Help tuning idle after 102 install

Hello all,

Just recently installed a lpe snout and NW102 on my zr1 and i'm trying to figure out how to get my idle back to the way it was. Car drove, ran, idled great before on the stock tb and had a great lope, but now it's gone. I had to change the tps settings for decel as it wasn't going into decel mode and was still basically cruising even with my foot off the gas. I've been tuning my own stuff for awhile now, but just getting into the hptuners/ls world, much different from the import/tuner world. Any help is appreciated.

Here's my file.

Attachment 69635

did you change the ect area scalar? i don't have the original file to compare so it's a bit hard

just checked with a file i found and it is stock. zou have to change it.

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Originally Posted by avido

just checked with a file i found and it is stock. zou have to change it.

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Yes i did change it to 5750, it helped slightly. Is that correct? I couldn't find a exact scaler for the 102

A 102mm TB scalar s/b like 7300......and can be tough to dial in sometimes.

Ed M

I have a Nick Williams 102mm throttle body. I used the formula for area of a circle less the area of a 10mm throttle shaft.

PI 3.142857143
Bore 102.00
Total Area 8174.571429
Shaft (10mm) 1020.00
Net Area 7154.571429

That's how to get an approximate value for the scalar. I rounded to 7150 and that's the value in my tune file

i have never heard about someone calculating the shaft

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Originally Posted by avido

i have never heard about someone calculating the shaft

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Here is a graphic from our tutorial showing shaft shadowing and why TPS% only hit 83.9% at Wide open based on the blade geometry...

Ed M

I would use 6955.24 for the scalar.

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Originally Posted by mowton

A 102mm TB scalar s/b like 7300......and can be tough to dial in sometimes.

Ed M

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So just change the scaler and i should be good to go?

I had mine set to 7150, but had to raise the min air table to unreasonable values. GHuggins suggested I change it to 7400, which I did. I was able to lower the min air table values considerably, lower than stock. The engine really liked this. No more engine run-on, starts great at all temps, and ramp down is perfect.

I think this post by Greg Bannish is a good one to refer to, seeing how is the "GM calibration guru" afterall.....

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Originally Posted by eficalibrator

Anything over about 82 degrees of rotation is basically WOT since the blade is "shadowed" by the shaft when view from the entry. Rotating any further doesn't really open up any more significant airflow area or reduce the pressure drop any more, so there's no real benefit to going all the way to 90*.

That said, you still effectively get 100% area opening at either 82, 83, or 88 degrees; which should equal roughly the area of the bore minus the area of the shaft. The PCM uses this maximum as a reference from which it will reduce down toward zero (in a nonlinear fashion, determined by another table you don't see) as it controls idle airflow.

Obviously, larger starting areas will need a smaller % of that area to get the same desired effective area at idle for normal operation. This is why adjusting the area scalar is so important if you change the ETC module and want normal drivability and idle control.

Going from 90mm up to 102, I'd first solve for the ratio of areas (with an ASSumed 10mm shaft):

90mm = (pi*45*45)-(10*90) = 5458.5
102mm = (pi*51*51)-(10*102) = 7147.1

Ratio = 1.30936

Multiply this by the reference scalar and I get : (5636*1.30936) = ~7380

Any smaller errors from here will just get baked into the RAF adjustments or idle airflow PID corrections. This of course ASSumes that you've nailed both the MAF and VE (or Virtual VE, as it were) airflow models and ignition timing before adjusting target idle airflows.

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More info in the thread where Greg made that post, including the shawow area Ed mentioned.

https://www.hptuners.com/forum/showt...TC-area-scalar

Thanks!


P.s. I bought your course. 👍

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Originally Posted by supraslow92

So just change the scaler and i should be good to go?

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Read the second part :-)...some go good, some go tough. The scalar will align the idle mm2 results to TPS% conversion to operate the blade at a the correct rate for the TB size..

Ed M

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Originally Posted by avido

Thanks!


P.s. I bought your course. 

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Thank you.....let us know what you think....

Ed M

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Originally Posted by mowton

Read the second part :-)...some go good, some go tough. The scalar will align the idle mm2 results to TPS% conversion to operate the blade at a the correct rate for the TB size..

Ed M

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okay i'm stuck, i've tried messing with the final airflow idle tables, min etc

Any ideas what else to try?

What's it doing and post a log illustrating this along with the latest tune - should help everyone.

Here's a few logs from things i've tried. I tried raising the ETC scaler to 8000 like NW recommends for the TB, might have helped slightly. The car will idle fine at 850, i just can't get it to lope like it did :(

Here's a few logs.

In one i tried lowing the final airflow by 50%
2nd i turned off the integral and porportional adjustments just to see what it did, idled around 1100 and was pulling timing
lastly i made the spark over and underspeed values more aggressive after reading that can help lope.