6 cylinders versus 4 (longevity)

General Discussion
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61

Just to throw a little more into the mix…is it worth the small increase in reliability (none IMO if 4 is run within it’s design parameters) if the 4 cyl handles substantially better. This seems to be a fairly common trait among many front drive cars, along with the added and annoying torque steer in some poorly engineered models. Check out CU comments on v6 vs 4 cyl. on some popular makes.

The added wear on brakes and other front end components, and the 4 cyl could result in a more reliable auto overall. This in a car that was originally designed as a 4 cyl.

Many remember the the v8 Pontiac Firebirds, but I remember the ohc straight 6 in the originals that I felt made them a better all round car, just to make a similar point. Obviously the tire squealers won out over the road huggers. We had a six in the family…a well balanced and very reliable car.

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Dagosa, Pontiac Said “We Build Excitement!”

They do build it! I have logged many hours in V-8 Trans-Ams. Believe me when I tell you that Pontiac was not referring to a straight-6. I didn’t even know they made a few. Did it have three-on-the-tree shifting ?

By the way that’s quite a stretch to make a V-6 look like it has less longevity than a little 4-banger on steroids.

I noticed you kind of drifted from the original question of longevity into some enlightening anecdotes pertaining to “handling”.

63

Just to repeat myself on previous post, so you know where I stand on 4 v 6 longevity. It’s all about design parameters and staying within them;

“A more powerful engine usually has a greater stipulated performance envelope. If the weaker engine stays within it’s, and the more powerful one the same…longevity should be equivalent. Try to ask a weaker motor to perform in the realm of a motor with greater torque esp., you’re asking for shorter working life…this applies to the other components as well. This also assumes they are both from the same manufacturer with the same design philosophy.”

The rest of the comment had to do with the overall reliability of the car. That’s as an important consideration for me when transmission repairs,cumulative brake repairs and body part replacement etc. any of which could easily exceed cost of engine replacement.

But, you may decide to take this comment out of context like you did the last…and make up something else I didn’t say.

See comments on Pontiac 6 @ http://www.classicaldrives.com/50226711/pontiac_ohc_straightsix_finally_gets_some_respect.php

64

a turbo decreases specific fuel consumption. specific fuel consumption is measured as mass of fuel consumed per hour divided by power output. Ends up as grams per KwHr. This boils down to saying that a 150 HP turboed engine will consume less fuel than a 150 HP naturally asperated engine

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as a mechanical engineer i feel confident in telling you that a fair amount, though not all, of what has been posted in reply to your question is speculation and BS.here’s how you figure out which engine to get. go to the dealership and take both options for a test drive. if you find in your test drive that you have to run the 4 cyl. up to redline in order to accelerate the way you normally drive -then get the 6. if you find that the 4 cyl. has enough power/torque to keep up with you (it should shift before/around 3500 rpm while driving normally)-get it.
all the talk about the four having to work closer to its performance envelope is semi-correct. in terms of the engine components a properly designed engine will be built for infinite life. to explain -each part has a certain maximum force applied to it. these forces are felt as a stress (force per area) in the part. generally more force equals more stress equals fewer applications of that force before the part fails due to metal fatigue. however there is a threshold in stress below which the metal no longer experiences fatigue and can theoretically survive infinite applications of that stress. furthermore there is a factor of safety that is taken into account i.e. Factor of Safety of 2 means that the part is designed to have infinite life at double the expected maximum load. there are many many other calculations that take into account stress concentrations, mounting considerations, etc. ad nauseum. what does this mean. you can’t simply say that a 200hp engine will not last as long while producing 150hp as a 250hp engine producing 150hp. the general idea has some merit but it all comes down to design, design, design.
that said audi’s 2.0L turbo has won top position on Ward’s best 10 engines for several years running now.

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Thank you…not being a mechanical engineer but some experience in owning and operating heavy equipment, it seemed pretty straight forward when choosing which a tractor to use for which task. What was the work load and rpm required at the PTO to do the task. If load required was near limit of one tractor…get bigger one. The smaller one lasts just as long at it’s reduced work load. Why wouldn’t that apply to any ICE ?
Provided we are not comparing a Chevy Vega 4 to Cummings 6 cyl diesel, it seems pretty straight forward. Stay within the design parameters of the manufacturer for longevity and make your decision of power required (not just 4 v 6 ) from there.
We’er up to 65 posts because some of us don’t have a life.

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I remember the 2 cylinder John Deere tractors from 50-60 years ago. It seems to me that these 2 cylinder tractors ran as long as the 4 cylinder International Harvestors or the Minneapolis-Moline tractors. I hope this post doesn’t start a long feud about tractors with the old farm boys out there.

At any rate, in those days we didn’t give much attention to the number of cylinders an engine had. Most of the trucks back then were 6 cylinder–the Ford V-8 being the exception. I don’t remember the life expectancy of one truck being any greater or less than the Ford V-8 trucks.

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By the way, dagosa also supported my arguement when he said:

A more powerful engine usually has a greater stipulated performance envelope. If the weaker engine stays within it’s, and the more powerful one the same…longevity should be equivalent. “lets not cherry pick”

Let’s not cherry pick supporting statements from other people’s posts to make our points. If we can’t make our own points in this debate, the least we can do is not drag others in and claim they support our positions

69

“At any rate, in those days we didn’t give much attention to the number of cylinders an engine had. Most of the trucks back then were 6 cylinder–the Ford V-8 being the exception” It’s not exactly the number of cylinders but the amount of power. It just happens that most 6s have more power than most 4s. Less power generaly contributes to more wear and shorter life. As for the John Deere 2 cylinder tractor, the engine probably had as much or more CID than the 4s. Size Matters! Most 4s run up to 2.5 liters while most 6s run up to 4 liters or the old 4.3 GM V6.

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it wouldn’t apply to an ICE proper because of infinite life design. however there are parts on a car that cannot be designed for infinite life…tires brakes belts etc. and i would suspect that most problems credited to engines are not really engine problems but accessory problems …alternators, starters etc. some of these would be more likely to fail due to more cycles experienced because of higher rpm. i would also be willing to bet that the majority of engine failure could be prevented by proper maintaince. in order to try to be as political as possible and cover my a$$-there are definitely reasons not to run engines at high rpm however higher rpm is not always synonamous with peak power.
with regard to heavy equipment you probably know more than i do. but i would suspect that problems with underpowered equipment deal more with the linkage/drivetrain between load and engine than the engine itself. and a more powerful engine demands a stronger linkage in order to move a larger load. in the automotive industry it is common for the automaker to use the same transmission behind several engines because the load (the car) doesn’t really change that much.
i do agree with your train of thought. however in dealing with a vehicle I don’t believe a automaker could sell a car that would be so underpowered that normal driving habits would require the engine to be wrung out enough to damage it. adn would base my engine decision on design and how fast i wanted to go.

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“with regard to heavy equipment you probably know more than i do. but i would suspect that problems with underpowered equipment deal more with the linkage/drivetrain between load and engine than the engine itself. and a more powerful engine demands a stronger linkage in order to move a larger load. in the automotive industry it is common for the automaker to use the same transmission behind several engines because the load (the car) doesn’t really change that much.”

TRANSMISSION in heavy equipment are subject to similar considerations as stated for motors. make sure they work “well” under load capacities for them as well…why tempt faith when a tranny rebuild is often more than an engine and the price of a new condo. Friends dozer cost 75% of it’s value to rebuild it’s transmission. Transmission failures are due more to load stress and poor operator procedures as well as time while engines are cumulative wear/high operating rpm over time. If you’re kind to your transmission, you’ll be kind to your motor as well.
You’re right in that nothing irritates a contractor more than an inconsiderate operator…the transmission suffers most.
But we should be talking more about the motors I guess;

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And unlike cars, you won’t find tractor manufacturers often “stuffing” bigger motors into existing models. Overall integrity is too important. You want a bigger motor…you get different model tractor with all the appropriate design changes.
That’s why, for longevity, I would buy a car (not truck) with the standard engine and change models that come standard with the larger motor (and hopefully design changes) if more was required.

73

This posting started out with a guy wondering if he should buy a 4 or a 6 (in the same car) for longevity’s sake. It went everywhere from there. Several people have agreed that a 4 trying to do the job of a 6 in the same car, you could expect shorter life. Now if they have to add a few pounds to the car with a heavier tranny, larger brakes, bigger tires, and radiator, The 6 would more than make up the difference and you would have a better car. I wonder why they quit putting the 4 banger in the Ford Taurus? Or why not put a 4 or a 6 in the Crown Victoria?

why not put a 4 in the Impala?

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The straight 6 you refer to is probably about 300 CID (5 liter) while the V6 is from 3 liter to 4 liter The 5 liter just might be tougher than the smaller ones.

75

Good post; in Europe and other places with expensive gas, cars that size are all available with 4 cylinder engines. The Jeep Grand Cherokee assempled in Austria by Magna International comes with a 4 cylinder diesel and 5 speed manual. Large engines are only popular with rich Germans because of the high (or no) speed limits.

The power required to propel a car in the US is very small compared to what it akes to propel the Audi in Germany at 110 mph. Gemans have a choice depending on how fast they want to drive. In the US a car spends a great deal of time just warming up, and a small engine warms up quicker. Over 80% of engine wear is caused by cold starts.

All said, I would prefer a non turbo 6 over a turbo 4, but that’s because of the turbo, not the cylinder count.

76

In the US a car spends a great deal of time just warming up, and a small engine warms up quicker. Bologna! Have you guys on here ever driven a 200 hp car?

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My car is 19 years old. Very rare, and not many imported. It is very costly in terms of maintenance because everything is so close together. It is a life insurance policy on snow or slippery roads. Toyota Celica All Trac. Turbo. 4 cylinder.

Original engine. 2.2 liter. Yahamaha engine, not a Toyota engine. It is as powerful without the turbo as most 6 cylinders sold today. It is a heavy car, weighing almost 3900lbs. Manual transmission which I imagine many have a view of.

I have not been able to let this car go because I have driven other cars thinking what if? The new Lexus is250awd doesn’t drive as well as this car.

I think if you buy a decent, well maintained used 4 cylinder Toyota or Honda and keep it up, you won’t have an issue.

I think the new Nissan is a good vehicle and if you maintain it you won’t have a problem.

Lots of press on the newer light GM cars, as well as the Honda Fit, Toyota Yaris, etc. Those are throw away cars.

I think the mid sized 6 cylinder cars from Ford and GM are as good as the 4 cylinder Honda and Toyotas. It is all about what size of car you need, and all about you maintaining the car.

The mechanic who worked on my Toyota for the longest time, and he worked at a Toyota dealer, had a bland Chevy minivan that he got close to 250K miles out of because he changed the oil and did the maintenance.

I believe it is not which brand you by, what size engine you buy, but how you treat it and how you take care of it that matters.

I bought my main driver used over eight years ago, with almost 67K miles on it. I drive it all the time, it goes in snow and ice. Has it cost me to keep it up, yes. It is a sports car with all wheel drive. I drive it like a little old lady in snow because I know what it can do. I don’t want it smashed up. But it is reliable, safe, and it looks good.

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there are many factors at play. Do you want the power (obviously Audi’s have quite a bit of that) or have very peppy acceleration w/ the 2.0 litre turbo? there is also fuel economy, repairs, and wanting to spend the extra money upfront for the 6 cyl. The choice is yours but if it were me, i’d go with the turbo 4.
Good luck :slight_smile: P.S: Audi’s have pretty strong reliability records, so longevity concerns between the two engines shouldn’t be to aggressive.

79

I could have easily lost respect for you when I discovered you were not a man of your word, but I thought I would give you the benefit of the doubt.

I guess you either don’t have any factual evidence to back-up your claims or you stubbornly refuse to share them. Yet you claim you are here to cure our ignorance. I guess if you go back on your word once, there is no reason to take anything else you say seriously.

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I love it! Confronted with a fact, your only response is “Bologna!” Elly, you are priceless!