why 3.0L 4cyl when you don't see that in automobiles?

[aggiedave98]

Hopefully this is ok to post here...<br /><br />Why do you see a 3.0L 4 cylinder boat engine, but never a 3.0L 4 cylinder car engine? Most 3.0L car engines are 6 cylinders. Is there a reason why you see this in boats, but not cars?<br /><br />Just trying to educate myself...<br /><br />thanks.

 

[aggiedave98]

Re: why 3.0L 4cyl when you don't see that in automobiles?

ok, just saw the post:<br /><br />Inquirering mind...<br /><br />I swear I didn't see that post before I posted this. (I opened it up, but didn't read it yet.)

 

[trog100]

Re: why 3.0L 4cyl when you don't see that in automobiles?

the more cylinders an engine has the less vibration it causes.. there is no other reason for multi cylinder engines.. u could have a single cylinder 3.0l engine if u wanted.. it wouldnt run very smoothly thow.. with boats the engine vibrations obviously aint as high on the priority list as they are in a car..<br /><br />trog

 

[aggiedave98]

Re: why 3.0L 4cyl when you don't see that in automobiles?

Trog,<br /><br />Is that really true though that's the only reason? Wouldn't another reason be that to get high HP (for the same displacement) you need to have smaller cylinders that can go to high RPM's (I'm assuming large heavy pistons have a lower max rpm).

 

[trog100]

Re: why 3.0L 4cyl when you don't see that in automobiles?

its still all about vibration.. the higher the rpm the greater the vibration problem.. so if u want to run an engine at higher revs u do need the multi cylinders..<br /><br />but talking about the average 4 or 6 cylinder engine its just that the six will run smoother than the four.. both could produce enough power one just does it more smoothly..<br /><br />the other factor is the length of the stroke.. how far the piston has to go up and down.. todays engines have shorter strokes than the engines of yesterday.. this does go against your theory that smaller pistons are better thow.. cos the shorter the stroke the bigger the piston has to be for a given displacemnt..<br /><br />basically a piston has to accelerate from a standstill to a maximum speed at mid-stroke then decelerate to a standstill each stroke.. the shorter the stroke the shorter the distance the piston has to travel and the less stress loads are placed on everything.. this is the main thing that gets todays engine up to higher revs.. shorter strokes.. not more cylinders or smaller pistons..<br /><br />the other factor is moving from overhead valve systems to overhead cam systems.. with an overhead cam all the valve spring has to do is close the valve.. with the other method the poor old valve spring has to close a rocker plus long push-rod and hefty cam follower.. this used to limit the max revs overhead valve systems could reach.. the term for it was valve bounce or valve chatter.. basically at a certain rpm the valves just simply didnt close properly and the revs had to be backed off..<br /><br />trog<br /><br />ps.. one other factors is points.. they dont work that well at high rmp rates either.. electronic ignition plays its part in the pursuit of more power from a given size engine..

 

[rodbolt]

Re: why 3.0L 4cyl when you don't see that in automobiles?

the biggest reason is its about the only entry level 4 banger GM made, ford dropped the 2.3 years ago. the 3.0GM is also used in a lot of industrial and stationary stuff. but soon it will dissapear. the 3.0 started life as a 2.5,153 CID that shared quite a few parts with the old 230/250 inline 6. the other problem is the emissions and long engine height of an inline on most modern cars small enough to run a 4 banger.

 

[Boatist]

Re: why 3.0L 4cyl when you don't see that in automobiles?

I belive the 3.0L 181CI was used in the Chev II auto.<br />In it day the only other option was a straight 6 cyl. The 6 took up a lot more room and was much heavier without much more power.

 

[seahorse5]

Re: why 3.0L 4cyl when you don't see that in automobiles?

The 3.0L motor is an industrial engine that was not used in automobiles. It powers air compressors, fork lifts, pumps, etc. and has been around for a long time. It is said that the older Post office small delivery vehicle used the same engine.<br /><br />The 153ci motor was used in the Nova II and in the early 120hp stern drives. That engine had a very short production life span.

 

[Weirdwalt]

Re: why 3.0L 4cyl when you don't see that in automobiles?

I think cost factors are the reason they use that. It is an industrial engine and it's a tough beast. If the auto version of the 3.0 six cylinder were less expensive I imagine they would use it if it would last.

 

[Paul Moir]

Re: why 3.0L 4cyl when you don't see that in automobiles?

I'm no expert on this stuff, but I think the answer is simple. 4 cylinder engines are less expensive than 6 cylinder engines, because they have (close to) 1/3 fewer precision parts as a 6 cylinder. <br /><br />3.0L is pushing the outer limits of practical bore & stroke for a gasoline engine at 4.00" x 3.60". So it's simply the largest, cheapest engine.

 

[aggiedave98]

Re: why 3.0L 4cyl when you don't see that in automobiles?

Trog,<br /><br />Thanks for the explanation. I'm not disagreeing with it, but why does it make more vibration?<br /><br />If you had an inline 4 versus an inline 8 (if they made them) and the 4 was 3.0L and the 8 was 6.0L, all pistons are the same, bore and stroke are the same, etc. Would there be more vibration? Or are you saying that bigger pistons have more vibration than smaller ones?<br /><br /><br />Thanks for all the replies. I'm really interested in knowing more about engine tradeoffs.

 

[Weirdwalt]

Re: why 3.0L 4cyl when you don't see that in automobiles?

Its the firing order that causes the vibration. In a V engine there is usually a piston firing opposite to cancel out vibration. On inline engines there is no opposite effect since all of the pistons work in the same direction. The addition of a balance shaft in the engine will help a lot. Some V engines require balance shafts, I think those were the old 90 degree ones. Most 4 cylinder engines arent too bad though. Some of the old I-6 truck engines vibrated pretty good.

 

[Dunaruna]

Re: why 3.0L 4cyl when you don't see that in automobiles?

Welcome back, Walt.

 

[trog100]

Re: why 3.0L 4cyl when you don't see that in automobiles?

in the US its a bit different than the rest of the world.. cheap gas again i spose..<br /><br />in the rest of the world four bangers are the norm.. not some special cheapo entry level option..<br /><br />"he biggest reason is its about the only entry level 4 banger GM made"<br /><br />rodbolts comment is interesting.. in the US praps.. but in the rest of the world no..<br /><br />GM under the guise of vauxhall (UK) opel (germany) made many four bangers.. in fact most of the production were and are four bangers..<br /><br />a 3 litre four banger is okay for boats or the more common industrial uses.. or even a post office delivery truck.. for a car it dosnt hack it.. it just dont run smooth enough.. <br /><br />the way the rest of the world does it is roughly this.. up to two litres are mostly four bangers.. even small/medium high-end cars still use four bangers.. anything over two litres is usually a six cylinder and also mostly in the luxury or high end market.. this market demands the smooth running of six cylinder engines even at less than 2.5 litres..<br /><br />in the rest of the world.. a 2.5 or 3 litre four banger is pretty much unheard of.. mind u so are seven litre V eights.. he he..<br /><br />as Weirdwalt says it is all about firing orders and smoothing out individual power strokes.. and yep the more cylinders the more expensive to make and the more bits to wear out.. but the more cylnder (in thoery at least) the smoother the engine will run..<br /><br />i think the american gm four banger we use in our boats was really a (more normal for america) inline six.. they wanted an economical entry level engine for some cheapo car (or post office trucks) and just lopped two cylinders of the inline six..<br /><br />the big difference here is the 2.5 litre four banger that was the result (entry level) would not have existed in the rest of the world.. 2.5 litre aint entry level..<br /><br />our two in one engines are normally a 3 litre inline six for the luxury car chopped to a 2 litre four banger for the not quite so luxury car..<br /><br />in the rest of the world anything bigger than a 3 litre six cylinder engine would be exotic and have more than six cylinder.. we have 3.4 litre V eights for example and jaguar (when it was jaguar and not ford) used to have a 12 cylinder at about four litres..<br /><br />in the rest of the world a 1.6 litre petrol engine is considered average to medium size..<br /><br />trog

 

[Dunaruna]

Re: why 3.0L 4cyl when you don't see that in automobiles?

Maybe in Europe, trog. But not downunder. In boats, V8s' rule. Obviously the 350 dominates the list, but 302/351 are (still) also very common here.<br /><br />The 3.0L is offered in entry level packages but not many people fall for that old trick. We want cubes .

 

[TilliamWe]

Re: why 3.0L 4cyl when you don't see that in automobiles?

walt you tired of p_____ people off at TBM? <br /><br />I was once told that an I-5 would be smoother than an I-4 or I-6 or even I-8. Any truth to that?

 

[trog100]

Re: why 3.0L 4cyl when you don't see that in automobiles?

i was just talking engines in general Dunaruna..<br /><br />in boats i recon V8s rule everywhere.. its just that not many off us can aford to put the gas in em.. he he<br /><br />in the UK and probably the rest of europe at the moment with larger engines of any kind diesel is the only "sensible" way to go.. especially in boats in the UK cos we dont pay the huge tax on it for off-road use.. basically diesel cost us about 1/3 the price of gas.. at that price difference with anything that guzzles fuel there aint no competition..<br /><br />where off-road diesel is concerned its us dudes in the UK that get the good deal.. pretty unusual that in rip-off britain.. he he..<br /><br />most UK boaters go green at the gills when i mention the fuel costs for my little american style gas powered boat..<br /><br />trog

 

[rodbolt]

Re: why 3.0L 4cyl when you don't see that in automobiles?

trog<br /> ya got it all wrongies over there<br /> the 153 was later the 181 in the early 80's the 153 was in production for about 20 years in the states. but in the states that long stroked overhead valve pushrod motor was not popular in an auto. at that time most our autos started at 2700 pounds and rapidly grew to over 4500 pounds.<br /> the inline 8 will be much smoother than the 4 due to the power impules at shorter intravels. has not much to do with 60*,90* V or inline or slant six. all could be very smooth. the carbed 181 with the mercarb is a bit shaky, the 153 with 2 1bbl carters was smooth as any v6 or v8 I ever ran.<br /> v8s in the 7-8.3 L class were common here for many years. the 6.6 and 7.4's were everywhere. I ran one for many years in a 3300 pound auto. <br /> when I bought it shell super leaded at 98 octane was about 40 cents a gallon and it only held 19 gallons.<br /> I find it very interesting to see what the overseas market did with smaller cubes and higher operating rpms. the only thing,well one of the things, I hated on that v12 jag was lash adjustments, that and like any other vehicle with lucas electrics it tended to die or catch fire more often than ac/delco stuff seemed to <br /> my dad was big into british race cars, I drove an old elva about some years ago after he was done. most kids could not believe I could shift that coventry at 11,000 RPM on my way to school <br /> best I remember the redline on it was about 14,000.<br /> I am also friends with the guy who's grandfather developed the coventry. he owns a marina near me now but still gets royalties from the coventry design.

 

[aggiedave98]

Re: why 3.0L 4cyl when you don't see that in automobiles?

Rodbolt,<br /><br />Dumb question (maybe?) but what is the conventry?? (google wasn't enough for me to find out easily...)

 

[Lou C]

Re: why 3.0L 4cyl when you don't see that in automobiles?

I recall reading that the engine configuration is is one thing that does affect smoothness. <br />An inline 6, and a V-12 are supposedly in perfect balance. V-6s, esp 90 degree ones are rough, to the point where GM put in the balance shaft to smooth it out. My old non balance shaft 4.3 V-6 is not too bad, just a period of resonance about 1800 rpm, it idles smoothly esp for its age and higher rpm running is pretty smooth as well. 60 degree V-6s are smoother. 4 cylinders start to get boomy and noisey over 2-2.5 liters, years back Mitsu added a balance shaft that smoothed out their 2.5 L 4 well (ChryCo used in their vans for years, and Porshe also used it in the 944)<br />I'd like to see more inline 6's in boats, they are a lot easier to work on and are smooth, and have good low end torque. I'm thinking the old AMC/ChryCo 4.0 six in my old Jeep would make a good boat motor, 225 ft lbs of torque down low, it is just a long engine though. I would give up a little room in the boat to be able to get at everything without breakin me fingers, wouldn't you rod?