View Full Version : why I6 diesels are better than V8's
Blowing head gaskets & blocks cracking along with the know lift pump & subsequent injection pump failures, along with manifold bolts falling out. Now I know why the cummins boys tout the 5.9 with its inline design, it needs to be easier to wrench on with these kinds of problems.
http://www.dieseltruckresource.com/yabbse/index.php?board=4
[ 02-08-2003: Message edited by: Micheal Tomac ]</p>
An I6 is easier to maintain in some aspects, but try lifting one of those long, heavy heads out of the engine compartment, or trying to set the head back on the block without it sliding on the gasket THEN tell me they're easier to work on. Same goes for lifting that heavy I6 injector pump up from the bowels of the engine compartment versus having to take the intake manifold off to get the pump out. I don't mind minor or routine maintenance being a little harder, like it generally is on a V8, if it means the major jobs are a little easier at times.
turbokid
02-08-2003, 15:03
I would rather have an I6 over a V8 any day. Just put a head on my dad's 7.3 that we had rebuilt, and ruined a head gasket trying to squeeze it down between the intake, blower motor, miscellaneous hoses and wires, and firewall. It's much easier to hook a cherry picker to an I6 an pull 'er right out...and set it back in...
As far as the injection pump, I had to replace my front oil seal on my pump when I first got the engine in, (had been sitting for a while) it took maybe an hour to get the pump out and was no big deal lifting it out... even if it was, I would much rather have the performance, reliability, and better built-ness of an inline pump over a rotary any day. (Though the bosch rotary aren't too bad.)
I like my deep skirted, real lift pumped, heavy injection pumped, heavy headed, and easier maintained I6, thank you.
[ 02-08-2003: Message edited by: turbokid ]</p>
GOTTA CHIME IN HERE. INLINE ENGINES ARE EASIER TO COOL AND KEEP COOL. LESS HEAT MEANS LESS WEAR AND TEAR AND TROUBLE. PERIOD, END OF STORY.
BEYOND THAT, ITS AN ARGUMENT THAT CAN GO ON FOREVER! HA HA
i am a happy dmax owner and am satisfied withthe power,but i tell you if these maxes had a 5.9cummins they would never get a tranny fix.just my opinion.jess
having to "work" with and around Diesels all my life, I have an opinion. I think that if GM had the Cummins.......there would be no other truck on the road tongue.gif
Burner
I'm sorry but there is no way I would subject my neighborhood to a Cummins cold warmup every winter morning. It would have been a definate no-sale for me.
Now the new motor is real quiet so that's a different story.
Rebel_Horseman
02-12-2003, 08:10
I'd have to agree with Burner. The Cummins I-6 is probably the best bang for the buck. The Cummins is such a good towing motor that I almost wish I would have bought one. Don't get me wrong, I love my Dmax, but a Cummins will out tow me any day (stock vs. stock). It's the efficient design that gives it gobs of bottom end trailer pulling power. Our trucks are made to wind up a bit before they grow some cajones. That same design also allows excellent fuel mileage. The downside to the motor is the trucks they are in. Let's face it, Dodge trucks aren't nearly as nice or confortable as our truck. Couple that with a pi$$ poor automatic trannie and you can rule Dodge out. The HO ISB and the NV5600 hand shaker are a nice combo though.
Reb [><]
I have no doubt the Cummins is a terrific engine, but I've wondered about this. Are there any engineers out there who could explain. Is there something in the I6 configuration that is inherently superior to the V8 from a theoretical power producing perspective? Or is there something in the particular execution of the Cummins that makes it such a good powerplant? Just wondering.
TC
I'm also curious.
Virtually all big truck/tractor engines are I6 (12.7L Detroit, 14L Cummins 3406 Cat etc.) Two bigger diesels I can think of that were V-8 config were duds (John Deere had a V-8 for a short time in the 80's, and I think Cummins had a 904 cu-in V-8 for a while) The old 2 stroke Detroit 8v series were v-8 and were not the greatest either.
84 Convert
02-12-2003, 23:43
Just my 0.02 here, I understand that the inline design is inherently the best-balanced engine design out there. Another factor is the super long stroke of the Cummins. If I recall correctly, it is about 5.1", whereas a V-8 is usually around 4". I'm no expert, but those would be my guesses as to why the I-6's get the nod for heavy towing (except locomotives and tug boats) :)
Gregg
[ 02-12-2003: Message edited by: 84 Convert ]</p>
a5150nut
02-13-2003, 19:28
Even Cat equipment ran better with I6 motors. I used to run 633c scrapers when the new "D" models came out with the v8 in them. Side by side the c with the inline 6 would run off and hide from the d model V8s. The inline has more bottom ent pulling power. The V8s, runu like a Detroit! Wind em up and keep em wound up.
Now the 637s with 425 horse V8 in the front and a 3406 I6 (375hp) in the back - that is 4 wheel drive! And if you cant climp it, you can re-shape it till you can......
imported_
02-14-2003, 10:16
inline sixes have perfect primary and secondary balance (dividing the rpm range by 3) only in the 3rd order do they start to shake a bit.
triggerman
02-15-2003, 01:24
The crank jurnals in the v-8 have to deal with a cris/cross blow of harmonic vibration ,which is the best way to stress a bottom end compared to the straight down harmonics of the I6. This harmonic "shock wave" is created when the piston stops momentarily at the bottom of the jug. When the cap bolts are inline with a straight down harmonic blow from a inline, bottom end stress is minimised. Unfortunatly ,the cap bolts on the 6.5 do not point in the direction from which the "shock wave" is coming.... cracking bolt holes is the result. Constant hi revs in these v8's leads to premature death,(compared to a inline). My .02....
If properly designed like most diesel v8's crank and block cracking is not a problem or issue at all.
turbokid
02-16-2003, 16:57
HAHAHA
I have yet to have seen a diesel V8 designed properly...
There may be a few that are designed "properly", but they still won't hold up as long or under as much stress as a "properly" designed I6...
Practically every major diesel engine manufacturer has tried a v8, none of them have been succesful... 903 cummins- 2 mpg, wouldn't hold up over 300 hp... 555 cummins-also a flop... International and cat have also tried them, they haven't worked... You may cuss detroits, but the 8v-71 was about the only one that held up at all, if you kept oil in it... :D
Hop on the interstate and I highly highly doubt you would see one v-8 powered semi even if you drove all the way across the country... International tried a v8 in a farm tractor, didn't work...
There are countless examples of failed attempts at v-8's and applications of them...
THEY JUST DONT WORK
Bradley Fighting Vehicles use a 650HP 903, and Multiple Launch Rocket System tracks use a 500HP 903. The problems with these vehicles don't lie in the engines, but rather the stress cracks that develop in the alloy hull and allow the engine to move while the transmission is held rigidly in place. I still say the reason inlines have a near monopoly in OTR and off-road use is because 1) everything's much easier to reach during routine maintenance, and 2) most OTR trucks and off-road machines have plenty of room length-wise but not a lot at all width-wise.
The only inherent advantage I can see that an inline engine might have is a lower piston speed due to the lower RPM required by the longer stroke. Piston speed and side loading are basically what determines cylinder wear, which is why a stroked V8 wears cylinders out so quickly.
I still say that if the 6.2L had an extra 100lbs or so of iron in the block & heads, it'd be a 500K mile engine. I know, I know - IF IF IF! smile.gif
[ 02-16-2003: Message edited by: NH2112 ]</p>
Depends on how much HP you want, over 600 looks like V-8's. Think a 6 would get quite long. Cat 3508 engines have a good rep.. Hundreds of them running 24-7 as prime power generators and for marine use.
turbokid
02-17-2003, 11:47
Maybe the 903 would hold up under higher horsepower in a slower application like that, but they didn't hold up in semi's...
3508 cat- that's a different story running as generators and marine use... more of a constant load and rpm...
I will have to admit that the biggest haul truck cat makes, the 797B, doesn't use a straight six, but the 3524B, a V24 that, in this 380 ton nominal carrying capacity truck puts out 3550 gross horsepower. It has a displacement of 117 liters, or 7143 CI...
The smallest one they make, the 773E, with only 710 gross horsepower, uses the 3412E, which is, you guessed it, a straight 12. That's right 12 cylinders in a row. It is 27 liters. And it's not an issue of width, either, as it's about 10 ft wide.
But no v8's... tongue.gif
All of CAT large gensets are V-design be it V8,V12,V16. Most locomotive and marine engines that are not Fairbanks Morse, are V-design ie EMD and ALCO. Inline or V is all a matter of application.
turbokid
02-17-2003, 13:50
I was actually suprised that the 3412E is an inline 12, but that's what it says right on their website...
As far as inline or v depending on application- that is very true when you get into the larger applications...
triggerman
02-19-2003, 00:13
At the prison where I work, We run a Cat V12 generator when the grid goes down.The thing overheated once and now blows blue smoke slightly.
The Cat service guy says there's nothing wrong with it. I think time will tell... :rolleyes: Ya think they woulda had a Hi temp shut down that works on a beast like this!!
They are easier to work with, and there is not as much moving parts in them.
Rebel_Horseman
02-19-2003, 11:38
Here's a thought too. GM's Elector MOtive Division (EMD) makes locomotives. These jokers put out 6,300 hp in some applications and they are used in mainline freight trains. Check out this link:
http://www.gmemd.com/en/locomotive/innovations/engine/Hengine/index.htm
This is a I-16 design. I think it comes down to efficiency. An inline motor can make more use of the combustion process and make more power. That's just my opinion.
Reb [><]
NickLeinonen
02-19-2003, 18:42
that big ol' emd diesel is a V-16, not an I-16. it is a narrow V though. 45
Well of course an I6 has fewer moving parts than a V8 - it has 2 fewer rods, 2 fewer pistons, 4 fewer valves, springs & lifters... :D
Want to see a really neat design? Check out the Fairbanks Morse web site. 10 cyl. vertically opposed engine, 20 cyl. Was developed for the submarine service in WW 2. Very compact power. They call them Centennial engines cause they will run 100 yrs, maybe.
Cummins 5.9 4.72" stroke
Duramax 6.6 3.96" stroke
Gotta love the way a I6 Diesel sounds. I've got 315/70/17's on my new quad cab Dodge and it gets about 2 to 3 mpg better than my single cab Duramax did with 285/75/16's on it. Long stroke Diesels rule, torque in the low rpms is unreal.
bigredhummer
03-03-2003, 19:42
7 mains vs 5, can you say longevity? How many v-8 diesels do you see with a million miles..... zero!!! The inlines like the cummins5.9 and big rig motors can and will go over a million miles if maintained properly.
Our 903 only got 1,170,000 miles before it burned up. I guess that the wires are not designed to last that long, they caused the fire. We did not get the truck after the fire, the insurance got it.
Burner :D
We just took 3 Cat V250Bs in trade from a lumber yard, the one I looked at has 37,000 hours on the original 3208 and its only problem is a leaking rear main (our used equipment guys went over them with a fine-toothed comb because we have to get a lot for them at sale.) Using 40 miles/hour as a rule of thumb that engine has 1,480,000 miles on it, and a lot of them at idle.
The whole "7 main bearings versus 5 main bearings" argument doesn't mean much when you're comparing a medium-truck I6 with a light-truck V8. A Ford 300 I6 or AMC 258 I6 have 7 main bearings, but they don't typically last any longer than 5 main bearing V8s do. Saying the reason a 5.9L Cummins lasts longer than a 6.2L GM is because it's an I6 instead of a V8, or that it has 7 mains instead of 5, is vastly oversimplifying things.
DieselEnvy
03-05-2003, 20:08
Of course a well designed inline six will have more main bearings than a V8.......the crank is longer! Now maybe compare the ratio "mains per inch of crankshaft"! ;)
------------------------------------------------
A Ford 300 I6 or AMC 258 I6 have 7 main bearings, but they don't typically last any longer than 5 main bearing V8s do
------------------------------------------------
I disagree with this statement. I have owned several 258 and 300 I6's, and I will share my experience.
The 258's in the Jeeps each lasted 100,000+ miles (sold), and the Ford 300 I6 is definitely one of the best engines they have ever produced. My last one was sold with 180,000 miles and still running like new (using no oil).
------------------------------------------------
Blowing head gaskets & blocks cracking along with the know lift pump & subsequent injection pump failures, along with manifold bolts falling out
------------------------------------------------
Ummm, I know of the lift pump issues in the '98.5-'02 trucks, and if you don't monitor that it can take out the VP44 (this is no longer a problem in the '03+)... Pretty much everyone will admit to these shortfalls, but where are the blown headgaskets , lost manifold bolts, and cracked blocks??? All I see is a link to the DTR 24 valve forum...
If you blow a headgasket in a Cummins, your are: A)pushing 50+ lbs of boost, or B)running injection timing of 20 degrees or more. In either scenario you should not expect your head gasket to last too long, be happy it lasted as long as it did.
Blown head gaskets are very uncommon in a near-stock 5.9L no matter what year, and cracked blocks are almost unheard of without SERIOUS fueling. Methinks someone is telling stories. In fact, these are not problems plaguing ANY of the big 3 diesels... Misinformation only leads to widespread ignorance.
[ 03-06-2003: Message edited by: WKener ]</p>
"I disagree with this statement. I have owned several 258 and 300 I6's, and I will share my experience.
The 258's in the Jeeps each lasted 100,000+ miles (sold), and the Ford 300 I6 is definitely one of the best engines they have ever produced. My last one was sold with 180,000 miles and still running like new (using no oil)."
100K+ miles isn't a lot, though, and even 180K isn't out of the ordinary. I've never kept a gasser that long (usually destroyed them 4-wheelin' LONG before that), but could tell you about friends and acquaintances who do little to no routine maintenance on their V8 trucks and are still making it to the 150-200K range and beyond. I'm not saying the I6 gassers are bad engines - far from it! - just that on average they don't last any longer than V8s do.
My 258-powered Jeep had 140K on it and made smoke like a WW2 destroyer.
-----------------------------------------------
I've never kept a gasser that long (usually destroyed them 4-wheelin' LONG before that)
-----------------------------------------------
This is exactly my point. The gassers I am talking about were all used HARD (mainly offroad). Each vehicle was sold with said mileage, and all were running well. Who knows how long they went before the quit.
I have to concede that experiences differ, but for me the I6's held up longer to similar abuse.
We will just have to agree to disagree smile.gif
[ 03-06-2003: Message edited by: WKener ]</p>
BTW, I also have plenty of stories of abnormal longevity with terrible maintenance... It just goes to show, ya never know!
JMJORDAN
03-08-2003, 20:21
The answer to this debate has a lot to do with the application. I-6 diesels are in my opinion easier to service. V-8 diesels are preferred in light trucks because we only have a max of 6 speeds of transmission gears so we need RPMs. OTR trucks have 2 to 3 times more gears which makes them able to use a I-6s huge low end torque. Lower rpms means less wear. Your average OTR truck motor idles around 600RPM and redlines at 2000RPM. Dmaxs rev to 3200RPM and the new F@rd 6.0 revs to 3700. As far which is more durable common sense says the motor with less parts is less likely to fail. But there are always exceptions to this. My buddy's dad had 98dodge cummins it blew 2 head gaskets and cracked ahead. This truck was never modified. He drove 3miles to work everyday with no warm up. He would about 3 times a year tow 34 foot slide camper. It would always break down. He bought a new F@rd 6 months ago it has been in the shop 4 times already. He still does think the problem is him. Another buddy has a hotshot bussiness his 01 Dodge Cummins 5speed has over 280,000 miles on it. He starts it in the morning drives all day like he hates it. It takes like nothing!
Sorry for such a long post but I true beleive the answer has to do with the application.
losts of torque at low rpms
cracked blocks - The #53 Cummins block's have an extremely thin wall near the water jackets. They have been known to crack on trucks that have done heavy hauling to daily drivers.
manifold bolts falling out - improperly torqued bolts from the factory have loosened and fallen out. There is a TSB for this.
My cousin and his dad are big dodge nuts. Between the two of them they had the following problems with a Cummins. Lift pump, injection pump, scored cylinder, blown head gasket, manifold bolts loose & missing.
They've also had the famous nut backing off shaft that holds OD gear on the 5 speeds
http://www.dieseltruckresource.com/yabbse/index.php?board=4
do a search for head gasket, manifold bolts, cracked blocks or lift pump and you will get plenty of reading material
[ 04-15-2003: Message edited by: Micheal Tomac ]</p>
bigredhummer
05-01-2003, 19:09
There are several well documented cases on the TDR and in the TDR newsletter of million mile cummins diesels. Over the road semi trucks regularly go a million miles before overhaul. I have heard of no V-8 diesels going anywhere close to a million, 300 or 400K, but never a million.
The I-6 is a better design, 7 main bearings vs 5 on a V-8 diesel,not to mention the rods of an I-6 diesel each have thier own throw on the crank, they do not share like v-8 rods do. these are two reasons they can go a million miles, they have nearly double the bearing surface area of a v-8 diesel.
If you want a valid fallacy free discussion talking strictly about I-6 vs V-8 diesel design,you need to throw out all of your chevy, ford or dodge biases and quirks associated with each particular engine. (you could say V-8 diesels suck because ford's 7.3 powerstroke had injector cackle, idle knock, turbo bolts falling out, GM diesels cracking blocks and breaking cranks, or like the gentleman in the first post did, you could bash the I-6 design because of cummins lift pump and injection pumps problems).
The point is each diesel in a light pickup has had it's own particular problems, and most of those problems have NOTHING to do with the I-6 or V-8 design in and of itself, so the arguement this gentleman began was biased and false to begin with..... just more crap and reason not to surf these forums. I for one enjoy reading about diesel engines, finding true and relevant information, NOT listening to someone else's biases.
I'm not sure we've advanced the quest for knowledge very far. I know we all have our favorites, but wishing somethere were true doesn't make it so. The bearing surface observation makes some sense if we're truly comparing surface area and not just numbers. But the number of parts argument seems a little thin. The 24 valve Cummins has MORE parts than the 16 valve PSD for example. I haven't heard of any million mile V8 diesels, yet, but they may be out there, and there are well documented cases of million mile light truck gas V8s. I would expect a well maintained, slower turning diesel V8 to do as well or better.
I'm still wondering if the I-6 configuration isn't chosen just because it's a simple design easily capable of cranking out the low end grunt without a lot of drama. But, remember, if you've checked out the tach on a BMW lately, (SoCalDmax might be able to verify) the I-6 arrangement can buzz right up to the soprano range in an oversquare short stroke design.
Cheers
TC
D-max Man
05-09-2003, 08:53
There were several good points made in this discussion. I do have a question about one that always seems to pop up during these debates.
I am referring to the "I-6 engines are easier to cool" statement. The argument here is that there is airflow around both sides of the cylinder and therefore it can cool off better than V-8 engines which are siamesed on one side and thus trapping the heat in. While this is true, there is another side to this argument that always gets forgotten about.
With the exception of the DDC 50/60-Series, all of the engines have the water pump mounted to the front of the engine and the water flows back from front to rear. By the time the coolant gets to the rear cylinder, it has cooled down all the cylinders to that point which has increased the coolant temprature and thus reduced it
there is two less things to think about so two less headaches
all huge engines, like this kawisaki plant are inline engines, up to 16 cylinders long!!
http://www.members.shaw.ca/diesel-duck/machinery_page/diesel_engine/diesel_engine.01.htm
i have also been told that v designs always work agenst each other as both banks heat up first but the intake stays cool, thus it creats stress withen the engine.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.