Fuel Tuning.

[Fox Slaughter]

So obviously the more air you can get in and out the more fuel you are going to want to get in also.

My widebands on each bank at idle are reading ~15.4 which is lean to the 14.7. PE mode I was reading adds more fuel based on the LTFTs. Which mine have been above 128. Which is i remember means the PCM is trying to add fuel to compensate for a lean condition.

Now I can't figure out how to tune for fuel exactly. I read that an easy way to do it is to change the Injector Constant. If you move it up the PCM thinks you have bigger injectors which in turn will decrease the time they spray, thus leaning your mixture out, and vice versa.

So in order to get my LTFTs to get closer to 128 (128 = 14.7) I should turn down the injector constant so it thinks they are smaller and would keep the timing open longer getting spraying more fuel in correct?

[shawnc16]

I dont see an issue running lean at idle.

[Fox Slaughter]

Well my LTFT is all out of whack. They are running ~130 on the left bank and ~140 on the right bank.

[1BADAIR]

injector scaling is a set constant. you set it to your injectors. if its incorrect the whole tune will be off.
PE and VE tables are used for fuel

[Fox Slaughter]

Well how would I edit them. I have tunercats but I don't know to increase the values or decrease them.

Fuel Pressure at the rail key on - 42psi
Fuel Pressure at rail key off after 2 mins - 41psi
Fuel Pressure engine running - 41psi

[Fox Slaughter]

I think I got it. The Formula for PE tables is:

PE AFR = 14.7 / (1 + %Change vs Cool / 100 + %Change vs RPM / 100)

So if the Coolant is 68 degrees and you wanna know the AFR at 5200rpm (19.1 Coolant, 9.8 RPM on stock LT1).

• 14.7 / (1 + 19.1 / 100 + 9.8 / 100)
• 14.7 / (1 + .191 + .098)
• 14.7 / (1 + .289)
• 14.7 / 1.289
• 11.4:1

So at 68 degrees coolant temp at 5200 rpm stock it is running a 11.4:1 AFR.

By working backwards you can set your AFR.

• 14.7 / 12.5 = 1.176 (14.7 divided by your desired AFR at 5200rpm)
• 1.176 - 1 = .176 (To remove the 1 you added in)
• .176 - .098 = .078 (Subtract the RPM %Change Number)
• .078 x 100 = 7.8 (Times by 100 to get to the %Change Coolant Number)

So at 68 Degrees RPM of 5200 you if you put in 7.8 you would get a AFR of 12.5:1 in theory.

[1BADAIR]

PE table controls WOT fuel

[Fox Slaughter]

Right. I was just reading a write up about tuning your VE tables.

The guy said you have to enter SD mode then copy the High Octane Spark Table to the Low Octane Spark Table using HPTuners, but I use TunerCats so I have no idea what these tables are haha. Then it will eventually 0 out you're LTFT then you can tune for your STFT then it will be ready to tune for the PE tables. But as I said I don't have HPTuners so I don't know how to enter speed desity mode and then turn the LTFT off so it only uses the STFT.

[Fox Slaughter]

BLMs split like crazy. Just did a log and my right LTFT will hit as high as 150 and go no lower than 135. Left LFTF is between 130 and 140. The mV on the right O2 will go as high as 968mV, low as high 100s.

I put the car into SD mode and the STFT is ~128. LTFT is still way up.

My question is if I reset the BLMs to 128, then keep it in SD mode get some logs then tune the VE table then disable MAF mode will this make my VE tables correct?

Also under MAF I would sometimes see as much as 10 degrees of spark retard. Now that I put it in speed density there wasn't even a hit of knock.

Here is a picture of the crazy lean on right side.

Lean.jpg

[Fox Slaughter]

Well pretty sure is a header gasket leak. The number 4 cylinder has some carbon on the header flange. I reached around when it was running, felt some air moving by the number 4 tube but no where else. So I took a piece of paper towel and stuck it down there, soon as it gets within like a half inch of the header flange it sucks it right to it.

I just put on the gaskets that came with the Pacesetter headers so what gaskets should I get?



Should I run FelPro 1406 gaskets?