Is my 450 slow ?
Discussion
Took delivery of a 2015 Jaguar XFS last weekend. It has a 3.0 supercharged V6, with a 0-60 time quoted as 5.9secs.
It is quick....very quick. It pulls and pulls and just keeps pulling and doesn't seem to let up, even on a steep hill. Very impressive.
Took it for a run along a route I use regularly in the TVR and from a standing start at a junction, it reached the same speed before braking for the first corner (in the region of 60) as the TVR would.
This begs the question, how can that happen when the TVR is supposed to have a 0-60 time of around 4.7secs ?
Is the 0-60 time quoted completely unrealistic or is my Chimaera down on power ?
It is quick....very quick. It pulls and pulls and just keeps pulling and doesn't seem to let up, even on a steep hill. Very impressive.
Took it for a run along a route I use regularly in the TVR and from a standing start at a junction, it reached the same speed before braking for the first corner (in the region of 60) as the TVR would.
This begs the question, how can that happen when the TVR is supposed to have a 0-60 time of around 4.7secs ?
Is the 0-60 time quoted completely unrealistic or is my Chimaera down on power ?
Yes it is the diesel and is an auto and it's the older XF (2015) not the newer one, which is slightly quicker.
All good arguments and things like weight and gear changes etc but my thinking was that both cars are reaching around 60 in the same distance and it's a relatively short distance so should both take approximately the same time.
If the TVR was over a second quicker to 60, I would have expected it to be at a higher speed by the corner than the Jag was. No ?
I have had the car on a dyno twice in the 15 years I have had it. The latter time (2015 ish) it had a few runs and the peak bhp results were quite variable so I wasn't sure how reliable they were but the top figure was around 250bhp from memory. I could post the curve if you are able to comment on it for me ?
All good arguments and things like weight and gear changes etc but my thinking was that both cars are reaching around 60 in the same distance and it's a relatively short distance so should both take approximately the same time.
If the TVR was over a second quicker to 60, I would have expected it to be at a higher speed by the corner than the Jag was. No ?
I have had the car on a dyno twice in the 15 years I have had it. The latter time (2015 ish) it had a few runs and the peak bhp results were quite variable so I wasn't sure how reliable they were but the top figure was around 250bhp from memory. I could post the curve if you are able to comment on it for me ?
Edited by taylormj4 on Monday 19th September 14:43
ClassiChimi said:
Iis your 450 slow,,, hmm. Get your phones video camera out, do some 0-60 mph drag starts and then get your stop watch out and check the footage. That will give you an indication of how yours performs.
I've done this in the past and I manage 60 mph in 4.5 seconds but it is a very rough guess.
To get a fast time in the Tvr you've got to be prepared to control wheel spin etc and that's where you loose time, that and gear changes compared to a modern car.
Now that's a good idea! Yes, no wheel spin. It's a 90degree turn out of a junction to start so the tail would be straight out if I did.I've done this in the past and I manage 60 mph in 4.5 seconds but it is a very rough guess.
To get a fast time in the Tvr you've got to be prepared to control wheel spin etc and that's where you loose time, that and gear changes compared to a modern car.
Chaps all very valid points. In particular are the gear changes, which I could be slow at. ALthough I only change gear twice to 70, whereas the Jag is probably making at least 4 as it is an 8-speed box, so it probably evens out.
The test I am doing is one that I set up a long time ago to make sure my TVR's performance is not deteriorating.
I know that from a standing start, I can reach a certain speed before having to brake for a corner. So when I get the chance as the road is clear, I run this test. If the engine performance is down (assuming my skills are constant), the same rough speed should be reached.
However, I was initially surprised that a car that has a 0-60 time that is supposedly over 1 second slower than my TVR could reach the same speed over the same distance.
However, after further thought and the above threads, maybe this is what is happening:
On the graph below, the Jag is the red curve and the TVR is the blue curve. If the x-axis is time and the y-axis is speed, the area under the curve is the distance travelled. So the Jag is slower starting than the TVR (as I have shown) but then the Jag's bhp helps it to keep increasing it's speed whereas the TVR's rate of speed increase is dropping.
By the end of the chart, the area under both curves is around the same, so both cars have covered the same distance but the Jag's speed is higher than the TVRs. So whilst the Jag might be slower to 60, if the test is allowed to go to a slightly higher speed, the slower 0-60 car will catch up and at a certain point they will have covered the same distance but the Jag would be at a higher speed at the end.
Think that makes sense ?
The test I am doing is one that I set up a long time ago to make sure my TVR's performance is not deteriorating.
I know that from a standing start, I can reach a certain speed before having to brake for a corner. So when I get the chance as the road is clear, I run this test. If the engine performance is down (assuming my skills are constant), the same rough speed should be reached.
However, I was initially surprised that a car that has a 0-60 time that is supposedly over 1 second slower than my TVR could reach the same speed over the same distance.
However, after further thought and the above threads, maybe this is what is happening:
On the graph below, the Jag is the red curve and the TVR is the blue curve. If the x-axis is time and the y-axis is speed, the area under the curve is the distance travelled. So the Jag is slower starting than the TVR (as I have shown) but then the Jag's bhp helps it to keep increasing it's speed whereas the TVR's rate of speed increase is dropping.
By the end of the chart, the area under both curves is around the same, so both cars have covered the same distance but the Jag's speed is higher than the TVRs. So whilst the Jag might be slower to 60, if the test is allowed to go to a slightly higher speed, the slower 0-60 car will catch up and at a certain point they will have covered the same distance but the Jag would be at a higher speed at the end.
Think that makes sense ?
Edited by taylormj4 on Tuesday 20th September 10:57
ClassiChimi said:
The question was is my 450 down on power, what mileage is your 450 at, what air filter and cam etc,
The only way to be sure would be a recent power run on a dyno ( not that cheap)
Or a few timed runs up a drag strip ( cheap) in comparison and a lot more fun.
There's another thread on here about a get together of Tvr boys at Shakespeare raceway near Stratford (Warwickshire)
That would be a perfect opportunity to test your cars speed in safety,,
You'll also have plenty of time to discuss your car with other Tvr nutters who know these engines inside out.
Just a thought
Sounds good. I'm interested !The only way to be sure would be a recent power run on a dyno ( not that cheap)
Or a few timed runs up a drag strip ( cheap) in comparison and a lot more fun.
There's another thread on here about a get together of Tvr boys at Shakespeare raceway near Stratford (Warwickshire)
That would be a perfect opportunity to test your cars speed in safety,,
You'll also have plenty of time to discuss your car with other Tvr nutters who know these engines inside out.
Just a thought
It's almost completely standard. Done just over 65k miles, standard air filter and original cam. Regularly serviced. Full ACT induction hose, new AFM. Was interested in further tuning but have been advised that the next best thing to do is to have a better ECU and loom like Emerald and I'm looking at nearly £3k so that's put it on hold for a while.
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