Not trying to bust anyone's chops on these numbers, just trying to sort out so we can try to understand the situation as bets we can and look for a workable solution. Thanks for checking.

Spoke with PCA scrut on their boost checks and they tell me the temporarily connect a boost guage to the car, put a scrut in the passenger seat and driver down the road.

On stock boxes, its interesting what happened to us at Nationals this year. We had drivers bring us their spare dme's looking for a real stock one, and we were surprised what we found. Boxes that appeared to have never been opened and when we did open them, found signifcant changes had taken replaced or damage done from chips being removed and replaced worng or new soldering done. So, be mindful of reports by prior owners of stock dme's.

I too suspect that Behe is the man to talk to and that will be time well spent. Dave, really great of you to be looking at this so closely, and then to invite others even better. Looking forward to the insight. Almost beginning to comprehend it, too!

This has been discussed on this forum before, it is important to remember that the max limits provide for a margin of error on the part of the tuning of the car, the weather that day, or the dyno, so that the intention is not for the car to be at the max necessarily.

But acctg for now using a stock chip, 205 is attainable with a legal engine, so we can drop the limit down to 210 with a weight of 2750.

Dave,
I'm glad you are going to talk again with John Behe. In my opinion he is one of the few tuners on the east coast that can give you accurate data and explanations. He knows more about this stuff than anybody and it is factual, not the conjecture garbage you read on message boards. With 20+ years of experience you will learn so much. I spent several hours with him trying to learn more about how my car operates on a component level. He tuned my car and knows how to "read" these chips. He has found differences in maps of stock chips from box to box. According to John, stock chips with the same part numbers can have different maps from the factory. Evidently the engineers were constantly making revisions and tweaks and incorporating them into the chips. This whole issue is extremely complex and there is no easy solution. I remember him talking about N/A cars, using yours as an example, and the differences and difficulties associated with trying to get cars to meet Cup rules for all atmospheric conditions. Forced induction cars just compound the problem.

As far as the numbers I have quoted, the 1.82bar I quoted came from Peter Morgan's book on the 944/951/968. Mike is correct about the 1.75 bar stated in the shop manual page 21-10 and M51 motor cars were programmed differently than M52 cars. However, Clark's garage states the following,

5.2 What is the maximum boost I should see on my boost gauge?

This has long been a point of contention among 944 Turbo owners. For early 944 Turbos, I've heard ranges from 1.7 - 1.75 bar while the numbers for the Turbo S cars range from 1.75 - 1.85 bar. However, the factory shop manual clearly states that the maximum boost for both models is 1.75 bar. "Maximum boost pressure of 1.75 bar (absolute pressure) is reached at approximately 3,000 rpm. At higher engine speeds (engine type M 44.51) the boost pressure drops off again and reaches a boost pressure of 1.52 ±0.03 bar (absolute pressure) at 5,800 rpm. With engine type M 44.52, the boost pressure remains constant at 5,800 rpm (1.75 bar absolute pressure) and drops only after this value has been passed."
M 44.51 1986-1988 Model 944 Turbos
M 44.52 1988.5-1989 Model 944 Turbos

There does seem to be some variance between models, but I don't know that anyone's ever actually proven if the later model cars produce a higher maximum boost. The factory does indicate that there is a 10% tolerance at maximum indicated boost. So, that means that the indicated maximum boost could range anywhere from 1.58 bar to 1.93 bar. Start looking for problems if your maximum boost is consistently less than 1.6 bar.

The last sentence of the first paragraph is significant in that it states that, the maximum boost pressure of 1.75 is constant only after this value has been passed

Value has been passed....This is what I have been talking about. The electronics in the S cars are designed to go above the maximum pressure and then be mechanically attenuated, which takes a short amount of time.

Mike used 14.5psi/bar but is actually 14.696. I used 14.7 in my calculations which can give somewhere around 13.7 psi max within factory allowed 10% tolerances. This is exactly how my car acts and Mike sees the same. Why mine goes into protection mode and his does not I can't explain. I never had this problem until I put on the low restriction exhaust.

Sooooo.......Setting a max value for boost and DQ'ing guys for going over it is contradictive to the way these cars were designed to operate. All I can say is talk with Behe and get his opinion.

BTW, My boost gauge reads to 30 psi and has a peak memory recall with no limitations on duration.

Dave lose the stock DME chip. Its a bad and un-enforceable idea. Listen to your constituency.

Don't have a dog in this fight; but can't not just comment in defense of DD's proposal for stock chips.

Any rule set defines the playing field for finding that famous 'Unfair Advantage'. Porsche racers especially should appreciate that as the marque was/is famous for exploiting same.

Most probably the stock chip rule somewhat defines not only the chip but the exhaust on these cars. It's not that requiring stock chips would be unfair; only that it changes one other 'unfair advantage' that previously existed. The exhaust is going to have to more closely resemble oem. See the italics in the above quote.

And that should not be unexpected for turbos. One reason early on that I was pursuing the turbo car in Cup was just that same unfair advantage. With the then rule set a legal turbo (931) would respond to the allowed mods, including open exhaust, to a much greater extent than a legal na motor. With the change to the rules becoming almost dyno series especially the torque limits that unfair advantage went away and that car will probably never be completed. Oh well.

Any rule set limits someone. But only by moving the advantage around.

Thanks John and Steve.

My only conclusion is that a consensus among the constituency can never be acheived. In the end I listen to what everyone has to say, but I make decisions that I think are in the best interest of the series. Drivers come and go as do their positions on rules and I am left the with the outcome of changes and the burden of related enforcement.

The SC class has not been very successful in the format it has been set. Changes need to be made if the class is to do better. I won't get it just right, can only hope for better.

Hopefully Behe will provide some facts that help me make a good decision on the subject of chips. One possiblity I want to pursue is giving drivers the option of using a stock chip or an aftermarket chip with only one map. If a Turbo model is equipped with an afermarket chip, it will also need to have a telltale boost guage.

Dave,

Single maps are OK. Since the DME doesn't impact boost, what's the point of telltale boost gauges. You can use a stock chip and shim the wastegate or mess around with the device under the intake that controls the wastegate (I forgot what its called). If

John

The dme does impact boost by virtue of the limiter.

It doesn't control boost, only throws the engine into limp mode if the limit is exceeded. Its a safety feature in case of a malfunction,