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C2 Dyno Results with Graph & Video

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Old 02-03-2016, 12:40 PM
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MTR
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That isn't as big of a delta as I would have thought. Good to know.
Old 02-03-2016, 12:45 PM
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cobalt
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Originally Posted by MTR
Nice numbers Anthony, especially with the stock cams. Looks like your A/F was doing something similar to mine going a little lean in the upper RPM band. Do you by chance have the dyno run files?
Unfortunately I don't I had most of this on another PC which had issues so I lost a ton of info these are a few years old. I am rummaging through some papers trying to see what I have in hard copy. There is so much crap I am desperately looking for especially the baseline charts.

Car had 1-2% leak down and 52k miles at the time it now has 60k miles. I have no doubt the initial condition of the engine had a lot to do with the results.

Protosport does some amazing work. John was curious about that as well so he straps meters to the car and will test the car on the road monitoring real life numbers to gain the most he can and feel safe about it. In the end we determined it was fine as is. Considering the number of track miles since and that it is still as strong as the day I last tested it I will assume he was correct in his findings. My most recent leak down last year was up to around 3-4% so I am sure there is a change but nothing my seat tells me.

The chip was designed for 91 octane since it was a dual driver and 93 is not always available.
Old 02-03-2016, 12:50 PM
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Originally Posted by Spyerx
I know in my RS the difference with 91 and 100 octane map is about 12hp and about 5 more tq. Surprised if 10 difference between 91 and 93. 402 wheel. It's a 3.6 too!!! :-)
Wow even my ford raptor gains 11hp if I run 93 vs 87 octane
Old 02-03-2016, 01:14 PM
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Steve Weiner-Rennsport Systems
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FWIW,.....

Since we have both an engine dyno & a Dynojet, its been easy to make comparisons between BHP & RWP (Dynojet only) for accuracy.

I've found that the difference is 12% between Dynojet results and what we see on the engine dyno. Your figures more or less mirror the similar engines we have done with those modifications.

Hope this helps,
Old 02-03-2016, 01:23 PM
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Originally Posted by Steve Weiner-Rennsport Systems
FWIW,.....

Since we have both an engine dyno & a Dynojet, its been easy to make comparisons between BHP & RWP (Dynojet only) for accuracy.

I've found that the difference is 12% between Dynojet results and what we see on the engine dyno. Your figures more or less mirror the similar engines we have done with those modifications.

Hope this helps,
That is interesting.
Old 02-03-2016, 03:22 PM
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MTR
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That's good to know Steve, but I like using 15% since it's over 300 bhp.

Seriously though, thanks for the input. Out of curiosity what do stock 964s put down on your dynojet 220-230 rwhp?
Old 02-03-2016, 10:00 PM
  #22  
Steve Weiner-Rennsport Systems
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Originally Posted by MTR
That's good to know Steve, but I like using 15% since it's over 300 bhp.
LOL,...gotcha! I can make 300+ BHP in those things, however it requires a realistic budget to do that.

Seriously though, thanks for the input. Out of curiosity what do stock 964s put down on your dynojet 220-230 rwhp?
Yessir,...thats the ballpark. Many variables are work that include engine condition, cam timing, AFR's, exhaust, and fuel.
Old 02-03-2016, 10:21 PM
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I've always used a # of ~10% for drivetrain loss on porsche when getting WHP. Nice to see a real comparison.
Old 02-04-2016, 09:27 AM
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Would the loss be different if tested on a dynapack vs a dynojet?
Old 02-04-2016, 11:44 AM
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Originally Posted by cobalt
Would the loss be different if tested on a dynapack vs a dynojet?
I would think so and also different for a mustang dyno. I've always used a dynojet as they seem to be the gold standard. It's nice to be able to do an apples to apples power comparison, as long as you use the SAE correction.
Old 02-04-2016, 01:04 PM
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Originally Posted by MTR
I would think so and also different for a mustang dyno. I've always used a dynojet as they seem to be the gold standard. It's nice to be able to do an apples to apples power comparison, as long as you use the SAE correction.
I have a dyno printout but have no idea what dyno it was done on. Will different dynos plot the same graph and just vary on the peak numbers?
Old 02-04-2016, 01:10 PM
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Originally Posted by Steve Weiner-Rennsport Systems
FWIW,.....

Since we have both an engine dyno & a Dynojet, its been easy to make comparisons between BHP & RWP (Dynojet only) for accuracy.

I've found that the difference is 12% between Dynojet results and what we see on the engine dyno. Your figures more or less mirror the similar engines we have done with those modifications.

Hope this helps,
There is an interesting story behind how the Dynojet was developed to arrive at an "acceptable" HP number that would correlate with an engine dyno.

One of the biggest headaches of Dynojet's go-it-alone chassis-dyno project was figuring out how to assign meaningful power numbers in the face of unknown inertia from the moving parts of the hundreds or thousands of engine, drivetrain, and tire combinations. Wrestling to fully understand inertia and powertrain losses, Dobeck and his team quickly realized that the standard physics formula of weight, time, and distance for converting acceleration into horsepower simply didn't work-the derived number was always lower than accepted numbers. They poured on resources and burned up time and money investigating it, but no matter what they did, the math never added up.

Dynojet's final number-fudge was arbitrarily based on a number from the most powerful road-going motorcycle of the time, the '85 1,200cc Yamaha VMax. The VMax had 145 advertised factory horsepower, which was far above the raw 90hp number spit out by the formula. Meanwhile, existing aftermarket torque-cell engine dynamometers delivered numbers that clustered around 120. Always a pragmatist, Dobeck finally ordered his Chief Engineer to doctor the math so that the Dynojet 100 measured 120 hp for a stock VMax. And that was that: For once and forever, the power of everything else in the world would be relative to the '85 Yamaha VMax and a fudged imaginary number. Dobeck's engineering staff was dismayed by the decision, but the Dynojet 100 exclusively measured surplus power available to accelerate the vehicle's mass-no more, no less-and that was true even if the modification was a low-inertia flywheel or lightweight wheels.
Things have changed over time, but the point is that different cars will have slightly different corrections between engine dyno readings and chassis dyno readings. They all seen to cluster in the 12% to 17% range, but the main concern is that they are repeatable in the same car from test to test. Twelve percent between engine and chassis dynos would seem to indicate that a 911 drivetrain is fairly efficient at transmitting power.
Old 02-04-2016, 01:20 PM
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Originally Posted by porsche mania
I have a dyno printout but have no idea what dyno it was done on. Will different dynos plot the same graph and just vary on the peak numbers?
There is a little more to it than that. A dynojet is an inertial dyno where your car is accelerating a large drum versus a mustang dyno is a load dyno. Putting a load on the car further reduces the HP and TQ readings which is why Mustang dynos read lower than Dynojets. I can't speak from experience, but I've read that because the mustang dyno operator can manipulate the amount of load the results can also vary significantly, making it hard to compare numbers with other people.

That's why I really like Dynojets as I can compare my numbers with anyone anywhere and the SAE correction will adjust for things like altitude, temperature, and humidity as best as possible. Dynojets also let you save the run digitally so I can send my run to someone else so they can overlay it on to theirs which is very nice for comparison purposes.

If you have a dyno chart, post it up and maybe someone will be familiar with the format and be able to tell you the brand of dyno used.
Old 02-04-2016, 01:22 PM
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Interesting stuff. I had a full engine rebuild on my C2 last year which included 993RS Cams, Schrick valve gear and a Steve Wong Custom chip and on a power it made 290BHP with 270 Ib/ft Torque, so similar mods with very close results.

It's probably worth adding that on the same rolling road, prior to rebuild it recorded 252BHP and from memory around 240 Ib/ft Torque.
Old 02-04-2016, 08:25 PM
  #30  
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Originally Posted by cobalt
Would the loss be different if tested on a dynapack vs a dynojet?
Oh hell yes,....

All chassis dynos give different results: Dynojet, Mustang, Dynapak, Superflow, etc.

The only one that gives reliable results that exclude any operator shenanigans is the Dynojet and thats precisely why sanctioning bodies use them.


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