bluebanana23

iTrader: (26)

what is a good AFR to aim for in the evo? I've heard 11.5 most of the time but I just read the AMS tuner page with the safc tuned to run 12.0.1 is safe. I'l be running 93 octane btw. Right now it's 11.1 with dynoflash.

EVOTEXAS

iTrader: (12)

On 93 octane, which we have, you can safely run high 11's. you can run high 12's on C16 though. You will find that your Dynoflash gives up quite a bit of power. You could gain as much as 50 WHP (on the high side) with a TT flash (for instance). I did. My TT flash is running about 11.7 AFR and when I tune my SAFC to C16 I will shoot for high 12s.

bluebanana23

iTrader: (26)

too lazy to search but how much was it again to be tuned by TT on 2/5? thanks guys

EVOTEXAS

iTrader: (12)

PM sent

EVO8LTW

iTrader: (41)

Cars vary and leaner isn't always faster. AFR is also just one part of the tuning process and needs to be coordinated with amount of timing that you are running. Best thing would be to experiment (within reason) on a dyno, at the track or using some sort of device that measures the acceleration of the car on the street. If you see an extra 5 hp running 12:1 vs. 11.1:1, then maybe the risk of detonation isn't worth it on your car.

DynoFlash

iTrader: (91)

Very inteligent and insightful observations.

I have discovered through extensive research and experience that the vast majority of Evos will experience knock activity and pull timing when running leaner than 11.2 - 11.3

Even though your peak power maybe slightly (READ SLIGHTLY) higher with a bit leaner a/f ratio, your power band will not be as smooth and the pulling of timing under certain load situations will result in a uneven feeling as you pull through the rpms

In most cases, we actually see MORE power at a richer a/f of about 11.1 - 11.3 than we do at 11.5. In other cases, 5 - 10 whp that the leaner a/f taget may achieve are offset by much smoother results and more of a saftey margin for varying conditions

There are many other tuners who choose to run the cars leaner that I do, and it would not involve any technical marvel for me to tune at a leaner a/f target. Most of the cars that you see running big whp numbers on the dyno with a lean a/f will pull timing shortly after they leave the dyno and are driven on the road. This is why I choose to either road tune the car outright or at least do a extensive road test after the car leaves the dyno.

To me, the hallmark of which a reflash is judged is through the TOTAL ABSENSE of any pulling of timing as verified by a OBDII data log driven on the road. A/f ratio is only part of the combination.

EVOTEXAS

iTrader: (12)

And on the other hand there are tuners out there who can run leaner AFs and not pull any timing. Once again, fuel is important. There are other factors involved in tuning than just the AF ratio so let's not get too bogged down.

DynoFlash

iTrader: (91)

Remember, when I am discussing tuning paramateres I am limiting the scope of my remarks to REFLASHED STOCK ECUS on the stock turbo.

Of course, those who are using a stand alone or other piggy back type device such as a UTEC with a user defined knock control set up may push the a/f a bit leaner without running into the timing pulling that you may see on the stock ecu.

Of course, running more knock without pulling timing comes at a cost of reduced margin of saftey and also more stress and impact to the engine.

There is no bright line rule of thumb in tuning, it involves a series of trade offs and compromises. Richer or leaner is not better or worse, each has its own benefits and disadvantages.

While I ran my race car at a nice rich a/f ratio of 11.3 - 11.5 all year, it also was able to make it through an entire season of racing without one tuning related engine failure and also make it into the semi finals on most of the races I entered. Of course, it is possible to run it leaner and make 10 more whp but you wont be winning any races if you miscalculted and blew up your head gasket in qualifying.

DynoFlash

iTrader: (91)

I think that you can best grasp a concept often when it is visualised so I want to offer a few concrete examples of how lean a/f ratios effect tuning and how I can smoothen up the power band and make the car run better with a slightly richer a/f than others may recomend

Here is a typical Evo with an aftermarket intake and a stock ecu which distorts the MAF sesnor reading and results in an overly lean a/f through the meat of the tq curve. Of course this will result in some knock and the very senstitive stock ecu pulling ignition timing



making the car a tad richer makes it smoother but you can see how the slight lean spot really causes knock and timing pulling even one one dyno pass. Aftera few more the timing would be all over the place.



You can see after a properly rich 11.1 a/f ratio the car becomes much smoother and has a much better powerband

DynoFlash

iTrader: (91)

Another example of a very smooth and refined power band at a 11.1 a/f ratio

DynoFlash

iTrader: (91)

Stock 2005 RS with Dyno Flash and 11.1 a/f

EVOTEXAS

iTrader: (12)

So with that said, all this conversation can really accomplish is relating "rules of thumb." In reality, no specific information recieved on the Internet regarding tuning is going to work the same on two cars. Rules of thumb like richer is safer and leaner is more powerful, turbo cars run richer than naturally aspirated cars, etc. So with that, I guess there really isn't too much more to say! All the dyno graphs you post also only mean something to people who also dyno at Pruven in the same time of year, etc. They mean nothing to me here. Anyways....

DynoFlash

iTrader: (91)

Of course - what do I know about reflashing anyway? Here is the USAs' most powerful Evo 8 on a reflash - member Superz who runs the AMS GT35R kit on a bone stock Evo 8 block and head. He runs this car every day BTW with no isssues

Rich = powerful and safe



Thats right 523 whp

DynoFlash

iTrader: (91)

In this case nearly stock evo is making more power running richer

In tuning, I test theories with equipment and measure the results with an objective eye, this is how I come to a logical conclusion

DynoFlash

iTrader: (91)

For those seeking further evidence, backed by actual dyno sheets which you can look at, please do a search on the Dyno Flash section under "case study" tunes - there are 22 of them in which I show exactly how I tune and where the power and smoothness is found relative to a/f ratios on stock ecus.

Here is one more