Diesel design paradigm - V6 & V8 3

[IceStationZebra]

Just throwing out a question for discussion - Would it make sense to swap the intake and exhaust ports on a V6/V8 diesel engine? My thinking is that you put the turbo just above the flywheel and eliminate the convoluted exhaust plumbing. (see this picture for a relative location

http://www.just-auto.com/articleimagelist.aspx?ID=90659)

And then the intakes could routed to the outsides of the heads with no limitations with high temps. The heat from the exhaust wouldn't cook the things that bolt to the side of the engine or next to the engine in the engine bay.

I assume that this layout has been tried before, but curious if there are problems with this or just that the standard layout is too ingrained?

ISZ

 

[MikeHalloran]

Exhaust heat would cook the engine oil, valve cover gaskets, and clutch. The two exhaust manifolds would be radiating at each other, which may not do them any good. The hot sides of the heads would be radiating at each other, which surely wouldn't do them any good.

A turbo in that location, above the flywheel, would interfere with traditional body structure in a car or truck, or force you to move the engine forward, which is not usually a good thing.

Caterpillar adds a second turbo to a 1000HP marine inline six, mounted above the flywheel. It makes the exhaust plumbing considerably more complex, but uses space that is normally wasted on a boat, so the overall engine is relatively compact.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

Mike

The OP does not specify an application, but he does mention engine bay which implies it is not a stationary motor.

A cab over truck normally has the bell housing under or behind the drivers seat. This would leave room for the turbo there.

If the engine was over head cam or had an insulated valley cover, I don't see that much more temp going to the oil. With the outboard exhaust, the rocker box is directly opver the exhaust. With the inboard, it would be below and beside. I don't see a lot of difference.

Main problem will be lack of room between cabin floor and exhaust manifold, but if this was not a problem in the specific application, the idea would simplify exhaust routing and turbo location with shorter pipe lengths. If there was plenty of overhead clearance with ventilation at the top, the heat would actually escape easier.

The commercial and economic problems of a complete head, induction and exhaust system change for a small volume application is another matter which will probably make the idea unviable.

Regards

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[IceStationZebra]

I had no particular application in mind, just more of a "are we stuck in a rut" question. Being limited to "V" engines however defaults this discussion mainly to light-trucks, cars and some vocational trucks.

Packaging - Mike, look were the turbo is on the 7.3L and 6.0L powerstoke, between the last two cylinders.

Neutral
- I think that either way you run into heat issues which can be addressed.

Positive?
- Preservation of pre-turbo exhaust energy with the reduction in plumbing?
- Would it give better catalytic converter light-off at start-up?
- Better pulse scavaging with a common exhaust manifold?

Negative?
- Could you make an exhaust manifold that wouldn't crack due to thermal expansion?
- Would it grow too much between the heads and have leakage problems?

 

[MikeHalloran]

I wouldn't dream of bridging the heads with a shared central exhaust manifold. It would leak, or crack, or both, at least if made of cast iron, the traditional material.






Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

You would need an individual exhaust manifold on each head.

You would need twin turbos or a slip fit between the two manifolds prior to single turbo. The slip fit would at best be difficult to do and unreliable or leaky and probably very expensive. Maybe a stainless steel bellows.

The packaging problems listed by Mike will make it undoable in a normal front engine with cab behind firewall type layout.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Fabrico]

CAT and Detroit both had highway V-8's with turbos mounted in that location. Having exhaust in the back and the intake side facing forward made things quite simple. Both used a turbo with two exhaust inlets so the entire manifold-to-turbo plumbing consisted of almost nothing. Ultimately simple, but simplicity at the engine can cause headaches with the rest of the exhaust.

Even in turbo applications, intake plumbing is quite large so it is questionable that spacesaving or a reduction in convoluted plumbing would materialize from exhaust on top.
(Detroit=blue, CAT=yellow)

 

[MikeHalloran]

Note that both engines have the exhaust manifolds in the conventional position, radiating to the world and not each other, and there is a bellows between each exhaust manifold and the turbo, to allow all the pieces to grow without cracking each other.



Mike Halloran
Pembroke Pines, FL, USA

 

[SomptingGuy]

Nobody has mentioned fuelling yet. You'd need two common rails if the Vee was full of exhaust manifolding.

 

[IceStationZebra]

Thanks for the responses (and pics Fabrico). It sounds like everyone pretty much agrees that the plumbing would be at best a wash, and certainly not worth changing convention.

ISZ

 

[bentwings1]

I worked on very large stationary powerplants and they had "center" exhausts. These ran into a "y" then into the turbo mounted on the rear and on top of the motor. Simple exhaust piping. Air intake filters were mounted on side boxes. The intake manifolds to the ports were large aluminum castings connected with rubber boots. It was all pretty simple ...if anything on 5000-7000 cu in engines is simple. 45 pounds of boost too.

Probably the main advantage was that all the really hot items were up high and away from the engine. It was easy to vent as the heat went straight up away from the electronics and other items onthe engines.

99 Dodge CTD dually.