Can a VR6 be made into a TD? no... seriously

[Josh]

A vr6 converted to diesel, idi or tdi, is outrageous.  I can't believe this is even a question... what is this, the vortex?  

  -Josh

[lord_verminaard]

Well, a lot of people on the vortex dont understand why anyone bothers modifying a Diesel either.  I say, if he's got the stones to do it, then he should do it.  This forum has always been about changing the rules and pioneering new thinking.  Sounds like a perfectly reasonable question to me.  Do you think putting a Diesel in a Scirocco is an "outrageous" idea?

Brendan
84 Scirocco 8v
00 Camaro L36 M49

[myke_w]

A vr6 converted to diesel, idi or tdi, is outrageous.  I can't believe this is even a question... what is this, the vortex?  

  -Josh

Bwahaha! Awesome!

[fspGTD]

I really doubt the IDI VR6 idea is feasible as a head conversion project.  I don't see there being room amidst the network of intake and exhaust runners and water jacket to sink prechambers into the head. :?

It would take a lot of resources (the kind that only automotive OEMs have, or very wealthy racing team owners) to completely reengineer and manufacture from scratch a prototype cylinder head.

On the VR6 DI conversion idea - there are a few unique problems you'd need to solve that would likely make this very challenging.  I'm not talking about the necessary custom pistons, rods, and reground cam, which are solveable with adequate budget.  Adapting the injectors may prove challenging because I believe the TDI injectors are installed indexed and at a specific angle, and their injection pattern is designed to match that specific installation angle.  Their position and installation height would also have to match the combustion chamber perfectly to get good results.  If the sparkplug holes didn't happen to be in the right angle, you'd likely need different injectors.  If they aren't in a central position, all at the same angle in each of the 6 cylinders, you're going to have a very difficult time achieving a "well balanced", smooth running motor.

Unique challenge number #2: the TDI intake ports are designed to impart "swirl" characteristic to the air as it enters the chamber, to bring all the air to the injector spray nozzles so you're burning more than just burning the air that happens to be in front of the injector's orifices.  If you don't bring the air to the injector, you're going to get a lousy running diesel - smoking, low power, and low efficiency.  You would need to add some material (maybe through aluminum welding or metallic epoxy) to the runner to give it the necessary contour to impart swirling.  Perhaps you could just "eyeball" it and use a TDI's intake port shape as a guide?  But you might end up with improper or uneven swirl across the cylinders.  VW has means of testing the amount of swirl and to expect good results on your first try, you probably should too.

If you are still interested in these projects, you'll need to learn as much as you can about diesel engine design.  At minimum you should read every VW Diesel SAE paper and technical engineering document you can find.

[2383 GTD]

I read in an SAE paper (I cannot recall which) that the VR6 motor, was indeed designed in mind for use with the diesel cycle. A major problem with the combustion chamber design, from what I've read, is the wedge shaped quench area. This could be resolved with proper/custom wedge shaped pistons, with the enhanced Japanese style cloverleaf relief in the piston surface. It is possible VW has designs somewhere for these pistons, if they got that far in the development of the engine.

If there is indeed room for a swirl chamber within the head, this project could be possible in an IDI format.  A DI design would be easier in some aspects, but without strong swirl via bespoke inlet runners, would require great effort, as Jake mentioned.

As far as the IP, again from what I've read, the crankshaft has 120 degree throws, which is exactly what an inline six uses.  Therefore, the injection timing should be that of just about any inline six cylinder engine.  Drive for IP would be from the chain (possibly complex), or perhaps from the other end of the camshaft, like the VW inline six engine.

If you have the room, I suggest using the VW inline six that is used in VW LT vans, and Volvos, as it is a well proven, extremely strong design.

[Josh]

  Nah, a diesel in a Scirocco is cool.  It's a bolt-in conversion, basically.  

But for all the reasons listed and more, attempting to adapt a vr6 to run diesel is just plain crazy talk, I don't care how much money you've got to spend.

  IT's just NUTS!!  Sure, it's possible, but so is converting a rabbit into an aeroplane; although the latter is probably cheaper.

[Mechdonald]

Yeeesh - you would almost think I asked a stupid question or something  :lol:

I appreciate the helpful comments from the technical side.
I'm learning quite a bit on this forum about what is possible with IDI and TDI engines. (who would have thought you could make a M-TDI? - very neat)

Sometimes, not knowing that "you can't do that" allows you to look at the problem with fresh eyes and come up with a solution. I have to do that all the time in my job.

I wasn't sure if the VR6D question had ever been asked before on here.

[DieselMonkey]

I hate to put such a downer on this but where would you get a fuel injection pump to supply fuel for the correct firing order of the VR motor ? Where would you drive the pump ? (timing chain )

Driving it wouldnt be such a problem and tweeking it but the firing order would be the problem, and making fuel injecion lines. Machining the head for pre-chambers would be fun ! I work in the machine shop running CNC mills, this would be easy and probably not a big job getting IDI injectors into the head either but to be honest, you'd be better with a VR6 diesel with direct injection. It would take much more work to make an IDI.

I agree with the others, you would get much more power from a TDi or M-TDi in a nicer package and it would cost less also.....but then again - its all been done before hasnt it !

Best of luck. DM

[Josh]

Mechdonald,

  I apologize for being harsh earlier; I've no right to dump on anybody's questions.  I was just in a bad mood and took it out on the board.  Sorry, All!  I like the open nature of the board, and hope it will remain a safe place to ask questions, regardless of their relative outrageousness.  

  -Josh

[lesharoturbo]

As for a timng pump that has the correct firning order, you SHOULD be able to determine the firing order of the pump and match it to the engine.  All yo have to do is reroute the lines to where they would need to go.  Provided you have a pump for a 6 cylinder   .

Running the pump off a timing chain shouldn't be a real issue, but maybe you can convert to a belt system.

Bernie

[Josh]

You've got to reroute the lines keeping the lengths of the tubes equal, of course.

[Mechdonald]

Josh - that's OK, I know all about being in bad moods.

Good point brought up about the pump timing. Does the VR6 fire evenly?
I was thinking of a pump off the Volvo inline 6 that naturally would have an even firing order. If the VR6 does NOT fire evenly then....there goes that idea.

I checked out a book I have in the basement last night about VW history. There is a little blurb in there about when the VR6 was introduced - VW claimed that 24V and Diesel versions were possible... the rumour is true to a point.

[lord_verminaard]

Like 2383 GTD said earlier:  

"As far as the IP, again from what I've read, the crankshaft has 120 degree throws, which is exactly what an inline six uses. Therefore, the injection timing should be that of just about any inline six cylinder engine. Drive for IP would be from the chain (possibly complex), or perhaps from the other end of the camshaft, like the VW inline six engine."

So there ya go.  Either the volvo pump or even a cummins 6BT pump would work.  Making the lines would be easy, just figure out how long you need, then buy some pre-made straight lines with fittings all in the same length and bend them to fit.  Like others have said, it would be head mods and figuring out a way to drive the IP that would be the hard stuff.

Brendan
84 Scirocco 8v
00 Camaro L36 M49

[lesharoturbo]

Look at this cutaway of the VR6: About halfway down the page

http://www.me.umn.edu/~byronr/vw/gti_picts.html

Notice the position of the plug related to the combustion chamber and piston.

With the proper pistons (TDI style) and injectors in the plug holes, I think you may be able to get the swirl necessary to efficiently combust your diesel.

Bernie

[Mechdonald]

thanks for the link. that's the cutaway I've seen before - the plug is off to the side as needed.

Like many have said and somewhat verified - VW has said themselves that a diesel version is possible. I wonder how much work they did on a diesel version.

Just another question about pump timing:
If the crank is 120 degrees like a straight 6 but the V angle is 15 - wouldn't that give you DIFFERENT timing then the straight 6?

I think it would - if you make the V angle more pronounced (say 60 degrees) you can visualize it better.

Is that what gives the VR6 its neat sound? - a slightly uneven firing?