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Old 06-12-2006, 03:48 AM   #1
bugeyes
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Question A/F tuning on the vacuum side....

Found heaps of detailed info on boost mixtures but I need more info on vacuum manifold pressure mixtures.
I have searched this topic and it seems many comments are just to run 14.7-1. You guys that have standalone ECU's what mapping are you using for the vacuum side of the fuel map. I suppose you could-

Simply map the entire vacuum map to 14.7-1 as many of the search posts make mention of.
OR
Run a zero manifold pressure of say 13.2-1 tapering off to a maximum lean mixture of 15.5-1. With a general cuise mixture close to 14.7-1
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Old 06-13-2006, 02:24 AM   #2
rac
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I'm not saying this is right for you but this is what i run with my Autronic sm4 on my ej257/ver3 sti.
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Old 06-13-2006, 07:09 AM   #3
bugeyes
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Quote:
Originally Posted by rac
I'm not saying this is right for you but this is what i run with my Autronic sm4 on my ej257/ver3 sti.
Could you please translate the load column into vacuum level. It appears the pic you posted also includes boost a/f mapping.
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Old 06-13-2006, 10:44 AM   #4
jblaine
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Here's what I do, for no real good reason other than theoretical fuel conservation:

14.5:1 to 14.7:1 = Idle vacuum and lower, all RPM ranges.
14.7:1 = High vacuum at lower than 3000RPM (very likely the car is decelerating to a stop)
18.0:1 = High vacuum at higher than 3000RPM

Really though, it's pretty pointless if you ask me. How often are you in vacuum higher than idle vacuum? Shifting, engine braking. Woop dee doo.

Tune it for 14.7:1-ish and be done.
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Old 06-14-2006, 09:32 PM   #5
Jaxx
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a thought and the way my car is tuned (which is probbaly wrong)

open loop i target 12.1 (best lean torque) then and let the closed loop pull it up to 14.7
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Old 06-14-2006, 09:53 PM   #6
bugeyes
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Well after reading the replies I think this is what I will do. Configure the map to 14.7-1 across the vaccum band. Then bring my fuel cut vacuum level up as far as possible so when I hit high vacuum levels it shuts off the injectors. Finally set my closed loop control to about 15-1 (maybe even higher 15.5-1?), so on continuous throttle position such as cruise it tends to lean off slightly.
This should give me a clean, fuel efficient burn (totally the opposite from the boost side)

On boost the map tapers off gradually from zero to give max power under boost conditions.
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