Idle with new Cam?
Thread Starter
Le Mans Master
Joined: Aug 2004
Posts: 5,141
Likes: 7
From: Metairie Louisiana
Idle with new Cam?
I'm wondering where everyone has their idle set with an aftermarket cam. The one I installed has a pretty good lope to it. It's definately not a hotcam. In the new tune it appears to be set to idle at 850 rpms. Would lowering it some be a good idea or just make it kill? See signature for cam specs and mods.
Thanks
Thanks
Race Director
Joined: Jan 2002
Posts: 12,263
Likes: 86
From: O'Fallon Missouri
Rick, I'm running an M6 with a 224/230 605/622 112 camshaft, and have my idle set at 800 rpms. I don't like the idle set so low that it sounds like the car is going to stall when idling. Yor camshaft has a tighter LSA and your running an A4. So, 850 rpms sounds about right to me. Don't know if you do your own tuning? But, it only takes a couple if minutes to change the idle and see what happens.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
I don't recommend you try to lower the idle speed. Due to your cam, you need the higher idle. Don't concern yourself with a hundred (100) RPMs at idle.
I agree, too, that your cam calls for that idle speed due to its duration and LSA of 109.
At the current idle speed, your idle shouldn't be too raunchy; mine's only noticable and listeners actually have to spend a little time to actually hear that it's different from stock.
Since this is the second time you've mentioned this issue, I'm now suspecting that you may have a vacuum leak or a too tight lifter preload adjustment. If it turns out that you don't have either, you'll have to chalk it up to the 109. Comes with the territory.
Remember, most of our aftermarket cams are on 112 or higher LSA. That decreases the over-lap and smooths the idle. Some guys like the tighter LSA because of the peakier torque curve it gives, but there's a trade-off - Isn't there always?
Jake
West Point ROCKS!
I agree, too, that your cam calls for that idle speed due to its duration and LSA of 109.
At the current idle speed, your idle shouldn't be too raunchy; mine's only noticable and listeners actually have to spend a little time to actually hear that it's different from stock.
Since this is the second time you've mentioned this issue, I'm now suspecting that you may have a vacuum leak or a too tight lifter preload adjustment. If it turns out that you don't have either, you'll have to chalk it up to the 109. Comes with the territory.
Remember, most of our aftermarket cams are on 112 or higher LSA. That decreases the over-lap and smooths the idle. Some guys like the tighter LSA because of the peakier torque curve it gives, but there's a trade-off - Isn't there always?
Jake
West Point ROCKS!
Thread Starter
Le Mans Master
Joined: Aug 2004
Posts: 5,141
Likes: 7
From: Metairie Louisiana
I think it's just that I have not been in a car with a cam in so long that I am not used to it. I'm used to the Vette being fairly still at a redlight. My 67 had a cam but it's been so long I forgot how it felt. Of course it also had an exhaust system that probably tamed down the experience a bit. Whats the best way to track down any vacuum leaks, just in case? I did request a cam with a heavy lope. I'll get used to it.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
I think it's just that I have not been in a car with a cam in so long that I am not used to it. I'm used to the Vette being fairly still at a redlight. My 67 had a cam but it's been so long I forgot how it felt. Of course it also had an exhaust system that probably tamed down the experience a bit. Whats the best way to track down any vacuum leaks, just in case? I did request a cam with a heavy lope. I'll get used to it.
FWIW, many of the factory cams have an LSA of 115* or even 117*, not to mention less duration than what you have.
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Pro
Joined: Aug 2004
Posts: 549
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From: Richmond VA
With an LSA of 110 mine is not perfectly still either but close you are at LSA 109 so yours will be more pronounced. still it should not shake badly.
For me, finding a leak without a smoke machine is a PITA unless you know what area is suspect. If a gasket leak do what 96GS#007 says.
For me, finding a leak without a smoke machine is a PITA unless you know what area is suspect. If a gasket leak do what 96GS#007 says.
Last edited by blue94; Mar 25, 2009 at 05:39 PM. Reason: spelling
