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Old 08-03-2004, 05:39   #1 (permalink)
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What is the best way to judge how fast a car will go?

What is the best way to see how quick a car will go down the 1/4? Or what is the best way to judge how quick a car will go in general?

Is it the rwkw output?

Is it the torque output?

Is it the power to weight ratio?

Is it something else?

Is it a combination of the aforementioned factors?

Thanks
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Old 08-03-2004, 05:41   #2 (permalink)
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Re: What is the best way to judge how fast a car will go?

There are calculators based on weight and rwkw but most of them are basically well off reality. Only real way is to actually do it or get a gtech to give you a close estimation.
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Old 08-03-2004, 05:43   #3 (permalink)
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Re: What is the best way to judge how fast a car will go?

to calculate a car's estimated quarter mile time you will need its rwkw and its weight. theres a few calculators around that will do this for you.
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Old 08-03-2004, 05:50   #4 (permalink)
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Re: What is the best way to judge how fast a car will go?

I was under the impression that torque was pretty important too, in figuring out 1/4 times.
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Old 08-03-2004, 05:53   #5 (permalink)
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Re: What is the best way to judge how fast a car will go?

rwkW calculators are the most poorly thought out, inefficient calculators possible. Go to google and search for Virtual Engine Calculator. It's a program I use for calculating cubic inches from bore x stroke numbers, and calculating your ET from power. Enter your crankshaft power, in Horsepower, so if you own a stock 260kW BA XR8, you input 348 for 348hp... and your weight in pounds, so for the stock XR8, 3949lbs (1795kg). It gives you your ET @ mph for 1/4 and 1/8 mile.

Keep in mind, this does not take gear ratios, weather conditions, traction etc into account, but I have found it pretty accurate. For a stock XR8 is says 13.76 @ 97.9mph. Lots of people in stock BA XR8's on this forum have run 13.8s @ 100mph.

ANY calculator based on power output in the wheels should be thrown away and poked fun at. It is by far the MOST inefficient and stupid way to calculate one's ET. Every 2 minutes your rwkW is different. Dyno the exact same car, on the exact same dyno, say 10 minutes apart, and you will get a different reading each time. Chassis dynos can never be accurate, ever, unless the power went direct to the wheels, no tranny and s*** in the way to sap any of it.
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Old 08-03-2004, 06:02   #6 (permalink)
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Re: What is the best way to judge how fast a car will go?

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Originally Posted by Steffo
Dyno the exact same car, on the exact same dyno, say 10 minutes apart, and you will get a different reading each time.
sure will. but by how much? 5kw? for a rough ET(which is all we're looking for) rwkw is accurate enough.
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Old 08-03-2004, 06:08   #7 (permalink)
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Re: What is the best way to judge how fast a car will go?

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Originally Posted by barry_v
sure will. but by how much? 5kw? for a rough ET(which is all we're looking for) rwkw is accurate enough.
rwkW will never be accurate enough ever. That's a lacksture attitude in my books, if its not as perfect as possible, it's not good enough I say. Plus why bother when there are BETTER calcs then that in existence, which do it from crank rated power? Virtual Engine Calculator does alot more then ET from Power. I'll have to buy the full copy, though the free demo version can do alot of stuff too.
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Old 08-03-2004, 06:13   #8 (permalink)
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Re: What is the best way to judge how fast a car will go?

rwkw is really the only way to do it. 2 cars, exact same engine HP, 1 an auto and 1 a manual. You will get significantly different real world times. I have many of these calculators (including virtual engine calculator) and none of them are even close. Some over estimate time others under estimate time.
I know my car is 3600lb, I also know it can run a 15.94 @ 88mph. I also know the rwkw figure (or at least a reasonable estimation) and none of the calculators even get close.
Oddly enough, virtual engine calculator gets the right mph based on 3600lb and 230hp (172fwkw stock for the VCT) but a time of 15.32ET. Hell, I wish!!! I dont know of any legit stock VCT's that run a 15.3!
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Old 08-03-2004, 06:16   #9 (permalink)
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Re: What is the best way to judge how fast a car will go?

Quote:
Originally Posted by Casper
rwkw is really the only way to do it. 2 cars, exact same engine HP, 1 an auto and 1 a manual. You will get significantly different real world times. I have many of these calculators (including virtual engine calculator) and none of them are even close. Some over estimate time others under estimate time.
I know my car is 3600lb, I also know it can run a 15.94 @ 88mph. I also know the rwkw figure (or at least a reasonable estimation) and none of the calculators even get close.
Oddly enough, virtual engine calculator gets the right mph based on 3600lb and 230hp (172fwkw stock for the VCT) but a time of 15.32ET. Hell, I wish!!! I dont know of any legit stock VCT's that run a 15.3!
I saw a bone-stock AU1 XR6-VCT run a 15.0 at Eastern Creek back in 2000. Was probably a freak car though, but 15 flat nonetheless.
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Old 08-03-2004, 06:18   #10 (permalink)
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Re: What is the best way to judge how fast a car will go?

No calculator can possibly be 100% accurate. But I've found, looking at real world times (ie: 13.8s in XR8 etc) that Virtual Engine Calc is extremley good. Other people may have found it different, but whatever. The BEST way to find out how fast your car is.. is definitley to go out to the track and race the bloody thing!
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