kit choice & Newton's nightmare

[PASHEN]

Hi Brutebogart,

Welcome to the forum. As you can see, we're an excited bunch here and are pretty passionate about our cars and our opinions. Once again, the thread has been highjacked, although unintentionally.

Regarding which kit you want, first determine how much you can afford. Then accept that it will void your factory warranty. Then be prepared for the reality of informing your insurer that you have done some mods. Then be prepared to upgrade some other parts (more $$) of your car to cope with the extra power.

Once you're ok with all the above, go and check out what's available, and more importantly, speak to as many people as you can who have gone down the mod path. Testimonials are the best indication of how good a kit it really is.

My car was the second one in the country to be fitted with an APS Phase III kit, behind 100%. I am completely happy with it, so is my insurer, so are the cops...the same can't be said for every poor sucker that's wanted to take me on. It's completely drivable, completely stealth....and yet so farkin completely fast it'll put a permanent smile on your dial.

p.s See the Motor Magazine Hot Tuners mag - it features the APS Phase III car....and likens it to a true supercar, with a speed limiter removal top speed of 307kph

[bcl]

Rob,

It's actually fairly simple.

Acceleration is a change in velocity over time, velocity is measured at a point in time.

If you are travelling at a contant speed you have zero acceleration.

If your speed increases you are accelerating, although that rate of acceleration can actually be decreasing.

If you are accelerating at a constant rate your speed will be increasing at a uniform rate.

The greater the torque of your car the more capable it will be increase at a either a higher constant rate of acceleration, or, up to a point to increase that rate of that acceleration.... which can be judged by the "shove in your back".... I.e you feel like you're going faster at a faster rate.

For us the rate of acceleration will depend on gearing, and where we are on the torque curve.

It's not smoke and mirrors, just physics.

******

Brian

Edited 20/04/04 03:13 AM by BLKXRT

[Guest Big Mick]

The main flaw in the arguments is the assumption that acceleration is constant.

To be specific:

Re your conclusion 1.

“The initial acceleration used to get a vehicle up to a certain velocity has ZERO effect on braking distance, though in the absence of higher anticipation in reaction times, it may significantly increase reaction distance, therefore total stopping distance.”

The rate of acceleration when you attempt to brake has a major impact on braking distance. The higher the power of the car the higher will be the RATE of acceleration, rather than acceleration being constant. During the reaction time (assuming it is constant) you will travel much further if you are undergoing increasing acceleration rather than constant acceleration. Constant acceleration is assumed in most calculations, largely for the sake of simplicity. In this case it is incorrect.

Conclusion 2.

Since initial velocity (speed at which brakes are applied) and deceleration capability (quality of braking power) are the only 2 variables that affect braking distance, then how much throttle is applied to get to that initial velocity is IRRELEVANT except for the purposes of reaction distance...which is why I advised 100% to get better brakes!

This conclusion assumes zero acceleration and therefore constant velocity, clearly not the case.

Anyone feeling tempted to quote Newton's Second Law relating to Force, Mass, Acceleration etc in an attempt to refute these conclusions is referred HERE to dust off some Physics 101 cobwebs.

Did you actually read the reference that you quoted? It actually refers to the f=ma equation, (via “Work is the force times the distance, and since force is the mass times acceleration”) which IS Newtons 2nd law, and which is very relevant to braking. The higher the force generated by the vehicle, the higher will be the force required to stop the vehicle. The better the brakes, the greater the force that can be put on the vehicle in terms of deceleration to bring it to a stop.

Brian

Brain,

Unless you are driving with one foot on the accelerator and one on the brake, I don't understand how the car can still be accelerating forward while you are braking. Or can you please explain how this acceleration exists?

Cheers,

Mick

[Geeseman]

Like most forums on the internet you get people who become obsessed with a product or brand that they just purchased or are about to purchase for one reason or another, which may include trying to justify their purchase to themselves.

Trying to decide when it becomes a problem is a tough call for the mods of any forum, and I think comments like Bcl's on this matter are pretty spot on. Hey, I've even harped on about brake safety a little more than I should have but who is perfect.

*** geea *** Just stick to what you know and your experience with chiptork stuff and it will all work out.

Best to think of it this way: if someone comes to the forum and reads one post and purchases based on that then good luck to them. 9 times out of 10 they may make the wrong purchase decision. Kudos goes to the person who does some research to back up their purchasing decision and that's what places like this are here for.

*** house keeping

Edited 20/04/04 04:02 AM by BLKXRT

[Grant]

Mick,

Not sure exactly what your question is addressing but I'll take a few different viewpoints for you.

A car that accelerates evenly would have a graph represented by a straight line. The y axis would be speed, the x axis time.

A car that accelerates harder and harder would have a logarithmic curve - like the bottom right quadrant of a circle.

A car that starts off accelerating hard and then the acceleration drops off would have a curve like the top left quadrant of a circle. At all times the car is accelerating, but at the start it is accelerating far harder than at the end.

The other answer you may be after is that if a car is stopping from a constant speed then it is going to have a certain amount of force behind it. If it is at that same speed but still accelerating, it will have more force, and hence require more braking force to stop it. Also, as mentioned earlier, if you are accelerating harder, the amount of distance you cover during your reaction time from taking your foot from the accelerator to the brake is much greater than if you were accelerating slower.

One final point - Peter, I know your kits all provide ADR compliance, but it's safe to say that 90% of the kits you have supplied are "illegal modifications" since the owners of those cars have not yet obtained an engineers certificate!

[Cobra]

Rob,

It's actually fairly simple.

Acceleration is a change in velocity over time, velocity is measured at a point in time.

If you are travelling at a contant speed you have zero acceleration.

If your speed increases you are accelerating, although that rate of acceleration can actually be decreasing.

If you are accelerating at a constant rate your speed will be increasing at a uniform rate.

The greater the torque of your car the more capable it will be increase at a either a higher constant rate of acceleration, or, up to a point to increase that rate of that acceleration.... which can be judged by the "shove in your back".... I.e you feel like you're going faster at a faster rate.

For us the rate of acceleration will depend on gearing, and where we are on the torque curve.

It's not smoke and mirrors, just physics.

******

Brian

Brian,

I hear what you say, but with respect mate, I think you have fallen for "a trick for young players"

the physics that is being quoted is based on the prime example of gravity .... and Isaac was lucky that there weren't too many variables with the apple hitting his head

it is easy to discuss things like the rate of acceleration ... or the shove in the back when we hoof the pedal on the right

but the instant the middle pedal is used and the brakes applied... then there is only a constant velocity at that instant in time

with cars there are a thousand variables like lag or apparant momentum or other such tricks ....

the rate of acceleration might at best be a series of constant accerations changing from instant to instant .... but that is all

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this thread is way of track but interesting

[geea]

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this thread is way of track but interesting

17 people reading at one time must nearly be a record lol. Its very interesting.

Geea.

[aps]

******

I take your accusation that I am **** at home as a personal compliment as he is obviously a very intelligent and astute fellow.

Finally every forum member is entitled to discuss the pros and cons of different systems in this thread and the legality issue is one of many aspects that deserve some discussion. *****

Thanks

Peter

*** house keeping

Edited 20/04/04 03:57 AM by BLKXRT

[TURBO4LT]

Seems to be attracting the crowds :D

[Cobra]

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this thread is way of track but interesting

17 people reading at one time must nearly be a record lol. Its very interesting.

Geea.

I hope that the interest is not all due to the potential scrap that was about to take place ..... the moderating team are not going to allow the tone to drop in any thread ....

even it is way off track and interesting