Hi All,
Has anybody here used this aftermarket performance lower supercharger pulley on their XJR6? Was wondering what the word on it is if anybody has? https://www.ebay.com/itm/Jaguar-XJR-...7/182752366418
just noticed it and thought I would ask. Not really looking to upgrade horsepower or anything as I am happy with my XJR6 as it is. Just find it interesting and thought i would share.

 

yes, I have had one on my car for 15 months. The difference is definitely noticeable and worth it. I got my mechanic to fit it, and it was a tight fit with one on the other pulleys or tensioners, but I just needed a new belt on that one as the old one had stretched, so once it was adjusted with a new belt (may have been alternator- can’t remember), the larger supercharger drive pulley fitted fine.
Go for it. - worth the money!
I have posted here somewhere on this before in this X300 section, but you will max out the MAF at 4-4,500rpm under full throttle with this pulley.

 

Thank you very very much, that is really good information to know about the MAF.

 

I’d also recommend buying the ‘Andy bracket’ from Andy Stoddart - there is a long thread in this X300 section- it will give a good extra edge, and with the supercharger you’re will notice more advantage than the lower-powered normally-aspirated engines.

 

Have an 'Andy Bracket" already! I was so amazed how much it woke the car up! I think I got mine about 3 months after acquiring the XJR6. It also help with my fuel mileage.

 

Hi, I also have this upgraded pulley on mar car with and Andy Bracket it makes a very noticeable difference and was an excellent upgrade.

 

Thanks everyone for the endorsement of my revised design of crank sensor bracket. this is much appreciated.

When I programmed the fuelling in the production ECU, I had to over-fuel the engine quite significantly, to keep the exhaust gas temperatures down to 950degC (You may not believe it, but adding more fuel actually cools the exhaust !). Exceeding the measureable airflow of the air meter by less than 10%, as will occur when fitting a larger crank pulley, will cause the engine to run less rich. This is acceptable as the condition cannot be maintained continuously in road driving.

 

Thank you so much Andy! I really appreciate you explaining that. I was actually thinking the opposite would happen when the MAF sensor exceeds its limit. Like it would go way to lean and with the boost and good bye engine. it is very reassuring to me that you explained that. Well I know what my next project is for sure now. Cheers!

 

thanks Andy . I always enjoy your firsthand facts from the 1990s when you were at the coal face of the X300s.
I believe you re- the extra fuel cooling things.
I remember reading years ago that the 1950s Maserati 250F GP cars were essentially fuel-cooled, doing about 3mpg

 

Has anyone here got the larger lower supercharger pulley fitted?

I have, and noticed that if I absolutely floor the accelerator I get a brief (3 or 4 seconds) low squeal, and the other day I also noticed a burning or very hot smell in the cabin (after foot-to-the-floor acceleration). I popped the bonnet when I stopped and checked the belt, which seemed tight and tracking fine. I wondered if what I'm experiencing might be due to some slight initial belt slip under very hard acceleration?

Has anyone else with the larger pulley fitted experienced anything similar? Thanks.

 

You may well be experiencing some belt slip, as the torque required to drive the supercharger will increase, as the boost pressure is higher due to the higher drive ratio. You could try increasing the belt tension. The best tool to measure belt tension is a Clavis belt tension meter, which measures the natural frequency of the belt. A good auto shop might have one of these meters. The frequency of the long span between the supercharger and the crank pulley should be 113Hz. Alternatively, if the belt tension is measured with a Burroughs gauge it should be 835-875N when cold.

 

Thanks very much for the insights Andy. I get her serviced and looked after by Barny Jones in Farnham, so next time the car's booked in I'll get them to check tension. To be fair if I feed the acceleration in it's fine and only does this if I'm heavy footed. There's a quick and simple solution to this before I get the belt tension checked!

 

Could your crankshaft pulley possibly be delaminating? See the related threads for the simple white line test. It is a common failing on these engines with age, and your pulley mod might just have tipped it over the edge.

 

Possibly, but with a mileage of about 32,000 I’m not overly worried. I did buy a chalk pen for marking steel to mark the pulley/harmonic balancer. But with the bonnet open, because it’s hinged at the front it’s impossible to get access to mark it without removing a load of stuff. So, I’ll leave it for the garage to check when I get a service. Feed the power in though and it’s fine, which to me suggests it could just be optimising belt tension. Or not being lead-footed!