Throttle hang and the Idle Stepper Table
Oct 9, 2006, 05:32 PM
#31
Originally Posted by tsi90awd
Maybe. The perception of a problem is colored by your expertise. If you are mechanically inclined, you tend to think in terms of the CBV, throttle spring, clutch restricter, etc. If you are software inclined, you tend to think in terms of the ECU. Maybe it is two different issues, I don't know. Or, a combination of systems with the intent of slowing down the closing of the throttle, probably for emmissions control.
I mainly notice it shifting rapidly at high revs. Obviously, you try to let off on the throttle at the same time as disengaging the clutch. If some "system or systems" is holding the throttle open when you take the load off the engine, this may result in a raise in RPM. It depends on how much the throttle is open and how fast you are shifting as to whether the RPM raises or drops off slower than expected.
All I know for sure, is that it is annoying!
I mainly notice it shifting rapidly at high revs. Obviously, you try to let off on the throttle at the same time as disengaging the clutch. If some "system or systems" is holding the throttle open when you take the load off the engine, this may result in a raise in RPM. It depends on how much the throttle is open and how fast you are shifting as to whether the RPM raises or drops off slower than expected.
All I know for sure, is that it is annoying!
Stock Air filter and JDM DV= 200rpm raise
Stock Air filter and Forge RS (full soft)=worse rpm raise(500rpm)
Works air filter and Forge RS=200 rpm raise
Works air filter and JDM DV= NO RPM raise.
I tied adjusting the RS from full soft to 10 clicks and noticed the harder the setting the higher the rpm rose.
Oct 9, 2006, 06:24 PM
#32
Originally Posted by cpoevo
I have an '03 and my car does the "throttle hang" this happens even when in nuetral and the car is not moving and the clutch is depressed. The RPM's drop normally until it gets down to about 2500 and then the rpms drop slowly to idle.
Oct 12, 2006, 04:50 AM
#34
Its funny you mention that.. I have a friend who had been running meth injection for awhile, when I took his IACV out, the tangs were worn off the valve and it would just spin and never adjust.. He had tons of idle problems under different conditions. I made adjustments for a few hours until we got fed up and pulled it out. When I put one of my spares in, it fixed his problem (it was somewhat different than this specific problem though)
So it really can't hurt to check and clean that valve..
HOWEVER, some of you guys having trouble are on low mileage stock cars..
Oh that reminds me, he has my spare valve and he needs to get it to me soon, I was planning on installing my intake manifold and throttlebody in the next 2 weeks.
So it really can't hurt to check and clean that valve..
HOWEVER, some of you guys having trouble are on low mileage stock cars..
Oh that reminds me, he has my spare valve and he needs to get it to me soon, I was planning on installing my intake manifold and throttlebody in the next 2 weeks.
Oct 12, 2006, 09:13 AM
#37
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Originally Posted by MalibuJack
Its on the throttlebody, if you look at the pipe that runs to the throttlebody (your upper intercooler pipe) its below that, not clearly visible, but easy to get at if you take the pipe off.
Oct 12, 2006, 11:24 AM
#39
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Interesting and logical thought but i would think that a JDM EVO8 BOV should be well suited in my setup. I mean its the stock turbo, and plumbing with the exception of an apexi intake. Maybe 25PSI has something to do with it. None the less if this is my problem what would be a good remedy? Different DV?
Jan 13, 2007, 06:22 PM
#41
Dont know if this is related but same symptom - When I was rigging stuff in order to get my DV holding solid to redline in between shifts it gets overloaded with air (especially at 26 psi). DV opens but not in time, so when I lift the throttle the air forces it back open and a good portion VTE's (vents to engine) making the rpm peg the rev limit between shifts durring high boost and cold days.
One little additional spring to the TB (two in there, added a third) was enough to overcome the additional air that pushed it beyond it's design. So now - no more involuntary RPM blips between shifts - I was starting to get so frustrated with it that I was going to give up the top end boost to make it quit.
Now the car is so much fun to drive I have to make excuses to my wife for grocery shopping so I can go to get to drive it.
One little additional spring to the TB (two in there, added a third) was enough to overcome the additional air that pushed it beyond it's design. So now - no more involuntary RPM blips between shifts - I was starting to get so frustrated with it that I was going to give up the top end boost to make it quit.
Now the car is so much fun to drive I have to make excuses to my wife for grocery shopping so I can go to get to drive it.
Jan 13, 2007, 06:56 PM
#42
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I've tried reducing the values in the upper-RPM range of the idle stepper table. I basically treated the RPM axis as being scaled wrong, so I assumed it really represented the entire RPM band. The changes did seem to help, but I would have to do some more testing to get conclusive answers. I'd like to log a couple runs to see if the idle stepper values are reduced.
I'm a little discouraged with the effectiveness of the idle settings since I've tried reducing the "desired idle RPM" and it has zero effect no matter what I do.
I'm a little discouraged with the effectiveness of the idle settings since I've tried reducing the "desired idle RPM" and it has zero effect no matter what I do.
Jan 14, 2007, 08:00 AM
#43
Dont know if this is related but same symptom - When I was rigging stuff in order to get my DV holding solid to redline in between shifts it gets overloaded with air (especially at 26 psi). DV opens but not in time, so when I lift the throttle the air forces it back open and a good portion VTE's (vents to engine) making the rpm peg the rev limit between shifts durring high boost and cold days.
One little additional spring to the TB (two in there, added a third) was enough to overcome the additional air that pushed it beyond it's design. So now - no more involuntary RPM blips between shifts - I was starting to get so frustrated with it that I was going to give up the top end boost to make it quit.
Now the car is so much fun to drive I have to make excuses to my wife for grocery shopping so I can go to get to drive it.
One little additional spring to the TB (two in there, added a third) was enough to overcome the additional air that pushed it beyond it's design. So now - no more involuntary RPM blips between shifts - I was starting to get so frustrated with it that I was going to give up the top end boost to make it quit.
Now the car is so much fun to drive I have to make excuses to my wife for grocery shopping so I can go to get to drive it.
Jan 14, 2007, 08:04 AM
#44
I've tried reducing the values in the upper-RPM range of the idle stepper table. I basically treated the RPM axis as being scaled wrong, so I assumed it really represented the entire RPM band. The changes did seem to help, but I would have to do some more testing to get conclusive answers. I'd like to log a couple runs to see if the idle stepper values are reduced.
I'm a little discouraged with the effectiveness of the idle settings since I've tried reducing the "desired idle RPM" and it has zero effect no matter what I do.
I'm a little discouraged with the effectiveness of the idle settings since I've tried reducing the "desired idle RPM" and it has zero effect no matter what I do.
Base idle should be around 750rpm or so, then the stepper does its work from there. This was a trick to raise idle speed before there was access to the settings in the ECU, or if the base idle is too low or too high and needs minor adjustment. What ends up happening is you open the BISS, and the stepper ends up completely closed in an attempt to adjust idle quality and speed, or other stepper values, and basically unable to do anything.
Jan 14, 2007, 08:14 AM
#45
Its funny because all of the aftermarket designs have tiny little diaphragm or valve surfaces, when more surface area will offer a more effective function without requiring as much spring pressure. I have been wanting to have a machine shop make something to demonstrate that.
That valve actually had a lower port, too that could be connected to a pre-throttle plate pressure source to help with part-throttle lift-off to still open very easily. This is how I had it setup on my DSM and it held 30 psi and still opened with ease, without any hint of flutter.
Eric