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Old 09-22-2009, 05:06 PM   #1
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Default engine runs hot after a few minutes of racing..??

can anyone explain to my why a perfectly sealed engine(including the entire fuel system/tank) would temp and run fine for the first few minutes of a qualifier/race and then have the temps climb up into the low/mid 300 range ?? the engine(v-spec's) got about 9 tanks thru it....backplate, carb and h/s needle are all sealed. the front bearing is not leaking. plenty of engine smoke upon acceleration.....but, i've been told that if the L/S needle is set a bit too lean that it could cause an engine to overheat the longer that it is run.....typically after a few minutes of hard running.....anyone ever heard of such a thing..??
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Old 09-22-2009, 05:11 PM   #2
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are you trying to tune the motor before it gets up to temp.
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Old 09-22-2009, 05:23 PM   #3
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Sometimes if the top is right but the bottom is too lean the temps will just keep climbing.

Also, it can take well over 5 minutes of running before the motor reaches full temp so if it's a bit too lean it might not show on the temps during warm-up.
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Old 09-22-2009, 05:25 PM   #4
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do all the tuning after running 2-3 minutes after the engine temps in the low/mid 200's...............just chasing the L/S deal............the engine passes a 3-5 second pinch test after a few high speed passes......
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Old 09-22-2009, 05:26 PM   #5
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thanks for the input guys...........you've given some good advise.......
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Old 09-22-2009, 05:29 PM   #6
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if you have anymore just ask and good luck.
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Old 09-22-2009, 05:35 PM   #7
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Plenty of smoke?
When I'm lost I tune till I'm a bit boggy (rich) and retune. make sure your hot before you tune like said above.

I like to stop for 3-5 seconds on the turn after the straight. (The low needle pinch test never works for me. ) It should bog just a little when you take off again if its too rich on the bottom. And I make sure I've got good smoke at least half way down the front straight.

Spit test, well don't spit on the head, i usually wipe a bead cross the top of my Novas head, it should boil and bubble for a bit then maybe evap in a few more seconds (250?). If it dissappers too quick then you really are too hot.

Usually my wet finger deosn't get burnt, but it should hurt. Pain is hardly a good temp gauge though.
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Old 09-22-2009, 05:47 PM   #8
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Oh yeah, one other thing. Not all tanks react the same. Most tanks will run a bit rich when full and lean out as it goes down. This can cause the motor to heat up at the end of a run. Some tanks stay pretty consistent through a run, some actually do the opposite. Start out lean and richen up. Weird I know but anyone that had an original tank Mugen MRX3 knows what I mean.
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Old 09-22-2009, 06:40 PM   #9
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Before I tweak any of the needles, I run the car/truck until the chassis is very warm to the touch under the center diff and engine area.

The ONLY exception is if I know it is WAY off.

If I am not sure how warm the engine is and if it hasn't radiated enough heat yet, ie:get the warm up late, etc. I will try and stay a little on the rich side, meaning that the car won't feel as crisp, knowing it will improve in a couple minutes.
This of course means you won't be stretching the fuel mileage to 9 or t10 minutes, but it also means more time between rebuilds!


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Old 09-22-2009, 07:07 PM   #10
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did you mess with the mid-range alex?

make sure you tune evenly...like just cause it runs ok, dont mean your hsn couldnt be causeing you random flame outs or over heating on the track,same goes for the lowend...adam drake talks about it really well in that nova-rossi tuning vid on youtube..

what carb insert you running? i wouldnt go over a 8mm


how is the idle?

what pipe do you run
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Old 09-22-2009, 07:37 PM   #11
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didnt touch the mid range spray bar. and, when it does "overheat" it comes into pit lane actually "humming" rather than idleing......hot, for sure.
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Old 09-22-2009, 07:46 PM   #12
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Quote:
Originally Posted by alexrckid View Post
didnt touch the mid range spray bar. and, when it does "overheat" it comes into pit lane actually "humming" rather than idleing......hot, for sure.
Big indication of too lean on the bottom.
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Old 09-22-2009, 08:23 PM   #13
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Quote:
Originally Posted by wingracer View Post
Big indication of too lean on the bottom.
i agree...

mabe back it out some on the bottom and lean it out on the top some to compensate...of kourse depending on the situation etc..
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Old 09-23-2009, 10:13 AM   #14
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i did find out that whn came in "humming", richening up the lo-speed was a fix............just cant figure out why..??
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Old 09-23-2009, 10:17 AM   #15
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Quote:
Originally Posted by alexrckid View Post
i did find out that whn came in "humming", richening up the lo-speed was a fix............just cant figure out why..??
Chances are Brad that you have a false idle, and it's making it imposable to get the LSN right.. Come see me next weekend and i'll get it straightening out for you..
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