There is a company called Racing Green of Hampshire UK that is advertising a Supercharger pulley upgrade and ECU re-map to the 4.2 that gives an extra claimed 70 Bhp without affecting fuel consumption. Has anyone had these mods and if so what experiences did you have before, during and after? Any advice would be appreciated.

 

Highly unlikely to get 70 bhp, you could start also with asking RG for some dyno evidence.

I would guess more like 40 to 50 or so max on a (very) good day...

 

You will also lose power as the intercooler system heats up, since the factory supercharging cooling system is not capable of quickly removing all of the additional heat generated.

 

For what it's worth, I have had three of my previous cars remapped in the past (2 turbo diesels and 1 petrol) and I have always kind of regretted doing it. Yes, you do get extra power, but the car just doesn't feel right somehow.

 

70hp doesnt sound too far off. most likely its hp at the flywheel and not the tires.

 

I had my 225 TT remaped (up to 265bhp) when it was 2 years old with 16k miles on the clock, it pulled like a train, I loved it, it ran this way for the next 8 years until I bought the XK8 almost exactly one year ago, it then had 100k miles on the clock. The day I had planned to put it into autotrader, the turbo blew. Even using a cheap replica turbo from China, the job still cost me £1000 and highlighted a crack in the exhaust manifold.

So I would say, if you plan to keep the car for only a couple of years, go for it, if you are in it for the long term, stick with what you have got.

 

Plenty of suppliers offering the same but the 70 BHP is a bit theoretical rather than actual. It will give you more low end power so it seems more powerful but very little at WOT. The Eaton charger can be spun faster but produces lots more heat, which eats the extra power Re-maps are now (according to UK experts) useless for the 4.0 engines, something can be done for the 4.2s. If you are close to Racing Green consider also TL Jaguars in Wokingham who offer this mod, cats and other mods for more power no heat and if you have lots of $$$ then consider a KB supercharger replacement. Good for 100+ BHP although you might want the Quaiffe LSD to help control it too.

 

Thanks very much for all of the comments. On balance for the time being I think that I will keep things as they are.

 

Good decision. While I agree that you can never have too much power, I would be the first to admit that nobody really needs 400hp in the first place