Hey guys. Well, the boost bug has bitten me and i think i'm gonna go ahead an build the bottom end. With that said, i've never really seen anyone discuss AFR tunes with some build. I'm gonna go ahead and make plans to purchase some pistons and rods, get that done and maybe by the end of the year some headwork.


Currently running 100% stock on 8lbs with an 11:1 tune (250whp/250wtq)


Questions:

-What are some idea's of safe to mild AFRs with (8.8:1) pistons+rods? I'm thinking 12:1, 12.2:1. Ideas?

-What amount of boost? I'm wanting at least 12-12.5lbs (again, 8.8:1), but i'm wanting to stay returnless and on 550 injectors.



All of this on Greddy Blue

 

uhhh im running 8.5:1 and under wot im like 10.4 and thats on 13-14 psi

 

why would u want to run low compression pistons for 12lbs boost ? u will make less power then with stock pistons , the only benefit would be timing at those boost levels with low comp.

318 why r u running so rich? that defeats the purpose of having a built bottom end , u would prolly make more power at 10lbs with AFRs around 12.2-12.5

 

I dont know ask the tuner who tunes my car, tony palo at t1racedevelopment.com

 

It's not uncommon to run rich at WOT. It's safe. I've run as rich as 10 flat at WOT. I've seen 10.7 as well, depending on the temp outside. With a built bottom end, I would expect to run at least 14lbs of boost, ESPECIALLY if you have a Meth/water kit too.

 

^^ no offense but I have never heard a good reason for running rich . 11.5-12.5 is usually optimal .

 

Rich is safe....I thought 10,11 is the AFR you want...I havent heard alot of people tuning for 12 AFRs

 

On the contrary, I've never heard a bad reason for running rich either. I concur that the OPTIMAL A/F ratio is that of 11.5-12.5. The Unichip tune from Tnetics I think runs in the 12's at WOT. You would achieve the MOST HP you can at that threshold. But there is nothing wrong with playing a tad bit safer in the 10's either.

I Love the fireballs that come out.....

 

yeah, text book is 12.5 being the limit and down to 11.5. But a safe tune is a little on the richer side. I normally tune my car to lower 11's. I think low 11's with maybe dabbing into the 10's as the way to go...just the lower you go into the 10's the more it hurts your pockets at the pump!

a Lot of if depends on your CR....some people with higher compression like to go on the richer side and vice versa. In the end it's personal preference and what you feel safe with. are you willing to gamble basically. but nothing wrong with 11:1 AF's

I've had a tune that was in the mid 12's on low in the boost maps and it resulted in melted pistons....I'll never tune there again. (the last time I'll pay for a tune!)

but my pistons we're on the cheap side...(SRP) Weisco's from here on out.

 

Detonation is Detonation is Detonation... It doesn’t matter what kind of pistons you have, they will eventually fail with detonation present. With a built bottom end you can get away with more before something happens but it is still not a good thing. With pump gas you should really stay in the 11's no matter what unless maybe you are running low boost with low compression pistons (less than 7 psi… but who would bother doing that??). You should not really bother with leaner A/F’s until you start running race gas of some sort. Race gas is what will really change how much knock you can keep in check.

 

Been boosting for a little over a year now. Tune has always been into the 10's at wot. Originally on 7 PSI, now on 9.5-10.5 PSI with a stock block. 93 octane pump gas.

 

maybe I didnt specify , the guy wants to run low compression which leads me to beleive he wants to make the best power , which is between 11.5 and 12.5 with a built motor and correct timing it should be safe .

running too much fuel will eventually wash the rings and cylinders " raw fuel taking the oil from the cylinder walls" . I dont know what AFR that happens at but I do know it happens.

 

I didn't have detonation...I only had high cylinder temps...those pistons are horrible for my set up and know of quite a few people the same pistons did the same things to them...but I feel you on the rest....

 

not the "best" power, just more power reliably. Yes, lower compression will yeild lower numbers on the same boost level but lower compression allows for reliable higher boost

 

^^^^ all I was sayin as far as CR vs HP is that if all u want is 12-12.5 boost then just keep stock bottom end . find a good tuner and it will be safe .

 

Ditto

 

10.0 AFR may work but it's certainly not the safest power. Your EGTs go up and it's not good for the motor. Ideally I'd say 11.5 is a good target AFR to shoot for, and has a little bit more tolerance than say a 12.2 or so. Ignition timing in relevance to this plays a large role as well.

toyotaracer, outerheaven, and kutsuju, are all correct. 10.0 may work, but a slightly leaner AFR is actually safer. You make more power, consume less gas, and run lower EGTs so why not?

Matt, I'd shoot for 11.5AFRs for daily driving. And with a built bottem end 14psi isn't a stretch at all for the motor.

 

The only reason I would make mine leaner to 11's is just to squeeze more power out of it. Wether or not it's quote-unquote Safer at 11's than 10's is more or less a breeze in the wind, as I've been running low to high 10 A/F ratio's since I had the kit put on, which was a little over a year ago. With me beating on it just about everytime I step in to the car.......guess we must have one of those magical motors.

 

Proto, how many boosted cars have you had before this one?

 

WOW, this post has been helpful. I've been running 10.0 at WOT, not tuned. I may also be shooting fire ***** cuz I hear popping from the exhaust once in a while. So me being on a stock motor should shoot for 11.5-12.0 at WOT?