[s-cars] Power Cut for 1 second

[manuelsanchez at starpower.net]

Fellow S-heads,

Power seems to be cut for 1 second, the time it takes you to snap your fingers, under Wide Open Throttle. This only happens when at the track, which by the way was a blast as usual, even in my 4,000 lb pig. It doesn't always happen during a track session, sometimes it happens multiple times (say 6 times or so) during a track session.

This problem has not been experienced on the street, ever.

Strangely, there was one particular part of the track where this problem occurs, it is a very slight left hander, I'd say 10 degrees of turning on the wheel. But....it also happened on the back straight, and at another part by at a short straight just coming out of a right hander. It doesn't happen when backing up  :-). 

After the problem occurred on one lap in a particular location I would not try to use full throttle at the same location on the very next lap, result was no power loss, hiccup or whatever you want to call this annoyance.

Here is a list of what's new in the last 100 miles:

Plugs (the Bosch tri-electrode copper plug Javad sells, previous plug was the OEM Bosch F5DPOR)
Coils and cables (034 DIS system)
Fuel Filter
Fuel Pressure regulator (adjustable)
Fuel Pump (044)
Car has 125,000 miles on the clock

I don't think it was bad gas because it happened both when I filled up with 93 Octane at the local gas station, as well as when I filled up with half 93 and half 100 octane Sunoco at the track pumps. 

I checked the plugs at the track and they looked fine, no real residue yet, they pretty much looked new (well they had about 300 miles on them when I checked them). The old plugs I pulled out had a very slight dpec on white at the  tip of the electrode, which I understand may mean it was running slightly lean. It was at this time, a week before the track event, that I swapped all the fuel and ignition items listed above. 

On an interesting note, before I swapped all this fuel and ignition stuff I attended my first dyno day on a dyno-dynamics dyno. The tech running it said my air fuel ratio was very rich, 9:1 (it was measured by a tailpipe probe), and my ATW power was lower than I was expecting, 209hp/245 ft lb torque (i'm essentially at sea level). I think guys with similar RS2 set-ups were getting about 60-80 units more at a Dyno session on the west coast a year or 2 ago on the same type of dynodynamics dyno. I had always heard that Mihnea's software ran rich. I emailed Mihnea and he thought those numbers were a bit too rich. When he tuned the car it didn't have the stromung, FMIC, nor the new FPR, FP.

I checked the electrical connection at the MAF and it looked brand new, no residue or visible wear on the connector plug.

Fuel pressure at idle was 3.9 bar.

This past Thanksgiving at the same track I had occasional power hiccups as described above, but instead of a 1 second cut of power, it was a series of stumbles, it was an audible braaaaaappp, that lasted 2 or 3 sec. This was with a relatively new coil pack (less than 10,000 miles), original POS's as far as I know, and relatively new plugs at the time.  Last November I was convinced it was ignition related, as the first time it occured was after I removed the coil pack and laid it on the throttle body in order to check plug tightness. My next run after that check was the first time I had the stumble/ braaap. I thought at the time it was something with the wiring and the coils thaqt I disturbed when I twisted the coil pack to lay it oon the TB.

The stumble/braaap didn't always happen, but it happened enough to piss me off.

I know I'm down on power, as I go to these events with my brother in law, who has a stock BMW 540 (280hp/310 ft-lbs at the crank).  When my car was running fine, say 2 years ago, I would pull away from him on the straights and I had lap times 6-10 sec faster than he did, now he pulls away from me on the straights and we maintain our relative position on the track for each lap. I suppose he could be getting better and I could be getting worse, but I think it's a power thing.

Last year I found and fixed my boost leaks by replacing many of the OEM hoses in those hard to reach areas. Car has Samcos elsewhere.  I have pressure tested the car to 15 psi and no leaks that I can hear.  The car seems to make plenty of boost according to my VDO gauge but it doesn't feel like it's giving it's all with regard to acceleration.

Other info on the engine:
RS2 turbo, RS2 manifold, Lucas Delphi 37#/hr injectors, Mihnea Cotet custom software (tuned at PK's house in CT), Tom and Marc FMIC, Forge 007 BPV (2 years old), RS2 WGFV (2 years old), Stromung.

So what's going on? Is the ECU detecting knock and cutting power? 

I'd really love to solve this one so I can smoke Bro-in-law.

Manny "perplexed and wanting all of Ms Piggy's Go back" Sanchez