#1 - 5 runs instead of three - Yes
Because there is some question about our squiggles, doing five dyno pulls and throwing out the highest and lowest would seem to help remove any "wild card" squiggles. From what I understand, the three compliance runs would no longer need to be consecutive.

#2 - Add fluids - Yes
This is what will happen regardless and what should happen. No one would refuse to allow someone to top off their oil if it was low after a session. It would be done with an official looking on and it is common sense.

#3 - Limit RPM's - Yes
This would make it clear that the dyno operator should not hit the rev limiter more than once in a series of pulls. Once confirms the rev limit and hitting the rev limiter is hard on engines. Setting the "minimum" helps prevent it from happening more than once, I hope. The sheet Eric posted started dropping HP after 5,900 and there is no reason to run the engine over 6,200 more than once for compliance. This will be better for everyone's engines while on the dyno.

#4 - Oil temp - Yes
This would seem to be an easy, repeatable solution for the question of when the compliance pulls start. No longer is it vague. When the oil temp gets to 160 or more, compliance runs start. If the car is still hot from the track, it may not need any preliminary pulls nor should it. This removes the "judgment" of someone from our equation and I like that idea. Getting the oil temp, at the oil filter should not be any problem. An infrared pyrometer is accurate enough as long as every car to be dyno'ed has the same one used on it. If a tire temp pyrometer is used, that is fine too as long as the same one is used for everyone in that session. The instruments do not need to be calibrated across the country. They will be accurate enough to ensure the oil is up to some reasonable temperature and that is all we are trying to achieve, it seems to me. Oil temp is a much better way to ensure engines are up to temp than water, too. My water will get up to temp way quicker than the oil and I, for one, would not allow my car to be put to the stress of a dyno until the engine was warm and the oil is the way to be sure of that.

I do not see anything bad about this. If someone wants 150 or 165 we can argue about that but something that makes our procedure less prone to human intervention is a good thing for our class.

While I understand Eric's thoughts on the squiggles, my concern is to try to prevent one anomaly from DQing someone. If there are several of the same magnitude, OK I feel better then. If there is one that is appreciably higher, being able to exclude the outlier should help. If we see actual dyno sheets, in the future, that show a bigger problem then it MAY need some more thought but this seems like a reasonable approach with what we know now.

The other area that is of great concern to me, and that has not been addressed with these proposals, is the variability of dyno's from time to time and from dyno to dyno. Eric believes that one should get their car tuned up as much as desired, get it warm (because that is when it will throw the highest numbers - its "potential"), tune the power to be where the highest pull is where you are comfortable, and be done with it. Walk away. Is your comfort number 137.5? Is it 136? Do you want to go with 139?

That would be fine with me IF all dyno's were created equal but they are not. It might even be fine IF a dyno was consistent from time to time/ day to day, but they may be neither and there is my problem.

Imagine that I do as Eric suggests but I happen to be on a dyno that reads lower than some others AND I dyno on a day where it decides (assuming it can decide anything) to have one of its "lower" days. How much too low am I showing? So, since I am below my comfort level, I tune to get to my comfort level on the highest pull of the day and I say "fine I am finished"

To continue my hypothetical, I now go to a race and get dyno'ed on another dyno that simply reads higher than the one I was on AND it decides to have one of it's high days. WHAM! My only protection would be to go to whatever dyno is at the track I am at and pay to get my car dyno'ed to make sure the worst case above did not happen to me.

I know, WOW what a lot of what if's. Is that guy a lawyer or what? Folks here is the bottom line on dyno's.

DYNOJET DOES NOT HAVE ANY WAY TO CALIBRATE A DYNO.

There are dyno's out there that are somewhat new and there are some that are many years old and there is no way to calibrate them. Heck, my alignment guy gets his alignment rack calibrated every month to be sure it is still exactly level but a dyno can not be calibrated, at all, ever.

Will some dyno's read higher than others, absolutely. Will they read differently from time to time, day to day, absolutely. We have all seen it on our own cars. We all know that our cars make different amounts of power depending on weather conditions. The dyno is supposed to take all of that into account and "adjust" its numbers back to a "true" number. If so, and if you did nothing to your car, why does it throw off different numbers at different times? We all know that dyno pulls at higher altitude seem to give us lower numbers than we are used to but the Dyno is "supposed" to correct for that. Dyno's are not perfect.

We, however, have a perfect example of what I am talking about with a car at Nationals. On one day it read higher than allowed. On the very next morning, after having been sealed overnight, it was thoroughly warmed up and it read legal. The SAME car on the SAME dyno but at different times and different weather conditions. I do not know exactly what the three run averages were for each session but would like to understand what the exact average numbers were as that is my point here.

While I do not have enough information to make any statement about what the variability factor is, we as a class need to remember that it exists and we need to gather data when and where we can to build up a data base. It will require everyone to be careful. For instance, anytime someone gets a dyno from a different dyno, they need to compare it with prior dyno's and share that information. Of course, if they have done something to their car that might effect performance the data is not valid and they need to understand that. Over time, we need to try to build up a data base for the same car on the same dyno at different times and on different dyno's to try to understand the variability of dyno's to make sure our dyno rule actually works the way we want it to and not in some unintended way. It is the best tool we have but we need more data as time goes on.

I simply do not have confidence in dyno's to be comfortable DQing someone that is .1 over our limit. I want to get to that point and I hope we all can get there as time goes on.

Suggestions are good so feel free to make your own. If anyone wants to discuss anything I have said with me, please feel free to e-mail me so we do not bog the forum down. My e-mail is This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Jim Foxx

Ken,

I think it is great to codify that the compliance dyno testing is open to all, as well as to clarify adding fluids (in practice this has been allowed all along).

Jim,

I hear you. All classes deal with this, and we can only minimize this through averaging runs, checking tire pressures, etc. We have incorporated all the ideas from other classes.

As far as the example you bring up, the 3 run average difference was about 2 (HP +TQ)/2. It was close on both sides. On any given day it might fall just over, or just under the limit, even with fairly little variation. Everyone makes their choices on how close they want to run. The results were not an anomaly. Weather conditions were quite different from the test to retest (delayed overnight due to rain). Despite this, results were fairly close, though in this case, just on one side, vs. the other of the hard cap (both were over the soft 138 cap). I think this is an object lesson in the gamble of pushing the cap. Sometimes it may work, out others not.

I have a few thoughts but I should say that I'm not the most informed about dynos and the intricacies involved so take what I say with a grain of salt.

My first thought, and I've felt this from the beginning of the dyno rule is that there should not be a hard and soft cap. We set the limit at 138 but really it's 140 so people are shooting for that. However we adjudicate the dyno findings lets pick a number and stick to it. If it is found over then that's it, and I prefer 138 by the way. It seems that if we are splitting hairs and discussing rules minutia when you are pulling in the 140's the spirit of the dyno rules were ignored(I'm not thinking of any car in particular so this is not a knock against anyone who may have pulled higher numbers).

I haven't thought out all the details of this idea but what if we had an average from a few different cars factored in. Say we get a dyno sheet early in the season and then when you are tested again and go over some math wiz who didn't go to public school like I did could figure the percentage you are over. Then take say 3 or 4 other cars, have them do pulls and see what percentage difference from their original run they are at. If you are the outlier you are in violation but if everybody is pulling about the same percentage better than we will call it a dyno anomaly. Of course engines wear at different rates and are maintained differently but if a big enough sample is taken then we should be able to get an idea of where the median is.

One other quick thought, again not well thought out but it occurred to me that we don't have this trouble with scales. They differ from set to set, are somewhat weather affected, and if aren't taken care of properly will be out of spec. I'm not aware of how often they are recalibrated but I am certain no two sets read alike.

There doesn't seem to be much controversy with them and the question is why? I believe the answer is we all build in a little cushion so we don't have to sweat it. Why don't you do this with your motor? I'm not worried ever about pulling over the limit and I think most everyone else is in the same boat so if you built your motor to pull right on the limit, you should take the chance of pulling over and being disqualified and not worry about small variations.

It's been said repeatedly that 5 horsepower doesn't make a difference so build a quality motor that is 5 horsepower under the limit and we won't need to hash out these details.

Thanks, Ron.

We had a competitor at Nationals last year who nearly bumped themselves off the podium with a weight of 2601 (!). He runs a little extra ballast now, and has no worries about weight. For regional competition, the weight rule is more onerous than the dyno rule. If a competitor goes under in weight, it becomes a non-droppable DQ, and must be taken as 0 points. Other classes handle dynos the same way. We made a specific rule to lower the standard CCR penalty to a "move to last" for the first offense in our class. BTW, I do hear some complain about scales, but the rules remain.

While I'd agree that the spirit of things is to have all cars equal on any given day. Try to make a rule around variations from mean would require a statitician to regulate at the event. What we have been pursuing over the last year is ways to get as close to equal as is practical (and as close as to make no difference). This requires the top motors to detune a bit, and the guys on the lower end to do some dyno tuning. Norm saw some good results from tuning his AFM at the track, as did Neal. I think most motors can get into the mid 130's (from either direction), and that's what we should shoot for. We dyno'd a lot of cars at Nationals - most were in that range, at least after some effort at tuning the AFM.

rd7839 wrote:


I believe you have a very valid point. Why is it that we give on the dyno but not on scales. They are the very same principal. If your over your over. On one hand you get a slap on the wrist and with the other your DQ'd. Not very fair!!! I think that should be changed to fall in line with the scale rule of being DQ'd if one goes over.
Live by the rule, die by the rule.