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        General >> Give/Need advice to/from others >> mph at 1000 rpm
        
(Message started by: 5stud on May 11^th, 2010, 11:00am)

Title: mph at 1000 rpm
Post by 5stud on May 11^th, 2010, 11:00am

is thear a list of mph at 1000 rpm in top gear fore diferent models ??

Title: Re: mph at 1000 rpm
Post by Highlander on May 11^th, 2010, 11:41am

I've never seen anything for that rpm.

We've had the rpm figure for various models quoted but usually for 70mph (speedo reading)

I'm assuming the engine/transmission/diff combinations will all give different readings

at 1000rpm in top gear the engine would be struggling and you would be nearing stall speed so it would be hard to judge.

Redarrow said his diesel auto sits around 2400 at 70mph
24v will be 2500rpm at 70

What is it you are working out?

Title: Re: mph at 1000 rpm
Post by Tons_of_fun on May 11^th, 2010, 1:48pm

Indicated 155mph @ 5900 rpm in top :-) :-) :-).....On private land of course ;-)

Title: Re: mph at 1000 rpm
Post by PJDavis on May 11^th, 2010, 8:32pm

There are certain fairly accurate measurements you need to work out to a fairly close degree what speed your car is doing per 1000 rpm.

The rear wheel rolling radius, differential ratio, and final gearbox ratio.

The rolling Radius would be about 11.5 inches with a 225 tyre. Diff ratio for the 2.3 is 4.27, and the 2.9 3.64. The ratios for the 4LDE gearbox are, 1st=2.47 2nd=1.47 3rd=1.00 4th (o/d) = 0.75.

The engine at 1000 rpm = 60,000 revs per hour. Because of a differential of 4.27 the wheel would do 14,051 revs per hour at a speed of 1000rpm.

The circumference of the wheel = rolling radius x 2 x Pi. Which = 11.5 x 2 x (22/7) = 72.28 inches. (This 72.28 = one wheel revolution) = 2.008 yards. 1760 yards in a mile, divided by 2.008, = 876.49 revolutions of that wheel in a mile.

14,051 revolutions of rear wheel per hour, divided by 876.49 revolutions per mile of the rear wheel, = 16.03.

So, at 1 to 1 ratio the 2.3 does 16.03mph per 1000rpm. However, top gear ratio is 0.75, so that puts it at 21.373 (recurring) mph per 1000rpm, so at 6000 rpm the 2.3 is doing a true speed of just over 128mph.

You can swap the figures for the 2.9. It is 18.8mph per 1000rpm, then also has the reduction through top gear ratio of 0.75, = 25.06, so 25.06 x 5900rpm = 148 ish mph.

You can also work out the speed in each gear by using the ratios against 1 to 1. So, because first is 2.47 ratio, that would be (for the 2.3) 16.03 divided by 2.47 = 6.49. Then multiply the 6.49 by the engine speed. So if you change up at 6200rpm, that would = about 40mph in 1st gear at 6200rpm.

Of course all the speeds above are very approximate, and probably quite wrong, but the formula is rock solid.

Title: Re: mph at 1000 rpm
Post by tonyboy on May 11^th, 2010, 9:05pm

http://www.fordscorpio.co.uk/YaBBImages/iagree.gif ...... ??? ... ;D

Title: Re: mph at 1000 rpm
Post by Highlander on May 11^th, 2010, 10:58pm

2.3 has a 3.91 diff ;)

Title: Re: mph at 1000 rpm
Post by PJDavis on May 11^th, 2010, 11:45pm

Is it the 2.0 ltr that has the 4.27 diff then?

Title: Re: mph at 1000 rpm
Post by PJDavis on May 11^th, 2010, 11:55pm

Aye Highlander, I must have read the diff ratios wrong, the 3.91 seems more realistic with revs at around 6000rpm the change up true speeds for 2.3 would be about,,, 1st to 2nd 42mph,,, 2nd to 3rd 72mph,,,3rd to 4th 105mph.

Title: Re: mph at 1000 rpm
Post by 5stud on May 12^th, 2010, 9:15am

just trying to workout the speed-rph on a 2lt man.old fords wear quoted mph at 1000 rpm.the mk1 granada is 21 mph at 1000 rpm so low by to days standerds.the mk3 24v is 29 mph at 1000 rpm

Title: Re: mph at 1000 rpm
Post by Highlander on May 12^th, 2010, 9:58am

on 05/11/10 at 23:45:10, PJDavis wrote:

Is it the 2.0 ltr that has the 4.27 diff then?

2.0 16v is 4.27
2.0 8v is 4.09
2.3 16v is 3.91
2.9 12v is 3.64
2.9 24v is 3.64
2.5 TD is 3.36

some of the Ford literature incorrectly shows the wrong diff ratios

Title: Re: mph at 1000 rpm
Post by Mike H on May 12^th, 2010, 2:53pm

i think I know what he means, like the old BL cars might be quoted as so many r.p.m. per 10 m.p.h.

You couldn't drive it at 10 m.p.h. in top, but that's not the point, just means you'd be able to work out r.p.m. from an actual road speed and vice versa. Like, for instance 500 r.p.m. @ 10 m.p.h. means 5,000 @ 100 m.p.h.

Might be able to work it out from technical data in the handbook, there's tables for max. power also for speeds in what gears, presumably the max. speed in each gear equates to max. power output (?)

Title: Re: mph at 1000 rpm
Post by tonyboy on May 12^th, 2010, 6:00pm

Does this Help (http://www.csgnetwork.com/rearendgearcalc.html)

Title: Re: mph at 1000 rpm
Post by faffi on May 17^th, 2010, 10:07pm

Slightly off-topic, but... My 2.9 12-valve didn't appear to have the same gearbox as the others with automatic transmissions. It didn't have a sport, economy or winter setting, for instance. Does anybody know if it had the same ratios as the other autos?

My 2.3 seemed to give about 23 mph / 1000 rpm in top, this with a manual gearbox, although I haven't done any calculations.