beefing up my XJR
Discussion
I'm a little disappointed with the straight line grunt... it feels kind of 'restricted'. It's probably due to the weight that the car feels that way, but I've already heard rumours of a pulley conversion to up the boost some.
What needs to be done to free up some more wild cat power?
I don't want it noisy, but a bit of beef on kickdown would be nice
What needs to be done to free up some more wild cat power?
I don't want it noisy, but a bit of beef on kickdown would be nice
I think our own Marquis Rex once said that the best, cheapest, most reliable way to free up more ponnies on the newer (4.0 & 4.2 V8) supercharged Jags was to fit bigger, better intercooling.
But don't quote me on that, as i are only a lowly grease monkey and he is a big shot Automotive Engineer....
...too bad you can't fold some seats down to save some weight....
Also check to see if the MAF sensor is clean, air filter is clean, injectors are clean, no vacuum leaks, no exhaust leaks, etc.
But don't quote me on that, as i are only a lowly grease monkey and he is a big shot Automotive Engineer....
...too bad you can't fold some seats down to save some weight....
Also check to see if the MAF sensor is clean, air filter is clean, injectors are clean, no vacuum leaks, no exhaust leaks, etc.
Edited by Trooper2 on Tuesday 30th September 01:55
Trooper2 is close to the mark there talking about the intercoolers. I remember that when we did the XK180 we ended up with each intercooler brick having it's own cooling pump & radiator.
First step would be to make sure that the coolant is topped up & the system bled.
I would have the coolant pump tested if there is no improvement in power - it may have worn out.
Bear in mind that the engines were mapped on both 95 & 98 octane whith the engine always trying to get to the 98 octane settings and being reined in by the knock sensors I would fill the tank with 98 to get extra power.
Hope this helps.
First step would be to make sure that the coolant is topped up & the system bled.
I would have the coolant pump tested if there is no improvement in power - it may have worn out.
Bear in mind that the engines were mapped on both 95 & 98 octane whith the engine always trying to get to the 98 octane settings and being reined in by the knock sensors I would fill the tank with 98 to get extra power.
Hope this helps.
I believe supercharger pulley upgrade and sports airfilter will give up to 10% bhp boost, but I think sports exhaust is usually recommended first (no ecu remap required) as the stock Jaguar one greatly inhibits engine breathing and performance in order to keep sound levels down.
I looked into getting a stainless cat-back sports exhaust for mine but the cost was looking like about £900 including fitting and VAT - difficult to justify imho.
Unless in sports mode or using semi-auto I think the gearing can be a bit low personally, which I guess is ideal for cruising around but not outright performance.
Chris
I looked into getting a stainless cat-back sports exhaust for mine but the cost was looking like about £900 including fitting and VAT - difficult to justify imho.
Unless in sports mode or using semi-auto I think the gearing can be a bit low personally, which I guess is ideal for cruising around but not outright performance.
Chris
Another ( more expensive ) option would be to replace the Roots
with a twin screw type (Sprintex) charger. These are more expensive
to manufacture than the Eaton, due to the complexity of machining the
helical lobed rotors. Which is probably why Jag fitted Eaton's in the
first place. The design guys will know if this is the case,though.
But they do have some advantages:
They run cooler.
They consume less power to drive.
They are a more compact installation.
They have a higher volumetric efficiency ( VE ) over a
comparable roots.
I,ve read they can be worth up to 40 bhp, though that would depend
on pulley size used, intercooling, etc. Might be worth looking into.
I can't believe you think it's not fast enough !
with a twin screw type (Sprintex) charger. These are more expensive
to manufacture than the Eaton, due to the complexity of machining the
helical lobed rotors. Which is probably why Jag fitted Eaton's in the
first place. The design guys will know if this is the case,though.
But they do have some advantages:
They run cooler.
They consume less power to drive.
They are a more compact installation.
They have a higher volumetric efficiency ( VE ) over a
comparable roots.
I,ve read they can be worth up to 40 bhp, though that would depend
on pulley size used, intercooling, etc. Might be worth looking into.
I can't believe you think it's not fast enough !
jag guru said:
Another ( more expensive ) option would be to replace the Roots
with a twin screw type (Sprintex) charger. These are more expensive
to manufacture than the Eaton, due to the complexity of machining the
helical lobed rotors. Which is probably why Jag fitted Eaton's in the
first place. The design guys will know if this is the case,though.
But they do have some advantages:
They run cooler.
They consume less power to drive.
They are a more compact installation.
They have a higher volumetric efficiency ( VE ) over a
comparable roots.
I,ve read they can be worth up to 40 bhp, though that would depend
on pulley size used, intercooling, etc. Might be worth looking into.
I can't believe you think it's not fast enough !
Well it's ok... But it's not what I expected. Kind of want it BRUTAL on kickdown in sport mode... and it just feels 'rapid'.with a twin screw type (Sprintex) charger. These are more expensive
to manufacture than the Eaton, due to the complexity of machining the
helical lobed rotors. Which is probably why Jag fitted Eaton's in the
first place. The design guys will know if this is the case,though.
But they do have some advantages:
They run cooler.
They consume less power to drive.
They are a more compact installation.
They have a higher volumetric efficiency ( VE ) over a
comparable roots.
I,ve read they can be worth up to 40 bhp, though that would depend
on pulley size used, intercooling, etc. Might be worth looking into.
I can't believe you think it's not fast enough !
I'm not moaning, but it does feel like it's holding back a lot
groomi said:
KR - You've bought an XJR! Bloomin 'eck, when did this happen?
Is it a straight six or a V8?
Last week Is it a straight six or a V8?
V8 of course... I want to get something else though, I wanted to beef this one up but I'm starting to get requests for weddings and chauffeur work with it... Are the straight six XJR's easier to tune, I might get one of them as well for a bit less and turn it into a monster
How's your cat?
Jag guru is indeed right with the advantages of a twin-screw, except for the possible gains with a good setup.
Depending on the pulley setup you can expect at up to 150 rwhp more then stock, so a comfortable 200 BHP more on the engine (depending on drive train loss).
I can assure you that this power is noticable :-), great fun, it has transformed my car completely.
I usually have my pulley setup for a more modest 430 rwhp (a very comfortable 525 BHP+), this is what Jagaur should have done ears ago.
Here is a thread with some more info:
http://www.pistonheads.com/gassing/topic.asp?h=25&...
Andre.
Depending on the pulley setup you can expect at up to 150 rwhp more then stock, so a comfortable 200 BHP more on the engine (depending on drive train loss).
I can assure you that this power is noticable :-), great fun, it has transformed my car completely.
I usually have my pulley setup for a more modest 430 rwhp (a very comfortable 525 BHP+), this is what Jagaur should have done ears ago.
Here is a thread with some more info:
http://www.pistonheads.com/gassing/topic.asp?h=25&...
Andre.
avos said:
Jag guru is indeed right with the advantages of a twin-screw, except for the possible gains with a good setup.
Depending on the pulley setup you can expect at up to 150 rwhp more then stock, so a comfortable 200 BHP more on the engine (depending on drive train loss).
I can assure you that this power is noticable :-), great fun, it has transformed my car completely.
I usually have my pulley setup for a more modest 430 rwhp (a very comfortable 525 BHP+), this is what Jagaur should have done ears ago.
Here is a thread with some more info:
http://www.pistonheads.com/gassing/topic.asp?h=25&...
Andre.
Jeez Andre..............that is impressive ! plus 50 % on standard roadgoing bhp !Depending on the pulley setup you can expect at up to 150 rwhp more then stock, so a comfortable 200 BHP more on the engine (depending on drive train loss).
I can assure you that this power is noticable :-), great fun, it has transformed my car completely.
I usually have my pulley setup for a more modest 430 rwhp (a very comfortable 525 BHP+), this is what Jagaur should have done ears ago.
Here is a thread with some more info:
http://www.pistonheads.com/gassing/topic.asp?h=25&...
Andre.
transmission longevity would be my only concern. How long have
you been running at this power level ?
Sprintex quote + 35 % ( bhp) possible.............but you're way above
that !
I know the In the US they have had racing 4.5 XKR'S running at this kind
of power level. But I never thought it was viable on a road going car.
Edited by jag guru on Sunday 5th October 09:59
Edited by jag guru on Sunday 5th October 13:41
When I started with my first conversion 2 years ago (was more a proof of concept), I never thought this would be possible, but now some conversion changes later there is still no end to what it can reach.
I guess I have driven with this amount of power for about 20-30Kmiles. But already 75Kmiles with higher then stock levels, and I have used evry bit of the extra power ;-) Now my car has done 130Kmiles.
Of course the 470 rwhp (or our next goal of 500 rwhp) is not something to contineus use, which is one of the reasons I usualy stick to the 430 rwhp.
The 4.0 gearbox (a Mercedes one) is pretty tough, and is already build for sustained 580nm, and can handle peaks of 30% more. So far with my car (and also NormanD's) it has proven to very strong.
Funny enough there is a safety build into the system and that is the stock open diff. In 1st (or even 2nd) the forces would be too strong I guess if there would be grip on both wheels, but thanks to the open diff you never get into that situation ;-).
Andre.
I guess I have driven with this amount of power for about 20-30Kmiles. But already 75Kmiles with higher then stock levels, and I have used evry bit of the extra power ;-) Now my car has done 130Kmiles.
Of course the 470 rwhp (or our next goal of 500 rwhp) is not something to contineus use, which is one of the reasons I usualy stick to the 430 rwhp.
The 4.0 gearbox (a Mercedes one) is pretty tough, and is already build for sustained 580nm, and can handle peaks of 30% more. So far with my car (and also NormanD's) it has proven to very strong.
Funny enough there is a safety build into the system and that is the stock open diff. In 1st (or even 2nd) the forces would be too strong I guess if there would be grip on both wheels, but thanks to the open diff you never get into that situation ;-).
Andre.
avos said:
When I started with my first conversion 2 years ago (was more a proof of concept), I never thought this would be possible, but now some conversion changes later there is still no end to what it can reach.
I guess I have driven with this amount of power for about 20-30Kmiles. But already 75Kmiles with higher then stock levels, and I have used evry bit of the extra power ;-) Now my car has done 130Kmiles.
Of course the 470 rwhp (or our next goal of 500 rwhp) is not something to contineus use, which is one of the reasons I usualy stick to the 430 rwhp.
The 4.0 gearbox (a Mercedes one) is pretty tough, and is already build for sustained 580nm, and can handle peaks of 30% more. So far with my car (and also NormanD's) it has proven to very strong.
Funny enough there is a safety build into the system and that is the stock open diff. In 1st (or even 2nd) the forces would be too strong I guess if there would be grip on both wheels, but thanks to the open diff you never get into that situation ;-).
Andre.
I would say it looks money and time well spent. Arden have aI guess I have driven with this amount of power for about 20-30Kmiles. But already 75Kmiles with higher then stock levels, and I have used evry bit of the extra power ;-) Now my car has done 130Kmiles.
Of course the 470 rwhp (or our next goal of 500 rwhp) is not something to contineus use, which is one of the reasons I usualy stick to the 430 rwhp.
The 4.0 gearbox (a Mercedes one) is pretty tough, and is already build for sustained 580nm, and can handle peaks of 30% more. So far with my car (and also NormanD's) it has proven to very strong.
Funny enough there is a safety build into the system and that is the stock open diff. In 1st (or even 2nd) the forces would be too strong I guess if there would be grip on both wheels, but thanks to the open diff you never get into that situation ;-).
Andre.
4.5 now in Europe, rated at 480 bhp/ 472 lb/ft.........and that still
isn't matching your car.
Unfortunately, I don't have the 160,000 Euro or so, they want for one.
And since that is using a special crank, I don't see a lot of difference
in using the twin screw charger as an alternative.
At this point, we're well away from factory standard parts anyway.
Thanks,it was really interesting to hear about your car.
Good luck with the project......
Ardens conversion is much cheaper than 160.000 euros, it is about 30.000 Euro only (without VAT), they also have a 530BHP version for just 40.000 Euros, also without VAT.
But you cannot get 90 BHP more by just increasing the engine size from 4.2 to 4.5 liters. Chances are they have lowered the compression ratio to allow for more boost with the (H)Eaton, and a possibility would be to have the engine rev more with stronger internals. The latter is not advisable with the stock internals.
Not sure if I understand your comment "And since that is using a special crank, I don't see a lot of difference in using the twin screw charger as an alternative."
I can only see the twin-screw as an true alternative and on top of that (imho) the only worthwhile performance enhancement there is, and it is only a fraction of the costs from Ardens ;-).
Thanks for the thumbs up,
Andre.
PS Arden is not strenthening the Gearbox...
But you cannot get 90 BHP more by just increasing the engine size from 4.2 to 4.5 liters. Chances are they have lowered the compression ratio to allow for more boost with the (H)Eaton, and a possibility would be to have the engine rev more with stronger internals. The latter is not advisable with the stock internals.
Not sure if I understand your comment "And since that is using a special crank, I don't see a lot of difference in using the twin screw charger as an alternative."
I can only see the twin-screw as an true alternative and on top of that (imho) the only worthwhile performance enhancement there is, and it is only a fraction of the costs from Ardens ;-).
Thanks for the thumbs up,
Andre.
PS Arden is not strenthening the Gearbox...
avos said:
Ardens conversion is much cheaper than 160.000 euros, it is about 30.000 Euro only (without VAT), they also have a 530BHP version for just 40.000 Euros, also without VAT.
But you cannot get 90 BHP more by just increasing the engine size from 4.2 to 4.5 liters. Chances are they have lowered the compression ratio to allow for more boost with the (H)Eaton, and a possibility would be to have the engine rev more with stronger internals. The latter is not advisable with the stock internals.
Not sure if I understand your comment "And since that is using a special crank, I don't see a lot of difference in using the twin screw charger as an alternative."
I can only see the twin-screw as an true alternative and on top of that (imho) the only worthwhile performance enhancement there is, and it is only a fraction of the costs from Ardens ;-).
Thanks for the thumbs up,
Andre.
PS Arden is not strenthening the Gearbox...
Yeah..............160,000 euro was for the whole car !But you cannot get 90 BHP more by just increasing the engine size from 4.2 to 4.5 liters. Chances are they have lowered the compression ratio to allow for more boost with the (H)Eaton, and a possibility would be to have the engine rev more with stronger internals. The latter is not advisable with the stock internals.
Not sure if I understand your comment "And since that is using a special crank, I don't see a lot of difference in using the twin screw charger as an alternative."
I can only see the twin-screw as an true alternative and on top of that (imho) the only worthwhile performance enhancement there is, and it is only a fraction of the costs from Ardens ;-).
Thanks for the thumbs up,
Andre.
PS Arden is not strenthening the Gearbox...
As regards the crank ? this isn't obviously factory standard as it's
increasing the displacement from 4.2 to 4.5 ?
Therefore, it,s a leap of faith imo.
Consequently, It's no more so, to ditch the Eaton for the twin screw,
and retain the standard 4200 cc ?
Both methods are major departures from standard spec.
that's what I was trying to say ( badly ) sorry !
Edited by jag guru on Sunday 5th October 11:46
Andre, I,ve PM'd you to try and better explain what I've been trying
to convey here. In a nutshell, I think your method of obtaining these power
levels is more cost effective than the big capacity 4.5 alternative.
Regards JG
Edited by jag guru on Sunday 5th October 13:34
I've just been given a 'Heads up' on this Thread.
Andre fitted the Twin Screw Supercharger on my 4.0Lt XKR
470 rwhp using Jaguars percentage drive train power loss equates to 600BHP at the fly wheel
The great thing about this convertion is although I have the use of all that power the car is still driveable as an everyday car to go into town as well as a blast though the country side.
We are looking also into an other tweek so maybe the 500rwhp / 650BHP is on the cards.
Like Andre my car is a high mileage, engine had done 110,000 enthusiastic miles, the gearbox 150,000 miles
Andre fitted the Twin Screw Supercharger on my 4.0Lt XKR
470 rwhp using Jaguars percentage drive train power loss equates to 600BHP at the fly wheel
The great thing about this convertion is although I have the use of all that power the car is still driveable as an everyday car to go into town as well as a blast though the country side.
We are looking also into an other tweek so maybe the 500rwhp / 650BHP is on the cards.
Like Andre my car is a high mileage, engine had done 110,000 enthusiastic miles, the gearbox 150,000 miles
KingRichard said:
jag guru said:
Another ( more expensive ) option would be to replace the Roots
with a twin screw type (Sprintex) charger. These are more expensive
to manufacture than the Eaton, due to the complexity of machining the
helical lobed rotors. Which is probably why Jag fitted Eaton's in the
first place. The design guys will know if this is the case,though.
But they do have some advantages:
They run cooler.
They consume less power to drive.
They are a more compact installation.
They have a higher volumetric efficiency ( VE ) over a
comparable roots.
I,ve read they can be worth up to 40 bhp, though that would depend
on pulley size used, intercooling, etc. Might be worth looking into.
I can't believe you think it's not fast enough !
Well it's ok... But it's not what I expected. Kind of want it BRUTAL on kickdown in sport mode... and it just feels 'rapid'.with a twin screw type (Sprintex) charger. These are more expensive
to manufacture than the Eaton, due to the complexity of machining the
helical lobed rotors. Which is probably why Jag fitted Eaton's in the
first place. The design guys will know if this is the case,though.
But they do have some advantages:
They run cooler.
They consume less power to drive.
They are a more compact installation.
They have a higher volumetric efficiency ( VE ) over a
comparable roots.
I,ve read they can be worth up to 40 bhp, though that would depend
on pulley size used, intercooling, etc. Might be worth looking into.
I can't believe you think it's not fast enough !
I'm not moaning, but it does feel like it's holding back a lot
The Jag engine works no different to any other, so the same tuning principles apply.
First and easy mods are induction and exhaust. Jaguar have historically fitted very restrictive setups in both cases.
Fitting a LARGE cone filter cold air intake will work wonders. Not sure what's available off the shelf (might be worth looking at some US tuning shops and suppliers if nothing turns up here in the UK).
Then to the exhaust. Yo can still have good flow and low db levels. The stocker probably only manages low db. So a good exhaust from the headers back is well worth it. Also including some proper high flow cats.
The best way to get an exhaust is to get one made for the car. There are loads of shops that will custom make and fit a full stainless exhaust using mandrel bends.
For the XJR you basically need two exhausts, one per cylinder bank. So costing wise you should be around £500-600 at most, but maybe £300-400.
You'll also want a cross over (a join of the each exhaust bank). Either a H or an X crossover. You can buy these pre made if you want.
For the cats buy them from US Ebay. Look for Magnaflow 3" highfow ceramic cats. These are cheap and flow very well. No point paying stupid rip off prices people in the UK charge for high flow cats.
From here on you could go many tuning routes such as nitrous oxide or n/a improvements. But with the blower you might as well use that.
Improving the intercooling will help, but only if the stock setup is not very efficient. This will also help in the long run also.
Upping the boost will also make more. However the Eaton M112R is not the most efficient blower so it will top out and become very unefficient very rapidly if you get too greedy with the boost.
Again, best to check US tuners as they are far more likely to do this.
You'll probably need the ECU mapping to suit the new fuelling.
A different approach is the transmission.
Probably 3 area's to look at:
Final Drive
I'm not sure what the final drive ratio is, but by making it shorter you'll notice a lot more acceleration. The trade off will be higher cruising rpms. Dependant on what gear top speed is reached in, this might be affected, but it will probably increase it if anything.
Example, my Camaro runs VERY tall final drive ratio of 2.73:1 that means 2000rpm in top = 80mph. Swapping this to something like 3.73:1 would make it accelerate a lot quicker and run thru the gears faster.
I think this might be a US thing again, not sure where else you can get ring and pinion sets from.
Stall - torque converter
The torque converter is what transmits power from the engine to the gearbox.
Stock converters tend to stall at around 1200-1500rpm. This means when you accelerate hard or kick down the stall will flash a higher rpm momentarily, essentially allowing the input shaft of the gearbox to sping quicker than the output shaft. Basically means it puts the engine in a better rpm range while the wheel speed hasn't changed.
By swapping this to a higher stall, say 3500rpm it will transform how the car responds and may no longer need to kickdown to accelerate as hard.
People with higher stall torque converters seem to liken it to being shot out of a cannon.
If you want to read about them and speak to some guys that may help have a look here: http://www.converter.cc/
Shift points
I'm not up on the current tranny in the XJR. But as a rule if you can improve the shift and kickdown response it will give it a much more sporty feel. I'm not certain how this can be done, some can be mapped via the PCM, others need parts fitting. But this kind of mod is usually rewarding.
It might be worth some investigation into this.
Hi,
Some good info!
But why not just change to the twin-screw, it will give you more than 300 bhp/ton ;-)
I know of 1 tuner that has tried all the tricks in the book you also mention, from intake/exhaust/removed cats/tuned/faster spinning Eaton/ported Eaton and other parts/ bigger intercoolers and god knows what more and the most he ever got out of his 4.0 was something like 375 rwhp.
Now with a good twin-screw setup and just a modified intake you can easily get about 430-450 rwhp, and there is so much more to come if you would do more modifications, we are hoping for 500 rwhp soon.
Andre.
PS
No point imho in changing the final gear until you have also changed it to a LSD, there is just not enough grip otherwise (if you up the power), and even with a twin-screw and a LSD you will have traction issues. I was actually thinking going smaller ;-). Another negative effect of changing the final gear ratio is the negative effect on fuel consumption. For those that are interested Jaguar has a 3.51 diff it uses for the Mexican market.
Also be careful with sports catalysts, as there is a chance the ECU doesn’t like it (depending on year car you have), so you might also need to look into fooling the ECU there or find the right catalysts that will not cause an issue. Have just heard too many issues there, but maybe the older AJ26 cars are easier?
Any good Mercedes tuner (for the 4.0 R cars) will be able to change shift points, or even make quicker shifts possible, though you will lose some smoothness, which is why I haven’t done that. Try http://www.renntechmercedes.com/ for that.
Some good info!
But why not just change to the twin-screw, it will give you more than 300 bhp/ton ;-)
I know of 1 tuner that has tried all the tricks in the book you also mention, from intake/exhaust/removed cats/tuned/faster spinning Eaton/ported Eaton and other parts/ bigger intercoolers and god knows what more and the most he ever got out of his 4.0 was something like 375 rwhp.
Now with a good twin-screw setup and just a modified intake you can easily get about 430-450 rwhp, and there is so much more to come if you would do more modifications, we are hoping for 500 rwhp soon.
Andre.
PS
No point imho in changing the final gear until you have also changed it to a LSD, there is just not enough grip otherwise (if you up the power), and even with a twin-screw and a LSD you will have traction issues. I was actually thinking going smaller ;-). Another negative effect of changing the final gear ratio is the negative effect on fuel consumption. For those that are interested Jaguar has a 3.51 diff it uses for the Mexican market.
Also be careful with sports catalysts, as there is a chance the ECU doesn’t like it (depending on year car you have), so you might also need to look into fooling the ECU there or find the right catalysts that will not cause an issue. Have just heard too many issues there, but maybe the older AJ26 cars are easier?
Any good Mercedes tuner (for the 4.0 R cars) will be able to change shift points, or even make quicker shifts possible, though you will lose some smoothness, which is why I haven’t done that. Try http://www.renntechmercedes.com/ for that.
avos said:
Hi,
Some good info!
But why not just change to the twin-screw, it will give you more than 300 bhp/ton ;-)
I know of 1 tuner that has tried all the tricks in the book you also mention, from intake/exhaust/removed cats/tuned/faster spinning Eaton/ported Eaton and other parts/ bigger intercoolers and god knows what more and the most he ever got out of his 4.0 was something like 375 rwhp.
Now with a good twin-screw setup and just a modified intake you can easily get about 430-450 rwhp, and there is so much more to come if you would do more modifications, we are hoping for 500 rwhp soon.
Andre.
PS
No point imho in changing the final gear until you have also changed it to a LSD, there is just not enough grip otherwise (if you up the power), and even with a twin-screw and a LSD you will have traction issues. I was actually thinking going smaller ;-). Another negative effect of changing the final gear ratio is the negative effect on fuel consumption. For those that are interested Jaguar has a 3.51 diff it uses for the Mexican market.
Also be careful with sports catalysts, as there is a chance the ECU doesn’t like it (depending on year car you have), so you might also need to look into fooling the ECU there or find the right catalysts that will not cause an issue. Have just heard too many issues there, but maybe the older AJ26 cars are easier?
Any good Mercedes tuner (for the 4.0 R cars) will be able to change shift points, or even make quicker shifts possible, though you will lose some smoothness, which is why I haven’t done that. Try http://www.renntechmercedes.com/ for that.
Good info too Some good info!
But why not just change to the twin-screw, it will give you more than 300 bhp/ton ;-)
I know of 1 tuner that has tried all the tricks in the book you also mention, from intake/exhaust/removed cats/tuned/faster spinning Eaton/ported Eaton and other parts/ bigger intercoolers and god knows what more and the most he ever got out of his 4.0 was something like 375 rwhp.
Now with a good twin-screw setup and just a modified intake you can easily get about 430-450 rwhp, and there is so much more to come if you would do more modifications, we are hoping for 500 rwhp soon.
Andre.
PS
No point imho in changing the final gear until you have also changed it to a LSD, there is just not enough grip otherwise (if you up the power), and even with a twin-screw and a LSD you will have traction issues. I was actually thinking going smaller ;-). Another negative effect of changing the final gear ratio is the negative effect on fuel consumption. For those that are interested Jaguar has a 3.51 diff it uses for the Mexican market.
Also be careful with sports catalysts, as there is a chance the ECU doesn’t like it (depending on year car you have), so you might also need to look into fooling the ECU there or find the right catalysts that will not cause an issue. Have just heard too many issues there, but maybe the older AJ26 cars are easier?
Any good Mercedes tuner (for the 4.0 R cars) will be able to change shift points, or even make quicker shifts possible, though you will lose some smoothness, which is why I haven’t done that. Try http://www.renntechmercedes.com/ for that.
I agree twin screw is the way to go. I'm surprised only manage 375rwhp with the Eaton though. The Mustang Cobra guys also running the Eaton M112R seem to get a fair amount more, although I admit the Ford mod V8 is 4.6 litres.
But yeah twin screw all the way. What blower are you planning on fitting??
Also good info on the final drive, if it's already 3.51:1 then probably no need to change it.
Do you know if the UK cars are this??
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