Hi Guys, hope some one can answer my question about the top speed of my Jag. Will have the opportunity soon to open her up on an unpatroled deserted road. Will the 5-speed ZF stay in 4th if you hold the throttle wide open? If so, then top speed is attained in 4th gear, right? What kind of top speed can I expect on a level road with no wind with 2 guys up? Some Fords that I owned would not shift into O"Drive with the pedal to the metal. Thanks for your help.
Spillwaybob

 

Moved for you for better responses...........

Anyone?

 

The non-Supercharged XJs can get up to about 150mph and are aerodynamically limited. The Supercharged XJR/Super V8 can go 155mph before the speed limiter kicks in. Someone on youtube somehow got their X300 XJ6 to go 150+mph which is impressive considering that it has much less horsepower than the V8.

I've taken mine up to about 135mph on an empty 100 mile road closed by the police with me and only a couple of other cars on te road (long story) . The aerodynamics are pretty bad on these cars, and they can get a bit unstable at high speed. The front end tends to gradually drift left and right and requires you to steer the car to keep it straight. It's no german car, but its still not as scary as a Jeep Grand Cherokee that topped out at a measly 105mph.

I'd keep the car in drive and sport mode enabled to get the top speed. I'd imagine the transmission will be able to determine if 4th or 5th will get the top speed considering ambient conditions and engine wear and etc. You can always keep it in 4 on the J gate if you prefer though.

 

Car & Driver tested a Vanden Plas in their November 1999 issue, which was probably a model year 2000 car. They reported a top speed of 144mph reached in either fourth or fifth gears.

 

Sorry Mate, I'm going to have to totally disagree with you there! These cars are not "aerodynamically limited" they all have the same body fittings whether they are an XJR or a XJ8, the only things different are the wheels, trans and engine. I have had 150mph out of mine in D (5th) and it hit the limiter but had a lot left to give. I happen to know they are good for 175ish unrestricted. The XJR can touch nearly 200 I'm told by a very reliable source in Jaguar Cars.

As for the car's actual aerodynamics, they are far from bad. In fact they are still regarded as one of the greatest aerodynamic designs ever created, developing very little in the way of drag. At any speeds I find them to be stable, but cruising across France at 130mph with Cruise Control on, the car was as comfortable as it would be at 70mph.

If your car is trying to change direction by itself perhaps you have a suspension issue or your tracking is out.

 

Thanks to all of you responders. I am a little surprised at what burmaz said about the aerodynamics of the XJ's at very high speed. As low and sleek as the car is, I would think it would have excellent aerodynamics. Perhaps there is a suspension or tire problem with his car. I have already had mine to 115 and it felt fine. When I do the top speed run, if I survive, I'll let you know how it behaved.
Think I will leave the trans. in D and let it do whatever it wants to. I don't particularly want to hit the rev. limiter or the red line.....my engine has 52K on it with original timing chain tensioners but runs very well. Thanks again guys.
Spillwaybob

 

Nope its not just my car. Others with XJRs can chime in on the high speed stability. I think it was either Car and Driver or Motor Trend that critized the X300 XJR for this problem too (same body style/aerodynamics as the X308).

They look low and sleek, but if you look at a modern car side by side to the XJ8, you will notice that the XJ8's front end is totally flat and is like a brick moving through the air, the windshield is very steep which creates front end lift, and there is severe wind turbulence over the rear window (which is why in the rain, water tends to collect on the rear window instead of sliding off) , for it does not follow the path of wind. There are videos on youtube of the development of the XJ, and when it is shown in the wind tunnel, although the editors tried to hide it, it isn't that great. In fact the drag coefficent is .37! Possibly the worst in its class!

High speed drives aren't bad, but I just wouldn't want to drive everyday at 120+mph on the autobahn in a X308 unlike a German car. That is all. I have driven about 115mph in a Pontiac Grand Am while standing on the throttle, and thank God I was wearing some strong deodorant. That drive was quite scary.


I guess poor aerodynamics are the price for beautiful styling (for the XJ). I cost I'm willing to pay.

 

Burmaz... the problem with the X300's high speed stability was the ZF steering rack that was fitted. The aerodynamics are average for X308, with a .35 drag coefficient.

The fastest I've ever been in a car was 120+ (the speedo only goes to 120) and it felt rock solid . Also, that was in a fully loaded Ford Escape. That car was styled with nose aerodynamics in mind.

DavidN, a fellow XJ sport 4.0 driver, has had his car up to 155 on the autobahn. He said that the car had some more go left in it. These cars have the potential for very high speed, thanks to the 6800rpm redline and 3.08 gears.

I've only ever been up around 100 in the XJ, but it felt excellent.

Burmaz, I think you should try a more solid sidewalled tyre... the softer the tyres, the floatier a car can feel due to centripetal force. you, too, have 18"s, but something like a Pilot Sport PS2 would probably be far better than Continentals (if I remember what you said correctly).

The aerodynamics of the passenger compartment are poor. The windshield angle is excellent, but the rear windscreen is at a very poor angle for aerodynamics. Far too steep. The front of our cars is, however, a huge improvement over the (more beautiful, IMO) Series 1. The nose of that car can't withstand more than 120 without being a danger. (wedge-shaped! Also, engine is far back.) Luckily the top speed was 115.

I'm pleased that our car's nose defies aerodynamics. Every car has a similar shape now, you can look at the noses of a lot of cars and see the same exact degree of steepness/ same air funneling. The XJ has a similar rake in the nose to an E38 BMW, which is interesting. (another beautiful car)

I have heard 150, but my knowledge has always been that this car is electronically limited to 155. There are no aerodynamic speed limiters on X308 SWB Jaguars, I do know that. Hopefull DavidN will stop by, and recount his story. LWB, I'm not 100% sure

 

The high speed stability is not just my car. I have read many accounts of this issue. Even Motor Trend or C&D which compared the XJR to the Volvo 850R (!) and the E34 M5, and the high speed stability of the Jag was considered to be much poorer than the others. There is no 'aerodynamic' speed limiter on a car, aero limited top speed is a property of the car. However, I am comparing the X308 to another car I have driven very quickly, a BMW E39. That is an extremely high bar!

The wind-shield on the X308 is too steep. This creates wind turbulence where the top of the wind-shield and roof meet. This wind can be heard at high speeds. The cd is .35-.37 depending on the model. I do not know of a luxury car of the era that exceeds .37. Many are in the low 30s, and some even in the high 20s.

However, the X308 is not bad at high speed. Its not like a suicide mission. Its just that you can tell you are driving very fast in the X308, whereas in the BMW, you can creep up to these speeds without realizing it.

 

My old 2008 XJ8L (X350) was speed limited to 105. Hit that a couple times on a freeway on-ramp. Fail!

 

Haha. Wow really just 105mph? Yikes!

Btw how do the X300, X308, and X350 all compare in terms of handling and ride comfort? Does the X308 feel about the same as the X300?

 

My X300 and X308 were/are XJR's and the 350 an XJ8L. The XJR's handled very similar but the 308 feels more balanced and stable than the 300. I think the weight of the V8 compared to the 6 may be part of that feeling. The X350 is too much like a Lincoln Town Car to give it a fair compare.

 

rvirginia, The steering rack (different between 300 and 308, but both ZF) probably made a bigger difference. I'm fairly sure the V8 weighed a bit less than the Straight-6.

I Thought that the X350 was limited to 118mph? 105 is just sad.

@Burmaz... +1 for 'suicide mission' I am chuckling to myself! And I also read that comparo of the XJR(6) vs. the Volvo and BMW, I remeber them mentioning high speed instability. Our steering setup is different from the XJR-6's.

About the "aerodynamic limitations", I don't believe a 290hp V8 can be held back by 150mph air... I just don't buy it. The XJR has the guts(and gearing) to pull well over 170mph. DavidN had his XJ Sport up to 155, with extra acceleration to be had. Our Sport has better aero than the LWB though, as far as I remember.

The E39 BMW is great. Although I'll stand by my XJ, even if it isn't quite the autpbahn-meister. (You will too I'll bet) The E39, by today's standards, has a much more vertical fascia, but the atrium is a much more competent shape than our Jag's.

 

X308 R's - When I bought mine, I asked the guy half in jest what he'd had out of it. He said a recent trip to Germany showed 170mph on the sat-nav, he was behind an M6 BMW (V10 510BHP) for over 30 miles. The limiter was removed when he had it tuned at Paramount.

Another car I bought did almost daily trips to Europe - again this hit the limiter and sat there all day at 150mph.
If an XJ8 is in good order, suspension and bushes in good shape I've no doubt they can find the limiter without issue.

If high speed runs are attempted the car has to be in tip top shape. A good point are the tyres - Y96 rated extra load, from high performance manufacturers are worth every penny. Things happen quickly at high speed. Brakes too are important.

I don't feel the need to travel that fast, but it's nice to know they're capable cars. Mira high speed tests showed they're fast stable cars, 1.8 tons reasonable aerodynamics outstanding suspension and 300bhp makes it relatively easy to achieve.

 

I had mine at around 140mph (speedometer reading) one time. It felt solid to me, but I'm used to going fast in rougher cars, so don't really know how to compare... It felt like it had a lot more to go, but I chickened out being that I was on the freeway near home.

All of my newer cars have been heavily speed limited, so I don't know how they feel going fast.

 

I'm very surprised of what I'm reading here, because my XJ8 is with the smallest engine - 3.2 V8 and I've pushed it many times up to 220km/h and surely it could go for at least 10-15 more.

So how is it possible to have one and the same top speed in 3.2, 4.0 and supercharged?!

P.S> It's not something I'm proud of, but I hit 90mph everyday morning in the city while going to work...

 

Because back then Car makers had a deal where everything they made was limited to 150mph, for environmental reasons I'm told.

Now most seem to have forgotten about the deal and are back to making 170mph+ cars

 

Yeah, the main difference is not top speed, but how fast you get there. The XJR gets there quicker.

 

.....a *lot* quicker ;-)

 

@Stu, that EU top speed agreement was 155mph, (25X+-kph), not 150mph. Although, I believe the 3.2 was only capable of 144mph.