This is topic optimal a/f ratio in forum Tech Talk at Northern California Ford Owners  .


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Posted by z ya (Member # 1327) on :
 
What is your opinion on what is the optimal a/f
ratio for n/a motors? I read that Edelbrok feels
that 12.5 is the number to shoot for. Then I read
that LaRocca feels that 13.5 to 14.5 is the way
to go. My a/f on my z was 10.0 across the board.
That sucks big time!
 

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Posted by shade-tree (Member # 298) on :
 
14.7 for efficiency, a little richer for power, 13.5 sounds right to me, but I'd ask Byron
 

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Posted by st5150 (Member # 51) on :
 
I believe Edelbrock must be claiming 12.5 for nitrous use. Aim for 13.0-13.5ish and you'll be fine. 13.5 around your tourqe peak and slowly fattens up as the RPM's climb to about 13.0ish.
 

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Posted by yellow67stang (Member # 903) on :
 
10-1 is a little fat! thats what we were shooting for on the dyno when I was throwing a lot of n2o at my motor.

You really need to hit a dyno and spend some time to find out where your motor A/F ratio is best. And you also have to figure out if you want to keep it conservative or lean it out a little for more power. If you play with it and read your plugs you will find it in no time.

Eric
 

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Posted by customN2O (Member # 914) on :
 
Im really curious as to why you chose to go with 10.0 A/F so you could add alot of nitrous? Why did you do that? Dont say to be safe, cause your motor A/F ratio has nothing at all to do with the nitrous. You need to tune the motor as best you can, then get the nitrous correct. you are hurting yourself by doing it that way. Only makes things worse. Tune the motor, and when that is optimum, start tuning your nitrous. Never tune motor to correct a nitrous problem, or you will get burned. There is alot more to it then that, but thats the basics of it.
 

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Posted by shade-tree (Member # 298) on :
 
dude, he's over-rich and needs to fix it
 

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Posted by yellow67stang (Member # 903) on :
 
Well, its not a "wet" system Scott. I get my fuel enrichment by increasing the fuel on the injectors thus making the ratio really "fat" when it is just motor. The V/E has a lot to do with the tune. EFI is a wonderful thing!
 

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Posted by z ya (Member # 1327) on :
 
Yeah 10 to 1 is gross I know! How much hp do you
think I can pull out of it if I go from 10.0 to
13.5? Ralph said I had alot left to go in the motor. I guess it helps to bring your jets with
you!
 

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Posted by st5150 (Member # 51) on :
 

quote:

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Originally posted by z ya:
Yeah 10 to 1 is gross I know! How much hp do you
think I can pull out of it if I go from 10.0 to
13.5? Ralph said I had alot left to go in the motor. I guess it helps to bring your jets with
you!

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Going from too lean to "ideal" makes more power than going from too rich to "ideal". I hope that makes sense. With that said, I'd guess a 17 RWHP gain
 

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Posted by I like to race (Member # 1484) on :
 
YellowStang,

Doesn't FAST have a nitrous option that only increases the pulse width when you hit the nitrous???
 

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Posted by z ya (Member # 1327) on :
 
Thanks st5150, I am hoping to pull around 20 to 25
more out of it. More timing,no air cleaner, and
proper a/f !
 

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Posted by yellow67stang (Member # 903) on :
 
Yes it does "i like to race". when increasing the pulse you are adding more fuel which changes the a/f ratio right? I am by no means an expert on this but I believe my EFI guy just used the A/F ratio as a gauge to know when the car had enough fuel to add the n2o.
 

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Posted by st5150 (Member # 51) on :
 

quote:

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Originally posted by z ya:
Thanks st5150, I am hoping to pull around 20 to 25
more out of it. More timing,no air cleaner, and
proper a/f !

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You could very well get 20+ rwhp out of it, but who knows until you try it. As for the air filter... my buddy tried it on his big block and gained ONE rwhp. I'd try playing with the timing rather than the air filter. You should be able to get away with a tad more timing than you normally would because of your fat air fuel ratio.
 

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Posted by z ya (Member # 1327) on :
 
I timed the car when I got home and I only had
32 degrees total. I bumped it up to 36 total.
Small block chevys seem to make the most power in
the 35 to 36 range. Took it for a ride and no
pinging at all. Should be fine with alloy heads
and 10 to 1's.
 

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Posted by I like to race (Member # 1484) on :
 

quote:

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Originally posted by yellow67stang:
Yes it does "i like to race". when increasing the pulse you are adding more fuel which changes the a/f ratio right? I am by no means an expert on this but I believe my EFI guy just used the A/F ratio as a gauge to know when the car had enough fuel to add the n2o.

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