Shinobi'sZ

I have a strange hesitation/cutting out while cruising under light load in OD. I will be around 2000 rpms and if I slowly roll into the gas it will start to sputter like it's starving for fuel before the tq converter begins to flash. If I drop it down into Drive and bring the rpms up to 3000 it goes away and will pull hard all the way to 6K rpms with no issue. It is all part throttle under light load and under 2800-3K rpms, just acts like it isn't getting enough gas. I have heard that the Stealth Ram fuel pressure regulator isn't that great, I ordered a Kirban. Looks like the Stealth Ram FPR just bolts up to the bottom of my driver's side fuel rail. I can probably put the Kirban near where the steel lines in front of the shock tower and remove the SR FPR and replace with a 90* elbow.





Here is my combo:
AFR 195 Heads
Comp 280XFI Cam
Dyno Dons Headers
3" Magnaflow Exhaust
Holley Stealth Ram
30lbs Bosch D3 Injectors
3000 Stall Converter
3:73 gears

Tuned Performance

iTrader: (92)

Do you have a datalog? Or wideband gauge?

Shinobi'sZ

My friend put it on his scanner while driving and it looked like the "tip in" or it was rich right when the issue was happening...cruise off idle to part throttle acceleration while underload below 2500rpms, so maybe it is actually getting too much fuel? At WOT there is no issue and it doesn't miss a beat, kick it down or drop into Drive and go WOT and it pulls up to redline fast, or from dead stop it will drive fine too at WOT. It's just part throttle off idle cruise situation that it's a little off. I manage it by just dropping into Drive, but it would be nice to leave in OD and pull light hills at 2000-2500 rpms. My wife wants to drive the car and she doesn't like when it starts cutting out, I told her to drop into Drive or mash the pedal...that was necessarily the answer she was looking for.

aliceempire

iTrader: (14)

Replacing the regulator is a good idea just due to the failure rate of the holley units. The problem you're having may or may not have anything to do with it. Fairly easy to start troubleshooting, use a pressure gauge to see what the fuel pressure is doing during such an instance and datalog it.

Tuned Performance

iTrader: (92)

I think you can still get the kirban for grand national and it would go on the rail .
can’t say what the fueling issue is without seeing some data or wideband readings.

ULTM8Z

Is this something new that's happening? Has this combo run well before.

Also i dont see a MAF sensor so i'm assuming this is 90-92?

Shinobi'sZ

It's done it since the I got the combo up and running, so nothing new after the mods. Car is a '91 so no maf, just MAP/Speed Density.

Shinobi'sZ

I purchased this one, hopefully it's the correct version.

Fuel Pressure Regulator | Kirban | Adjustable | Inline | Race | FPR (stinger-performance.com)

aliceempire

iTrader: (14)

https://wheelwell.com/austin-teter/1...regulator-6547

ULTM8Z

What re-tune was done for the new combo?

It seems like you may have too much accelerator enrichment. Short runner manifolds do like a pretty shot of AE on throttle tip in, but my experience with my miniram indicates you can definitely "have too much of a good thing." The Stealth Ram probably isn't that much different.

IROCThe5.7L

Sounds like a tuning issue. I had an issue after my HSR install where if I stabbed the throttle from a stop, but not completely WOT, it would fall on it's face for a second. Some tuning fixed that.

Shinobi'sZ

Agree. I need to either get it dyno tuned or do some data logging and get mail tuned. I don't have a data logger.

Hello, Michael

I’m having a similar issue with my Stealth Ram. I’m running the FAST EZ efi 2.0 multiport retrofit. Its like a surging or shuddering under part throttle cruising. Are you running the factory fuel pump? I’ve got 27# injectors.

Hello, Michael

So the FAST setup instructions recommend less AE for multiport engines and to tune it in the negative. But you’re saying short runner intakes actually like a little bit more? Maybe I’m too lean?

Shinobi'sZ

I am using the stock fuel pump with 30# injectors. Originally, I was thinking it could be the fuel pump, but I had a guy with a scanner do some data logging while I was driving and it definitely appears to be rich tip/in before my stall (3000rpms) flashes. Once I'm at lock up at part throttle or WOT the car runs great...it's just the part throttle boggin/lugging underneath where the converter isn't locked up. This is why I will drop it from OD to Drive and it takes care of the issue.

ULTM8Z

It depends....

For reference...On the 8D calibration in the 7730 ECM, there are essentially two different types of AE... one based on delta-TPS and the other based on delta-MAP.

I'm not sure what the FAST calibration is like...

What I've found after years of playing around with AE is that for the Miniram which is a large-plenum, short-runner intake (similar to the Stealth Ram), it likes a quick shot of AE right at the moment of a throttle change and then have it roll off pretty rapidly after that. So I'm pretty heavy on the AE delta-TPS. Since the delta-TPS is based on an electrical signal from the TPS, the fueling reaction is probably a little faster than say a delta-MAP based reaction. For whatever reason, it seems to make a difference.

So in biasing the delta-TPS more heavily, I've reduced the delta-MAP. This is in reference to the DA3 LT1/LT4 AE table values that I copied into the 8D calibration.

But too much overall AE will cause stumbling, hesitation, lazy throttle, etc...

With the facotry LT1/LT4 values, you could see the AFR dip into the 10's on throttle changes, which corresponded to a seat-of-the-pants feel of hesitation and laziness. With my modified settings, it'll go down to about 13.0-13.5 for a fraction of a second and then get to the commanded AFR and the throttle is extremely crisp and linear.