Ryan23silverado

iTrader: (1)

I am just curious as to the most powerful Air/Fuel ratio to be at for a boosted application. Safe would be somewhere around 11.7:1 correct? Highest numbers would be somewhere around 12.0:1? I guess this question would be reffering to stock (non-forged) pistons.

On my dyno I tuned it to be approx. 11.7:1 from 3600rpm-6000rpm (5800rev limiter) Is that good to have it just flatline like that, or should the fuel mixture increase only as rpms increase? I have a twin screw SC, and full boost is seen at anything above 2000rpm and wide open throttle.
Thanks

Texas Terminator

as high as you can without detonating/losing power. have you scanned your truck under full throttle? any KR?

NicD

iTrader: (7)

In the hell that is AZ with awesome 91 oct gas and high temps during the summer, I tune for 11.5-11.7 on a dynojet.

red ws6 99

Every kit and setup is different. I run 9 lb of boost on an Incon kit with 91 octane. I can vary the AFR from 10:1 to 13:1 (in car wideband) with no change in power or detontation. Leaner than 13:1 and all bets are off. Of course this is on a low of 19 deg advance at 4400 rpm then ramping up. Also this is at 4200 ft elevation so power output is pretty low and therefore tuning can be a little off with no ill effects.

Gary

ChevyNo1

Gary, you can vary THAT MUCH with no change?? I would have thought that would make a big difference . . .

Also . . . so you start at 19 and ramp up to what? And is your motor stock so far? I run a low of 15 and ramp up to only 17 on 91 octane as well . . . but I haven't tried bumping up the timing yet.

- Dug

red ws6 99

4800 rpm at 19 deg and ramp to 24 deg by 5600 rpm. I get most of knock down low when boost first comes on. Still need to tweak the those a little more.

I am only making ~460 fwhp based on maf air flow. So I am not making a huge amount of power and probably why I can get away with what I am doing. For safety the timing will be dropped at least another deg, since I am right on the raggged edge. Engine is completely stock even valve springs, etc. I have a boost block so the turbo actually spool pretty good. They actually make full boost by 2000 or so with an aerochamber muffler (mine cats). Before the boost block I would not make full boost until redline with the aerochambler. Before I put exhaust on the car, I have full boost by ~3500 rpm. I will be going to the track on Sunday. Its supposed to only get up to 45 deg, so the horsepower should be a little higher, but E.T. will suck most likely.


Gary

ChevyNo1

FWIW, my maf air flow #'s in Autotap aren't even close to what I dynoed . . . I don't have the #'s right in front of me, but they didn't match up at all from what I recall. My PCM thinks my knock sensors are shot even though I've replaced them both, so my next try is to get a new PCM and see if that helps. If not, I'm stuck with tuning by ear like the good 'ole days. So I'm hesitant to play around too much with my timing.

What is a boost block??

- Dug

red ws6 99

I may try to get some dyno time (just to see what it makes) at MSD electronics or another place that just opened up. I am trapping at 115 mph on a fully loaded Trans Am, so its not to bad. I have a relief valve and check valve in parallel inbetween the engine and the actuators. This blocks the boost signal until the relief valve opens. This means the actuators are completely shut and no more slowing creeping open until there set point. This makes spool time as fast as it can be. This is about the only way to do it with the single port actuators. All of the boost controllers I have seen that will work with single port actuators are bleed type. This means spool time is slower. There are a few similar setups that use relief valves that slowly open with pressure, but the kind I used Nupro (Swagelok) which open at whatever pressure you set them for. I get no boost spike because the relief valve (adjustable checkvalve) and the check valve (.3 psi opening pressure) will regulate the pressure at the set point. The two valves are $30 total plus fittings. I have real make shift setup out of brass fittings at this point. I will either switch over to AN or machine a few adapter blocks so it looks nice. I did not make the controller so it could be adjusted in place, which means I won't be fiddling with the boost level much. I also bought a $30 Airtrol regulator that is adjustable with a **** on top. It is so adjustable it takes 2 full rotations of the **** to get a 1 psi difference in open pressure.

Gary

MillsMotorvation

Good information

stevieturbo

If you were on the dyno, surely you would have seen what produced the most power when tuning ?
Isnt that the point of using the dyno ?

NicD

iTrader: (7)

Holy thread revival, I saw it pop up and I was like I don't remember posting in this thread. LOL

stevieturbo

Haha, I never even noticed that. 10 years !!!! must be a record