Fastest 1/4 time?

[InsanityInc]

Oh, also. I posted in that thread about buying one, but it seems to have kind of disappeared from the forums. So, is there somewhere I can email you at or something? This forum doesn't seem to have a private messaging system, or i'd just use that.

[Nismo_Freak]

3" exhaust on a n/a KA is ignorant. Sure your peak hp increases, but look at the torque curve down low. That same car that supposedly pulled 13+ hp out of a 3' catback would run .2-.4 SLOWER in the 1/4. So dyno numbers become meaningless.

I'm gonna have to disagree with this.

Horsepower is a measure of work. Work is what actually moves the car, since it by definition is the amount of mass moved x amount of distance per unit time. Granted in order to achieve work you must have a force, torque. The more torque you have the more work at that give amount of time, true. However, when you include engine rpm into the mix then the amount of work moves up as the RPM's increase even though the torque value can remains the same. What you get is faster acceleration even though amount of torque is exactly the same. The same goes for when you gain a minute amount of torque at a high rpm, the amount of work gained is higher than if you had gained the same amount of torque at a much lower rpm. It is because of that principle that torque plays only a role in actual vehicular acceleration, it is not the end all to movement.

HP = Tq *RPM / 5252

Lets say at 2000 RPM the 3" Exhaust 240 makes 5 lb. ft. less torque @ 140 lb. ft.

X = 140 x 2000 / 5252X = 53.3 HP

By comparison - the stock 240

X = 145 x 2000 / 5252X = 55.2 HP

Delta X = 1.9 HP

Now lets say at 6000 RPMs the 3" Exhaust car makes 5 lb. ft more torque @ 130 lb. ft.

X = 130 x 6000 / 5252X = 148.5 HP

In comparison the stock 240

X = 125 x 6000 / 5252X = 142.8 HP

Delta X = 5.7 HP

Now some calculations:

1 HP = 1000 lbs. X 33 ft.

or

1 HP = 3000 lbs X 11 ft. (3000 lbs. = weight of 240 w/ driver)

now

5.7 HP = 3000 lbs. x 62.7 ft.

Meaning 5.7 HP can move a 3000 lbs. object 62.7 ft. in one minute.

1.9 HP = 3000 lbs. x 20.9 ft.

Meaning 1.9 HP can move a 3000 lbs. object 20.9 ft. in one minute.

Translated into movement differences.

53.3 hp = 3000 lbs. x 586.3 ft. 55.2 hp = 3000 lbs. x 607.2 ft.

Delta ft. = 20.9 ... notice the above value the 1.9 HP formula

148.5 hp = 3000 x 1633.5 ft.142.8 hp = 3000 x 1570.8 ft.

Delta ft. = 62.7 ... notice the above value in the 5.7 HP formula

While at the lower RPM the stock 240 may gain a small advantage the other 240 will overtake that advantage and proceed to put 2/3rds. more space between the two.

There you have it... the higher the RPM value the more crucial the torque value becomes. So the focus on making a vehicle accelerate should be in the production of high end torque which is easier translated into the production of horsepower.

However, a common misconception is area under the curve means a faster car. Untrue by the math above. You want to move as much area as possible into the USEABLE RPM range for maximum acceleration. When you upshift a 240 you drop down to around 4000 rpms or so, so what good is producing power below 4000 rpms other than daily drivability? It doesn't make you faster to produce 50 ft. lbs. more torque at 2000 rpms when you are never at 2000 rpms in the course of a 1/4 mile.

[:: orion ::]

However, a common misconception is area under the curve means a faster car. Untrue by the math above...

No, that's true by the math above.

If you increase the TQ by 5ft/lbs up 6000rpm, it adds more area than if it's added at 2500rpm...this holds true especially if there is no low end loss, which is the case with a 3" exhaust on an N/A KA...see below:

- - - - -



Purple line on the yellow-background graph versus blue line on the white-background graph...only change was an N1 exhaust on the same '97 240SX with a KA.

The TQ is higher across the board, with a peak increase of 10rwhp and 10rwtq...but a max gain of 16rwhp!

Not exactly typical gains (usually not as high), but it's a typical curve...low end barely changes, and if it does it's for the best...and the top end is substantially increased.

- Brian

[AZhitman]

Oh, also. I posted in that thread about buying one, but it seems to have kind of disappeared from the forums. So, is there somewhere I can email you at or something? This forum doesn't seem to have a private messaging system, or i'd just use that.

No problem - You can always reach me at [email protected]!

[UncleBen]

If you want a car to go fast in the 1/4 mile, please, by all means SELL THE 240 and buy a civic, because they can go fast for cheap in the quarter.

The 240 has never been a straight line car, and it never will be IMO. There are a few insane ones out there that can go very fast in the 1/4, but thats because they have v8's and/or major major major work done.

[Nismo_Freak]

No, that's true by the math above.

If you increase the TQ by 5ft/lbs up 6000rpm, it adds more area than if it's added at 2500rpm...this holds true especially if there is no low end loss, which is the case with a 3" exhaust on an N/A KA...see below:

Purple line on the yellow-background graph versus blue line on the white-background graph...only change was an N1 exhaust on the same '97 240SX with a KA.

The TQ is higher across the board, with a peak increase of 10rwhp and 10rwtq...but a max gain of 16rwhp!

Not exactly typical gains (usually not as high), but it's a typical curve...low end barely changes, and if it does it's for the best...and the top end is substantially increased.

- Brian

Actually I was refering to the torque curve, which makes my statement true, however if I was refering to the horsepower curve then yes, you would be correct.

[WDRacing]

Wow...What a waste of bandwidth...I'll double Gregs $100 for anyone who runs 14.99 with a street legal 240 with the only mods being I/H/E. This includes weight reduction as well. I could run 13's with a sawzall listed in my mod list, so lets be serious.

[InsanityInc]

A civic? You're seriously recommending a civic for drag racing. I don't even know how to respond to that.

The only fast civics also have massive, massive work done to them, have a huge turbo, a different engine etc.

[BadMojo]

I would have said Fox Body Mustang or even a DSM, but whatever. I can't even remember what the hell this thread is about.

The aftermarket for the Civic is, of course, HUGE compared to our cars. More kick *** parts available and they're cheaper, due to economy of scale, I suppose.

Anyway...what the hell are we bickering about anyway?

[AZhitman]

LOL

Brian, you gotta come up soon (or I'll roll to the Pueblo) - I want an expert to check out my 'vert (and tell me if it's as slow as all other S13's).

[WDRacing]

I was gonna come up last weekend...should have cause I would have saved some cash. That friggin drive kills me though. I hate 2 hour drives through the desert, especially when GAY AZ has a felony speeding law of 80mph.

I'm pretty sure I have Alert again this weekend, I'm so sick of this job.

[InsanityInc]

AHA! I found it!

http://forums.freshalloy.com/u...&vc=1

3" N/A KA dyno.