# simple A:F question



## Murph (Aug 8, 2002)

im going to be running my car for awhile without a turbo. Now, with an s'afc and a wideband, should I be aiming for 14.7:1 AFR? Or whatever stoich is. It seems like everyone goes for a richer mixture, but maybe its because im always hanging out in the forced induction sections everywhere.

Just thought I would check!

Your thoughts?


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## James (Apr 29, 2002)

running slightly leaner usually will net more power... but you should do all your tuning on a dyno.


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## Murph (Aug 8, 2002)

whats wrong with basing it on the wideband readings?

slightly leaner than 14.7:1???


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## James (Apr 29, 2002)

so you know when you're getting the most power in each rpm


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## Murph (Aug 8, 2002)

I sense a circular statement here. :cheers: 

I need power! And fuel efficiency. Both point to a leaner mixture than stock. How much hotter does 14.7:1 burn compared to lets take a guess on the factor mixture and say 13.8:1.

Did anyone here possibly run an EGT guage on a N/A application like this?


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## James (Apr 29, 2002)

http://www.nissanperformancemag.com/may03/project_qg18de/

that may answer a few of your questions.

the goal of tuning with the SAFC is to be able to change the mixture in various RPM's right? so if you set it to be at stoich. in the whole rpm band you would gain power in some places and lose in others... where if you're on a dyno you can lean it out or richen it up and see the results on a graph...


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## Murph (Aug 8, 2002)

Great, thanks James, I forgot about that! When I read it before I didnt realize different mixtures at different RPMs would be benificial. Thanks man.

I wonder if Keith Sipmann has any additional dyno information that he pulled from that. Is he on these boards?


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## James (Apr 29, 2002)

np...

so your car was turbo but you're taking it off?


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## Murph (Aug 8, 2002)

Nope. Building up the fuel size, then the the rest of it sometime next summer. Im looking forward to 6-8psi or so of t4 sugar.


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## morepower2 (Apr 19, 2002)

Murph said:


> im going to be running my car for awhile without a turbo. Now, with an s'afc and a wideband, should I be aiming for 14.7:1 AFR? Or whatever stoich is. It seems like everyone goes for a richer mixture, but maybe its because im always hanging out in the forced induction sections everywhere.
> 
> Just thought I would check!
> 
> Your thoughts?


No you
will blow your engine to bits if you try to tune for stoic at full throttle. 14.7:1 is for idle and light throttle cruise only.


If you are planning turbo then on pump gas your a/f ratio should be in the 11-12:1 range.

What kind of engine do you have?

Mike


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## Murph (Aug 8, 2002)

Mike,

Im going to be running N/A on my 95 KA for awhile. _So, im looking for something to aim for._ I do appreciate your comment on the 14.7:1.

Is there a specific mixture that is generally desirable for N/A applications? Or does the ideal in fact vary by engine speed as I understand it to be?


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## morepower2 (Apr 19, 2002)

Murph said:


> Mike,
> 
> Im going to be running N/A on my 95 KA for awhile. _So, im looking for something to aim for._ I do appreciate your comment on the 14.7:1.
> 
> Is there a specific mixture that is generally desirable for N/A applications? Or does the ideal in fact vary by engine speed as I understand it to be?


Best power is going to be between 12.5:1 and 13.3:1, of course leaner than 13:1 is somewhat risky.

Mike


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## Murph (Aug 8, 2002)

awesome, thanks again Mike


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## jetsam (Feb 7, 2004)

morepower2 said:


> Best power is going to be between 12.5:1 and 13.3:1, of course leaner than 13:1 is somewhat risky.
> 
> Mike


I've seen dynoplots showing A:F ratio of the nissan maxima equipped with the Jim Wolf ECU. It looks like 14.7:1 is held all the way to red-line, while the stock ecu brings A:F down to 14, then 13, then 12, and so on as rpm rises. Care to comment on this?


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## morepower2 (Apr 19, 2002)

jetsam said:


> I've seen dynoplots showing A:F ratio of the nissan maxima equipped with the Jim Wolf ECU. It looks like 14.7:1 is held all the way to red-line, while the stock ecu brings A:F down to 14, then 13, then 12, and so on as rpm rises. Care to comment on this?


Dynojets a/f meters are notoriously inaccurate. The JWT is about 12.8 or so all the way and the stock tapers to the mid 10's.

Mike


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