Chevrolet Speed -- Concept

[Drew Dowdell]

The balance is bad in Audis, but in other setups, not so much. With a V4, in this setup, you could still have the engine mostly aft of the front wheels. In the intrepid, there doesn't seem to be any more footwell intrusion than any other FWD car.

It still does not answer WHY the set up has bad balance. Is it harmonic (NVH) or stability or mechanical?

In the Audi specifically, even though the engine is set up longitudinally, more than 90% of the drive-train weight is forward of the wheel center line. In the case of an Audi V8, that means there is more engine ahead of the front wheel center line than any transverse setup might have. (i.e. an A8L has more engine in front of the wheels than a DTS). The whole reason SMK beats on American FWD cars is because of the nose heavy balance characteristics (while he conveniently ignores Audi). For balance reasons, you want to push the weight as close to the center of the car as possible.

In the case of the Toronado's setup, you can push the engine as far back as you want. It's a more compact setup than what Audi is doing.

[G. David Felt]

Which totally makes sense for what you are talking about Drew with a V4 FWD solution which based on your drawing above would still have the engine and tranny sitting mostly behind the front wheels.

[balthazar]

^ Doesn't have to be- looks to be HydraMatic centered the engine & built the case to accommodate the axle shafts. There may well be room to design a shorter case and come closer to centering a V4... (tho I might prefer the shorter nose approach).

[Z-06]

A longitudinal V4 provides a FWD platform a leverage to push the engine behind the driveshaft. Thus, provides a stable structure and mechanically balanced FWD platform. It will also be harmonically balanced compared to a transverse V6, but more or less a wash compared with a transverse naturally aspirated inline 4.

You have to understand the history behind the transverse FWD vehicles. Most of them were from Japanese/European manufacturers where there was a need to fit 3/4 cylinder engines in the bays of smaller cars, which did not facilitate enough wiggle room for engines to be longitudinal.

The modern FWD trend is to have as short overhangs as possible and push the engine as far back as possible. Also, 4 cylinders with some kind of force induction is becoming a norm in cars. In that setup, transverse FWD 4 cylinder suddenly becomes less balanced, because you have turbo sitting on one side of the engine. A longitudinal V4 with short overhangs is a plausibility in vehicles similar or larger than a Cruze.

[G. David Felt]

It would be great to see a mock up design drawing of a Turbo or Supercharged V4 FWD solution as well as RWD solution.

I know you have the large fly wheel and torque converter, but I have always wondered why you have to have such a large bell type housing. Why not curve it to be more bowl shape and then spread out the gear system so you have like a fat cigar shaped tranny which would allow you to loose the large opening on a firewall and spread the tranny down the RWD tunnel.

I personally think Transmissions could be better packaged than in a big bulky Bell shaped current package.

[Drew Dowdell]

They can be. Most transverse fwd transmissions are quite compact.

[dwightlooi]

The oldsmobile transmission (which I am not familiar with) looks like a transverse transmission with a 90 degree diffferential mounting in the engine's oil pan area. The will make a longitudinal engine layout in a FWD application less nose heavy by reducing powertrain weight which overhangs the front axle. However this is not the layout of any existing transmission and using this layout will require a new transmission design -- I was referring to using a V4 in a FWD application using existing transmissions.

If you are to design a dedicated transmission, the more interesting thing to do -- from a balance standpoint -- is actually to take the conventional VW/Audi or Subaru style tranny and install it backwards. In otherwords, the engine is completely behind the front axle with the transmission sticking out the front. Mechanically, it is relatively easy to do since all you really need to change is the side differential input gear engages the output shaft (which reverses the direction of wheel rotation). This presents some challenges with regards to accessories serviceability since the pulleys, belts, AC compressor, water pump and alternator will be on the firewall side. But this isn't actually any worse than you see with mid engined cars and is something you can live with. Normally, such a layout will require that the front axle be pushed out away from the firewall or the engine won't fit. But, since we are dealing with a V4 the engine will actually fit within the extents of the wheel well so no such change is necessary. The transmission being in front may also intrude into traditional radiator spaces, but this can be accommodated by using a horizontal radiator and a vent channel in the hood (ala Corvette C6R).

[Drew Dowdell]

The oldsmobile transmission (which I am not familiar with) looks like a transverse transmission with a 90 degree diffferential mounting in the engine's oil pan area. The will make a longitudinal engine layout in a FWD application less nose heavy by reducing powertrain weight which overhangs the front axle. However this is not the layout of any existing transmission and using this layout will require a new transmission design -- I was referring to using a V4 in a FWD application using existing transmissions.

It was actually a standard RWD transmission (A THM400 in fact) turned 180 degrees and chopped off just aft of the torque converter. The torque converter stays with the engine and drives the transmission via a nylon cog/steel chain setup that requires no idler pulley. The FWD version, called THM425, shared lots of internal components with its RWD brother.