speed + gear = what RPM?

[s383mmber1]

Is there a chart that tells me for my car what RPM ill be at in each gear at a certain speed? I searched and couldnt find anything...

W58, 4.3 LSD with 17's

I dont think my tachometer is correct....

In second gear, at 20 MPH im at 1500 RPMS...

 

[IJ.]

Will: what size tires?

 

[s383mmber1]

245/45/17's

Im just trying to get an estimate, because im running open downpipe, and it seems like the engines working real hard at 2500 RPMs...

 

[IJ.]

1 2 3 4 5
0 0.0 0.0 0.0 0.0 0.0
200 1.1 1.9 2.8 3.6 4.6
400 2.2 3.8 5.6 7.2 9.2
600 3.3 5.7 8.4 10.8 13.8
800 4.4 7.6 11.2 14.4 18.4
1000 5.5 9.5 14.0 17.9 23.0
1200 6.5 11.4 16.8 21.5 27.6
1400 7.6 13.3 19.6 25.1 32.2
1600 8.7 15.2 22.4 28.7 36.8
1800 9.8 17.1 25.2 32.3 41.4
2000 10.9 19.0 28.0 35.9 46.0
2200 12.0 20.9 30.8 39.5 50.6
2400 13.1 22.8 33.6 43.1 55.2
2600 14.2 24.7 36.4 46.6 59.8
2800 15.3 26.6 39.2 50.2 64.4
3000 16.4 28.5 42.0 53.8 69.0
3200 17.4 30.4 44.8 57.4 73.6
3400 18.5 32.3 47.6 61.0 78.2
3600 19.6 34.2 50.5 64.6 82.8
3800 20.7 36.1 53.3 68.2 87.4
4000 21.8 38.0 56.1 71.8 92.0
4200 22.9 39.9 58.9 75.3 96.6
4400 24.0 41.8 61.7 78.9 101.2
4600 25.1 43.7 64.5 82.5 105.8
4800 26.2 45.6 67.3 86.1 110.4
5000 27.3 47.5 70.1 89.7 115.0
5200 28.4 49.4 72.9 93.3 119.6
5400 29.4 51.3 75.7 96.9 124.2
5600 30.5 53.2 78.5 100.5 128.8
5800 31.6 55.0 81.3 104.0 133.4
6000 32.7 56.9 84.1 107.6 138.0
6200 33.8 58.8 86.9 111.2 142.6
6400 34.9 60.7 89.7 114.8 147.2
6600 36.0 62.6 92.5 118.4 151.8
6800 37.1 64.5 95.3 122.0 156.4
7000 38.2 66.4 98.1 125.6 161.0

 

[s383mmber1]

My tach is way off

 

[MDCmotorsports]

Ian.. I wanna know what size rear end gear its going to take to make a 6500rpm 7m go 200mph with 18" rims....

 

[IJ.]

Jon: I'll need a tire size

3.0:1 will do it on 285/35/18s

 

[Blackfin]

Jon: I'll need a tire size

3.0:1 will do it on 285/35/18s

IJ:

You may want to check calc but I can't match that number unless I squish the tire diameter 2.5 inches or use a 3.32 rear. Either that or I have had one too many.

RPM = 6500
5th gear ratio = 0.753 (r154)
Tire diameter = 25.85 (285/35/18) (unloaded)
Rear end = 3.0
Speed = 222

 

[Blackfin]

I got same answer as hand calc using this:

http://locost7.info/gearcalc.php

 

[IJ.]

BF: I just rounded it near enough.... (213.6)

Can't get 3:1 gears for a Mk3 G series anyway.

 

[Blackfin]

Don't mind me, I am just one of those geeky engineers who like to calculate nanometer answers to irrelevant questions. :nono:

 

[IJ.]

BF: There will be considerabe centrifugal growth at 200 mph so it's all academic

 

[Poodles]

not to mention you're supposed to run higher tire pressure for high speed...

 

[Blackfin]

not to mention you're supposed to run higher tire pressure for high speed...

I thought I would start out at like 10 or 15 psi and let the pressure build.

BF: There will be considerabe centrifugal growth at 200 mph so it's all academic

Hmmm. That is something I never considered before.

 

[IJ.]

BF: We no longer speak of my manifold

 

[AJ'S 88NA]

BF: We no longer speak of my manifold

When is the funeral:cry:

 

[jonny87turbo]

Is there a chart that tells me for my car what RPM ill be at in each gear at a certain speed? I searched and couldnt find anything...

W58, 4.3 LSD with 17's

I dont think my tachometer is correct....

In second gear, at 20 MPH im at 1500 RPMS...

i checked my car in second gear, is 20 mph at 2000 rpm. 7mge, 4.30, 17in rims

 

[AGlobalThreat]

My tach is way off

at least you have a tach

 

[s383mmber1]

at least you have a tach

Ive got two, and neither work

 

[Nick M]

MPH x gear ratio x diff ratio x 336/ tire diameter = RPM.

Write it down.