Hammond drives the GT500

[Nethead]

Oh Nethead, are you around?

That's 1'30.0" for the 500bhp Mustang.? 1'30.1" for the 400bhp Monaro (that's a GTO).? You tell me which handles better.

Raza: Hey, RazDude!  Yeah, I just got into this thread a little bit ago.  All this shows us is how abysmally Pontiac fucked up a perfectly good Monaro--but all of us knew that already...

Holden Monaros were the Australian currency equivalent of around $50,000 US in Australia, per info provided by our forum participants in Australia.  I guess they stripped out some $16,000 (musta been more, considering the cost of shipping an entire vehicle across the Pacific) of the good stuff before they ship them to the US to get them to list for $34,000 or so here.  Of course, Pontiac added some badges and interior trim, which greatly offset the loss of the good stuff they stripped out before they shipped the Monaros here to be rebadged... 

With all the good stuff taken out, Holden probably insisted that they not be called Holdens nor Monaros in the watered-down US versions.  I certainly support Holden on that one, as anyone would...

So, a $50,000 (not US specs) Monaro only got beat by a $40,930 GT500 (built to US specs--the only way they build them so far unless you get the 620 HP Hennessey KR600 version of the GT500) by a tenth of a second around some track somewhere?  But of course, if the Monaro WAS to be built to US specs like the GT500, it probably would perform a little differently than a non-US-specs Monaro--Hey, wait a minute--they DID build a Monaro to US specs, didn't they?  We know the results of that one from the GTO/SRT8/GT500 comparo, don't we?

Hey, ChrisV will tell you it's because the GT500 had better tires!  It's always because the faster vehicle had the better tires... 

And Leblowski will tell you it's because the slower car had 37-year-old racing tires!  Obviously, the Monaro in the comparo had 37-year-old racing tires...

I wish there were "export specs" GT500s to compare to non-US-specs whatevers--the Hennessey KR600 version of the GT500 is probably the closest vehicle to what an "export specs" GT500 would be like, but the Nethead here has not seen any performance figures for a KR600.  Expect them to be fast...on roadrace courses, dragstrips, wherever...

OTOH, the plain-vanilla GT500 can outrun every four-wheeled vehicle I've ever owned and quite likely every four-wheeled vehicle anyone else owns in these forums, too.  That being the case, what else we got?

 

[Rich]

Is there an ignore function on these forums?

[SVT666]

Raza: Hey, RazDude!? Yeah, I just got into this thread a little bit ago.? All this shows us is how abysmally Pontiac fucked up a perfectly good Monaro--but all of us knew that already...

Holden Monaros were the Australian currency equivalent of around $50,000 US in Australia, per info provided by our forum participants in Australia.? I guess they stripped out some $16,000 (musta been more, considering the cost of shipping an entire vehicle across the Pacific) of the good stuff before they ship them to the US to get them to list for $34,000 or so here.? Of course, Pontiac added some badges and interior trim, which greatly offset the loss of the good stuff they stripped out before they shipped the Monaros here to be rebadged...?

With all the good stuff taken out, Holden probably insisted that they not be called Holdens nor Monaros in the watered-down US versions.? I certainly support Holden on that one, as anyone would...

So, a $50,000 (not US specs) Monaro only got beat by a $40,930 GT500 (built to US specs--the only way they build them so far unless you get the 620 HP Hennessey KR600 version of the GT500) by a tenth of a second around some track somewhere?? But of course, if the Monaro WAS to be built to US specs like the GT500, it probably would perform a little differently than a non-US-specs Monaro--Hey, wait a minute--they DID build a Monaro to US specs, didn't they?? We know the results of that one from the GTO/SRT8/GT500 comparo, don't we?

Hey, ChrisV will tell you it's because the GT500 had better tires!? It's always because the faster vehicle had the better tires...?

And Leblowski will tell you it's because the slower car had 37-year-old racing tires!? Obviously, the Monaro in the comparo had 37-year-old racing tires...

I wish there were "export specs" GT500s to compare to non-US-specs whatevers--the Hennessey KR600 version of the GT500 is probably the closest vehicle to what an "export specs" GT500 would be like, but the Nethead here has not seen any performance figures for a KR600.? Expect them to be fast...on roadrace courses, dragstrips, wherever...

OTOH, the plain-vanilla GT500 can outrun every four-wheeled vehicle I've ever owned and quite likely every four-wheeled vehicle anyone else owns in these forums, too.? That being the case, what else we got?

?

I think you make shit up as you type.

[Lebowski]

Raza: Hey, RazDude!? Yeah, I just got into this thread a little bit ago.? All this shows us is how abysmally Pontiac fucked up a perfectly good Monaro--but all of us knew that already...

Holden Monaros were the Australian currency equivalent of around $50,000 US in Australia, per info provided by our forum participants in Australia.? I guess they stripped out some $16,000 (musta been more, considering the cost of shipping an entire vehicle across the Pacific) of the good stuff before they ship them to the US to get them to list for $34,000 or so here.? Of course, Pontiac added some badges and interior trim, which greatly offset the loss of the good stuff they stripped out before they shipped the Monaros here to be rebadged...?

With all the good stuff taken out, Holden probably insisted that they not be called Holdens nor Monaros in the watered-down US versions.? I certainly support Holden on that one, as anyone would...

So, a $50,000 (not US specs) Monaro only got beat by a $40,930 GT500 (built to US specs--the only way they build them so far unless you get the 620 HP Hennessey KR600 version of the GT500) by a tenth of a second around some track somewhere?? But of course, if the Monaro WAS to be built to US specs like the GT500, it probably would perform a little differently than a non-US-specs Monaro--Hey, wait a minute--they DID build a Monaro to US specs, didn't they?? We know the results of that one from the GTO/SRT8/GT500 comparo, don't we?

You have no clue what you're talking about and you completely f-ed up the facts here, as usual, comparing apples to oranges.

On a like for like basis, and expressed in US$, essentially ALL cars are significantly more expensive in Australia than in the US (just as ALL cars are significantly more expensive in the UK than they are in the US).? And it's not because they add or remove x thousand dollars of "good stuff" when they ship them overseas, it's the market dynamics.? A non-z06 corvette can cost the equivalent of $100k in the UK, for example, and they don't add anything to it (other than different spec brake lights and stuff like that).? You can NOT take an Australian price and compare it to a US price when talking about value.? The US version of the GTO is essentially identical to the monaro, which essentially matched the GT500 around their track, which is a fact.?

So no, you can't take the Australian price of one car, the US price of another car, and then try to imply what's what they both cost in the UK.? The GT500, for example, isn't $40,900 in the UK - hell he even said in the clip it was '30 grand' (that's $60k US), had you been paying attention maybe you would have picked up on that.

Try as hard as you want to bungle the facts by comparing prices across countries, the bottom line is the monaro went around the track as fast as the GT500, the monaro is essentially the same as the GTO in the US, and in the US the GTO was a hell of a lot cheaper than the morbidly obese GT500.



And I never said any car was riding on 37 year old tires, I mis-read the article and thought the car set that lap time 37 years ago, you intentionally extracted that and tried to make it sound like I said something that I didn't, stop putting words into other peoples' mouths.

[SVT666]

The US version of the GTO is essentially identical to the monaro, which beat the GT500 around their track, which is a fact.?

I hate to do this because you were on such a roll, but......the GT500 beat the Monaro around their track by 0.1 of a second.

[Lebowski]

I hate to do this because you were on such a roll, but......the GT500 beat the Monaro around their track by 0.1 of a second.

Fixed.   

[SVT666]

Fixed.? ?

The only problem with their testing is that the tests are done on different days.  I've seen them test on super cool days, rainy days, and on scorching hot days.  The cars running on the super hot days will generate more grip but engine power suffers.  On the cool days the cars don't get as much grip but they produce more power.  The rainy days speak for themselves.

[LonghornTX]

The only problem with their testing is that the tests are done on different days.  I've seen them test on super cool days, rainy days, and on scorching hot days.  The cars running on the super hot days will generate more grip but engine power suffers.  On the cool days the cars don't get as much grip but they produce more power.  The rainy days speak for themselves.

X2.

[565]

What's odd is that they had their 10,000GBP supercars tested on that kind of dyno and knew enough to convert it.

Also, wouldn't they dyno operators know to say something?

Actually I read something interesting over at SVTperformance.com

Some guy from England basically said that the convention around there is to convert to flywheel HP before you report the number, unlike the convention here, where you just report RWHP.?

So there is a possibility that 447 HP reading was the product of some flywheel conversion equation they used, and thus indeed flywheel HP instead of RWHP.? Which means the actual RWHP reading must have been pretty low for a GT500 (lower than 400 probably).? I think there are a few possibilities here, in increasing order of probability.

1)? The GT500 they had was tired and abused.? This is supported by the fact this GT500 is the same color as the one they tested in 5th Gear, which is probably not concidence.? I would bet there aren't too many tester GT500's in Britain and they've all been severely beaten on.? This could have been that same car, and probably beaten like a dog by every British magazine journalist.

2)? The GT500 was broken in some way.? It is less far fetched than it seems considering many of the early tester GT500's were defective.? C&D got a defective convertible to test as well as a slightly defective coupe in their VIR comparo.? Edmunds got a defective one for their testing as well.? They were all making less power than expected.? Top Gear is filmed far in advance, and there is the possibility this early GT500 also suffered from some problems.

3)? Heat soak.? Massive Heat Soak.? I remember early GT500 dynos coming in around the low 400hp mark due to mild heat soak from either just previous pulls on the dyno or driving the car in.? GT500's put down better numbers after some cool down.? I see that Top Gear wheeled their Dyno out onto the freaking track.? Now that just appears like they were seriously strapped for time with this car, because the usual place for a Dyno is not in the middle of an airfield.? I am willing to bet Top Gear only had a limited amount of time with this car, and had to fit a road review, dyno test, and test lap all into a day.? So the solution was to film it all at the track (instead of scenic locations) and also bring the Dyno to the track to save time.? So while normal GT500's suffered heat soak from previous normal driving to the Dyno shop, this GT500 could have very well been doing long power slides and powering around that track right before they rolled it onto the Dyno.? That GT500 could have been suffering from heatsoak on a totally diffferent level before being put into the Dyno.


I think these 3 factors may offer some explanation of why they reported such a low HP rating.? ?Otherwise if we take the 447HP as a RWHP rating, this dyno is among the best recorded for a stock GT500.? I just don't see Top Gear taking the care for sufficent cool down to achieve those numbers. I mean Jeremy doesn't even bother to get the facts straight about the GT500 (no LSD he thinks).




Edit:  I checked the Fifth Gear video.  They used the same GT500, license plate M500 FMC.  Also the one they had in the Top Gear studio was the same car M500 FMC in the video.  Top Gear usually puts a car of different color in the studio compared to the one they video test (no idea why).  I think there are probably very few GT500's to test in the UK.  Maybe this M500 FMC plated one is the only one, which means it has endured all of the journalist abuse.

[GoCougs]

No.? Mustangs have 12% drivetrain loss.? Evidenced by most GT500's have between 440 and 445 rwhp and regular Mustang GT's dyno at 265 rwhp.? 12% drivetrain loss pegs the GT at 300 crank hp and the GT500 at 500 crank hp.? Drivetrain loss is from the moving parts and how much force is required to turn or move those parts.? That's why an aluminum lightweight driveshaft and flywheel will lower the drivetrain loss and the wheel horsepower will go up without the engine crank horsepower increasing.

Actually, a lighter flywheel and/or driveshaft will not result in more RWHP as they are not a factor in efficiency. Items that have friction or drag such as bearings, gears, AT fluid pumps, etc., whittle away at RWHP.

[GoCougs]

It also puts down 20 more hp at the wheels. There's no way a Mustang GT has that little drivetrain loss. Most 911's have about a 15% loss, I don't see how a FR layout Mustang could have even less than that.

Drivetrain losses will vary by vehicle as each vehicle has different tranmissions, rear ends, bearings, etc.

A 2WD one-ton pickup w/AT will have quite a bit more losses versus a Mustang GT w/AT even though each has the same number and type of drivetrain components.

[SVT666]

Actually, a lighter flywheel and/or driveshaft will not result in more RWHP as they are not a factor in efficiency. Items that have friction or drag such as bearings, gears, AT fluid pumps, etc., whittle away at RWHP.

The weight of the parts that have to turn or move also has a bearing.  Everything the engine has to turn or move is part of the drivetrain loss.  That's why a lightweight flywheel and driveshaft will "free up" horsepower.  The lighter they are the easier they are to turn and will result in more power getting to the ground without actually upping the horsepower in the engine.

On a side note: The supercharger in the GT500 requires 120 hp just to operate.  The GT500 engine actually produces in the neighbourhood of 620 hp, with 120 of that total is used just to turn the supercharger, leaving 500 hp for the rest of the car.  That's one of the reasons a turbo pushing the same PSI will get a lot more power out of an engine then a supercharger.

[GoCougs]

The weight of the parts that have to turn or move also has a bearing.? Everything the engine has to turn or move is part of the drivetrain loss.? That's why a lightweight flywheel and driveshaft will "free up" horsepower.? The lighter they are the easier they are to turn and will result in more power getting to the ground without actually upping the horsepower in the engine.

That simply is not true. Only at points of mechanical interface are sources of inefficiency; up to an including CV and U joints (albeit very, very small in this case).

Lighter drivetrain components can equate to less inertia and hence the ability to rev faster,  but that is not increasing efficiency, or RWHP.

[The Pirate]

That simply is not true. Only at points of mechanical interface are sources of inefficiency; up to an including CV and U joints (albeit very, very small in this case).

Lighter drivetrain components can equate to less inertia and hence the ability to rev faster,  but that is not increasing efficiency, or RWHP.

But wouldn't that efficiency increase tranlsate into more power being transferred to the wheels?  It makes sense to my engineering illiterate brain.

[GoCougs]

But wouldn't that efficiency increase tranlsate into more power being transferred to the wheels?? It makes sense to my engineering illiterate brain.

Yes, you have it right. Greater efficiency is formally stating that more power is transferred to the drive wheels.

I'm not sure though of the efficiency increase you mention.

[SVT666]

That simply is not true. Only at points of mechanical interface are sources of inefficiency; up to an including CV and U joints (albeit very, very small in this case).

Lighter drivetrain components can equate to less inertia and hence the ability to rev faster,? but that is not increasing efficiency, or RWHP.

Hence, it is freeing up power that can be transfered to the wheels.  If less power is required to turn a lighter flywheel or driveshaft, then more of that power is making it to the wheels. 

[Soup DeVille]

That simply is not true. Only at points of mechanical interface are sources of inefficiency; up to an including CV and U joints (albeit very, very small in this case).

Lighter drivetrain components can equate to less inertia and hence the ability to rev faster,? but that is not increasing efficiency, or RWHP.

Cougs, you have to realize that people are generally not interested in the steady state power of their cars. They want to know how fast they will accelerate. Lower drivetrain inertia means however much less of the work the engine does to accelerate the drivetrain means a greater percentage of it goes to accelerating the vehicle as a whole.

And, because 99% of chassis dynos are read horsepower by measuring the effective acceleration induced on the rollers, that means that these inertial based dynos will record a higher RWHP because of lighter driivetrain components.

You are absolutely right that when measured at a constant speed on a water brake dyno there will be no measurable change in HP.

[The Pirate]

Yes, you have it right. Greater efficiency is formally stating that more power is transferred to the drive wheels.

I'm not sure though of the efficiency increase you mention.

I was referring to the lightened components contributing to a more efficient system, albeit worded vaguely.  Anyways, I read up a few posts, and I think my question was answered.

[GoCougs]

Hence, it is freeing up power that can be transfered to the wheels.? If less power is required to turn a lighter flywheel or driveshaft, then more of that power is making it to the wheels.?

But it does not take more power to turn a heavier flywheel or driveshaft.

[Raghavan]

But it does not take more power to turn a heavier flywheel or driveshaft.

At a steady speed, no, but when you're trying to accelerate that driveshaft, it does.

[GoCougs]

Cougs, you have to realize that people are generally not interested in the steady state power of their cars. They want to know how fast they will accelerate. Lower drivetrain inertia means however much less of the work the engine does to accelerate the drivetrain means a greater percentage of it goes to accelerating the vehicle as a whole.

And, because 99% of chassis dynos are read horsepower by measuring the effective acceleration induced on the rollers, that means that these inertial based dynos will record a higher RWHP because of lighter driivetrain components.

You are absolutely right that when measured at a constant speed on a water brake dyno there will be no measurable change in HP.

I guess I wasn't thinking of the typical chassis dyno test rig.

Those types of dynos will record a higher RWHP, but by the most fundamental engineering definitions, the change is false and therefore does not exist. The system should allow the operator to alter the change in inertia. Perhaps some do.

[GoCougs]

At a steady speed, no, but when you're trying to accelerate that driveshaft, it does.

Does stripping 500 pounds off your car increase increase its RWHP simply because it will accelerate faster?

Less weight and/or less inertia does not increase power for then you are then stating that you are creating energy by doing so.

It appears that SdV cracked the code in the misunderstanding in that chassis dynos apparently don't factor in changes in inertia (which is a funtion of weight) thereby falsely showing an increase in RWHP with lighter components.

[Raghavan]

Does stripping 500 pounds off your car increase increase its RWHP simply because it will accelerate faster?

Less weight and/or less inertia does not increase power for then you are then stating that you are creating energy by doing so.

That's exactly what you and a few others are stating. And it sounds like SdV cracked the code in the misunderstanding in that chassis dynos apparently don't factor in changes in inertia (which is a funtion of weight).

Yeah, but I never said that you'd be gaining more horsepower that way.

[GoCougs]

Yeah, but I never said that you'd be gaining more horsepower that way.

Your hypothesis (takes more power to accelerate a heavier driveshaft) is identical to stating that you'd gain power by removing weight from the driveshaft (which is identical to my 500 lb analogy).

[Raghavan]

Um... you're confusing me now... I'm leaving this thread. Bye.

[MX793]

Hence, it is freeing up power that can be transfered to the wheels.  If less power is required to turn a lighter flywheel or driveshaft, then more of that power is making it to the wheels. 

No, it doesn't equate more power at the wheels.  The easiest way to understand the effects of lighter wheels and driveline components is to look at the kinetic energy of these components.  For a non-rotating mass inside the car, the driver for instance, the kinetic energy is simply equal to 0.5mV^2 (the linear motion equation).  However, for a spinning component, the kinetic energy has two pieces, linear motion and rotational motion.  The kinetic energy for a rolling wheel (or other spinning component in the car) is equal to 0.5mV^2 + 0.5Iw^2.  Presuming one can find a relationship between V and w (which you can for a rolling wheel), then it's possible to rewrite this expression in the form 0.5mV^2, but m in this case would be an equivalent mass rather than the actual mass of the component (the equivalent mass would be greater than the actual mass).  In other words, spinning components behave as if they weigh more than they really do when it comes to a vehicle's performance.

Power is the time rate of change of kinetic energy.  The less mass you have, the greater the change in velocity you'll get from a certain amount of power sustained over a certain period of time.  In simplest terms, less mass = more acceleration for the same power.  For a spinning component, the reduction in mass typically results in a reduction in I (moment of inertia) as well.  The change in the linear equivalent mass could wind up greater than the actual reduction in mass.  So the reduction in mass of a spinning component will likely benefit you more than shedding the same amount of weight from a non-spinning component.  Losing 8 lbs by switching to rims that are 2 lbs a piece lighter than stock (but are the same diameter) should do more for you than removing 8 lbs worth of interior trim pieces.

[Soup DeVille]

I guess I wasn't thinking of the typical chassis dyno test rig.

Those types of dynos will record a higher RWHP, but by the most fundamental engineering definitions, the change is false and therefore does not exist. The system should allow the operator to alter the change in inertia. Perhaps some do.

Agreed.

[SVT666]

I guess I wasn't thinking of the typical chassis dyno test rig.

Those types of dynos will record a higher RWHP...

That's what I've been saying all along.

[SVT666]

So the reduction in mass of a spinning component will likely benefit you more than shedding the same amount of weight from a non-spinning component.? Losing 8 lbs by switching to rims that are 2 lbs a piece lighter than stock (but are the same diameter) should do more for you than removing 8 lbs worth of interior trim pieces.

That is all I understood from your post.

[GoCougs]

That's what I've been saying all along.

And my point all along is that an increase in RWHP from lighter drivetrain components is not possible.