I have been doing some research and come across some evidence to suggest that a rich (richer than the normal 13.0-13.2 that usually works for most motors) mixture may provide better performance (specifically at the dragstrip) than a leaner one. I have seen 12.5:1 on gas referred to as Max power rich with 13.2 as Max power lean in a couple places. It seems like most people target the Max power lean when tuning but I don't hear too much about Max power rich.

I know each motor is different, you have to tune on the dyno for best power, etc I am just looking for some real world experience from those who have tried a richer mixture. I would be particularly interested to hear from those that have tried different afr's at the track vs. what showed to make the most power on the dyno. I am sure to see the best gains timing would have to be varied to suit each afr but I will take any info/experience you may have.

So lets hear from those of you who have tried a richer afr on an all motor setup - 12.5 afr or richer. Were you able to increase timing and see gains that way? Did a richer mixture make no difference in performance? Did you slow down with a richer mixture? Not looking for a xx.x:1 is best just looking to spark some conversation.

 

12.5 is common at WOT on most of the larger displacement motors i have played with. max whp on my corvette for example was between 12.5 and 13.0 at WOT. i still have to get my newly built b18c on the dyno to see what it likes but that's a common AFR on any 4 stroke piston engine.

 

I have seen all-motor cars like low 12's, I have seen them like mid 13's it all depends on the setup, put it on the dyno and see what she likes!

 

It also depends where you are measuring from, and the type of measuring device.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vw1320 &raquo;</TD></TR><TR><TD CLASS="quote">
I know each motor is different, you have to tune on the dyno for best power, etc I am just looking for some real world experience from those who have tried a richer mixture. I would be particularly interested to hear from those that have tried different afr's at the track vs. what showed to make the most power on the dyno. </TD></TR></TABLE>

The crux of my question is right here - results from the track that contradict what the dyno has shown. I have tried things on the dyno that made power and made no difference at the track and I have tried things at the track that made gains when they showed no difference on the dyno. I get that every setup is different and what works for one motor may not work for another of the same type. I am just looking for some real world experience and some good discussion. I plan on trying some stuff at the track myself but with how busy the tracks are here (lucky to get three runs in in five hours at the track) its not the easiest or most conclusive testing.

Since most people measure all the cylinders at once with a single sensor in the exhaust and are measuring an average of all the individual afr's can a richer mixture help a lean cylinder more than it hurts the others? IE are the net gains from richening up the lean cylinders greater than the losses from running the others richer than optimal?

Does rich with more timing work at the track better than lean with less timing?(assuming both made the same power on the dyno and you have a reasonable safety margin with both tunes)

Again I am not looking for a XX.x afr is best type answer just looking to here some experiences and thoughts. I appreciate the replies but so far nothing has been said that wasn't in my original post for the most part.

 

i was just experimenting w/ this last friday at the track. I had been targeting a 13.0 a/f since starting trackside tunning this season. Friday night i decided to reload a tune which seem to make the most power on the dyno and i ran 1 tenth quicker and 1mph faster seeing the exact same iat's. The logs showed a/fs starting in the 12.5s and steadily getting richer throughout the run ending around 11.3

this was w/o any changes in timing whatsoever. timing is 27-29 deg throughout.

i believe my stock motor likes to be run on the rich side, but i am going to continue experimenting for the rest of the season

 

I've gone to the dyno with a 13:1 CR 13.5 AF street tune, bumped it to 12.8 with no difference in power, so left it there. Compression ratio could be a factor, because some of the 10:1 engines I've tuned liked it leaner.

 

This should be in the tuning forum, but whatever...

You aren't going to see a lot of power change from AFR, especially a close range like that. The benefit is going to be the fuel cooling effect on the motor, since the excess fuel will carry the heat out of the chamber into the exhaust.

Many OEM Hondas run extremely rich on factory maps, the worst I've seen being a stock 2002 AP1 S2000, which dropped off the bottom of my wideband (9:1 AFR on E10) above 7000 on the dyno. GS-R P72 maps also tend to run a little on the rich side at high RPM/WOT.

 

What part of the curve are you talking about? A/F should not be a constant, it changes with RPM and load. Peak TQ should probably be the richest, as the is the best cylinder fill, leaning out as the rev's increase. A day or two on the dyno will help you sort the numbers.

 

i have found a lot of motors to make more power when run rich, or if they dont make more power they atleast make the same power and are "safer"

 

If you're talking about with your current manifold, I totally buy it. It's a problem with air distribution and how the VE is different in the two cylinder banks. Think about it

 

Nothing to do with my current manifiold or even my car at all Paul. Just something I came across at the track and have done some more research on.

Since this got moved from the All-Motor forum its not as clear but I am talking strictly about Naturally Aspirated motors in this case. I agree the power to be found from AFR is minimal but when you can't turn the boost up and are still trying to go quicker you need all the help you can get.

While the dyno is a great tool it is just that a tool. Even a load bearing dyno can't simulate what happens at the track completely.

NAH2B - your results were one of the things I read that made me want to try and find out more. Curious that you had great results going richer up top vs. leaning out as the rpms increase. How much more power did that tune make on the dyno vs. the one you had been running at the track?

 

I couldn't find this thread again after I had posted.

It's definitely interesting and I haven't experienced that before, however I usually don't tune to max power lean afr's, generally I run richer then that, about halfway between max power rich and lean afrs. In general target afr's are around 12.7-12.8:1 at WOT.

Now one question for you, are you running a wideband all the time to see this effect, or are you just getting gains from making the upper end VE bins richer then you were at the dyno with no O2 feedback? I can see if that's true you might be running leaner then intended up top due to air temp or coolant temp effects on fueling that you aren't compensating for all the time. Thus the track condition differs from the dyno and you're having to make changes. If not. . well, got me!

I do know that on my car with the stock fueling curve it definitely does go richer past torque peak. Analysis shows that more or less the fueled VE% stays the same as the actual VE goes down past peak.

There's also run to run variation that's hard to quantify though without a lot of passes, but that's another story altogether.