Originally posted by Bronk
It's based off fords modular motor design.
How do you know? It could just as well be based on the BMW one or the Merc. Or perhaps they are telling the truth when they say it is all new.
Originally posted by Bronk
Is it just a coincidence they started making the V8 jags shortly after ford acquired them?
Seven years after. Not "shortly" in my book.
Originally posted by Bronk
Or more likely they took an already existing Ford V8 and tweaked it.
I'll go with the later.
Conjecture and fallacies are all you offer to support your claim. Even the sites you present support my point of view.
From my link:
" It is perhaps then not surprising that on the Jaguar V8 the tensioners on the secondary camshaft chains in particular have developed a reputation for being troublesome. In fact it may not be that there is any weakness in the tensioners themselves, rather that at certain critical speeds heavy torque reversals on the chain can produce higher than expected stab loads, a condition which can probably be exacerbated by some usage patterns. It is perhaps interesting that the later 4.2 V8 uses more rugged morse internal tooth primary chains and that when BMW introduced a similar V8 (four valve, twin OHC, Nikasil bores, sintered fracture split con-rods) in 1992 they used duplex chains throughout. Whilst Jaguar's design team, in choosing a single link chain drive, did specify that it should be rated for heavy duty, one wonders if there have been any regrets that space wasn't made to use a duplex chain rather than relying on the lightweight valve gear to let them get away with the narrower option?
Of course, all engines have weaknesses that only become apparent with time and the engineering of the Jaguar V8 is not without many positive attributes. The combination of quite large valves and cam profiles of modest duration, allied, in the case of the naturally aspirated 4 litre, to a variable timing mechanism controlling the inlet cams, results in an engine with a particularly wide spread of torque.
The early variable timing device was a two state system - either advanced or retarded over a range of 30 degrees (at the crankshaft). Retarding the inlet cam eliminated overlap so improving idle and drive quality at very low speeds and light loads. It also meant the inlet valve closed later thereby improving power at higher speeds. In the mid-speed, part to high load range, the cam was advanced giving early inlet closing to boost torque, the extra overlap then also providing a degree of 'internal EGR' to reduce NOx emissions. Later engines use a more advanced system that optimises the cam phasing within a much wider range of, incredibly, 48 degrees.
With the benefit of hindsight the decision to use Nikasil plated cylinder bores instead of conventional liners might be judged a bad mistake, but it is one that was understandable and which caught BMW off-guard as well. The Nikasil process had been used for years on motorcycle engines and is in common use for F1 and other racing engines so it is hardly unproven technology. At the time BMW's exceptionally tight control of oil on the bores was thought to be a factor in their troubles, which would not apply elsewhere. In truth, instances of failure of the Nikasil coating appear to have been induced by poor fuel quality in certain markets allied to short journey usage, and engines running on low sulphur fuel would be most unlikely to suffer the problem. Jaguar resolved service failures in an honourable fashion but eventually decided to abandon Nikasil and revert to conventional cast iron liners (from VIN 42776 XK8, 878718 XJ8). The advantages of light weight and close running clearances were sadly lost. Ironically the fuels which caused the problem have now virtually disappeared from the market. "
Strange how many teething problems Jaguar had with their new engine if it was just a tested and true 5 year old Ford V8. Also interesting that BMW introduced a similar engine in 1992, which affected the Jaguar design which later ran into similar problems.
[sarcasm] Seems like Ford should have designed their engines better! [/sarcasm]
