Target Idle Speed M6 vs A4
The converter is a fluid coupling and has much more mass than just having a flywheel. Also the A4 idles are not as smooth as the m6, but the converter helps filter it a bit.
Is there any benefit to having a lower rpm idle? Fuel economy?
With my heads/cam, I bumped my idle to 850, but if I don't need it that high, should I tune it to idle lower?
I figure the higher idle makes it idle smoother, and easier to put into gear. But, hurts fuel economy?
With my heads/cam, I bumped my idle to 850, but if I don't need it that high, should I tune it to idle lower?
I figure the higher idle makes it idle smoother, and easier to put into gear. But, hurts fuel economy?
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From: Troy,MI.
You bet it hurts fuel economy. If you do a lot of stop/go driving then it REALY hurts it.Remember if you are stoped at a light you get 0 mpg. The higher the Idle speed the more fuel you are burning. The A/F ratio is the same (controled by the computer) so if you put more air in (higher idle speed) you must add more fuel.
Interesting..... And I do a ton of stop and go driving.
Maybe I should tune to lower my idle. And as long as it isn't too rough, and I don't stall..... leave it there. I don't have a very large cam.
Maybe I should tune to lower my idle. And as long as it isn't too rough, and I don't stall..... leave it there. I don't have a very large cam.
i think the idle on the A4 is lower at operating temperature to allow for softer gear engagement from neutral and to allow easier control of the IAC. if the idle was set at 800rpm on an A4 in gear you will have to press on the brake a little harder to keep it at a standstill and thats a bit inconvenient. my opinion is that it has nothing to do with the torque converter and its filtering abilities. another reason maybe is that its alot easier to launch an M6 from 800rpm than at 650rpms.
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The higher the idle is on an automatic, the harder it pulls when you're in gear with your foot off the brake. You don't want to be constantly riding the brakes when you're trying to creep along in a parking lot, etc. And yes, I know this doesn't apply to a car with a stall converter.
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Originally Posted by soundengineer
so why can A4's idle so much lower than an M6??
what is so different that an M6 has to be 150-200 rpm higher??
what is so different that an M6 has to be 150-200 rpm higher??
Originally Posted by Sharpe
My stock 99 LS1 M6 idles at 800 RPM.
teh A4 is at 650
i dont buy the "higher rpm uses more gas". try to set the rpm lower, itll bog adn with a big overlap cam you will see shittier gas mileage. theory and reality are totally different. if you set the idle on the a4 with the stock converter to a higher rpm itll be a pain in the *** to drive. i guess tahts why its lower. like stated, if you let off the gas with higher idle you dont want to be moving 10 mph lol
