Running way rich.

[Keith Carter]

Before the race last weekend we installed a Lambda sensor and calibrated it as we were supposed to before putting it in the collector. At idle it was running rich , but as it was explained to us it was because of the map to improve paddock/starting performance, etc... So we got out to Road America and in the first session going into T5 we were at 6015rpm at full throttle and had a Lambda of 0.771. Heading into Canada corner were were at 6100rpm and had a Lambda of 0.742. In another lap we were at 0.827 going into T5 and 0.799 heading into Canada. So we are obviously rich, but is variance from lap to lap with similar rpms normal? In any case, we backed off the fuel pressure as low as it would go which was only 2 psi less than what were previously had. In the next session we were at 0.833 into T5 and 0.860 into Canada. With the optimal being 0.880 and with us being all the was down in fuel pressure, is there something that could be causing us to be rich out of the range of the fuel regulator? We've been advised to take apart the regulator and clean it to make sure there isn't any crap in it causing the pressure to increase, but is there anything else that could be causing the mixture reading to be rich? Injectors? Coil? Fuel pump? We're running non-oxygenated BP pump gas and have changed the plugs and wires and have cleaned the air filter before installing the Lambda sensor.

[sracing]

Optimum performance will be between .85 and .90. (a/f ratio 12.5-13.2 : 1).

However this is only with no throttle transients. IE. At WOT for a few seconds.

If you are doing that correctly, it is most likely a fuel regulation issue. It would also be helpfull to see a graph of WOT a/f from 4000 RPM to RedLine. I would log the fuel pressure.

Misfires can of course cause bad readings, but you would probably have felt/heard this if it was enough to screw up the readings.

Also can I ask what type of wide band 02 system you are using? Some wide bands systems are poor at temperature compensation and repeatabilty.

Based upon your numbers you were sometimes down into the 10.5 : 1 area. You will be down as much as 10% HP and any lower and you would be prone to misfires.

[Keith Carter]

We're using an "Innovate Motorsports LC1 Lambda Sensor" that we got from Veracity. Here's a snapshot of what I'm referencing.

[sracing]

That is your problem. You didn't buy it from us.
Seriously, the Innovate unit is fine (we use 2 of them on the dyno here.)

Ok, looking at your graph it appears to be just about exactly where the manufactures leave a stock ECU burn for WOT. When we tune a car we change the map to lean it up to the range I described. Of course in your class you can't re-map. Assuming it is legal, decreasing the fuel pressure is all you can do. I am afraid I have never looked at a A/F run on an FE, so not sure if you are abnormal, but I can tell you this graph pretty much is precisely what a stock WOT a/f map would look like. The manufactures leave them relatively rich to protect them. Lowering fuel pressure or changing fuel SG is about all you can legally do.

[Marshall Mauney]

Keith -

That trace doesn't look right - there should be a trend leaner as you hold the throttle down for long straights. I'll try to get a screen cap of mine from the last race and PM you. I missed the setup (too rich in qualifying, loo lean in the race), but it will give you an idea of what it should look like.

[iamuwere]

What pressure is the "lowest you can go" as you are measuring?

[Keith Carter]

We install the fuel pressure gauge only to take a reading and remove it before racing. As low as we can go on the fuel regulator is 30psi when the screw comes off the diaphragm. We were at 32.5psi or so before.

[Marshall Mauney]

That's pretty low - I know I was running higher than that on the same day (same fuel, too) and I was actually a bit too lean.

[sracing]

Not to be insulting, but you did free air calibrate the LC-1 right?

Jim

[Keith Carter]

Yep. Did it before installing it in the collector. Everything happened as it said it would when we calibrated it so I can only guess that I did it right with the series of button pushes. Should I calibrate it again? Would I need to calibrate it at every race weekend?

[sracing]

Normally unless you change the 02 sensor you don't have to re-cal very often. But if you set it up with the calibrate switch, I would do it before each weekend. (make sure your pipes are clear of any exhaust gasses before you do it.)

[KAMcDonald]

i get similar results. have the lambda1 with my AIM unit. setup for it using either all gas or 10% ethanol, when running at 39psi was showing in the .77 range. did same thing, lowered pressure till the screw came out, still in the lower .8x range.

did not really see any improvement in acceleration, so playing it safe, went back to 38 psi and decided to live with it.

[sracing]

That is what I expected. These readings are close to the stock ECM map burn. Lowering the fuel pressure will get a/f closer to optimum. One caveate is that when you get down to the 30psi pressure area the injectors may not atomize as well,depending upon design.

Jim

[iamuwere]

Running an AIM LCU-ONE, track 100 unleaded I am able to get a 0.85-0.9 with about 36 psi. Most current ECU map I am aware of.

jim

[sracing]

Running an AIM LCU-ONE, track 100 unleaded I am able to get a 0.85-0.9 with about 36 psi. Most current ECU map I am aware of.

jim

That is just about perfect for WOT. (A/F = 12.5-13.2 : 1

Jim