I'll try and take a look at the files when I get home - can't download them at work.

I understand your car was low, and Tim had some suggestions to tune it up. Did you dyno after the tune up?

I know Dan had to tun down, and then the final dyno was lower yet, so it seems the dyno was not just off high, and what happened at Road Atlanta - the weather station was being baked in the sun, throwing the correction factors off, so that all erad high. I haven't seen that degree of inconsistancy in my own cars, but it does seem we are seeing more of this at Nationals. I think this is the first DQ at the national level.

It is impressive and interesting that Dan was able to win from the back down on HP - shows it's not worth it to push the cap too hard in general.

According to dyno jet there is no calibration required.

I have never seen a variance as big as yours but I have personally experienced a 10 hp variation over a weekend.

Sterling Doc wrote:


My initial dyno on Friday was under the cap and matched up with the dyno done a few months back at Auto Club Speedway (that dyno sheet is included in those files). We did not do any tuning on the car the entire weekend.. We actually don't know how to tune up or down. If the car had dyno'd over the cap on Friday we would have asked for help from the group to tune down because our expectation coming from Auto Club was we had plenty of margin to make the cap without any adjustment needed.

I look forward to your thoughts on the data because I'm at a loss as to any explanation.

My (HP+TQ)/2 was 7 lower on Sunday than we tuned it to on Saturday morning.

I enjoyed seeing you on and off track Alberto. You seem like a good guy. I am not aware of anyone that thinks your are purposefully trying to skirt rules.
Here's my thoughts. First in 2014 I had dyno readings that swung from way high like 148 to 120 on same dyno over 3 days last year. I spend 450$ in tuning and was so mad cause I way detuned and was so slow compared to other cars. So my first conclusion is that dyno can be off different each day! they can also read a few points higher or lower depending on how the car is placed and strapped. This is why a retest is sometimes done.

This year I put in a 52 mm restrictor plate on low compression engine that made 139.4 ave at Autoclub. just to be safe and not have issues. I did not dyno but figured I was minus a few points.
Dan and Simon also were running restrictor plates. I think Dan went to 50mm restrictor after dyno fail on Friday.

Now for your numbers I must say they were unexplainable because they were low Friday. Your driving was very good but I and others would probably say, your engine was the fastest one there. Same at Autoclub. I believe part is your high compressions engines (88's) make more power mid range compare to other years.

my conclusions: All engines are not equal from the builders. Different cam and heads and valves and piston CRs. So unfortunately (cause I hate it) the dyno is best to check for equal-ish compliance and not tearing down/testing engines, like other groups. Test early and/or aim for 136 ave rather than 140 or you are gambling. And no, that does not explain why dyno number went up...?

Alberto - it looks to me like your 944 may not have been very well warmed up on the test runs. Each dyno pull gained quite a bit of power (>2HP, and climbing) - indicating it was getting stronger as it ran more. When you see this in testing, you can't assume the motor has reached it's potential. We use thick oil, and the gearboxes also sap more power when cold. This is why the rules are written to allow pulls until the motor's output stabilizes. This may take a while, and we have seen 944's in particular gain power as they get hot over the years of testing. It is important to match the tests to post race conditions as much as possible. The compliance runs after the event show much more consistency run to run, and were not rising with subsequent runs- indicating that the engine was reaching it's potential.

I am sorry this caught you out, but you have a motor capable of quite a bit of power. It's a good example of how important it is to follow the dyno rules when testing. I understand it can be hard when time is limited, but it is important for accuracy.