I thought I would share my experiences so far regarding my 2001 XKR supercharger pulley upgrade. As many of you know the 4.0 and 4.2 L supercharged XKRs use a Jaguar specific Eaton M112 supercharger. AFAIK, there are three pulley change approaches to getting the supercharger to spin faster.

1) +1.5 PSI supercharger pulley upgrade, available from Mina, Eurotoys, Paramount and others

2) +3 PSI supecharger pulley upgrade available from Eurotoys, Phoenix Coachworks, and others

3) +3 to 4.5 PSI Crankshaft pulley upgrade available from Eurotoys, Phoenix Coachworks, Paramount Performance and others

Note that it is possible to use approach 1 and 3 or approach 2 and 3 in combination, but the heat generated will almost certainly require a better than stock intercooling solution.

Approach 1 is the least expensive in terms of parts and labor. Basically it requires just pulling or cutting the old pulley off, and pressing on the new one. (On an XKR, this also means draining the coolant and removing the aluminum pipes and thermostat housing that is over the top of the supercharger snout). A special tool for this can be rented or purchased. These pulleys are pressed on extremely tightly, and an ordinary 3 jaw puller will likely not work and may damage your supercharger. Gain is reportedly around 15 bhp. In my opinion, probably not worth the trouble. Also the same supercharger belt can be used.

Approach 2 is roughly the same in terms of parts (although some outfits charge more for this one), but requires significantly more labor in terms of modifying the supercharger snout. The +3 PSI pulley is about 2.6 inches in diameter, and this is just too small to fit over the supercharger snout. Once the old pulley is removed, it is necessary to grind down the snout diameter by about 4-5mm. Supposedly, the snout casting is still strong enough after this mod. Another potential disadvantage is that such a small pulley is more prone to belt slippage, but according to marketing and anectdotal sources, a steel pulley will be less prone to slippage than an aluminum one, and a Goodyear Gatorback belt is less prone to slippage than other brands (although the stock belt size still can be used). Gain is reportedly around 30 bhp.

Approach 3 is the most costly, but requires no modification to the supercharger itself. The crank pulley and damper assembly is removed using a puller, and typically sent off to have a machine shop add an outer, larger diameter pulley. (Some vendors offer a range of sizes for this outer ring, which may be user changed once the original damper is reworked). The new unit is then reinstalled. Normally a larger belt is required. Gain can be up to around 45 bhp, depending on the ring size.

In all cases, the larger the gain, the more you will need additional charge air cooling to receive maximum benefit. There are also diminishing returns, because the M112 is already being run at or near its maximum efficiency in the stock configuration.

For my car, I chose approach 2, the +3 PSI, 2.6" pulley from Phoenix Coachworks in the UK (http://www.phoenix-coachworks.co.uk/superchargers.html). They are currently selling at auction on ebay (http://cgi.ebay.com/Jaguar-XKR-XJR-S...item1e5fe5c1f0) for around $200. This appears to be one of the better values out there. It is a high quality, steel pulley, and comes with a nylon dummy pulley with a window cut out to help you gauge your progress when grinding the snout.
Rather than use the pulley cut off method for removal and heat up method for installation as described on the Phoenix web site, I chose to purchase a puller/installer tool from Eurotoys (http://eurotoysltd.com/catalog/produ...roducts_id=636), which at $110 was one of the less expensive ones.

Removal of the old pulley went flawlessly. However, the next step, grinding the snout, was tedious work. I used a belt sander, and about six 36 grit extra course belts, plus a medium grit and a fine grit for final smoothing. I found that this job would be easier if the entire supercharger is removed first. The problem with doing it on the car is limited access with the belt sander, and all the abrasive grit that gets all over your car, even with a drop cloth under the snout. It turned out that I roughed it in with the belt sander, and then did the final trimming by hand sanding about a 90 degree arc at a time on the supercharger snout. It was tedious, and I did about an hour a day over 5 evenings.

Unfortunately the nylon dummy pulley gauge , though a good idea, was just a tad too large, and when I installed the new pulley there was a very slight binding spot. I went to pull it off and had a serious 'oh s---' moment...the puller was too big for the reduced size pulley. After calming down, I fashioned an 'adapter' of sorts for the puller from some 1/8" hardened steel strips I had lying around from another tool. It worked and I got the new pulley off, then worked on grinding for another hour or so and re-installed the new pulley. I cleaned up the engine compartment with a vacuum and then with compressed air. If you do it on the car, it is imperative that you use fender protectors..the airborne grit will otherwise settle on the car and rub between your legs and the car and scratch the finish. It can be polished out, but its best to avoid in the first place as much as possible. When you are done, wash the car vigorously with a hose, to get off any grit without rubbing it in. Also, be sure to plug up any open hoses and coolant orifices with rags. I also found a pair of inexpensive calipers was invaluable for judging the correct diameter of the snout (target diameter is 54 mm).

Once the pulley was installed , I replaced my thermostat with the Eurotoys 170 degree (13 degrees cooler) version. I reinstalled the aluminum pipe /thermostat housing assembly using new seals (two required of Jaguar P/N C2C11477). I also replace the bearing on my supercharger idler pulley, because mine had excessive play and some noise. Finally, I chose to replace my supercharger belt with a Goodyear Gatorback belt (see https://www.jaguarforums.com/forum/s...ight=gatorback for Gatorback details).

Once all back together, with fresh coolant, I reset the ECU.

It has been 2 days now, and so far I am quite pleased. The 170 degree thermostat is causing no issues. It seems as if the performance continues to improve as the ECU re-adapts. These cars, though fantastic at accelerating at the higher revs, are geared such that they are a little slow getting going from a standstill. The 3 lb pulley really improves performance significantly in that regard.

I hope to make some intercooling improvements in the future (it gets awful hot here in the summer)and perhaps add a thermostatic or manual auxiliary fan switch in the not too distant future. Then I will get some dyno numbers.

 

Interesting topic and a great writeup! Thanks for taking the time!

 

I am so glad you are on this forum. I'm just going to follow in your footsteps in time. You might have purchased a cheap Harbor Frieght pnuematic die grinder and those 2-3" 36 grit discs. So Avos with the twin screw TVS SC said as you did,that the Eaton was already at 100% efficiency so how can spinning it faster gain 30-40hp? I am most interested in the final result, but if you already feel more power than I guess with a new cooler it will be a big gain? LET US ALL KNOW.

I'm still getting everything up to par. New alternator on the way, mine was making noise. All pulley bearings will be renewed except the SC bearing at that point. Next for me will be buying all new rubber hoses to have them on the shelf (they are so unique and won't get any cheaper). After my oil cooler Hi Pres hose blew i'm gonna replace the other 3 pcs. Then Poly upper bushings, Mina exhaust, Nameless Perf Cats...I'm pretty far behind where you are but I'll get there. EVERYTHING WORKING OK except broke flimsy Bleed Hose fitting on Crossover pipe..new one on the way. They changed design on your car..hose goes over nipple..mine plugs into it!

 

How much shorter than stock are the Gator belts? I have both pulleys done and there is a lot of slippage with the belt supplied.

To get over it I sleeved my idler pulley, but it would be good to know if there is a better belt available.

 

Obviously the most nerve-wracking aspect of this would be grinding the snout of the supercharger, thus eliminating the possibility of returning to stock. I am not all that knowledgeable about the pieces and mechanics of the supercharger but why don't these pulley manufacturers also provide appropriate replacement "snouts"? Of is it that the snout piece is impossible or difficult to swap?

Doug

 

@Doug
New (replacement) snout = more work, as SC needs to be taken out = more work for seller (core charge etc) = more expensive = less sales (my guess). If you want to change to this ratio then I would think it is safer to choose a larger (little more expensive) lower pulley. Less chance of issues, as the snout has to take a lot of force, and vibrations over time might fatige the material.

@XKRacer
Not sure what pulley sizes you are reffering to, but when I go lower than 2.75" I use a K080510 belt (from Gates).

@WhiteXKR,
Hasn't Phoenix Coachworks been able to provide before and after dynos?

 

I might have to get my hands on a Gates belt, they do sound quite a bit shorter though (2.5") are they harder to get on?

Removing the snout is actually very simple once you have the supercharger removed........throttle body.......water pipes.....elbow....hmmmmm OK scratch that

 

AVOS--so are you saying that, in the end, replacing the lower pulley rather than the upper one is easier? Would that be more of a pull-off/press-on operation? It occurred to me that the slickest solution would be for someone to develop an "over-ring" that can be slipped over the lower pulley to, in effect, increase the diameter. Probably no such thing exists and it would probably slip too much to work. Doug

 

Lower pulley is far simpler, all you need is the correct puller for the lower pulley which is held on with a split tapered collar, once it releases, no probs.

 

@Doug, as XKRacer says I also think it will be easierwith the right pulley puller of course. Biggest advantage is that you do not have a weakened snout.

@XKRacer,
And that doesn't even include the EGR...
The pulleys I have are a little bit different in that the side lips are smaller then the eaton ones. That makes it easier to put on the belt if it is tight.

 

Quote:

Originally Posted by Fla Steve

Thanks for "Paving the Way"

Fla Steve - Thanks for the feedback ! The way was really paved from other other folks in this forum (and some years back on other forums), including members on the S-Type and XJR groups. Also, in particular Avos has helped me keep a level head as to the limits of the Eaton. I enjoy sharing my experiences with people who are realy interested and will definitely continue to.

You are right, in retrospect, a die grinder probably would have been a better tool, giving esier access in the limited space, although my belt sander model had a 'window'to allow sanding on a couple of inches of the top of the belt, which helped access.

The Eaton is not at 100% efficiency in stock form, it just makes the most power in relation to the power lost to drive power and air heating in the stock configuration. Avos explains this really well in post number 8 of this thread: https://www.jaguarforums.com/forum/s...ight=snakebite. Also, remember, you are not running full throttle most of the time (at least I am not ), so you are getting extra boost at lower RPMs with the smaller pulley and not running the Eaton at such high losses.

Regarding the crossover bleed pipe, I have the same crappy one in my early build 2001, which also broke when I removed it. The inside of the nipple is rusty, I was afraid the stock replacement may not seal well, so I cobled together a repalcement with some heater hoses and fittings from home depot.

 

I only had the upper pulley, so I used the same size as stock [Goodyear Gatorback 4080515 for the 4.0, 4.2 is different]. Still plenty of tension, but the wear reading indicator obviously is no longer valid. All the Gatorback sizes are here: http://www.goodyearep.com/productsdetail.aspx?id=3128

True, the lower pulley has its advantages for sure...but it is at least twice as costly (assuming you do the snout work on the upper pulley yourself) and you need to ship your damper out for machining. I am considering both upper and lower once I improve the intercooling.

I probably should request it. Doesn't matter that much to me though, I am more interested in the dyno on my car with my set of mods. I still think it is a pretty good bang for the buck mod...and I know it will still never be close to a TS.

Nerve-wracking? Thats why I called this thread an 'adventure'. BTW, no reason the old pulley cannot be refitted to return to stock, it will just have a little extra clearance. But yes, you sure can damage the supercharger if this is not done with care.

 

What size on the Goodyear belt did you guys use?

 

Goodyear Gatorback 4080515. I am not certain if your '98 XJR is the same.

 

It seems to me that if it was that easy to get more performance without more issues, Jag would have done it already.
What are the downsides of doing this?
What happens to your fuel efficiency? What does it do to your engine & supercharger lifespan?

 

The work that Avos has done with even more powerful twin-screw superchargers over the last several years has pretty well proven that the engines and transmissions in these cars are designed with considerable headroom to tolerate higher hp and torque as long as they are well maintained. Likewise the ECU and fuel systems can accomodate the changes without issue.

Turning the supercharger faster may slightly accererate wear, but if you add supercharger oil changes to the mainteneance schedule every 30K-50K that may help.

Thinning the snout of the supercharger could be a concern, and if it is you could always go with the larger lower pulley instead of the smaller upper.

Fuel mileage might be impacted very slightly, but your driving style will impact it more. Supercharger boost only kicks in at higher RPMs, so gentle driving will result in no mlleage change to speak of. Of course if you use the boost heavily, you will pay in fuel.

The biggest issue is heat. The Eaton supercharger runs hot and runs near its point of maximum efficiency. Though you get more boost by turning it faster, that is quickly negated by added heat in the air charge. So without improvements to the intercooler system, your gains are diminished with repeated use without giving the system adequate cool down time between applications of boost. This is even true of the factory boost levels, but is excerbated when you increase boost further with a pulley swap.

Bottom line is the pulley swap gives you a little extra power that you can definitely feel, at a minimum cost and risk, but heavy use of the extra boost will lead to diminishing returns. Also, if are trying to extract max. power, careful attention to maintenance should also be at the top of your list.

Those looking for maximum power should consider Avos' twin screw configuration which provides far greater boost with far less heat generation.

 

Great review and write up! Have you noticed an incremental improvement the days following the initial install as the ECU adapted more to the modifications?

 

Not particularly noticable. What is noticable is that the car, as it is designed to, adapts to a moderate or aggressive driving style independent of the mod.

 

what boost do you actually get? in psi i mean

 

https://www.jaguarforums.com/forum/x...-pulley-86808/