I haven't got my calculator at the moment, but if you hook on to the thread
http://fordsix.com/forum/viewtopic.php?t=1708&start=0&postdays=0&postorder=asc&highlight=
I stated on the Hardcore session, you'll see a way to calculate it. It'll maybe confuse you, but its got all the answers there. Another goodie, and better if you are into mph, feet, pounds and inches is Bruce Bowlings on the Tech forum (just click on the in-line moniker), or click on this
http://www.bgsoflex.com/aero.html
The really good thing about all this crap is you can find out absolutely how much horspower or killer Wots you need to get the top speed required. So if someone says there Falcon Phase III does 140 mph ( 225 KM/H) you can tell him he needs 250 kw or you can tell him that the Phase IV couldn't have done 170 mph(274 km/h) on a flat as a stocker unless it had 300 kW. And you can prove it beyond reasonable doubt!
It's the best BullSh*t detector around!!!!
Oh dear, I found my calculator....There are two answers for manual and auto (A & B).
A.SOME GROUND RULES FOR MANUAL XF EFI 5-SPD:-
Doing the math
1.the weight of the car has no bearing on the maximum top speed unless the road isn't long enough.
2.The stock XF readlined at 4500 rpm, but could cope with more. It's just that theres less than 90 kw at 4500 rpm. The maximum power was about 121-122 kW at about 4000 rpm, so maximum speed can only occur at max power generally.
3.Gearing of the car must allow the thing to hit 4000 rpm at the speed at which maximum flywheel power equals kW's of tyre loss, drive train loss, and drag and frontal area loss. An auto and diff losses almost 33% of flywheel power verses rear wheel power. A T5 manual is more like 28% loss.
Often top speed happens in 4 th on a brick like XF with poor areodynamics, not 5th. I've not seen the data on the 188 km/h reported, but I'd say it would be in 5th because 3.23:1 gears give only about 36.4 km/h per 1000 rpm, and at 4000rpm, that's only 164 km/h. I don't know what the top end overdrive is for the EFI T5, BUT IF ITS 0.79:1, then that's 46.1km/h. This gives 184 km/h at 4000 rpm.
(Doing the power calcs from the Tech section
http://www.bgsoflex.com/aero.html has Bowlings formulae for drag and horsepower calculations gives you an answer, but it's based on Imperial measure for hp loss and frontal area in feet. It's just easier to use metrics, in my opinion).
4. The calcs for finding out how much power 188 km/h, the speed claimed, are as follows:-
How much power does he need? Well, drag factor (cd) is 0.48, and front area is about 2.25 m
2
(188*188*188*0.48*2.25) all divided by 76716. That gives 93 kW at the road wheels needed.
Then do an etimate on a 205 mm wide tire on a 1480 kg car at 188 km/h. Take that Honda CRX's 6kW at 240 km/h, and mutiply it by 1480/900...this gives 9.9 kW rolling resistance. Then mutiply the 9.9KW by the % increase in section width. Thats about 10.4kW. Then work out the reduction in speed from the 240 km/h CRX, and divide by the factor. That gives 8.1 km/h
93kW+8.1kW=101 kW needed on an engine dyno...135 horsepower.
Then the drive train loss is around 1.28 for a T5. That's a need for over 174 hp net at the flywheel. That's 129 Kw at 4100 rpm with a 46.1 km/h per 1000 rpm top.
Sum-up is that 188 km/h might just be possible for a 5-spd stocker!.
B.SOME GROUND RULES FOR AN AUTO XF EFI:-
Doing the math
1.the weight of the car has no bearing on the maximum top speed unless the road isn't long enough.
2.The stock XF readlined at 4500 rpm, but could cope with more. It's just that theres less than 90 kw at 4500 rpm. The maximum power was about 121-122 kW at about 4000 rpm, so maximum speed can only occur at max power generally. A BW 40 auto and diff looses almost 33% of flywheel power verses rear wheel power.
3.Gearing of the car must allow the thing to hit 4000 rpm at the speed at which maximum flywheel power equals kW's of tyre loss, drive train loss, and drag and frontal area loss.
Often top speed happens in 4 th on a brick like XF with poor areodynamics, not 5th. With a 2.53:1 diff (thats what it was, I think) that's a top gearing of 46.5 km/h, maybe less than that because of slight torque convertor slip. This gives 188 km/h at 4000 rpm.
4. The calcs for finding out how much power 188 km/h, the speed claimed, are as follows:-
How much power does he need? Well, drag factor (cd) is 0.48, and front area is about 2.25 m
2
(188*188*188*0.48*2.25) all divided by 76716. That gives 93 kW at the road wheels needed.
Then do an etimate on a 205 mm wide tire on a 1480 kg car at 188 km/h. Take that Honda CRX's 6kW at 240 km/h, and mutiply it by 1480/900...this gives 9.9 kW rolling resistance. Then mutiply the 9.9KW by the % increase in section width. Thats about 10.4kW. Then work out the reduction in speed from the 240 km/h CRX, and divide by the factor. That gives 8.1 km/h
93kW+8.1kW=101 kW needed on an engine dyno...135 horsepower.
Then the drive train loss is around 1.33 for a BW 40. That's a need for over 180 hp net at the flywheel. That's 134 Kw at 4050 rpm with a 46.4 km/h per 1000 rpm top.
Sum-up is that 188 km/h isn't possible with a stock BW 40 XF EFI.
Actual speed with an auto would be about 184km/h, and that would need about 120 kW to do it.
Whew, now we can all get some sleep!.
