AFR Compare.. Do I have a Problem?

[robertsmb]

ok I need an analysis because something is bugging me.

I was ordering my CT27 upgrade from ATS racing, and their dyno page AFR caught my eye.

Their car goes from lean to way way rich just like mine does, but way way later... like its a pretty slope from 15:1 to 10:1 all across the RPM range.

My Dyno (the top one) falls directly off the page at 2500-3000rpms to below 10:1?? What could be causing that, and how can I fix it?? Why doesnt my AFR drop normally like the ATS graph??

Please Compare these 2 graphs. If you compare the Power from the 2 dyno runs,.. my power at 152 and their power at 151 are very close to each other, and judging by that I could say that the cars were pretty much in similar shape at the time of the dyno...

so what could cause my AFR to be stupid like this, and theirs to be nice and neat??

[JekylandHyde]

The ATS graph's A/F is from the CT27 they tested, not the CT26 they tested -- notice the color of the lines. That red A/F line can't be right BTW - something is goofy there.

At any rate, neither of you have a "good" A/F going on.
As noted on their Site, that was as tock car that they threw a CT27 on to test.
A good tune will have a steady A/F around 11.8:1 to 12:1 while you are on boost.

You can see my tuned A/F here:
http://www.jekylhyderacing.com/image...hp_424rwhp.jpg

As to why their A/F doesn't fall as fast as yours, the CT27 is pushing more air. More air + same fuel = not as rich.

[JekylandHyde]

If you look on the official MR2 records pages:
http://www.mr2ownersclub.com/mr2records/mr2records.htm

You can look at what is going on with different set ups.
A healthy stock MR2 should put out 165 rwhp.

Your A/F does not look any worse than the other CT26s running around 160 or less whp.

[robertsmb]

Ok one more question.

Jekyl, do you know how to tune this car using the APexi S-AFC? Im going ot need some pointers on getting to a starting point. I think I can handle adding a little fuel here and there once I get in the right area, but I need to get to a solid starting point. The power primer didnt really explain in detail how to lean the car out a bit, and im inexperienced with the S-AFC.

Any pointers would be great.

[wvturbo2]

all you have to do is turn the knob to the right to take fuel out push to the right to go up in rpms and take out what you want.... id use a fuel pressure regulator and change that...then afterward correct what extra is needed with the safc...

[JekylandHyde]

Tuning an MR2 with the SAFC is risky business, but it can be done.
The SAFC is a liar. It lies to your ECU about the amount of air coming in and the ECU sends less fuel (hence leaning it out).

On most cars, you can just lean fuel out and that is all fine and dandy.
On the MR2, the ECU says, "Hmmm less air? We better advance the timing for better performance."

As you keep leaning fuel out and the ECU keeps advancing timing, you run the risk of popping the engine. Many, many people have done this, so be careful.

You are much safer leaning the whole graph out a bit with an adjustable fuel pressure regulator and then using the SAFC for much smaller changes in the A/F.

[robertsmb]

I have an adjustable fuel pressure regulator and gauge ready to go on it...

So the S_AFC isnt great huh.... is there another computer that I cna get that is much safer and more user friendly? I can send the S_AFC Back or sell it on Ebay...

[JekylandHyde]

Unfortuinately no.

You either gamble with the SAFC or spend the big bucks to go to a full EMS.

A lot of people have safely and succefully used the SAFC.
You just have to be very respectful of the amount of changes you make with it.

[robertsmb]

by big bucks are you talking Greddy E-Manage, or are you talking thousands of dollars??

There has to be an alternative... i really dont know anything about the S-AFC and I dont want to blow my shit up trying to tune it.

[JekylandHyde]

I am using the Hydra Nemsis which runs about $1500 or so.
www.mrcontrols.com
You would need someone who is capable of doing a full EMS tune.