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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.
I heard about the issues with the TBs not going 100% open. Can't say that I have experienced that at all.Quote:
Originally Posted by DrX
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??
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.Quote:
Originally Posted by Redline Motorsports
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?