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Old 10-07-2002, 05:46 PM   #18
nmyeti
Scooby Specialist
 
Member#: 4980
Join Date: Mar 2001
Location: Albuquerque, NM USA
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Quote:
Originally posted by d00f
What would the effect have been with less advance and less fuel? Also, your pump gas is what (north american system) octane?
93 octane; Less advance and less fuel = higher EGTs in the upper RPM range. For reference the stock ECU wants to run as much as 34-36 degrees at redline on C16.

Quote:
Originally posted by d00f
The WRX I sat in was running 10.6 in stock form. The unichip tuner leaned it out to about 11.6 as well as advancing the ignition by a few degrees. The power increase was very noticeable and the more he leaned it out the better it went. All this and the EGTs were staying quite low.
Just wondering did the tuner check the detonation level with a microphone on the block and a head set? I'd be surprised if you were not getting detonation at that level that was too slight to hear over the engine noise in the dyno room.

The advance helps keep the EGTs cool, so you can advance and lean the car out if you have enough octane to support it in your fuel, but frankly pump fuel in most of the US does not have enough to keep the small detonation away from your motor at the A/F level you're quoting. It's even worse when you also know that the car is going to lean out a bit on the road because of additional air flow over the intercooler.


Quote:
Originally posted by d00f
Is it possible that this large discrepancy is coming from the specific mods on the car you were tuning where for some odd reason it likes to be run really rich?

It's possible that my tired recollection doesn't have the numbers right but it just strikes me as really rich...

-Michael
We run a stage2 car in the 10.5 to 10.7:1 range. We run them rich to keep our customers from running into issues when they road-race the car or fill up with less than perfect pump fuel. We also know that there are customers that will up the boost and take the car on very long high speed runs. I want to know for sure there is enough fuel in the system to keep detonation and EGTs under control. We only lean the car out when we make a "race gas" map.


-Nathan
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