Dan Chambers wrote:I'm basing my competitive class on "ballpark exercises, at best" ... as are my classmates?
Well, it ain't rocket science, that's for sure, Dan. If this were a moonshot aimed at landing on the "Sea of Tranquility," I don't think you would end up on Mars, but you might touch down somewhere else on the moon (possibly on the dark side), but still somewhere on the correct celestial body.
I'm not the one to play apologist or cheerleader for the new rules here--my history in this process is pretty clear. I advocated for rules stability and evolutionary change/refinement from the beginning, not the radical overhaul we got in the end. But it's a done deal now, and I'm dealing with what we have like anyone else, trying to figure out what the rules mean now and trying to optimize my car. It's going to be an interesting year, and the next few rule revision periods should be fruitful, as we discover the "holes" and unintended consequences of the new system. It's important to keep in mind that this is all supposed to be for fun.
My take on the new rules is that everyone has a place to play, but the compression of the classes is going to favor certain choices of cars and mods (as has always been true). Obviously, the SS classes are going to offer the best chance of "level competition," but this choice isn't available for the older cars. Even in SS, there will be "favored" models within a class, but the new rules encourage not modifying your car, just like the old ones. With an older (or modified) car that runs in the CC-classes, you have choices to make about setting up or optimizing your car that will probably offer 3 classes to run in, depending on tire and equipment selections.
In your particular case, I'm not sure that the vagaries of dyno measurement have to enter the picture at all. Is your engine swap completely stock? Were cams/induction/compression changed or was the engine management reprogrammed in the process? If nothing was altered, and you simply transplanted a stock 3.6L into your SC, then my opinion is that you don't need to (and probably shouldn't) bother with measuring the HP. You will almost undoubtedly be better off using the figure for HP published by the factory for your engine type, as it seems that Porsche is very conservative with their power figures and most models produce more power on the dyno than advertised.
If your engine has been modified from stock, you may still find that measuring HP on the dyno gives you a better result in the HP/Weight equation than taking the individual point penalties for the various engine mods. There is no "free" chipping anymore, though, so if your only mod was reprogramming the ECU, I would consider going back to stock and not having to dyno the car. This is a cheap and easy "de-contenting" that may pay off ultimately in points and $$$.
If you are forced to dyno, it's not the end of the world. Yes, there are variations in machines and techniques that do not give you an absolute value that is guaranteed to be accurate. As Mike said earlier in this thread, dynos are most useful as a tuning tool, optimizing output of an engine, not for comparing it to other cars measured on other machines at a different time. As John Gordon said, for classification purposes, it is best to have all the cars measured on the same machine on the same day to level the possible variance in the figures. Our rules don't require that, though, and we don't measure ALL the cars in the class, so there are going to be variances. The question is how significant these will be. As we saw from Gordon's report, even with a highly modified engine, he came out better on total points by measuring than by taking individual mod points. I would point out that the "blips" that some people reported on some runs were for peak torque numbers, not for max. HP, which is what applies for the formula, and they were small (3 ft. lbs. in my case, out of 190).
Am I pulling 273 RWHP, am I pulling 287 RWHP, am I pulling 269 RWHP?
Well, if you dyno and don't like the number you get, you can always go to another dyno and try again. You might get luckier.
I think you will find that even given the possible variances, a 5% (say, 10 HP in 200) difference in measurement on one machine vs. another does not have a huge impact in our classification scheme. Plugging 194 HP instead of 204 into the formula for HP/WT makes a 17-point difference. If that point difference bumps you into a higher class, where you don't want to be (remember you have 50 points between classes until you get to CC-14, where you have 75), you can make some other change like adding some ballast (if you are less than stock weight) or changing your tire choice to get back down into the class you want to run in. It's all a compromise, and indeed a "ballpark" situation. Some of the cars you might be running against may have 49 points less than you do, if their cars are not optimized.
HTH,
TT
