B4349 Scaler for LS2 TB upgrade (Real FACTS)

[kwhiteside]

There are lots of guys upgrading thier LS1/LS6 Engines with the FAST Intakes and LS2 TB (or similar). If you've searched for what adjustments to make you will be scratching your head because about half the people have convincing technical arguments with spreadsheets that the scaler number needs to go down.

theory here is when you go from 78mm TB to a 90mm TB, original setting on a C5 Corvette is .0255 for B4349 and it should be reduced to .0191.

There are equally as many guys doing real live tunes saying an increase to .0320 is the only way to go.

My story is that I started with a Z06 with headers, FAST92, LS2, and a jacked up tune I inherited, then began my EFILive learning experience. After a while, I ripped the intake and TB off and went back to stock. I worked by tune in shape and proved it at Road Atlanta doing over 50 laps hitting high speed red lines over and over. I did notice my car was slower without the extra air from the FAST and LS2 TB, so I'm going for it all over again. This time I know for sure my base tune was great. Idle was great too.

So what to do with the B4349 TB area scaler?

Since one of the above theories is going the wrong way, wouldn't it be pretty noticable if you applied both settings and did some logging? That's exactly what I did today. I'm going to repeat tomorrow because my wideband must have come unplugged and didn't log. Regardless, I'll share a couple points from todays logs that stuck out.

The logs will have _0191_ or _0320 in the name and the only difference between the tunes they run on will be the setting for B4349. I've done everything in the AutoVE tutorial so no MAF, no Fueltrims, open loop speed density.

Notice the difference in the MAF Grams/s being logged with everything else being nearly the same. I believe the .0320 tune is reporting much lower then it should be. Also note the .0320 intruduces some severe Knock Retard. I also noticed the .0320 tune dropped below 700rpm many times. Nothing close to stall at this point, I'm guessing because my base tune was solid.

This is preliminary as I will repeat tomorrow, but at this point, .0191 seems to be the correct value.

If you want me to log some other pid and look for something specific, feel free to make suggestions.

Ken . . .