Diesel Snippets

I’m not totally sure what form GM’s passenger-car diesel engine for the US will take. It looks very much like it’ll be the 2.9 litre diesel engine that’ll be manufactured by Italy’s VM Motori. They already make a 3.0 litre diesel unit and it seems that this engine will be a derivation of that unit and will make a US debut in 2009.

It’s tipped that this engine will also be a possibility for the next Saab 9-5, too. This much we’ve heard before.

The reason for my hesitation at the beginning of the piece, is that I don’t know if this new piece from Motor Authority pertains to the development of that engine, or not. If so, then it sounds like the development is going well and the innovations should mean good things for the powerplant going forward:

The innovative engine works by reversing the flow of air and exhaust gases going in and out of the cylinder heads. This means that hot exhaust gasses can be transferred to a turbocharger in the gap between the cylinder banks. According to Automotive News, the result is the elimination of numerous parts and more efficient use of heat. This in turn leads to better fuel economy and performance as well as improved NVH and emissions levels.

Some of the parts the design eliminates include the intake manifold, heavy cast-iron exhaust manifolds and their associated parts such as gaskets, bolts, nuts, studs and most heat shields.

The picture they’ve used doesn’t reconcile to the VM Motori picture at all, so I’m wondering if they’ve just stuck up a photo of any old engine, or if this is an entirely different powerplant they’re talking about.

The numbers sound similar, though, so it’s a possibility.

thanks David W.


I’m not sure how new this is but Turbin got it in a newsletter from BSR just this week and if you TiD owners don’t know about it yet, then it’s worth reading about.

BSR have a PPC tuning kit for the 120hp and 150hp TiD engine. The one Turbin was reading about was the 150hp upgrade, which will take your TiD to 184hp and 412Nm of torque, which is a LOT of torque.

That’s a higher spec than the new TTiD. Well, until BSR get their hands on a TTiD, at least. The great thing about the TTiD is the dual exhaust, which makes the car sound unbelievably good when you’re driving it.

Anyway, if you’ve got the 150hp TiD and would like a little more poke, the BSR product page for the tuning kit is here.

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  1. In and out the same valves would be a huge leap, but this is the first I’ve heard of it. Is that what they’re talking about?
    Seems like it would have other penalties though…what about the engines with variable intake lengths?
    Also, is this technology limited to slower-turning diesels?
    That’s a lot of questions, any engineers out there?

  2. About the pictures. The VM Motori picture doesn’t show a turbo sitting between the banks, the Motor Authority picture does, as described. So my guess is that the Motor Authority pic is correct.
    About reversing the gases, don’t they just mean the intake and exhaust are on the same side of the bank, thus reversing the flow?

  3. Adam/Ted Y – put ‘reverse flow cylinder heads’ into Wikipedia to read the upside/downside of this principle.
    Swade – do not forget that VM Motori are 50% owned by GM with the other 50% owned by Penske, USA who are probably not involved directly with engine development. It is highly probable that joint projects are on-going between VM & GM.

  4. Thanks englishbob. Here’s what I found on Wikipedia to save time for those interested (if this is really what they’re talking about):
    “A reverse-flow cylinder head is a cylinder head that locates the intake and exhaust ports on the same side of the engine. The gasses can be thought to enter the cylinder-head and then change direction in order to exit the head. This is in contrast to the cross-flow cylinder-head design. This term is used for engines which have only one intake and one exhaust valve per cylinder.
    The reverse-flow design is accepted to be inferior to a cross-flow design in terms of ultimate engineering potential, however, the reverse-flow design has been shown to be a more practical and economical manufacturing proposition in turbo-charged applications (where the impeller and propeller must be close to both intake and exhaust). In a forced induction engine overly-large valves and “through flow” of gasses on cam overlap are not critical design features as under normally-aspirated conditions.
    The real problem is that of temperature. With the exhaust ports on the same side as the intake ports, the intake components and the incoming charge must absorb some of the heat, thus reducing volumetric efficiency.”

  5. From the article’s description, it sounds like the exhaust valves are inside the V, while the intake valves are outside.

    This makes sense in a turbocharged V engine, since you can put the turbo right next to the exhaust (saving a lot of tubing). The intake air has to go to the intercooler after the turbo, so it will need a lot of plumbing in either case.

    This idea is along the same lines as Saab’s asymetrical V6 turbo of the 90’s, where only one bank of exhaust feeds the turbo. Saab was trying to avoid running the exhaust from the rear bank around the engine to the turbo in the front.
    Other manufacturers use twin turbo’s (one per bank, as opposed to twin-sequential) to adress the same issue.

    Reverse-flow cylinder heads are where the intake and exhaust are on the same side. Most 70’s and 80’s 8v water-cooled VW’s were of this type.

  6. I’ve got the PPC upgrate boosting the 150hp to 184hp and 412Nm of torque. All I can say is WOW.
    The response of the car is fenomenal. Driving is even more a pleasure.

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