dhahlen

iTrader: (5)

Car was being tuned by a reliable tuner... read my sig for the setup...

Basically anything above 7500 RPM would studder like it was getting too much fuel. When the tuner tried to lean it out, it wouldn't go away... he didn't want to lean it out too much cause of the chance of detonation.

This was only at 10psi... and we couldn't get it to stop sputtering over 7500 RPM, it would happen everytime. The spark plugs are new, all NGK 9's, and fuel system is solid, 850/1600 cc injectors, clean fuel filter, fuel pump wired for constant 13.5vdc.

Not sure if the wideband is reading incorrectly, but its not running lean... just feels like too much fuel is being dumped into it and its bogging out. Works fine throughout the rest of the run, but 7500+ it eats it...

Any ideas?

Thanks

bcty

ignition not keeping up? could try aftermarket coils?

dhahlen

iTrader: (5)

At 10 psi? That doesn't make sense. The HKS Twin power with the coil pack should be good for well over 17psi.

2a+RoN

try changing out the plug wires just to see if that would help at all.

dhahlen

iTrader: (5)

Good idea on the plug wires... They are racing beat wires and fairly new, less than 3k on them... but they've been pulled and moved around a lot... I'll pickup some NGK's tomorrow.

What are you up to Aaron? Want to help me throw on a 99 lip right now? I got to cut a section out to fit the oil cooler.

GUITARJUNKIE28

are you making power above 7500?

willjs7

iTrader: (1)

its that damn 61r

jk.

GUITARJUNKIE28

nothin' runs like a deere eh?

dhahlen

iTrader: (5)

It feels like it's dumping a ton of fuel, but we leaned it out and it still did it. Not sure if the wideband is giving an accurate reading, or if the spark is working... i am going to pickup some magnacore wires, and replace my 850's with some fresh ones.

As for power... it isn't going any faster at 7500rpm.. it looses a bit of power.. as you would expect from a rich spot.

GUITARJUNKIE28

turbo cars usually don't peak much past the low-mid 7's with the stock manifold.

do you have a dyno sheet to post--no matter what it looks like?
your injector pulse-width is going to follow your torque curve, NOT your hp. so you should probably have a lower IPW @ 7500 than you do at 6500, or wherever the torque starts to drop off.

of course, this is assuming all other problems are taken care of. ie: no boost creep, etc...

Asleep

Are you running the meth injection?

BLUE TII

iTrader: (9)

I have had this same exact problem on my car twice from two seperate problems.

First time I had terrible stuttering/loss of power ~6,000rpm. Turns out my 720cc and 1600cc injectors were hitting 100% duty cycle because the Walbro couldn't maintain fuel pressure- some jerk sold me the LOW PRESSURE Walbro 225lph instead of high pressure Wally. I had upgraded my ignition to the max chasing this problem.

Second time I had a hard drop in power at 7,500rpm. Data log of MAP signal showed boost pressure fluctuating 3-5psi in 10ths of a second at full boost depending on rpm.

Moved MAP sensor vacuum lines from the nipples on the primary runners on my 3rd gen UIM to nipples on the 2ndary plenum (behind the throttle body) and it pulled hard and smooth to 8,500rpm redline.

The boost pressure fluctuations were from dynamic effect pressure waves in the intake system runners.

Some things to check on.

GUITARJUNKIE28

good call...forgot about that one.

jacobcartmill

iTrader: (6)

dhahlen

iTrader: (5)

Yes, methanol sprays at 8psi and up, but it's tuned for the methanol. The AFR's are at 11.7-11.9 when I am hitting 7500rpm... and it's breaking up... popcorn exhaust.

I am going to check and see where that vac line is going

dhahlen

iTrader: (5)

Injector duty isn't an issue.

I checked the map sensor line and it goes right to the UIM near the TB.

What are the chances of a bad leading coil or plug wires? I am on a stock leading coil and twin power with racing beat plugs?

Perhaps a loose ground on the leading coil pack?

GUITARJUNKIE28

if it were bad ignition, not all of the air and fuel would have reacted--leaving leftover oxygen molecules and a bunch of CO and hc's. it'd probably show up as a lean condition on the wideband.

not talking about max injector duty cycle... what is the pulse-width, compared to the 3 or 4 rpm slots below it?

dhahlen

iTrader: (5)

pulse width... no clue, dont have it in front of me.. i can search for it on the commander. Don't have a datalogit to hook up to the FC right now.

GUITARJUNKIE28

post up a screen shot if you get a chance later on.

dhahlen

iTrader: (5)

what do you want a screenshot of?

I checked my CAS gap and it was off, it's within 1-2mm now. That didn't fix the problem, still getting breakup.

GUITARJUNKIE28

the fuel map. specifically the regions between 5500 and 8500 at the load you're running.

twokrx7

iTrader: (1)

Check the spread in AFR in each cell on the log, if you are having ignition issues you should see a wide margin between MIN and MAX in the upper rpms, say 0.5+. On a healthy ignition I am used to seeing a difference of 0.4 afr or less.

dhahlen

iTrader: (5)

I can take a pic of the commander, but I am trying to get ahold of my tuner so he can send me the map or take pics of the FCEDit software for me.

I don't think I can get to the fuel map using the commander, only the base map which is corrected for 1.0 across the board.

dhahlen

iTrader: (5)

I gave my symptoms to Steve and he said I needed a colder spark.. I told him I was using 9's and he said use 10's or 11's.

bcty

i think 9's are perfect.. 10's would be excessive for 10psi.. you could try iridiums that might clean it up a bit.. what is your af like from 6500-7500? how much does it drop when you see it go rich?