intakes*** auto correct

 

i like the term,"internet racers".says a lot.

OP asked who has actually made 500hp from a JagV12?

maybe next year we may find out!!

 

Notice that Mike has made several references to Allan Scott's book in this thread. I've known Mike for several years on the J-L forum, and we have corresponded countless times. He's extremely knowledgeable about the XJS, and he has been a great help to me with my JagZilla project through the years. Believe me, when he feels strongly enough about a source to make reference to it, it's because that source is both reliable and accurate. Just another reason everyone reading this thread, and interested in getting the most performance out of your XJS should take advantage of the forum discount we have on Allan's book, and get it into your Jaguar library, if you don't already own it.

 

Calvin,
Check the last few posts in the thread titled "Possible Group Buy: New XJS Book". I arranged for a slight discount for all of us on this forum, straight from Allan Scott himself, and if you want him to sign it, and write a personal message in it, he will be happy to do so at no extra charge. He's a great guy, and my copy is already on it's way to me.

 

I bought Allan's book yesterday for $64US off eBay so lets see where this takes me.

Internet racing has its place for me anyway, do the research and formulate a plan before I commence modifying my spare engine.

 

Ronbros: internet racer: great term! I suppose I fall into this, like most here, one time or another. This is part of the attraction: talk on what can be, might be, may never be. Almost always entertaining.

On the TWR book: Allan Scott was the guy who was responsible for engine development for TWR during the Group A onslaught. When I first read this book, I thought, hey, where are the details? Then I read it again, more slowly and there they were.

Cam work consumed much time, getting valve springs and related hardware that would hold up under 7000-8000 rpm took time. MUCH time on oiling and keeping the oil (and engine) cool. Another interesting tidbit: It is pretty much accepted that the V12 bottom end is overdesigned and pretty much bullet proof. However, TWR found that extended race time in the upper RPM region left them with motors with broken main bearing caps, on a regular basis. They couldn't sub out a strong material because of Group A regs.

Those interested in the cam details should read this book carefully, as the timing specs and related information is there, it's just threaded into the text here and there.

As for me, I am really interested to read about the Group C motors, a subject for another Allan Scott book that evidently will be forthcoming.

What I like about this book is that it details what worked, and what didn't. Most of this stuff never reaches the rest of us because racers are very closed-mouthed while they're racing, and the details languish and disappear with time after the cars are no longer competitive or some other well turned ankle grabs our attention. Scott is coming on the scene now with details that are safe to disclose, as no one is interested in the Jag v12 any more. Just us. And that's fine, because I really enjoyed seeing those details.

 

I got pretty interested in this thread when it turned to the topic of twin turbocharging. I've wanted to do it for a very long time, but, I've always heard that you have to run big boost numbers to make power, which requires moderately low compression and forged internals. Yet someone here is of the mind that the stock HE could run twin turbos with an aftermarket engine management system.

Well, I have the right engine management system, An Electromotive TEC1 (refer to the specs in my signature). JagZilla is still in the project stage, and it wouldn't be inconceivable to plumb it for turbos at this point. As it sits, the motor in the car was dynoed at 390HP on GTJ's engine dyno (according to the previous owner of this motor). My first two initial questions are:

1. How much (or how little) boost could I reliably run with the cast pistons? The PO told me when I bought the motor that Gran Turismo Jaguar installed what he said they referred to as "proper" 10:1 pistons (neither of us is sure why GTJ thought of 10:1 as "proper" pistons) when they built the motor for him. I'm conservatively guessing that they are cast, rather than forged.

2. How much HP will that amount of boost net me?

I simply can't justify the expense and trouble involved for only another 50 or so ponies, and I don't want to crack this motor open, and pour in thousands more dollars.

***EDIT*** I had originally misquoted the HP of this motor, and had to dig through my old emails with the PO to find the correct figures, which I have now changed in the above text.

 

Calvin:

I forgot to respond to your question on TWR and the intakes. Here's what they did, in summary: 1) they reprofiled the internals (no details on exactly what), and eventually, cast new manifolds so that they could accomplish what they wanted internally. Externally, these appear OEM, but I would bet side by side an OEM set you'd pick up subtle differences. They were evidently good enough exterior matches that the Group A scruiteniers passed them. The manifolds were insulated from the cam covers- evidently the oil temps radiated a lot of heat into the intake manifolds, so they used heat shields. The throttle bodies were radius'd on both sides (they could not change the throttle diameter). Then, they used an elbow connected to a hose that ran to the rear of the headlights to get cold air into the engine. The elbow could be concealed in the air boxes. This headlight route caused trouble on a race in which a car hit another, breaking the headlights, and glass got ingested into the engine. That event caused a redesign.

Whatever they did to the intake internals, though, resulted in a motor that rev'd pretty freely in comparison to earlier efforts. Looking at the HP curves, it actually underperforms just a tad, but comes into its own >6000 RPM, and from there, it's a solid performer. The HP curves showing A-B comparisons demonstrate this convincingly.

Anyway, some of the details.

 

these must be the same manifolds that bob tilley sells, since he has cast reproductions

 

The Tilley manifolds may be the same, but I am not sure- the reason is that the ports on this look round, and the pictures I've seen of the Group A heads and manifold interface show an elongated, 'D' style port. There is also something called a 'reverse ratchet' or some sort, and I have NEVER been able to understand what those are.

I would guess that much of the Group44 stuff has its origins, evidently, in the TWR bits. I am not completely convinced on that point, but, TWR would be the home team for Jaguar, as it were, no matter how good Jaguar's relationship with Group44. Wouldn't you think?

If you get hold of a set of those, please take detailed pictures and post them!

 

Turbos vs superchargers: The two big questions I have been wrestling with are space and temperature, the latter being worse for the lack of the former. My intention is to keep the car looking bog standard from the outside. Target HP is 450. Driveability as for NA.

Space: Fitting all the pipework for twin turbos without virtually rebuilding the inner structure, anybody got that beaten? For the twin screw superchargers my thinking has been to put one where the air injection pump will be and the other where the power steering pump is. The power steering I intend to convert to electric assistance.

Temperature: With twin screw superchargers the heat generated is pretty much minimum when we are talking about forced induction. turbos are at the other end of the scale.

BTW, Alan Scotts book is a great read whether you look at it from the tech, the racing or the project management perspective. I enjoyed them all.

 

My preference would be a single Whipple, this is not going to happen, there is simply not enough room to fit in down the side of the engine, and it will not fit in the V. The manifolds could be removed and new ones fabed like the TPI 350 with a single center TB at the front. I think then the single whipple might fit down the LH side.

A single SFSC would fit down the side if the PS pump was relocated. This would be the easiest of all to accomplish 9:1 cr and low boost

Dual superchargers have been done many times on the XJS one with twin whipples and the Listers with twin Albrex SFSC.

After a good crawl over Bruce's TT XJS I think this is easier than PDSC, as for the heat just wrap everything in the TT/exhaust area in thermal insulation. If the CR is left higher than about 9:1 with low boost and dual W2A intercoolers directly off the TB's. I think this would be a good streetable engine it would still have good bottom end and midrange and if the turbos were sized correctly to provide boost to 6000rpm better topend than currently.

 

But considering the temps under the bonnet and the (at least theoretically) higher heat (into the compressed air) from the SFSC compared to TSSC, is it worthwhile going for the TS? I have picked the brains of a drag racing aquintance, but his experience is not directly transferable to a street machine with limited under bonnet circulation.

 

SFSC has about the lowest thermal transfer to the intake and are repetitively cheap. Their main drawback is the linear boost. They are configured to provide max boost at peak RPM and the boost curve is linear across the rpm range ie 10psi at 6000rpm 5psi at 3000rpm.

TS SC are far more efficient at producing power through the entire rev range than Eaton or SF SC. TS are by far the best of the SC's, they are also the most expensive.

 

Warrjon: who is this "Bruce" with the TT XJS? I'd love to read on this, and see pix. I have been collecting pix of several TT installations, to see how differently this is done.

Also: anyone consider mounting the turbos in the rear, maybe where the middle silencers are located, or in the spaces for the rear silencers? I have been corresponding with a guy in South Africa who is working that approach. My main problems with it are a) oiling the turbos, b) space for running the intake pipe forward, and up through to the manifolds, and most of all c) lag concerns.

-M

 

The floor pan stems from the original XJ6. The story goes that they forgot all about the exhaust pipes and so they were crammed into the tunnel .....

It is in fact very cramped and the ground clearance does not encourage any sizable pipes going forward.

 

In the web shops I have checket over the past year or so they have been pretty close in price. Am I missing something?

 

There is a link on the previous page post #63

 

mike grp 44 was three or four years before TWR got into the V12 jag engine.

pix of book(read date May 1977) specs from book(sorry upside down).

TWR got into XJS around 1983-84!

also pic of Grp44 car 1985, TWR got into Grp c around 1986.

 

for what its worth, the factory pre heads could not make power much beyond 500-550hp, with many modifications done to them.

SO Tullius went to California to a top performance engine designer, around 1982- 1984, with a modified pre head, said what can be done.

guy made drawing and blueprints for heads. bob took them to UK, and they said they would be made in UK,NOT USA. bob not happy,but jags handing out the money,ITS ALWAYS ABOUT THE MONEY.






guy designed the(most sought after heads today) the raised port along with D shapes, and other mods, Bob had them cast in Cali. and machined by the designer, a few sets were made, when Jag found out , they were given to TWR and he had some race head company make some improments,.

this is from interview Bob Tullius just this year, he still lives in Florida US.