How is NASA measuring Horsepower with GPS?

[StealthTT]

I've been told NASA can use GPS to estimate horsepower. I was told the following is measured:

intital velocity

final velocity

distance

time

weight

 

Using those variables you get a formula of:

Work = {Mass x [(Final Velocity - Initial Velocity) / Time]} x Distance

 

I wrote a calculator available to download here:

Right click. Save as.

http://www.ink3s.org/pub/disturbedkorn/GPShorsepowercalculator.xls

 

I ran some tests and the calculator is coming up low. I think it's from aero drag and tire friction, etc. Is NASA using some constants or individual car stats for these variables?

 

Does gearing need taken into account? Some engineering buddies of mine are debating it. There was even a reference to "hand of God".

 

Using some timed runs from a 1/4 mile dragrace I did this summer, the numbers are low using the GPS calculator above. So there are more variables. What's NASA use for a formula?

[drivemusicnow]

There are several other factors.

 

Drag from air could be estimated, if we ASSume all the cars have the same co-efficient of drag. If we base it on Cd = to say, .32 or so. This would inflate the horsepower numbers of very aerodynamic cars, and deflate an aerodynamically challanged cars horsepower figures.

 

Drag from tires. While this is MUCH less important than air resistance, the rolling resisitance of tires adds drag to a vehicle. Sometimes significantly. Again, this could be taken into account however you'll have tires with much higher rolling resistance than others.

 

In the end, you are taking a guess, however it shouldn't be too hard to get that guess damn close. Even so, Anyone competing in a class should understand this variance, and plan accordingly.

 

I would also think the AI method (I think) of Peak Horsepower + Peak Torque divided by Two might be a better way of limiting classes using the power over weight method.

[StealthTT]

drivemusicnow:

 

Yeah, I would assume NASA is using a correction for aero. I wonder if they use different aero numbers for different cars or one constant. Likewise with tires, do they have friction numbers for different tires and pressures or do they use a constant?

 

Further discussion with my friends has produced a theory that it is a differential equation. That's why it looks simple, but the simple math doesn't work.

 

Acceleration = dV/dT, not (Final Velocity-Initial Velocity)/Time.

 

We emailed a friend that does telemetry for professional racing teams. I can't wait to see what he says.

 

But back to NASA. How does NASA do it?

[StealthTT]

A little birdie told me that NASA is using the MaxQData system.

 

True....False.....Is this thing on?

 

I just want to know how to tune my car so I don't make too much horsepower. I want to fit in the rules not exploit them. If there is a large margin of error between NASA's HP measurement equipment and mine, I want to narrow that gap. If I have to buy a "road dyno", so be it.

 

***I just want to know to what stick will my car be measured.***

[Greg G.]

We did use the MaxQData system at the Championships. You are correct in many of your statements. Drag coefficients were not much of an issue when comparing similar 4-door sedans, with similar aero mods and tires. This would be a bigger issue comparing an AWD 911 to an STi, though. The Stealth will have a better CF than the 4-door sedans as well.

 

I guess the best answer is to get dyno'd on a dynojet to make sure you are compliant, buy a MaxQData system to monitor your performance, and don't try to cheat The more experience we have with the system, and the more data we have with different vehicles that we "trust" in their dyno numbers, the more accurate monitoring will be. I like the "hand of God" quote, though. Maybe there's a little voodoo mixed in there too?

[StealthTT]

So did you plug into the MaxQData the gear ratios, tire diameter, etc. for the car???

 

I guess AMS in Chicago is the closest Dynojet to me at 5 hours away. I'll have to book 2 months in advance and save my pennies for the tow. Just yanking your chain.

[jrerin]

Problem is 3 fold

1. AWD car 3000 pounds 300 whp

2. FWD car 3000 pounds 300 whp

3. RWD car 3000 pounds 300 whp

 

 

who has the advantage? The AWD car had more loss of HP through the drive train but should have and advantage on the track....Right???

 

Lets throw in a couple of more variables....Mid engine car, front engine car or rear engine car....now who has the advantage????

 

If it were a totally fair playing field then there would have to be separate classes for all the types of cars....so bottom line NASA has done a very good job of trying to level the playing field... 07 should be better still... will it ever be perfect probably not but as long as we go out and have fun and be safe thats what it is all about. God knows we cannot make a living racing with NASA, SCCA or any other series.... I guess we will seewhat happens November 30th when the new TT rules are out.....

 

Russ

[Shawn M.]

I like the "hand of God" quote, though. Maybe there's a little voodoo mixed in there too?

 

 

No voodoo, just use good old peristrokia!!

[IGZOSTD]

Gee AWD , such a HORRIBLE disadvantage . GMAB

[warrtalon]

Problem is 3 fold

1. AWD car 3000 pounds 300 whp

2. FWD car 3000 pounds 300 whp

3. RWD car 3000 pounds 300 whp

 

who has the advantage? The AWD car had more loss of HP through the drive train but should have and advantage on the track....Right???

 

WHP is WHP - it already takes drivetrain loss into account. That's why the WHP limits for bumping to TTU are higher for 2WD (560) than for AWD (500), or at least that's my guess.

[DaWorstPlaya]

who has the advantage? The AWD car had more loss of HP through the drive train but should have and advantage on the track....Right???

 

Lets throw in a couple of more variables....Mid engine car, front engine car or rear engine car....now who has the advantage????

 

If it were a totally fair playing field then there would have to be separate classes for all the types of cars....so bottom line NASA has done a very good job of trying to level the playing field...

 

Good god, lets not turn this into another SCCA type class war. If one truely want to be fair, all the drivers should go out and drive the same car ... but since that is not realistic ... I think what NASA is doing is great. Letting the different strengths and weaknesses of different cars play out is a wonderful idea. Personally I kinda like it that way ... it brings a sort of variety (spice of life) ... with some cars faster in the straight, some able to stop in a short distance, some fast in corner entry and some fast in corner exit ... Ultimately what matters is the lap times are similar. Now thats fun!

[kbrew8991]

Problem is 3 fold

1. AWD car 3000 pounds 300 whp

2. FWD car 3000 pounds 300 whp

3. RWD car 3000 pounds 300 whp

 

who has the advantage? The AWD car had more loss of HP through the drive train but should have and advantage on the track....Right???

 

WHP is WHP - it already takes drivetrain loss into account. That's why the WHP limits for bumping to TTU are higher for 2WD (560) than for AWD (500), or at least that's my guess.

 

correct.

 

its like asking which is heavier, a pound of lead or a pound of feathers.....

[Shawn M.]

its like asking which is heavier, a pound of lead or a pound of feathers.....

 

 

It really depends on what planet you weigh them on.

[hagakure]

Gee AWD , such a HORRIBLE disadvantage . GMAB

 

Not picking on you Steve:)...but a just a little word about the AWD "advantage" It is an advantage in some circumstances, like grip to jump off tight corners...but in other instances it sucks. the Evo drives like a front-wheel drive car in many instances. It has a 60/40 front to rear weight bias, and without a lot of tweaking understeers like a pig. I guess I'm just a little sensitive, because a lot of folks tend to think these things drive themselves. Mine weighs 3100 pounds (weighed at the last NASA event has about 350 HP to the crank, you can get a little bit more out of the stock turbo, but not much. all of the huge HP eVos are in TTU and TTR already)and I've gone 2:02 at t-hill. Most of that is DRIVING. All of the cars that I am competing with in TTA have as much power as I do, or more, and some have more and stickier tires. So, everyone that drives an Evo is not driving a 550 hp monster with big turbo and 26 pounds of boost...some of us are actually driving the wheels off of what we have! that's my rant for the day, and again, not intended as a poke in the eye to anyone!

[IGZOSTD]

Hi Percy , at least I think its Percy ,

I think at Sears point it is a big advantage as the speed is not so high and plenty of elavation change and turns . I watched the GOTO EVO go around the outside of me into 9 at T-Hill , at the very edge of the track and yes i watched the push , the wheels turned hard left , I could have bet he would hit the dirt rally style , but he hung on the far out side with a good dose of right foot .

I don't think overall it is an advantage , all drive , front drive , rear drive , they all have there +'s and -'s . I have had a few front drive cars and I don't care much for them . never had an all-wheeler though , I think i would like it . but as a hole I don't think it is a disadvantage . Rembember how Audi kicked everyones tail .

I think the car classifacation works out pretty good . I like competing with such a wide range of cars .

Try some dot slicks , they changed the way my car works .

[hagakure]

Hey Steve,

 

I think we are on the same page. AWD is definitely not a disadvantage, my point is that it is not a substitute for not being able to drive...I'm looking forward to running at Infineon next year, as it is just one of 3 tracks ont he west coast I have not driven. Remains to be seen if I can use DOT slicks next yeara nd stay in TTA. I may need to stay with RA-1's.

[IGZOSTD]

You will like Sears Point (Infinion), I one who will always call it Sears Point . I have a lots of time on this track racing bikes. It is my favorite track. With all th eelevation change and off camber it sure is demanding of a driver , rider . I'm not so willing to hang it out there in the car though as at Thunder Hill . Lots of impact zones .

I think you will find it very rewarding .

[zuperdave]

Gee AWD , such a HORRIBLE disadvantage . GMAB

Not picking on you Steve:)...but a just a little word about the AWD "advantage" It is an advantage in some circumstances, like grip to jump off tight corners...but in other instances it sucks. the Evo drives like a front-wheel drive car in many instances. It has a 60/40 front to rear weight bias, and without a lot of tweaking understeers like a pig.

 

and some have more and stickier tires. So, everyone that drives an Evo is not driving a 550 hp monster with big turbo and 26 pounds of boost...some of us are actually driving the wheels off of what we have!

I don't have any idea how it applies to AWD or RWD, but a racer who has a LOT of experience winning in a Honda tells me if I'm not sliding through the corners in my Civic I'm not going fast enough.

[Valhakar]

I think the best example that puts the "AWD if for the unskilled" to rest, happened at 2 different AutoX early on in my experience.

 

Drivers swaping cars after getting into the already over done above "discussion". Neither drive did as well as they would in their own cars, but in both cases the AWD owner had better times. With AWD you get the strengths AND weaknesses of both FWD and RWD. If you are unskilled you can have a Civic understeer from he** in one corner and a Fbody over steer in the next.

 

Having driven an RX-7, an Acura, and now my WRX, I can say that my pokey 50/50 split is driven more like the RX-7. It is all about loading up that rear tire while keeping the front from lifting too much.

 

A real disadvantage I have over a RWD. When I do add to much load on the rear, the front lifts up and one wheel spins like made burning off tire AND bleeding about 50% of my power. Keeping the car on the line at that point is tricky to say the least.

[Chuck McMillion]

There are several other factors.

 

Drag from air could be estimated, if we ASSume all the cars have the same co-efficient of drag. If we base it on Cd = to say, .32 or so. This would inflate the horsepower numbers of very aerodynamic cars, and deflate an aerodynamically challanged cars horsepower figures.

 

 

 

 

.

 

IMHO!!!!

aero should be a constant.

 

look at TTB for example.

 

the Corvettes are by far better in aero than the STi/Evo's etc..

 

so with power being equal.. the corvette should be able to accel quicker... and decel quicker..

 

if power was calculated via GPS with out any aero index... it would provide an even more level playing field..

 

this would help limit power to a lower level than their brick-like competitors... and allow the brick like competitors to have more power...

 

Bear in mind, this is only a rough idea... as accel works on a curve... which changes very differently based on which ever drag co-effiecient you use.

[Shawn M.]

 

look at TTB for example.

 

the Corvettes are by far better in aero than the STi/Evo's etc..

 

so with power being equal.. the corvette should be able to accel quicker... and decel quicker...

 

Lets say for the sake of discussion that both cars weigh the same, same power, same tires and brakes and even the exact same driver.

If the car is aero slicker and gets thru the air better, how does this aid in decell/braking?

[Bart Carter]

...the Corvettes are by far better in aero than the STi/Evo's etc..

 

so with power being equal.. the corvette should be able to accel quicker... and decel quicker...

Actually, Corvettes would be able to accelerate quicker and would decel slower. Deceleration for the STi/Evo would be enhanced by air resistance.