Just ran across this. Gonna drop the builder a line and see if he'd care to join us over here. Pretty ambitious!

pcmhacking.net - View topic - XJS V12 twin turbo

 

I hate to be a prophet of doom, but...

That would be a great project if not for the fact that he's going to ruin that motor the first time he puts his foot in it for any length of time. He's going to be very disappointed when he tries to run anything over about 6 pounds of boost, because, he obviously has not lowered the compression, nor even bothered to clean what looks to be a very poorly maintained, high mileage motor. I wonder if he even knows that the stock CR is 11.5:1.

If done correctly (nothing more than maybe 9.5:1 CR), his approach of using 4 small turbos would likely be a better way to go on the V12, than 2 larger turbos. However, I would run one turbo per every 3 cylinders, instead of having one turbo feed the other, as he appears to be doing. By compressing already compressed air, he's definitely planning to run some serious boot with this setup (and did I mention that a stock V12 will never take that kind of pressure?). He's also going to multiply the heat under the hood by a factor of at least 10, and will need a massive water to air intercooler (or two) to handle the heat of that charged intake air. Also, that exhaust manifold he welded up looks far too small and restrictive to be effective.

 

he said he is using 6.0L pistons in a 5.3 to lower the compression ratio. i don't know if that will actually do that or not though. i don't know a lot about the v-12's

it also looks like he has too different motors he is working with a old crusty one in the car and another one on a bench that looks a lot cleaner. might just be using the old crusty one in the car to mock up the manifolds.

i would be a bit concerned about the manifolds. the welds look a bit buggered i would be a bit worried about how much weld splatter is inside the pipes. would be a pretty cool build if he pulls it off.

using one turbo to spin another isn't that uncommon of a setup. a lot of twin turbo setups are done like that.

 

My question is where will he fit them?
I'm thinking of procharging the strokee motor I've built. But I have no idea how you would fit 4 turbos under the hood...

 

Thanks for pointing that out to me. I'm not sure how I missed that he's trying to get the CR down to 6.5:1. Like you, I'm not sure the 6.0 pistons will do it, because I haven't seen one, but, it stands to reason that the wrist pin would be located higher on the 6.0 to accommodate the added stroke. However, at the time he shot the photos of the turbos in place, it appeared that nothing had been done inside the motor.

That clean motor was posted by someone else, and was used in a boat.

Yeah, it's common to feed one turbo from another. The point I was making is that you don't use that approach unless you are planning on big boost, and have a way to deal with the big heat which results from it. I can't imagine where he'll put a W-2-A intercooler that's big enough to cool that charge.

 

another"beautiful dreamer" should wake up and see!

6.5 comp ratio will take a 1/2 hr to spool-up and make usable boost, by then everyone has gone on down the road.

compound turbo systems on home built engines never seem to work out(tuning IS a nightmare, and expensive), not counting speeding tickets, trying to eliminate flat spots, during turbo transitions.

and i personally dont think a Jag V12 would enjoy much boost, and if you aint gonna make at least 1 BAR pressure in the manifold at peak torque, you aint in the turbo game!

and if factory pistons would work eveyone would be using them. uno usual stuff cracked ring lands, cracks in the skirt area, melted edges etc.

and the comb. chamber he is proposing, would detonate like hell.

also nobody makes a proper boost friendly headgasket.

 

Its a shame to many guys are more intrested in putting down than helping.
After 18 months of research i decided to take this on. its not the first car i have built tho it is the first turbo car.
This turbo config has the ability to provide over 30 pounds boost.
turbo will start to boost at 1200/1500 rpm 14 pound by 3500 rpm.
Head studs will be upgraded to larger as in TRW spec.
Pistons can be 6 liter or pre HE with HE head. total fuel management via twin ECU,s electric power steer pump for oil feed govened to 35 psi flowing through large oil coolers in rear of front guards. there may well be blow ups but i AM willing to try...lets see you do it.!

 

Shaun L,

I'd have to say that I'm guilty as charged.

I somehow missed what you had written on the other forum, about lowering the CR with 6.0 pistons, and I assumed you were simply planning to bolt those turbos onto a worn out V12, without any preparation.

If you use forged rods and pistons, get your CR down to around 9:1 (6.5:1may be a bit low for off-boost performance), and can somehow keep the heat under control, I see no reason why your efforts shouldn't succeed.

I don't know how much experience you have with Jaguars, but, you will find plenty of guys here who can give you advice to help you through most any Jag-specific problem you may encounter along the way. Although there has been plenty of discussion and theorizing on the subject, as far as I know, nobody on this forum has yet built a turbo XJS, so I will be very interested in seeing progress reports from you, and will be wishing you great success with this project.

 

Hey Shaun,

Glad you came over! Don't be put off by some of the initial scrutiny - these guys are a salty group, but LOVE the XJS, and are more than happy to put in their 2 cents worth (unsolicited or not). Guarantee everyone here wants to see you succeed (and make it into an affordable kit!!!!!!!!!!).

Please stick around and share your progress - there's a wealth of information to be had here, and it's a great community.

Cheers!

 

OK guys, i'll follow along with the dream!

Shaun you think you can make a Jag V12 handle 30-35 lbs of boost, and be even a little reliable?
OK have at it,were all a waitin!

 

As much as I hate to reopen a thread where I so obviously stuck my whole foot in my very opinionated mouth, I was wondering if anyone knows what has happened with this project since we last visited the subject.

Flint, have you heard anything from him?

 

There was a article in Jaguar World magazine several years ago (2002?) where a guy in Chicago built a quad turbo 7 liter XJS using a unused Lister V12 that had ben built by a race shop, then outlawed before it could be used. He was a computer software guy from what I remember. Used two fuel injection systems to get a injector small enough to allow it to idle without overfueling, and the larger injectors to supply fuel at higher RPMs. If I'm not mistaken, I think the engine put out something like 1600HP, and could be street driven with relative ease. Of course, the car could not apply that power at ANY speed. Even at 80-100, tire spin was a real problem. Seems I remember that the fuel would only last minutes as well, under full throttle. A unuable beast at best. Great conversation piece though......
I admire the attempt. Go for it! A goal without a plan is nothing but a dream....

 

Looks like as of July he built a custom manifold. There are pics in the original thread.

 

Too bad this guy has never posted to the forums again. I think its an excellant project.
A lost opportunity of knowledge and outside of the box thinking.

 

^^ agree 100%

 

I agree as well, and, regrettably, I think that the skepticism I expressed in my post is responsible for that.

As such, I'm emailing him a letter of apology, in the hope that it will persuade him to give this forum another shot. Not only because I would like to track the progress of his project, but, mostly, because I realize that as a member of a Jaguar-based community, it's my (and all of our) responsibility to offer encouragement, and, whatever little knowledge and experience I may possess, to a fellow enthusiast who is stepping out into uncharted territory. I know from my own project just how easy it is to get discouraged, and loose momentum on a large project. It doesn't help when you visit a forum where you hope to find kindred spirits to help you push forward, and, instead, you find some jerk (this jerk) is mouthing off about how it'll never work, because, you didn't do this or that. In doing that, I either disheartened him, or, lit a fire under him to prove me wrong. I sincerely hope it was the latter, because I'm certain that my post has deprived all of us of the trial & error knowledge that he is acquiring with every step he takes on his project.

Because of that, I owe everyone on this forum an apology as well. Hopefully, I can rectify my error in my email to the gentleman.

One thing I know for sure is that I don't like the taste of humble pie, and I like it even less when I eat it publicly. The memory of that taste will help remind me to engage on my brain before I activate my keyboard in the future.

 

JagZilla, we've all done it at some point. I think it's great that you're reaching out to him. I was considering dropping him a line as well.

Sure is an ambitious project - I'd love to see it complete (and offered as a kit)!!!!

 

Hello all
Yes i will admit i was put out by the comments.
But as a few have said they are not sure as to how i am going about it.
lets see if i can explain a little... as my logic works for me!
The quad turbo system is set up in COMPOUND configuration.
The reason for Hi boost is valve size limits. the valves limit how much you can get in at any air flow situation "upper limit" boost pressure in this instance is direct relation to restriction in air flow. Not in cylinder charge pressure.
The end result is at low compression ratios 6.5:1 or 7.0:1 the end result is combustion chamber pressures not a great deal higher than factory test units "jaguar" that ran well at 15.0:1 CR these were dropped tho because the reliability of the ign system once it had aged some what.
The Jag is progressing slowly money spent on new welding gear..learning to TIG weld alloy and just brought a new lathe to make things like injector bosses, spacers harmonic balancer for timing. purchased wrecked VS commodore for IGN parts throttle bodys ect.

AS a side note dodgy welds...lol any body can CRITICIZE from a arm chair very few do so while the parts are finished and in there hand.

I spent 18 months studying and problem shooting before i even removed a single part of the jag.
The primary Turbo`s "small ones" are suitable for a 2 litre Nissan RB20 and as such should start to boost at 1200 RPM (i am hoping lower) due to the fact that one bank of the V12 is 2.6 litre and run out at about 3500/4000 RPM the larger turbo`s are good for 600 HP each and should come on song at about 2500/3000 RPM but because the primary NEVER stops boosting it just has exhaust by passed to the large turbo to prevent over spooling there should be nil lag.
Pistons...now thats a whole game on its own.
there are two easy options for lower CR on the V12. early pistons late head
or 6 litre pistons in a 5.3 will do the same job, the benefit of early pistons is they ARE designed for the combustion chamber in the piston and as such more capable of boost situations keeping in mind over all CR is still inside factory design.
there are many other items like remote oil coolers in gaurds electric oil pumps
split air to air intercoolers triple pass radiator (my design) re route the cooling sys and many others to achieve this. This may take me ages but it WILL be done
Shaun
P.S thank you for the apology

 

I have a set of pre he pistons for sale if you're interested!

 

Hi Shaun, thanks for coming back and sharing your progress!

Seriously, quad turbo V12 - if the sound of that doesn't put a smile on your face...

One word keeps coming to mind: KIT. Even if it were sold in a detuned state, say to make 400HP at the wheels... I can see them selling like mad if reasonably priced.

Thanks again, and keep us posted! Love the pictures of the V(alley of death).

This is awesome