91Camaro_RS

iTrader: (3)

ok so i have a 91 camaro, 350 TPI, headers, GMMG exhaust, intake, the rest is basically stock. last year i dynoed and made 198hp and 298 tq.

this year this is the result


lately i have been playing with Tuner pro and i have been adjusting the AFR vs RPM graph based on what my WB02 sensor says while driving. im shooting for 12.8:1 at WOT. so basically on the first pull my SES light came on so i swapped out the chip (had problems with it that morning) and put in a backup and it was fine to this day. if i remember right the tunes i used were stock AUJP bins with the EGR turned off because i have emissions deleted. if it was a tune i used then it just had the AFR changed but i leaned it out up to 4200rpm, on the graph it gets leaner so it doesnt make sense that it was one of my adjusted tunes because it should have got richer. can anyone explain what these drops are in the graphs and why i lost so much torque? im pretty new to using Tuner Pro. Thanks in advance

Fast355

iTrader: (2)

Those dips look like the torque converter locking at WOT. Numbers seem low. How much timing advance are your running and what does the curve look like?

91Camaro_RS

iTrader: (3)

Im running the stock 6* btdc. And can i change the lockup in the prom?

Kevin91Z

iTrader: (1)

The torque converter locking up should make more power, not less, because the transmission becomes direct-drive instead of losing power thru the fluid. Are you at a high-altitude? Those numbers are terrible for an L98 with your mods. If the bottom end is stock, then it looks like you have issues with the pistons, rings, blow-by, etc. Whats interesting is those dips are evenly spaced from each other, but the air/fuel changes in the bottom graph are not.

Orr89RocZ

iTrader: (20)

Never seen a dyno like that before. How did it sound during the pull? It almost looks like engine is cutting out momentarily and dropping power. What changes did you make to the bin file? There shouldn't be huge changes from stock tune for fueling and only small changes in timing to optimize for those mods. The air fuel readouts don't look right at all! Surprised its that rich for one thing but the end lean out is very strange

The power dips also might be from huge timing swings. What do all your timing table settings look like? Most traction control setups use timing retard to control torque output and big retard in timing can kill power like that

camaro1185

Just for a point of reference, I have a 100% 78K stock motor. I just dynoned 187/260 and that was pretty rich at wot (11.8afr IIRC). From what I have read, l98s should be around 200hp stock, so it looks like both your motor and mine may have some problems. With your mods, I would guess you should be somewhere in the 220 range?

RBob

iTrader: (1)

The leans outs at 115 MPH are likely the vehicle speed limiter shutting off the injectors.

GM does run WOT throttle rich to protect the cat-cons.

It is strange how the power drops are at different points (MPH).

Check that the go-pedal is opening the TB all of the way.

RBob.

Orr89RocZ

iTrader: (20)

Factory TPI 350's even have a speed limiter? I know I been 130+ in mine when it was stock and didnt find the limiter

RBob

iTrader: (1)

I don't know, if all L98 cars came with Z rated tires then the vehicle limit is set to 255 MPH. Would need to check every calibration GM used. I know for a fact that the 5.0l TPI cars, many have a speed limiter. Example is AXXC (5.0, 5-spd) set for 108 off, 106 on (Dang, that is lower then a stock 3.1l RS @ 115/112).

AWFU (5.0L, auto) is set for 115/114, which matches the graph.

The other thing is, is this car stock with an L98, and is it even using a L98 calibration. There is a mention that it 'could' be AUJP.

RBob.

JP86SS

iTrader: (1)

Fuel filter or fuel pump problem?
Goes lean right after the drop off like the regulator closed and there isn't enough fuel flow to keep up.
I would think air restriction (duct collapsing) if it was going rich but because it goes real lean I'd suspect something fuel related.
Did you run datalogs during the runs?
If so, look for change in voltage (belt slipping at high speed) and pump volts dropping off or something.
And you'll know if you hit the ECM rev limiter, drops like a rock and scares the crap out of you its so abrupt. It would recover better than what is on the graph too.

91Camaro_RS

iTrader: (3)

fuel cut off is set to 255mph and the fuel pump is pretty new, its the walbro 255 lph pump and its working good, someone mentioned to me it could be the lockup converter locking up too soon?

Orr89RocZ

iTrader: (20)

lockup doesnt decrease power tho. Lockup looks something like this:



When it locks, sometimes the rpms may dip, but the motor is now transfering 100% power to trans and rear, so the power at the wheels goes up, so it kinda draws a circle or a weird hook like that. Sometimes it just goes straight up alittle at that lockup rpm.

Either way it should INCREASE power.

RBob

iTrader: (1)

On the going lean, I should have thought of this before. Lift off the throttle and DFCO kicks in. Shuts the injectors off.

One thing I don't understand about the graph is why the AFR doesn't line up with the HP/Torque graph. Take the red trace, goes dead lean but takes quite a bit of time before the power graph drops off.

RBob.

JP86SS

iTrader: (1)

Knock retard could have killed the power and would recover very slowly (or not at all)based on stock AUJP settings.