As I said, I have no skin in the Turbo game. My car will be an S2. The overboost occurred at a Jan. or Feb. DE. Raising or eliminating the overboost function doesn't raise the boost of the car. I can't say that it wasn't a sticking wastegate or vacuum problem, but it did occur. Overboost does put you into a kind of Limp mode with about 5 pounds of boost and I believe it can only be reset by turning the car off and then on again. When I got back to the paddock and let the car sit between sessions, it returned to normal.

Understood, but eliminating the overboost function does allow the boost to go higher then stock settings. So, the overboost limiter is a good thing as I understand its function.

Chart tweaked:

Model Yr Min. Weight (Lbs) Displacement Rear Wheel Max HP

944S All 2550 2.5L 195
944S2 All 2800 3.0L 215
951 All 2900 2.5L 223
951S All 3080 2.5L 237
968 All 2900 3.0L 223

I assure you Mike there is no "agenda" from my statement...just what I experienced. My car has no hidden funny stuff, secret buttons, piggy backs, etc. All stock or approved components from airbox to the turbo outlet. I had never experienced the overboost either with a 160K mile motor. Over the winter I rebuilt the engine and added a 3" mandrel bent exhaust. Car ran fine on the dyno but the first time out in the real world it went into overboost protection but the boost gauge never went above 13 as I have a warning light on the gauge and it has a max memory that can be recalled. John at Vitesse told me it is not uncommon for 951's to exhibit this behavior with less restrictive exhausts. It has to do with the rate at which the boost builds not the maximum manifold pressure. I attribute my issue due to a freshly rebuilt motor and rebuilt turbo that have the ability to build boost quickly thus triggering the protection mode. I had a dme chip made that had the stock maps and nothing changed but the protection factor raised and used the stock klr chip as required. Problem went away.

Interesting Steve, thanks. Looks like we have a potentially good device, boost limiter, that can be triggered by something other then overboost. Its never simple or clearcut.

Steve: how much did u need to have the factor raised to solve the problem?

"I assure you Mike there is no "agenda" from my statement..." And I thought he was talking about me.

Dave, I like the new weights, since they seem to recognize that the performance difference between a Turbo and Turbo S is mostly in engine HP, now that brakes are free. I guess I should stop spending so much time here and get to work building my 2011 SuperCup car.

"how much did u need to have the factor raised to solve the problem?

I have no idea. The shop copied my stock chip and changed this value without messing with afr ratios. That's what confused me about the whole thing. With same maps and stock klr, same wastegate, oem cycling valve, airbox and plumbing, etc. you would think the exhast wouldn't have caused this problem but it did. I will call the shop and see if I can find out.

Wondering if there a way to keep the good aspects of the the oem mapping and boost limit. maybe yur shop has some thoughts on the subject. and can u ask if they know the set point for the oem limit. thanks.

I like the idea of stock chips, they work for me and don't open up any 'gray' areas. So that is the side I am posting for . . .

Steve,
When you first hit the limp mode with your rebuilt motor, what did you do to troubleshoot?

At what rpm do you make full boost (in 2nd gear)? The factory manuals give a spec for a normal curve. Just curious how far off that you are to hit limp. I think I am behind the curve, so maybe thats why I never had a problem.

It is good to know though that your fresh motor is at/under the hp/tq limits for supercup. I was always worried I would be over if I freshened things up. I am close now on a tired motor, well at least I was when DD put me on the dyno last at VIR. I guess a fresh motor just gets to full power sooner, not more power overall. Guess that makes sense.