The problems with the Jaguar V-12 engine were two fold.
By the time the last XJ-S rolled off the manufacture’ assembly line (in 1995?) the engine was obsolete and way too heavy.
At that time Jaguar‘s resources were already directed towards their V-8 engine for the XK8 that debuted in 1997.
The sale numbers for the XJ-S convinced Jaguar that the future was not in a low production, expensive V-12 engine.
That said, the best engine to replace the aging V-12 in 1995 was the SBC Chevy engine. The advantages were light weight and perhaps more important, significant torque and relatively low RPM’s.
The problem was pricing. Nobody was going to buy a high end British luxury automobile with a pedestrian, less that state of the art, Chevrolet engine.
If Jaguar had hopes then of keeping the XJ-S alive an engine was needed and it was not the existing obsolete and heavy V-12.
The answer was within Jaguar’s reach if they wanted. The Aston Martin double overhead cam V-12.
This engine is made by Ford at a separate area of their engine plant in Cologne Germany.
Note that at the time Ford owner both Jaguar and Aston Martin. There would have been no issues with Jaguar licensing to use this V-12 in a redesigned XJ-S.
To differential the engines, the Jaguar V-12 could have been tuned for less HP (500?) and more torque.
This is a properly designed modern 5.9 liter V-12 with double overhead cams and VVT that currently makes 575 HP (595 in Europe) and 460 lbs. of torque in last year’s DB9 Vanquish and Vantage. (Note that Aston Martin has reached an agreement with Mercedes Benz to use their turbocharged V-8 and V-12 in the latest versions (2019) of their automobiles. This is not a knock on the mighty V-12, but a nod to emissions and the current move to pressurized engines for fuel economy.
Unfortunately, Jaguar saw no future for the V-12 XJ-S and passed on, what I believe, was the only hope of keeping the XJ-S model alive. Later XJ-S versions utilizing the 6 cylinder engine left the car underpowered and lacking that special engine that made the car a great automobile.
Aston Martin are using the AMG V8 but not the AMG V12 in their current line up. They have a new bi-turbo V12 of their own.
In the ‘90 the quick fix for more HP was a supercharging. A supercharged 4.0L A16 XJS could have been special (in the 90s) but may have been too much of a rival for the DB7 which started off using a supercharged 3.2L AJ16.
The XKR100 was a worthy successor to the XJS.
The SBC was a great engine but now dated too. The LSX is in another league.
The V-12 5.2 liter engine is an Aston Martin developed engine. (Their first twin turbo engine I believe) Its compatible with the Mercedes Benz electronic architecture as they are using MB drivetrain technology.
Chevrolet has got so much mileage out of the SBC that I would not be surprised to see that engine in their main stream cars for some time. It has IMHO, outlived its usefulness as a true high performance engine.
Its safe to say the next Corvette will have a double overhead 4 cam V-8
I thunk the SBC hasn’t been used by Chev for a long time. The LS series was introduced in the ‘90s and it’s a different design to the SBC. For starters it’s a Y block.
Yes the next corvette will be 4 valve (and mid engine) according to the media. The Camaro now handles so well Chev is needing to take the corvette to the next level.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
25
You’re apparently confusing the SBC with the LS. True enough, they share a lot of dimensions, but the LS is really an all-new design that is known for vastly better breathing than any incarnation of the SBC. Oddly, there are people so stuck on the SBC that there are aftermarket companies selling blocks that utilize a SBC bottom end but use LS heads. Weird.
Not sure why anyone would want a SBC any more, as the LS is considered vastly superior in all respects. I think the LS comes with an aluminum block in cars but a cast iron version is used in pickup trucks, so you can actually choose your preference.
There are lots of variations of LS. The current hot ticket is the LT1 (that’s an LS, I think they reached LS9 and decided to move on to LT numbers), which produces 460 hp in stock form. It has direct injection and variable valve timing, both features that should mean excellent fuel economy. There are also a couple of supercharged versions that are available in Corvette ZR-1’s and Camaros, but the fuel economy really suffers when you bolt a supercharger on it.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
26
Yes, but they’ve told us that before! In fact, they’ve had 4 valves before!
When I mention the Chevrolet Small Block (SBC) engine I include the LS family of engines as well.
Note that SBC is a generic engine description only.
Yes, the LS engines are stronger, breath better and are vastly superior; however they are a natural design evolution of the original SBC 265 CI V8.
The basic design concept is the same. Two valves per cylinder driven by a central camshaft operating overhead valves.
The Chevrolet LS engine, introduced in 1997 in the Corvette is referred to in Chevrolets description as the “Gen 111 Small Block engine”
Chevrolet later produces the “Gen IV Small Block engine” (again based on their description) which feature cylinder deactivation. The Gen IV family includes the LS2, LS3, LS9 and supercharged LSA and LS7. All referred to by Chevrolet as” Gen IV small Block Engines.”
IMHO, the differential between the original SBC and the later LS engines are important from a standpoint of performance and of course parts.
However, as per Chevrolets own description, the generic description of
“Small Block Chevrolet Engine “applies both the original SBC and the later LS family of engines.
but the SBC and the LS , are completely different engines(except for diminsions), altho some do think they are related, but not so and LS .LT.etc. are light years ahead of our wonderful OLD SBCs.
i sure worshiped them in 1955 onward till i got hold of my 1st LS2, never looked back !
ron
some dont believe that a factory stock Special high Performance OPTION SBC 283 cu.in. could rev past 7000 rpm in 1957, i know i owned one , Corvette F/I, 4 speed , limited air flow fell off after 6000rpm, converted to twin 4 barrels , and revved to the moon!
the CAM was the real trick tho, Zora DUNTOV himself designed the lobe shape.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
30
Chevrolet may call the LS a SBC – perhaps to capitalize on a positive reputation – but nobody else does. The terms SBC and LS are used by the auto enthusiast community to distinguish between two distinct families of Chevy engine.
I think we have forgotten what the original description of the SBC was. It was a generic term to differentiate between the small block (283, 350) and big block 396, 427 rat motors with the canted valves.
The fact that the LS motors are significantly different form the old 283 is not the point. The point is that it’s a small block Motor as defined by the original description of small block / big block. That’s why Chevy calls the LS a SBC.
Now I understand that the description of what is a SBC seems to have become muddled after the LS engines came out because the block design has changed. But the designation of SBC is not based on block design or camshaft location or improvements head breathing. It’s based on engine block size. In short, engine block design does not identify the engine as a SBC. Block size does. Based on engine block size the LS family of engines are SBC. Chevrolet certainly thinks so.
I agree that most car guys don’t consider the LS as a SBC. That said Chevrolet continues to refer to them as the latest generation of the SBC on many of its print media.
So I am putting this topic to bed from by end. (smile)
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
37
It would be interesting to know the respective numbers of V12 engines produced…
Why I say this, is because I see newer cars with exotic V12 engines (BMW?) being scrapped because the cost to service even minor parts of those engines is prohibitive. I looked at a BMW with 12 electronic throttle bodies that needed something like $2,500 per throttle body. Might be good when it was new, but trying to keep that classic going is going to cost someone an arm and a leg. The same is probably true of the Aston and Merc.
The reason you use a V12 is not for the power or torque. It is to “have a V12”. You can get the power or the torque from physically smaller, lighter and more economical power plants. Personally I find the outrageous V8s in the newer Audi or Merc performance cars too crude to be serious. Or to put it another way, why spend all that money and only get a V8? Whatever its faults, Jaguar did deliver turbine like smoothness.
Perhaps this is why the electric vehicle is winning. It doesn’t cost any more than a top end V8. But it goes faster without making all the crude noise or the manic gearbox crashing and banging of the paddle shift. 98% of the time you want the refinement. It is rare nowadays to find some road where you can exploit the performance, and if you can, it is better they can’t hear you coming …
so true about V12 owners , Looky ME , i got 12 cylinders, nobody actually positively needs 12 cylinders!
i have one just to say so,its an EGO thing!
a modern turbo 4 cylinder will run all day long at 120MPH, and give good MPG cruisin at speed limits!
but all v12 cars seem to have NO values, i know about 8 yrs ago, a perfect 1998 BMW 750L V12 with a bad transmission sold for $1500. USD , trans replacement cost over $7000.
and just last year , a local car lot sold a good running ,loaded all bells and whistles, no problem Mercedes 600 v12 , for $3000.
a shame , but it what the market will bear! if a car has a serious problem , in todays world it costs more to repair than the cars are worth!
ron
Well even non-V12 high end cars suffer the same; just spent my week fixing oil leaks and doing a few upgrades on my e38 740il. At local labour rates and fixed rates still over 30 hours for what I did it would have been more than the resale value of the car and that’s with the V8. I feel we are at a tipping point though, most of the parts from the scrapped luxury cars make it back into the market now providing easier access to those of us who do our own labour. It’s a bit of a detour from the topic at hand but I can see German luxury engines being the scrap yard racing engines of my generation. $300 gets me a new BMW v8 all day on locally with zero shipping
