[Rap]

Stop being so sensitive thong man. The kids reaction times were faster not yours were slower. Da! Lol buy the Motorsport fitness Manuel. It's for guys our age looking to keep up! At least I think it is if I can remember what I read.

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[bombfactory]

Re-match! We gotta know for sure!

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[MB968]

[quote name='ds968' timestamp='1349209856' post='133288']



btw, I just spoke to him, he was in 3rd gear and I was in 4th , though I sense even if we were both in 3rd, and I had the AC off, yada, yada .. the 964 is still quicker by virtue of its torque sustainability ..

[/quote]



Just because you're both in 3ed doesn't tell you enough. The force between the tire and the road which goes into the F=ma equation to see who accelerates the fastest comes from several factors. You start with the engine torque, multiply it by the 3ed gear ratio, then multiply it by the final drive ratio and then divide it by the radius of the wheel (in feet if you are using ft-# for the torque values). If you know the weights of each car as tested, divide the above calcs by the weight of the car which will result in two numbers, one for each car, which is proportional to the acceleration of the car. If his ratios don't mutiply out as big, or if his tire OD is much larger, or the weight much different, you might still show pretty well. Of course, as you said, since his torque sustains it's high value longer into the upper rpm range, you may initially pull ahead only to have him overtake you.



Someone who knows these ratios should do the math just to see how much of a shot you have at least at the initial "start". If you want to get a little more accurate, since you are both starting at the same speed, say 40 mph, you need to get the torque value for each engine at the rpm corresponding to the "start" mph.



And, yes the equation should include the effort it takes to accel the rotatinal inertia of the engine/drivetrain. These aren't so easily known, thus calculated/compared.



The math gets a lot more difficult if you want to run a simulation of the whole race. I know there are some other engineers out there who might remember this better, but if memory serves, you'd have to take the integral over time having each torque value for that instant in time for where the engine is in its rpm range.

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[flash]

there are some pretty cool programs out there nowadays that will do this for you

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[ds968]

[quote name='MB968' timestamp='1349222919' post='133298']

Just because you're both in 3ed doesn't tell you enough. The force between the tire and the road which goes into the F=ma equation to see who accelerates the fastest comes from several factors. You start with the engine torque, multiply it by the 3ed gear ratio, then multiply it by the final drive ratio and then divide it by the radius of the wheel (in feet if you are using ft-# for the torque values). If you know the weights of each car as tested, divide the above calcs by the weight of the car which will result in two numbers, one for each car, which is proportional to the acceleration of the car. If his ratios don't mutiply out as big, or if his tire OD is much larger, or the weight much different, you might still show pretty well. Of course, as you said, since his torque sustains it's high value longer into the upper rpm range, you may initially pull ahead only to have him overtake you.



Someone who knows these ratios should do the math just to see how much of a shot you have at least at the initial "start". If you want to get a little more accurate, since you are both starting at the same speed, say 40 mph, you need to get the torque value for each engine at the rpm corresponding to the "start" mph.



And, yes the equation should include the effort it takes to accel the rotatinal inertia of the engine/drivetrain. These aren't so easily known, thus calculated/compared.



The math gets a lot more difficult if you want to run a simulation of the whole race. I know there are some other engineers out there who might remember this better, but if memory serves, you'd have to take the integral over time having each torque value for that instant in time for where the engine is in its rpm range.

[/quote]



   





geez guys, I' have no interest in turning this into a contest since there is no purpose to it.. I just wanted to find out why two seemingly equal stats cars were so different in acceleration.. and now I know more that I ever wanted to learn, LOL..

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[MB968]

Sorry, I've been known to geek out once in a while, you can just ignore me, I won't take it personally. Pretty used to it; combine innate curiosity with a need to solve problems a basic understanding of physics, and you have a recipe for disaster. Especially since I've been retired for some time and don't get to play high tech any more.

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[tamathumper]

Help me design a small sound studio for the new house. That'll keep you occupied! <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" />

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[flash]

lol - been there done that. quite a few of the artists i have worked with have home studios. i used to do quite a few of them. it's a lot harder to do something in an existing structure, especially if the ceilings are only 8'. it's all about how much of the sound you want contained in the room. tuning the inside is easy. stopping it from pissing off the neighbors or the wife is a whole different story.



but now we're WAY off topic



i have a couple of programs for figuring out what a car will do. there is a ton of stuff to plug in to get real data, but it's pretty cool. i even have one of them that lets you "race" cars around various tracks around the world. it's not interactive (you can't change anything on the fly - it's not a video game), but it's cool for seeing what different things will do in lap times.

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[Rap]

DS is that a pic of you when you were younger? Lol

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[ds968]

[quote name='Rap' timestamp='1349259306' post='133311']DS is that a pic of you when you were younger? Lol[/quote]



Ha, ha..



@MB - I was just kidding of course and actually as technically-challenged as I am most of the read was clear enough to make sense even to me, lol.. just funny to see the level of detail we' re covering here ; flash' algorithms and similar models included.. :-) :-)

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