Setup tips for 90mm TB needed!

Still trying to better grasp the parameters that need to be tweaked to get the PCM to accept the increase from 75 to 90mm. The application is based upon an F-body (non ETC). B4349 is in the file but looks geared for the ETC cars. I read some old posts regarding this and there seems to be some conflicts as to which direction to adjust this and not sure if it even effects the non ETC cars.

Does 4350 have any impact?

I would think that manually getting the throttle blade where it gets enough air in the motor and still keep IAC counts between 60-80 would be ideal.

I guess while we are on the subject we mind as well discuss the ETC cars as well. :master:

Howard

Honestly Howard, I don't do anything different and have never had an issue. I just adjust it so the steps are in that range and go on with the tune. I haven't had a problem on any Fbody.

I put a LS2/Fast on C5 and did not change anything from Shaner/LS6. I hated the FAST intake for fit issues but it idled and ran fine.

I agree that the F-body should not be as much as an issue as the ETC C5. I have been having some issues with high and hanging idle with just the switch alone from stock to a 90mm. What about all the conversation about effective throttle area??

Seems to me with the larger opening and that the throttle blade has to replace the IAC function, that more would be needed to let the PCM know the size difference.

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Originally Posted by Redline Motorsports

I agree that the F-body should not be as much as an issue as the ETC C5. I have been having some issues with high and hanging idle with just the switch alone from stock to a 90mm. What about all the conversation about effective throttle area??

Seems to me with the larger opening and that the throttle blade has to replace the IAC function, that more would be needed to let the PCM know the size difference.

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Lean idle surge?
In the end if you are getting more air than before you will change your LTFTs a bit and lean your AFR. Which you fix with your choice of methods.

Bottom line as I understand is to reduce your desired airflow to reflect less iac counts due to extra flow around larger throttle blade.
Some move their iac effictive area, but that shouldnt be necessary. Just log the RAFPN and RAFN logging & adjusting etc.

Can we talk a bit about the ETC cars?? I know it gets a bit more touchy with the ETC TB's. Do you have to play with the effective area? That parameter seems to be debated in many posts.

I have a 02 C5' to tune tomorrow and I would like to try some new tricks. Its a header, 90 mm setup, stock cam.

I just put a FAST 90/GM 90 TB on a 410ci from a truck intake. I'd be interested in anything you guys can provide.

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Originally Posted by Redline Motorsports

Can we talk a bit about the ETC cars?? I know it gets a bit more touchy with the ETC TB's. Do you have to play with the effective area? That parameter seems to be debated in many posts.

I have a 02 C5' to tune tomorrow and I would like to try some new tricks. Its a header, 90 mm setup, stock cam.

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Shouldn't really need to do too much to it Howard. Just get the VE in line and the rest should be cake.

Shouldn't need to change the IACEA unless you change the physical size of the IAC passage or IAC motor.

What I have done that seems to help ETC on my C5 is to change B4349 ETC Throttle Area Conversion to .0320 from .0255. This brought my IAC Steps down to 50-60 at idle, smoothed my idle, and also improved throttle transitions. I played with it a bit before I ended up at .0320. I have to agree though that the single best change I made that helped everywhere in my tune was getting my VE table set up correctly first.

I am not sure how much time I want to spend with this car as I will installed was a set of LT headers and the intake. I'll try the stock parameters and see what happens. Now that I think about it we just removed a BBK TB and intake and replaced it with a FAST 90 and TPIS 90mm TB. It never had any issues with that setup..

In most cases, adjusting effective area will solve any idle problems resulting from a throttle body change. I think the point that a lot of people miss with ETC cars is that since idle air is controlled by throttle position, an increase in throttle bore diameter means that more air will be admitted for a given throttle position. If you don't change the effective area, the PCM thinks it's controlling air flow through a 78mm throttle body, when in fact, it's controlling it through a 90mm throttle body. Consequently, it can't get things right because it's making changes based on incorrect data. It's kind of the same premise that politicians work under.

Only initial change I made when I did the conversion was effective throttle area. Doesn't look like anything else should be touched. I had someone with HPT look at a LS2 tune and it is a totally different setup. Throttle Area Scalar Value is 4725! Not sure of the units.

At least you are working with an 02. Apparently, the 02 TAC module/02 PCM combo seems to be the only one that works properly with the 90mm ETC TB. There are still unresolved correlation issues with other PCMs. I am seeing a max physical throttle opening of around 85% and some idle tuning issues.

I ended up reducing the desired airflow in PN and gear and it cleaned up pretty good. I went to take it for a drive and it popped a 1514 so I raised the predicted airflow table up to get rid of it. When it starts it flares up a bit so we took more out of the DAF. The only issue I have is that it "cruise controls" a bit while driving.

I agree in that the larger diameter has to be compensated as quite a bit more air must pass around the bore in a 90mm vs. a 78.

I experienced "cruise effect" with higher throttle area conversion values.

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Originally Posted by DrX

At least you are working with an 02. Apparently, the 02 TAC module/02 PCM combo seems to be the only one that works properly with the 90mm ETC TB. There are still unresolved correlation issues with other PCMs. I am seeing a max physical throttle opening of around 85% and some idle tuning issues.

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I heard about the issues with the TBs not going 100% open. Can't say that I have experienced that at all.

Isn't there a table that remaps the throttle opening percentage?? I thought it was a red tabbed folder in Live that is only present when the software is hooked to the car.....

Also when going from a 78mm to a 90mm; the effective throttle area; we assume that GM's base value is mathematically correct. If you just figure out the percentage of difference between the 78 to the 90, can't you just multiply that value to make the change? It should be that simple....no??

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Originally Posted by Redline Motorsports

Isn't there a table that remaps the throttle opening percentage?? I thought it was a red tabbed folder in Live that is only present when the software is hooked to the car.....

Also when going from a 78mm to a 90mm; the effective throttle area; we assume that GM's base value is mathematically correct. If you just figure out the percentage of difference between the 78 to the 90, can't you just multiply that value to make the change? It should be that simple....no??

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For that table to help you would have to be able to command greater than 100% TP. The 90mm TB has a slightly wider TP sensor voltage range than the 78mm. So the TAC module/PCM see a value that equates to 100% TP on a 78mm before that is actually attained with the 90mm. A similar thing could be happening at the other end of the TB's range of movement resulting in idle issues.

Yes, the relative throttle area caculation makes sense. I wouldn't expect that any changes to required airflow values, etc would be necessary if the TB was the only change being made. It's not so simple for those of us with the TP correlation/communication issues though. Supposedly, a solution is still under investigation.

How do you properly calculate the effective area when going to the 90 from the 78?

So you think that just by changing this alone and no DAF changes can get these cars to idle? How cool would that be!

Howard

When do you play with the airflow park?

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Originally Posted by Redline Motorsports

How do you properly calculate the effective area when going to the 90 from the 78?

So you think that just by changing this alone and no DAF changes can get these cars to idle? How cool would that be!

Howard

When do you play with the airflow park?

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This has been discussed before but here's how I think it should work anyway:

Cross sectional area of 78mm= 4776 sq mm
Cross sectional area of 90mm= 6359 sq mm

Units for B4349 are %/sq mm

100%/4776sq mm= .0209 %/sq mm for the 78mm TB
(my factory tune had a value of .02077)

100%/6359sq mm= .0157 %/sq mm for the 90mm TB

Airflow requirements of the engine haven't changed if the TB was the only mod, right? So I think B4349 should take care of it for ETC vehicles. If there are other mods, then I assume that you would still have to tune AF accordingly for them once B4349 is correct. If B4349 is off it is likely going to make idle tuning difficult.

We'll tonight I did some cold startup tuning with this 02' A4 C5. I originally decreased the DAF from 133-200 degrees F. I still had a high reving cold start. I changed the B4349 to the values you calculated and holy crap it fixed the problem!:cheers:

The car starts and idles like stock!!!

It seemed real good and I left the DAF values as is. Maybe I should have changed them back to stock but all seemed good.

Not for nothing but that parameter works!!! Thanks for the lesson!

Howard

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Originally Posted by Redline Motorsports

We'll tonight I did some cold startup tuning with this 02' A4 C5. I originally decreased the DAF from 133-200 degrees F. I still had a high reving cold start. I changed the B4349 to the values you calculated and holy crap it fixed the problem!:cheers:

The car starts and idles like stock!!!

It seemed real good and I left the DAF values as is. Maybe I should have changed them back to stock but all seemed good.

Not for nothing but that parameter works!!! Thanks for the lesson!

Howard

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Glad that worked.

Now if only someone could get the 90mm TB electronics working properly with the 03 and up PCMs!

What do you mean about the 03's? This won't work past O2?

Why not?

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Originally Posted by Redline Motorsports

What do you mean about the 03's? This won't work past O2?

Why not?

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Apparently, the only one(s) that claim to achieve 100% physical throttle opening with the LS2 90mm swap are those with 02 PCMs. Even though the 02 TAC module is also installed as part of the swap. With my LS2 TB, 02 TAC module and 04 PCM I am only seeing about 85% physical opening when 100% TP is commanded. I believe the correlation is off at the closed end also(affecting idle tuning).

The TP sensors of the LS2 TB operate on a slightly different voltage range than those of the 78mm. The LS2 sensor output at 85% TP is equivalent to that of the 78mm at 100% TP. I don't know how only the 02 PCM adapts to this. I do know that the stock TP sensors on my 04 both move in the same direction(voltage increases as TB opens), while the LS2 TB's sensors move in opposite directions. Hence the need for the swap to the 02 TAC module which operates similarly to the LS2s. Although the TAC is built into the PCM on the LS2s.

Dr,
I was looking at some of my old logs from my FAST/LS2 days and I was at least logging 100%. This, with just a cable splice from my 2K and LS6/Shaner setup?
Bruce

Does this apply to a aftermarket 90mm as well as OEM LS2 TB? I don't see why it should matter as long as the PCM knows the area changed and that the throttle blade still follows the same angle of opening. No??

I am only referring to ETC vehicles with the LS2 90mm swapped in to replace a stock 78mm. This is not relevant to cable actuated TBs. As far as I know this issue has only been seen on 03 - 05 vehicles. 06 doesn't work at all with the swap. The swap may work OK on earlier vehicles. I have seen pics of a 02 TAC/PCM setup where the TB was fully open. Logs will look OK (i.e logged TP will match commanded as per the pedal position/TP table) but if you actually take a look at the TB it will not be at 100% physical opening.

This is what I see happening. Let's say that sensor1 on a 78mm TB puts out 3.8V at WOT while sensor1 on the LS2 TB puts out 4.2V at WOT. Because the setup was engineered to expect 3.8V at WOT it will not actuate the throttle blade beyond that point. So the LS2 will never achieve full opening. Because this is programmed into the TAC module rather than the PCM we have no way of addressing it with EFILive.

There may also be some difference in the way that the throttle actuator motor is driven by the PCM(both use pulse width modulation). Someone would have to compare a stock 78mm setup to a stock LS2 setup, looking at the PWs at WOT.

yes i realize holy old thread batman...but i have a 02 C5Z06...with the LS2 90mm just put in .0157 in my ETC conversion and reraf'ed...my car needs like 16 grams fully warmed up in the desired table....anyone elses tune i look at is frickin 9 grams lower...what gives....and any truth after 3 years of this dead thread to the ls2tbody not opening 100 percent on my car?