I have a 997 gen2 GT3, mainly driven at the track. Love the car but have one mysterious issue.

When I downshift to 3rd at VIR at the top of the hill at the end of the backstraight to go down into hogpen it seems like the car goes into something like safe mode. Just has no pickup all the way to turn one. If I keep it in 4th or downshift from 5th to 4th, same problem. No pickup in 4th.

The only thing that solves the issue is downshifting to 2nd. Then 3rd and 4th are fine all the way to turn one. The other curious thing is never have a problem downshifting to 3rd at turn one or oak tree. And if I'm in this safe mode all the way to one, shifting into 2nd at one again solves the problem.

Any ideas as to cause/solutions appreciated.

 

what do you mean "no pickup"

 

You can floor it, it runs but much more slowly than it should. It just lacks acceleration. I can get down the front straight in 3rd, doesn't red line. At one, I'm around 140 instead of 150

 

any sputtering? does it happen elsewhere? is it consistent? when was the last time you serviced your car: plugs, fuel filter, etc

 

Load on the diff maybe? Are you redlining at all prior to the downshifts?

 

Is stability and traction control turned off?

 

Vacuum leak. The turn is pulling at a hose in some way shape or form. Check your exhaust sport valves if you have them, then other vacuum lines.

 

Everything's smooth, just slow acceleration. Only happens at end of backstraight at VIR. First run is usually ok, after that it's a consistent problem. Car spends more time in my mechanic's garage than mine. He can't figure it out.

Something about the long straight where i reach my top speed? The hill at the end? And why does downshifting to 2nd instead of 3rd resolve the issue???????

 

Might be worth running a OBD datalogger to see if any fault codes are happening.

 

end of a backstraight. so, at high rpm/load? do you have this issue at redline in 1st?

first thing i would do is scan the car, otherwise we are just guessing

 

But seriously, if you are sure Stripe isn't hiding under the car, then look for a loose "something" that the hill and high speed could be exacerbating. You definitely want to review the OBD information for stored codes (but I guess there are none if the mechanic has been looking at this). If you can run Durametric and log some live data during a session that could be very helpful. Good luck!

 

I forget if it was hard left or right turns but S2000s used to experience some blow-by only under very specific high-G corners and coming out of the corner you would temporarily have severely reduced power for a second or two and then it was all back to normal. In this case people found oil was collecting on the baffle in the valve cover and then getting sucked out (or maybe in) the PCV. Most people got around it via some form of a catch can setup or drilling a few holes in select areas of the baffle and that let the oil properly drain back.

 

Nannies on or off?
what rpm are you at in 3rd when You gas and it has no pull?

 

Dean, you ever get to the bottom of this?