Ok so I got my car dyno'd and its best run, the first run it put down 243whp and 222.8wtq SAE Adjusted! Thats up from like 215whp and 190wtq SAE adjusted. All pulls 3rd gear.

So I am quiet happy about that, but I am concerned that the runs were so inconsistant.

My AFR was mid to high 11s when at WOT.

See pic below.

Comments Questions... whatevers?? Any ideas on the inconsistencies?

-Rich

 

inconsistency looks like heat soak. get a gauge and check IAT2 temps over the runs and i bet u see increase between 1st and later runs.

edit: NICE NUMBERS THOUGH!!

 

Nice numbers, congrats. Yeah it might be big heat exchanger time for you.

Did you guys really make 10 dyno runs?

 

yeaht hats what i dyno'ed at before my 3" exhaust. i got a heat exchanger on the way

 

get the gmpp exhaust or corsa and I bet the car will really be jumping then!

 

Damn good numbers man. Compare it to your other dyno now. Look at how much earlier your torque comes in at, and the gain through the mid range. I think you be even happier once you analyze the two more closely.

 

Only prob is my other dyno graph isn't sae adjusted... but that shouldn't matter when comparing the curves.

Thanks for the props people.

-Rich

 

Most dyno shops keep a record of all your pulls and can print them out for you if needed. I had my shop lay the old graph onto the new graph for reference to see where my mods helped the most, and I was pleasantly surprised with the torque yield like I said. I'm sure if you called them, they could hook you up with the original or SAE corrected for both laid onto one graph and email it to you. Definatley nice numbers though.

 

A little bit off topic, doesn't stage with a 2.8" and 45 lbs/hr Injectors max out injector cycle?

 

great numbers, did they log the car for you? if so you can see if it was heat soak. When I dyno, my fans and intercooler are 100% on all the time. We wait till it hits 100* on IAT2 before doing another run.

 

yes at about 6000rpm. If you don't want bigger injectors, run a meth/water kit, it's cheap octane with added fuel up top.

 

umm... proof please?

 

lol since when does a 2.8 max out the 45's?!?

 

Guys this has been talked about over and over again.

First of all they are 42lb. injectors.

Second, A 2.8" pulley gives your fuel injectors 100% duty cycle around 6,000rpms

A 2.85" pulley is about 90% duty cycle at the same rpms.

Anything 90% and up is no good. Your injectors can go static.

So the best thing to do is run no bigger than a 2.9" on 42lb. injectors or install 60lb injectors so you can go 2.8" and smaller.

Just trust me on this guys.

EDIT! Here is the thread. https://www.cobaltss.net/forums/show...ght=tuned+dyno

 

considering how many people put a 2.8 on stage II....im curious why i havent heard this before....and/or heard of people WITH that setup having issues....

 

.05 makes that much of a difference...

 

It's because people just bolt **** on but don't know a thing about supporting mods and or what's safe and what's not.

Your average person doesn't know what their AFR is at WOT or the IDC's (Injector duty cycle) they are at.

That's the problem. You either have to dyno the car with AFR or have a wideband hooked up to see some numbers.

Injector duty cycle is very important but most people have never heard of that term.

The numbers and advice I gave you guys are real. A 2.8" pulley at 7,000rpms is like 120% duty cycle. That's bad. Your car has no control over the injectors at that point. That's what static means. Things go boom that way. Plus remember you're not always sitting at 7,000rpms so the car will drive OK. It's just hitting that point one too many times will do you in.

Absolutely. Remember our superchargers are air-movers. They should be called blowers.
That little difference (0.05) X 7,000rpms is a completely different AFR. (Air to fuel)

 

interesting. thanks for the info.

Id love some input from people running the 2.8's on this.

 

Not a problem bro. There will be others chiming in that will agree.

I guarantee the 2.8" guys that tell you all is well don't know their IDC and AFR @ 7,000rpms.
All is well for now......... This is why I run a 2.9" pulley. I won't touch 90% IDC at 7,000rpms.

 

Thanx for the info. How do I find out my IDC? HPT or datalogger? Also, My AFR was fine at the dyno, a little rich actaully at 60 deg weather.

On a side note. There isn't any difference between 2.79 and 2.8 so the .05 difference isn't going to be that much, maybe a little at 7krpm. In my mind not enough to changes pulleys.

 

Almost all the cobalt's in our group (7+) run a 2.8 with 42's and none have had problems and 2 have HPT, I'm skeptical but also have an open mind about the 2.8 causing problems. I would think it has a lot more to do with the tune than someone might think.

 

Hmm I dunno. We keep going over this but its allways different. I thought our conclusion was to up the stage 2 injectors (including 7k redline) when you go below a 2.7 not below a 2.9...

 

that was exactly the comment i was waiting for.

Thats the number that i remember reading alot about.

I distinctly remember 2.7 being the threshold. but once again im just going on what ive read. i dont know it for fact.

 

Just do everyone a favor and ask those 2.8 guys in your group what their IDC's are at 7,000rpm.

Distillion's 2.85 had his IDC's at 90% @ 7,000rpms.

Anything 90% and up, the injectors can go static.

 

Thats why I asked how exactly/ whats the best way to find out! I'll do it right now.

Edit: Just did, waiting for reply. They wil be using HPT.