 mixture adjustment via head temp resistance |
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| ape914 |
 Apr 4 2012, 10:12 AM
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red locktite  Group: Retired Members Posts: 240 Joined: 7-February 11 From: In front of a computer Member No.: 12,676 Region Association: None  |
Just wondering if anyone has made up some data points on how a change of resistance in the head temp circuit effects the mixture?
I know of some one long ago that had installed an additional head temp resistor in line. They wired a variable resistor (potentiometer) all the way up to the dash so they could add enrichment on the fly. They had no airfuel meter so it was all seat of the pants. I am considering that a a possible fine tunning method on a D-jet 914. With an aftermarket cam, big bore pistons and non-stock compression ratio, I think there might be some room to add enrichment across the range. what I am thinking is to add an airfuel ratio meter, or go by head or exhaust temp as a guide, and adjust the mixture via this method and watch the gauges to try to find an optimal setting. Has anyone already tried this? How does head temp reistance effect the mixture? is it uniform across the rpm and load range? or does it only effect certain running conditions? Just begining the thought process on this, and dont want to re-invent the wheel if it has already been tried. By running a parallel reisistance, one could also lean out the mixture. I know some folks will tune the Pressure sensor (MPS) to change mixture, but I am thinking this is one more tunning tool maybe,and with a variable resistor wired to the dash, it can be changed on the fly, unlike MPS adjustments. |
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| Dave_Darling |
Apr 4 2012, 11:06 AM
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914 Idiot Group: Members Posts: 15,161 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California 
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Brad Anders has done circuit analysis of the ECU boards. He had some comments about the CHT resistance and its effects. You may have to search around a bit to find the info: http://members.rennlist.com/pbanders
I don't think anyone really knows the exact effect of CHT resistance on mixture, probably because there are a ton of variables that go into determining the mixture on a running car. In general, the higher the resistance the richer the mixture. The effect pretty much goes away completely under about 100 ohms, if I remember Brad's writing correctly. The table about 2/3 of the way down this page (CLICK ME!) talks a bit about the CHT's effects. Aha, here (CLICK ME!) is his very detailed discussion of what the CHT circuit does inside the ECU! --DD |
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Posts in this topic
ape914 mixture adjustment via head temp resistance Apr 4 2012, 10:12 AM
ape914
Brad Anders has done circuit analysis of the ECU ... Apr 4 2012, 01:20 PM
76-914 The MPS won't like the cam overlap. Maybe LJet... Apr 4 2012, 12:40 PM brant my understanding (but go read all of the brad ande... Apr 4 2012, 01:28 PM ape914
my understanding (but go read all of the brad and... Apr 4 2012, 01:43 PM brant cool then you cam sounds like you don't have a... Apr 4 2012, 01:55 PM ape914
cool then you cam sounds like you don't have ... Apr 4 2012, 01:59 PM brant I really don't
I know exhaust probes we'r... Apr 4 2012, 02:06 PM |
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