PV protection (check ball) has to be drilled out for boost?

[enkeivette]

Trying to figure out what my PV check ball is doing under boost, almost ready to forget about it and tune it as it. BG Tech sucks, those red necks rarely give me any useful advice. 90% of their techs are morons.

They don't want to answer your question, they think they know what your problem is before you even tell them what's up. This guy told me that my compression under boost is 15.29:1 and that I need to run 114 race gas or I'll pop another piston.

I popped a piston because BG doesn't know how to setup a race carb to get the AFR under 15:1 at WOT! That's why I popped a piston. :mad:

He told me that race gas would correct my rich problem at cruise and magically correct any lean problems at WOT. :rolleyes2:

[Vettezuki]

. . . He told me that race gas would correct my rich problem at cruise and magically correct any lean problems at WOT. :rolleyes2:

Wow. Even I know more than that. Hell, Sean might know more than that. That's scary. :smack:

[94cobra69ss396]

He is correct about the compression. Have you called The Carb Shop in Ontario? I'm not sure what effect boost has on a power valve.

[Vettezuki]

He is correct about the compression. Have you called The Carb Shop in Ontario? I'm not sure what effect boost has on a power valve.

I don't understand. Compression Ratio is a function of mechanical design and does not change. Cylinder pressures certainly raise under boost and I suppose that what you're referring to is a cyldiner pressure equivalency of a higher compression for comparison purposes? :huh:

Correct me if I'm wrong enkei, but your motor is 9:1 static and you're only running 5-6 pounds at the moment. I can't imagine that's anywhere near equivalent to 15.x:1.

[Vettezuki]

. . .

Correct me if I'm wrong enkei, but your motor is 9:1 static and you're only running 5-6 pounds at the moment. I can't imagine that's anywhere near equivalent to 15.x:1.

This is not an A/F item, so a little OT, but found a little formula.

Effective compression Ratio (ECR) = [(Boost / 14.7) +1] x CR

Ergo:
ECR = ((6 / 14.7) + 1) x CR

ECR = 12.67 (at sea level)

That does imply you're in quite a gray area with pump gas. Intercooling and boost timing retard change it quite a bit of course, but in simple terms it seems to me 6psi is about as much as you're going to get without some combination of race gas, intercooling, boost timing retard. :huh:

As for Race Gas changing fixing your A/F problem, unless I don't understand anything at all, that's funny.

[enkeivette]

I don't understand. Compression Ratio is a function of mechanical design and does not change. Cylinder pressures certainly raise under boost and I suppose that what you're referring to is a cyldiner pressure equivalency of a higher compression for comparison purposes? :huh:

Correct me if I'm wrong enkei, but your motor is 9:1 static and you're only running 5-6 pounds at the moment. I can't imagine that's anywhere near equivalent to 15.x:1.

10lbs since I fixed the HG & intake gasket after DC dyno day (5 lbs then). This is why I blew a piston and this is why my car is way faster now than it was then.

Doesn't matter. Procharger says that I can run 10lbs at 34 degrees of timing on 91 octane with Al heads. I'm convinced the cylinder destruction was due to a 15:1 AFR and that with a 12:1 AFR and only 28 degrees of timing I'll be fine.

[enkeivette]

He is correct about the compression. Have you called The Carb Shop in Ontario? I'm not sure what effect boost has on a power valve.

PV works fine with a blow through, concerned about the PV check ball.

[BRUTAL64]

Trying to figure out what my PV check ball is doing under boost, almost ready to forget about it and tune it as it. BG Tech sucks, those red necks rarely give me any useful advice. 90% of their techs are morons.

They don't want to answer your question, they think they know what your problem is before you even tell them what's up. This guy told me that my compression under boost is 15.29:1 and that I need to run 114 race gas or I'll pop another piston.

I popped a piston because BG doesn't know how to setup a race carb to get the AFR under 15:1 at WOT! That's why I popped a piston. :mad:

He told me that race gas would correct my rich problem at cruise and magically correct any lean problems at WOT. :rolleyes2:


They really told you that??? It thought it was bad when I talked to MSD's techs. That beats them by miles.:bang:

[94cobra69ss396]

PV works fine with a blow through, concerned about the PV check ball.

How much pressure does it take to open the check ball? I'm assuming it would be more than 10psi since its purpose is to protect the PV in the case of a backfire in the intake.

I still think you are crazy to think you can run 28 degrees of timing with 10psi on 91. I'm only running 17 from 4800-6000 and I still occasionally get detonation on hot days when I've been running the air. Think about it, 15:1 compression! You need to pick up a MSD BTM so you can pull out timing with boost. That way you will be able to run more timing in the lower and mid rpm range to help with your torque output but still keep it safe as boost climbs.

[Vettezuki]

. . . Procharger says that I can run 10lbs at 34 degrees of timing on 91 octane with Al heads. . .

Let us know how that works out. Are they warrantying your engine for that application?

http://www.superchargers4less.com/procharger/images/carb_comp_ratio_chart.jpg

I like the dramatically under the asterisk part. :smack:

[TimAT]

[QUOTE=94cobra69ss396;28041]How much pressure does it take to open the check ball? I'm assuming it would be more than 10psi since its purpose is to protect the PV in the case of a backfire in the intake.

QUOTE]

I'm interested in this one too. The boost comes in from the top and would tend to SEAT that checkball. In the event of a backfire, it lifts that ball off the seat and allows the excess pressure to vent into the venturis instead of thru the PV. I can see how high boost could lift the checkball, but I'd not think it would be too likely because the pressure would be the same on both sides.

[big2bird]

[QUOTE=94cobra69ss396;28041]How much pressure does it take to open the check ball? I'm assuming it would be more than 10psi since its purpose is to protect the PV in the case of a backfire in the intake.

QUOTE]

I'm interested in this one too. The boost comes in from the top and would tend to SEAT that checkball. In the event of a backfire, it lifts that ball off the seat and allows the excess pressure to vent into the venturis instead of thru the PV. I can see how high boost could lift the checkball, but I'd not think it would be too likely because the pressure would be the same on both sides.

I would imagine as long as the differential MAP is lower than supply, it would not be a problem. It should always be lesser when accelerating, the only time the PV should be active.