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Thread: technical question.....looking for constructive help

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Posts: 1-3 of 3
2010-06-13 16:16:34
#1
technical question.....looking for constructive help
My roomates ka-t is acting very strange. Hasan enthalpy tune, 750cc injectors, 300 zx maf, walbro fuel pump, built ka, no thermostat curently. Car runs and idles great. Drives dowthe road ok. As its on super low boost for break in its not too fast....but that's not the realquestion. The afrs are bang on perfect....14.7-16 idle, and around 11.5-12 under load if I remember currectly. Butthe egts are sky high! 1200 at idle, and even more under laod! Not to mention the egt bung is3 inches down the downpipe, so its looking like were dealing with closeto 1600 degrees egts! What could cause this? Whatshould theegts be? If they areway to hot, which I'm pretty surethey are(turbo cold side is scaulding hotafter afew minutes idling.) Istood 5-8 feet behind his car when he revved it, and I could phisically feel the heat hit me, it wasclose to uncomfortable to nearburning me. BUT the car doesn't overheat, at least not for a good 30 minutes of idling....which is probably just cause ofthe massive egts finally overwelming the coolant. Trying to solvethis one.....I'm lost. Car was notjurry rigged, its been well built. What couldcause highegts, while having good afr's and coolanttemp? NEVER seen something like this. Before.
2010-06-13 16:43:53
#2
Originally Posted by crznx2000
Butthe egts are sky high! 1200 at idle, and even more under laod! Not to mention the egt bung is3 inches down the downpipe, so its looking like were dealing with closeto 1600 degrees egts! What could cause this? Whatshould theegts be?
If the max you're seeing is 1,600°F then you're fine. The high EGTs are because the EGT sensor is placed 3" downstream of the turbo outlet. The collector, turbine and turbine exit are all very hot. Much hotter than the actual EGTs because they have four exhaust ports heating them up. If you had the probe on one runner right after the head you'd see much lower (and accurate) temps.

I don't see anything wrong. really.
Last edited by BenFenner on 2011-07-20 at 20-44-35.
2010-06-13 17:23:58
#3
Ben, aren't the turbo EGT's naturally higher only because of increased exhaust pressure before the turbo and frictional losses inside the turbo? Regardless of how many exhaust ports are contributing, I think that's the only way it could end up at a temperature higher than the port exit EGT.

You might also be lower than 1600 degrees. Since, as Ben pointed out, the temperature won't really start to drop until after the turbo, a 400 degree drop is an awful lot of energy loss through only 3 inches of pipe. The hot air you feel behind the car could be a lack of catalytic converter or a non-restrictive exhaust system.
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