[Torgus]

Trap speed can be inflated...it also is traction dependant.

[Taskmaster]

Originally Posted by Torgus

Trap speed can be inflated...it also is traction dependant.

Nah.

[hassmaschine]

Originally Posted by Torgus

Trap speed can be inflated...it also is traction dependant.

Uhhh.. OK. Says you, but that flies in the face of what, 60 years of drag racing? How exactly can you inflate your trap speed? It takes X amount of power to accelerate mass M to Y speed in Z distance. Basically, F = MA. You can't fudge it.

You can have widly varying ETs (traction, driver dependent) but for a given power to weight ratio, the trap speed will be consistent, because you are always accelerating the same mass the same distance.

Traction makes no difference unless you're spinning all the way to the end of the track - which no E90 is going to do, 335i or not.

But keep on trolling the N52 forum...

[mike-y]

trap speed is usually the most consistent 1/4 mile stat. unless you really, really botch up the launch, your traps are going to be very very close to each other, provided you aren't changing tires between runs.

[Torgus]

If you spin off the line it usually inflates your trap speed. This becomes even more apparent the more power you are making. This well known. A poor 60 foot will generally inflate your mph however it is possible to even lower it.

The fastest S55 1/4 mile time comes with the most wheelspin and that the quickest S55 1/4 mile time comes with the best 60 foot time.

If you disagree go ask the holder of the e9x trap records.

I will agree it's usually the most consistent but it can be affected by traction.

[hassmaschine]

OK. I'd like to know how you can "make" a car accelerate faster through a given distance with the same power and weight. You're not going to make more than a 1mph or two difference unless you really screwed something up.

F = MA. It's like grade school level physics..

[anjuna]

Originally Posted by hassmaschine

OK. I'd like to know how you can "make" a car accelerate faster through a given distance with the same power and weight. You're not going to make more than a 1mph or two difference unless you really screwed something up.

F = MA. It's like grade school level physics..

uh, gearing?

[hassmaschine]

well, you're multiplying torque. but power doesn't change.

again, we're talking speed here - not time.

[weehe126]

Originally Posted by hassmaschine

well, you're multiplying torque. but power doesn't change.

again, we're talking speed here - not time.

Just think about it logically. You grip and have a great 60' time. You effectively left the line starting at 0mph.

Or

You roast the tires and by the time you grip you are effectively leaving the line at 5mph. You have gained 5mph and used 0 distance.

[hassmaschine]

You cant leave the line at a speed higher than zero. Unless you believe in teleportation... How did you get from 0 to 5mph? Did you accelerate at the speed of light?

Its sad how weak basic physics knowledge is.

[Mavus]

Originally Posted by hassmaschine

You cant leave the line at a speed higher than zero. Unless you believe in teleportation... How did you get from 0 to 5mph? Did you accelerate at the speed of light?

Its sad how weak basic physics knowledge is.

haha A+ student above

Used 0 distance at 5 mph velocity hahaha superb!!

[Hobbs64]

This forum is always good for a laugh or two. Hass, you are the man!

[PhaseP]

Be careful while you guys laughing at others mistakes you don't notice your own. Power is not force for instance. The force that moves the mass of the car is the torque at wheel times radius of the wheel. Torque at wheel is total power train gear ratio at current gear times engine torque. (ignoring gear friction)

Anyways engine torque is not constant, it is varies by engine rpm. Engine rpm is directly tied to vehicle speed through gear ratio.

So it is not very simple, but it is not too complicated either.

But in the end the final speed at distance x will be the integral of the acceleration of the car from start to end. Instantaneous acceleration of the car will be engine torque at rpm for the speed times total gear ratio for the gear times wheel radius divided by mass of car. Assuming tires are not slipping and ignoring air resistance and friction on gears (loss factor), and speeding up of the gears and etc.

You take the torque curve, transmission gear ratios, final drive ratio, wheel radius and mass of car, start calculating and integrating acceleration from start to end, then you get the end speed at x distance.

Of course at what point gear is changed will change the result. If tires sleep will effect the result too. Tire sleep makes it more complicated, when does it hook up after it slips, and which rpm? What is tires friction coefficient when it is slipping? That would determine how much still acceleration while slipping. And probably other complexities come in.

I think people thinking trap speed is directly determined by horsepower is thinking or based on a very simplified model.

Like this: start with assuming the force (thrust force) on the car is constant, which means engine has constant torque curve. Don't bother with need to change gear due to rpm limit on engine, assume no red line.

Then work done is F times distance. All work done goes to kinetic energy, road if flat, then 1/ 2 m x v2 = F x Distance

v = square root ( 2 F Distance / m )

From such simplifications, high F (engine torque) with low m will have high trap speed (v at distance D)

But again that is assuming engine torque is constant, and no gear change is required all the way. And no to mention any complication of losing traction and when gaining back and other stuff.

[weehe126]

Originally Posted by hassmaschine

You cant leave the line at a speed higher than zero. Unless you believe in teleportation... How did you get from 0 to 5mph? Did you accelerate at the speed of light?

Its sad how weak basic physics knowledge is.

I tried to simplify it for you to understand. I guess it is understandable that you don't understand, since a N52 can't spin it's tires to increase trap speed anyways.

[hassmaschine]

PhaseP, thanks for the detailed explanation. All of that is definitely true. But the reality is, it doesn't add up to a whole lot. We aren't talking about changing multiple variables at once - just the power output of the engine.

Even accounting for all those variables, if the same driver takes the same car down the strip 10 times - they could get 10 very different ETs, but unless they really screw up the trap speed will be very consistent.

Leaving the line at 5mph though. I have to laugh again at that. If you know how to do that you should be working for NASA.

[hassmaschine]

Originally Posted by weehe126

I tried to simplify it for you to understand. I guess it is understandable that you don't understand, since a N52 can't spin it's tires to increase trap speed anyways.

Ok man. If you think so... Your ad hominem attack certainly adds credibility to your theory.

There's another theory you should look up - its 100 years old now. Something about matter and accelerating faster than the speed of light.

[weehe126]

Originally Posted by hassmaschine

Ok man. If you think so... Your ad hominem attack certainly adds credibility to your theory.

There's another theory you should look up - its 100 years old now. Something about matter and accelerating faster than the speed of light.

The sad part is that you don't want to accept facts. You keep saying "physic" is your rationale. But in reality physics is what proves myself and others right. Please go actually look into drag racing trap speeds and their correlation to 60' times. You will realize my "breaking light speed" example is a pretty simple way to explain it.

[Torgus]

Now that we have agreed that trap speed can be affected by traction and water is wet perhaps we can talk more about the supercharger?

What specific supercharger is it? Knowing that will let you know the real limits when you goto smaller pulleys. I'm guessing no one has had a pulley made?

[justin1180]

Originally Posted by Torgus

Now that we have agreed that trap speed can be affected by traction and water is wet perhaps we can talk more about the supercharger?

What specific supercharger is it? Knowing that will let you know the real limits when you goto smaller pulleys. I'm guessing no one has had a pulley made?

it's a vortech V3 supercharger with 115mm pulley. you can go directly to vortech's website and buy different size pulleys.

[desertman123]

This is why I still lurk e90post

[justin1180]

well, it took two weeks but the kit finally shipped. supposed to be delivered thursday. but I will be out of town half of this month so i'm not sure when I will have time to do the install.

[Eagle1oh7]

Originally Posted by justin1180

well, it took two weeks but the kit finally shipped. supposed to be delivered thursday. but I will be out of town half of this month so i'm not sure when I will have time to do the install.

Hope to see what results you get...