XJR X308 V-max
Discussion
As the 250Km/h top speed is descibed as "limited", how fast would it go without this governor?
I have also been told but am unable to substantiate: If one drives in shifter position 4 to 6000rpm, this takes speed to marginally over 250Km/h. If 5th is then selected by moving shifter to D, it keeps going, having 'by-passed' the governor.
Short of going out to experiment, can anyone confim? I would like to know the operating protocol before stretching the legs of my car to such an extent.
Thanks
Peter
I have also been told but am unable to substantiate: If one drives in shifter position 4 to 6000rpm, this takes speed to marginally over 250Km/h. If 5th is then selected by moving shifter to D, it keeps going, having 'by-passed' the governor.
Short of going out to experiment, can anyone confim? I would like to know the operating protocol before stretching the legs of my car to such an extent.
Thanks
Peter
My old XJR had a slightly ill-fitting bootlid (which is not uncommon on the X308) and when tried out on a private road I chickened out at 145 because it felt and sounded like the bootlid was about to be ripped off.
That said, up to about 130 it felt like it would go on all day (inbetween fuel stops ofcourse).
That said, up to about 130 it felt like it would go on all day (inbetween fuel stops ofcourse).
I read many postings about knocking it from D into manual then back to D to bypass the limiter, but as far as I recall the manual gears are 4th, 3rd and 2nd. I fear knocking it into manual (4th) at top speed would cause the gearbox/diff/engine some interesting damage. Would be interested to hear any of the mechanically competent posters's thoughts..
Edited by TurricanII on Tuesday 2nd November 00:08
The auto 'box programming prevents it from selecting too low a gear for a given road speed protecting from over-rev situations. So that should not be a concern. However, I would not propose to go up to the road-speed limiter then downshift and upshift again. I would approach it with 4th selected and then at 6000rpm manually upshift.
All I would like to know is if this (or a different procedure) will by-pass the governor. Has anyone tried or has anyone access to Jaguar technical information about this?
Other cars I have driven at this sort of speed:
- E320 CDI estate (V6) 151mph. Limited to 155, but felt like it would never make it.
- C43 AMG estate. 147mph. ran out of road opportunities so never maxed out. would easily have done 155.
- E55 AMG estate. Limited to 155. Was accelerating so strongly towards it that when 155 was achieved it felt as if the brakes had been applied!! If you pay AMG a lot of money, they will re-write the ECU for 186mph (300Km/h) limit.
- Porsche 911 Carrera 4 (993 model). not limited. 165mph acheived. Seemed to take a long time to get from 155 to 165mph.
- Caterham 7. 138mph with aeroscreen - very exciting in an open cockpit!
- Jag XJ40 Sport 4.0. First car in which I exceeded 140mph (speedo reading) seemed absolutely ballistic in 1990!
In terms of sustainable acceleration still available a higher speeds, the XJR V8 supercharged is nearest in feel to the E55 (although not as strong obviously as the E55 with its 470 horsepower motor). That is why I believe it is capable of more than 155mph. I don't think it is just a matter of convenience to the marketing guys to state "limited" when the car will only just achieve that speed.
So just worndering how to get the best V-max from it. Not ready for the run yet. These things take planning and preparation on older cars. But certainly thinking in that direction. A trackday would be totally hilarious also!
Looking forward to any further info any of you may have.
Cheers
Peter
All I would like to know is if this (or a different procedure) will by-pass the governor. Has anyone tried or has anyone access to Jaguar technical information about this?
Other cars I have driven at this sort of speed:
- E320 CDI estate (V6) 151mph. Limited to 155, but felt like it would never make it.
- C43 AMG estate. 147mph. ran out of road opportunities so never maxed out. would easily have done 155.
- E55 AMG estate. Limited to 155. Was accelerating so strongly towards it that when 155 was achieved it felt as if the brakes had been applied!! If you pay AMG a lot of money, they will re-write the ECU for 186mph (300Km/h) limit.
- Porsche 911 Carrera 4 (993 model). not limited. 165mph acheived. Seemed to take a long time to get from 155 to 165mph.
- Caterham 7. 138mph with aeroscreen - very exciting in an open cockpit!
- Jag XJ40 Sport 4.0. First car in which I exceeded 140mph (speedo reading) seemed absolutely ballistic in 1990!
In terms of sustainable acceleration still available a higher speeds, the XJR V8 supercharged is nearest in feel to the E55 (although not as strong obviously as the E55 with its 470 horsepower motor). That is why I believe it is capable of more than 155mph. I don't think it is just a matter of convenience to the marketing guys to state "limited" when the car will only just achieve that speed.
So just worndering how to get the best V-max from it. Not ready for the run yet. These things take planning and preparation on older cars. But certainly thinking in that direction. A trackday would be totally hilarious also!
Looking forward to any further info any of you may have.
Cheers
Peter
According to 'the numbers' the 4 litre, 290bhp XJ8 will do 150mph.
The power required to raise the top speed increases with the cube of the speed.
An XJR has (370/290) 1.28x the power of an XJ8.
(1.28^-3) = 1.09
1.09 * 150 = 163.5mph (the same calculation using the XJ8 3.2 figures gives a top speed of 161mph)
This assumes perfect gearing for both cars, the same aerodynamics (which we know is not true, the XJR has wider tyres) the same loss through the transmission for both cars (again, unlikely as they use different gear boxes) and, of course, that the top speed for the XJ8 is accurate and not limited by gearing or whatever...as well as lots of other things but it shouldn't be hugely off, I'd be surprised if the actual top speed was outside the 160-168mph range, let me know how it goes.
The power required to raise the top speed increases with the cube of the speed.
An XJR has (370/290) 1.28x the power of an XJ8.
(1.28^-3) = 1.09
1.09 * 150 = 163.5mph (the same calculation using the XJ8 3.2 figures gives a top speed of 161mph)
This assumes perfect gearing for both cars, the same aerodynamics (which we know is not true, the XJR has wider tyres) the same loss through the transmission for both cars (again, unlikely as they use different gear boxes) and, of course, that the top speed for the XJ8 is accurate and not limited by gearing or whatever...as well as lots of other things but it shouldn't be hugely off, I'd be surprised if the actual top speed was outside the 160-168mph range, let me know how it goes.
JEC VMAX sounds interesting. Does any other club run a similar activity?
I have only previouslu sed Autobahn. Thsi carries al sorts of its own issues, not least the distance to get there and then the availability of a suitable stretch of road without traffic.
Doing in the UK does have a certain appeal.
Peter
I have only previouslu sed Autobahn. Thsi carries al sorts of its own issues, not least the distance to get there and then the availability of a suitable stretch of road without traffic.
Doing in the UK does have a certain appeal.
Peter
a8hex said:
I wonder whether anyone has run one at the Woodbridge speed trials. The JEC has done a VMAX here the last few years. Sadly it looks like it isn't likely to happen again as the charges for runway use have shot up.
Woodbridge will now be a Bi-annual event so next one will be 2012XKR's that are de-limited were running at about 160mph after 1.5 miles if I remember
The trouble is at that speed you are running out of runway to get any more speed
Given say a 5 mile run then they would creap up to their Max
Thanks Norman.
This is an interesting thread to which I see you have also contributed:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Looks as if Germany may be the only place freely accessible to V-max.
I'm not sure that I will get much over 155mph, just don't wantthe frustration of coming up against the governor and then not knowing what it would have done if there's a simple way to by-pass it.
Peter
This is an interesting thread to which I see you have also contributed:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Looks as if Germany may be the only place freely accessible to V-max.
I'm not sure that I will get much over 155mph, just don't wantthe frustration of coming up against the governor and then not knowing what it would have done if there's a simple way to by-pass it.
Peter
Edited by 6speedmanual on Tuesday 2nd November 15:35
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