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TOPIC: Perplexing Dyno Results

Re: Perplexing Dyno Results 4 years, 1 month ago #19559

As far as interpreting stable, that is the job of the series director, and you are free to ask them questions. This seems to be more of an issue with testing, than after the cars come off track.
Eric Kuhns

National Director Emeritus

2007, & 2008 National Champion
2011, 2012 2nd
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Re: Perplexing Dyno Results 4 years, 1 month ago #19566

  • afonseca
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  • Posts: 75
Sterling Doc wrote:
Alberto, look at your dyno again - they did not put the runs in order on the sheet.


Great catch! I did not see this either. Just another thing to check I suppose. With that in mind, the initial Sunday compliance dyno also has the same out of order sequence such that it too would be considered "unstable" per our ongoing discussion. In run order it would have read 140, 142, 145 so this beast is still going! However, the retest shows a 143 max at the last run. All values are out of compliance of course but just not giving me any more confidence about repeatability/accuracy of that dyno.

Sterling Doc wrote:

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.


Thanks Eric, it is extremely helpful and I'm at the point where I just want to understand how this is all supposed to work. I decided to share my dyno sheets because I figured it's easier to talk specifics with real data and if my asking lots of dumb questions helps anyone else then I've turned my sad experience into a something constructive for the group.

#44 Alberto Fonseca
? Region
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Re: Perplexing Dyno Results 4 years, 1 month ago #19570

Thanks for the good attitude to a tough situation.

We average of 3 pulls to help smooth out the results a bit.
The average of the 3 run from the compliance check on Sunday to the recheck was within 3/10ths of a horsepower, which is pretty amazining

From a mechanical perspective of car and dyno on a given day, things seemed pretty repeatable. How atmospheric correction factors play in with regard to our cars over time (i.e. how well does the dyno correction factor apply to our cars, etc.), could remain an issue. Moving forward, it my be good to track the temperatures the dynos were done in, and see if there are patterns.

That said, conditions were similar, and the dyno correction factor was the same (1.03) for each day. This is a pretty low correction factor (It is adding 3% to your raw readings to correct from "ideal" conditions). On hot days, this factor can go up to 7-8%. In the end, the biggest issue I see, and have seen in the past, is inadequate warm up on testing. Compliance is done with the cars in "as raced" conditions, while testing is often done more quickly. Having done hundreds of test runs over the years on these cars, I find much better consistency once the cars are hot.

At the ECC, I will make a big point of this when testing, and we'll see how it goes again.

For perspective, when I race in ST2 at the ECC, I will live or die based on one number, and one pull. A single HP reading. No averages with TQ or repeat pulls. I will have to tune carefully, and conservatively!
Eric Kuhns

National Director Emeritus

2007, & 2008 National Champion
2011, 2012 2nd
Last Edit: 4 years, 1 month ago by Sterling Doc.
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Re: Perplexing Dyno Results 4 years, 1 month ago #19572

  • Atteberry
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I have read with interest the posts on this issue over the past week and think we should consider a standard procedure for national events as it relates to dyno and HP. In my opinion if we can reduce the uncertainty then driver may not be surprised with results and find that after driving well all weekend they get DQ'ed for HP when they never touched their engine. We all come from different regions and have our results from different dyno machine's, set up conditions and procedures. For these reasons I propose the following for national events in an attempt to make the playing field more level.

Prior to the first qualifying session all the competitors go the the dyno at approximately the same time and establish a base HP level for their car on the same equipment.

For the weekend there will be a 3% variance allowed. For those cars that have an average of 136 HP or greater you will be subject to this 3% variance with the following being the maximum allowed HP.

136x1.03 = 140.08
137x1.03 = 141.11
138x1.03 = 142.14
139x1.03 = 143.17
140x1.03 = 144.20

If you have less than 136 HP after your 3 base line pulls you have two options. 1. If you do nothing your maximum allowable HP is 140. 2. If you choose to work on your car to increase HP then when you re- dyno and get to 136 -140 then you are subject to the matrix above.

For those who are 136-140 on first dyne session they will have the DME tapped over the adjustment hole and tape placed over the are/fuel box (not sure if this right name). If the tape is tampered with then you are DQ'ed. If you are less than 136 no sealing is done. If you are under 136 and you retune your engine then those two items will be sealed.

If you are under 136 after first baseline pull and you choose to retune your motor you must declare this action to the series director and at your expense pay to have the car re-dyno'd.

The series director will hold all the dyne sheets for the duration of the event.

This does not supersede any further dyno testing during the event for compliance with the rules.

While I suspect most will not want to institute this process, I am asking that we take a serious look at instituting a standard dyno procedure at national events. From what I have read here, experienced myself and heard as it relates to Dan I think the variance in HP per dyno was too great and the inconsistencies resulted in two individuals in our class being DQ'ed during the weekend and at least one in E30 (Charlie for HP issues.
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Re: Perplexing Dyno Results 4 years, 1 month ago #19574

  • cbuzzetti
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  • 944 Spec = The best racing on the planet
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We have procedures in place they just need to be followed to the letter.

We as drivers must insist that the procedure be followed.

I know that this did not happen at Laguna. I was there during the 944 and E30 dyno runs and cars were not being tested per the rules.i reccomend letting your car idle at full temp to be sure it is operated at race temps on the dyno.

I was DQ'd at Laguna in E30 because my car got dynoed before it was at full temp since we had long wait times for every dyno test. It was my fault for not demanding that my car get re-dynoed but at that time I was due on track for the GTS race and made it there just in time to leave the pre grid.

My plan is to test multiple water and oil temp ranges to see where my car makes the most and least power.
2018 NASA 944Spec National Champ
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2010 NASA GTS-1 National Champion
2010 NASA 944Spec National P3
2010 NASA So-Cal 944Spec Regional Champion
2009 NASA 944Spec National Champion
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Re: Perplexing Dyno Results 4 years, 1 month ago #19575

Tom,

I appreciate the thought you put into this.
I would submit that it would not have helped Alberto here, and he is the only person to be D/Q'd for HP in any Championships yet.

Charlie is right that the rules all already pretty fussy, and it make a difference to do it right. I now bring a checklist to the compliance dyno, and make sure all the conditions are met. The dyno operators don't always love the fussiness, but it does help consistency. We really have to spread the word to test the car to it's potential - get it hot. At the last ECC, all the top cars dyno'd all would up within 5 H+/TQ/2 in the end. It would be hard to achieve that level of consistency with Spec built sealed motors.

What speaks volumes, is that Dan was able to win from the back down as much as 10 HP. Test carefully, give yourself some headroom, and drive well.
Eric Kuhns

National Director Emeritus

2007, & 2008 National Champion
2011, 2012 2nd
Last Edit: 4 years, 1 month ago by Sterling Doc.
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