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Old 03-28-2005, 01:30 PM   #1
Scooby Specialist
Member#: 29963
Join Date: Nov 2002
Location: chicago
04 sti

Default tuning philosophy

It seems that more and more tuners, or people that are posting at least are now tuning at what was preceived to be really lean conditions in the past (11.5-12 to 1 a/f ratio).

Is the above a change in philosophy, a change from growing knowledge about ej motors, or just going for the ultimate tune? Traditional thinking at least on this board,has been you should stay about 11.1 to 1 to keep it safe.

Also, what's everyone shooting for as a a/f during spool up? My thoughts and it seems to work well are 13 to 1 droping to 12 to 1 a/f covering 5-12psi
then droping to 11 to 1 ~ 10.9 towards redline.

What's everyone elses tunning philosophy?

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Last edited by wrex03; 03-28-2005 at 01:38 PM.
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Old 03-28-2005, 02:52 PM   #2
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Join Date: Apr 2000
Chapter/Region: VIC
Location: Delta, BC, Canada
2000 RS-T -> RSTi-8
Blue Ridge Pearl


From all that I have read, the only reason for such rich ratio is to prevent knock due to variables outside the car (like weather, gas). The way I see it, if you can get away running 11.5-12:1 without knock year round, do it.
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Old 03-29-2005, 12:04 AM   #3
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Chapter/Region: Tri-State
Location: wishing i was somewhere else
08 wrx


wrex03 - many of the recent dyno sheets that have been flowing around here have been 20gs, sr55s and other "larger" turbos. (i dont consider a 20g a big turbo).

But to risk sounding like an idiot and taking this out of context.
"If we were willing to run our turbochargers at peak efficiency then we could easily run AFRs in the 12:1 range but since we make substantially more power for every pound of boost added we choose to quench knock with fuel. You will also significantly add more power by advancing timing but again you need fuel to reduce knock." -Phil Element Tuning


To me, those SR55s that are running 19-20psi are in their peak efficiency range and therefore aren't already blowing hot charges so the extra fuel isn't needed to keep knock at bay.

*runs to corner hoping i'm right and that the tuning gods don't scald me*
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Old 03-29-2005, 09:38 AM   #4
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Location: chicago
04 sti


Nice link! And that's what I'm wondering.

So there are at least two thoughts on tuning that I have seen so far.

1) Low timing on spool to raise egts and then increasing timing and adding fuel after spool to lower egt's.

2) Higher timing off set with more fuel than in option one,which would reduce the chance of knock in the spool area. I would think this would be the more dangerous option, as with higher pressure caused by the timing any knock could be deadly.

Do both work the same? I've tried both and can't really tell the difference(butt dyno)! Which option above causes less stress on the engine assuming all things are done correctly.

Someone has ideas and thoughts! Let's hear them. Hopefully Clark, PDX, turboXS, Element, and some of the other people of knowledge will chime in.
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Old 03-29-2005, 10:03 AM   #5
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Location: lincoln, ri
2003 GGA MBP
12.9 / 105+


i don't "tune for spool." i've found it is not worthwhile. instead, run reasonable afrs, ramp them down to full load, and run as much timing as you can get away with. the timing power is always there--the boost power is not, and is unpredictable.
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