B4349 Scaler for LS2 TB upgrade (Real FACTS)

[kwhiteside]

Obviously, I've bored most of you. I'm thinking now that if you start with a rock solid tune to begin with, you most likely wont have to make any changes to the scaler. A couple months ago when I slapped the FAST onto my engine with a jacked up tune, I could not stop my car from stalling out every now and then. Now I can change the scaler either way and my car idles really well regardless.

That said, and without much input from others, I picked the .0191 setting and have finished AutoVE and started on AutoMAF. While my tune is shaping up very quick, in the back of my mind I have noticed two things now that suggest I may have chose the wrong path.

First symptom - the .0320 tune ran .5 richer at idle. This indicates that scaling to a greater value, adusts the throttle blade to let less air in.

Second symptom - My first AutoMAF run found my MAF reading too much air for the initial opening steps to the throttle.

I'm thinking I can go back to my 0320 tune and setup for AutoMAF, do a log run, and see if those early steps are less lean. If that turns out to be the case, it seems to me to prove that the .0320 scaler setting actually adjusts the LS2 Throttle body to let less air in.

Keep in mind the whole point of the exercise is to take your new bigger 90mm throttle body and prevent it from letting massive air into the mixture so your car will idle properly. Then those step setting should also carry through wide open throttle to be more correct.

[kwhiteside]

Tested the 0320 setting in AutoMAF mode with two log runs, and it ran even leaner. I also had a noticable surge or hunt at stops and could see my AFR gauge move back and forth in rythm to the hunting. Sure didn't like that. Wish I could have shown something indusputively conclusive.

I'm going to move on with my .0191 setting.

[joecar]

I'm not bored... I just don't know enough... I read your posts, and I would agree that the 0.0191 seems to be the more correct one (for want of better terminology).

[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.

[mr.prick]

Besides the spreadsheet and (X/Y)*X = {B4349} someone has posted a method for this:
What you have to do is simple

The real question is why is this a sticky?

[joecar]

Just so I can track it for a few days... he posted some real data for us to look at.

[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?

[kwhiteside]

Huh? You're doing idle at highway speeds?

Ok, you taunt me with that one. I tested the 0320 idle stuff on the way to the gym, and on the way back today. Mabye 10 stoplights each way.

Most of my log runs take 7 minutes to get to clear highway with many lights (idle stuff). Yes we are talking about idle, but I'm still tuning. To me, tuning is for when I go to the track and hit redline in 4'th gear of 140mph. Now I don't go that fast of course during my log runs, but I do get the 90-105 cells kicking in. I use both 3rd gear redline and some quick 4th gear floor board up to speed, then break to get down from go to jail speed. Actually similar to what happens at the track. Floor it, then get ready for a turn. Oh, and each run also includes a drag strip run as there are some nicely isolated on ramps that allow you to go full out 1st thru 4'th without drawing attention. Of course no other cars around me during testing.

The only time idle even matters at the track is when cruising thru the paddock. Having your car die there amongst all the 250k Ferraris and Vipers would be like doing bench press at the gym and getting stuck on your chest, then having the throw the weights off to one side so everybody in the gym gets a good laugh. (Don't try too many reps at 285 without a spotter )

[monzaaddict]

{B4349} ETC THROTTLE AREA CONVERSION (% per square mm)

Newbie here. After looking at this for most of the night it dawned on me that the reason redhardsupra's chart perfectly calculates the correct value for a truck throttle body and not the F/Y body throttle body is because the F/Y body throttle body in addition to the throttle blade has that bypass passage (this passage is not present on the truck throttle body). The fudge factor in the F/Y body tune is to account for the bypassed air.