I’ve seen a recent release that Burlen intends to release EFI within a SU carb body, and I beleive similar options have existed for Weber carb bodies for some time.
This is a neat idea, and I’m sure a boon for reliability & fuel efficiency, but somewhow adding a computer control to a 50+ year old car seems odd…
Which got me thinking, has anyone ever done a more period correct mechanical injection system on an xk engine? Mercedes and Chevrolet both offered factory MFI in the same period as the Jag XK 140/150.
Thanks, the Lucas injection story is pretty cool. I had read about the Spica, that was interesting as well, sounded somewhat similar to the CIS Bosch system used by Porsche, that I had in my 73 911…
As somebody who owns a few Mercedes Benz with MFI (6 cylinder and V8’s). I would suggest that this is not a good idea. I’m pretty sure that you can adapt a TBI setup with megasquirt to the twin carbs which will look close to factory once the air cleaner is on or find an intake from a later XK motor and make it work.
If you search Google, I saw years ago, a smarty had worked out how to install GM injection within the SU, it was simple, I’m pretty sure there was 2 each injectors coming up thru each carb, some guts removed, GM hardware, looked fairly standard. I cannot remember how he handled O2 sensors etc
I obtained a kit made by Tecalemet Jackson back in the seventies, bought it from Lynx who had run it on a 3.8 motor, included a long tract manifold with 40mm throttle bodies, a six way manifold for the injector pipes , engine driven pump and high pressure electric one, six capillaries injecting fuel a couple of inches from the intake, ran it for a couple of years but need constant adjustment of the various pressure valves, but, when it was in tune , it pulled like a train, but not much fuel efficiency !! down to eleven to the Imp gallon…big swirl pot in the boot helped get rid of the aeration in the fuel…
There are two reasons why conventional fuel injection works so well:-
1/ the fuel is injected directly onto the back of a closed and very hot intake valve where it vapourises instantly and so is in exactly the place you want it;
2/ the electronic control element of the process ensures exactly the right amount is injected no matter what the operating conditions and timed to happen optimally. In addition, if acceleration is instantly detected and exactly the right amount of fuel is added to the injection pulse. When the car is coasting, it cuts the fuel pulse.
This mechanical system has none of these advantages - it injects a long way from where the fuel is needed and doesn’t have any more than a blanket change for temperature, transients, etc.
To be clear, I’m not likely to do anything, as the SU’s perform acceptably and I’m reasonably adept at getting them sorted correctly. I certainly have no interest in EFI as it just seems wrong (which is saying something for me with my car as modified as it is)…
I’ve just always loved the idea of MFI for some reason, and since Jaguar’s competitors were using it as early as the 50’s it would “fit”, but not really worth the cost incurred in designing a system. The Tecalemet Jackson sounds pretty interesting… but would take a lot of digging to replicate something of that age.
Another “idea” to park on the shelf unless I hit the powerball (which is unlikely since I don’t buy tickets)
at the outset there is a difference between engines that are designed for fuel injections and engines that aren’t . The XK engine was designed for carbs, whereas the Jaguar 12 cylinder engine was designed for FI - I read somewhere that the Jaguar engineers were disappointed that the FI wasn’t yet finalized when the first 12 cylinder cars were to be marketed and had to be equipped with carbs. - The Mercedes 6 cylinder as initially used in the 300 SL was already designed for FI.
Then there is a huge difference between mechanic and electric systems. The big FI victory tour in the mid to end-70s began with the Bosch K-jetronic, which is basically the CIS injection. Obviously it was much more adaptable to different engine needs and at the time it was common practice to have one “injection” model top of the line, typically with a 10 % gain in power, reasonable consumption and improved cold start and idle. Some products I remember are Audi 100 5S and 5E, Mercedes 280 and 280E, Citroen CX 2400 i.e., Opel Commodore GS and GS/E.
The mechanical predecessors were very expensive (Mercedes 220S, 220SE) and/or hard to handle. It is an ironic twist of history that the US market didn’t receive the TR 250 and TR 5, 6 PI, but carbed cars. The Lucas FI was mechanical. It works very well, but it takes an expert to set up an maintain. Many drivers today are happy to find the “easier” US version with twin Strombergs. One typical fault though has nothing to do with the FI - it is simply caused by the heating up of fuel guided along the hot exhaust parts …Kugelfischer mechanical FI have a quite good reputation for being adaptable and power enhancing - they were used on BMW 2002 tii, Ford Capri RS, Peugeot 404, 504ti, Lancia Flavia 1800 i.e.
So, while there are good reasons to upgrade the XK engine to the last and fuel injected versions I can’t see many for making up a mechanical FI - in fact the only one I can see would be to replicate one of the Jaguar racers of the late 1950s.
While I run a 123 ignition - basically hidden in an unobtusive fake distributor body - and like both looks and technical result I can’t see much of an advantage to operate a flawed FI system in the guise of fake carbs.
That’s basically the conclusion I’m at is it’s not worth the effort for the benefits realized. Bill Terry got over 400hp from an XK engine still running on carbs, there’s apparently about 20hp gained in converting the head to twin plug which probably would have similar cost to a home-brew MFI.
I just love the old mechanical systems, my dad was considering buying a '57 FI Corvette and that’s probably what got me fired up about it… reading the old road tests where they talked about how much better the MFI was than the competing dual 4bbl. Of course SU’s are a far superior arrangement to the 2x4bbl, and SU basically gives many of the fuel injection benefits since it’s actual metered fuel, and also mostly eliminate the fuel sloshing problems associated with Holley type carbs.
400 hp on carbs - maybe I’m too skeptic, but that must be the same kind of horse Jaguar initially claimed to be 245 of in an XJ …
Calculating in DIN hp a twin SU SI and SII has available around 175, a triple SU E type around 200 and a fuel injected non-cat XJ SIII 205 hp. After some classical tuning work I’d expect to find 210 DIN hp at the wheels of a triple SU car. Some report 300 hp http://www.classiccars4sale.net/classic-car-how-to-guides/restoration/How-to-tune-your-jaguar. This is probably feasible, but may make sense only for classic motor sports. With more serious work I’d assume you can achieve some 260 reliable hp.
I’m running a Terry’s “Cat Claw” head, which I can’t find specs for but
included taller cams, bigger valves, porting and polishing; claimed good
for ~100hp over stock with appropriate other modifications. I’m still at a
mild 9:1 compression, with SU’s, but custom Hayward & Scott headers.
Hi Brandon,
I’ve had a few conversations with Bill on various Jag subjects and always found him to be a straight shooter! I’m sure that you’re right about the cost of this engine as I was just looking through a GTJ catalog from 1990 and they were “claiming” 400 HP back then for their level 6 engine that cost $27,000! I don’t know how many here have seen a dyno pull but I’ve seen several and found them to be rather scary, even standing behind bullet proof glass. A friend of mine built several V12 engines, one was for a XJ13 replica, 425 cu that developed 499 HP and knowing how much work, time and not to mention money (guess that I just did) was in it, you can’t help to be a little uneasy until the run was finished. The shop that did the pull also did the heads and Matt was told that probably another 25-40 HP could be found in something besides the stock intake manifolds alone but no further development work was done as it was not intended as an all out racing engine. As I recall the stroker crank was out of an off shore racer. I can’t recall the size of the other engine that was intended for a street rod but it had a huge blower, longer then a GM 671and with 11 lbs of boost produced 635 HP, again no effort was made at further development but big HP=BIG money!
Bob
889076
Plymouth, Mi.
sozfingers
(Keith. P. series two roadster,,,UK)
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When I rang TJ for advice, not only were they really interested, but they sent me the blueprints for the system as they were no longer manufacturing, these blue prints were in a tea chest with all the equipment when I changed to Webers and were stolen from my garage along with many spare parts, …