Superiority of different engine designs

[perky_intnl]

There are some pretty clever mechanical people out there. I have read some of there answers here in this forum.
I want to have somebody explain the differences in design between for example an inline 6 cylinder engine and a V6 or V8 engine, (or even V10). Ultimately I want tank tough, last forever durability & reliability.
Let me clarify why I want this explanation.
I have 1994 Dodge Ram with the 5.9 Cummins Diesel engine.
It is time to replace this truck, it has well over 400,000 kilometers, 250,000 miles.
I would love to have a truck with the Common Rail Direct Injection fuel pump system, however only the Duramax offers that, and I am not going to spend that kind of money for a late model nearly new truck.
So my options are the newer Dodge (either late 12V or early 24V) or the Power Stroke, approximately year 1998, 1999.
I am baffled at how the much smaller engine (the Cummins) can produce similar power and torque, and in many cases with better mileage, when compared with the Ford Power Stroke, which has approximately 20% more displacement. Even comparing the performance after everything possible has been done (Banks Turbo Kits, Mufflers, TLC etc) it seems that it is possible to get bigger performance boosts from the Cummins than the PowerStroke. So that seems to indicate some inherent strengths in the inline 6 design.
Now we get to the really grey areas for me, the difference in the Crankshaft length, and mass, moments of inertia, how many bearing are supporting it, does the extra mass contribute something to the torque potential, overhead valve designs.
I try and equate it with the old John Deere Single and 2 cylinder tractors that just chugged away but had a massive flywheel that allowed them to work forever.
There must be some influence from the increased surface area, ( The surface area, perimeter of rectangle will be larger than a square of the same surface area) possibly the distance that the various fluids (oil and coolant) have to travel etc, etc.

Ultimately this question will also apply to my next problem which is to try and determine whether I am better off with one 502 (8.2 liter) GM engine in my boat, or 2 Wankel rotary marine engines each producing 240 HP, and only 1.3 liters displacement each, and the two of them together weigh 300 lbs less than one 502.

[Holyterror]

Geez, this isn't the sort of thing I should try to tackle at 4 A.M., but here goes...

Trucks, and diesels especially, are not my area of expertise. I can, however, tell you plenty about engine configurations.

The Inline 6 is a terrific engine design. Despite the fact that auto manufacturers prefer the V6's smaller size, it's not really that much bigger and is intrinsically superior. The reason the I6 is so great is that it's completely balanced by nature. Vertical and transverse vibrations are cancelled out completely. This eliminates the need for a balancer. Compare that to a big truck V6. Since it's a big motor, I'll assume it's a 90 degree (possibly a scaled-down V8 even). It's going to need a balancer. There goes some of your power and efficiency right there. Now let's look at the valvetrain. The V6 has twice as much of just about everything because it's split into two banks. Frictional losses from the extra camshaft outweigh the V6's only component advantage, 4 main bearings versus the I6's 7.

That's it in a nutshell, without resorting to complicated math (which I don't particularly like). The only real reason to go for a V6 is its smaller size. When packaging isn't an issue, you'll see the I6 used much more often. That's why when Rolls-Royce and Bugatti didn't want to put a V12 in a certain car, they turned to the I6. And you probably should too.

As for your boat, get the rotary engines. They'll serve you well, and with less demanding work than they would get in a car, they'll last forever. I won't get into why they're so nice, not in this post anyway.

[MaFi0s0]

i always thought the V formation was better, the domestic companys here in australia like to put an emphisis on V6 and V8 here like there mad or something, then when some other company has an I6 they dont say inline they just say 3 litre or 6 cyinder not _inline_ 6

[Holyterror]

I don't know about Australia, but I know why they emphasize V motors in the U.S. For small cars, V6's are empasized versus 4-cylinders. And with trucks and SUVs, V8's are empasizde over V6's. In America, bigger equals better, so big displacement (and thus more cylinders) is a major selling point. The reason we don't hear much about inline motors is that there aren't many, aside from 4-bangers, which don't get much respect here (except among import fanatics like myself). I think that if somebody advertised an I6 car, nobody would know what it was. :smoker2:

[Someguy]

A straight 6 is a much better design then a V6 as Holyterror said. And as he said V6s are more popular because you can squeeze a V6 into pretty much the same space you can a I4. There really aren't that many cars that come in V6 flavors that don't have a I4 base model. Mustangs and Camaros being exceptions I guess. But Accords, Carollas, ect... A straight 6 is a bit harder to package, and less common since if you have enough room to fit a straight 6, then you probably have enough room to fit a V8, which another very well balanced design, hints why they are so popular with high dollar luxury cars. Even BMW which sells more straight 6s then anyone uses V8s in its really high end cars.

But anyway, I6s are hardly *new* to the American market. They were available in Mustangs and other Fords from the mid 60s to the late 70s. GM has a quite nice new one out for some of their SUVs now and probably other vehicles eventually.

As far as the Cummins vs. Powerstroke. The Cummins is actually an older style, simpler design, which actually works better.

[ivymike1031]

don't forget that the 4.0L engine used in Jeeps is an I-6... they're pretty common.

[A20A1]

I just hope nissan keeps the I-6 for the GTR insead of going to v-6.

or they can get funky and build a Quad - 4 like oldsmobile.

[SaabJohan]

Generally a smaller engine is a more effective engine.
Also the use of fewer cylinders means less suface area per volume, which mean a more effective engine.
But few cylinders have a problem with balance, also if the cylinders become very large this means a long flamepath, and that isn't good.
With balanceshafts you can make a engine with few cylinders more smooth (usually used in 4 cyl. engines).

A V configurated engine is compact, and also allow a short crankshaft, but the forces created by the pistons i a little diffrent (sideways). An inline engine is easy to make stable, usually there is one bearing per cylinder and one at the end. The number of bearings with a not too long crankshaft makes theese engines very durable. But the differences in durability between engines is rather because of construction, than construction type.

But since diffrent types of engines behave, and sound diffrent this is a "salething", because there is probably nothing you can't do with a inline four that you can do with a V12.

[flylwsi]

the reason the "smaller" dodge makes similar power is b/c the ford powerstroke is detuned...

by using the hypertech power programmer on a powerstroke, you can gain 50hp and 108tq. not bad. and that is just by changing computer tuning. the smaller dodges are apparently tuned a little more highly than the ford.

there is your answer to that one...

and on your wankels, im not quite sure where the info came from that a rotary runs forever, but they are subject to self detonation b/c of heat... that could be bad...

weight is big though... if you go with the wankels, they don't work as much, but they do get hotter. rotaries overheat easy. ask anyone w/ an rx7 that uses it for anything other than daily driving. and im sure a marine rotary is different, but that all depends on the cooling system YOU ultimately design for it...

i'm not sure i am quite on topic, but i think i said what i meant

[Steel]

dont forget the flat designs, are also really good too, no need to balance them and they produce a lot of power it seems. Or at least that's what Porsche and Subaru say.

[Holyterror]

Flat engines are perfectly balanced. In fact, the only way to make a perfectly balanced 4 cylinder is to make it flat. They also do not take up much space vertically, so they can be mounted low. However, they take up a lot of space horizontally, have more parts and are thus more expensive to make, and most auto makers don't think it is worth the trouble. Remember, if you design a platform for an I4 and later decide you want to put a V6 in it, no problem. But if you design one around a flat 4 and want to move up to a flat 6, it's a different story.

There are other perfectly balanced engine designs which carry none of the boxer configuration's disadvantages. Ferrari's flat 12s eventually gave way to V12s, for example. Porsche spares no expense in achieveing their corporate vision of the perfect automobile. Subaru isn't shooting to be the biggest manufacturer in the world, but to make safe, reliable cars that the discerning driver will favor. Their design philosophies do not revolve around keeping things bare bones cheap and selling as many units as possible.

I think it's pretty much set in stone that Nissan is going with a VQ-series engine for the GT-R, so hoping won't do much at this point. Try praying instead.

[Steel]

queeeeeestion - is it possible to transplant the v6 from a current pathfinder into a 93? cause mines gonna kick the bucket before long...

[flylwsi]

that depends on if you want to do it. anything is possible... yes is the answer. you just need the whole harness, ecu, and trans...