Toilets

Was at the track this past weekend and my 3rd to 4th gear lag has seem to have gotten worse.

Basically there is is a slight hesitation (like a sputter type feel) when you shift into 4th gear. After the hesitation, the car feels to have fallen on its face. I did some comparison to other videos people have posted including lawdogg Ra video, and noticed the average time it takes a M7 to go from 120mph to130 mph in 4th at WOT is roughly 2 seconds. My average is 4 seconds. It's quite literally going up 1 mph at a time. Does anyone have any clue what I can check?
I do TT racing so I do at max 5 laps at a time . The issue came and went but it happened in 1 lap or another in all my sessions. Coolant temp never saw over 225 based on the data, and oil temp maxed at 259.

Engine light did come on the last session of the weekend and it killed the power. Culprit was P1101 which is the MAF sensor. We pulled it and there was some kind of dirt (see pic) . I know that was the reason for the limp mode last session given the engine light and limp mode but could the car restrict power and not throw a code for this sensor in the previous sessions?

fleming23

Mine appears to be more like 4 seconds as well. I have compared my videos to others, Jeremy's included, and I attribute it to ambient temps of 90+ as I did not feel my car accelerated nearly as hard as others on the same track but at different times of the year.

Toilets

I would have concluded that also however I am seeing the differences in the same session.

Example:
2nd race:
out lap
lap 1. Max temp 208
Oil pressure 54.5
Max oil temp 226
time to take between 120 to 130 after shift is just over 2 seconds

lap2. Max temp 214
Oil pressure 48.7
Max oil 243
time to take between 120 to 130 after shift is now 4 seconds.

It was happening all weekend. One lap it was strong, next lap it felt like it just fell on its face. I then said, well maybe timing is being pulled or something and then the car does the opposite. Lap 1 fell on its face then lap 2 it felt completely normal. It's frustrating because nothing is consistent. I was seeing up to 10mph top end swings on the front straight with the same entry speed to the MPH.
Tale tale sign was when I did my record lap my entry speed was 4mph faster than any other lap, it fell on its face and still was 8 mph slower as to my best top end that day.
I measured by two exact points (entry and just prior to braking zone)

phantasms

Sorry to dig up an old thread but did either of you guys ever figure this out?

I was doing research on the P1101 code I got when I went to the drag strip. A battery reset seemed to "fix" it. My car at the strip felt underpowered and in very good DA with excellent track prep, a good driver, good engine temps, and CAI my car was only running ~122mph. It drove me nuts. The car pulled much harder on the street on the drive home with a passenger than at the track

Thanks!

Best,
Gene

Toilets

I replaced the MAF sensor and haven't had the P1101 code however we are still fighting power loss issues. We did some fixes and go to Rd Atl this weekend so hopefully can report back with a positive response.

phantasms

Fantastic. Did you replace with Factory sensor or go aftermarket? Good luck or there!

Toilets

Just the factory one

Bill Dearborn

I went back through some of my videos from Watkins Glen and VIR this year. In 4th gear my car will accelerate from 120 to 130 in 2 to 3 seconds. This is going up hill. The hill at the Glen is a little steeper at the beginning than the hill at VIR at the beginning but tends to flatten out while the hill at VIR gets a little steeper as you drive further.

Have you tried shifting the transmission a little sooner so you are shifting from 3rd to 4th at 6K or 6.2K rpm rather than right at the 6400 rpm which is where max HP is produced but only 100 rpm below the rev limiter cutting in. Given there is always some tach readout lag you may be actually getting into the rev limiter just as you shift and that could cause the engine to stumble a little bit in 4th as the clutch is let out.

Bill