VR Engine displacement
VR Engine displacement
(OP)
Does anyone know what figure is quoted for the stroke (and therefore displacement) of a VR engine (e.g. a VW 2.8l VR6)? Is the stroke quoted as twice the crank throw or is it the measured stroke, taking into account the massive offset between the cylinder axis and crank centre-line.
- Steve





RE: VR Engine displacement
http:
Looks like the cylinders are angled to point ~ at the crank centerline, so 2X offset and measured stroke would be the same
RE: VR Engine displacement
- Steve
RE: VR Engine displacement
The crown moves 45mm from Tdc to Bdc.
The big pain with these is the fact that pistons need to be fitted with a special ring compressor as the rings meet the block deck at 75 degrees when inserting the piston to bore.
I made a turned tapered bush the size of bore and sliced at 75 degree's to aid fitting. Placed on deck the piston can be slid ito the tapered bush and into the cylinder without worry.
If you need further info on block structure let me know.
Brian.G
RE: VR Engine displacement
that would be a stroke of 45mm?
So the actual stroke is 90mm... what is the radial dimension of the crank throw - the distance between the crankpin axis and the main bearing axis (was thinking about calculating it, but didn't get around to it)?
RE: VR Engine displacement
RE: VR Engine displacement
RE: VR Engine displacement
- Steve
RE: VR Engine displacement
Brian.
RE: VR Engine displacement
RE: VR Engine displacement
Another thing about the vr6 is that the big end journals are offset by 22 degrees. Hence the exhaust note, Id know one a mile away.
RE: VR Engine displacement
I have a spreadsheet that can calculate the true stroke resolved to each °CA; however, what needs to also be known that's not always published is the piston-pin offset if there is any in order to get a correct calculation.
RE: VR Engine displacement
Seems that it'd play hell with piston position bank to bank if they were not!
RE: VR Engine displacement
If the piston tops are asymmetric as described above, then the only real disadvantage of pin offset would be that it would necessitate different piston part numbers for the two banks (because the crown slope is thrustward on one bank and the opposite way on the other bank, but you'll offset the pins uniformly to thrust).
RE: VR Engine displacement
http://bit.ly/aFxLBL
The above link to a page on the SSP document (there is no copyright mark, I checked) shows that the minor bank does indeed have a 12.5mm cylinder offset, but what is incredible is that the offset are on opposite sides of the crankshaft centerline (!!!), with the intersection point below said crankshaft centerline. This means that the motions of the left-minor bank will be slightly different than the right-minor bank!! This also means that the articulating angle of the connecting rods are different at given crank angles and, particularly close to TDC, in fact on opposite sides of the cylinder axis.
Given a 90.3mm stroke of the first-generation 2.8 VR6, 164mm con rod length, ±12.5mm cylinder offset and assumed zero piston-pin offset, maximum true stroke is 90.585mm. On the right bank with positive cylinder offset (toward the anti-thrust side) the maximum stroke length occurs at 186° CA (referenced to TDC), and the pistons' closest approach to true TDC occurs at +3°CA (0.0016mm below true TDC). On the left bank with negative cylinder offset, the same maximum stroke length of 90.585mm occurs at 174° CA and closest approach to true TDC occurs at -3°CA (also 0.0016mm below true TDC).
On another note, a slight piston pin offset (usually 0.5 to 2 percent of piston diameter) is introduced mainly for NVH purposes in order to smooth out the transition of the piston skirt position, which wants to stick to the anti-thrust side on the upward portion of the stroke and to the thrust side on the downward part.
Interesting stuff!
RE: VR Engine displacement
http://bit.ly/are5NC
RE: VR Engine displacement
- Steve
RE: VR Engine displacement
Displacement: http://bit.ly/aDqcPv
Velocity: http://bit.ly/bRyAmY
Acceleration: http://bit.ly/91Ri58
The velocity and acceleration curves my be flipped from what some people are used to because I've employed the convention that a downward stroke displacement is negative.
RE: VR Engine displacement
http://
RE: VR Engine displacement
They hand build these at the VW engine plant in Salzgitter, Germany. It's a very interesting factory and one people can and should tour if they get a chance.
RE: VR Engine displacement
I,ve been there. VW actually build a lot of diesel engines in that factory too. There is dedicated room for Bugatti engines. As I was told production target of Bugatti engines is 3 per week. They didn't let me inside the room, just watched eng. assembling through the glass.
These pics are from Cologne Auto Show last year though.
RE: VR Engine displacement
RE: VR Engine displacement
What's crazy about this engine is that different pistons are required on the one minor bank side than the other, since all the direct gasoline injectors are on the same side of the head and the bowl-in-piston must have the same relationship to the injector position and in-cylinder charge motion.
RE: VR Engine displacement
RE: VR Engine displacement
Ford, part of Ford Motor group, Chevy part of GM, two competing corps., im not quite seeing the comparison?
BTW big VAG fan and hoping to develop a twin charged 2.9 VR
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Audi redesigned their V-8 engine front end drive to shorten the engine so they would not be forced to use the VW W8 in an Audi. You will note that only the VW VR6 engine is used in any Audi models. The 4 cyl. and other engines are Audi designs, not VW and Audi is quick to tell you so.
I hope VW brings their twin-charger engine series to the U.S. The issue appears to be engine cost.
RE: VR Engine displacement
The Hybrid version of the VW Touareg/Audi Q7/Porsche Cayenne will all use use the 3.6 VR6 and not the any 90-degree V6 variant from Audi.
Yes, there's intense competition and even some conflict within the VW Group, like any inter-division rivalry within a large conglomerate, but it's not like GM/Ford. But having just typed this, I must qualify that statement: I have personally worked in a project in a Tier-1 supplier where Ford and GM collaborated on a 6-speed transverse automatic transmission. In development they were known by GM and Ford as X22F and 6F, respectively. In production the X22F followed the more familiar convention and became the Hydra-Matic 6T70. It was a pretty good collaboration. I was in many a conference call with engineers and managers from both companies simultaneously.
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When the dictate from Dr. Winterkorn or similar says you will use the 3.6L VR6 in the Q7 or the W8 in an Audi it is met with a lot of resistance.
Engineering groups at the same division are also very competitive. As an example the engine designers and development engineers at Ford U.S. 4-6-8 cyl. engines would not share ECU software strategies. They all insisted on their own unique ECU SW for personal more than professional reasons...
Anyway I'm sure there are unhappy campers at Audi when they are forced to use a VW engine design even though these engines tend to be good, reliable engines for the most part.