[Ryridesmotox]

Originally Posted by 94cobra69ss396

I don't see how you can get peak hp and tq numbers from airflow data. I didn't tune my Cobra, Steve at Powertrain Dynamics did, but I know that when my buddy (Ron's Friend on here) did his twin turbo GTO we took it to GTR to run it on their dyno to get the power numbers.

Ohhh I see what your saying now I totally missed the point you were making before, my bad... no, you can't determine peak numbers based on datalogs.... you can get a pretty good idea of where you car will make the power though. Example, when my car makes 'x' lbs/min of ve airflow at 'y' rpm, that RPM should yield the peak point in the powerband. as far as peak numbers, you can guess based on acceleration at a given weight but that is a total shot in the dark really. I totally missed what you were saying before lol, my bad.

[94cobra69ss396]

Originally Posted by Ryridesmotox

Ohhh I see what your saying now I totally missed the point you were making before, my bad... no, you can't determine peak numbers based on datalogs.... you can get a pretty good idea of where you car will make the power though. Example, when my car makes 'x' lbs/min of ve airflow at 'y' rpm, that RPM should yield the peak point in the powerband. as far as peak numbers, you can guess based on acceleration at a given weight but that is a total shot in the dark really. I totally missed what you were saying before lol, my bad.

Have you dyno'd your car to validate that?

[Ryridesmotox]

Originally Posted by 94cobra69ss396

Have you dyno'd your car to validate that?

Yea, for my car the datalogged airflow is almost a mirror to the curve of peak torque. I will try and find my data sheets to post up. I have the dyno runs on my other computer along with my datalog info

[94cobra69ss396]

That'd would be cool to see. So max tq happened at max airflow. What about max hp?

[Ryridesmotox]

Originally Posted by 94cobra69ss396

That'd would be cool to see. So max tq happened at max airflow. What about max hp?

I am gonna have to look at my logs. I dont want to shove my foot further in my mouth lol... I know that peak VE airflow (Volumetric Effeciency) is where you will hit your peak torque. But I don't know where the peak hp comes in on the logs. But I don't really care about HP since Torque is what moves you haha... what is that one saying: Oversteer is the back hitting the wall, unersteer is the front hitting the wall, torque is how far the wall moves when you hit it and HP is how far you along the wall... or something like that?

I'm not sure if these pictures will work since they are off another site. They ar kinda chopped and messed up but they kinda show what I'm talking about

Here is a picture of a log. Ok so in the second row down the white line is the VE airflow. In a 3rd gear pull @4400rpm the airflow is at 27.00 lbs/min. On this picture I wasn't looking for a VE shot but I was showing the fuel rail pressure drop.


In this picture you can see that the VE airflow is at 30.25lbs/min. If you look at the graph you can see the line kinda peaks between 4600-5000rpm. It's hard to see, sorry about that, and my injector pump had to catch up before the engine would make real power. But that is more or less fixed now.


And here is an old dyno sheet with a horrible slipping clutch and the wheels were losing traction on the dyno, just a shitty run but its all i have access to right now... sorry about the huuuge weird spot. It is on 91 octane so it isn't exaclty a proper analog for the comparison I'm trying to make.


That dyno is on a straight 91 octane tune, and the log is on an E85/91 50/50 mix tune, I couldn't find a picture of the log that went with this dyno run soooo the logs will show the airflow a little later, this was pretty early on in my tuning and I was still having pretty bad fuelling issues. hopefully it kinda answer your questions more than it confuses everyone

[Boosten ya]

Originally Posted by 94cobra69ss396

How do you know where the peak hp and tq are without dynoing it?

I use virtual dyno.

[Boosten ya]

Originally Posted by Ryridesmotox

That build looks sic dude. I have the same injector issues as you do since the cobalt ss uses a 2.0 DI motor. I'm not sure how your HPFP works but ours is a cam driven unit. We currently have 2 options, a new set of cams with a different fuel pump gear to turn the pump faster, or a 5th injector in the intake manifold. Our EVAP system uses a port right in the middle of the intake mani directly behind the throttle body. Its perfect for putting a 60lb injector in. For me, it would allow me to run straight E85 instead of having to mix it. I'm not sure how your car responds to E85 but mine will demand about 2300psi of rail pressure from 3000-6000rpm (on my e85/91 mix tune) and the car will only be able to provide about 1000psi rail pressure or less until like 4500rpm. I can't get enough fuel in the cylinders. Having the extra injector would allow me to get enough fuel in there based on boost levels. Just cruising around, I would run on the DI only, then if I needed the extra go juice, the 5th injector would get me there. There are a bunch of cobalt guys trying to do a dyno day this summer, I'll let you know when it is so you can get a run on the rollers, I think they are talking like $50 for 3 pulls on it but I don't have all the details as of yet.



I'm not sure what tuning software he is using (I'm sure he said earlier in the thread) but most will show peak airflow numbers, That is what I usually use as the guess for peak power at a given RPM. When I tune for my E85/91 mix tune it I get ALOT of airflow from like 3000-5000 RPM, my torque band looks like an LS block V8.

Sweet yeah let me know man.

Yes we have a HPFP that is driven by the exhaust cam. Our release valve opens at around 1950psi, ptp has a RV that holds to just under 2150psi. We have fuel pump internals that get us to 2k psi no problem but thats it.

I wonder if a new exhaust cam with bigger HPFP lobes would work for us.

[94cobra69ss396]

Originally Posted by Boosten ya

I use virtual dyno.

What's virtual dyno?

[Boosten ya]

It's a program someone made. You datalog your car. 4th gear start at around 2500 and takr it to redline. Just like a dyno pull. Load the log in VD and enter your car weight, driver/passengers weight, and tire size. And it gives you your estimated numbers.

The program has a bunch of cars main stats I.E. stock tire size, weight, and gear ratio.

http://www.mazdaspeedforums.org/foru...al-dyno-94798/

[Shaolin Crane]

Have you scaled your car to know it's exact weight?