Is 0-60mph in 10.7 seconds too slow?
 

I don't know, but my XJS feels sluggish. I did a 0-60mph test today and came up with (yawn) 10.7 seconds. That's way slower than the 7.6 second claim by the factory I read somewhere. It really seems sluggish on the low-rpm range. Wondering what the problem might be...? I have in the past detected what seems to be a fuel starvation symptom but it runs very smoothly now.

Details:
1995 convertible. No modifications. Excellent condition. 59,000 miles.
4.0 L 6-cylinder.
Running full tank at time of test (93 octane)
No AC running at the time of test.
No missing or surging of the engine on acceleration
No pulling of the brakes or steering.
New fuel filter and Air filter, and new relay for the fuel pump.

That does sound slow, although I'm not sure if the 7.6 seconds is realistic.

I think your car will start off in second gear unless 'sport' mode is selected. If you are not in sport mode that alone could account for your sluggishness

After that I'd wonder about a clogged fuel filter or clogged cat converters

Cheers
DD

I just noticed that you already replaced the fuel filter

Cheers
DD

That's slower than my MGC was and that was only 3 litres.

My car can do it in 8 seconds. I think I'm in sport mode too.

My test (in which I could not get under 10 sec) was done in both regular and sport mode.

Yeah, the 7.6 seconds might not be realistic. Also, I did the test in sport mode and still could not get under 10 seconds. But.....your suggestion about the clogged cats is worth looking into. I appreciate it!

Temperature, humidity and elevation will play a role too. You lose ~10% power for every 1000' above sea level.

Do a run on a cold, dry day at sea level and you will get a different result.

I think the factory numbers are generated by methods that are fairly brutal on the car too, such as holding at it high revs with the brake and then releasing so the engine is already producing near full power when it starts rolling. Very hard on the transmission, but if the transmission only has to last one 1/4 mile pass that's different than how you'd treat your own car.

True enough. I live in the deep south. Temps here are 95-100, and the humidity is like stepping out of a dripping shower. Not Calgary, where you are -- or Edmonton, where I grew up:icon_toast:

Was that with the car in drive?

Putting my turbo400 into 1st and letting it pop into the next gear (or doing so manually) does wonders for the 0-60 time.

It is most certainly not a good figure. The 4.0l is supposed to have equal acceleration figures to the V12... Though it seems a bit hard to see that.

What colour is the tranny fluid? Might be a worn tranny with slipping clutchpacks. The 4hp22 or 24 (should be one of them two) has issues with clutches...

Thanks. Just checked the fluid. It's a healthy pink with no burned cork smell. I did notice though, for what it's worth, that the tranny is over-filled by about 1.5" on the dipstick -- past the squiggly bend in the dipstick.

And, I do notice the occasional hard shift from 1st to 2nd.

Left foot on brake, right foot on gas, tranny in D. What RPM can you achieve? This cam tell if the ZF tranny is worn. Don't do it for long...

I do not know how 1995 models are in terms of self-diagnostics... My car would not report anything if few cylinders were not firing, so I would shortly pull connectors from each spark plugs while in idle and see if it makes a difference. If all cylinders are firing... compression test? (at 59K miles chances are it is good, but still..)

On older cars like mine there are a lot of other things to check like ignition timing, but on 1995 I suppose all is electronic... hard to suggest something... Check Air filter and air passage? Or throttle linkage - does it reach WOT?

Performance figures I found for 1995 model were (reportedly claimed by factory)

4.0l with 4 speed auto transmission:
0 to 60 time 7.9secs
Top speed 147mph

4.0l with 5 speed manual
0 to 60 time 6.9secs
Top speed 147mph

6.0l with 4 speed auto
0 to 60 time 6.6secs
Top speed 162mph

Obviously the above related to full power from new engine / transmission.

1.3s difference... I hard doubt the V12 will really make it in under 7 s.

Oh yes it will Daim. At least, my 1985 will, all day any day.


For the OP, I agree with an earlier poster, look at clogged exhaust.
Greg

Your 85 isn't totally stock mate :D

I don't think any of my 1996 XJ12's will do 7 seconds. Never tried but seems like a stretch for that much weight. With a few minor modifications I'm sure they would do 6 seconds all day long. But mine were never meant to be quick.

To help muddy the waters..... :)

Go to post #21 in this thread

https://www.jaguarforums.com/forum/x...-142347/page2/

I posted a slew of 0-60 times from magazine road tests. The numbers are all over the board!

Cheers
DD