Re: the dyno rules

While I understand the desire to have an update to the dyno rule handled behind the scenes, I believe it is too technical to have only a few laymen contribute to revisiting it. While there may be many with no expertise in dyno work that might voice an opinion, I believe that we need to encourage input from those that may have substantive information and/or knowledge of the issues.

With that said, one issue that may be peculiar to our cars is the jagged peaks and valleys that our dyno sheets show. Tom, from 7's Only (Buttonwillow) has a DynoJet. He has shown dyno sheets from a variety of cars. They do not seem to have the same look as our sheets. They appear to be much smoother than our cars. These peaks and valleys are after the smoothing is applied, meaning that something may be different with our cars that cause them to be more pronounced.

Also, the dyno uses the torque curve to interpolate the horsepower. The dyno does NOT read horsepower directly, it is a math calculation based on torque. Even with the SAE 5 smoothing, peak horsepower is calculated from the peaks in the torque (after smoothing) although at a different point on the rpm band.

DynoJet says that SAE 5 is the highest level of smoothing they have available. It does not smooth out our cars as much as other cars so the question is why?

A possible reason for the look of our dyno's may be our torque shaft. Most cars do not have a torque shaft, they have drive shafts. Drive shafts generally are much larger than our torque shaft. Our torque shaft is a long torsion bar, in affect. It will "wind up" and then cause a quick release of stored energy to be transmitted to the transmission and rear wheels. This "wind up/release" affect may be the cause of our peaks and valleys even with the most aggressive smoothing factor available.

Our cars may be more difficult to dyno and get real numbers than other cars because of this. Reading a peak and then showing a corresponding peak in horsepower does not represent the actual power that is going to our rear wheels, it represents a momentary pulse only.

These peaks and valleys are significant to our results if the peaks are being used to determine power instead of their "average", and they seem to be. We may need to use another "smoothing factor" to get a better idea of relative power because the bottom line is that dyno's are not all that accurate, from day to day and from time of day to time of day. Perhaps they are not all that accurate from altitude to altitude either since all of the "corrections" are algorithms that make "corrections" as well as the programmers can make them but they are somewhat theoretical.

These problems make our present dyno rule a challenge when our cars seem to react differently than most other cars do and the dyno software is using false peaks, generated from our torque shaft, to determine results.

What does this mean? Perhaps we need to go to some simple way to determine our compliance by taking the dyno sheet and locating the one peak/valley on the torque and horsepower curves and drawing a line between that peak and that valley and using that as the value for that pull. In affect creating our own smoothing factor to compensate for the torque shaft distortion.

In addition, because dyno's are quite variable between different sessions with the same car in the same configuration, perhaps we should be able to go to the dyno, assuming there is one at the track, and check our power output. If it is legal, one could have an official seal whatever is needed to be sealed to prevent later adjustments and that car is done with the dyno for that weekend - Period. This system would put the burden of dyno time on the individual and would remove repeated dyno sessions, by tech, of that car throughout that weekend as long as the seals are in place. It would remove possible dyno session variations from being an ongoing problem for us. Comply one time, seal things and be done with it for the weekend.

As many of you may recall, I was greatly concerned with the dyno variability last year when the rule was imposed because of my own experience with the variability while racing in the GTS class at Nationals. I have variations of five and six horsepower/torque averages during three days and, probably, six official dyno tests and I was in a horsepower/weight class where six horsepower meant lots of weight variation to be legal. I believe this is a much larger problem than was recognized last year and should be addressed.

My concern with the series directors addressing this, behind the scenes, is that laymen will be making very technical decisions for us that may not be qualified to really make them. Our rule set process needs to be as transparent as possible so that everyone feels invested in them to continue to grow the class. The Spec E-30 debacle, as well as our own from a number of years ago, should teach us all a lesson about transparency.

Thanks for listening and here is to another year of great racing coming up.

Jim Foxx

#1 - Yes. This proposal seems reasonable for anyone that chooses to do it. It is their risk and their reward. With our dyno cap, if someone needs to do this to get their power up, great. If it removes a source of failure for them, great too but not a big issue for me. Letting racers get up to power is reason enough.

#2 - Yes. This is not required and, if it helps someone with reliability, go for it.

#3 - Yes, the current rule does not make sense and it gives an advantage to those that have cool shirts and fire bottles. It seems to me that allowing ballast anywhere on the floor AND in the rear seat butt well areas (very secure, safe mounting point, make sense for all. It allows anyone to obtain the same benefits that those with cool shirts and fire bottles now enjoy.

#4 - No. No real reason to allow these. It would cause great confusion and cost to those with our current tire if they had to change over and most do not purchase used tires anyway.

#5a - Yes. Right now, there are heads that are not legal BUT are still within the compression rule. The dyno cap removes this as any concern and making engine parts illegal without any real reason does not seem to make much sense any more.

#5b - No. Does not comply with low cost concept

#6 - Yes. Anything that allows more cars to come over and try out what we do is a good thing. This rule has been used on occasion so no reason to remove it now.

#7 - Yes. A positive rule IF it is restricted to low compression engines only. According to expert engine builders, the factory timing is very, very good. Changing it is not any appreciable advantage. However, with a shaved head, timing changes and costs those engines power they are trying to get by shaving the head in the first place. With our dyno rule, why not allow someone to do this if they can gain power and be closer to the others. It will not be "required" simply allowed for those that can not make power some other way. It will simply be an option for someone searching for power with a low compression engine.

#8 - No. We have a series that allows different cars to compete and not everything can be equalized. Late cars have heavier wheels and brake rotors that are not equalized. 924's have better aero that is not equalized. There is no reason to do this unless we figure out how to "equalize" everything and we will never be able to do that. It is the nature of our various allowable cars.

#9a & b - Yes to both. The reality is that there may not be any blocks out there that are still within wear limits and things are rapidly getting worse. Having to purchase multiple engines to try to get the best of the worst to build an engine seems to be the wrong approach that gives an advantage to those with more money (Spec Miata engines come to mind) that to really solve the problem for the long term. To throw away blocks is easy to tell someone but harder to do if it is you. The next one might be worse.
The argument that it may be expensive is an unknown and, if it is, it is not required of anyone. It just opens up an option for all. It may well turn out to be less expensive than engine failures because of poor blocks and pistons. High compression pistons are no longer available. Are low compression pistons available new? More and more of our pistons are out of spec with skirt wear and ring groove wear, too.
If this class is going to last for 20 years, lets fix these kinds of problems before they cause new racers to go to another class because they are concerned with parts. Our class can collapse quickly (remember the RX 7 class demise).

#10 - Yes. It is not required and is not a performance issue. If someone believes it will protect their box, let them do it. If the ballast rules are opened up, as proposed, any advantage of the weight seems to substantially go away too.

#11 - Yes. As I recall, Joe Paulach posted that this was OK sometime in the past in response to a car build question. (I did not go back and research this.) I recall that I was advised to overfill my oil just a little to protect the engine from low oil during a longer race. I over did it at PIR and was smoking as a result and got a black flag because NASA thought my engine was blowing up. Apparently, Eric has seem many cars with this set up. Mine has it in response to Joe's post. I think this is a good thing and would not require a change to a large number of existing cars.

#12a - No. This rule is not broken. Not all of our cars are equal now. If this is a disadvantage to 924's, they have an aero advantage now. We just can not make everything equal with different years and models of cars legal in our class.

#12b - No. This would require a large installed base to make a change in something that is now legal.

#13 - Yes. Not required but does allow options for racers. It will allow a much safer air intake location for helmet/driver air. The cost is very low to anyone that can do basic work on our cars and there is no real performance issue.

#14 - No. The reason for not allowing it was the aero advantage to early cars with smaller fuel tanks. They can cut an opening in it for access to the trans now but simply need to make it so it can be put back in after service is completed.

Jim Foxx

New additions

13 - Yes. dont see it as a major weight saver or expense

14 - Yes - speculation of the aero benefits between the years over this is just speculation with no measurements done for either style. Late cars have other benefits that make up the differences.

After some thinking on the Dyno rules and the variations that happened at Nationals maybe it would help in publishing any compliance dyno runs (either the average numbers used for the yea/nay or the raw data).

This would be useful in 2 ways - Reduce speculation on the results as well as seeing what the different regions top cars are achiving.

The more open we can make the process the less rumour and inuendo will cause dissatisfaction.

I realize different regions will dyno different amounts depending on both facilities and need, but it would be great if the publication included regional compliance runs as well as the National numbers.

Thoughts ?

I like it, Jerry. It makes lots of sense.

Jim Foxx

I'd say no to the two new proposals for a few reasons, the biggest of which is we would be creeping further from factory.

Glass quarter windows are free and don't get broken easily or often. Replacing them with plastic costs money, even just a little adds up with all the other just a little costs. Also how will they be mounted? If they are flush they are an aero advantage. If you try to reuse the rubber they won't stay put. If you bolt them to the window channel they look horrible! It gets very hot here in California and with a cool shirt and naca ducts in the door window channel I stay plenty cool!

Cutting out the spare tire well should be outlawed for any year. Again it's too far from factory, not needed and even may cut out crash material between the bumper and gas tank. I've taken out my tranny several times by myself in the garage with just a floor jack and it only takes 30 to 40 minutes. Taking out the spare might save a couple of minutes but that's it. All it does is take weight out in one spot so you can add it somewhere else, at the cost of some measure of safety. And if you take it out if the filler piece is not very specifically detailed what's to stop me from making an aero plate from the bottom of the tank to smooth airflow under the car? Somebody will and will argue that the rules don't cover that.

Am I the only one who wants to stay close to factory? If I am I'll be quiet. I know these are small proposals but they are starting to add up. Maybe we should start adding rules to back the cars up to where they were 6 years ago. The costs won't be too great to those who have made big changes and will be more in line with the original spec idea. Or maybe we should think about splitting into two classes, spec and sealed spec 944.