Lol, we'd sniff that out .

There are provisions in the rules to ensure cars are warmed up well, more than in any other NASA ruleset. We don't need to micromanage that more, just be aware that we should follow that through and look for stabilization, both in testing and compliance.

Sterling Doc wrote:


I see what you did there...

Sterling Doc wrote:


So I've already put myself out there as a novice when it comes to using the dyno but if it's not in the rules then how does someone like me know what "stabilization" means? Now, I'm not trying to be facetious here but here's what I'm thinking:

I can now interpret the test at Auto Club as the dyno numbers not being stable because they were increasing with each run: 123, 124, 130. Got it, if I see that again I'll ask for more runs.

However, on Friday at Laguna I saw 123, 128, 125. Oh, the last run went down in hp so is that stable? Wait, the variance between runs is between 3-5 hp. Is that too much? What is the threshold for stability and where is it defined?

I would have rather had that test thrown out and me back on the dyno to get a stable reading where I might have learned I was over and had a chance to fix it. Where I think this really comes into play is when I'm at the dyno looking at a competitor's runs (btw, I think it's great the dyno is open for anyone to see). If the Friday Laguna scenario is not my car but a competitors, how do I say, "Hey, your hp reading isn't stable" and what is my basis for that claim?

All great questions Alberto, unfortunately I dont think there are answers for them.

You and I both got bit by the dyno rouliette that we have to play at big events. Neither of my two cars have given similar results back to back on a dyno anywhere.

You drove well last weekend and earned your spot.

I'm certainly not an expert on dyno's but I can tell you my experience. Last year at Sonoma I got on the dyno early in the morning when it was cool and pulled a high of 140 with an average over 3 runs of 139'ish. I then noticed the car overheating because the fan wasn't on nor did they turn on their blower. They turned on their fan and leaf blower and I turned on the electric fan and after it cooled a few minutes we did 3 more runs with an average of 129'ish. BIG difference! I would have thought it would have gone the other way but I figure with cool air temps and the computer sensing a hot engine it richened up the mixture which worked great with the dense air.

The only other time I was on the dyno a few years before blower placement made a 10'ish hp difference. I don't remember the numbers but I do remember when they moved their fan power went up a bunch and when the stock fans(which I don't run anymore) kicked on power went down at least 5.

What's the moral? I guess fan placement, which engine fans you have and whether they are on, and engine temps all play a big part. Since we are playing with small numbers, one or two can make the difference of being a hero or zero. I would imagine even if all else is equal you will still have statistical variances from run to run. How much makes a big difference to us because we are trying to cut it close to the factory number.

Maybe the answer is test which way makes the lowest number as far as fan placement is concerned and since the rules aren't specific about them, tell the dyno operator how you want it set up.

Alberto, look at your dyno again - they did not put the runs in order on the sheet. They listed them order #1, #3, #2. If you re-order them by the number, they were going up each time. It took me a moment to see that as well.

In back to back testing - on-off-on, running the fans seemed to cost around 1 HP, so it's in your best interest - both in term of the numbers, and protecting your car, to run them. I don't know why 944 motors like to run hot HP wise, but is is a consistant trend we've seen.

I hope this is coming across as helpful to you, and the greater 944 community, because it is certainly intended that way. It is not meant to be punitive, and we hope that we can keep others out of the unfortunate situation you found yourself in with sharing information. I much appreciate you sharing the dyno graphs.