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Dyno
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TOPIC: Dyno

Dyno 15 years, 1 month ago #6370

Thought I'd post dyno I did today.

Some back ground - this is a low compression motor, with a shaved head. This same motor about 1.5 HP/TQ less at Nationals in 2008, with an open element air intake. It now has a stock airbox, and a quieter Borla exhaust. Results are within dyno variation, favoring the new setup. This again confirms that the OEM airbox is not a restriction, nor is a reasonable exhaust.

Here's the dyno:
Eric Kuhns

National Director Emeritus

2007, & 2008 National Champion
2011, 2012 2nd
Last Edit: 15 years, 1 month ago by Sterling Doc.

Re:Dyno 15 years, 1 month ago #6371

Looks good, waiting to see how you hold up against my whopping 124hp @ RA.
MICHAEL MADUSKE
2009,2010 Southeast 944-SPEC Champion

Re:Dyno 15 years, 1 month ago #6373

  • F1rocks
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I've not spent much time looking at the torque and horsepower curves for these. Looks like running any higher than 5,500 is just making more noise and not much else.

Thanks for the data points. Is Dynojet our standard for dyno's??

Re:Dyno 15 years, 1 month ago #6379

We do not have a dyno standard nor a dyno limit in the class. Most cars will dyno in the 130's for peak hp and 130's for peak torque. Both peak numbers should be close, but a few more ft-lbs is not uncommon. This is mostly for dyno jets, but every dyno will vary.

Remember a dyno is just a measurment tool. Most dyno to dyno (between) variation can be 3-4 hp for our cars. That means from Jimmy Bob's dynojet as compared to Ricky bob's Dynojet. Within dyno variation is much less. This means if you do a pull on Jimmy bob's and then pull again 1 hour later those numbers should be with in 1 hp. However that is if you look at 3 pulls each. I have often seen pull 1 on dyno 1.5-2 hp low. Then the 2nd and third pulls are perfectly overlapping to 0.3 of a hp.

Now if you do a pull today and then come back 3 weeks later I would not be shocked to see 1-2 hp variation even on the same dyno. Dyno's can correct for atmosphere, but 1% shift is not very big.

Dyno's are best used to measure back to back testing and next best for baseline and post upgrade testing. Comparing on dyno read out to and another even if both are the same model is not really fair.

Even so I have seen alot of dyno pulls over the years and Eric's pull is right in the range I would expect for nicely running 944 spec motor. (shaved head or not, low comp or high comp pistons)

Dynojet pulls under 128-129 are indicitive of some sort of softness in the motor. The first place I would look for softness is in the valves. Poorly sealing valve cost hp. The bores are rarely a problem in these cars.

Of course if you pull a 124 hp on a mustang dyno then your motor could be fine. This type of dyno routinely shows lower numbers than dynojets. However I have never seen data from enough of them to know what that typical range is. From what I do know 124 on a mustang may be 134 on a dynojet.

Now the reason I bring all this up is that it is one big reason we don't have a dyno limit for the class rules. I believe the dyno to dyno variation is large enough to cause nothing but headaches in compliance vs makeing it easier. We did us a dyno to validate use of stock DME chip, but that was doing pulls back to back with in 1-2 mintues of each other. Results from that showed two things. 1) no compliance issues and 2) it was very good test to back to back pulls with the competitors DME and stock referce DME and use the results to show no change in engine output. Of course if engine output did change it would imply some difference in DME programming.

The other thing is that if the car did pull a 140 hp number it would not mean it is not legal, but it would probaly lead to alot more careful looks in the tech shed. 140 hp is in general pretty high, but if the dyno at the event was reading a bit on the high side all event then maybe it would not raise any eyebrows. So again a dyno is just a tool to help with compliance, but and one single peak hp number will not DQ anyone nor should it be set as a "the standard".
Joe Paluch
944 Spec #94 Gina Marie Paper Designs
Arizona Regional 944 Spec Director, National Rules Coordinator
2006 Az Champion - 944 Spec Racer Since 2002

Re:Dyno 15 years, 1 month ago #6386

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So, Joe, what you are saying is that my 145 to 147 hp numbers turn out to be OK because of the variations inhearent in dyno's. That is good to know and releives my mind of concerns over this issue.

Life is GOOD.

Big Dog
Jim Foxx
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