A/F Ratio Help

kornshadow097 · Post by **kornshadow097** » Wed Feb 16, 2011 9:23 pm

I've read that

Any mixture LESS than 14.7 to 1 is considered to be a rich mixture
Any MORE than 14.7 to 1 is a lean mixture.

I also read from the same source that the place that a car makes most of its power is between: 12.5 - 13.3:1

Which is Rich. But on the street I've heard you want to get as lean as possible without actually being so lean that knocks become too rampant.

So which is it? do I want the A/F over 14.7- something else...or should my goal and parameters be 12.5-13.3:1?

One more thing. What makes a car backfire with flames after a shift? Timing,A/F ratio and is it good or bad? My current set up does it with downshifts and hardly ever for upshifts...I'm curious.

Thanks.

Nny

tomzauto · Post by **tomzauto** » Sat Feb 19, 2011 5:44 pm

a 14.7 af will give you less power and give you better mpg

a 13 af will give you more power but less mpg

pm me if you still need help tuning

i tune engines online and have lots of vouches and very fair prices

pm, or text 717-222-8619 if interested

kornshadow097 · Post by **kornshadow097** » Sat Feb 19, 2011 8:57 pm

alright. I know that much. But I've heard many cars tune lean to get more power or torque like actual formula racers end up with a 15:1 when done tuning.

I've tuned up my car a lot, using datalogs but I need to dyno to know for sure.

I'd rather know what to look for in a tune. ive read books and forums and nobody ever seems to be specific or have any actual reasoning or strong opinions.

tomzauto · Post by **tomzauto** » Sun Feb 20, 2011 8:38 am

Nobody tunes lean to get more power, it doesn't work like that, the power is in the rich fuel mixture

keto06 · Post by **keto06** » Sun Feb 20, 2011 8:52 am

wrong. leaner = more power. richer = safer power. Hondas come super rich from the factory under WOT which is why a leaner AFR tune can often result in power by itself!

14.7 is whats called stoich and its the correct fuel mixture for idle/cruise driving. Some people run leaner under light cruise for better highway MPGs, which is up to you, but because I prefer to drive in closed loop, im always correcting for 14.7.

At WOT, extra heat is generated and offset by the added fuel to keep things cooler. Hence why you want an AFR around 12.7-13.2 for NA. Heck turbo guys run as rich as 10:1 on the street.

kornshadow097 · Post by **kornshadow097** » Mon Feb 21, 2011 2:39 am

Thats what I'm talking about. Thanks for the more specific answer.

Alright that makes sense. So how lean is too lean in a k20a2? 16:1?

Because I want it relatively safe but not too safe. I want it as lean as I can without it being just plain unbeneficial and a gas hog and just a over all hazard.

Because I'm sure there is a level where there isn't much power gained and its just unsafe without any actual benefits worth blowing your engine... the temp compensation of adding extra fuel comes into play at higher RPM I'm sure. so there has to be a part of he RPM's where its more beneficial to have it lean and transition into a richer fuel range

any Idea where I can find out more?

tomzauto · Post by **tomzauto** » Thu Feb 24, 2011 10:06 am

keto06 wrote:wrong. leaner = more power. richer = safer power. Hondas come super rich from the factory under WOT which is why a leaner AFR tune can often result in power by itself!

14.7 is whats called stoich and its the correct fuel mixture for idle/cruise driving. Some people run leaner under light cruise for better highway MPGs, which is up to you, but because I prefer to drive in closed loop, im always correcting for 14.7.

At WOT, extra heat is generated and offset by the added fuel to keep things cooler. Hence why you want an AFR around 12.7-13.2 for NA. Heck turbo guys run as rich as 10:1 on the street.

here i copied this from the hondata tech page on tuning for fuel

The general approach tuning mixture is to adjust the injector multiplier (overall fuel trim) until the mixture is as close as possible to ideal while the engine is under full load. Normally this will result in the part load settings giving close to ideal mixture as well.

The ideal mixture at full load (for a non boosted engine) is a matter of option but generally lambda 0.88-0.92 (air/fuel 13:1 - 13.5:1) produces the most power. Measurement of the mixture is best achieved with a wide band lambda meter. An exhaust gas analyser may be used, but tend to have a slow response time (although they are more accurate than lambda meters).

With forced induction the ideal mixture will be a richer under boost. Generally lambda 0.82-0.86 (air/fuel 12:1 ö 12.6:1) is suitable for a boosted engine. For engines with a detonation problem richer mixtures can be used.

Once the overall mixture is close to ideal, the fuel table should be adjusted to give an even mixture spread for each cam. The best way to do this is to select the whole of a table (ctrl+A), then apply a percentage adjustment to the table (J).

For stock engines often adjusting the injector multiplier and adjusting the high speed cam table will bring the mixture close to ideal. Otherwise it is best to select portions of the table by revs and adjust the mixture using the adjust function.

As a check as to whether the mixture is correct for full load and throttle two dyno runs can be made with 2% more and 2% less fuel. If the mixture is correct then there should be very little variation in power.

kornshadow097 · Post by **kornshadow097** » Fri Feb 25, 2011 1:18 am

cool, thanks for that post. I appreciate all the help n info you've given me.

kornshadow097 · Post by **kornshadow097** » Fri Feb 25, 2011 1:29 am

I just noticed something in your post.

What is an injection multiplier?

thanks