Inconsistant dyno results. confused

moneypit94

Active Member
May 23, 2003
1,723
2
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Macomb, IL
Car went back to AFM on the dyno today. And it was a fight from the beggining. Everything was backwards. The richer it ran the more it liked it. And when you tryed leaning things out it would run like crap with less power.

It's as if the computer changes up things randomly too. I get the idle set and start working on teh part throttle and get it half way set and then it won't idle again. Or i would get both set and the next time I start the car they are both messed up again.

Got things half way straightened out and then it dynoed about 550 farily consistantly which is about 120 less then last time, so im like WTH? And So were thinking something is still messed up with the transmission or something. And Danny, the tuner, decides to do one more run and decides to lean things out just a bit more and the next run it RICHENs up super fat and hits 660? Everythign just seemed random.

Im thinking of trying out another computer and if i can set the idle consistant with it then i would take it back but until I figure out why its so inconsistant Im not spending any more money on tuning it or pushing it any harder.

By the way it hit 678 the time before last on the dyno at 15.4 psi, and then the last time it only made 550 and we thought it was because the transmission had eaten the clutches out. This time it starts out at 550 and jumps up to 660 on what was going to be the last run of the day and that was at 14.4 psi.

So im confused and there are just so many little variables in all of this im gettign frustrated. Car litterly had the best A/F on the last 550ish run and then goes super FAT and runs 660 WTH?

The tuner was like I don't know, its just got a mind of its own.

Good news is im not afraid to race it now, but i am affraid of driving around town with it being so inconsistant. lol
 
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Yeah, I have thought about something other then the PMS. But sence i take it to AFM and that is their piggy back system I thought of all people they could get it to work, and they say it will work. Don't know if i trust anybody else around with my type of setup either.
 
I do have my own wideband guage and it was fairly close to theirs, even though mine was reading out of the other exhaust pipe. And AFM tunes with the Interact software. They do the runs and datalog them and go through and add and subtract fuel as needed. Far as timing goes they never really changed the timing to much. They were trying to get the fuel taken care of before they started putting in any real timing.

It was at 10* base timing because we did check it just to make sure.

Far as the timing being in the right place during the run i couldn't tell you. I was just watching him tune. But I assume he would have noticed that.

When i say fat i mean like 10.5 or lower. And during idle and part throttle we were trying to get something around 13 or a bit higher. And it DID not like it.

Idle it did the best in the 12's. Not much luck anywere else.
 
The dyno operator should be able to look at wheel speed vs engine speed to find any driveline/tire slip.

Wes

I personally made them check that. Which was interesting actually. The better runs it made less mph per rpm, but the slopes were identical, just shifted down. But now that I say that It makes me wonder why they would change unless the tranny is doing some weird stuff too. But this doesn't explain any of the rest of the tuning issues.
 
Just threw a different ECU into the car and HOLY cow it idles and runs and if you lean it out slightly it doesn't backfire. It will start each time and idle and it comes to stops signs and doesn't quit. I AM IN A GREAT MOOD! 50 dollar used ECU off ebay and the car is actually streetable!

I was starting to think you couldn't make 150 lb injectors streetable, at least using a piggy back system like a PMS anyway. But Rick Anderson said i could and damnit i believe him now.

I think it will actually be consistant on the dyno now and can now tune it.
 
Just ordered a boost controller. And on my way up to my dyno appointment, (next wednesday) Im gonna pick up 15 gallons of E-85. So first thing is a quick gas pump tune. Probably up the boost if i need to hit 700 and then Im put in the e-85 and gonna runup the boost to about 900 rwhp and if it makes it that far pretty smoothly im gonna kick this pig and make her eat for 4 digits. Im pretty stoked right now. Defenitly borrowing a video camera. MAKE or BREAK its gonna be filmed!