Wideband Demon Tuning

[enkeivette]

Hooked up the LM2 yesterday, drove the Vette around...

It's about 10:1 under light throttle acceleration, 12.5:1 under part throttle acceleration, and I tipped into the boost real quick and it hit 15:1 :suicide:

If you have any tuning tips feel free to shout them out, a Demon is similar to a Holley for reference, but otherwise I'll be keeping this thread as a log.

If it turns out that I need to upgrade the fuel system and this can't be fixed by carb tuning, the car might have to wait. Unless anyone knows a trick to up the output of a mechanical pump.

[BRIAN]

Take what I say with a grain of salt but isn't 10:1 hella rich for light throttle, It gets leaner as you accelerate but I don't know. I'm used to seeing 10:1 at full throttle but in a boosted car and about 14.7:1 at cruise. This is going to bother me all day :bang:

[Vettezuki]

Hooked up the LM2 yesterday, drove the Vette around...

It's about 10:1 under light throttle acceleration, 12.5:1 under part throttle acceleration, and I tipped into the boost real quick and it hit 15:1 :suicide:

If you have any tuning tips feel free to shout them out, a Demon is similar to a Holley for reference, but otherwise I'll be keeping this thread as a log.

If it turns out that I need to upgrade the fuel system and this can't be fixed by carb tuning, the car might have to wait. Unless anyone knows a trick to up the output of a mechanical pump.

I'm shooting from the hip here, but if a mechanical pump is driven off the accessory drive, is there any such thing as a smaller pulley to spin it faster therefore higher output across the rev band. :huh: This might be especially necessary if you're running an underdrive pulley I would think, since you'd just be bringing it back into its designed engine rev : fuel pump turns ratio.

How big is your Carb?

[94cobra69ss396]

What size jets do you have in the primaries and secondaries? When I tuned the Caprice on the chassis dyno I increased the secondaries jet size from 83 to 86 and it went from 15:1 to 14.5:1 and picked up almost 50rwhp. We ran out of time on the dyno but the following day we up'd them to 92 and it felt a lot stronger than it did with the 86.

You'll want to shoot for 14.7:1 at a cruise and 11.5:1 at full throttle. You need to decrease the size of the primaries to bring the cruise ratio up and increase the secondaries to bring the WOT ratio down. However, start with the secondaries first and get the WOT right then move on to fine tuning the cruise ratio.

If you want some help tuning it I'm available this Sunday.

[BRIAN]

ugh I'm too young for carbs :p

[Damian]

What size jets do you have in the primaries and secondaries? When I tuned the Caprice on the chassis dyno I increased the secondaries jet size from 83 to 86 and it went from 15:1 to 14.5:1 and picked up almost 50rwhp. We ran out of time on the dyno but the following day we up'd them to 92 and it felt a lot stronger than it did with the 86.

You'll want to shoot for 14.7:1 at a cruise and 11.5:1 at full throttle. You need to decrease the size of the primaries to bring the cruise ratio up and increase the secondaries to bring the WOT ratio down. However, start with the secondaries first and get the WOT right then move on to fine tuning the cruise ratio.

If you want some help tuning it I'm available this Sunday.


Perfect answer.

[enkeivette]

Take what I say with a grain of salt but isn't 10:1 hella rich for light throttle, It gets leaner as you accelerate but I don't know. I'm used to seeing 10:1 at full throttle but in a boosted car and about 14.7:1 at cruise. This is going to bother me all day :bang:

Yes. Tune was f'd in the A, which is why I blew a piston. Those were base line figures.


CobraSS, Secondary - 80 / Primary - 94

I think you're supposed to keep them within a difference of 10, but at this point I might tell that rule of thumb to suck it.

Today I replaced the stock (33?) high speed air bleeds with some 28s, huuuge difference. Check out the graph, close to 12:1 under boost (only opened it up to about 5 lbs to be safe).
http://i26.tinypic.com/2rh8sx0.jpg
The rpm is not accurate (black line) but at least you can tell when I opened it up.


Tomorrow I plan to drop the primaries, prob down in the 76 range.

[enkeivette]

You can see the AFR (pink) jumps up when I open it up, and when I let off. I think (let me know if you guys disagree) that it's normal to hit 16 or so for a split second when you let off the throttle. I know it shouldn't go so lean when I first open the throttle, but I've been working on that problem for years. Next step is a 50cc pump because my system right now has the biggest pump cam with size 40 squirters and hollow screws. Not much more I can do without bigger pumps.

But the important thing is that it's back down within an acceptable range under boost, for the most part.

[94cobra69ss396]

Yes. Tune was f'd in the A, which is why I blew a piston. Those were base line figures.


CobraSS, Secondary - 80 / Primary - 94

I think you're supposed to keep them within a difference of 10, but at this point I might tell that rule of thumb to suck it.

Today I replaced the stock (33?) high speed air bleeds with some 28s, huuuge difference. Check out the graph, close to 12:1 under boost (only opened it up to about 5 lbs to be safe).
The rpm is not accurate (black line) but at least you can tell when I opened it up.


Tomorrow I plan to drop the primaries, prob down in the 76 range.

The secondaries should have the larger jets, not the primaries. I hope you have those labeled wrong in your post. If you do have larger jets in the primaries that would explain why your cruise ratio is so rich and you should switch them.

For the lean tip in, that's normal. As long as it isn't lean misfiring your fine. Back when I had the 396 in the Chevelle I had to make my own cam to fine tune the tip in. I just used my Dremal and shaped it until I had the results I wanted.

[enkeivette]

Yeah, switched em. Good catch.

[big2bird]

......... However, start with the secondaries first and get the WOT right then move on to fine tuning the cruise ratio.



That doesn't make any sense to me.

Adam, look for an e-mail from me.

[Vettezuki]

That doesn't make any sense to me.

Adam, look for an e-mail from me.

Unless it's an ode to Adam's biceps, post it here so I can learn something. As for not understanding, the apparent contradictions will get hashed out.

[94cobra69ss396]

That doesn't make any sense to me.

Adam, look for an e-mail from me.

He had a 15:1 AFR at wide open throttle and 10:1 at cruise. He needs to lean out the primaries more to fix the cruise ratio which will make the WOT ratio even leaner. I didn't want him to blow his newly repaired engine. Once he has the WOT ratio to where he wants it it is easy to go back and fine tune the primaries for a good cruise ratio and then readjust the secondaries for a safe WOT ratio again.

[Vettezuki]

He had a 15:1 AFR at wide open throttle and 10:1 at cruise. He needs to lean out the primaries more to fix the cruise ratio which will make the WOT ratio even leaner. I didn't want him to blow his newly repaired engine. Once he has the WOT ratio to where he wants it it is easy to go back and fine tune the primaries for a good cruise ratio and then readjust the secondaries for a safe WOT ratio again.

Keep in mind I know only the basic ideas of a carb. I've never worked with one.

So if I understand correctly the principle at work in this context is simply to be safe at WOT and work your way down to cruise.

BASIS
- There are two sets of "jets" which provide fuel to mix with air to the intake
- They are primaries (for idle and low throttle) and secondaries (opening up towards WOT), which are combined with the primaries

ADAM'S CASE
- He is very rich at idle BUT dangerously lean at WOT.

TUNING SCENARIOS - RON'S POINT (as I understand it)
By enlarging the secondaries first to bring WOT into safe AFR you create a margin of safety. If you reduce the size of the primaries first, even a test towards WOT run could be seriously damaging to the engine.


TUNING SCENARIO - BIRD'S POINT (as I'm totally speculating)
While fine tuning might be subtle, this isn't magic. The observed data that he is rich at idle/low throttle and dangerously lean at WOT suggests smaller jets in the primaries and larger jets in the secondaries. One should be able to make a pretty educated guess based on flow rates of the jets. Then proceed from idle up to WOT progressively in passes. This seems rational to me and I think is what bird might be suggesting.

MY QUESTIONS
If the starting spread in sizes between primaries and secondaries radically differs from experience and theory, it seems to me some other parameter in the "system" is off? :huh:

Even if you dial this in for 5lbs boost, aren't you going to completely repeat when you change up to 15lbs (or whatever you're at)? Therefore, if there is a safe progressive method, wouldn't you want to base it on your target max boost?

[94cobra69ss396]

So if I understand correctly the principle at work in this context is simply to be safe at WOT and work your way down to cruise?

That's how I do it.

[Vettezuki]

This isn't a carb thing. Adam, if you've been blasting around much with a bad tune that varies from super rich and especially to dangerously lean for any extended period of time, you may have seriously compromised your O2 sensor. This is really possible if you've ever had serious detonation or back-firing. Further tuning may be in the dark.

[Vettezuki]

That's how I do it.

Makes sense. The only caveat as I can imagine is that if you dial in a great AFR for WOT and you're rich at idle, then reduce your primaries, you're going to be lean at WOT and the cycle continues. I understand, in purely conceptual terms, the idea of calculating a starting point, and very progressively running up through throttle positions off idle.

[94cobra69ss396]

Makes sense. The only caveat as I can imagine is that if you dial in a great AFR for WOT and you're rich at idle, then reduce your primaries, you're going to be lean at WOT and the cycle continues. I understand, in purely conceptual terms, the idea of calculating a starting point, and very progressively running up through throttle positions off idle.

The ratio at idle is adjusted differently than the cruise ratio. He will adjust the idle mixture with the idle mixture screws. As for the primaries they have an affect on both cruise and WOT. The only reason I suggested that he adjust the WOT first is because he already broke one piston from it. No need to do it again. I'm not a carb expert and can only tell you from adjusting my own carb on the Chevelle. I've never tuned a my carb using an A/F meter but I did have the Chevelle dyno tested once after I built the 454 just to make sure I was close and the AFR was 12.6-12.8 from 3000 to 6500. This was after tuning it at the track and cruising it around town to fine tune the drivability.

[enkeivette]

ADAM'S CASE
- He is very rich at idle BUT dangerously lean at WOT.

No. Did you only read my first post? As of today I'm at 12:1 under boost. See graph. Assuming I don't run out of fuel it should stay around 12:1 at 10 lbs, carb meters air to fuel. Once you get the AFR right a good carb should keep it steady, at least at that throttle position.

The primaries are supposed to be about 10 sizes lower than the secondaries, because the PV on the primary side compensates about that much. With no PV, you should run equal size jets.

Going to screw with the PCVRs to get the boosted AFR a lil richer, then I'll tune down the primaries, and depending on the response I get after f'n with my PCVRs I might even jet down the secondaries.



As far as the O2 sensor, I just installed it the other day. It's brand new, and per mfr spec, I will only leave it in when tuning.

[Vettezuki]

No. Did you only read my first post? [B]As of today I'm at 12:1 under boost.

Yes. I read your first post.

It's about 10:1 under light throttle acceleration, 12.5:1 under part throttle acceleration, and I tipped into the boost real quick and it hit 15:1

Did I misunderstand it in principle? Light Throttle = rich, Heavy Throttle = Lean

It's a spectrum of rich -> lean according to throttle position???

The primaries are supposed to be about 10 sizes lower than the secondaries, because the PV on the primary side compensates about that much. With no PV, you should run equal size jets.

Define PV.

Going to screw with the PCVRs

Define PCVR.


As far as the O2 sensor, I just installed it the other day. It's brand new, and per mfr spec, I will only leave it in when tuning.

It only takes ONE lean backfire to destroy an O2's ability to accurately represent the amount of oxygen flowing by. To my understanding.

[enkeivette]

Did I misunderstand it in principle? Light Throttle = rich, Heavy Throttle = Lean

It's a spectrum of rich -> lean according to throttle position???



Define PV.



Define PCVR.




It only takes ONE lean backfire to destroy an O2's ability to accurately represent the amount of oxygen flowing by. To my understanding.

It was lean, now it's not lean under boost, and hopefully not under WOT. Still rich at part throttle.

Power Valve

Power valve channel restriction

Haven't had any lean backfires, and I doubt it. Further, I can recalibrate my 02 sensor whenever I want to, cuz that's how I roll playa. ;)

[Vettezuki]

. . . Further, I can recalibrate my 02 sensor whenever I want to, cuz that's how I roll playa. ;)

Hey playa, wouldn't you need some kind of standard to "recalibrate" to? How does that work?

I'm glad you're learning all this stuff on your car. Should make tuning RX-Snake go pretty smoothly. Bird has some kind of fantastical Sun machine for dialing in ignition curves on Dizzies and doing other diagnostic work. I only vaguely get it, but it's cool looking. Looks like a "computer" from a 60s war movie. :smack:

[big2bird]

I didn't mean to be rude, I just went to bed early. I can't stay up till 3AM anymore. Those days are gone.

I sent Adam a tuning paper for holleys by Dr. Lars Grimsrud.

Lars taught carb operation at GM for many years, and races on weekends.

The paper is very extensive, and too large to reproduce here. There are many checks to perform BEFORE even tuning, and there is a certain order of things to prevent chasing your tail.

[big2bird]

He had a 15:1 AFR at wide open throttle and 10:1 at cruise. He needs to lean out the primaries more to fix the cruise ratio which will make the WOT ratio even leaner. I didn't want him to blow his newly repaired engine. Once he has the WOT ratio to where he wants it it is easy to go back and fine tune the primaries for a good cruise ratio and then readjust the secondaries for a safe WOT ratio again.

I do understand the logic here. I just don't think I would approach it that way. If he goes back to square one, he can work up to WOT, and avoid WOT while tuning.;)

[Vettezuki]

Makes sense to me. :thumbs_up:

Send me the paper too yo. Any paper written by a guy named Dr. Lars has got to be good. :smack:

[enkeivette]

Ben, base line reading should be 20.9 (known atmospheric level). If it deviates more than .4 the LM2 will calibrate to correct it.

Bird, thanks for the e-mail, I'll attach it here for others. At the risk of sounding arrogant, I'm sort of beyond his general tuning guidelines. I've definitely used them to get my car a good base line tune, but his paper doesn't dive into air bleeds, & pcvrs. And Demons are notorious for going lean at WOT, you can up the jet size as much as you want and it will still be lean at WOT.

Also, I used his timing procedure to set up my NA setup, but now that I have to limit my total timing to 28 because of the blower I can't setup the butterflys over the trasfer slots the way that they should be.

[big2bird]

Then, I suggest you start a thread at VM where he can respond, or e-mail him directly. I also have his phone # should you wish to call him. I am sure he will help you, or at most tell you to trash the Demon, and try something else.:rolling:

[94cobra69ss396]

Also, I used his timing procedure to set up my NA setup, but now that I have to limit my total timing to 28 because of the blower I can't setup the butterflys over the trasfer slots the way that they should be.

Does your Demon have the Idle-Eze? If so you need to adjust it so that you can close the butterflys where they need to be.

[enkeivette]

Idle Eze is adjusted, won't help me now. Car needs to be limited to 28 total, wants 18 initial to idle adequately with the transfer slots set correctly, cannot find a 10 degree bushing, otherwise I would.

I know what I need to do, smaller primaries for cruise, drill the PVCRs between 70 and 80 for a baseline.

Might need to drill out the PV protection to prevent it from kicking on under boost, need to call Demon and find out if this is a potential problem.

[big2bird]

Idle Eze is adjusted, won't help me now. Car needs to be limited to 28 total, wants 18 initial to idle adequately with the transfer slots set correctly, cannot find a 10 degree bushing, otherwise I would.


What kind of dizzy?

[big2bird]

Good read.

http://www.superchevy.com/technical/engines_drivetrain/induction_poweradders/sucp_0809_chevy_carburetor_build/index.html

[Damian]

Im still trying to understand why you would tune WOT first and not cruising? Your primaries affect WOT too. Personally, Id do cruising first, then ease into WOT.

[94cobra69ss396]

Tune how you want. Again, I'm not an expert and haven't written any articles on tuning carbs. I'm just your average guy who has learned to tune his own carb on his own car. I've already explained why I suggested it.

[Damian]

Tune how you want. Again, I'm not an expert and haven't written any articles on tuning carbs. I'm just your average guy who has learned to tune his own carb on his own car. I've already explained why I suggested it.

If it works, it works. I havent touched a carb in quite a few years, so Im no expert either. I just know when I tune an EFI engine, Im going to tune idle and cruising speed areas first, then venture up and get to WOT. To me, thats much safer. My thinking is that if you cant drive 25 mph safely, how can you do WOT going 80?? Thats how I look at it. If you can tune a carb that way, then I learned something new.

[94cobra69ss396]

If it works, it works. I havent touched a carb in quite a few years, so Im no expert either. I just know when I tune an EFI engine, Im going to tune idle and cruising speed areas first, then venture up and get to WOT. To me, thats much safer. My thinking is that if you cant drive 25 mph safely, how can you do WOT going 80?? Thats how I look at it. If you can tune a carb that way, then I learned something new.

So after reading his first post in which he says "It's about 10:1 under light throttle acceleration, 12.5:1 under part throttle acceleration, and I tipped into the boost real quick and it hit 15:1" you would worry more about getting the cruise ratio right first? Even after you broke a piston due to the WOT being too lean? According to your statement above you consider 15:1 under boost safer than 10:1 at cruise and would lean out the primaries further to get to 14.7:1 at a cruise and then worry about the ratio under boost. I'd be more concerned with breaking another piston than drivability and it looks like Adam felt the same because he corrected the ratio on the secondary side and it's now around 12:1 under boost.

[Vettezuki]

So after reading his first post in which he says "It's about 10:1 under light throttle acceleration, 12.5:1 under part throttle acceleration, and I tipped into the boost real quick and it hit 15:1" you would worry more about getting the cruise ratio right first? Even after you broke a piston due to the WOT being too lean? According to your statement above you consider 15:1 under boost safer than 10:1 at cruise and would lean out the primaries further to get to 14.7:1 at a cruise and then worry about the ratio under boost. I'd be more concerned with breaking another piston than drivability and it looks like Adam felt the same because he corrected the ratio on the secondary side and it's now around 12:1 under boost.

I understand your point. but one thing I'm sticking on a little bit, is that you don't have to romp on it right away for tuning. If you get the cruise right, then you go a little further and observe; in short you don't ever make WOT passes in the dark. You get cruise right then pass by pass work up through throttle positions.

To be honest I like your thinking in principle because it is fail safe. No moment of jack assery or simply loosing concentration will result in destruction. :drink:

[94cobra69ss396]

I understand your point. but one thing I'm sticking on a little bit, is that you don't have to romp on it right away for tuning. If you get the cruise right, then you go a little further and observe; in short you don't ever make WOT passes in the dark. You get cruise right then pass by pass work up through throttle positions.

To be honest I like your thinking in principle because it is fail safe. No moment of jack assery or simply loosing concentration will result in destruction. :drink:

How long has he been driving it like this, a year? You really think he's not going to jump on it if someone revs at him? Do you really think Adam has that much restraint?

I'm not saying that you shouldn't tune the primaries first but that should have been done after he built the engine the first time and was breaking it in. That's how I tuned the 454 in the Chevelle. I drove it around at light throttle and got the drivability tuned for the first 500 miles or so and then tuned the secondaries for WOT.

Anyone else with their vast knowledge want to tell me how my suggestion is wrong?

[94cobra69ss396]

Adam, did you do any more tuning today? How's the ratio now?

[Vettezuki]

. . You really think he's not going to jump on it if someone revs at him? Do you really think Adam has that much restraint?

This Adam?

http://photos-a.ak.fbcdn.net/photos-ak-snc1/v2564/39/119/19912599/n19912599_32644552_1400909.jpg

Ya. No.

I'm not saying that you shouldn't tune the primaries first but that should have been done after he built the engine the first time and was breaking it in. That's how I tuned the 454 in the Chevelle. I drove it around at light throttle and got the drivability tuned for the first 500 miles or so and then tuned the secondaries for WOT.

So we're talking about an Adam-safe procedure.

Anyone else with their vast knowledge want to tell me how my suggestion is wrong?

It clearly isn't wrong. It's probably best for Adam's exact condition. It simply differs from the ideal procedure (basically the one you used for yourself).

That's my read.

[94cobra69ss396]

Yes, this was specifically for Adam who is the one tuning his car and asked. Now if he had posted that he just built an engine and wanted to know how he should go about tuning the carb my answer would have been different.

[Vettezuki]

Yes, this was specifically for Adam who is the one tuning his car and asked. Now if he had posted that he just built an engine and wanted to know how he should go about tuning the carb my answer would have been different.

Alles Klar!

[enkeivette]

Damian, Zuki, you guys are arguing for an impossible method of tuning. You can't tune your cruise AFR without affecting your WOT AFR. You can tune your WOT AFR without affecting your cruise AFR, however.

And you can't just hit one then the other, ex: next time I get in there I will lean out the primary side which will drop the cruise AFR & the WOT AFR. Then, depending on how much it leaned out, I will need to guage the size I need to drill the PVCR out to, depending on that.

Stop thinking about it in terms of RPM vs AFR and think about it in terms of tuning this part of the carb first, then that part, then the other part, in that order.

And Adam did tune his carb when he first built the motor, then he changed the intake manifold, compression, cam lift did some port matching and added a blower.


Bird, MSD HEI.


CobraSS, I'm starting to wonder if my PV's blow out protection is working under boost and stopping the PV from functioning. I want to call BG Mon and get their opinion, might drill it out.

[Vettezuki]

Damian, Zuki, you guys are arguing for an impossible method of tuning.

Que? It's basically the method bird was talking about in the first place and what Ron would have recommended in principle.

Yes, this was specifically for Adam who is the one tuning his car and asked. Now if he had posted that he just built an engine and wanted to know how he should go about tuning the carb my answer would have been different.

. . . I'm not saying that you shouldn't tune the primaries first. . . That's how I tuned the 454 in the Chevelle. I drove it around at light throttle and got the drivability tuned for the first 500 miles or so and then tuned the secondaries for WOT.

. . . You can't tune your cruise AFR without affecting your WOT AFR. You can tune your WOT AFR without affecting your cruise AFR, however.

Sure. Then go back and discover you need to reduce the size of your primaries for cruise and what happens to your WOT AFR?? Seems like a lot of inefficient tail chasing.

And you can't just hit one then the other, ex: next time I get in there I will lean out the primary side which will drop the cruise AFR & the WOT AFR. Then, depending on how much it leaned out, I will need to guage the size I need to drill the PVCR out to, depending on that.

I don't know much about carbs in practice. But it's hard for me to believe it involves this much black magic. If it does, no wonder FI and computerized control took over.

Stop thinking about it in terms of RPM vs AFR and think about it in terms of tuning this part of the carb first, then that part, then the other part, in that order.

What system is "this and that part" connected to? It isn't a carb in a "vaccuum"; it's part of an engine system functioning in a context. All references are made relative to throttle position which has at least something to do with rpm. Yes I know there is a lot more to do to this regarding engine load and vacuum, maybe I should only refer to throttle position and load. The idea is simply moving in a progressive manor bottom to top. Repeated cycles may be required to idealize all ranges for a given purpose, but the process must be systematic and logical.

I'll be investigating TB injection for RX-Snake. No Fing way I want to deal with these kind of issues at all.

[big2bird]

Ben,
There is a big difference between his induction system and the Snake. He pressurizes his carb. The Snake sucks. Big diff. Tuning a Holly, once finished, will hold it's tune well.
A carb is just a mechanical metering device that regulates the A/F mixture thru various air flows. Typically, on a N/A engine, once tuned, you can install it on another engine, and it will work fine.
Adam is pushing air into a carb that for 100 years has relied on differential pressure to operate properly.(Vaccum).

[big2bird]

Bird, MSD HEI.



Pull it out, and I'll install a 10* stop.

[Damian]

Damian, Zuki, you guys are arguing for an impossible method of tuning. You can't tune your cruise AFR without affecting your WOT AFR. You can tune your WOT AFR without affecting your cruise AFR, however.

Then I have to appologize then, my statements werent meant to argue, more of me wanting to understand why he chose that route to tune. The reason I was asking is because Im working on a guys Eclipse that turboed it. The shop that fabricated everything said the fuel system was a-ok for the setup, not even close. So Im going in and upgrading the fuel pump, fuel rail and injectors, among a full maintenence on the engine. Then Im going to tune for his bigger injectors. Then Ill tune his car for cruising and light boost, just enough to get him to a dyno shop of his choice to really dial in hit WOT a/f ratios. So thats how I do it, not saying its the only way, but my way.

I do see your reasoning now for the fail safe under WOT conditions. That is smart and thats exactly how Im going to tune this guys car, minus the WOT pull. But its a matter of finding a balance between the primaries and secondaries, and from the sounds of it, is going to take a lot of trial and error. Tuning EFI under boost is so much easier IMO.

[enkeivette]

I don't know much about carbs in practice.

This is apparent.

I posted a thread awhile back with some Holley tuning basics. Review it. http://www.motorgen.com/forum/showthread.php?t=284

After all of that you move on to the jets. Not cruise AFR, not WOT AFR... the jets. Hopefully, after tuning the jets (both primary AND secondary at the same time, as they need to be 8-10 off) the idle, cruise, and WOT AFR will all work out perfectly.

...IF NOT! Then you can move on to f*cking with HSABs IABs and drilling out different parts of the metering block (PVCRs). You cannot, CANNOT, screw with all of that more sensitive stuff before you at least try to tune by jets (which is not cruise or WOT specific) otherwise you might (and will likely) cause irreversible damage to your carb. And THAT, is chasing your tail.

Like I said before, you move through the carb systematically, not RPM vs AFR.

As far as it being more difficult, cry about it. I've spent about 10 mins working on the carb since I hooked up the LM2, and after a few more quick changes it will be spot on. The rest of the time I've spent typing on this forum and waiting for it to be Monday so I can call Barry Grant about the PV check ball.



Pull it out, and I'll install a 10* stop.

Bird, you are my hero. When can I bring it over? And how much are custom Bird bushings? :D

[big2bird]

Bird, you are my hero. When can I bring it over? And how much are custom Bird bushings? :D

Cheap. No one makes a 10* bushing. I am going to put a stop on the slot.
(Read as shorten the slot). Not to worry. It's reversable.;)

I think Weds might be good.

[BRUTAL64]

I don't post on the week ends. So you guys have all your fun and I'm not around. I see how it is.:(

[Vettezuki]

I don't post on the week ends. So you guys have all your fun and I'm not around. I see how it is.:(

We're going to have to hold a bake sale or something to get you a computer for the shop. :)

[BRUTAL64]

We're going to have to hold a bake sale or something to get you a computer for the shop. :)

Wow, what a nice thought.:bigthumbsup:

[big2bird]

More stuff

http://www.chevyhiperformance.com/tech/engines_drivetrain/induction_poweradders/0610ch_superchargers/compression_ratio.html

[big2bird]

http://www.pawinc.com/charts/Supercharged_Compression.html

[enkeivette]

Guess my jets outflowed my metering blocks. As you can see, there is almost no change.

Before (80s/94s)
http://i26.tinypic.com/2rh8sx0.jpg

After (75s/88s)
http://i28.tinypic.com/2ujtt9x.jpg

[94cobra69ss396]

After (75s/88s)
http://i28.tinypic.com/2ujtt9x.jpg

Correct me if I'm wrong reading this graph because it's a little hard to read.

The bottom numbers are time lapsed and the side numbers from left to right are Volts, RPM and A/F ratio? According to the 2nd graph you ran your engine up to 8500rpms? The pull starts at 10 seconds where the ratio is 11.25. It then spikes to about 12.5, falls to almost 10, spikes again to about 13.75, falls to around 12.25 until about 13.5 seconds when you let off where it then spikes back up to about 15. Was this pull made under a load?

[enkeivette]

That 13.5 lean spike was because I pumped the throttle to readjust my foot. Wasn't WOT with either of those pulls, part throttle, prob 5lbs and about 4.5-5K rpm. I'm taking it easy because I'm making changes and I don't know what's going on till I get home. Don't want to pop another piston.

RPM is not accurate, only an indication that I was getting on it.

The spike at the end of the pull is normal, motor goes lean when the throttle slams closed all of a sudden. This is why your exhaust pops.

[big2bird]

The spike at the end of the pull is normal, motor goes lean when the throttle slams closed all of a sudden. This is why your exhaust pops.

Actually, when you close the throttle, the mixture spikes rich. The popping sound is the mixture hitting the exhaust manifold. That is why diverter valves shut off during high vaccum readings.
Turn off your key at high rpms while coasting, then turn back on after a few seconds. It will ignite this unburned fuel, and blow your muffler clean off.:laugh:

[BRUTAL64]

Turn off your key at high rpms while coasting, then turn back on after a few seconds. It will ignite this unburned fuel, and blow your muffler clean off.:laugh:


Done that a few times.:sm_laughing:

[big2bird]

Pull it out, and I'll install a 10* stop.

Adam. Do you want me to do this the way we discussed, or would you like me to have a custom made 10* bushing made? It would take me more time to arrange that, and might be $20 instead of $10, but would be easier to reverse. Let me know.

[enkeivette]

Sent you a PM, yeah do the 10 bushing if you can. I can wait. :drink:

Update, I have a blue pump cam in the mail. Trying to see if I can fix the lean spit without going bigger on the jet size. Trying to keep my mpg above 7.

[big2bird]

Sent you a PM, yeah do the 10 bushing if you can. I can wait. :drink:

:hail::hail::hail::hail:

[enkeivette]

:hail::hail::hail::hail:

Why would the dist. guru bow to me?! I bow to you!

[big2bird]

Why would the dist. guru bow to me?! I bow to you!

Because your wish is my command. Besides, your car beats my car.
Now, for an update, Lars recommends using a boost retard to pull the timing back to 24* under boost.

I am going to have a 8*, 10*, and 12* bushing made.

See also additional info at VM .;)

[enkeivette]

Lars has more money than me. After buying that new ring set and the new piston, I'm tapped out. No new toys till I get out of school. An intercooler would be a much better fix, and when cash permits I will cool my big blow dryer.

Bird, you are my hero.

[BRUTAL64]

Lars has more money than me. After buying that new ring set and the new piston, I'm tapped out. No new toys till I get out of school. An intercooler would be a much better fix, and when cash permits I will cool my big blow dryer.

Bird, you are my hero.

Bird, is everybody's HERO.:drink:

[enkeivette]

Made my first WOT pass... where oh where did my horsepower go, oh where oh where did it go? I think it left with my 34 degrees of timing. Don't think I can live with 24, I need to install the 10 degree bushing for 28 total and take someone with a ping sensitive ear on a ride with me.

Found a cheap way to tune my cruise, bought a .073/ .076/ .078 drill bit and I drilled my left over .028 air bleeds out to .073 (stock is .07) my cruise is better, around 14.2:1 but my idle has a difficult time staying stable. I think I need to take the bleeds up to .076 at least, then open up the idle mixture screws. I think it will idle happy that way.

At WOT it seemed to jump up to 14:1 again, which is odd, it moves so fast it's hard to tell what's noise and what's a legit reading. I need to sample only the WOT period so I can get a wider sample.

I want to install the 75 primary jets but I'm worried my part throttle acceleration will get too fat, it's already about 13:1. But hopefully the larger IABs will somewhat counteract the problem.

I'll report back tonight.

[enkeivette]

Combo 75/84 jets drilled the IABs out to .076 and the cruise is about the same after turning the idle mixture screws out a tad to bring the idle back to stoich. WOT is about 13:1 now. Going to jet up the secondary side to 86.

The idle still gets somewhat angry. I'm going to go ahead and drill the bleeds out to .078 and retune, I can see the light. :nuts:

[Vettezuki]

Combo 75/84 jets drilled the IABs out to .076 and the cruise is about the same after turning the idle mixture screws out a tad to bring the idle back to stoich. WOT is about 13:1 now. Going to jet up the secondary side to 86.

The idle still gets somewhat angry. I'm going to go ahead and drill the bleeds out to .078 and retune, I can see the light. :nuts:


When you're done with this whole thing and have what you want write down what you would recommend as a comprehensive procedure starting from scratch; IR Curious.

[enkeivette]

When you're done with this whole thing and have what you want write down what you would recommend as a comprehensive procedure starting from scratch; IR Curious.

If I had to do this all over again I could do it in a weekend or two, even on a different motor. I now have an understanding of all of the adjustments and how they overlap.

BTW, Lars mentioned that jets and HSABs do not affect cruise and idle AFR, but what he forgot to mention was that they do affect part throttle acceleration (which is what you're doing 50% of the time). So they do overlap.

Most carb tuners out there would be happy with a 12-14:1 AFR everywhere. I'm being ridiculously picky trying to get a 14.7 cruise/ idle, a 13:1 part throttle AFR and a 12:1 WOT at all rpm. Like I said, I could have left my jet combo alone weeks ago and the motor would have run well but at 7 mpg. I'm hoping for 25 on the highway and 17ish in the city.

The folks on Vettemod seem to be mad at me because I talked back to Lars. :surrender: They seem to be mad that I made a giant leap rather than tuning slowly and gradually. The reality is that I made the leap after careful research and I was dead on with my guess on the HSABs. My WOT AFR curve did not get messed up with the smaller bleeds and I'm a few jet sizes away from a perfect 12:1. Lars argued that he has never seen a carb that needed such a drastic change in HSAB size, but I have. 3 or 4 people with Demons on the Innovate forum. Sure I could buy several tuning kits for a couple hundred bucks and go back and do it 'the right way' but the reality is that AFR is AFR, and my fuel curve is looking good. So I don't care what anyone says, my tire smoke and good gas mileage speaks for itself.

I'll get started on that thread Ben. Feel free to help out CobraSS.

[94cobra69ss396]

Don't worry what other people say. You did it yourself and look how much you learned and how close you are to the AFR you set out to get. I've done a ton of tuning on my Chevelle and I couldn't tell you what the AFR is at cruise. I don't have the slightest idea. All I know is that at WOT it's where I want it and that's just because I ran it on a dyno. Hell, you know more about tuning the carb than I do now. :hail:

[Vettezuki]

If I had to do this all over again I could do it in a weekend or two, even on a different motor. I now have an understanding of all of the adjustments and how they overlap.

BTW, Lars mentioned that jets and HSABs do not affect cruise and idle AFR, but what he forgot to mention was that they do affect part throttle acceleration (which is what you're doing 50% of the time). So they do overlap.

Most carb tuners out there would be happy with a 12-14:1 AFR everywhere. I'm being ridiculously picky trying to get a 14.7 cruise/ idle, a 13:1 part throttle AFR and a 12:1 WOT at all rpm. Like I said, I could have left my jet combo alone weeks ago and the motor would have run well but at 7 mpg. I'm hoping for 25 on the highway and 17ish in the city.

The folks on Vettemod seem to be mad at me because I talked back to Lars. :surrender: They seem to be mad that I made a giant leap rather than tuning slowly and gradually. The reality is that I made the leap after careful research and I was dead on with my guess on the HSABs. My WOT AFR curve did not get messed up with the smaller bleeds and I'm a few jet sizes away from a perfect 12:1. Lars argued that he has never seen a carb that needed such a drastic change in HSAB size, but I have. 3 or 4 people with Demons on the Innovate forum. Sure I could buy several tuning kits for a couple hundred bucks and go back and do it 'the right way' but the reality is that AFR is AFR, and my fuel curve is looking good. So I don't care what anyone says, my tire smoke and good gas mileage speaks for itself.

I'll get started on that thread Ben. Feel free to help out CobraSS.


My assumption is that it's not magic. Through your experience you must be able to derive a documentable "from scratch" optimal process; this is my interest. Be sure to include any points that you would do differently if money were no object (reasonably, you know what I mean :)).

You guys will get to tune our carb in concert with bird setting up the dizzy for the project car, a pull through blower setup. I'll setup a dyno day and we'll do it in a day, so you'll need to specifiy ALL the things you'd like to have on hand at that time (long from now). Do you have any reservations about it being a vacuum secondary?

[enkeivette]

My assumption is that it's not magic. Through your experience you must be able to derive a documentable "from scratch" optimal process; this is my interest. Be sure to include any points that you would do differently if money were no object (reasonably, you know what I mean :)).

You guys will get to tune our carb in concert with bird setting up the dizzy for the project car, a pull through blower setup. I'll setup a dyno day and we'll do it in a day, so you'll need to specifiy ALL the things you'd like to have on hand at that time (long from now). Do you have any reservations about it being a vacuum secondary?

Yes, vacuum secondaries are stupid. Go mechanical.

Also, if you don't care about the idle/ cruise AFR on the Snake, we can set it up in prob a day. And we'll know exactly what the AFR is before we send it to the dyno.

[big2bird]

Generally speaking, on a N/A engine, mech secondaries for a stick, and vacuum secondaries for a slushbox.

[BRUTAL64]

Generally speaking, on a N/A engine, mech secondaries for a stick, and vacuum secondaries for a slushbox.

:drink: good point.

Hey, got a voice mail from you, but it's mostly static.:(

[BADDASSC6]

That doesn't make any sense to me.

Adam, look for an e-mail from me.

Every time I have help tune a car. The first step was to get hte car drivable so it could be run with a limited degree of safety on the Dyno. The the WOT was dialed in on the Dyno. Then the part throttle maps were adjusted to increase drivability.

[BADDASSC6]

My assumption is that it's not magic. Through your experience you must be able to derive a documentable "from scratch" optimal process; this is my interest. Be sure to include any points that you would do differently if money were no object (reasonably, you know what I mean :)).

You guys will get to tune our carb in concert with bird setting up the dizzy for the project car, a pull through blower setup. I'll setup a dyno day and we'll do it in a day, so you'll need to specifiy ALL the things you'd like to have on hand at that time (long from now). Do you have any reservations about it being a vacuum secondary?

Here is my Carb tuning input:
Step 1) unbolt carb
Step 2) Have intake manifold drilled for fuel injectors and milled for throttle body
Step 3) connect laptop and start typing:thumbs_up:

[Vettezuki]

Here is my Carb tuning input:
Step 1) unbolt carb
Step 2) Have intake manifold drilled for fuel injectors and milled for throttle body
Step 3) connect laptop and start typing:thumbs_up:

That's the first damn thing I've truly understood. :smack:

[enkeivette]

I'd like to see FI & an FI Procharger kit on my motor for the same price as my Demon and my Procharger.

[Vettezuki]

I'd like to see FI & an FI Procharger kit on my motor for the same price as my Demon and my Procharger.

I'm not concerned with such pedestrian issues. ;)

Out of curiosity what's the price differential between your carbed setup and big_G's FI?

[enkeivette]

Big G runs a Holley last time I checked.

[Vettezuki]

Big G runs a Holley last time I checked.

I think he's running a FAST setup.

http://motorgen.com/forum/showthread.php?p=22525#post22525

[enkeivette]

Installed 78s/88s and drilled my IABs out to 78, HSABs are still 28.

Cruise right around 13.5 (Needs some work and research. I think it will come down to a balance between the IFRs and the IABs and the idle mixture screws.)
WOT right around 11.8:1 YEAAAAAAAAAHHH!!!
Idle right around 14.8:1

Suck on that suckas!

[94cobra69ss396]

Installed 78s/88s and drilled my IABs out to 78, HSABs are still 28.

Cruise right around 13.5 (Needs some work and research. I think it will come down to a balance between the IFRs and the IABs and the idle mixture screws.)
WOT right around 11.8:1 YEAAAAAAAAAHHH!!!
Idle right around 14.8:1

Suck on that suckas!

This is perfect for right now but remember as soon as winter comes it's going change. Also, 11.8 at WOT is a little lean in the higher boost levels.

[Vettezuki]

Installed 78s/88s and drilled my IABs out to 78, HSABs are still 28.

Cruise right around 13.5 (Needs some work and research. I think it will come down to a balance between the IFRs and the IABs and the idle mixture screws.)
WOT right around 11.8:1 YEAAAAAAAAAHHH!!!
Idle right around 14.8:1

Suck on that suckas!

Congrats yo. Do you still find the WOT to be lacking because of the retarded timing? We can try a little Torco if you like, that stuff works and since you're only bombing around in the Vette, it wouldn't be a big expense.

[enkeivette]

11.8 is lean?! What would you shoot for?

I think the 24 degrees of timing is sort of ridiculous, & I don't like the idea of having to add something to my gas ever. I think part of the problem was the 15:1 AFR, I feel a little more confident about abusing the engine with a sub 12 AFR. And I think I'll prob bring the timing up to 28.

[94cobra69ss396]

11.8 is lean?! What would you shoot for?

I think the 24 degrees of timing is sort of ridiculous, & I don't like the idea of having to add something to my gas ever. I think part of the problem was the 15:1 AFR, I feel a little more confident about abusing the engine with a sub 12 AFR. And I think I'll prob bring the timing up to 28.

I have around 11.5 up until about 4800-5000rpms and then it drops to 10.5 to help keep it from detonating. You should be fine with 11.8 as long as it's not detonating.

[enkeivette]

I called BG tech again... because I like wasting my time apparently. It was actually entertaining to call them. I tell myself that I'm going to direct the conversation a certain way to pull a very specific answer out of them... and it never works.

Today I was trying to figure out how much of a jump I should make on the IFRs to lean out 1 AFR point, sounds doable right? Nope! He starts lecturing me on how I want to cruise at 12.8:1... :suicide: And how I should lean out my HSABs, that's right... high speed bleeds... to .043s!!! Remember, I had 33? HSABs which caused my piston to pop at 15:1 AFR and it took 28 HSABs to get my motor down to 12:1... now he wants me to install 43 HSABs!!!

Idiot!!! Why do I keep calling them?! How does that guy, Jeff, have a job there? How?! With this economy? I wouldn't trust him to change the oil on my Neon. He'd prob try to put some antifreeze in there to keep the motor running super cool!

[enkeivette]

Anyways, think I'll try some 29 IFRs to replace my 36s. The AFR will stay mid 13 in the city in 4th but it jumps to high 12s on the freeway in 6th.

Then my WOT is fat happy during the day, but leans up at night. Wish my Demon came with a computer. Haha.

[Damian]

Anyways, think I'll try some 29 IFRs to replace my 36s. The AFR will stay mid 13 in the city in 4th but it jumps to high 12s on the freeway in 6th.

Then my WOT is fat happy during the day, but leans up at night. Wish my Demon came with a computer. Haha.

Can you log knock?

[enkeivette]

Can you log knock?

Nope. I have a knocklite, but it doesn't work with my big cam... Need to ebay it.

[Damian]

Nope. I have a knocklite, but it doesn't work with my big cam... Need to ebay it.

Can you get one to work with your setup? When I datalog my Eclipse, thats one of the main things Im looking at when I make my timing adjustments.

[enkeivette]

Installed the 29 IFRs over the stock 36s. Cruise around town now is right around 14.6:1, idle is right around 14.8:1. Cruise on the highway has gone up to mid 13s from mid 12s. I'm not sure how I can lean out the highway cruise without leaning out the idle/ low speed cruise. I might just have to live with the mid 13s in 6th gear.

Drilled some main jets with a 7/64ths drill (close to 91 size) from the 88s that were installed and the AFR at WOT actually got a few tenths leaner. The hole is larger than the 88 hole but I must have not drilled it clean which prob causes it to flow less. I think I'll try 80s and 94s next time.

The smaller IFRs actually make up somewhat for the huge primary main jets at part throttle. Really made acceleration smoother and leaner.

Also, doing a high speed run my bowls ran out of fuel... I think my mech fuel pump might have to retire. I'm going to up the level on the floats for now for a cheap fix.

[BRUTAL64]

Installed the 29 IFRs over the stock 36s. Cruise around town now is right around 14.6:1, idle is right around 14.8:1. Cruise on the highway has gone up to mid 13s from mid 12s. I'm not sure how I can lean out the highway cruise without leaning out the idle/ low speed cruise. I might just have to live with the mid 13s in 6th gear.

Drilled some main jets with a 7/64ths drill (close to 91 size) from the 88s that were installed and the AFR at WOT actually got a few tenths leaner. The hole is larger than the 88 hole but I must have not drilled it clean which prob causes it to flow less. I think I'll try 80s and 94s next time.

The smaller IFRs actually make up somewhat for the huge primary main jets at part throttle. Really made acceleration smoother and leaner.

Also, doing a high speed run my bowls ran out of fuel... I think my mech fuel pump might have to retire. I'm going to up the level on the floats for now for a cheap fix.

When drilling jets bevel the top and bottom opening for cleaner flow.

[enkeivette]

I will, good idea.

[94cobra69ss396]

Also know that when you increase the level in the floats it tends to richen up the mixture slightly.

[enkeivette]

Also know that when you increase the level in the floats it tends to richen up the mixture slightly.

I did know that. Any idea how high I can bring the levels up before I f something up?

[94cobra69ss396]

I did know that. Any idea how high I can bring the levels up before I f something up?

Not sure what you mean.

[enkeivette]

There are 3 lines in the sight glass. Typically you're supposed the bring the fuel level to the middle line, I've heard of recommendations to take it to the top line, but never beyond that. I'm wondering how much fuel I can allow it to fill up without flooding some passage way in the metering block, etc.

[94cobra69ss396]

There are 3 lines in the sight glass. Typically you're supposed the bring the fuel level to the middle line, I've heard of recommendations to take it to the top line, but never beyond that. I'm wondering how much fuel I can allow it to fill up without flooding some passage way in the metering block, etc.

It could also slosh out the vent tube if it's too high. This is a common problem with Holleys on 4x4s.

[enkeivette]

It could also slosh out the vent tube if it's too high. This is a common problem with Holleys on 4x4s.

Firetastic.

[enkeivette]

Raised the float levels to the upper line... car bucks under moderate throttle now. :(

Time to move it back down and step up to a loud ass electric fuel pump. I guess when they dyno my car I'll ask them to run it in 3rd, just to be safe, if I don't have a new pump on by then.


I've decided to leave the PVCRs alone, don't want to risk screwing up the metering block/ tune. No time or money for that right now. I'll live with the 13.5 6th gear cruise.

[enkeivette]

Bucking was a result of an MSD wire melting on the header. Fixed it, but not before I moved the floats back down problem solving. :damit:

Still intend to go electric when I get the time to wrench on it again.

[big2bird]

It could also slosh out the vent tube if it's too high. This is a common problem with Holleys on 4x4s.

Install extensions.

[94cobra69ss396]

Install extensions.

Jet extensions won't help in the offroading example. When you are climbing a steep hill with light throttle you are only using the primaries which are getting fuel. What happens is that the angle is enough that when you hit bumps the fuel gets pushed out of the float bowl through the vent tube and it falls into the venturies which in turn floods the carb. If you where giving it full throttle in that situation then you would want to have jet extensions on the secondary jets.

[enkeivette]

Bowls are running out of fuel, I've had this problem before. Need an electric pump. Mechanical one was maxed out 200hp ago.