Comparision between a straight-4, V6 and a VR6's cylinder block, viewing from above. The V6 has the length equals to 3 and a half cylinder in-line. The VR6 approaches 4 and a half.
However, it is a lot narrower. In a conventional V6 far leff , one bank of cylinders mirrors another bank. This means, air enters from the center of the V and exhaust flows out from outside of the V.
In contrast, a VR6 near left has the air intake from one side and exhaust from another side for ALL cylinders, no matter in which bank, so it is an asymmetric design. As the hot exhaust manifolds and pipes are located at one side only, the VR6 does not need to reserve as much space for thermal clearance at the other side.
This allows it to be easily fitted in FF small cars whose engine compartments are originally designed for inline engines only. Valve Gear The first generation VR6 had 2 valves per cylinder, single overhead camshaft SOHC serving each bank just like any conventional 2-valve V6s, although the 2 camshafts were positioned so close that they looked as if a twin-cam design. Thanks to the close proximity of the two cylinder banks, they could share a common cylinder head.
As a result, VR6 is not only smaller but also lighter than conventional V6. On the down side, its crankshaft is also constructed like that of a straight Each cylinder is served with its own crank pin and counter weights, and the crankshaft is supported on 7 main bearings.
In contrast, a V6 has half the number of crank pins and only 4 main bearings. This means the VR6 is no cheaper to build than a V6. You might wonder why it took 8 years to bring the VR6 a 4-valve head.
In fact, it had some technical difficulties to overcome. Technical Difficulties When I heard the rumour about the 24v VR6 about 2 years before its launch, the first question came into mind was: how to fit 4 camshafts into the small piece of cylinder head? It seemed virtually impossible, especially that some space has to be left for replacing spark plugs. If not having 4 camshafts, then it must be an SOHC design serving 4 valves per cylinder, just like many Japanese cars, say, Honda and Mitsubishi, did at the time.
However, SOHC 4-valve is not an ideal design. Firstly, it puts 3 or 4 elegant, narrow cam lobes to each cylinder, thus was relatively complex. For SOHC 4-valve, because the ideal position of the rocker arms for intake and exhaust are exactly the same, a small distance shift is introduced to one of them or both of them, thus results in the aforementioned drawback.
Right: the complex rocker arms. But the most important reason that makes SOHC 4-valve undesirable is that it does not allow the adoption of cam-phasing variable valve timing.
This results in little or no gain in performance. How did Volkswagen overcome these problems? Volkswagen's Solution Volkswagen's engineers solved the problems by introducing a revolutionary concept: Twin-camshaft per bank, one for intake, one for exhaust, but there are only 2 camshafts in total. Yes, believe your eyes. I might be the first one pointed out this secret. This photo was scanned from my favourite magazine when the engine was launched in I inspected it very hard and suddenly realized something unusual — look at the farther camshaft, its rocker arms press the valve springs, and the direction of springs project to the valves of a cylinder belonging to another bank!
I had never seen something like that before! Either way, VR6 symbolizes the joining of both the V6 and inline-6's benefits. The VR6 has a lot of advantages, the most notable being, its packaging.
The original design of the V6 engine was never engineered to be a stand-alone piece of automotive technology, it was specifically designed to get the 6-cylinder engine down to a size that would fit in any small-medium sized engine bay. Another beneficial aspect of these engines is their relative simplicity.
For any V-layout engine, it needs twice as much important stuff as an inline engine. It needs two cylinder heads, two valve trains, two fuel injector rails, two cams, and so on and so on. And there lies the genius of the VR6, it keeps that nice compact shape of a V6, but it only needs one cylinder head, one set of cams, and one of everything else, which equates to half as much pain to deal with when it breaks.
Speaking of breaking, the VR6 doesn't actually do it that often. It's balanced enough that its motions are balanced and natural, requiring fewer parts and counterweights, something that a V6 can't say for itself.
If you like small engines but dislike their shortage of power, the VR6 is a fantastic fit for your needs. It can make inline-4 turbo power while being the same size and naturally aspirated, which seems to be a dying art these days. An oil pressure control valve is integrated in the pump.
The one-piece cylinder block and crankcase is made from pearlitic grey cast iron with microalloyed steel microalloy. The cylinder bores are They are staggered, but overlap along the length of the engine block - to allow the engine to be shorter and more compact than conventional V6 engines. The centerline of the cylinders are also offset from the centerline of the crankshaft by The firing order is: 1, 5, 3, 6, 2, 4.
A European-spec 'ABV' 2. This version also had a free flowing 6 centimetres 2. It was also sold to Mercedes Benz for use in their vans, and designated as M This gave extra low-down torque, but was deleted before production on cost grounds, and was instead offered as an aftermarket option. In , with the introduction of the Volkswagen Golf Mk3 , a six-cylinder engine was available for the first time in a lower-midsize segment hatchback in Europe.
North America waited until to receive this engine; at the same time, the European model started to use the 2. This version, which had a 2. It was introduced in the Passat in , and the Golf and Bora in Further modifications were added to the design in , with the introduction of the valve 2. The new version was not available in the Passat as it was incompatible with the then-current generation's longitudinal engine layout , but was introduced as the range-topper in the Golf and Bora for European markets under engine codes AQP and AUE from The VR6 name was dropped as a commercial designation, [ citation needed ] and the 4WD system now renamed 4motion became standard on the V6 VR6 in Europe.
This new VR6 improved performance via updated camshafts , variable geometry intake manifold , an increased compression ratio of This engine option was available from In , the VR6 was enlarged to 3.
The Beetle RSi was the first production vehicle to use the 3. The then range-topping 3. In , the European market version of Volkswagen's sixth generation Passat, now with a transverse engine layout, went on sale with a revised version of the 3. For North America, the Passat received a new 3. These revised 3. This new 3.
The Passat R36 , available from early , received an uprated version of the 3. The first generation Porsche Cayenne base model is powered by a 3. The VR6 was developed before turbo technology helped make torquey, powerful four-cylinders with minimal lag and good reliability. In its day, that made the VR6 useful in performance cars, but now, it's an engine without much of a purpose.
In the VW Atlas, for example, the VR6 doesn't offer that much more torque than its four-cylinder companion, and its power band is narrower. The VR6 isn't totally dead, though. Bentley's W12 engine is basically two VR6s arranged in a V and connected to a common crank.
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