cosrep

Can any present or previous XR4x4 owners tell me what rpm the car will cruise at 70mph in 5th at please?

tabetha

Need certain info to get 100% accurate, such as top gear ratio, ie 0.83:1, if it is N3 type box still ?, tyre size used if different etc, diff ratio I would assume is the std 3.62:1.
Assuming it has the std ford listed 195/60X14, plus std diff/box it is 22.45mph/1000rpm(5th), so easy to work out from there.
tabetha

cosrep

Thanks for the info, Yes looking for what the factory rpm would be, MT75 box which has a 0.83 5th as far as I can remember and both diffs are 3.62. So with the info here were looking at just over 3100 rpm does this sound about right to any previous/current owners?

Tabetha - you wouldn't happen to know what the mph/1000rpm(5th) for a Diesel P100 is would u?

tabetha

3100 sounds pretty right to me for my old xr4i, diesel P100, would most likely be on the 3.14:1 diff, so would be to establish engine rpm at any road speed,
60 X rpm / wheel revs(mile) X diff ratio X gearbox ratio
You can also use the formula's to work out speedo errors as well , ford traditionally use either 6 or 7 teeth drive gears.
I have no idea of the box ratio for the diesel otherwise I would have shown this.
tabetha

cosrep

The P100 Diesel uses a 4.63 ratio rear diff and a type 9 box with a 0.83 5th and runs on 195/14 "transit tyres"

tabetha

What profile are the tyres, ie 195? X 14 ?
tabetha

tabetha

I am GUESSING at a 195/70 X 14, which is 630 revs per mile.
So 60 X Engine RPM = 60,000
630(wheel revs/mile) X diff ratio 4.63 X top gear 0.83
630 X 4.63 = 2916.9 X 0.83 = 2421.027

60,000/2421.027 = 24.782871 MPH/1000rpm.
Hope this is near enough for you!!
tabetha

cosrep

Thanks for the info, some van tyres dont show the profile hence why I said "transit tyres"

tabetha

If they don't show the profile, assume it to be 82% of the width then, as this is the start ratio, so I would estimate about 620 revs per mile, don't have this profile on me chart, but unmarked are 82%, I'll let you do the resum from 630 to 620.
tabetha