Correcting lean condition at spool up ?

[Lil Truck]

Julio,

My alkycontrol has been working great, I have been tuning for the past 6 months street and strip learning the do's and dont's. One concern I have had is a lean condition That occurs during spool up, I have attached a data log of a rolling start run you will see a 13.2-13.4 AFR as boost is building. No knock but it just concerns me that the 12. AFR does not hold during this time. I have seen lean conditions on burn outs also.

I tried turning the gain from 11.30 to 12 and 9.30 to 10 on the activation. (Main blue knob at 6) Nothing seemed to change. The data log is with these changes.

The next morning I took the car out to wash it was a cooler outdoor temp (75deg) than the data log run the day before. When I left the car wash I went to dry the car off at 15 psi all was good, when I went full throttle it backfired through the intake 2 attempts. No data log.

I went home turned down the gain knobs and went for a test run, all was good again. I did not wash the engine bay, and I have made the same run before after washing with out this happening. To much Alky at low temp ? I run 100% Meth.

Guess I have 2 questions here,

1. Should I try to correct the lean condition?
2. Cause of the Intake backfire?

I am running a TT6.1 chip All wide band control is set to 10.8 AFR including the mid boost setting.
Stock MAF, 55lb Injectors, XP pump, Hot wire, 91 & 100% meth.

Thanks

 

[KEVINS]

If the car backfired after the car wash the engine may have been too cold. I've had this happen at the track after cooling the car down to much.
I'll also add that I don't hink you're supposed to cure the fueling with the alchy, you do this with the fueling in the chip. The alchy is used to help eliminate detonation not to cure lean conditions.

I'm no expert so if I'm wrong someone will correct te above statements.

ks

 

[Lil Truck]

Thanks, I was curious if anyone else had experienced a intake backfire with cool conditions. I understand about the fueling, but I have no adjustment in that range. I was just trying to find out if I am the only one who has this AFR during boost ramp up of if it is normal ? I have had KR during burnouts due to this condition.

 

[Eric Stage I]

That A/F looks pretty typical to me. The boost is only in the 3 to 6psi range, so it can be leaner. I would not relate that to the alky system as it would barely be on at that point.
Not sure on the backfire. If it was cooler out, maybe it was overboosting and momentarily leaning out. Or maybe a freak thing from the carwash.

 

[Lil Truck]

Thanks Eric, I appreciate your input!

 

[murphster]

For the backfire, my first guess is the stock MAF. Could be getting lazy. The logs don't look like you are getting too rich with the extra alky for that to cause it. But adjusting the "initial" knob inside the PAC box does make big changes to how fast the alky comes in. If the alky was already primed it could be too rich if it spooled fast and too much alky came in.

One comment from the log with that lean condition at the lower boost...... My guess is that when the A/F dropped is when the alky came in. If it isn't primed there is a pretty good delay before all the pressure builds up. Looks like the boost came in pretty slow so it wasn't a big deal. But that can be disaster on the highway if you punch it from a roll and the boost builds up quickly but the alky isn't there. Plus if you keep the timing delay in on WOT that gives you a little safety margin also. It's just a guess, but logging the alky pressure would tell you for sure.

 

[larrym]

I had some interesting misfires after detailing my engine should have but a bag over the coil pack and module.......

Any chance you got the coil pack and module wet?

 

[Lil Truck]

The hood was shut and the seal is in place, it was a hand wash. There is always a possibility, I did not notice any water when I made adjustments. I believe the engine was just to cool for the amount of Alky. I made a test run last night, the first run the engine was cool and I could feel some mild surging. I made a second run 5 min after and there was no surging. I use to run on the 5 setting without a problem, but after reading the information on this site about keeping the gain knob at 6 or higher for reliable pump activation I have been keeping it at 6.

 

[murphster]

I've run in 50 degree weather many times with the gain knob practically maxed on a dual nozzle. I don't think that is the problem.

 

[Lil Truck]

Thanks for the information, I have been concerned about low temp operation.

 

[Lil Truck]

For the backfire, my first guess is the stock MAF. Could be getting lazy. The logs don't look like you are getting too rich with the extra alky for that to cause it. But adjusting the "initial" knob inside the PAC box does make big changes to how fast the alky comes in. If the alky was already primed it could be too rich if it spooled fast and too much alky came in.

One comment from the log with that lean condition at the lower boost...... My guess is that when the A/F dropped is when the alky came in. If it isn't primed there is a pretty good delay before all the pressure builds up. Looks like the boost came in pretty slow so it wasn't a big deal. But that can be disaster on the highway if you punch it from a roll and the boost builds up quickly but the alky isn't there. Plus if you keep the timing delay in on WOT that gives you a little safety margin also. It's just a guess, but logging the alky pressure would tell you for sure.

I have a New MAF to test with later this week. I appreciate the input you have provided it sure helps. The system was primed before the test run the had the backfire. The strange thing is I had a mild back fire about two weeks earlier the car was cool, first run when it was in 3rd about 2 seconds I heard a pop. I got out of it, nothing shows on the data log that looked abnormal. KR, MAP, MAF, DC ?? I made a run a few minutes later and everything was fine? I was expecting to see a spike on the MAP sensor?

 

[Eric Stage I]

Usually, when I run into popping, it ends up being an ignition problem, or cam sensor.

 

[Lil Truck]

Thanks Eric, any tell tale signs on the power logger to look for?

 

[Razor]

Another thing that throws the engine off is that when the engine is cold, there is extra enrichment(added fuel) until it warms up. So look at the coolant temp and make sure its always above 160+. Your results can get sketchy when racing an engine still in warm up mode.

When I fist got a FAST, it was on enrichment until 180 degree's. What a screwy tune that was.

I vote bad maf/ignition module for back fires.

 

[Lil Truck]

Thanks Julio, it is reassuring to have your input!

 

[haywire4130]

Out of curiosity, are you running an electronic fuel pressure gauge? Im having a similar issue that i think is due to "42 psi" on my electronic.gauge is not quite 42. I havent had a chance to locate a mechanical gauge to confirm readings. Just a thought-

 

[haywire4130]

Out of curiosity, are you running an electronic fuel pressure gauge? Im having a similar issue that i think is due to "42 psi" on my electronic.gauge is not quite 42. I havent had a chance to locate a mechanical gauge to confirm readings. Just a thought-

 

[haywire4130]

Out of curiosity, are you running an electronic fuel pressure gauge? Im having a similar issue that i think is due to "42 psi" on my electronic.gauge is not quite 42. I havent had a chance to locate a mechanical gauge to confirm readings. Just a thought-

 

[haywire4130]

Sorry for the quadruple post, i have no idea how to undo it... Lousy "4g"!

 

[Lil Truck]

I Have checked my FP with a mechnical guage, it is working fine. set @ 44 runs 1lb per psi. I have new IG mod, coil pak and MAF to test later this week. The intake back fire only occurred 2 times, but the mild surging under full is more frequent. I hope one of these will fix the problem.