Engine Questions.

[Justin]

Something I’ve been pondering that maybe one of you here can assist me with…

Are inline engines inherently longer-lasting than “V” engines given same quality of components?

Which engine designs are “naturally” balanced?

Which is better: I-4 or I-5 for longevity?

Edit - I'm use to working on older American V-8's in pickups, and changing spark plugs and routing the associated wires isn't exactly the most fun way to spend an afternoon.

Hasn't most O.E.M's gone to a "coil-on-plug" design? How short are "modern" plug wires?

[ August 20, 2004, 10:21 AM: Message edited by: Justin ]

 

[Kestas]

With respect to naturally balanced engines, I've read somewhere that V-12 is the best, followed by I-6. Don't know what the rest of the pecking order is, I believe V-8 is better than V-6. And I know I-4s aren't all that great and can be a problem over roughly 2.5L because of the internal reciprocating mass. That's when designers start considering balance shafts for four bangers.

The coil on plug design gets engines away from distributors, which have been a maintenance and repair problem in the past

 

[labman]

I don't think longevity is much of an issue in passenger car engines any more. Even the notoriously inherently unbalanced I4's are often still in great shape long after the rest of the car falls apart. Same for the 90 degree V-6's. I don't think I can even kill the 4 in my 77 LUV truck, which certainly is not a more expensive one. It only has 124 K on it, but nearly all engine killing cold starts and short trips. It and my wife both survived a trip across town with no oil early in its life. It still has never rattled or knocked again since I refilled it with oil that time. Most of its life it has gotten 6 quarts of fresh Pennzoil every 3 months whether it needed it or not.

Took one of my rare trips out of town in it yesterday, 80 degrees, Pennzoil Conventional 5w30, running 70-75 on the interstate. After about a half hour, the oil pressure dropped to about 50 psi from 80 psi and held the rest of the trip.

One advantage of the straight configuration is the simplicity and low parts count of the valve gear in my trucks SOHC design. There is nothing between the cam and valve except a lever with an adjustment on one end. No lifters, no push rods. It simply uses a slightly longer timing chain than a OHV would.

Medium and heavy trucks are another matter. Still GM hasn't built an I6 for a long time. Even UPS had to give up and convert to the V-6. They do keep their trucks going, through several engines. Oops, excuse me ''Package cars''.

 

[47HO]

One advantage that inline engines have over the V configuration with the same number of cylinders is that the loads on the crank are spread out among more main bearings on the longer crankshaft.

 

[Motorbike]

Most of the better inline sixes also have 7 main bearing saddles that will help minimize crank deflection .

There is quite some difference in the toughness of an Izuzu 4 cylinder gas motor's lower end and a Toyota 22R for example .

3 main bearing saddles vs 5 for the Toyota

 

[Justin]

Motorbike...you once again have hit the figurative nail on the head!

Besides big American V-8's, I've spent a fair amount of time around the Toyota 22R engine in the small Toyota (pre Tacoma) pickup.

Would you know how the new 2.8 and 3.5 liter GM engines compare to this engine in regards to longevity/durability?

 

[labman]

I don't know how many main bearings the I-8's GM built in the late 40's had, but crankshaft flexing was a problem. The shorter V cranks don't need as much support.

 

[darrenc]

Inline engines have a design and absolute durability advantage over vee configurations due to their extra main bearings. An I-4 has 5 mains, an I-5 has 6 mains, and an I-6 has 7 mains. A V8, for example has 5 mains like an I-4. After all, a V8 is but two I-4s set parallel to each other in at a vee angle sharing a common crank. This is one of the reasons I-6 motors (like the Jeep 4.0) last so darn long. That said, there is no substitute for good design and build qualities.

Horizontally opposed engines (boxer) are nearly perfectly balanced in any number of cylinder configurations. Smoothness is a function of engine harmonics (vibrations created by rotating mass) and power impulses of the engine firing. Thus, a perfectly balanced boxer 2 will be less smooth than a boxer 4, a 6 smoother than a 4, etc.

Here is a good link for you.

http://www.e31.net/engines_e.html

and

http://autozine.kyul.net/technical_school/engine/smooth1.htm

Hope this is helpful.

 

[Motorbike]

quote:

---

Originally posted by Justin:

Would you know how the new 2.8 and 3.5 liter GM engines compare to this engine in regards to longevity/durability?

---

No I never even lifted the hood with either of those under it that I know of .

What vehicles are they used in < curious >

 

[1 FMF]

gotta love the epa/cafe for that one.

but if you lean it out, and buildup more heat in the cylinder (whether towing or not), don't you automatically increase NOx emmissions?

I too have heard that the v-12 was a naturally balanced engine... I believe it was a discovery show on the mclaren F-1, where they used a bmw v-12 naturally aspirated motor.

On the inline 4-cyl 3.0L mercruiser in my boat, the coupling between the sterndrive yoke and the crankshaft taked a pounding because of only 4 pulses per 2 revolutions of the crank, or so I've been told. And can make for hard removable of the outdrive if that coupling isn't kept greased to prevent galling and seizing. I would imagine all 4-cyl 4-stroke engines are like that. Worse harmonics maybe?

The ignition on my '02 camaro, and all LS1 GM's I think, have individual coils per cylinder located on the rocker covers. The spark plug wires are a straight run to the plug, about 6-8". On the gf's '03 jeep, that's an inline-6 4.0L and looks to have a coil on plug design. I haven't pulled it off yet to change the plugs, which is recommended at 30k miles.

I would think all motors now are distributorless. Electronics and computers make it so easy, and probably cheaper, to control the ignition. All you need is a crankshaft position sensor.

As for longer lasting, I think it would be based more on overall design, cooling and oiling systems mostly, rather than an inline vs V cylinder design.

 

[Matt_S]

For inherent secondary balance, you need six cylinders in a line, meaning inline 6's and V12's would be the best. I understand the reason is that, with this configuration, every piston has a corresponding piston 180 degrees away on the crankshaft. (Someone please correct me if I'm wrong). I've also read that V8's can be made to come very close to achieving this, while V6's and inline 4's would need balancing shafts.

As for the new GM 4 and 5 cylinders, I don't think anyone knows the reliability since they're so new. The GMC Canyon and Chevy Colorado are the first ones to use these engines, which are basically the inline 6 with 1 or 2 cylinders shaved off.

 

[Justin]

Sure...both the 2.8 I-4 and 3.5 I-5 are in the Chevy Colorado and GMC Canyon.

Although I don't tow anything extremely heavy (nothing the Toyota could not handle), I do tow and haul things around quite often (this will be a "farm" truck) and found this interesting:

"In order to keep emissions minimized under heavy load (towing), they had to lean out the fuel mapping. Engines keep cooler under heavy load by increasing the amount of fuel flowing into the cylinders, so leaning out the fuel mixture results in higher engine cylinder head and block temperatures. So, GM engineers reduced the maximum load/tow rating of the Colorado based entirely on fuel delivery and subsequent engine cooling, not on the actual strength or reliability of the powertrain."

[ August 20, 2004, 12:29 PM: Message edited by: Justin ]

 

[Ugly3]

Interesting write up.

Smooth 3

 

[crashz]

Good technical article on the balance of engines. Not very in depth, but it illustrates basic concepts though.

 

[Chris B.]

I bought a 3.5 Colorado last month and I test drove just about everyother make and I'll say the I5 is the smoothest engine I have seen. Power is good as well. The only time is shutters is when you turn it off it will buck a little like every V6 I have owned and V8.

 

[Propflux01]

It was my understanding on the inline sixes that since the engine is longer, the water in the block keeps the cylinders warmer, thus prolonging the life of them. Don't know if it is true, but what I was 'taught' in my earlier days of tinkering.