What does "drag limited" mean?

10665 Views 11 Replies 7 Participants Last post by sjt, Feb 9, 2002

Jonathan_Yi

Discussion Starter · Feb 8, 2002

Like it says, what does that mean? Couple of days ago I saw somewhere that said our cars were drag limited to something like 125mph, and I think I recall that it said the same thing for the STI, so I figured it meant that it couldn't go faster than 125mph due to aerodynamics and such, but it doesn't sound right as doing a little search revealed that many people claimed to go well over 130mph.

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· #2 · Feb 8, 2002

Drag limited means that's as fast as you're going to get with the supplied amount of power. The STi has a bunch more power than the RS, so it'll go faster.

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STiShawn

· #3 · Feb 8, 2002

Drag limited means that the cars aerodynamics will not allow it to travel anyfaster...

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sjt

· #4 · Feb 8, 2002

drag limit = hp vs. drag coefficient.

the greater the hp, or the lower the drag coefficient then the higher your top speed and the converse of the statement is true as well.

Hood scoops are damn cool but don't help much in the aerodynamics dept.

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trojan9x

· #5 · Feb 8, 2002

i've gotten my car over 130 before i'm sure (whatever straight down is)

so i'm probably guessing that they mean maybe in an actual 1/4 mile race that you will probably never get it over 125 mph. but i am probably wrong.

:run:

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Mike M

· #6 · Feb 8, 2002

trojan9x said:
i've gotten my car over 130 before i'm sure (whatever straight down is)

Well, you've seen an indicated 130, but I doubt you were acutally there. Most cars speedometers are optimistic, and they seem to get more so as your speed increases. Had you been dinged by a radar gun at that point, I think you would have seen a somewhat lower number.

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trojan9x

· #7 · Feb 8, 2002

well, i wasn't at redline yet and the car wasn't slowing down at all, i just didn't want to get caught going that fast so i slowed down.

and i do feel that the speedometer is pretty accurate because when i went drag racing at ATCO i checked my speed as i was finishing and it was fairly accurate to my time slip.
my G-Tech was also fairly close to my speedo time.

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Mike M

· #8 · Feb 8, 2002

That's cool. I certainly wasn't trying to call you a liar or anything, just going on previous knowledge with other cars.

But, considering the horsepower our cars turn out, and their rather "brick-like" aerodynamics, 125 sounds like a pretty reasonable number to me...

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HondaH8er

· #9 · Feb 9, 2002

I know that my speedometer is a bit on the opptimistic side, as I drove by one of those photo-radar things on the side of the road, the kind that shows your speed, and when it said I was going 30 mph, my speedometer showed about 32-33 mph. And when considering that the RS is about as aerodynamic as a snowplow, 125 mph with stock power sounds about right to me.

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subachad

· #10 · Feb 9, 2002

Hi guys, here's a quote from my site.

Wondering how much power it will take to get your car up to 200 MPH? Here's an equation to help you find out. (this information is from August 2001 Sport Compact Car)

Aero Horsepower: Drag x Speed or HP at the wheels

Frontal Area: Amount of Frontal Area (large hood scoops, mirrors and bumper openings add to this and decrease your top speed.

Cd: Coefficient Drag.

Speed: In MPH

Aero Horsepower = 0.000007 x Frontal Area x Cd x Speed3

Here is a Chart from Sport Compact Car

Car Frontal Area Cd HP Needed at 100 mph HP Needed at 125 mph HP Needed at 150 mph

2000 Subaru Impreza 2.5RS 22 0.35 54 105 182
1998 Ford Mustang GT 22.5 0.34 54 105 181
1996 Honda Civic DX Hatchback 20.5 0.32 46 90 155
2001 Volkswagen Golf GL 20.5 0.31 44 87 150
1997 Acura NSX 19.2 0.32 43 84 145
2000 Honda Insight 20.4 .25 36 70 120

The .000007 number will change depending on temperature. The hotter it is, the lower the number.

The L has a CD of .32 due to the lack of spoiler, scoop, and really nice bumper.

Chad
93 1.8T

P.S. cars traveling at 200+ MPH (radared at 229) are VERY fast when you see it on an open highway.

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· #11 · Feb 9, 2002

Wind makes a huge difference. That's why most speed records must be run both ways, just in case you had the wind pushing you one way. With a tailwind it would be pretty easy to squeaze out an extra couple mph. The 125mph was an estimate. I've heard a lot of people say 127ish, so 130 isn't that far above. Who knows.. maybe you got a really hot motor. There's enough margin in each car to make one faster than another.

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sjt

· #12 · Feb 9, 2002

oh and going downhill REALLY helps too!!!:biggest:

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