Getting WOT throttle-on lean spike HELP!

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ion332
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Getting WOT throttle-on lean spike HELP!

Post by ion332 »

I get a throttle on lean spike of up to 16 AFR... It only happens if I slam the gas pedal. If I get into it somewhat smoothly it won't happen.

I have tried both TPSdot and MAPdot triggered accel, I have also tried increaseing the lower threshold accel fuel values and to no avail.

I have a very free flowing engine, throttle response is almost immediate..

Now, I might be throwing up an alarm for nothing, but, with the tuning on this motor getting so tight I would like to try to remedy this issue before it ends in a burnt piston ring. All the other settings are perfect and nail 13 AFR across the whole spectrum of driving conditions, its only right at a fast throttle on this 16 AFR spike hits, then the fuel goes straight to 13 AFR.

Anyone know of any way I can get the reaction time of the MS faster? Should I use MAPdot and put the map sensor right behind the throttle plate?
Last edited by ion332 on Mon May 29, 2006 8:35 am, edited 1 time in total.
MSnS 029t
94 Probe GT custom headers/ short ram intake/282dur cams/modded intake
147wtq@6800/197whp@7700rpms
ion332
Helpful MS/Extra'er
Posts: 112
Joined: Sun Sep 25, 2005 5:47 pm

Re: Getting WOT throttle-on lean spike HELP!

Post by ion332 »

So, any ideas?
MSnS 029t
94 Probe GT custom headers/ short ram intake/282dur cams/modded intake
147wtq@6800/197whp@7700rpms
ion332
Helpful MS/Extra'er
Posts: 112
Joined: Sun Sep 25, 2005 5:47 pm

Post by ion332 »

http://www.box.net/public/27ejdmco59 (4.7mb datalog)
http://www.box.net/public/b0m5h7ucto (datalog)

The second smaller datalog has an event at 164 seconds or so.. The event lasts less than a second, but its still worriesome nonetheless.

I would rather not just bump up the fuel at high MAP values because then then the car will lose hp. They do need to be moved up slightly I realize this but thats not the effect causing the spike.
MSnS 029t
94 Probe GT custom headers/ short ram intake/282dur cams/modded intake
147wtq@6800/197whp@7700rpms
ion332
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Posts: 112
Joined: Sun Sep 25, 2005 5:47 pm

Post by ion332 »

Well, due the the motors characteristics, lowering the fuel where you suggest is not doable. :( If it was I would do it instantly believe me my wallet would really appreciate it about now. :(

On partial throttle and/or steady state, the MAP starts out at around 1k/50kpa at idle, then, as it approaches 2300, it goes down to around 40kpa, then it goes back up as it approaches 3k.. It has alot of peaky resonances.

Autotune already pretty much gave up already lol..
MSnS 029t
94 Probe GT custom headers/ short ram intake/282dur cams/modded intake
147wtq@6800/197whp@7700rpms
ion332
Helpful MS/Extra'er
Posts: 112
Joined: Sun Sep 25, 2005 5:47 pm

Post by ion332 »

ONe thing that makes it difficult to tune that area on the fly is that the wbo2 signal swings wildly between 12.5 to 16 AFR at those rpms/kpa.. I don't think the logger catches it though, although sometimes it does... So my passenger tunes it more to the rich side of the swings after autotune yanked around on it, which obviously is too rich.

I will post the msq later. ;) But, I messed around with the AE a bit and I think I got it now. :) I lowered the threshold a bit, then I had to decrease the enrichment values at the lowest MAP/s. So, now AE comes on earlier rather than it being an all or nothing sort of thing.
I am using TPS triggered accell with MAP based enrichment. My thought is that this will give the MS a little less delay to trigger the AE.

So, it seems to me theoretically you want AE to trigger as low of a threshold as possible with as small a AE start value as possible for the smoothest and most accurate AE, correct?
MSnS 029t
94 Probe GT custom headers/ short ram intake/282dur cams/modded intake
147wtq@6800/197whp@7700rpms
ion332
Helpful MS/Extra'er
Posts: 112
Joined: Sun Sep 25, 2005 5:47 pm

Post by ion332 »

OK, I think I got this all sorted out now...

ALRIGHT, I went ahead and fixed the VE table but NOW I realize WHY the VE table what like that. :(

It was to fix a misfire condition the car experiences off-idle.. No amount of accel settings seems to be able to fix this.

What happens is when I first hit the throttle off-idle, even just a very small stab about 1/4 throttle, the MAP shoots up to 1500rpm@95, then it goes down to around 2000rpm@40, then it goes back up again from there and behaves like a regular motor, with map increasing along with rpm... Problem is, when it goes down to around 40, it leans it and causes the engine to stumble badly.

I am moving over to rpm based accel, I don't think there is anyway I can tune around this otherwise. :(
MSnS 029t
94 Probe GT custom headers/ short ram intake/282dur cams/modded intake
147wtq@6800/197whp@7700rpms
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