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."

[redhardsupra]

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

The fact that the same size TB's generate a completely different effective area estimates to me signifies that GM is either fudging this one, or they're accounting for something else with it. Obviously in fbodies the area somehow has to be correlated to the airflow, and that must get translated to IAC steps. In Vettes you gotta convert the effective area to the angle of the TB to keep the engine going with enough airflow.

To my knowledge, noone ever fully described the process of airflow estimation at idle in general, effective area <-> IAC steps/ETC angle transformations in particular.

What Jeff described in the post you linked to makes no sense whatsoever. Division of the fudge number by the ratio (not difference, difference is a minus) of areas would suggest that he was attempting to scale the fudge value, assuming that whatever fudge that number carried is heteroskedastic. We dont know that, as we dont know what are they're fudging for. Also if he wanted to scale it, he should've been multiplying it not dividing it. Mathematically failing to do bad science is pretty much why I haven't agreed to anything that Jeff proposed in the last 5yrs on the boards

If the fudge value is to account for the area that's obscured by the TB at different angles, then it's definitely not linearly scalable as Jeff would have you believe.

I dont think we should be looking at the scalar alone, I think we need to figure out how that scalar gets converted to the desired airflow. The full idle airflow model would be hugely beneficial as well, because we know all RAF, MAF, and Dynamic Airflow all play a role, but how, when, and to what extent they kick in is a mystery.

Also, idle is usually short pulse territory. This means that WB readings, and injector data can be screwing with you in a big way, so you attributing it to some TB scalars might be completely wrong.

[kwhiteside]

read ... read... heteroskedastic
read ... read...
big mystery

Got a little chuckle from me as I read that.

You know I've only been doing this for 2 months, and I know you've been doing it for many years, so I'm in no way trying to discount anything you've said. Keep in mind that us new guys get frustruted when we do use the search button and find experts pulling us in opposite directions.

Two months ago when I started with my FAST and then began tuning for the first time, I wanted to pull my hair out. The car's rpm's would divebomb and die and I tried everything, inlcluding idle tuning and throttle cracker stuff. I finally bailed on the FASt and went back to stock, started the tune over and got it right on. Then I took the car to the track and missed the extra ponies. Gotta try again. Now it is going very smooth. Smooth with the exception of what I reported today with the .0320 tune and the AutoMAF process. The car started surging / hunting at idle. I could literally see my AFR gauge sweep back between 13 and 16 AFR. I started to have flashbacks of the days were I couldn't get the car to idle right. I was hoping to prove it technically, but am not sure I know enough about deciphering my logs to do that. Real World Seat of Pants test, I'll stay away from that hunting idle for sure. Technically, the lower settings made most sense to me, that is why I went that way on my own. Perhaps you .0157 value is even better than the .0191. I showed how I got my .0191 value with your spreadsheet. I suppose it is quite heteroskedastic and yes it just repeats the GM fudge. I don't know if your value is even better, I didn't test it as I ran out of energy doing my log runs. Can't do that on public highways for ever without incurring a big cost eventually.

Ken . . .

[redhardsupra]

read ... read... heteroskedastic
read ... read...
big mystery

Got a little chuckle from me as I read that.

You know I've only been doing this for 2 months, and I know you've been doing it for many years, so I'm in no way trying to discount anything you've said. Keep in mind that us new guys get frustruted when we do use the search button and find experts pulling us in opposite directions.

Try 5 years, see how that fuels your frustration we seriously knew about the same amount about idle mechanisms then as we know now.

Two months ago when I started with my FAST and then began tuning for the first time, I wanted to pull my hair out. The car's rpm's would divebomb and die and I tried everything, inlcluding idle tuning and throttle cracker stuff.

Heh, I tune that with RAF, idle spark, and the TB scalar you didn't like. Rarely do I need anything more than that. Remember that Fuel, Air, Spark are the big villains, the rest are merely minions and henchmen.

I finally bailed on the FASt and went back to stock, started the tune over and got it right on. Then I took the car to the track and missed the extra ponies. Gotta try again. Now it is going very smooth. Smooth with the exception of what I reported today with the .0320 tune and the AutoMAF process.The car started surging / hunting at idle.

Too much fuel, seriously that's the correct diagnosis like 99% of the time.

I could literally see my AFR gauge sweep back between 13 and 16 AFR. I started to have flashbacks of the days were I couldn't get the car to idle right. I was hoping to prove it technically, but am not sure I know enough about deciphering my logs to do that.

Practice makes perfect, and you're absolutely right, reading logs is the way to tuning, not arbitrarily making changes to the tune <HINT HINT>

Real World Seat of Pants test, I'll stay away from that hunting idle for sure. Technically, the lower settings made most sense to me, that is why I went that way on my own. Perhaps you .0157 value is even better than the .0191. I showed how I got my .0191 value with your spreadsheet. I suppose it is quite heteroskedastic and yes it just repeats the GM fudge. I don't know if your value is even better, I didn't test it as I ran out of energy doing my log runs. Can't do that on public highways for ever without incurring a big cost eventually.

Ken . . .

Huh? You're doing idle at highway speeds?