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My data acq is telling me I am losing big HP after 5800rpms. This is also confirmed by studying video - especially starts - I lose several car lengths starting @ about 6000rpms.

I also had one race where I started on the pole and then even the slow Gen 2 cars are passing me. Motor sounds fine, just does not produce any power - in this case, even at low RPMs. After about 5 laps, all the HP comes back, I started passing everyone and lap times come back to normal. Only happen once after an oxygen sensor calibration. Not sure if it is related to loss @ high RPMs?

Anyone have any thoughts?

I have never heard of that with Gen 3. But I did experience this when I purchased a new Gen2.

After about 3 weekends on our brand new gen 2, we had this happen around 4800 rpm. It actually seemed like the car went into rev limiter mode. We fought this for the entire first year of the car and was so frustrated with it that we took both cars to the runoffs and ended up using a backup car.

We did everything Enterprise asked us to do and finally that winter, they told us to send in the entire wiring harness. They found that certain wires were not properly shielded causing a rev limiter response even though the gen 2 didn't have one. After we got the harness back no problems.

It would appear your problem is electrical in nature. Gen 3's do have a limiter. Mike wasn't at Enterprise when this occurred, but he has helped me in many situations.

Give him a call and my guess is he will be able to help you. Even though our problem was Gen 2 it might be a place to start. Rev limiter? Wiring? ECU?

Good Luck and let us know what you find.

Pat

Download and check your ECU data for any anomalies in the sensor readings that correlate in your drop in performance, especially around engine timing and O2 sensor. I had an intermittent issue with the O2 sensor that manifested itself as a significant reduction in the Lambda number, going full rich, which I assume is a safety default. The rich mixture caused a significant drop in performance and fouled the plugs, so even after it was fixed I needed to change plugs to get back to normal performance. Since at least the last hour was logged in the ECU any drop in performance should show up along with any other sensor reading that go off from the norm. Timing is another area where a sensor failure can cause a drop in performance. You may want to check all your sensor connectors to make sure they're fully seated as the timing sensor is particularly difficult to get fully seated.

Thanks Breton, my Lambda stays at 0.68 - which I assume is full rich - is that what you saw?

I will check all the sensors. Where is the timing sensor?

It's the O2 sensor (or wiring harness). Check the connector first, as that's the weak point. It takes a short time for it to read normally (assume the O2 sensor has to heat up before it gives a good reading.) I assume if you've changed sensors that you've gone through the recalibration process. If you ran a while in that condition I highly recommend changing the plugs (they're likely sooted from running rich). Should fix the problem.

I was referring to the crank sensor connection under the engine near the starter...

Steve-I sent you a pm. Let me know if you got it. Dave Skinner

Thanks, Dave - I got it. Appreciate your input.

I think the problem is the Oxegen sensors. My header is cracked, so I need to re-weld before I can test. Will keep you posted.

I am going to look at the intake manifold at any rate.