1/4 Mile Time In A Manual

[Turbo6man]

BTW a loss of just 50kw from an engine of 450kw equates to a driveline loss in percentage terms of just over 11. Do you honestly believe that this is realistic?

<{POST_SNAPBACK}>

Did you consider ther power loss to drive the dynamometer, I know what this power loss figure amounts to, do you?

Peter

<{POST_SNAPBACK}>

I don't have to know that. However if I were to think about it I would probably conclude that it would be equal to the frictional losses through one, the contact patch of the tyres and two, the bearings supporting the rollers. And I would expect that the losses would not be as great as the losses experienced by a vehicle driven on the road due to wind drag for one thing.

In any event you have not answered my Q.

Edited 23/02/05 11:12 PM by Forum Director

[aps]

In any event even taking the lower figure we can still equate that to being at least 450fwkw ...

<{POST_SNAPBACK}>

Please tell me how you figure that?

Peter

<{POST_SNAPBACK}>

Mathematically ... can't you do it Peter? I know we've been down this road before but, what the heck, I'll go for another ride with you ...

As most tuners/racers agree that a vehicle equipped with manual transmission will absorb between 15% and 20% of engine power - I have chosen the middle figure of 18% (rounded up from 17.5% for my simple sliderule).

Thus 450 x 18% = 81 ;

450 - 81 = 369.

Now that to me is damn close to the 368 figure you used above while claiming the car couldn't make 450kW at the fly ...

Your serve ... :w00t2:

<{POST_SNAPBACK}>

Drive train loss is not a constant and definetly not a calculated % figure, if you really want to know power at the flywheel there is only one way to find out, it's called an engine dyno and has been for many years, this is how every car manufacturer on the planet measures engine power.

Peter

<{POST_SNAPBACK}>

Heard all that from you before - I was really hoping you'd have something new to bring to the debate.

<{POST_SNAPBACK}>

New or old, this is an engineering fact and is indisputable, if you genuinely want to know the REAL power of an engine then you need to measure the power to the SAE or DIN standard on an engine dynamometer.

Go and ask any car manufacturer on the planet and they will provide you with power and torque numbers measured at the flywheel on an engine dynamometer, not at the wheels on a chassis dynamometer.

Thanks

Peter

Edited 23/02/05 11:32 PM by Forum Director

[BA_Turbs]

So, errr.....

What times were the manual turbos getting down the 1/4 again?

Good job to the manual drivers for trying to keep some of those autos honest!

[Lawsy]

It does seem fairly sound to say that the driveline loss is close to constant if weight was the only issue, but with extra power comes extra frictional forces and therefore extra heat.

So for a 240fwkw falcon, producing 185 ish at the wheels, this might actually be "240kw - 6% (friction, heat + moving the oil around) - 40kw (weight of the components)"..... This isn't accurate, I pulled these numbers from my ass, its just a hypothetical example of what it could be.

In my mind it wouldn't be a constant figure, it can't be. If you apply more force to any contacting surfaces then more friction is going to be apparent, and in turn so is heat. Energy doesn't come free, so power must have been lost to create this extra heat.

But through all this, the weight of the gearbox doesn't change, and there is no way that 20% of the power is being sucked up by friction and heat alone.

Think about it.

Lets say in a low friction system that you have a massive 1 tonne inertial wheel (like one of those massive balance wheels on some old deisels, big ass flywheel) connected to an engine with say 500hp measured after the wheel. If you then measure it from the output shaft of the engine, you mght find this thing happens to have 600hp (yes, I know its probably not right, but shush, im getting somewhere!).

So the extra mass of the wheel sucked up about 100hp. Put a 1000hp engine now on the same wheel, and measure the loss. You'll probably find its close to 900hp measured after the wheel.

So from having to turn the mass, 100hp was lost. Now in a manual box, the mass doesn't change just because you increase the hp. Only the friction changes. So from the weight of the gearbox alone, there should be a close to constant loss in turning the components. The rest, friction and heat.

You could possibly find out what the powerloss due to heat is. Friction directly converts work/power to heat, agree? Get a stock T. Get the gearbox temp to a normal running temperature, measure it. Do a power run and hold the engine at peak power for a minute. Measure the temp and the power.

Gain 100kw at the flywheel (wouldn't you love it to be that easy?). Repeat, get the normal temp exactly the same, pull the run, hold for a minute, measure temp.

I guarantee you that the temp of the box will be higher, significantly higher.

You could measure roller bearing temp, tyre temp and everything.

Convert all this data gathered to BTU's or Joules, do a few simultainious differential equations and you can directly convert this to how many KW you lost.

If done correctly, with the uttmost care for accuracy and control of the variables, this should infact give you very close to to a real figure.....

But hey, I just enjoyed thinking about it in my otherwise boring day (I'm injured and can't move, going to watch movies and read for the rest of the day). I just hope someone out there could learn something, or maybe even correct me as I just may be completely full of crap and forgotten everything from first year.... In either case, have a good one!

[Turbo6man]

In any event even taking the lower figure we can still equate that to being at least 450fwkw ...

<{POST_SNAPBACK}>

Please tell me how you figure that?

Peter

<{POST_SNAPBACK}>

Mathematically ... can't you do it Peter? I know we've been down this road before but, what the heck, I'll go for another ride with you ...

As most tuners/racers agree that a vehicle equipped with manual transmission will absorb between 15% and 20% of engine power - I have chosen the middle figure of 18% (rounded up from 17.5% for my simple sliderule).

Thus 450 x 18% = 81 ;

450 - 81 = 369.

Now that to me is damn close to the 368 figure you used above while claiming the car couldn't make 450kW at the fly ...

Your serve ...

<{POST_SNAPBACK}>

Drive train loss is not a constant and definetly not a calculated % figure, if you really want to know power at the flywheel there is only one way to find out, it's called an engine dyno and has been for many years, this is how every car manufacturer on the planet measures engine power.

Peter

<{POST_SNAPBACK}>

Heard all that from you before - I was really hoping you'd have something new to bring to the debate.

<{POST_SNAPBACK}>

New or old, this is an engineering fact and is indisputable, if you genuinely want to know the REAL power of an engine then you need to measure the power to the SAE or DIN standard on an engine dynamometer.

Go and ask any car manufacturer on the planet and they will provide you with power and torque numbers measured at the flywheel on an engine dynamometer, not at the wheels on a chassis dynamometer.

Thanks

Peter

<{POST_SNAPBACK}>

I've said it before Peter, I know you are a valuable contributor to the site, both financially and with you and your company's knowledge, expertise and products. However I have difficulty with anyone who cannot remain focused.

ADMIN EDIT

We must all remember that fellow members be treated with common decency that we demand from others. The fact that the answer to a question asked was different to what we expected does not give us the right to make further demands in a rude or disrespectful manner. If at any time you are dealing with a sensitive issue, please pursue the issue via private messages until the issue is resolved to your satisfaction.

By following this straightforward guideline, needless frustration or confrontation will be avoided and I am sure all forum members will appreciate this.

Forum Director

Edited 24/02/05 11:07 PM by Forum Director

[DBOSS]

So what is the quickest XR6T manual in Aus?

[tab]

Nice mining Jeff

[jetute]

probably about 12.3

wonder what it would run with nos

[DAWSEY]

has 11.7 been beaten yet??

[Gavin.K]

I dont know whome do you think it will be Jeff???