Trying to figure this out...I know there are alot of people that run a 2.7 w/42.5 and some say you can't, but with a custom dyno tune would the tuner be able to tune the car with the 2.7 and 42.5???? Would the 2.7 or 2.9 produce more HP w/ the 42.5???

 

The 2.7 would make more power than the 2.9, its all in the tune, this has been argued many times, I have been running it with a great tune, for a while now and no problems, other will tell you different.

 

I know, that is why I figured the tuner could tune the 42's with the 2.7....I just didn't want to go out and buy a 2.7 if they couldn't tune it to work with the 42's. I know it has been argued, but most of the arguements have been just slapping the 2.7 on w/ the 42's with the stage kits or there own personal tune....so I thought a REAL TUNER would be able to make it work......

 

By the way, Shortbus what step colder plugs do you have??

 

Of course it will work, but your injectors will be around 115% with supporting mods... which is troubling to me. It means that neither the piston protection or COT protection can be engaged by the car, and it means that you can't control your fuel for the last 700 rpms...

 

Well that sounds scary.....but thanks Spooner....

 

i have a 2.85 on and a 2.7 in my trunk, i think i just may tune with the 2.85 to be safe and see if i can still use the stage 2 injectors when it comes time to tune, the jump from a 2.9 to a 2.7 in horsepower is minimal, you see more torque though which is good, remember with a 2.7 at 7 grand yer overspinning the blower, even if its for a milisecond yer still doin it, plus more heat with a 2.7, like i said, i think i just may tune with my 2.85, but well see how greedy i get and how much coin i got when it comes time to tune.
atleast with a 2.7 you wont get any slip if you have the stage 2 belt, im not sure how much boost a 2.7 should make, the guy tuning my car saya anything over 18, he wouldnt unless water meth is used, which is another reason why i am reluctant on tuning with the 2.7.

 

The over spinning doesn't worry me at all, the GenV Eaton is good for 16k continuous RPMS, so that's the least of my worries.

As far as boost goes, I see some pretty crazy claims all the way around... I see a consistent 15-16psi with the 2.8"... 2.7 or 2.6 MIGHT hit 18-20... MIGHT...

 

My 2.6 almost touches 18psi when we're logging with HPT, and NoRemorse will hit over 20 with his 2.5.

 

If a 2.7 hits about 18 ish psi i would really wanna tune with them, ofcourse the 60 pounders would go in aswell.

 

Is your 2.85 closer to a 2.9 or a 2.7...or is it an actually 2.8??? Is it from ZZP???

 

I would go with 60 lbers with a 2.7 just to be on the safe side. It's better to be safe than sorry.

 

Why dont you just go in the middle and get a 2.8.

 

like at my altitude, i think i would be able to run a 2.7 fine on 42.5 injectors, but i would also have Some HP Tuners and a nice tune to go along with it. But i lose at least 2psi from being up here. Stock i only run 10psi instead of 11.5-12psi.

Gabriel

 

That is where I am leaning towards, but Billetflow does not make a 2.8 , so I am looking at ZZP's 2.85.....

 

You WILL be over 100% duty cycle on 42.5 injectors with the 2.7" over about 6300 rpm. I'm currently running the 2.8" on the 42.5 and after some data logging, I'll be going back to the 3" until I get some 60 lbers and a custom tune. Regardless of whether or not you get a custom tune, I'd be wary of going with the 2.7" on 42.5 lbers unless you lower your limiter to 6200 or so (which is, of course, no fun considering that's where the most power is at).

 

You can run the 2.7 with the 42's no problem. Just make sure you have a good tune in the car. It has been proven that it is safe

 

i have the zzp 2.85

 

No, its not safe, please don't say that.

 

Define proven. Meaning it won't blow up the car if you do it once? I ran the injectors ragged on my road courses, and it was fine. I couldn't get the 60's in fast enough for me. If you call safe uncontrolled A/F ratios for 10-20% of the revband, and being so on edge that the car can't even activate it's own protection schemes EVER, then yes it's safe.

However, I'll go with what proven engine builders go for. 80% duty cycle. No reason have an injector fail on you at 20psi and 7100 rpms. That's alot of money to waste, when the fix is $190 shipped...

 

Right on the money.

Duty cycle over 80% will accelerate fuel injector wear and will lead to premature failure. Duty cycle over 90% will result in an extensive loss of precision of commanded fuel. Duty cycle over 100%, well, the commanded fuel just isn't being delivered no matter which way you look at it.

So, unless you bump your rev limiter to a point where your pulse width will result in 80% or less injector duty cycle, I wouldn't call it safe.

 

Yup, with the 42's, I had no idea what my A/F would be after 6k. Sometimes it would go to 10:1 by 6300, the injectors would max, and it would lean to almost 12.5:1. The next time it might run steady at 11.5:1 and the injectors would max at 6500 and lean out to 12.5:1.

Can't set the timing because of the varying A/F, and god help you in the winter when it's -10 outside and you floor it!

 

Well I after hearing all of you, and thank you all for the help...I will be going with ZZP 2.85 press on pulley...it is between 2.9 and 2.8 so it should be safe...and it will give me a little more power, but not as much as a 2.8. Again, thanks for the help...but I would rather be safe than sorry......

I am doing the press on type because I will not be changing the pulley again, once I get this Dyno Tune done, then no more modding...Performance wise anyway...

Again, Thanks for the help.

 

2step colder plugs, running about 19lbs, but that is going to be less when the catless d/p gets on.

 

well im gunna buy the ca stage 1 kit and it comes wit a 3.0" pulley when ppl say u need to run 42.5's on the car also but they tune it right for it jsut send ur ecu to cobalt addiction theyll tune it for u