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Old 05-28-2012, 05:48 PM   #1
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Default Light throttle stalling/stumbling

I'm having an issue with my car on light throttle that at 1-2 % throttle it gets leaner and leaner until it catches itself and starts to rev. It feels like it's about to stall when it's doing this and it also occurs when you've backed off the throttle for a mo making it impossible to re-apply smoothly.

I've attached my logs and tune, any ideas what's causing this?
Attached Files
File Type: msq Dodgy light throttle.msq (84.2 KB, 65 views)
File Type: msl light throttle.msl (163.3 KB, 102 views)
File Type: msl light step 2.msl (85.7 KB, 63 views)
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Old 05-28-2012, 06:16 PM   #2
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What is your setup?

What are your mods? List them all.

-Raj
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Old 05-28-2012, 06:40 PM   #3
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It's a 96 1.8 with an m45 supercharger running about 8psi. I've got dual throttles and an intercooler with 440cc black top supra injectors. I've added some resistors to my ecu for these. Ecu's a DIYPNP running m2extra 311 mb_v12. Lc-1 wideband

I've removed all the pipework from the intake throttle body to get rid of any issues with the intercooler and extra throttle and the car behaves the same way.
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Old 05-28-2012, 07:13 PM   #4
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I have similar issue due to my injector's non-linear region characteristics.

I can't look at your msq or log right now.
Are you running sequential fueling or batch?

-Raj
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Old 05-28-2012, 07:17 PM   #5
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Batch injection.

I've also asked this in msextra and had a reply about my AE settings. Could be a cause as I don't see any AE being used in my logs
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Old 05-29-2012, 12:07 PM   #6
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looks like a tune issue, probably AE and the fuel map without looking at the tune file.
Doesn't help that you are running low imp injectors on resistors either.

redrider then I suggest you make sure you have proper injector settings for the injectors you are using. It will the worlds of difference in the tune and everything else falls into place for tuning.
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Old 05-29-2012, 12:27 PM   #7
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do you not have a vtps?

try reducing your Accel Enrichment MAPdot threshold* (~60) a bit and increasing the pw adder enrichments on low kPa/sec rates.


*turn the MAPdot gauge on in your virtual dashboard and find a value that above the value you see at idle and/or at WOT.


EDIT: your logs suggest you have a vtps. You need to switch from MAPdot enrichments to TPSdot enrichments and tune the damn enrichments STAT!

http://www.msextra.com/doc/ms2extra/...ual.html#accel
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Old 05-29-2012, 02:47 PM   #8
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Just gone back to the DIY auto tune defaults for AE and the car's so much better now. TPS threshold is now 20% and it still stumbles a bit on light throttle but it's not trying to die on me anymore.

A good read and some fine tuning should sort that out.

Cheers for pointing me in the right direction guys
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Old 05-29-2012, 02:59 PM   #9
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tps threshold is going to end up being too low for MSI, and you'll start tripping accel events at idle and WOT and you won't like the results.

But go ahead and add more pw adder where needed to prevent the lean spikes, then you can say you've actually tuned a car and can feel good about yourself.
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Old 05-29-2012, 03:02 PM   #10
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Any pointers on what a good setting would be?

I've tuned the fuel table myself. Well i clicked start autotune so that counts right?
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Old 05-29-2012, 03:06 PM   #11
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stab throttle. watch green dot. add fuel if too lean.

it's not hard.
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