Setup tips for 90mm TB needed!

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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

Quote:

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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?