V-Twin and V-4 motors 3

[kradicke]

With the current focus on economy cars, both hybrids and high efficiency IC motors... why is there such a lack of focus on V-twin and (especially) V-4 motors in the auto industry? Of course, these are two engine configurations also missing from the Bosch Auto Bible.

What I'm hoping will follow is a discussion about the pros and cons of such motors.

Thanks!

Kai

 

[automatic2]

No clear demand from consumers for such a tooling investment.

 

[evelrod]

I can only guess at the reason that V4's are no longer being produced in a couple of Euro cars. Probably cost and lack of demand. The V4 sprint and midget engines of the '60's (1/2 SBC and Pontiacs, Mickey Thompson, Ansen among others) died because they were a very expensive fad replaced at the time by VW and Cosworth/Vega and other engines that were eaiser to build. I see no reason to have a V4 in an auto aside the novelty!

Rod

 

[patprimmer]

But isn't the VW a 180 deg V ;-) Regards
pat

 

[GregLocock]

V4s have horrible balance issues, although I'm not too sure if they are as bad as those from an I3 of the same capacity.

V2s have even more horrible refinement issues.

I hope someone is working on a good opposed twin, probably turbocharged.

Cheers

Greg Locock

 

[iaguy]

Greg, I have worked with an I3 before and it was very well balanced. I have not done engine balancing since the late sixties, but I remember that 3s and 6s were very easy to balance. Do I not correctly remember?

 

[GregLocock]

Well we might mean different things by balance. If you mean first order imbalance then I agree. An I3 has an inherent rocking couple at 2nd order because the non sinusoidal motion of the pistons at each end of the crank are 180 degrees out of phase. This makes it a complete bear to mount in the car, since this force is very large and always present.

Sorry if I confused you, this isn't stricly balance as such, I realise, we just call it a balance issue. Really its an inertia issue!
Cheers

Greg Locock

 

[mranlet]

the VW motor <i>was</i> a 180 degree (or &quot;flat&quot configuration. these motors were incredably simple to build, which is part of the reason for their success.

As for modern 4-cyl v's, the closest well-designed thing i can think of is the Subaru motors... The EJ and EH families employ horizontally opposed banks of 2 cylinders each. Subaru calls them &quot;H-4&quot;s and they can produce some impressive power and torque (Cusco races a 2.2L 600+hp Turbo'd Impreza in the JGTC over in Japan). There has also been H-6's such as the motor from the good 'ole 3.0L SVX, which is reincarnated in the Legacy H-6. I vaguely remember some statements from when the SVX was in production to battle against cars like the Mutsu 3000GT and Nissan 300ZX, where tuners had gotten the H-6's up to power ranges close to 1000.

But, to halt my rambling, one problem with the horizontally opposed engines is that any detonation can put you out of action completely. Also, the opposed engines don't get the mileage per gallon that inline's do for some reason. Another possible drawback for the lack of commercial use is that manufacturers may not feel that the engine tone is as appealing as an inline: an I-4 sounds like half of a V-8, while a H or V-4 sounds like two 2-cylinder engines, despite the exhaust scavenging X-pipe.

I hope that was at least entertaining, if not helpful to your querry...
-MR

 

[GregLocock]

Are you ignoring the Porsche flat sixes for a reason? Don't Lancia still build flat fours?

Why do you say that det kills flat engines in particular? I'd have thought the lubrication /wear problems were more significant, but I guess in the context of an engine a 1g 'force' is pretty small beer. They might be touch less efficient because they have more water jacket exposed, but that's no worse than a V engine with the same number of cylinders.

Incidentally an I4 does not sound like half a V8, at least to my ears.
Cheers

Greg Locock

 

[NickB]

Posted by Greg Locock: Incidentally an I4 does not sound like half a V8, at least to my ears.

In most cases i agree, but my Talon (2.0L I4 turbo) has a big lumpy cam, a 3&quot; exhaust, and when it's idling just a touch lean, it sounds like a mercruiser 350 exhausting underwater It doesn't sound like a V8 when it's under boost at high rpm though.

 

[patprimmer]

I was only kidding about the 180 deg &quot;V&quot;, hence the smiley with the wink.

I see no real reason why flat engines will use more fuel, other than there are 4 rather than 2 end cylinders which could give a slightly greater heat loss as is also the case with a &quot;V&quot; configuration, as stated by Greg.

In fact, going back to carburetored engines, provided at least 2 carbies were used, the direct downward fuel/air path allowed for minimum accellerator pump shot size, enhanceing fuel efficiency.

The main reasons I see for flat engines not being more popular are related to:-
The high overall width re avaliable space between suspension components.
The extra cost of manufacturing two blocks and heads vs an inline engine (more parts and more difficult assembly).
Capital already invested in tooling for existing, popular layouts.
Ground clearance and exhaust system routing problems.

Finally, my VW's with equal length, 4:1, long tuck under tail pipe exhaust and twin twin choke webbers, and 310 deg cams didn't sound anything like half a V8. Regards
pat

 

[evelrod]

Ok there Greg. If you want your I4 to sound like 1/2 V8(???) you must use a 3&quot; exhaust system that exits underwater!!!
Pat---Just put the whole Vdub underwater and call it a U-boat!

I have had the opportunity to see several configurations of 1/2 V8's---SBC's split into a V4 and split down the middle into a slant I4 (also a Pontiac and a turbocharged [oem] International Scout) in both midget racing and off road racing and they sounded pretty much like 1/2 V8 should---ie---JUST LIKE A FOUR BANGER! After all, what IS a 1/2 V8?

Rod

 

[patprimmer]

OK Rod
Touche Regards
pat

 

[patprimmer]

Mranlet
Air cooled VW's were not easy to build. You had 2 crankcases, 4 cylinder blocks and 2 cylinder heads to machine, align and fit with appropriate clearances, alignment and sealing, and the crankcases on which it is all based were not all that stable. The centre main web was prone to move around, as were the cylinder seating surfaces.
Light weight and low centre of gravity, ease of modification (no water jackets to limit maching and welding)and lack of heavy and or fragile and vulnerable ancillaries like a radiator and water pump were it's main benifits, at least in my opinion, but they are only a blast from the past now, and quite irrelevant to the original thread Regards
pat

 

[LadaTrouble]

There was a lot of tin ware to remove before you could find an engine too.Subarus are not easy either,pushing gudgeon pins in through holes in the block,and all flat engines need to be removed before any major work can be done,one of my main resons for giving up on the VW.

 

[PJGD]

I have to admit up front that I am a strong supporter of horizontal opposition; it has got a lot going for it and I wish there were more such engines available.

I agree with some of the things that Pat and others have cited above: I think that flat engines probably are more expensive to build, especially if a split crankcase is used (NB, the Alfa-sud engine had a one-piece crankcase), and this point alone means that it stands little chance in any company run by bean-counters.

I also agree that the greater engine width means that it requires an engine bay and suspension attachment points designed for it. This fact may mitigate against the popular concept of offering one platform with several engine options, unless of course you have several boxer engines you can offer!

They do however offer several advantages: In terms of form factor, they are short in length and relatively low in height, so they go well with design concepts where you want to minimise the engine compartment and maximise the passenger compartment. Typically, if front mounted, they do not encroach on the footwell area, and can be made &quot;crash-friendly&quot; by sliding under the floorpan in a frontal collision.

Considering only 4-cylinder engines for the moment, I have noticed that Lanchester balance shafts tend to be applied to in-line engines at around the 2.2 Litre capacity, whereas the better inherent balance of flat engines permits satisfactory NVH to at least 2.5 Litres. I would think that this would be an offsetting cost factor.

I see no reason why ground clearance should be a negative factor against horizontally-opposed engines. It is certainly not the case for the Jowett Javelin and Jupiter. Further, the exhaust sound is unique and much more interesting than a typical 4-in-line engine. The 1.5 Litre Jowett engine also sounds different from the VW, and I am guessing that the firing order is different. For the Javelin and Jupiter it is: 1423, what is it for the VW?

PJGD

 

[GregLocock]

Your argument about balancer shafts is an extremely good one - they are the only practical way to get an I4 up to an acceptable sound quality, and they are expensive, heavy and create friction.

One disadvantage with an H4 is that you need enough width to cover two cylinder heads - and modern cylinder heads are extremely deep. However we are presumably talking about future trends, and rationally designed (and specified) engines, in which case a 2 valve head makes sense, since the reality is that torque at mid range is what the customer uses most of the time, unless he has a CVT, and a 2 valve head is OK for that. Cheers

Greg Locock

 

[TheSilverBullet]

I've been wondering this question for some time now. I believe this thread has answered most of my questions.

Has there been a manufacturer to build a transversally mounted flat engine (front wheel drive) layout? I imagine this would be a very difficult task and require much creative engineering.

Regards,
Rob

 

[EngJW]

How about the Subaru H4 and H6, overhead cam engines? I think they were longitudinally mounted however. Perhaps their width was comparable to a transversely mounted in-line 4.

John Woodward

 

[GraviMan]

Hows about this for a V engine?

http://ghlin2.greenhills.net/~apatter/beamer.html

Ok the original application is steam, but the epicyclic crank idea is sound. Ideally you also need a crankshaft balancer, but the thing is perfectly balanced in sinusoidal motion. Would need careful design to keep the mass down, and even so I doubt you would need an external flywheel!

I would imagine that this would be fantastic from the friction point of view too. If you use linear bearings on each side of the &quot;con rod&quot; then there will be no friction, and the generated side loads present no problem. No piston skirt either, so the ring may not have to scrape oil, and in any case will have less loading. Very compact.

One last point about V4 engines - You can't have smooth torque delivery unless they are two stroke (4-stroke V8 fires every 90 deg). This is the last advantage of this design, inlet ports at the base of the cylinder will not suffer undue wear. To my mind a set of exhaust valves at the cylinder top would ensure good scavenging. The real beauty is that if it is turbocharged, the exhaust valve timing could be mechanised to close after the inlet ports (varying with rpm and loading). This means that you could get very near to exhausting at the same pressure as the inlet - ideal for efficiency. Mind you I still like the idea of turbo generators.

The fuel of this engine? Well seeing as it a compact turbo 2-stroke designed for high efficiency: diesel naturally. Never said I was a petrol head! ;-)

Mart