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Slap one on a dyno please - an accurate one!

obspsd

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So they say......find it very strange that only the front wheels were changed.
Front skinnies make it a tenth fastest so it would be approximately 10.35 without them.
He is a good driver.
 

bluebeastsrt

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I
I know exactly what the Demon comes with from the factory. If you can post evidence of a faster time from a non crate Demon I’d be interested in seeing it. Video or slip with some photos would be great. Fastest i’ve seen evidence of is 10.43 and that was presented by the nut lickers on YellowBullet and those guys will search the ends of the earth to find the fastest time for the Demon so I’m taking their word for it.
You seam to be taking this personally. I dont own a demon. So I dont have any timeslips. Im sure YouTube is littered with videos. If you cared enough to look. I know a guy personally that has ran 10.2s@135, 136 in a redeye on drag radials. Seen it happen on several trips to atco. Id be happy to introduce you to him next spring. The guy is a fixture there. And he'd have no issue with you looking his car over. So a demon world record of 10.4. Sounds like some shit blaq would say about a mustang. Despite what the genius's on yellowbullet say. So again where did the 10.4 number come from? Was it at atco or cecil. Where I do the vast majority of my racing? Sometimes you just have to forget your biases. And just admit the other guy is fast. Among the car enthusiasts community. Its a well know fact. Demons are fast.
 

V00D00

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The closer you are to 1:1, the more accurate the HP reading will be. A lot of modern transmissions lack a true 1:1 gear (used to be 4th gear in the old 5-speed days), but every effort should be made to get as close to that as possible for accuracy.
I get that. Im asking for someone to explain the technical side
 

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V00D00

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You seam to be taking this personally. I dont own a demon. So I dont have any timeslips. Im sure YouTube is littered with videos. If you cared enough to look. I know a guy personally that has ran 10.2s@135, 136 in a redeye on drag radials. Seen it happen on several trips to atco. Id be happy to introduce you to him next spring. The guy is a fixture there. And he'd have no issue with you looking his car over. So a demon world record of 10.4. Sounds like some shit blaq would say about a mustang. Despite what the genius's on yellowbullet say. So again where did the 10.4 number come from? Was it at atco or cecil. Where I do the vast majority of my racing? Sometimes you just have to forget your biases. And just admit the other guy is fast. Among the car enthusiasts community. Its a well know fact. Demons are fast.
I think i know who u are referring to, arguing with him on FB now actually :)

Again, 10.2 is wonderful, stock is stock, stock except drag radials, is not stock.
 

MaskedRacerX

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I get that. Im asking for someone to explain the technical side

I __think__ it's because a inertia style chassis dyno measures increase in rotation speed (of the underlying drum) across time, and the gearing affects how quickly/effectively[?] the car can increase the rotation speed. I'm assuming the code logic of the software is assuming a certain gearing (i.e, 1:1) in the calculations to derive HP.

So same car, different gears, results in one getting the drum spinning from X to Y in Z seconds, and the same car, in the other gear gets it spinning from X to Y in Z + n_seconds (or Z - n_seconds depending on over or under the 1:1 ratio), with the derived HP number being higher/lower.
 

TORQUERULES

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I get that. Im asking for someone to explain the technical side
I __think__ it's because a inertia style chassis dyno measures increase in rotation speed (of the underlying drum) across time, and the gearing affects how quickly/effectively[?] the car can increase the rotation speed. I'm assuming the code logic of the software is assuming a certain gearing (i.e, 1:1) in the calculations to derive HP.

So same car, different gears, results in one getting the drum spinning from X to Y in Z seconds, and the same car, in the other gear gets it spinning from X to Y in Z + n_seconds (or Z - n_seconds depending on over or under the 1:1 ratio), with the derived HP number being higher/lower.
What he said above and...

1:1 is closest to a direct link between the engine and the rear end/transaxle/differential (however you want to say it and what end, or ends are being driven) gears and tires (where even their ratio and tire size can affect whp numbers due to changes in efficiency, but are harder to control compared to changing gear in the transmission).

I found this from Ford Racing that does a pretty darned good job explaining why you should use as close to 1:1 as possible:

How drivetrain affects wheel horsepower: Most chassis dyno tests are performed using the “roll-on” method, where the vehicle’s drive wheels are accelerated in a particular gear from a low speed to a high speed (generally to the rev limit of the engine) in one continuous sweep. Because of this constant acceleration, engine and transmission inertia, drive wheel inertia, tire characteristics, gear ratio and axle ratio can all affect the final measured horsepower. Generally a heavier wheel will take more torque to accelerate at the same rate as a lighter wheel, so heavier wheels will tend to reduce the measured wheel horsepower. Gear ratio comes into play because as the gear ratio strays from a 1:1, the efficiency drops and therefore the measured horsepower at the wheels also drops. This is why most dyno runs are run in the 1:1 gear (i.e., 4th gear in a 5-speed overdrive transmission) whenever possible. The same logic applies to axle ratio as well, which means that changing nothing but axle ratio can have an effect on measured wheel horsepower. Remember, this does NOT change brake (flywheel) horsepower, only the delivered wheel horsepower due to the change in drivetrain efficiency. When comparing dyno numbers, be sure the wheels, tires, gear ratio and gear, as well as all the other parameters previously mentioned, are the same from run to run!
 

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I __think__ it's because a inertia style chassis dyno measures increase in rotation speed (of the underlying drum) across time, and the gearing affects how quickly/effectively[?] the car can increase the rotation speed. I'm assuming the code logic of the software is assuming a certain gearing (i.e, 1:1) in the calculations to derive HP.

So same car, different gears, results in one getting the drum spinning from X to Y in Z seconds, and the same car, in the other gear gets it spinning from X to Y in Z + n_seconds (or Z - n_seconds depending on over or under the 1:1 ratio), with the derived HP number being higher/lower.
So, i get it, rpm over time. Given that, wouldnt lower gears show higher hp though? Its spinning the rollers faster, in less time, and the higher gears show lower hp/ takes more time to spin?

From what ive seen anyway, the opposite is true.
Have u seen the same?
 

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I'd guess a lower gear might get the drum to a given RPM faster, but a taller gear would continue to spin it to higher RPM, and there's more effect on the final calculation from peak drum RPM[?]
 

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bluebeastsrt

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I think i know who u are referring to, arguing with him on FB now actually :)

Again, 10.2 is wonderful, stock is stock, stock except drag radials, is not stock.
Well don’t be to hard on him. He's a good guy. He's done well on the drag radials. (Which are not stock). He got it down to 10.0 with a change to the dampers. And removing the sway bar.But Im fairly sure. He was 10.4s-10.6s totally stock.
 

9secondko

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Interested to see the dunk results. The DCT tightens up losses all by itself. the driveshaft helps and all the linkage in between.
But the engine can be underrated as well.

The numbers this thing puts up are defying logic. And that’s a great thing.
 

V00D00

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I'd guess a lower gear might get the drum to a given RPM faster, but a taller gear would continue to spin it to higher RPM, and there's more effect on the final calculation from peak drum RPM[?]
2k to 7500 is the same for gears, but thats what i have yet to grasp. What would cause a higher gear to read higher hp than the lower gears spinning the drum.with more force, faster.

I may have to wamder over to YB or other forums to find it out

Well don’t be to hard on him. He's a good guy. He's done well on the drag radials. (Which are not stock). He got it down to 10.0 with a change to the dampers. And removing the sway bar.But Im fairly sure. He was 10.4s-10.6s totally stock.
Initials BB? If not, not the same guy
 

bluebeastsrt

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2k to 7500 is the same for gears, but thats what i have yet to grasp. What would cause a higher gear to read higher hp than the lower gears spinning the drum.with more force, faster.

I may have to wamder over to YB or other forums to find it out



Initials BB? If not, not the same guy
Yea I think that's him. I only know people by first names or nicknames. Dudes car is B5 blue.
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