copied from other forum, what's yr opinion?
I said long time ago that S2000 engine is king, yes, only becoz Rover ran out of money (now busted) & couldn't get the original K Series to perform, basically Jap engines as race engines are crap:
Basic Design
The fully floating design (open top deck) is a clever and effective solution seen in many engines, not least the newest generation of Honda and Toyota engines and there were absolutely no compromise in the stiffness of the second generation K series block.
The block and ladder frame that support the crank were an absolute first for a mass produced engine. This arrangement is immensely stiffer than conventional bearing caps, which allowed the block to be very light. This is the area of the block that actually supports the crank and therefore carries all the loading imposed on the engine by the crank. It is where stiffness is actually required in an engine. This design was only previously seen in fully-fledged race engines – F1, Nascar, etc. and had never before been seen in a 4 cylinder. It is one of the design elements that make the K such a sophisticated and efficient design. Far more so than, for instance, all current Ford 4 cylinders including the Yamaha/Ford 1.7L in the Puma and the very new all-aluminium 2.0L Duratec, plus the likes of the much vaunted Honda 1.8 VTEC. The only engines which have caught up with the K are the 2.0L in the Honda S2000, the 2.0L from the Civic-R and the 1.9 VVTi in the Toyota Celica. All are copies of the K Series in this essential area of engine design.
Another frequently heard criticism of the K that it has very narrow main and big end bearings. This is a feature of the fact that the engine is very compact with narrow centres of 88mm. Only the Yamaha/Ford Puma engine at 86.5mm and the Yamaha/Toyota VVTi at 87.5 are narrower. This again contributes to a lightweight block, but I would say to those who consider that the resultant narrow bearings are a weakness, to look at any of the current F1 engines. Having seen a stripped down 1997 Supertec engine I can tell you that the F1 engine bearings are not huge and like the K’s, are certainly a lot narrower than the older generation of much tuned Ford engines or any of the new generation of in line 4’s, with the exception of the Puma and Toyota engines with their bike heritage. There are good reasons for this, firstly narrow big end journals with slightly larger diameters give good bearing overlap which makes for strong cranks and secondly the larger the bearing surface area the greater the friction loss in an engine. Therefore, it is in the interest of power output to have as small a bearing as possible. In order to enable this, the loading on the bearings needs to be minimised. This in turn is achieved by having as stiff a crank as possible, by accurate counter weighting in the crank and careful associated design of the block, by having as low a reciprocating mass as possible and specifying a tight F3 dynamic loading tolerance. It is worth noting that the K’s tolerance for the latter is half that for the Ford, Alpha and Mercedes engines I have tolerances for, and for that reason the K is a well balanced engine with low resultant F3 bearing loads. Most Ford engines are particularly poor in this respect.
Loads imposed on the block by the rotating mass and fluid forces – combustion loading, will cause any engine to flex whether it is an old iron dinosaur, such as a Chevrolet V8 or Ford Zetec, or the modern aluminium block in a Puma, or the K. The problem is to manage these stresses. The K does this by, instead of using a series of bolts to close the cam carriers-to-head and head-to-block and block-to-ladder, one long bolt which goes right the way through the engine. The metallurgy of this bolt has been very carefully designed and the torqueing at 64Nm brings the bolt to its yield point. Effectively the point at which the bolt will stretch with the block under its cyclic loading, to distribute these loads very evenly throughout the block. Thus the block is relatively unstressed within the design parameters for performance for the engine, the load being carried substantially by the long bolts. This also contributes to reducing the mass of the block. The design and metallurgy of these bolts is critical to the whole design and loading that the engine sees.
Engine Weight Comparisons
All of this tends towards a K series engine that weighs in, as standard, fully dressed at 96.5 kg. Compare this to the Honda S2000 engine similarly equipped with standard manifold clutch and fluids at 158 kg and the Toyota 1.9 VVTi engine at 137 kg. The Rover engine’s compact size and weight are a significant advantage in a lightweight race/sports car of the Lotus 7 type or the Elise. Note, a full race K Series weighs 78 kg including 7 kg of fluids. Compare these figures for output in terms of power to engine weight. See Table:
Engine / Power Output / Power-to-Engine Weight
Ford Duratec 2.0L / 140bhp @6000rpm / 1.16bhp/kg
Honda S2000 2.0L / 237bhp @8300rpm / 1.5bhp/kg
Toyota 1.9 VVTi / 189bhp @7800rpm / 1.3bhp/kg
Standard K 1.8L / 120bhp @5500rpm / 1.25bhp/kg
K VHPD / 184bhp @7000rpm / 1.91bhp/kg
K R 500 / 235bhp @8500rpm / 2.6bhp/kg
K K2000 2.0L / 293bhp @8500rpm / 3.9bhp/kg
However, this tells only part of the story because most of the Japanese engines like the old 1.8 VTEC and the new I VTEC engines are all short stroke, big bore engines, all of which have a relatively narrow power band. The K with its 89.3 mm stroke produces a lot more torque and spread over a wider engine speed range. This makes the K’s power to weight ratio all the more remarkable in the context of lightweight sports/race cars, and given its more advanced construction than all but 2 or 3 of its most recent competitors, it is clear that the K has a very strong claim to be the best 4 cylinder engine around. In fact, given the huge weight penalties of the Japanese engines and the backward design of the new 2.0L Ford – indeed most of the engines around at the moment, the only clear competitors to the K’s crown are the motorcycle derived engines.
The limitation of any normally aspirated engine, that is an engine that is using engine speed to pull the fuel mix into the cylinders and hence produce power, is piston speed. Piston speed is a function of both engine speed and stroke. To put the K’s ability into perspective the Honda S2000’s 2.0 litre engine the one that the Lotus people on the one make series aspired to, revs to 9000 rpm as a production engine. With an 84 mm stroke this achieves a piston speed of 4960ft/min, with its longer stroke the K achieves this at 8460 rpm, something the standard K bottom end is perfectly capable of, with the sole modification of forged pistons. The R500 engine achieves a piston speed of 5390 ft/min at 9200 rpm [the R500’s rev limit has of late been cut to 8500rpm], a figure that the Honda engine would only match were it to be revved to 9,800 rpm. The point is that big bore short stroke engines are conceived to make high engine speeds possible, the penalty is poor torque, the Honda 2.0 litre S2000 producing just 151 lb/ft @ 7500 rpm, a figure easily eclipsed by the 1.8 litre K equipped with Piper’s 1227 cams which will give a very similar power output to the Honda engine. So, the Honda is not such a special engine. It does have a very strong and stiff block, being a copy of the K Series’ design, but suffers from its enormous weight of 158 kg in standard form fully dressed (figures from the Vemac Car Co.) more than 60 kg heavier than the standard K. The only really attractive part of the Honda’s design are the roller cams which do reduce friction in the valve train but in every other respect the K is a more efficient and effective design than the Honda.
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Originally Posted by Chapman
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