I finally got my car back together and I wanted to do a quick review of the Eurotoys Lower Pulley. I did an extensive post on the installation here:

https://www.jaguarforums.com/forum/x...-guide-229392/

As I mentioned in that post it did take a couple of months to get the pulley from Eurotoys so that is a consideration. I also decided to obtain a rebuilt supercharger snout and, since the supercharger would be off for that, to take care of the valley hoses, water pump, and thermostat. I also added the uprated Bosch supercharger coolant pump.

I ended up ordering a couple of incorrect gaskets and that delayed me from getting the car finished as quickly as I would have liked. Otherwise, using the resources found here as well as the factory service manual, the entire process was fairly easy (but time consuming).

After installing the lower pulley I would have to say that it has to be one of the best "bang for your buck" modifications that you can do. The car is definitely faster and it is definitely more responsive....especially in the upper rpm range...where the 4.0 really gets going.

The only potential negative for some that I can see is that supercharger whine is much more pronounced. I happen to like that sound so it doesn't bother me at all but it is pronounced so if you are thinking about doing this, you should take it into consideration.

I did consider doing the supercharger pulley itself instead of the lower pulley. However, to get enough boost where it would make a huge difference in the feel of the car, I would have had to machine the snout. Ultimately, my thinking on that was "why do that when you can just install the lower pulley?"

Based on multiple posts on this board that cited diminishing returns, I decided to NOT do a performance pulley on the supercharger (in addition to the lower pulley). I think that was the right decision since the lower pulley gave me the performance boost I was looking for.

So, the bottom line on the Eurotoys lower pulley is that it is a quality product and if you don't mind waiting for it and if you don't mind supercharger whine, it is a mod that makes a definite difference in the performance of the supercharged 4.0.

 

Good you decided to stay at only bigger lower pulley because, with also the upper pulley changed for smaller, no doubt you would get even more torque but it would be short lived. The intake air temperature would go too high quickly and the ECU would start cutting the supercharger out.

With your current pulley upgrade, you may be fine but, if you notice supercharger cut-outs (in hot weather or repeated hard acceleration), you may consider installing an uprated (thicker) charge cooler radiator. I have installed a smaller supercharger pulley (6% only), uprated Bosh pump and an uprated charge cooler radiator and still, when I once tried repeated hard acceleration, I did get brief supercharger cut-out. But it was a fairly extreme case, a bit of spirited driving. Otherwise, the mod works great.

 

Thanks for the install how to, and review! Was a PCM retune needed? So it pulls better a highway speeds than stock? If you can get vids of a pull and whine, that'd be great

 

With only changing the upper pulley by a 6% smaller one, no retune is required. Also, no machining of the snout is needed and the stock belt can still be used. The acceleration through the mid revs is noticeably better. As for the power gain at high revs (towards the red line), I can't tell as I have not gone into that area. From what I have read, the top end power gain with the stock supercharger is minimal with larger bottom or smaller top pulleys because the supercharger, as it is spinning faster, will enter into lower efficiency area at high engine rpm so it will not provide much increased power. These mods are more for the mid rpm range torque gain.

So, there are two limiting factors - the supercharger's efficiency drop at the increased rotational speed (over it's upper efficiency limit) and the air cooling capacity of the charge cooler system.

My car is a Daimler Super V8 which has good sound insulation (including a foam pad under the supercharger) so I do not really hear the supercharger whine (before or after the 6% upper pulley). Also, my supercharger has the original spring loaded coupling and this is probably why it runs rather quiet. As I understand, solid couplings cause significantly increased supercharger sound/whine.

 

The ECU on the 4.0 cars is able to adjust and re-learn with the higher boost. In fact, I don't think anyone is offering tunes on this engine anymore. I remember reading a thread on that topic somewhere on the board.

You can definitely feel the higher boost @ highway speeds. Like I said, it is stronger throughout the RPM range but the 4.0 really likes the higher RPM's so you definitely feel the boost when passing, etc.

There is a video floating around on this board somewhere of someone who had an aftermarket pulley but if I have time I will do one myself.

 

I installed an Eurotoys larger lower pulley, slightly smaller upper pulley and sent the ECU to them as well for a reflash. This was on a 02’ XJR 100 with 32K miles about 5 years ago. The downfall of it all was the heads lifted under full boost and there was a smokescreen. I pulled the heads off and had installed ARP head studs. There’s photos of it somewhere on here. If you have metal head gaskets, you’ll possibly (?) be ok not to blow them out. If you have the non metal head gaskets, you’ll most likely have to plan on pulling the heads and upgrading those in your future.

 

I just read your other post about it being an 03’ so your good on the gaskets. It is remarkable how much different it feels. Enjoy! 😀

 

Crap, I have an 02 xjr 100 as well. Not trying to pull the heads this soon😂 Guess I'll keep the boost down

 

I could not find ARP studs for Jaguar AJ26/AJ27 engines. Where did you get yours? Are they perhaps made for some other engine but fit Jaguar's engine?

 

When I got the heads off, I had to do all sorts of measurements. ARP has a measurement sheet on their website that you print out, measure as stated, then email a scan of the filled out sheet in return. They then fill the order of what they know you’ll need. They were every bit of $500 about 5 years ago so keep that in mind. I’ll see if I can find the link of the head stud post.

 

It’s buried somewhere but I couldn’t find it so I’ll post them here.

 

Thanks for the info. I know that ARP studs/bolts are not cheap (have installed them on a few of my other cars) but they are still worth the money. Looking at the ARP website, it seems that you need to contact them first through their general contact form (couldn't see option to directly place order for custom made studs).

When I was rebuilding my Jag 4.0 SC engine a couple of years ago, I bought new genuine Jag head bolts (as I could not find ready made ARP kit) but was disappointed with their quality of fabrication. More than half of the 25 bolts I bought (included some spare) were quite a lot out of straight. Some so much that they would rub hard against the hole walls when I tried to install them. After my complaint to the supplier, they sent me another set of 20 f.o.c. Then I managed to put together a set of "not too bad" 20, out of 45, by checking their straightness on a lathe.

It appears that Jaguar currently has a batch of head bolts that are out of straight. Perhaps that is why the price was reduced from GBP 8.20 to just GBP 3.60. I will consider replacing them with ARP, which can be done one-by-one, without removing the heads.