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Old 11-16-2012, 05:04 PM   eBay Motors  #1 (permalink)
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v8 diesel vs. I6 diesel

Ok guys first off I just want to say I love my truck, but I am just wanting to know why you guys believe a v8 diesel is superior to a I6 diesel. I have been wanting to find this answer for some time now. I'm not just talking Power Stroke, Cummins, and Duramax. I'm talking just design in general.

What has really got me thinking about this more and more is you will see on youtube that A LOT of the road trains down in Australia are pulled by v8 Macks, where as here in the states you hardly ever see a v8 semi.

Thanks for reading and answering guys
Michael
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Old 11-16-2012, 05:47 PM   eBay Motors  #2 (permalink)
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First off, this is just some opinions I have just to be able to add to your thread. I am not overly educated on the subject so none of it is necessarily fact. I think they both have their advantages and disadvantages. In my opinion, an inline motor is probably the better design when it comes to a truck that pulls a lot of weight as its sole purpose. They inherently produce more torque at a lower rpm than a v8 diesel does. However, I don't think they have the RPM potential that a V design can have. They also generally have a very strong foundation by design. I think the length of the crankshaft allows more main bearing surface, but this design also takes up a lot more room and weighs more than our v8's. I'd say a big reason you see the v8's in pickup's like ours is the fact it can compare in size to a gas counterpart. The cummins engine is pretty tall as well as long. Not saying they cant put it in a pickup, as it obviously fits. I think a v8 works well in a pickup application as most people that own them don't need to make power as low as an inline, and the RPM potential makes them very streetable. The are a decent amount of V-design diesels that aren't so great compared to an inline cummins in my opinion. I feel the duramax is the exception, not the rule. It has been well engineered and updated frequently as problems were found.
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Old 11-16-2012, 06:34 PM   eBay Motors  #3 (permalink)
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07keo02 pretty well nailed it. Inline engines do produce torque at lower RPM but don't like high RPM's in general. The bigger you go the less they like to run the high RPMs. Cummins actual makes v-8 diesels or use to anyway. Cat makes some of the biggest v style diesels for some of there big off road equipment. Big rigs run inline mostly do to fitment and the low end torque. Which most V style diesel will produce peak torque a few hundred rpms after a similar size inline now. It isn't so much that they produce more power or torque then v8s anymore it's mostly come down to fitment. The V8s seem to be easier to produce big power with and also seem to be able to spool larger turbo's more easily then an inline of similar size.
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Old 11-17-2012, 11:46 AM   eBay Motors  #4 (permalink)
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I work at Cummins so I deal with the inline motors daily. Cummins does make a V8 engine called the V903 which is mainly used for military perpouses now. Inline motors have larger bearings areas for the rods. The also have less side loaded of the piston which is inherent of a V motor. Cat does make very large offroad V motors (254 liters V16) Cummins also just started making a 95L V16 called the Hedgehog with an option to go larger in the future. Inline motors are longer and taller due to the design and being able to get the stroke and bore spacing needed for a larger displacement but with only 6 cylinders. In my opinion inline motors are easier to work on. Each engine has the pros and cons.
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Old 11-17-2012, 12:02 PM   eBay Motors  #5 (permalink)
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the mack superliners your talking about has the cat 3208 eng they were great eng but in big trucks now the I6 like the 3406 cat are better from 1980s-2007 all junk after that
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Old 11-17-2012, 03:04 PM   eBay Motors  #6 (permalink)
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Thanks for the input guys. Now you guys talking about the big cat motors in off road equipment, why does cat use a V for that? Wouldn't a inline be better since it has a bigger stroke?
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Old 11-17-2012, 03:14 PM   eBay Motors  #7 (permalink)
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Quote:
Originally Posted by mpeters0991 View Post
Thanks for the input guys. Now you guys talking about the big cat motors in off road equipment, why does cat use a V for that? Wouldn't a inline be better since it has a bigger stroke?
i would think that overall engine size has alot to do with it. you can really only make a motor so big before it becomes more efficant to add cylinders. a V-8 would be a much better fit than I-8.
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Old 11-17-2012, 04:47 PM   eBay Motors  #8 (permalink)
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Like stated before a V motor is better suited than an I because of the packaging of the engine when they become that large. A V engine also helps with packaging of the turbos an aftercoolers since they can be put in the intake valley. I know for a fact the turbos on the large CAT motors are the size of a pizza pan and there are 2 of them on those engines. The large engines are low speed engines so max rpm is around 1100rpm. This is mainly due to engine vibrations with an engine that large
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Old 11-17-2012, 04:55 PM   eBay Motors  #9 (permalink)
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Inline 6 has half as many moving parts as it's v8 counterpart. Half as much to go wrong....at least on paper.
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Old 11-17-2012, 04:56 PM   eBay Motors  #10 (permalink)
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I think inline motors are smoother.
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