XJR-6 seems a bit slow - worn out blower?
Discussion
Hi there, newbie here so please be gentle!
Tried out an XJR-6 auto which I was expecting tremendous performance from. First supercharger I've tried but this car seems more N/A. Could only hear a faint whine and a nice kick 5000rpm+, doesn't seem to do anything below that. In fact, in the higher gears it feels like a wall at 4000 rpm.
Not what I was expecting at all. High mileage though, so is the blower worn out? anything else I could easily check?
Apart from that, fantastic car!
(btw for comparison I run a 270bhp Fiat Coupe 20VT which is similar power-to-weight)
(this XJR feels like similar performance to a previously-owned v8 740i there must be something wrong with the supercharger??)
Hope you guys can help!
Many thanks.
Richard
Tried out an XJR-6 auto which I was expecting tremendous performance from. First supercharger I've tried but this car seems more N/A. Could only hear a faint whine and a nice kick 5000rpm+, doesn't seem to do anything below that. In fact, in the higher gears it feels like a wall at 4000 rpm.
Not what I was expecting at all. High mileage though, so is the blower worn out? anything else I could easily check?
Apart from that, fantastic car!
(btw for comparison I run a 270bhp Fiat Coupe 20VT which is similar power-to-weight)
(this XJR feels like similar performance to a previously-owned v8 740i there must be something wrong with the supercharger??)
Hope you guys can help!
Many thanks.
Richard
Weird that, plenty people out there offering rebuilds, why would this be necessary if they don't wear?
I'd do a comp test anyway, but the engine itself feels strong enough - just feels like no 'boost' until 5k.
I'm used to turbo engines, I thought blowers did their stuff from like 1000 rpm up?
I'd do a comp test anyway, but the engine itself feels strong enough - just feels like no 'boost' until 5k.
I'm used to turbo engines, I thought blowers did their stuff from like 1000 rpm up?
Superchargers do not wear out like Turbos but they do have bearings. When the bearings go you can buy a new supercharger or get one of those companies to replace the bearings for much less 
Your performance description sounds wrong, get the engine checked out by an expert hopefully it might just be dirty plugs or AFM not like the Top Gear "Supercar" for under £10K where all the horses had bolted
Your performance description sounds wrong, get the engine checked out by an expert hopefully it might just be dirty plugs or AFM not like the Top Gear "Supercar" for under £10K where all the horses had bolted
richardxjr said:
Weird that, plenty people out there offering rebuilds, why would this be necessary if they don't wear?
As P700 has said they either work or the bearings are shot and the make one hell of a noise or stop altogether. The paddles pushing air into the engine don't wear so as to reduce the pressure of the charge. Are the belts slipping on the s/c pulley. is there the distinctive whine as the charger runs up?
G
I ran an XJR6 for 2 years & there was no "wall" or power steps. It was just seamless power right through the rev range. The car you have driven is faulty. Its unlikely to be engine or supercharger wear. The supercharger has an air bypass system that basically recurculates the high pressure air when its not needed to improve economy. There maybe something wrong in there or it could be an electronic fault. Get the car checked at a reputable indepentant Jag specialist.
well they are NOT very powerful you know....
I get far more power from a naturally aspirated motor than that old Eaton compressor system and there is no fade from running the compressor high boost.
It really wasn't a very good system from the word go, and it DRINKS fuel.
Frankly in view of the extra weight and poor handling a properly modified 4L atmo will easily outperform it and do about 10mpg better.
My atmo 3.6L does over 150mph and has fantastic fuel economy up to 30mpg
GT
I get far more power from a naturally aspirated motor than that old Eaton compressor system and there is no fade from running the compressor high boost.
It really wasn't a very good system from the word go, and it DRINKS fuel.
Frankly in view of the extra weight and poor handling a properly modified 4L atmo will easily outperform it and do about 10mpg better.
My atmo 3.6L does over 150mph and has fantastic fuel economy up to 30mpg
GT
gtevo said:
well they are NOT very powerful you know....
I get far more power from a naturally aspirated motor than that old Eaton compressor system and there is no fade from running the compressor high boost.
It really wasn't a very good system from the word go, and it DRINKS fuel.
Frankly in view of the extra weight and poor handling a properly modified 4L atmo will easily outperform it and do about 10mpg better.
My atmo 3.6L does over 150mph and has fantastic fuel economy up to 30mpg
GT
I get far more power from a naturally aspirated motor than that old Eaton compressor system and there is no fade from running the compressor high boost.
It really wasn't a very good system from the word go, and it DRINKS fuel.
Frankly in view of the extra weight and poor handling a properly modified 4L atmo will easily outperform it and do about 10mpg better.
My atmo 3.6L does over 150mph and has fantastic fuel economy up to 30mpg
GT
Jag engines are not meant to be ultimately 'powerful'. The emophasis is on smoothness and driveability, for which you need lots and lots of torque.
I agree that the Eaton 'charger is not as efficient as others, but I guess there were cost and perhaps reliabilty issues which stopped Jaguar from going for another supplier.
What model is your 3.6L? 30mpg sounds very good, as does 150mph...
I put together a conversion that offends a lot of people.
It basically turns the XJS 3.6/4.0L into a V12 killer, and so V12 drivers even with 6.0L cars have a hard time!
U can check up the figures in this year's woodbridge speed trial where the 3.6L car in question hit 140mph and caned away all the 5.3L cars dead easy.
Why be upset?
It drinks HALF the juice of a V12
Will drive rings round a V12 in the corners
Brake far more safely than a V12
Has torque come in a huge slodge from 1500rpm like a diesel and remains pretty much flat to revs which are beyond the range of a V12 (6500+), all this achieved without changing the cams or original exhaust manifolds.
Do that (which I have also done), and you get the figures I am talking about.....150mph+ and if needed throttle back to a steady 80-85mph for 30mpg.
I like win-win, and nothing would ever bring me back to a thirsty compressor car or 8/12 cylinder Jaguar, never mind the age!
GT
It basically turns the XJS 3.6/4.0L into a V12 killer, and so V12 drivers even with 6.0L cars have a hard time!
U can check up the figures in this year's woodbridge speed trial where the 3.6L car in question hit 140mph and caned away all the 5.3L cars dead easy.
Why be upset?
It drinks HALF the juice of a V12
Will drive rings round a V12 in the corners
Brake far more safely than a V12
Has torque come in a huge slodge from 1500rpm like a diesel and remains pretty much flat to revs which are beyond the range of a V12 (6500+), all this achieved without changing the cams or original exhaust manifolds.
Do that (which I have also done), and you get the figures I am talking about.....150mph+ and if needed throttle back to a steady 80-85mph for 30mpg.
I like win-win, and nothing would ever bring me back to a thirsty compressor car or 8/12 cylinder Jaguar, never mind the age!
GT
OK I drove another and performance is the same. The only difference between the cars was that mine has a very long accelerator travel, and the other, lower mileage one, had a quite short travel.
The other car was therefore less hard work to hussle along (different to explain what I mean there!)
I'm coming to the conclusion the Jag is just 'different' to what I'm used to. Holding gears in manual mode brings out the sort of performance I was expecting (together with audible compressor whine throughout the rev-range so I'm reassured about the blower being OK); the auto box certainly doesn't help here.
Still got her booked in with a specialist; a service and good check-over won't do any harm. By now I think a strip-down and clean of the throttle body which I've read can get a bit bunged-up may help too.
There's plenty of scope with this engine to improve the breathing, and may have a bit of a play with boost through alternative pulleys to improve the lower end. I'll be looking to add a bit of grunt without losing any refinement if poss.
Thanks for your comments & assistance
The other car was therefore less hard work to hussle along (different to explain what I mean there!)
I'm coming to the conclusion the Jag is just 'different' to what I'm used to. Holding gears in manual mode brings out the sort of performance I was expecting (together with audible compressor whine throughout the rev-range so I'm reassured about the blower being OK); the auto box certainly doesn't help here.
Still got her booked in with a specialist; a service and good check-over won't do any harm. By now I think a strip-down and clean of the throttle body which I've read can get a bit bunged-up may help too.
There's plenty of scope with this engine to improve the breathing, and may have a bit of a play with boost through alternative pulleys to improve the lower end. I'll be looking to add a bit of grunt without losing any refinement if poss.
Thanks for your comments & assistance
Solved
Took a while I know but it's sorted now!
Well there was a problem, was only producing 0.15bar of boost. Someone had taken the throttle and 'charger bypass valve off before, and not reassembled it correctly, so it was *always* bypassing the supercharger.
Now it's sorted, running the full 0.7bar and WHAT a transformation!
I reckon I was down 100+bhp. Let's just say I'm very happy with the performance now.
Thinking of buying an XJR-6? The problem I had is not common. Go try one, you'll love it
Took a while I know but it's sorted now!
Well there was a problem, was only producing 0.15bar of boost. Someone had taken the throttle and 'charger bypass valve off before, and not reassembled it correctly, so it was *always* bypassing the supercharger.
Now it's sorted, running the full 0.7bar and WHAT a transformation!
I reckon I was down 100+bhp. Let's just say I'm very happy with the performance now.
Thinking of buying an XJR-6? The problem I had is not common. Go try one, you'll love it
Good stuff! 
richardxjr said:
Solved
Took a while I know but it's sorted now!
Well there was a problem, was only producing 0.15bar of boost. Someone had taken the throttle and 'charger bypass valve off before, and not reassembled it correctly, so it was *always* bypassing the supercharger.
Now it's sorted, running the full 0.7bar and WHAT a transformation!
I reckon I was down 100+bhp. Let's just say I'm very happy with the performance now.
Thinking of buying an XJR-6? The problem I had is not common. Go try one, you'll love it
Took a while I know but it's sorted now!
Well there was a problem, was only producing 0.15bar of boost. Someone had taken the throttle and 'charger bypass valve off before, and not reassembled it correctly, so it was *always* bypassing the supercharger.
Now it's sorted, running the full 0.7bar and WHAT a transformation!
I reckon I was down 100+bhp. Let's just say I'm very happy with the performance now.
Thinking of buying an XJR-6? The problem I had is not common. Go try one, you'll love it
Good to hear you've got it sorted.
I hadn't noticed your posting before so hadn't commented. One of the people I work for occasionally drives a 740i and I often used to follow him down a section of road on the way into the office. The performance of his 740i seemed incredibly similar to my 3.2 XJ6. So if your XJR was feeling like that it must have been really sick.
Hi! Glad to hear that all is well with the XJR6. I have had a manual version now for almost six years and still get a buzz each time I get in her. When I first picked her up from an old family friend who happens to be a Jag indie, he told me to be blooody careful because I would never had driven a car with that much power before. He was right to a degree but the trouble is that one gets used to the power and some smaller, much less costly, cars are capable of keeping up. It can be very frustrating to have such power but not notice it!
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