eclou

Your dyno looks about the same as mine at 16psi. Respectable, but you can eek out some more. Lose the stock AFM

NZ951

I dont see how the airbox is a restriction? You are getting great spool and enough air and fuel, what will removing the airbox do?

toddk911

A little fat, but nothing that I would expect to be robbing you of those 30 more hp you were expecting. I would guess there was some roll off of boost, but yo usay that isn't the case.

However, I know many people in here, and when I went with my buddy to dyno, that the boost made on the street, is not always the boost made on the dyno. In my friends case he made 15 dead on on the street. On the dyno it would not hold more than 13 to redline. Maybe a dyno load issue??

So I would bet that might be why you are seeing less hp than expected. 1-2 more psi would give you 15-25 more hp you thought should have been there; add that to the 15hp for temps and fan and you are right there

toddk911

Also, I thought you couldn't run more than 15 psi with Vitesse on pump gas??

eclou

I thought the barn door AFM was a restriction of up to 20hp? For sure the snorkel tube can't flow a ton.

B951S

To clarify, there is no AFM, a 3" j pipe goes straight into the stock airbox. There some pictures in this thread.

https://rennlist.com/forums/showthre...t=stock+airbox

and some discussion here.

https://rennlist.com/forums/showthre...t=stock+airbox

Todd, your right, it very well could be a boost issue. Again, if I had logs in parrallel to the runs I could say for sure.

tazman

You didn't answer my question. What I was getting at is that if you tune the car on the street where the intercooler is working well then you take that and put it on the dyno with hotter intake temperatures you are going to see the richness as your temps increase. With my Tec3 the MAT sensor is in the pipe after the intercooler so at the higher temperatures I can take out a % of fuel. Did they put the O2 sensor in the tail pipe? That is the way they did it with my car and I found the same to be true.

For A/F ratios I shoot for 12.5:1 by about 5psi then after about 5000rpm I don't worry if it goes up to 13:1 because there is a lot less noise in the engine on the knock sensor and from what I have read max power is around 13:1 all the extra fuel is for cooling purposes. Now if you are going to be using the car on the track you might want to tune to the rich side because you are stressing the engine for longer periods of time and the loss in power is not a whole lot.

B951S

Yes, I tune on on the street using data logging from a WB and driving the car usually WOT in 3rd for a WOT pull so the speeds dont get crazy. I understand your point... So does that mean there is a an offset that you should build into dyno tuning on a hot day. I mean tuning 12.5 on a dyno in sweltering heat with a little fan is gonna have to satify the neeeds of the motor on a cooler day with proper front air cooling. THe link has a simple inlet air temp offset where you can specify how much fuel the computer adds accross the board for cooler IAT temps. As far as I understand this IAT correction should account for some of the differences. Link alsways told me never to put the IAT after the intercooler outlet as the transients and dynamics in temperature changes were too much for real time correction, I guess if it works for you it can't be all bad.

Anyway, I am pretty convinced the stock cold air snorkel will start restricting the motor quite a bit when you are trying to lay down over 300 rwhp. It will be interested so see what it makes once I take off.
Thanks

Chris Prack

FWIW I recently tuned an 89 car with a fresh valve job, Fabspeed test pipe, LBE and custom chips and it made 299 rwhp with the OE turbo peaking at 1 bar. He also had the AFM but with a cone filter attached. His A/F was around 10:1 and when I leaned out the curve it lost a little power as a result. This is pretty consistant with my experience tuning these cars. They like to be fat.

The chip set we were working off of were APE stage 2. We were using a Superflow dyno. You on a Dynojet?

toddk911

"FWIW I recently tuned an 89 car with a fresh valve job, Fabspeed test pipe, LBE and custom chips and it made 299 rwhp with the OE turbo peaking at 1 bar. He also had the AFM but with a cone filter attached."

With APE chips?????? and only 15psi?????

B951S

Cant see why not. I have run 17-18 psi for the last 5 k miles. Just make sure you use 93 oct and the timing is well sorted, keep the fuel a little fat. A stand alone makes this pretty easy to do.

Tom M'Guinn

Your torque curve looks a lot like mine. I bet your car pulls very hard. I've driven mine back to back with other cars making more peak HP, and the flat torque makes for a harder pulling street car. I trust your graph was adjusted for the heat. Otherwise, you are making more than the chart shows (on an adjusted/comparable basis). Keep tweeking (sans snorkel) and I see 330 in your future.

TonyG

B951S

Why didn't you simply take the top of the airbox off for one of the runs?

TonyG

B951S

Yes I was kicking myself after, I should have taken the cover off for a comparison, next time for sure.

FYI, I did a few street runs in 3rd, WOT from low down to red line while datalogging. Here is the boost curve for 2 runs back to back. I see I am loosing a psi or so, I guess there is some improvement to be had here that would help.

NZ951

I wonder why you are losing that psi? You have got the wg and exhaust and tubo to produce it...