Rented one of my 2 SRFs for the MVP Track Time event at COTA this past weekend. Took both figuring I might need the spare or somebody would blow up and want to salvage the weekend. Before lunch on Friday I had a customer for the second car... first two sessions out it was stumbling on all the straights. By the end of the weekend it "improved" to only stalling/cutting out completely on the long straight in 4th or 5th gear (usually just 5th) and ~5,000-5100RPM. As I did the following, the cutting out/stumbling improved greatly until Sunday morning when it died completely and wouldn't refire. After getting back to the pits, wiggling some wires, and playing with the throttle cable while cranking it eventually tried starting, then re-fired, and eventually drove around the paddock and onto the trailer.

-swapped relays between the cars.
-swapped computers
-new fuel filter
-new plug wires
-ran a bolt through the leads on the master switch (it only had leads on the large posts...)
-fuel pressure test (~25mL in 30 seconds at idle)
-alternator functional, maybe slightly high voltage, maybe due to everything being tied together on the master switch?
-at some point found the 2 20A fuses were blown/melted
-"cleaned" MAF

After talking Tom Dalrymple's ear off for probably an hour over the 3 days (THANKS AGAIN, TOM!!) the only thing I haven't swapped or replaced is the coil pack and MAF. Anybody had this experience before, chased all this stuff down, and have any advice? It wasn't anything like a fuel starve that I've experienced before. Usually in the top of 5th when the car is about at terminal aero velocity, power would just immediately cut out, the car would get squirrely, and it would either come right back on, or I'd cycle the dash switch and it would be fine for the next ~500 yards to the braking zone for T12. I kept the cell topped up all weekend, replaced the fuel filter, and the flow test shows brand new pump volume so I'm fairly certain it's not fuel delivery but electrical.

Did it get worse in-session?
The symptoms (assuming that it worsened) mimic that of vapor lock at the pump. It seems unlikely, given some of the things you mentioned, but we have seen that before down here on warm weekends in Feb. What was the temperature?
Especially the "after it sat for a bit, it fired up and I drove it to the trailer".
If it did not get worse as the session went on, then that's likely not the culprit.

Do you have a fuel pressure guage that you can attach and run for a session (data acq if you have it)?
I recommend that as number 1 on the data acquisition list. Reason being is that a trace of FP (or even eyeballing it when the issue happens) can eliminate a ton of possible causes for these types of symptoms.
Denny

I didn't hear you mention replacing the fuel pump. 25ml in 30 seconds at idle? That doesn't make sense (that's less than an ounce.) What was the actual fuel pressure and did you do the Enterprise's-recommended fuel flow test? The old volume test missed the fact that as the fuel flow builds a bad pump will no longer pump the spec volume. I've seen the flow on a bad pump and it often shows a lot of bubbling during the flow test and the result is a "flattening" at the top end on a longer run (the unlucky ones end up with a blown engine due to a lean mixture.) Either an FP or AF meter should help in that diagnosis.

I think the 25ml must be a mis-type, at the end he says it passed the flow test. Usually fuel flow-related sudden cut-outs do not restart and result in things like smashed spark plugs and melted metal.

The blown fuses / sudden cut-out make me think it's electrical. I would check the wiring around the alternator / heat shield. There are a lot of sharp things in that area than can push through insulation when things get hot.

Dave

It's the stumbling that seemed odd for an electrical issue; electrical cutouts are usually more abrupt and don't generally show up in straight line runs (but I wouldn't rule anything out, either.) Spiking alternator can do strange things as well (like send the computer into "default" mode). Given the note of higher voltage that's suspicious as I would expect voltage to drop, not go higher, if the connections are cleaned up as the alternator is getting a truer voltage reading. If the voltage from the alternator is over 14.5v that could be an issue as well (I've seen bad one spike into the 15v+ range). Never saw 2 20amp fuses blow unless there's a serious short somewhere. Guess I'd throw the master switch into the list as well.