Erratic idle after new clutch and light flywheel
06-05-2008, 01:14 PM
#1
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Erratic idle after new clutch and light flywheel
Whats up fellas,
Well after my synchros took a crap, I decided to have my clutch and flywheel upgraded while the trans was getting fixed. So I had the spec stage 2+ clutch and a lightweight flywheel installed. I figured I'd give it some time to break in, but after about 750 miles, it is still doing the same thing.
The problem I am having only occurs while I have the air conditioning on. When I turn it on, and while it is on, it will cause my idle rpm to drop to around 500, then to compesate will shoot up to around 1000-1100 and go back down. It sometimes will hang around the 750 it is supposed to, but will randomly become erratic. It always has the erratic behavior when I first turn it on. It is also accompanied by some chatter, I'm guess this is due to the low rpms.
Last, when the AC is off, no erratic rpm, it stays constant at 750, and no chatter.
Any idea what is happening?Something to do with the decrease in rotational mass? Solutions? Thanks.
Well after my synchros took a crap, I decided to have my clutch and flywheel upgraded while the trans was getting fixed. So I had the spec stage 2+ clutch and a lightweight flywheel installed. I figured I'd give it some time to break in, but after about 750 miles, it is still doing the same thing.
The problem I am having only occurs while I have the air conditioning on. When I turn it on, and while it is on, it will cause my idle rpm to drop to around 500, then to compesate will shoot up to around 1000-1100 and go back down. It sometimes will hang around the 750 it is supposed to, but will randomly become erratic. It always has the erratic behavior when I first turn it on. It is also accompanied by some chatter, I'm guess this is due to the low rpms.
Last, when the AC is off, no erratic rpm, it stays constant at 750, and no chatter.
Any idea what is happening?Something to do with the decrease in rotational mass? Solutions? Thanks.
06-05-2008, 07:20 PM
#3
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Join Date: Mar 2007
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RE: Erratic idle after new clutch and light flywheel
I thought about raising the idle rpm, but wanted to get some feedback first. What do guys think is a safe idle rpm since the idle is not erratic when the AC is off? Any idea about the chatter? The chatter is only comes when the AC is on as well.
Thanks
Thanks
06-05-2008, 07:24 PM
#4
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Join Date: Feb 2007
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RE: Erratic idle after new clutch and light flywheel
ORIGINAL: AmericanSpeed
Whats up fellas,
Well after my synchros took a crap, I decided to have my clutch and flywheel upgraded while the trans was getting fixed. So I had the spec stage 2+ clutch and a lightweight flywheel installed. I figured I'd give it some time to break in, but after about 750 miles, it is still doing the same thing.
The problem I am having only occurs while I have the air conditioning on. When I turn it on, and while it is on, it will cause my idle rpm to drop to around 500, then to compesate will shoot up to around 1000-1100 and go back down. It sometimes will hang around the 750 it is supposed to, but will randomly become erratic. It always has the erratic behavior when I first turn it on. It is also accompanied by some chatter, I'm guess this is due to the low rpms.
Last, when the AC is off, no erratic rpm, it stays constant at 750, and no chatter.
Any idea what is happening?Something to do with the decrease in rotational mass? Solutions? Thanks.
Whats up fellas,
Well after my synchros took a crap, I decided to have my clutch and flywheel upgraded while the trans was getting fixed. So I had the spec stage 2+ clutch and a lightweight flywheel installed. I figured I'd give it some time to break in, but after about 750 miles, it is still doing the same thing.
The problem I am having only occurs while I have the air conditioning on. When I turn it on, and while it is on, it will cause my idle rpm to drop to around 500, then to compesate will shoot up to around 1000-1100 and go back down. It sometimes will hang around the 750 it is supposed to, but will randomly become erratic. It always has the erratic behavior when I first turn it on. It is also accompanied by some chatter, I'm guess this is due to the low rpms.
Last, when the AC is off, no erratic rpm, it stays constant at 750, and no chatter.
Any idea what is happening?Something to do with the decrease in rotational mass? Solutions? Thanks.
this happens to me every time i turn on my car... when the engine is cold the rps jump all over the place and i have to wait about 10-15 seconds until i start to drive or else it is jumpy.. btw this happened as soon as i got my tune, but i just havnt done anything about it. also it only did this when it was real cold like 30-45 degrees out. its fine now though
06-06-2008, 10:31 AM
#5
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RE: Erratic idle after new clutch and light flywheel
the problem doesn't go away after the initial start up. I raised the rpm to 790 with the tuner and that seems to be helping. The chatter is still there, its extremely annoying. Any ideas about the chatter?
06-06-2008, 02:17 PM
#6
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RE: Erratic idle after new clutch and light flywheel
My guess is the erratic idle with the air on is caused by the lighter flywheel. A heavier flywheel helps the momentum of the engine stay constant, this is probably why the RPM's take a while to come down when gunning it in neutral with a factory flywheel. With the air on, there is more drag on the engine so the RPM's come down faster than the computer is programmed for so it compensates by giving it a little gas which causes the RPM's to shoot up faster than intended then it just becomes a vicious circle. I would assume this can be programmed out with a custom tune but then again I could be way off base too.
06-06-2008, 03:34 PM
#7
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RE: Erratic idle after new clutch and light flywheel
ORIGINAL: 06VistaBlueGT
My guess is the erratic idle with the air on is caused by the lighter flywheel. A heavier flywheel helps the momentum of the engine stay constant, this is probably why the RPM's take a while to come down when gunning it in neutral with a factory flywheel. With the air on, there is more drag on the engine so the RPM's come down faster than the computer is programmed for so it compensates by giving it a little gas which causes the RPM's to shoot up faster than intended then it just becomes a vicious circle. I would assume this can be programmed out with a custom tune but then again I could be way off base too.
My guess is the erratic idle with the air on is caused by the lighter flywheel. A heavier flywheel helps the momentum of the engine stay constant, this is probably why the RPM's take a while to come down when gunning it in neutral with a factory flywheel. With the air on, there is more drag on the engine so the RPM's come down faster than the computer is programmed for so it compensates by giving it a little gas which causes the RPM's to shoot up faster than intended then it just becomes a vicious circle. I would assume this can be programmed out with a custom tune but then again I could be way off base too.
06-06-2008, 06:31 PM
#9
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RE: Erratic idle after new clutch and light flywheel
The "chatter" might be a little gear rattle between the gear on the input shaft and its mating gear on the countershaft. Reducing the rotational inertia of the flywheel has moved some natural frequency to where it gets excited at idle rpm. The rattle itself would involve the gear teeth and the backlash that exists between them. If that's indeed the case, you should be able to stop it at idle speed by disengaging the clutch. The Tremec 3550 in one of my other cars (with a stock but relatively light 10.4" flywheel) does this.
Norm
Norm
06-06-2008, 08:34 PM
#10
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RE: Erratic idle after new clutch and light flywheel
thanks for the replys everyone. The chatter definently sounds like its coming from the tranny area. It's just a little odd that the chatter only becomes audible when the AC is turned on. When the AC is off, no noise what so ever.
Whats your guys take on the idle being at 790 rpm? Safe?
Whats your guys take on the idle being at 790 rpm? Safe?