Hi everybody. This is my first post on forum. I have tgo thank the commiunity with its post, that have helped me in a lot of situacion Well, i have by 3 years, an X350 XJ Super v8. I think that this is the most beautiful saloon, also 20 years later.. I've the bad habit of always wanting the best for my cars. After 2 years of research, my attencion stopped of a Twin Screw kit by Avos. Damn, that kit is insane! At this point, my question is easy: someone have an 2.6 H, TB and Pro M maf whit settings for X350 or STR 4.2 litre, also used, for sale, in Europe? I'm sincere, i don't have any idea of ​​the price of that kit (and installation, and upgrades at other components). So, i'm not sure that I'll accept the possible propostal, if i doesn't have enought money. Honestly, I don't think that someone have one kit for sale, 5 years later the end of the production by Andre But trying is the only possibility. I have another question: after installing the kit, the engine, the gearbox (ZF 6HP26) and the LSD need of heavy upgrades? Thanks to all!

 

Well you do mention the LSD but the problem is your car does not have one! Yes for a SC car to come from the factory without an LSD seems odd and it is. Jaguar fixed that when they released the newer X351 XJ and we got the wonderful E-Diff. We had some rumor that Jaguar was not allowed by Ford to provide LSD at that time because that was reserved for Aston-Martin which Ford also owned at the time. They no longer own either company and things have progressed from there.

Now if you want to add an LSD you can buy one but it's expensive and not many have done it. As you can see it's over 2000 GBP and that's NOT counting installation costs!
LSD for XJ

I would give up on the twin screw. Avos worked long and hard on that and I helped him a bit when he put a kit together for the STR by measuring stuff under the hood for him. But in the end even I decided it was just too much cost for an old S Type R.
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Thx for a reply. Yes, i'm aware that we have only a open differential on old SC Jaguar. But, for me, isn't a problem. For two reasons. First, the LSD is useful only for drag race or to drive the car into a kart track. Second, I saw that, on paramount performance site, is for sale a specific LSD to my car. In future, if I wanna buy it, I know where. I say that I'm not sure if the stock differential is enought strong for a Twin Screw. Can you tell me the old price of Twin Screw kit? Someone say that the new kit is around 6k €. The real problem is that, whit a Eaton and all mod like caldoofy intake, special exaust ecc., I can't pass the 450 HP at flywheel. I must open the engine, add a NOS and other. But I have other worry: for me, the gearbox (6HP26) can't support other 470-480 HP. The Mercedes gearbox of 4.0 litre is too much strong. And my gearbox have 240k kilometers... What do you think?

 

Well the biggest mistake Jaguar/Ford made with the STR was the lack of a LSD. The car stock was almost 400 ft-lb of torque and on any take off around a corner just apply the slightest bit of gas and you light up the inner wheel with little to no effort. You really can't use what the STR had stock without a LSD and added any HP will just make it worse. Don't even talk about when it's wet out! My poor ole STR has just about useless with all that power and no way to put it to the pavement in the rain!

My 2014 XJR with the E-Diff is completely different car and can put down massive power because it spreads out the slip between the two rear tires. It is 100% needed on the street and if you drive cars with and without LSD it will be obvious!

If you can afford the Paramount unit get it. It is a quality unit and there have been no complaints. Of course they have only sold a handful so not a lot of real world experience. AVOS was claiming 700HP and had no transmission or rear end problems. But at that level it would depend on how hard you are pushing the car. Like multiple track events or drag racing as those are really hard on a car if done consistently.
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Yes, I have an X350 R, that is lighter than STR, and takes a little, as you said, to speen the wheel. It happened to me in a roundabout, at only 3000 rpm. And, actually, I'm considering that purchase. But I live in Italy, so, excluding the price and the installation, the shipping cost too. Do you think necessary to spend 3k to have LSD on the car? I wanna have no more than 550 hp, just to beat an actual sports sedan. But whit Eaton it's a losing battle. What mods do you recommend to get close to that power without TS?

 

Your right where I was some years ago?

As you said it's $3k for the LSD plus the cost of mods to get to 550HP. In the beginning we thought there was a way to get a much cheaper LSD.
Here is my very old thread (Started 10 years ago!) on adding the LSD using more common Ford parts. Note we never did it all worked out and that thread finally dies out after 404 posts!

S-Type LSD

Here is a long thread from Avos that also has a lot of good info. Mainly about the Quaife QDF3W which would fit your car too?

Another LSD Thread

Now 550HP which IS pretty high for the 4.2L engine will require a pile of money too. I was talking to Avos a lot as his car was pretty amazing at a claimed 700HP! But the TS kit was in the $5K-$7K range when it was available but I don't think anyone purchased any kits? And Avos stopped producing them because of lack of demand?
Then the big problem is all that money in a car that just is not worth much if anything on the used car market.

I decided the STR was a very good car as is and with all that cost to get where you and I wanted to go. I finally sold my 2005 STR and purchased a 2014 XJR that came stock with close to 550HP. BUT that was also an expensive upgrade too!!

So I can't really say for you. For me it just got too expensive to do all those things.

550HP is high so maybe stuff like NOS or Meth injection? With the Eaton blower Meth injection would be a great addition and that would allow you to add pullies for more boost since you could control the heat soak with Meth. Again you would need to build this as no kits are out there?

Next problem is the tune and I don't know where to turn for that? The cars are getting older with not much demand so tuners are just not interested.
I like you project a lot but want it to be a success for you.
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Thank you very much for these tips and links, I'm sure they will be decsive for what I will do in the future! I must explain why I wanna have an TS. For the only reason that is the best mod to value for money. I say that, whit only 7k, there is only mod that give you 600 hp like that. But 7k are too much for me. For thats Avos has written, he interrupted the productons whitout a precise reasons. But I thnk that the interruption was for other reasons. I can't use meth in my car, becouse here in Ita, that has an big cost, there are not resellers, and take away the "originality" at car. Do you know why? Because I must register my cat in a "Historical Interest Veicle".Whitout that certificacion, i have to pay 1600 € per year in taxes. Yes, after 20 years and whit "only" 400 horse. Italy is the worst place to have powerful cars. And if they see modificacions of any kind, they don't give me it. Okay, also TS would made it, but, they can't see it For this i prefer go whitout an externals-engine modifications. And a lot of member say that's impossible whit a M112. Or maybe, opening the engine, but is still a problem. Hope I have explained. I search power, but whit an "originally spirit" of the car. Now i value to see (and buy if is possible) the QDF3W

 

I do find that Italy not being friendly to powerful cars a bit funny as Italy is basically where ALL the high performance cars come from?
I mean Ferrari is the top of the heap and they are born and bred Italian?

Post back with what you do as we all want to see it too.
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Yes, is so funny for these reason. Certainly, i've alredy done some mods at stock intake system, but i'm not sure that's will be interesting at member.