How rich does a stock EVO8 run @ WOT? I know that some of the newer F.I. cars are very rich, with the Cooper S around 8.5:1 and the WRXs around 9:1, @ WOT.

I suppose car mfgs do this to keep the cars safe, but I can't help but wonder if they would make more power by leaning them out?

Currently, my 4G63 (winter beater) knocks too much at anything leaner than about 10:1. This seems too rich to me, but maybe these Mitsu engines like life in the "rich" lane

 

(sorry).. whats WOT?

 

They are richer than 10:1 stock. I'm currently tuned to 11.7:1 on pump gas, and still see 23 degrees of timing at WOT. If you are getting large amounts of knock at 10:1, you've likely got a problem somewhere. Have you done the fuel pump rewire mod? What mods are on the car?

 

My stock Evo went "off the chart" rich (richer than 10:1) from 5700 RPM to redline when I dynoed it. At the torque peak at 3700 RPM, the A/F ratio was about 12.4:1. Just short-shift to avoid running too rich.

 

10.5-11.1 seem to be a good poing to run for daily driving on pump gas. That is what I run with 93 oct and a max of 18.5 to 19.5 psi.

 

WOT = Wide Open Throttle

 

Thanks for the reply. It is very interesting to know that these EVO8s run richer than 10:1. Safety reasons I guess?

I don't want to get too OT, but since you asked...it is a 1G DSM, EVO16g, 550s, 255lph pump, etc. 17-18psi on 94oct. Anything leaner than 10:1 and I get some knock. My guess is the stock I/C is keeping the intake charge too hot and the rich mixture is needed to keep it from knocking. It runs well and make decent power, but 10:1 seems very rich!

 

isnt air/fuel ratio for max power 11 to 1?

 

get a wideband, and some type of fuel management.....i will shortly and take my WOT rich blues away...heh.

 

You have all the right mods, you shouldn't be knocking very much. You say you're some knock. How much is *some*? Ditching the SMIC will help a lot. What are you using for fuel control? 1g's are notorious for having phantom knock caused by noisy lifters, have you looked into that?

 

It all depends on the car and altitude you are at. My car is tuned at 12.1 (6000ft), runs great. Ran below 10.1 stock.

 

Old thread Your suggestion of 10.5-11 sounds nice and safe to me. I wonder if I can lean the EVO out to about 11.5:1 @20psi on 91octane?

Probably more important >>>>> What power gains are people seeing on the dyno from going from about 9.5:1 to 11:1? IMO richer is safer for extended WOT runs so I am not going to lean it out much for 5whp!

 

To lean the car out to 11.5 is possible but it is going to depend on the car, every EVO acts differently. Honestly I wouldn't for everyday pump gas even on 93 oct, I see to many differences in pump gas. If you are on the stock ECU it may not do you any good because the more fuel you pull the more active your knock sensor will get so in this case it could just result in pulled timing, once again it may or may not but I am sure you would rather be safe than sorry. I run the AEM and 11.1 provides the safest tune for my car where I can run average timing without knock and be well into my safe zone all the time. The gas here isn't very good either even though it is 93 but the car still produces good power and I have no worries for everyday normal or hard driving. Leaning it out from 11.1 to 11.5 would only be at the very most 5hp if even that. Timing advance will make you more power than a leaner fuel mixture in the 10.5 to 11.5 range. Also running 20 psi on 91 I wouldn't recommend, on the stock 16g you will read several people running more than 20 psi on pump but you will also read some that have bad results down the road. The stock evo motor is very good but it still won't take but an instant to pop one from knock.

For extended runs richer is safer but remember richer won't help you if you heat soak the FMIC so keep this in mind. For extended runs stick to 18-19 psi and 10.5ish on 91. Other wise 11.1 at 19psi or be sure you are falling to 19 or below at redline. This is just advice that I give from the experiences that I have had with a few evos that I have tuned or took part in tuning so I hope it helps. Just remember to tune where you feel absolutly secure so when you walk away you don't have any questionable thoughts.

 

GTVEVO, a big thank you goes out to you! Your post is one of the most informative and useful I have seen in a long time...too bad more people don't share your knowledge and willingness to help others.

Your A/F advice makes a lots of sense to me and was exactly the info I was looking for.

To recap, here I what I got out of your post: On questionable-quality 91-93 octane pump gas the upper "safe" limit is probably around 19-20psi and 10.1-10.9 A/F. Even *if* one wanted to lean it out into the 11-11.5 range there is probably very little extra power to be gained. Maybe the Mitsu engineers were onto something when they tuned these cars to 9.X:1 from the factory? They weren't after every last ounce of power but they wanted the engines to last, same as what I am looking for.

No doubt there are some out there that run more boost and/or less fuel (stock turbo and internals) but those people might be living on borrowed time My car isn't a 1/4 mile Queen but rather a mean street car, AutoX and track day junkie that sees WOT for extended time, like about 25sec on a long track straight and more on deserted roads at 140pmh+

I will stick to the ~10.5:1 area and no more that 20psi. Hope the engine lives a happy life there.

 

you could always use water/alky injection to compat det. and high egts, then lean it out, using the water/alky when needed. most standalones will acomidate WI (as well as some other interesting fuctions) or you could run a presure poerated system.

ifyou where going to build your motor then i would say get as much of the chambers TBC coated as poss. these coatings will let you up the det. limits and make the whole engine much more robust, whitsanding lean moents much better than not coated engines.

thanks Chris.