1/4 Mile Time In A Manual

[badxr6]

I used the Ray Hall drag calculator and it reckons u need 500Hp ( 373KW ) to run 120mph and should have an ET of 11.37 odd with 3900 Lb.

doesn't add up in the real world though..

I reckon it would be right if all conditions where perfect O and driver

[Lawsy]

Good post macka, but I don't think its that simple. One thing though, pretzel had major clutch slippage off the line and in the 2nd to 3rd shift. He probably would have lost a good 5mph from this.

But anyway.....

Lawsy,

I believe it is that simple. Peter says the track is the true test of power. It's simply mass and energy to propel that mass to a given speed in a certain distance give or take a fewweather varables

your involved with engineering so you no that mathematics don't lie :lol:

macka

Hehe, maths lies all the time mate.... But I do see what you are talking about, but still say that it is not that simple. Watch.

Horsepower is the ability to move a certain weight over a certain distance in a specific timeframe. Or the tractive effort/torque/pulling ability over time. Agree?

So hp is roughly 4.6ts being moved over 1 meter in 1 minute. Or to make it easier, 76.04 kgm/s. From that, you can see that the lack of information makes it impossible to directly calculate how fast a car is going to shoot down the quarter. There is no static or intertial/dynamic friction coefficients, there is no - (v*(drag coefficient)) there. that's just 2 of the big ones, theres probably 20 more that have a significant effect on the outcome of the calculation.

It isn't that simple.

BUT, I do see the merit in your argument. And the simple answer is this. There is more energy being spent turning the gears in an auto then there is in a manual, obviously. But not all of this energy is lost. Between shifts the inertia of the engine helps to regain some of this power and continues to propell the car forward. Also, because on the dyno the engine is allowed to rev allot faster than what it can on the drag strip, the this extra energy difference is slightly less in the real world. It wouldn't supprise me if the torque value of both cars, if you held both Geea's car and BCL's car at 4000rpm, is roughly the same.

Look at BCL's MPH. And then look at how much power he has, I would say with a car of this weight, that the power difference between BLC's car and Pretzels car, would equate to about 6-7mph. Now, take into consideration that pretzel had massive clutch slip on launch, and into 3rd, his mph is spot on where it should have been. With a good launch, and a clean run, his car will easily have around 115mph, or, in a manual, about 290 - 300rwkw.

In a manual, even 112 mph is to quick for 240rwkw. Unless you got it perfect and/or was a little brutal on your driveline.

[aps]

I believe it is that simple.  Peter says the track is the true test of power.  It's simply mass and energy to propel that mass to a given speed in a certain distance give or take a fewweather varables

your involved with engineering so you no that mathematics don't lie  :lol:

macka

<{POST_SNAPBACK}>

Macka, with all due respect, the maths you are reffering to is based upon flywheel, not wheel horsepower. Most of these hp calculator web sites use the simple formula hp = weight * (speed / 234)** 3 where speed is in mph, weight in lb and the resultant flywheel power in horsepower. From there, multiply that figure by 0.746 to convert to flywheel kW.

Some drag calculators also calculate the optimum ET as well, however this figure is often misunderstood because it is heavily influenced by the chassis set up, tyres, traction and of course the driver. For the sake of completeness, this formula is hp = weight / (ET / 5.825)** 3

The terminal speed however is a better guide to the engine's power and is redilly accepted amongst the professional Drag Racing community as being close to the money.

So, with a weight of 3960 lb, to achieve a terminal speed of 120 mph, Craig and Dean need to be producing just over 390 kW at the flywheel (not at the wheels) - which is pretty much where they are now.

Hope this helps clarify the the use of these formulas.

George

[Guest]

I believe it is that simple.  Peter says the track is the true test of power.  It's simply mass and energy to propel that mass to a given speed in a certain distance give or take a fewweather varables

your involved with engineering so you no that mathematics don't lie  :lol:

macka

<{POST_SNAPBACK}>

Macka, with all due respect, the maths you are reffering to is based upon flywheel, not wheel horsepower. Most of these hp calculator web sites use the simple formula hp = weight * (speed / 234)** 3 where speed is in mph, weight in lb and the resultant flywheel power in horsepower. From there, multiply that figure by 0.746 to convert to flywheel kW.

dw ....I think the scoops reason was to get a reply like this from you or peter!

Some drag calculators also calculate the optimum ET as well, however this figure is often misunderstood because it is heavily influenced by the chassis set up, tyres, traction and of course the driver. For the sake of completeness, this formula is hp = weight / (ET / 5.825)** 3

dw.... see even you agree you cant use these calculatores due to the variable's!

The terminal speed however is a better guide to the engine's power and is redilly accepted amongst the professional Drag Racing community as being close to the money.

dw ....but did you not just contradict yourself here? just as the variables make the calc's imposible one way, so go's it the other, as all variables need varification for the calculation?

So, with a weight of 3960 lb, to achieve a terminal speed of 120 mph, Craig and Dean need to be producing just over 390 kW at the flywheel (not at the wheels) - which is pretty much where they are now.

Hope this helps clarify the the use of these formulas.

dw ....yes it does clarify that the use of the formulas with out all the corect figures is futile just as they proved to be in the injector formulas!

George

<{POST_SNAPBACK}>

have a nice day!

[Pretzel]

I believe it is that simple.  Peter says the track is the true test of power.  It's simply mass and energy to propel that mass to a given speed in a certain distance give or take a fewweather varables

your involved with engineering so you no that mathematics don't lie  :lol:

macka

<{POST_SNAPBACK}>

Macka, with all due respect, the maths you are reffering to is based upon flywheel, not wheel horsepower. Most of these hp calculator web sites use the simple formula hp = weight * (speed / 234)** 3 where speed is in mph, weight in lb and the resultant flywheel power in horsepower. From there, multiply that figure by 0.746 to convert to flywheel kW.

Some drag calculators also calculate the optimum ET as well, however this figure is often misunderstood because it is heavily influenced by the chassis set up, tyres, traction and of course the driver. For the sake of completeness, this formula is hp = weight / (ET / 5.825)** 3

The terminal speed however is a better guide to the engine's power and is redilly accepted amongst the professional Drag Racing community as being close to the money.

So, with a weight of 3960 lb, to achieve a terminal speed of 120 mph, Craig and Dean need to be producing just over 390 kW at the flywheel (not at the wheels) - which is pretty much where they are now.

Hope this helps clarify the the use of these formulas.

George

<{POST_SNAPBACK}>

George,

The difference between an Auto and a Manual drag car at the top leve (I'm not talking street car) is probably miniscule (In fact they run manuals at the top don't they anyhow ?)

But for a street car, where as you say chassis and tyres etc are not ideal, there are far too many variables to consider..... Put the motor out of Geea's into a proper drag car, weight them the same, and I guarantee you they will be miles ahead of Geea's times due to the car's setup etc.. (No offence Craig, just an example)

Then put a manual in Geea's car, and it will again be behind his current time (Because he is getting an excellent result, time after time with the Auto !) Use Brian as an example, he admits to not being a great driver, and has figures very slow compared to what the car is capable of doing (according to the calculations)!

So with that being the case, how can you quote a MPH figure as a difinitive indication of a car's performance ? Would it not be just an indication of how good (or bad) a DRIVER is able to use the power the car has ?

Pretzel

[aps]

I believe it is that simple.  Peter says the track is the true test of power.  It's simply mass and energy to propel that mass to a given speed in a certain distance give or take a fewweather varables

your involved with engineering so you no that mathematics don't lie  :lol:

macka

<{POST_SNAPBACK}>

Macka, with all due respect, the maths you are reffering to is based upon flywheel, not wheel horsepower. Most of these hp calculator web sites use the simple formula hp = weight * (speed / 234)** 3 where speed is in mph, weight in lb and the resultant flywheel power in horsepower. From there, multiply that figure by 0.746 to convert to flywheel kW.

Some drag calculators also calculate the optimum ET as well, however this figure is often misunderstood because it is heavily influenced by the chassis set up, tyres, traction and of course the driver. For the sake of completeness, this formula is hp = weight / (ET / 5.825)** 3

The terminal speed however is a better guide to the engine's power and is redilly accepted amongst the professional Drag Racing community as being close to the money.

So, with a weight of 3960 lb, to achieve a terminal speed of 120 mph, Craig and Dean need to be producing just over 390 kW at the flywheel (not at the wheels) - which is pretty much where they are now.

Hope this helps clarify the the use of these formulas.

George

<{POST_SNAPBACK}>

George,

The difference between an Auto and a Manual drag car at the top leve (I'm not talking street car) is probably miniscule (In fact they run manuals at the top don't they anyhow ?)

But for a street car, where as you say chassis and tyres etc are not ideal, there are far too many variables to consider..... Put the motor out of Geea's into a proper drag car, weight them the same, and I guarantee you they will be miles ahead of Geea's times due to the car's setup etc.. (No offence Craig, just an example)

Then put a manual in Geea's car, and it will again be behind his current time (Because he is getting an excellent result, time after time with the Auto !) Use Brian as an example, he admits to not being a great driver, and has figures very slow compared to what the car is capable of doing (according to the calculations)!

So with that being the case, how can you quote a MPH figure as a difinitive indication of a car's performance ? Would it not be just an indication of how good (or bad) a DRIVER is able to use the power the car has ?

Pretzel

<{POST_SNAPBACK}>

Pretzel,

The ET demonstrates how well the driver, chassis and tyres work, the MPH shows the real power of the car.

I'be seen plenty of manual cars run very high MPH though the ET is slow for the MPH, manual or auto trans, if the power is genuine the MPH will be big.

It's my view Deans or Craigs car with a manual trans would run identical or very close to indentical MPH on either a manual or auto trans, if the engine is producing the power (approx 390 FWkW's).

The APS Phase III manual sedan has run 118 to 121 MPH at calder with a low 12 sec ET, no doubt it's not easy to run a quick ET in a manual T though the MPH will always be demonstrated.

Peter

[Guest russ]

Just thought I should add my two cents worth especially as I am an "old" drag racer!

The calculations used for drag racing HP do not include a lot of things. Its actually an old industrial formulae for working out how much horsepower you need to drive various equipment in a fixed period of time.

The difference in drag racing is - the engine is working through an entire rev range in each gear. The calculations for Hp using ET or MPH will show the AVERAGE HP for the time it was accelerating down the track.

It is not unusual to have 500 peak HP but only show 400 HP on the track. Because 400 would be the average power that accelerated the car.

The comment about auto's is a little interesting. Auto's take more power to drive than a manual but often show faster ET's because there is no time lost during gear changes and the revs drop less between gears because the torque convertor will slip a little on gear changes. This keeps the revs a little higher thus making the AVERAGE HP higher as well.

And for all those guys with 2.0 something 60 foot times and 120 MPH speeds - its time to buy some slicks and a decent clutch. It would not be unreasonable to expect a 1.7 or 1.8 60 ft time with that power ( some may find it a little cruel for their baby)

Cheers

Russ

[Guest]

thank you russ I did not know that it was the average and always thought crap but this makes more sense!

[Guest]

Pretzel,

The ET demonstrates how well the driver, chassis and tyres work, the MPH shows the real power of the car.

It's my view Deans or Craigs car with a manual trans would run identical or very close to indentical MPH on either a manual or auto trans, if the engine is producing the power (approx 390 FWkW's).

Peter

<{POST_SNAPBACK}>

now peter hmmm you say mph = real power? of course its in writing!

in your view craigs and deans make aprox 390fwkw average so then by removing 20% that you wanted me to work with do your maths and tell the forum how far out your calcs are or your precious dyno dynamics?

[aps]

dw ....I think the scoops reason was to get a reply like this from you or peter!

DW, you must understand that Macka's confusion was based upon the assumption that the resultant power figure was at the wheels. I don't for one second believe that Macka posted false information simply to provoke a response from APS - which is in all fairness, a post that is of benefit to all members who wish to learn more about the science of drag calculators.

dw ....but did you not just contradict yourself here? just as the variables make the calc's imposible one way, so go's it the other, as all variables need varification for the calculation?

You needn't confuse the affect driver, chassis, tyres, traction etc has on ET compared to the terminal speed. eg, two runs:

10.98 sec @ 124.74 mph versus

11.50 sec @ 124.72 mph

The mph was almost identical but the ET changes significantly - mainly due to how successful the launch was. These factors have a huge affect on ET, but little on terminal speed.

This is the reason why I (and professional drag racers) hold the MPH in high regard as an indication of engine power. It also serves as a useful tool to ascertain whether an engine is operating correctly during a drag meet. If the MPH drops, then something may be astray. ET on the other hand is more often than not an inconsistent indicator due to the great affect the above listed parameters have.

These drag calculators have been around for many years and are well understood by professional drag racers. Whilst not definitive by any means, they are consistent and hence meaningful. Anyone remember the big Moroso wheel that racers used to hold close to their chests?

have a nice day!

<{POST_SNAPBACK}>

You too Nicko.

George