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Old 03-19-2006, 07:14 AM   #1
xolosis
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Default UTEC - Part Throttle Stumble

Ok when I go WOT the car just hauls and I get no knock events and everthing seems sweet. However I have the infamous stumble while cruising at highway speeds. For instance in 5th gear at 100kph (about 60mph) I get a stumple between 2000-2500rpm. Its only when I lighly lift off the throttle or lightly apply throtte.

Now does this have to do with the Close Loop Fueling crossing over to Open Loop? Or is it an Ignition Map tuning exercise?

Can somone please point me in the right direction in getting this tuned out?

Cheers!
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Old 03-19-2006, 09:30 PM   #2
Davenow
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Set the crossover point higher, like 28%
Add some timing in the lowest column.
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Old 03-20-2006, 08:12 AM   #3
xolosis
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Well I set the crossover to 40% and all seems to be running well. However this defeats the purpose in running Open Loop Fuel mode.

davenow how much timing do you reckon I should add to the 0% column? I'll do this then bring the crossover point down to 30%...
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Old 03-20-2006, 09:10 AM   #4
tmarcel
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Quote:
Originally Posted by xolosis
Well I set the crossover to 40% and all seems to be running well. However this defeats the purpose in running Open Loop Fuel mode.

davenow how much timing do you reckon I should add to the 0% column? I'll do this then bring the crossover point down to 30%...

He didn't mean the 0% column, rather the 10% or above. You might want to take a look at your ECU timing as a reference in the 0% column and that'll give you a timing to shoot for. There's also a CL to OL transition that you can either increase or decrease if you're on firmware 5.
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Old 03-20-2006, 10:39 AM   #5
hippy
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If you have a wrx with stock turbo, you're probably better off just leavin the crossover at 40-60% and setting the values in the boost map in those areas low to keep the boost down. That's just my $.02 though.

peace
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Old 03-20-2006, 07:23 PM   #6
xolosis
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I've got a FXT so I am using STi 1.1c UTEC which had the Open Loop Threshold % is set to 20% default. After changing it to 40% the car drives like stock on part throttle. However I would like to use the default 20% crossover and tune timing and fuel to get a smooth transition.

However another issue I've got is shift knock but will start another thread to keep things consistent.
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Old 03-21-2006, 01:09 AM   #7
gaby
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ECU on the 10-20% timing and fuel loads fixed mine.
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Old 03-21-2006, 09:18 AM   #8
ride5000
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logs logs logs logs logs logs logs logs logs logs
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Old 03-21-2006, 12:24 PM   #9
Freon
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I put "ECU" in the timing map in the 10% column from 500 to 3500rpm.

The problem is the UTEC uses the same timing from 20inHg vacuum all the way up to +2 or +3 psi or so. That's how the 10% column works.

If you put ECU in the 10% column at lower RPM, your UTEC waits until you are making 2-3psi before it takes over (in 20% column). You are still letting your UTEC control high loads and boost, but your factory ECU is a lot smarter with timing over such a wide range.

And you can also add a lot of timing to the lower load sites in the base maps. They have way too little timing in the 10-20% columns from 2500-4000rpm.
http://www.wrxhackers.com/forums/showthread.php?t=3491
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Old 03-23-2006, 12:07 AM   #10
xolosis
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Thanks all and yes I got to upload my logs. I getting some more bits put on the car today and will go logging mad this weekend.

Freon that is great information. Would you have a copy of he pic with the correct timing you recommend. Your pic links are dead over at wrxhackers...
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Old 03-28-2006, 08:46 PM   #11
beauhawk
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Try adjusting the fuel crossover. It fixed my problems.
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Old 03-30-2006, 08:38 AM   #12
xolosis
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Yep this is what I did (a couple of posts earlier). I set it to 40% cross over and the car is much smoother when cruising everyday.

Guys is it bad to say set the TPS to -20% and then set the CL/CL crossover to 20%. I've seen this suggested on older posts but and apparently eliminates the stumble all together. However you need to set your Min PSI to around 5 so you will arrive in the correct load columns.

Does this make sense?
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