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 . . .

[joecar]

Ken, very interesting, thanks for the info...

[redhardsupra]

all you need:
http://www.marcintology.com/tuning/TBresizing.xls

[kwhiteside]

Red, I pm'd you earlier about this ss.

Seems it is very misleading for corvette owners.

The default setting for LS1/LS6 78mm TB is .0255. The spreadsheet has a very different value. I found a multiplier to make it correct, and then used that on the 90mm cell.

This is how I came up with .0191. I used your spreasheet as shown below. Also some other tuners said they ended up using .019 which was a good confirmation.

That spreadsheet should probably either be updated or at least explained that the settings do not start with the corvette / camaro settings. Somebody said it may be correct for trucks using LS1/LS6??

[redhardsupra]

Could you explain the 'I found the multiplier' part? How did you do it?

The reason for the discrepancy is that I calculated the area purely from geometry. In reality you got some metal in the way, which makes the effective area slightly smaller. The general approach however is I'm fairly convinced correct, as I've used it on non-circular TB's by altering the formula for the area according to the desired shape.

I've never encountered any problems with the values generated by this spreadsheet, neither have anyone raised any questions/issues with. If you have any solid evidence pointing toward something new, please let me know, I'd be more than happy to alter the spreadsheet and give you credit for it.

[kwhiteside]

Could you explain the 'I found the multiplier' part? How did you do it?

Well, start with the stock corvette LS1/LS6 tune for 78mm TB. Right off there is the problem. Value is .0255 not .020928

In one of the original threads somebody explained the formula problem, but I wasn't getting that technical.

I took .0255 / .020928 and got 1.218482 multiplier. I then moved down to the 90mm cell and multiplied .015719 * 1.218482 to get the new value of .019153.

I think your approach seems to be correct. But if you are looking specifically at values to change B4349, shouldn't you at least start with a formula that matches. 78mm is .0255 according to B4349, not .020928.

Highlander was the one who also suggested .019 which matches your ss if starting from the correct point.

This is the original thread where my same point is brought out
http://forum.efilive.com/showthread....ght=b4349+90mm

That said, out of respect for you, knowing that you have lead a lot of the current understanding, I will add a third tune with .0157 to run my logging with tomorrow and see how it reacts. I would like you to try to make me understand why GM puts .0255 into b4349 when you calculate .0209 in you computations. You must admit, something is missing there since it is the values of b4349 we are adjusting. How did gm come up with .0255?

[kwhiteside]

Bruce Melton quote
"From the repository it looks like most stock Camaros and Corvettes are .0255 and trucks are .0208."

[kwhiteside]

and this says it better than I did.

http://forum.efilive.com/showpost.ph...0&postcount=16

[kwhiteside]

I've done two runs with my wideband working again. After analyzing these side by side looking for the "Right One", I've come to realize a few things. I start looking for my strong pulls at full throttle. I'm thinking which one give me better power. Neither With either the .0191 or .0320 setting, at full throttle they are almost always identical. Hmmm, why would that be? Because the blade is full open. What we are messing with here is how much air the TB is letting in at each step or increment of the blade opening. This is why people start fussing with this setting when they have idle problems. My car seems to be idling fine with either setting and the only difference I can make sense of is that the .0320 tune runs .5 richer at idle. But then there is the 20 degree difference in temperature that may account for some of that.

My head is hurting and I'm not sure what to make of it at this point. I'll upload a couple screenshots, my tunes, and my logs in case any of you think it is worthy to figure out.

[kwhiteside]

Here's a full throttle 4th gear pull showing that things are almost identical.