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500kw Rb25det

Gta51

By Gta51,
in Engines & Forced Induction

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Ryan1200 Proficient

Ryan1200

Posted
Posted

ETs have always indicated setup, MPH have always indicated power

Nothing has changed.

Dynos lie, MPH don't.

Power and setup will make a difference in MPH

For example if we have 2 cars with 450awkw, one with -5's and a dog box and one with a Gt42 and standard gearbox with a clutch that won't shift at high rpm the car with the -5 will trap higher obviously.

The guys with the 500kw dyno graphs trapping 125mph very well could have that power but might not have the tyres, clutch, gearbox, powerband, driver to use it properly.

Kinkstaah Grand Master

Kinkstaah

Posted
Posted

^---- that is the truest of all.

Other numbers, lap times. It's all just numbers. It's all just some kind of respresentation of some aspect of the car. You can think of the drag strip as either an "advanced dyno" or a reason to live.

  • Like 1
XGTRX Veteran

XGTRX

Posted
Posted

Agree to disagree.

Statistically speaking a 300kw a gtr should trap at 120mph approximately. So when talking of any other cars with similar weights they are always in the ball park with a half decent setup for traction and drive line.

The big variable is usually ET, but mph is always there or thereabouts.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Power and setup will make a difference in MPH

For example if we have 2 cars with 450awkw, one with -5's and a dog box and one with a Gt42 and standard gearbox with a clutch that won't shift at high rpm the car with the -5 will trap higher obviously.

The guys with the 500kw dyno graphs trapping 125mph very well could have that power but might not have the tyres, clutch, gearbox, powerband, driver to use it properly.

So the reason there MPH is down to mechanical issues there, easily explained and logical. :thumbsup:

Ryan1200 Proficient

Ryan1200

Posted
Posted

So the reason there MPH is down to mechanical issues there, easily explained and logical. :thumbsup:

I went from a Ppg dog box 400rwkw setup that trapped 131 to a standard box slowly shifting with a easy launch down to 126mph exact same power.

Just saying there's a bit more to it then rolling out with a certain hp and running X mph.

STATUS Grand Master

STATUS

Posted
Posted

ETs have always indicated setup, MPH have always indicated power

Nothing has changed.

Dynos lie, MPH don't.

No 100% correct.

same car 2 different tyres *10-15mph difference... same day same driver. Changing from 215 nankangs to 255 et streets didnt magically make any more power.

Gone are the average days of a bit of spin then grip enough to cross the line.... half the "average" turbo cars nowadays will powerskid 400m no sweat... and cross the line way off the optimum MPH.

  • Like 2
XGTRX Veteran

XGTRX

Posted
Posted

Agree to disagree.

Statistically speaking a 300kw a gtr should trap at 120mph approximately. So when talking of any other cars with similar weights they are always in the ball park with a half decent setup for traction and drive line.

The big variable is usually ET, but mph is always there or thereabouts.

No 100% correct.

same car 2 different tyres *10-15mph difference... same day same driver. Changing from 215 nankangs to 255 et streets didnt magically make any more power.

Gone are the average days of a bit of spin then grip enough to cross the line.... half the "average" turbo cars nowadays will powerskid 400m no sweat... and cross the line way off the optimum MPH.

As I said in the post above. A half decent setup for traction and driveline will see mph there or thereabouts. This means a good set of tyres at least obviously.

My point being, if someone quotes a dyno figure, then the next question is what mph did it run. If its lower than the expected range with a fair 1/4 mile run, then the power level needs to be questioned.

Well that's the way I have always confirmed my cars and everyone I know does the same thing.

So in the case above did the final mph support the dyno numbers?

scotty nm35 Grand Master

scotty nm35

Posted
Posted

Same goes for running semi's on a roller dyno and strapping the car down hard, no-one will be interested when you run 50kw less than your projected output.

Some cars are setup for drag and some aren't. It's less reliable than the dyno figures you are trying to prove misleading imo.

Stixbnr32 Rising Star

Stixbnr32

Posted
Posted (edited)

^ thats a fair call.

BUT what you are missing if you just take off normally at a drag strip your MPH will still be similar at a given weight/power ratio.

Doesn't matter on setup and if you are in a GTR you will have traction unless you are running silly power and really poor rubber.

That is how the online MPH calculators work and they are pretty good.

DISCLAIMER: This doesn't take into account bad driving etc.

Remember doesn't matter if you win by an inch or a mile.

Edited by Stixbnr32
  • Like 1
tricstar Mentor

tricstar

Posted
Posted (edited)

^ thats a fair call.

BUT what you are missing if you just take off normally at a drag strip your MPH will still be similar at a given weight/power ratio.

Doesn't matter on setup and if you are in a GTR you will have traction unless you are running silly power and really poor rubber.

That is how the online MPH calculators work and they are pretty good.

DISCLAIMER: This doesn't take into account bad driving etc.

Remember doesn't matter if you win by an inch or a mile.

So did you not read Ryan1200's post a few up about exact same power, just different gearbox and 5mph difference??

So it does matter on set up etc and is not just all about what power you run.

Your online calculator can't take differences like a dog vs normal H pattern into account.

More to it than X power runs X mph

Edited by tricstar
jet_r31 Mentor

jet_r31

Posted
Posted

With manual gearboxes.... Power under the curve drastically changes mph,not just the peak , with autos because the converter setup properly is spinning the motor in its sweet spot constantly

its easier to use mph vs power.

Its still a good marker regardless...many problems have been found at a dragstrip vs a dyno due to mph being off. Boostleaks are a big one. A car will run hard to 1/2 track and drop

mph big time in the back half.

cheers

darren

Stixbnr32 Rising Star

Stixbnr32

Posted
Posted

Yeah but then we are talking ratios and driver performance (slow gear changes) if you are changing gearboxes.

Lets not get into that - we all know a seq can change quicker than a H pattern and you will most likely end up with higher MPH.

I know I have contradicted myself here a little but lets compare apples with apples.

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