DynoJet, Inflated numbers???

[pelletz]

I dynoed my 2000 NSX-T on a Dyno Dynamics dyno with Downforce AIS+Unifilter as my only mod and produced 240.7 and 240.2 rwhp. I was expecting more like 247 to 250 range??

I saw numbers posted from a 1995 NSX (no mods) that dynoed 235 on a DynoJet dyno.

What gives? Shouldn't my car dyno much more than a pre 97 model? The guy at my shop told me that the DynoDynamic is the most accurate dyno and is generally more stingy, while the dynoJet dynoes typically gives 12-18 more generous hp numbers. This would account for the difference in the number for my car and vs the stock 95 model.

What are you guys experiences and/or thoughts?

 

[SugrueNSX]

I dynoed my 2000 NSX-T on a Dyno Dynamics dyno with Downforce AIS+Unifilter as my only mod and produced 240.7 and 240.2 rwhp. I was expecting more like 247 to 250 range??

I saw numbers posted from a 1995 NSX (no mods) that dynoed 235 on a DynoJet dyno.

What gives? Shouldn't my car dyno much more than a pre 97 model? The guy at my shop told me that the DynoDynamic is the most accurate dyno and is generally more stingy, while the dynoJet dynoes typically gives 12-18 more generous hp numbers. This would account for the difference in the number for my car and vs the stock 95 model.

What are you guys experiences and/or thoughts?

As you probably know calibration varies wildly from one dynamometer to another.
Temperature, altitude and humidity also have to be taken into account. Unfortunately this makes hp number comparisons somewhat meaningless. It seems to me that there is a trend within the industry to calibrate the dyno to read more hp than is really there because it makes the customer happy. As David Vizard said “use the same dyno and take a baseline reading before the mod and then check again after it’s done.” Or something like that. In other words, it really does not mater if the dyno reads 33.34 Elephant Newton yards so long as it reads 36.75 Elephant Newton Yards after you put in the new scram jet kryptonite throttle body. Unless you want to brag about the hp numbers to your buddies. Which I’m sure you don’t because that would be childish. And of course, if you want to compare… the best dyno is the race track is it not?

Regards,

Patrick

 

[pelletz]

As you probably know calibration varies wildly from one dynamometer to another.
Temperature, altitude and humidity also have to be taken into account. Unfortunately this makes hp number comparisons somewhat meaningless. It seems to me that there is a trend within the industry to calibrate the dyno to read more hp than is really there because it makes the customer happy. As David Vizard said “use the same dyno and take a baseline reading before the mod and then check again after it’s done.” Or something like that. In other words, it really does not mater if the dyno reads 33.34 Elephant Newton yards so long as it reads 36.75 Elephant Newton Yards after you put in the new scram jet kryptonite throttle body. Unless you want to brag about the hp numbers to your buddies. Which I’m sure you don’t because that would be childish. And of course, if you want to compare… the best dyno is the race track is it not?

Very well put. I geuss it could be compared to weighing yourself on the same scale every so often vs. a different scale that may very 1-7 pounds. I will be using the same dyno after each mod i do, so will have consistency.

I agree that all the dyno numbers posted here are pretty much meaningless unless there are baseline numbers to compare it to and 1/4 times speak more accurately of what you have done to your car as it takes other variables into consideration (i.e.weight reduction).

I guess if i decide that i want to brag, i'll go get on a dynojet.

 

[TomCat]

Agree 100%...relativety not absolute!!

 

[rbirling]

Temperature, altitude and humidity also have to be taken into account.

These are _supposed_ to be accounted for in the software, but I agree that it's probably not done accurately. Who checks accuracy of humidity sensors, for example? Theoretically there's no good reason, IMO, for dynos to vary so much. But it seems pretty well known that they do. :frown:

 

[khappucino]

i think dyno's are more useful in telling you if something is 'Wrong' with your car :biggrin:

 

[SaberX]

I bet your 19" rear tires eat up some HP.

 

[NetViper]

Most Dyno Dynamics numbers are correct by about 13% to get a similar number to what a DynoJet makes on the same car.

 

[paulviriyapan]

Just as a thought, that Downforce AIS and Unifilter won't do anything for you on a dyno since there's no air going into it to give the ram air effect.

 

[DutchBlackNsx]

13%...lmao, thats some cheap hp gains for the NSX!

I mean, how can you prove you gained 5hp by adding some mod?
Even when saying its relative, you cant compare if the sensors aint calibrated, let alone the whole dyno being calibrated.

Are there any real accurcy numbers availble for dyno's in general? I have been wondering about this for a long time.

 

[austrian type-R]

don't give too much attention on the wheel horse power. You will get out more whp dynoing in 3rd gear than in 5th gear, but always the same brutto hp. It is a simple thing. If the tires spin faster you have more drag, so if the car dirves 220kmh you loose maybe 30hp and at 280kmh you loose 70hp.

I tested my NSX and my turbo ITR in 4th and 5th gear and I got always different numbers on the whp, but same on bhp. It is easy to understand when you look at my graph.

As you can see below. The blue line is showing the whp and the red line the bhp. Below the black straight line at ZERO the blue line is showing the hp loss in drivetrain, as faster you go the more hp you loose in drivetrain drag. At 220kmh I loose about 20 kilowatts, but on 271kmh it is already 52kw!

 

[AndyH]

You will get out more whp dynoing in 3rd gear than in 5th gear, but always the same brutto hp. It is a simple thing. If the tires spin faster you have more drag, so if the car dirves 220kmh you loose maybe 30hp and at 280kmh you loose 70hp.

ummm.....I don't see how that happen. Drag Force is calculate by multiply drag coef, air density, frontal sectional area and velocity square divided by 2. So on the dyno, your wheel is spinning NOT your whole car. Therefore the drag force is the same if you go 1MPH or 1000 MPH on the dyno which is 0.

 

[austrian type-R]

All I can say is learn to read a Bosh Dynamometer sheet. With DRAG I just mean the power lost in drivetrain and that is higher when driver faster. Look at the line below ZERO in the dynosheet. Telling cars wheel hp means nothing, but I know this will mean war with you US volks, cause you only care about the whp....the whp is changing on the tranny ratio, but the flywheel hp not!

 

[rbirling]

All I can say is learn to read a Bosh Dynamometer sheet. With DRAG I just mean the power lost in drivetrain and that is higher when driver faster. Look at the line below ZERO in the dynosheet. Telling cars wheel hp means nothing, but I know this will mean war with you US volks, cause you only care about the whp....the whp is changing on the tranny ratio, but the flywheel hp not!

Hopefully this won't start a big argument, but technically, hp is preserved through a transmission, except for losses. So whp doesn't change with the ratio, only the torque. hp = torque * speed. The gears lower the speed, raising the torque. The curve might shift left or right, if you plot it by engine speed or wheel speed, though. Whether you care about hp or torque is a discussion I'm not even going to touch online. :smile:

 

[austrian type-R]

hehe, the Tech guy who designed and engineered the Bosch Dyno are for sure knowing what they do.

Look at the Graph. At 260kmh I loose more hp than on 160kmh. The line below zero + the blue line (whp) = hp to the engine.

 

[rbirling]

You're right, and I think we're saying the same thing in two different ways. You are seeing more losses due to the wheels having to spin faster. So you see less measured at the wheels. And of course, the hp being put out by the engine is the same, which is your point.

-- Also, though, the whp is what is measured, I think the _difference_ between whp and bhp is estimated (the lower blue line), so the bhp is actually a calculated number, not necessarily exact, since it isn't being directly measured.

 

[SugrueNSX]

This is a thought provoking topic. What a wonderful forum Prime is, sometimes.
I had not ever thought about how much power is lost in first gear compared to top gear.
As I think we are all agreeing if the wheels are spinning faster they should make more heat and there is more power loss there. In fact any parts of the drive train that spin faster should use up more energy due to some heat loss caused by friction.
But then the next question is which gear is more efficient?
Comparing first gear to top gear is like comparing two completely different gearboxes.
And their efficiency may differ. How much, I don’t know.

Regards,

Patrick