OK
There are two basic V12 engine types: Pre HE and HE. The HE comes in 5.3 and 6.0 litre sizes.
ALL He engines run out of puff above 5,500 RPM. This is a factor of their interior combustion chamber design, and it is not easily or cheaply fixable. See Warrjon's thread on his engine work for some idea of what might be required.
The Pre HE engine ,as fitted to all XJSs for the first 6 or so years of their production, has a different combustion chamber design, and this engine is far more easily stretched and can rev more highly because it breathes better through the intake valves as high revs. You could probably get one to 7,500 RPM and still be making power. These early models DO exist in the States, but they are much rarer than the post 1981/1982 V12s which are all HE engined. They also exist with manual boxes from the factory, but this configuration is rare as hens teeth. The TWR racing XJSs of the early 1980s had Pre HE engines, even though badged HEs, for this reason
I am no more than an interested observer, but there are guys on here on this thread who really understand what is doable.
However this I do know, making a pre HE Jaguar V12 rev to 7500 RPM reliably and frequently is an expensive and complex business.
Greg

 

What Greg said +1

I believe making power from a HE is doable, but not cheap, essentially how fast can you afford to go. There are not the plethora of off the shelf gofast bits like Chev and then there is 12 of everything.

By the time I get my 6.7L built I would guesstimate $20k will have been invested, and I am working with HE 6.0L heads and doing a lot of the work myself, and who knows what power it will actually make.

I do know 500hp @7500rpm is doable in an XJS engine bay, cost - who knows.

IMHO you are much better off building for torque (capacity increase) and let power be what it is. My 6.7L should have around 450ftlb torque, by the time the guy in his 500hp @7500rpm car gets going I'll be gone, - well at the legal speed limit of course.

 

realistically, I don't see the point of building an NA motor (any motor, be it a honda B or K, or a chevy LS series) for torque. Just blow the thing if you want that (which I'm considering. I think twin centrifugal superchargers would be the way to go - significantly less work than fabricating an intake for a roots deal, and far more likely to fit under the hood). However, I love the idea of revving engines out. I used to own an S2000, and I got addicted to high redline stuff the first time I put my foot down. Realistically, I'm not terribly interested in making BIG power. I just want to make it scream, which is why I'm asking about the capability of stock components to handle rpm levels.

Sure, a bump from 300 to 400 horse would be nice, but so long as it keeps pulling right up to the top of the range (and the ideally flattening out about 500-200 rpm before redline, so as to make the experience of shifting a natural one and one that doesn't seem frustrating because it feels as if the engine had more to give) I'm happy.

Do the HE heads have an issue with power or do they have an issue with rpm? because I thought the real reason why power curves started sloping down at RPM was because the intake couldn't provide enough air/fuel mixture in the increasingly short periods the valves are open for, not the combustion chamber itself (which I thought mostly impacted efficiency of the individual combustion).

 

True enough, I was going to do this to my 5.3L but our Government changed the rules and now it would cost me more to FI because of the engineering requirements in blowing engines above 3.0L.


The HE combustion chamber is quite efficient, the timing curve of the HE to pre-HE confirms this. The HE uses about 10° less advance to make the same power.

Power and RPM are intrinsically linked power = torque x rpm / k (k= constant - HP = 5250 or KW = 9540).

Power curves start to drop when the intake air velocity reaches Mach 0.55 which in the 5.3L happens around 5800rpm be it pre-HE or HE. There are so many factors that effect this - Valve curtain area, minimum port cross section area, The ratio of valve curtain area to port cross sectional area, and the list goes on.

What people usually do is hog out the port to flow more air but unless the port area is matched to the valve train then power WILL be lost due to the drop in pressure wave force.

The intake valve size in the V12 is capable of supporting 500hp, the issues I see are.
1) Intake manifold to head is too big, the manifold opening is about 34mm where as the runners are 33mm and the opening in the head is about 36mm. These area changes reduce flow and cause turbulence in the intake tract.
2) In the HE head the intake valve is recessed into the head shrouding the valve until nearly 1/2 lift. I've de-shrouded the valves in my head.

 

well i see we have another who is going to reinvent the wheel!

go for it , show us what you got!

pic is already 7yrs old.

 

I'm not reinventing the wheel by any means, earlier in this thread a bunch of people were talking about methods to get low-end torque. I'm saying a high-revving race engine, like those we all know existed, is what I'm after. The engineering has all been done already, the problem is collating that knowledge and utilizing it with a fraction of the budget. Although if head flow is such an issue, I may need to revaluate some things

 

The buy Allan Scott's book, there is enough info in there and these threads to build a 7500rpm V12.

TWR and Jaguar's XJS by Allan Scott Hardcover Book 9780987666550 | eBay

Here is a source for go fast parts.

Jaguar Engine Parts

 

Until now, I have resisted adding our work of extracting max power from Jaguar V12s, because it was gained before there was an "HE"; it was not constrained by needing to fit in a car, let alone street legal; and it was produced using the enthusiastic resources of a team of dedicated high performance engineers already committed to stretching the envelope for Australia's racing Jaguars of Jane, Geoghan etc.

However, subject to some caveats, I feel I can offer some findings that may help. Briefly, and totaling only 4 such engines, all were as developed and built for our Australian Unlimited Hydroplane "Jagged" in the early '80s. I will omit all I consider irrelevant to the OP's quest, but perhaps some of what remains will be of value.

Great advice from both . . . I endorse absolutely.
OK; back to "Jagged". Some brief specs, although my detailed notes are long gone -

• Jaguar V12 5.3L engine, minus all manifolds and peripherals except alternator and much modded Lucas EFI and injectors;
• bored and stroked to just below 6L and fitted with custom flywheel, dog clutch and 1.5:1 vee drive;
• full sets of custom machined chrome steel journal caps to crank and cams matched with new cs studs, washers, nuts etc;
• matched sets of custom chrome steel pocketed pistons and sleeves to increase bore but reduce CR;
• pistons, pins, rods all polished, crack tested, nitrided and balanced to 0.1g (lab tested at Lithgow Small Arms Factory);
• heads ported and polished using sheetmetal templates to match all port diameters, throats and profiles;
• new custom billet machined camshafts to get faster lift and extended duration and overlaps - especially across TDC;
• full sets of custom manifolds based around twin flanking Toyota Supra turbochargers running at (IIRC) 2.5 - 2.9bar;
• fuel blended across 20-30% methanol with up to 5% castor oil - the Lynx dyno ruled out several then popular blends;
• twin 1.5m long megaphone water injected exhausts - the added on water pump drawing about 12-15HP.

First 2 engines ended in tears, both at the top end - not bottom - and at (IIRC) 7300 and 7600 RPM - and neither made it beyond the Lynx Engineering dyno. With further development of cam profiles and custom caps, latter 2 made it into "Jagged" - were monitored by tell-tale memory tachos - and were alternated across 2 seasons of racing at these high 7000 RPMs.

Based on my memory of the manifolds and placement of turbos, there is NO way such a package would fit into any XJ-S, even ours which currently has no floors! The 5' long megaphones would look great (but confusing) way out forward of the bonnet and grille . . . but 10m (30ft) long rooster-tails of water would prove messy. Another feature of our very lumpy turbo'd engines was that idle speed varied around 3000RPM - up from an unreliable 2700. Finally, our application was based on little finesse needed between idle and full throttle. We saw 8000RPM briefly on each of engines #3 and #4 but only on the dyno. Ignition interrupter aboard "Jagged" was set to 7800RPM limit.

Summary . . . Jaguar V12 EFI is very strong out to (say) 6000 RPM. Going beyond is possible, even feasible, but exponentially expensive. Even with new parts custom machined from billet chrome steel, but perhaps flowing from our aggressive cam layouts, it was surprising that weaknesses were exposed at top end, not bottom. Also, I recall that first set of pistons were all re-machined and re-matched to increase top pocket, thus further reducing CR and enabling the lift to 2.9bar.

Hope some of this helps . . . and thanks for jogging some distant but fond memories. Of course, more recent technology makes all this ancient stuff of chasing 8000RPM child's play. Any decent top end, but stock, motorbike engine can pop these numbers with just a flick of the wrist!

Cheers,

Ken

 

HI Ken , how do you like the 2.7L TTD S-type?

interesting you have a Diesel car!

 

Love it Ron . . . just love it.
The S-Type is a great touring saloon - especially living some 500Km away from anywhere citified! We only saw the 2.7L TTD after 2006 here in Oz as, prior to that, there was poor availability of premium diesel fuel. So ours is one of the final run, with all the development updates that made it into these 2007/8 TTDs.

Perhaps not for everyone; especially if a daily stop-start low mileage city drive, but get out into my "wide sky" country that you fellas in the south and west USA share . . . push . . . and 3 things still amaze . . . engine at idle is virtually silent (tricky); road speed at a steady 2000-2500rpm is ridiculous (exhilarating); while instantaneous fuel usage will hover around 5L/100Km (50+ mpg). Only 2 downsides mar the car for newcomers . . . enormous low end torque can trap the unwary, and the wide Pzero tyres on 18x8" wheels can transmit more road bumps on broken roads than other premium Jag saloons tend to absorb.

Overall, Ron . . ? Brilliant! It's no head snapping XK8/XKR . . . nor can it match the ultimate in high performance comfort of an XJR . . . but it's soooo close, at a fraction of the cost, and still has that "smells new" aura.

Cheers,

Ken

 

Aand it can snap it's crankshaft As commonly the case in Britain

 

Being a long time UK Forum member also . . . I've been exposed to heaps of experiences that differ from mine. However, apart from DPF and sump oil dilution issues that can arise from negligence and total absence of correct maintenance, most myths quickly evaporate when challenged to put up the evidence.

Yes . . . there is no shortage of those who knew a bloke, who had a friend, whose neighbour's Jaguar TTD experienced runaway self detonation . . . wiped out a whole neighbourhood . . . and was totally replaced under warranty by Jaguar to avoid bad publicity . . . Truth is, most of the documented / photographed / verified stories of this ilk turned out to involve unattended stationary or marine diesels. "Common in Britain?" Perhaps Daim, you can offer up the proof that "snapping its crankshaft is common in Britain".

I'm not looking to be confrontational on this but . . . I sought out this car on the basis of it being awarded the "Car of the Year, 2006" by Australia's premier auto road test magazine "Wheels" and I stand by my posted analysis of both its strengths and failings . . . as well as my challenge to list proof of this supposed "commonplace" failing.

Now, those first 4.0L petrol V8s with their plastic timing gear carriers . . . there was something to really worry about.

Cheers,

Ken

 

Ignore previous . . . none of us need justification . . . nor aggro.
Besides, we have veered way off topic.

 

Attached are some pictures of a 2.7l V6 diesel crank removed from a Jaguar (not sure if XJ6 or S-Type).



Sure, the plastic timing chain tensioners are crud, but can be replaced (as I have already done). I'm not saying the V6 is "rubbish" but there aren't only rumors about it cracking off. The V6 diesel has a bad reputation (best example from Auto Reserve Jaguar, a company specialising in Jaguar parts for models beginning with the X300 to today). This crank is one of their car engines. They had also only ever heard of it but seeing this is a little painful...

I personally had never heard about this happening before I saw this and then searched afterwards. It happens not only within the Jags, but also in the Peugeot 607 and Citroen C6. The crank just doesn't seem to cope with the power the 2.7D can provide... At least when the power is used all the time...

 

possible , but rare.

my experience in engine rebuilding diesels, V6s of many types , had crankshaft breakage!

i'm not saying common, but have seen some!

my opinion was V6 diesels puts an unusual harmonic vibration at a certain rpm/load, that manufactures may have excepted as normal!

my thought was the short length of shaft just cant take the diesel power stroke impulse, for long term vibrations of torque and twist, like winding up and then unwinding with a snap!

and

some of the engines i seen changed metallurgy quality, and seemed to help, but costs increased and was hard to get the bean counters to agree!

and daim just dont like diesels, but Europe buys at least 50% of them manufactured.

cant be all wrong!
.

 

I don't not like all diesels. Just diesels in cars. And after dieselgate even less from VW AG

I'd love a vehicle with a Detroit Diesel or Foden two stroke diesel. They just sound soooooooo nice. Or a more compact Commer knocker... 3 cylinders, 6 pistons, 1 crank, 6 rocker arms... Screamy little beasts. But living tgere where the air stinks of diesel fumes... No thank you.

Btw. Germans bouggt last year only 43% diesels. The cear before it was 51%. So the numbers are declining... At least with new cars...

 

I have seen wrecked V12s and wrecked 2.7 diesels. (A couple of years ago my local specialist maintaing my XF 2.7 had three on the floor one day I dropped by). And with the exception of one V12 it was down to neglect in every single case. As in no service at all for 100k km or more. Yes, some engines can take that kind of punishment without breaking. Like older US iron. But few others and hardly any moderns. 'nuff said.

 

Well said all . . . but let's leave diesels . . . way off topic, anyway. Ah, Ron, your question tempted me "to the dark side".

I'm really surprised no-one rose to my comments . . . "Of course, more recent technology makes all this ancient stuff of chasing 8000RPM child's play. Any decent top end, but stock, motorbike engine can pop these numbers with just a flick of the wrist!"

When I wrote that, I was reflecting on my disbelief of the fabulous Suzuki (that my daughter learned to ride on quite some years ago) . . . inline 4 cylinder DOHC, twin sparks, but can't recall whether 4 carbs or efi . . . all this crammed into a package almost impossible to change plugs or service . . . redlined at 12,000rpm and total capacity of a neat 250cc. Yep . . . 1/4 of 1 Litre.

By my guesstimate (and with new crank and crankcase) a V16 or H16 based on that technology, if blown, should yield somewhere around the 500HP sought by our OP . . . all out of just 1.0L and in a package about 1/4 the size of our Jaguar V12s. Now . . . I'd like to see that!

Ah . . . but despite all the screaming, I bet it wouldn't have the prodigious roar and breath sucking torque of a really well modded, mighty Jaguar V12.

Cheers,

Ken

 

hear, hear!

 

"second the motion" gotta love a V12 engine, my 1st in 1950, V12 Lincoln coupe ,, "the Slinkin Lincoln", my dads words !