My question is, is there anything in the TUNE that can cause a lean condition that actually pulsates in a rhythm at that load, becoming worse as the load increases? If you go into open loop it's gone. The trims are pulling fuel out so I know I'm too rich if anything but it still occurs. I've had lean conditions in areas on cars I've tuned but they may hesitate, quit accelerating, even misfire. But they don't act in a perfect rhythm like you're on and off the pedal a bit, 3-4 times per second.

I have disconnected the EGR, monitored fuel pressure, checked many times for vacuum leaks, swapped upper intakes from the JLP back to the C&L, etc. The truck runs great at idle, light throttle, and wot. But at about .70 load and/or 350 throttle position it jumps into a lean pulse swinging from 15:1 to 16.5:1 in an even pattern, 3-4 times per second, with the rpms and blower noise in unison. Almost feels like you're pushing the gas pedal up and down. Once you go beyond to open loop it's fine. It's like the engine will not run happily at 14.64:1, it wants to be in the mid to upper 13 A/F range.

I dropped my open loop setpoints to 350 TP and .70 load and then re-worked the maf transfers and it runs great. My problem is the guys from SCT seem to think it should be happy at 14.6:1 at those loads/throttle position. I'm wondering if you tuners have fought this or can think of anything else that could be causing it. The tune the way I did it seems to fix it, but is it just covering something else?

Here's my mods:


03 Lightning NLP2
ported heads
Stage II crower cams
KB blower at 18 psi
JLP sheetmetal intake or C&L with C&L tube
Accufab monoblade
SCT big air maf
60# injectors
twin 255 pumps
stock manifolds and exhaust (did it with high-flow cats and cat-back also)
alcohol injection
cai


Jody

 

I didn't know you had 60 lbs injectors. They seem large, but you have the computer to program them right.

 

Yes, the programming is set up for the 60# injectors.

Jody

 

Let me know if disconnecting the injection system helps. I read the SoCal forum.
Like I said mine only starts at 8 lbs of boost, so I don't use much of the Walmart water and I only have 50 lbs injectors.

 

I already tried shutting off nearly everything including the alky and nothing changed that spot. The only way to get rid of it is to force it into open loop at that point. I just wonder if this is common on built motors or not.

Thanks!

Jody

 

Jody
I have a dynojet wideband unit on my JDM built/tuned motor. At present it has stock injectors with wilbro pumps. I am running at around the 520 rwhp mark with an Apten ported blower.
I have an 8 pound lower along with the factory stock upper. My wide band records mid 14 a/f numbers driving like you described.
Not much help I know, but some real world info none the less.

 

I appreciate it Hilander. Mine is real happy at 14.6:1 as long as the throttle is light like in normal driving. But if you start to get more aggressive, or tow a trailer like I did a couple weeks ago, then the load changes and it does NOT like to be that lean. By bringing in the open loop sooner so I can command and adjust the maf transfer to be whatever A/F I want it fixes it. I just richen it up to 13.8-14.0 or so and it's happy.

Jody

 

Can't be a dead plug that you don't really feel at WOT?

Just a thought.

 

Do you have a way to watch your Fuel Pressure? For some reason my two 255's did not like running at low voltage or pressure very much at all.