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Acceleration ALWAYS includes the element of time. It's m/s^2 after all. You are still talking about torque, but trying to glean some extra information from the power curve, which I'd warn is not always accurate. I'm really not sure what else to tell you but take a look at the text that I cited above. It's only concerned with "autodom". The equations used to calculate acceleration (very accurately, I might add) don't have power in them. |
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Nobody! In the end: we will shift where we want to shift. I love engineers, and theory, but I live in a real world. What is on paper doesnt always work. Some of us call it "seat of the pants". I call it "calibrated ass" Old school: "Bubba" shift the truck just after the valves float!! B |
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This last post is correct. You want peak power.
... because the torque multiplication effect of the gearbox works in your favor, since you get the torqgue multiplied by a ahigher number of revolutions equal to the ratio of the two gears).
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Huh?
Sorry guys but WTF are you talking about? Are you saying the harder I press the accellerator the faster my car goes?
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It's a good idea to cite your references for information. |
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Interesting, but this wasn't my source. This must have been posted on numerous sites, because I have seen it before... Happy Motoring!... Jim'99 |
My point is:
Keep talking it about and applying science. I'm going to go and actually do it. It's cool. I know where you are coming from :cheers: I also fully understand the theory. I spend a lot of time applying the theory to AutoX and road racing where I need torque. I dont really give a sh_t about it on the street where 90% of these people drive their Boxsters. Case in point (I have done this in the past multiple times) We both line up side by side in the same cars on the same tires. You apply torque theory to the drag race about to occur between us. I beat you from experience, not theory. Everything works on paper. My engines make the most power in the computer simulation software I use!! B |
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Copy and paste?
B |
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I most likely found this some time ago, thought it contained several good points and I copied it as a Word document to the pretty large database on Car Stuff that I maintain. Much of my reply was Cut & Paste from this, and other sources, it's much more efficient than transcribing it for this Forum. This is why I didn't quote a source, because I don't remember where I got it, the source is lost to me. I am certain it wasn't from a Corvette site, because I never visit them. But, that doesn't make it any less true. None of the respondents to this and other technical threads invented any of this stuff, we're merely passing on the information we have available. I am an author by trade (have done a lot of Ghost Writing and technical editing for several publishers, including Motorbooks Int'l.) and pay particular attention to quoting sources and giving footnote credits and have often done so here. I must regularly review my work to insure that no plagerism has occured and I am experienced in doing so. But, I don't give a foornote credit to the guy who invented the word The. And, I'm sure that you realize that pretty verbatim is not verbatim. I don't see a foul if that's what blue2000s is trying to imply... Happy Motoring!... Jim'99 |
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My point is that I can't have a conversation with an internet article and if that's the dimension of this converse, it's dissapointing and pretty much pointless. |
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Example: you have 2 identical cars w/ different torque curves. both cars are currently making 300 ft-lb of torque. Car A: Torque = 300 ft-lb, RPM = 8000, HP = 457 Car B: Torque = 300 ft-lb, RPM = 4000, HP = 228 now, as you stated earlier, because these cars are making equal torque, they are accelerating at equal rates. BUT, assuming 1:1 final drive: car A is doing this from 91 mph while car B is doing this from 45 mph. even though they are gaining speed at the same rates, car A is travelling MUCH faster because it is performing WORK at twice the rate (double the POWER). it is a common misconception that shifting just above peak torque will yield fastest acceleration times. gearing allows us to take advantage of power, though, and the object is to do the WORK (i.e. move 3000 lb of car 1/4 mile) as quickly as possible. work / time = power. |
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I wouldn't argue against that at all. but the acceleration of the vehicle still comes from torque doesn't it? That's all I've been saying. What you are saying is that there is an advantage to acceleration in extended speed, this is certainly true, but this is still due to the conversion of that speed to torque at the wheels through gearing. It all comes back to torque. READ THE BOOK! |
You guys can do all the math and internet jibba jabba you want, but the fact of the matter is you always shift at the highest RPM you possibly can, no matter what your torque curve looks like.
The engine accelerates faster at it's highest RPM regardless of HP. Your car will accelerate faster if you shift at redline even if your power is down lower. Talk about physics and engineering all you want. When the lights drop the BS stops, and if you don't shift at redline your in second place. PERIOD. Here is the dyno plot from my Dad's Maxima that he drag races. It has a VQ35DE in it (350Z motor) and makes a maximum of 259whp and 239ft/lbs of torque normally aspirated at the wheels (this isn't the max dyno plot just one of them I snapped. The car has cams and torque convert and headers etc few trick and stuff. Look at the HP and torque curve. That says you should shift at 6200rpm. When he does that the car runs 13.3 @ 100mph or worse. When he shifts at 7200rpm as indicated on the dyno, the car is faster, best now 12.8 @ 106mph. Almost a half a second and in terms of racing thats a long time. Acctually this dyno before I tuned the car (emanage ultimate) made 236whp and 219ft/lbs of torque. We picked up 21hp peak with my tuning. Between 6000-7000 power was dropping below 180whp and with timing and air fuel tuning I bumped it to what you see there. I made 60whp extra between 6000-7000rpm over stock with my tuning tricks on his car. It should run a 12.4-12.5 now I would think with 60whp extra in the top rpm range. |
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