Information needed: Pros and Cons of an I-line engine vs. a V-engine. TIA.

A V engine is shorter. More than that and more information is needed.


There are trade offs in every design and to discuss those things like straight eight and V eight need to be compared.

 

Two words:

Packaging

Balance

All depends what you want to do...

 

Inline engines usually have more torque. Because they are a taller engine, they have a longer stroke, which produces more torque usually. There are alot of 'for and against'. So it all depends on the application or what the car manuifacturer wants to use/build. Ford here in Aus have always used the inline 6 clyinder since the 1st Aussie XM Ford Falcon back in 1963. The new 2006 Bf Ford Falcon still uses the inline 6cyl. GM/Holden here in Aus have been using the Buick V6 since the VN Commodore days back in 1988. They have all been V6 engines since then. So it all depends mate.

 

An inline 6 or 8 tends to be very smooth and torquey but in very high output situations don't like to rev as high potentially. Typically have a higher center of gravity and a higher over all weight. I personally like inline 6's because the sound cool and can be so smooth. V6s can rev to the moon if needed, are light, have a lower cg and can be put in a small space.

I cannot say why BMW has stuck with the inline design. It is typically favored by more luxury oriented cars.

 

An inline 6 engine is smoother and more efficient than a V6 design, however, it is longer and hence used in larger car applications where packaging is not as big an issue.

 

If you look back in history, the V engines really came about in the auto industry from trying to get a larger engine into the same space a smaller one had resided. Ford was able, with thier flat head V-8, to put that engine into a car that basically already existed and increase power by quite a margin over thier 4 cylinder engine. It also has the advantage of low height, so that packaging it between the front wheels, allows the hood line to ride lower, as per the Corvette for example. Another advantage, is that by siamesing two inline engines side to side, say for example a V-8, the block becomes much lighter than an inline 8 would be, ditto the crankshaft, and the engine is now even stronger.

Packard, Cadillac, and a few others, used V-12's and V-16's for some of those reasons, but also for smoothness in that giant luxury car age. But when you see these, they are very narrow engines, with the Cadillac V-16 looking almost like an inline engine, very long and narrow. They wanted that tall and narrow radiator with that long hood to be a symbol of strength and power, and the motor helped to sell that sense. But in reality most were very underpowered crude low compression engines and they really needed those blowers to make them do anything.

Enzo Ferrari is reported to have seen a Packard V-12, and instantly could see its benifits in motor racing, with the ability to have a larger displacement engine of smaller size, with the added inherent smoothness. I think that smoothness was needed back then probably most of all, as many engines were still rather rough in thier mounting and the chassis were also rough. Smoothness would have helped a racing car stay togther longer, as well as be less fatiguing on a driver. But also, spreading out to 12 cylinders widened the power band, making the motor more tractable down at low speed, while delivering that train like pull we hear about so often as it wound out, and providing marginally more peak power over other engines, at least up until modern times. I think much has been written that Ferrari was a genius in seeing and taking advantage of the V-12.

 

A lot of interesting information has been presented. I have a couple of additional comments:

First, it depends on the number of cylinders. If I remember correctly a straight 6 is an inherently balanced engine with no shakes or rolls per cycle. The V12 is just two striaght 6s so it too is balanced. Again if I remember correctly the V8 has one roll per cycle, the I4 has one shake and one roll, and the V6 is a nightmare. This is why Mitsubishi developed the balancing shafts for the I4 and V6 engines. I have not looked this up to verify and am relying on 20+ years of memory.

Second, one reason that the strainght 8 was abandoned is crankshaft wind-up. As engine torque increased, a situation developed where the crank would twist under high loads, causing timing differences between the front and back pistons, but not the camshafts. This is less than ideal.

 

What I remembered on the above was about the same thing, except that I had been led to believe that a V6 at either 60 or 120 bank had only the secondary imbalance and so was superior to an inline four. A 180 degree V6 I.E. like a Porsche is completely balanced inherently like an inline. This book also said a flat four like a Vdub has only the secondary and so is also superior to an inline four.

There was also some complicated conditions on a V8; it had to have a four plane crank, be at 90 bank angle, and have crank balance weights, but could then be inherently balanced. Flat plane V8, like a F355, I think had a balance issue...surely somebody else will set us straight!

 

Straight 6's run cooler, or require less internally designed heat transfer surfaces... Because of a Higher surface to volume ratio.

 

The five cylinder diesel. Now there was an engine with a balance problem. I recall the first time I seen one bouncing all over under the hood of a Mercedes. I couldnt believe how much it bounced and rocked.

But I was thinking about engines, and Ferrari especially. The V-8 with a flat crank is truly 2 four cylinder engines siamesed together running 90 degrees out of phase. One could say they "harmonise" with each other. My experience with V-12's has been primarily with Jaguars, but they were always so quiet and muffled you could hear almost nothing. But I have listened to Ferrari's, and its odd how much they sound like a six cylinder. As odd as how much more the V-8 engine sounds like a four. Not exactly, but they sound more like those engines than anything else, just lots smoother. So, I was curious if you guys who have been around V-12 Ferrari's can comment on this. Do they seem that way, like two six cylinder engines harmonizing together? Consider that with either a Ferrari 12 or 8, there are always two cylinders at TDC on one bank at a time, followed by the other bank. On both engine types, it alternates fire pulses from bank to bank.

 

I too have noticed a big difference in Ferrari 12 vs Jaguar 12 vs Aston Martin - Ferrari being much more agressive sounding. Still, I wonder how much of this is intake and exhaust design & tuning.

For sure, the flat plane V8 has a unique sound, and seems a little "buzzy" to me.

I once read that the Boxer (and probably the TR, I guess) were not truly a Boxer design...i.e. each opposed piston was not on a 180 opposed crank plane but was instead shared a plane. Porsche 911 (and even Corvairs and most aircraft) flat sixes are real boxers in this sense - wonder if that could make a sound difference?

I would guess this all depends at least as much on the exhast system (or lack thereof) than on the cylinder configuration...but I must say that since I read that book on the balance issue as a teenager I have tried to stay with the inherently balanced engine types. Maybe this is partly why I want a Ferrari V12 so much? Or, could it be because I actually owned one of those 5 cylinder Mercedes diesels in the early 1980s as a family car? Seriously - I tend to shy away from flat crank V8s or V10 types for these balance reasons.

James

 

Google straight engines wikipedia and check out all types of engines and their applications.

 

Lexus used a straight 6 because BMW did, smoothness and sound. If you have a long hood you can get away with a S6.

BMW going V8 in next M3.

How about V10's!!! to me makes no sense other than packaging in an F1 car - but in a road car WHY!? - obviously marketing led - shame F1 has scrapped them now!

 

Chrysler went to a V10 because (I understand) they had lost the tooling for their B and RB Blocks and wanted a larger displacement engine for trucks. This way they could use much of the tooling and parts from the LA engines. Their V10 is a 360 with two more cylinders. The Viper engine was an outgrowth if the pick up engine project.

GM did the opposite with the 4.3 Liter V6, it is a 350 with two cylinders missing. This is why they ended up with a 90 degree V6.

These are compromise engines. The work very well but their inherent design flaws have to be compensated for.

 

So true! A 250 driven in anger sounds just like a Torana GTR XU1 - early 70's Aussie car with a hot straight 6. I only realised the similarity in sound after someone told me, but since then, I can't help but hear a Torana when I see a 250

 

yes, exactly.

 

FROM FERRARI 360 SP automobilia (2000) "The V8 with 180 degree crankshaft which permits the use of fuel and exaust systems similar to those for two 4-cylinder engines, is rarely used on road cars,since it prevents the elimination of the vibrations due to second order imbalanced forces. This crankshaft is universally used in V-8 racing engines,however, because the pulsations in the fuel and exaust system piping can be better exploited, determining the volumetric effciency of the engine and thus its power". That's what it said!

 

FROM ROAD AND TRACK OCT. 1994 "The high output is due to 1- nearly straight intake ports combined with racing type trumpets to suck air from two large airboxes 2- titanium connecting rods reducing recipicating mass. 3- 5 valves per cylinder allowing optimal breathing. 4- A flat crank allowing for optimum exaust tuning, not possible wih a 90 degree crank. Sophisticated engine mounts effctively make the resulting vibrations go unnoticed." FROM R&T 2002 "The shriek at high rpm's (like a wildcat cornered by a pack of dogs) is due to the 5 valves, a 2 path exaust system and the firing order necessitated by a flat crank". I especially like the wildcat reference.

 

Is'nt most inline 6 or 8 use only one cyl. head and V's uses two?

 

No. Some industrial engines have individual cylinder heads for each cylinder. Others build various engines using two cylinder cylinder heads, others using four cylinder cylinder heads, etc..

A good example are the old Detroit diesels. They made series engines, where the basic design centered around a particular displacement "series" cyclinder. They made a 53 series, a 71 series, a 92, and a 149, possibly others. These were cylinders rated by cubic inch, so the 71 series had a individual cylinder displacement of 71 cubic inch. They made engines of one cylinder, two, three, four, six, eight, twelve, and sixteen, in both inline and V configuration, using cylinder heads of varying numbers. The V-8's used two four cylinder heads, the V-12's used two six cylinder heads, the V-16 used four four cylinder heads.

I believe the early Alfa straight eights were comprised of two four cylinder blocks and heads, using a common crankshaft. I believe also that Enzo Ferrari's first car, the 812, was simular.

 

The BMW inline 6s are the best engines in the world IMHO...while my current M5 has a V10, I sure miss my old e34 M5 with its beautiful inline 6...

 

I had always heard Chrysler had to agree to not make any more big blocks as a condition of the bailout. Hence, no more big blocks, you stretch a small block and get more displacement and more power.

 

I had not heard that, in fact they have reintroduced the 426 HEMI as a crate engine. The 426 HEMI is basically an RB but they retained ownership of that specific engine. I also understand that they were seriously considering the 426 HEMI as the engine for the Viper. What I heard is they sold the design of the B and RB (essentially the 383 and 440 designs) and the tooling was lost by the purchaser at some point.

I do not have any secret connections but this is what I understand.