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Location:
Perth, WA
Registered:
May 2002
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Re: AFM 4AG idle problem (long)
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Thu, 13 June 2002 05:06
 
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Ben,
Its your intercooler that is causing the problems.
The standard top mount cooler is both small, and has a short intake tract. the bigger the cooler and the longer the intake tract is the worse the problem is.
The idle system is a feedback system, and the intercooler causes a time delay to be added to the system, which can cause the system to become unstable. This causes the idle problems.
Think of it this way.
The IC is after the throttle and is therefor basically and extnetion of you intake plenum. At idle, air flow is very low, so to consume this much air takes time, a lot if time compared to when u are fanging it.
The idle becomes low, the ECU opens the idle control a bit, but because the volume after the throttle is so large, this tiny throttle opening takes a while to have an effect. The revs keep dropping more so the ECU opens it more, still takes time to get there and the revs drop more. The ECU opens the idle again. The first increase in airflow coming through from the first idle control opening gives the motor some air, the revs rise back to the right position so the ECU closes the idle down a bit.... Too late because it already allowed a shit load of air in before, and this works its way to the motor. The revs rise with all this extra air and become too high, so the ECU closes the idle valve. The revs keep rising because of all this air... then the horrible cycle repeats but in reverse of what i have described.. the revs drop down and when they are right, the ECU opens the idle a bit.. but it has no immediate effect, so it opens it a bit more.. and a bit more... and it just repeats over and over and over.
This is why i fitted a Subaru water to air intercooler to my ae86 with GZE to keep this problem to a minimum, but it still did it a little bit. One other solution is to fit another throttle AFTER the intercooler...my runs perfect now as i have a RWD 4A-GE inlet manifold and am running a Turbo. Rock steady idle even with the original computer, as the ECu does not control my idle anymore.
MAP gze's do not do this anyware near as bad. I hav not got my head around this properly, but its just a fact that they are better... maybe less gain on teh feedback loop to the idle control??
Cheers
Mike
PS. If you dont have a cooler then i dont know what the problem is..hahaha and i wasted 10 minuites of my time.
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| | Subject | Poster | Date |
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AFM 4AG idle problem (long)
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Ben Wilson | Sun, 09 June 2002 09:38 |
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Re: AFM 4AG idle problem (long)
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whiteGZE | Sun, 09 June 2002 09:48 |
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Re: AFM 4AG idle problem (long)
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MaNGeW | Sun, 09 June 2002 10:33 |
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Re: AFM 4AG idle problem (long)
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troyboy | Sun, 09 June 2002 11:56 |
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Re: AFM 4AG idle problem (long)
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Sam | Sun, 09 June 2002 23:17 |
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Re: AFM 4AG idle problem (long)
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Ben Wilson | Mon, 10 June 2002 01:28 |
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Re: AFM 4AG idle problem (long)
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Celica_RA40 | Mon, 10 June 2002 11:43 |
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Re: AFM 4AG idle problem (long)
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Twinky | Mon, 10 June 2002 13:47 |
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Re: AFM 4AG idle problem (long)
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Ben Wilson | Mon, 10 June 2002 21:57 |
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Re: AFM 4AG idle problem (long)
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Twinky | Tue, 11 June 2002 11:33 |
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Re: AFM 4AG idle problem (long)
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Celica_RA40 | Tue, 11 June 2002 11:41 |
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Re: AFM 4AG idle problem (long)
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Twinky | Tue, 11 June 2002 12:46 |
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Re: AFM 4AG idle problem (long)
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Celica_RA40 | Tue, 11 June 2002 12:57 |
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Re: AFM 4AG idle problem (long)
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Ben Wilson | Tue, 11 June 2002 22:05 |
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Re: AFM 4AG idle problem (long)
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Celica_RA40 | Wed, 12 June 2002 08:32 |
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Re: AFM 4AG idle problem (long)
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Twinky | Wed, 12 June 2002 08:53 |
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Re: AFM 4AG idle problem (long)
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Ben Wilson | Thu, 13 June 2002 01:48 |
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Re: AFM 4AG idle problem (long)
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AE86_Sprinter | Thu, 13 June 2002 05:06 |
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Re: AFM 4AG idle problem (long)
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Grant | Thu, 13 June 2002 06:57 |
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Re: AFM 4AG idle problem (long)
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whiteGZE | Thu, 13 June 2002 10:24 |
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Re: AFM 4AG idle problem (long)
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Twinky | Thu, 13 June 2002 12:42 |
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Re: AFM 4AG idle problem (long)
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Ben Wilson | Thu, 13 June 2002 22:04 |
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Re: AFM 4AG idle problem (long)
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Grant | Fri, 14 June 2002 06:20 |
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Re: AFM 4AG idle problem (long)
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Ben Wilson | Fri, 14 June 2002 14:11 |
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