Why do Semi-Trucks Use Inline-Six Engines?

by



Commercial trucks use the inline-six configuration because it’s not a space limitation, allows them to run a big stroke which means more torque, it’s mechanically simpler and more reliable than a V engine, offers improved bearing space and load for the crankshaft and connecting rod bearings, and it’s inherently balanced, which means it doesn’t need balancing shafts.

Check out our website: dustrunnersauto.com
Follow me on Instagram: @bryce.cleveland

Gear I use to shoot my videos:
(Buying through these links supports the channel)
Panasonic G7: https://amzn.to/2FKsmKe
Panasonic 25mm F1.7: https://amzn.to/2X8LQhG
Rode Mic: https://amzn.to/2J0lrik
Tascam DR05: https://amzn.to/2LvYFjR
Neewer lights: https://amzn.to/2Xem68x

– Disclaimer –
This video is fair use under U.S. copyright law because it is transformative in nature, uses no more of the original than necessary and has no negative effect on the market for the original work.

source

41 thoughts on “Why do Semi-Trucks Use Inline-Six Engines?”

  4. 5:38 “Horsepower is irrelevant”
    Eeeeennnt! Wrong
    Wheel torque is what moves the vehicle, unless the powerplant is a 1 to 1 gear ratio with the wheels this is true then. But ALL motor vehicles are gear reduced unless intended for speeds above 300mph. Horsepower IS the same as wattage and is the total work produced, and since Semi’s almost always have a ton of gears means a low hp to weight ratio which we all know when they’re taking up both lanes in a mountain hillclimb. Low HP “High Torque” diesels slow way down going up hill, but higher HP still “High Torque” diesels fly up the hills in a similar gear. (Because they can still pull at higher rpm’s, shhhh, it’s a secret)
    But to the original point, the fully loaded semi only needs a fraction of big horsepower to cruise down a flat road so is why low revving high low-end torque diesels are king, lower rpm’s have less friction and get higher mpgs.
    That’s it.

    Reply

  5. The torque and fuel economy of the i6 can be explained by the firing order. In all engines bar the i6 and i8, the combustion will happen when the previous cylinder is at the end of the stroke. In the case of the i6 and i8, combustion happens when the previous cylinder is halfway through the stroke. Thus continuese torque and higher fuel consumption.

    Reply

  7. My first was a '79 Ford mixer with an Detroit two stroke supercharged inline six with a 8 yard smith mixer. I drove some mixers with v-8 cats and even drove a '73 Brockway. Don't know what engine it had. My present day right is a Mack which I do like because it doesn't consume oil like Peterbilts do.

    Reply

  12. European truck makers all had V8 (and V10 and V12) engines the reason they don't produce it anymore (besides Scania) is very simple: they cost lot more money than the S6 (or I6), and can have very similar power at general cargo hauling. And modern engineering developed to that point that an S6 can be as powerful as a V8, so for less money same power.

    Reply

  20. thanks for the info-clip and yes, I am a Diesel guy and yes, I had one each V8 Diesel from Ford and Chevy and no, they are not my type and yes, I (after driving 18-whewelers many moons ago) ended up with a Cummins powered pick up and yes it's the way to go even
    though I wouldn't touch the newer computerized DEF Ram's with a broomstick!

    PS: What's the uncool deal wearing the cap backwards?

    Reply

  23. 5:46 So close, but missed it.
    Torque doesn't say much about how good a truck is at hauling a load uphill. A human with a big breaker bar can deliver as much torque as a truck diesel does, but we sure can't haul a big load uphill.
    A sports car engine delivering 500hp or a truck diesel delivering 500hp, both geared in such a way that the road speed is 60mph at the RPM where it delivers its maximum power, both give the same amount of torque at the *wheels*.

    You could literally haul a 45 ton load uphill with a Ferrari engine, provided you give it a CVT to keep the engine spinning at its maximum power point (though i reckon it would wear out or overheat if you would actually try it, but that's not related to torque).

    The torque delivered by each engine is radically different, but the torque you measure at the wheels, after gearing down, is the same.

    Why don't we use sports car engines in trucks? Because the low torque means you need a high rotational speed to put out the same amount of power. Or in reverse, because you want a lightweight engine, parts have to be small, and can therefore handle little torque. To keep power high, you have to increase speed.

    High engine speeds often are correlated with lower life span. A diesel that tops out at 1500rpm will run for a million kilometer. A sports car engine is still deemed acceptable if it conks out at 100.000km.

    So in short, a truck doesn't need torque as a starter, but it is a dependent variable when designing for power and longevity. And to make an engine that has good power and longevity, it means you need a low revving engine. Finally, to reach the set amount of power with a low revving engine, the engine has to deliver more torque. It's the final part of the chain.

    If i were were rich, i'd stuff some kind of sports car engine into a lorry to for once and for all demonstrate how torque, power and engine speed are related to each other. It's all physics and mathmatics.

    Reply

  34. Does anyone know what Cummins engine our family boat might have had in it? It was a 6 cylinder in line, and adapted from the truck version at the time, which was 1968 or thereabouts. We used to see it on cab-over trucks of the era, where you could see large parts of the engine. It was a common motor, but I can't find any info on it. It was a beautiful thing to me; I was small and it was HUGE! It's so long ago no one really cares lol Peace!

    Reply

  36. Inline 6 engines DO produce more TQ than ANY other style of cylinder arrangement because it allows the power stroke to apply force to the crank shaft for 120 degrees. I believe the 90 degree v style engine is the second best at 90 degrees of rotation being useful to power production.

    Reply

Leave a Comment