There's A Good Reason Semi Trucks Don't Use V8s:
V8 engines are among our favorites . They make big power and sound that is, in the vernacular of Boston, wicked awesome. It's only natural to think that such big engines would power the big semi trucks that transport most cargo in the U.S., but that isn't true. Instead, you're more likely to find an inline-6 under the hood of most modern semis.
There are some important reasons why V8s have fallen out of favor in trucking. A V8 makes great horsepower, but towing heavy loads is all about torque. The inline-6 engines powering most modern semis make between 400 and 600 horsepower. That's not much more power than a well-equipped pickup truck these days, and is likely all the horsepower you really need anyway . However, most pickups don't make anywhere near the 1,000 to 2,000 pound-feet of torque that semi engines do. Big displacement in the 13 to 16-liter range, turbocharging, and diesel power maximize torque, and it shows in those four-digit figures.
Another factor is that in the U.S., semis are typically limited to a maximum weight of 80,000 lbs. Scania makes a 16.4-liter V8 producing 2,350 lb-ft used in Europe, but many of those countries allow heavier loads than we do. A smaller inline-6 can handle lighter American loads just fine.
The fundamental nature of an inline-6 is simpler than a V8. There's only one cylinder head, not two, so it has fewer parts. It's also easier to access and work on, reducing both maintenance costs and the time the truck is off the road. All this, plus its low-revving nature, makes the engine slightly more fuel efficient than a higher-revving V8. It's not much more efficient, but when you're talking six to eight MPG, every little bit helps and makes a big difference over thousands of miles.
The final nail in the V8's coffin was increasingly strict emission regulations for semis. It's easier to get a smaller displacement inline-6 to comply than a bigger V8, so that's what most manufacturers chose to do. In contrast, some companies like Caterpillar simply quit producing semi-trucks, focusing instead on off-highway applications. While electric options like the Tesla Semi may play a role in the future, the inline-6 remains the workhorse of American trucking for now.
Read More: https://www.jalopnik.com/1906098/why-semi-trucks-use-inline-6-not-v8-explained/
(Score: 5, Insightful) by VLM on Sunday May 03, @03:15PM (11 children)
Not bad for AI
There are two issues the AI missed:
1) Its mostly a cost thing. Its all about great big fleets and if 6 cyl saves a penny on each engine vs a V8 then you're getting a 6 cyl.
2) The "cool thing" about a V8 is they are squat and short and back in they days of lame turbos and low power per cubic inch, this mattered. Now a days you can get enough power out of an inline so its not worth the effort. I think people (and AIs) who've never lifted a hood don't realize if you "folded" the two sides of a V8 upward, the cylinders would overlap almost entirely. A V-8 is a technology for fitting more cubic inches of cylinder in per foot of engine length which was a big deal way back when diesels were trash (like when a WWII era diesel was bulletproof reliable for ships but it weighed 5 tons and only output 100 HP for alternators aux power, but on the good side it was indestructible). Now a days if you want a 500 HP inline its just a bit of cad/cam work and fancier turbo and fancier injectors and fancy engine computers. "Back in the day" if you wanted to fit 500 HP of displacement under the hood you needed two 250 HP "wings" of a V-8, but no longer.
3) The natural extension of "cram more cylinder volume in per foot of engine length" is WW2 rotary aircraft engines which are pretty much gone. Its a PITA to make V8s and rotaries compared to a simple inline. If you don't need to, you wouldn't. Back in the day you had to. With modern tech you don't have to, so nobody does that anymore.
Basically you can't justify the cost to build more cubic inches when its so cheap to get HP and ft-lb out of cubic inches in a cheap simple inline in the modern era (lets say post Y2K)
(Score: 5, Informative) by JoeMerchant on Sunday May 03, @04:43PM (5 children)
Don't discount the cost (and complexity) of labor. Truck owner/operator friend of ours got stuck rebuilding his own engine because the local shops were backed up with more work than they could handle, so they gave him a bay, let him borrow tools and talked him through the process instead of making him wait a month to get his rig back on the road. That same constraint still applies to the big, well funded, fleets - the simpler your engines are to fix, the less time they'll spend off the road due to labor constraints.
🌻🌻🌻🌻 [google.com]
(Score: 0, Disagree) by Anonymous Coward on Sunday May 03, @10:58PM (4 children)
Modern cars are actually easier to fix if you have the diagnostic tools. They tell you what's wrong with them and the parts to replace. Those "simpler" engines you had to know your ish and diagnose by symptom. Accessibility itself varies from vehicle to vehicle.
(Score: 4, Interesting) by JoeMerchant on Monday May 04, @01:19AM (3 children)
Meanwhile, I have a perfectly mechanically functional V8 sedan that has been laid up for a month while an expert mechanic specialist in the particular (W220) model uses all the best factory CAN bus diagnostic tools and scratches his head about which $800 module needs replacement.
🌻🌻🌻🌻 [google.com]
(Score: 2, Informative) by Anonymous Coward on Monday May 04, @03:36AM (2 children)
Yeah, parent AC is shockingly wrong. Not sure how people can be so ignorant. He doesn't seem to understand how complex the newer cars are, and that flaky connectors can cause many incorrect trouble codes. Sometimes a flaky / weak / defective sensor can "throw" incorrect codes, or throw other things off such that you get incorrect codes and waste time and money replacing otherwise perfectly good sensors and / or modules.
Older pre-computer car: there are only a few things that can go wrong. I think a stretched / slipped timing (cam) chain was one of my more difficult diagnosis, only because I'd never seen it before.
One of my newer cars has two CAN busses. The high-speed one- the important stuff- had been wired incorrectly, badly violating CAN bus wiring rules. It is truly amazing that the car ever ran, let alone for 14 years. Corrected the wiring and my trouble codes are all but gone.
(Score: 0) by Anonymous Coward on Tuesday May 05, @12:52AM (1 child)
> Corrected the wiring and my trouble codes are all but gone.
Very interesting. We process data that comes off CAN bus systems that often have 500 data channels/sensors (people upstream from us build and run these data acq systems). Often there are problems with the data and the typical approach to diagnose is to look at the sensor. But maybe we need to look at the system wiring as well?
Any references you can recommend?
(Score: 2) by RS3 on Wednesday May 06, @01:02AM
I'm an EE, somewhat into cars, been doing all my own repairs, well, for a very long time. Aforementioned car is a 20 year old Volvo. It's all Bosch (German) electronics. Not sure who made the wire harnesses.
You can do a websearch on CAN bus wire rules, but I'll summarize. It's a differential signal, a bit asymmetrical, but like most differential communication mediums, it's to be twisted pair, with a bus terminator at each of the two ends. You're allowed up to 1 foot (30 cm) or so for a "stub" - a short branch off of the main bus to a device. (other differential examples: Ethernet, USB, RS485, ...)
I bought the car cheap knowing it had (many) problems. I had some difficulty reading the high-speed CAN bus devices, and could barely read from the electric power steering pump. It's down in the right front, just in front of the right front wheel.
Long story short, I tore into the wire harness and found what I suspected: the main CAN bus ran behind the engine, and they tapped in a "stub" to go to the EPS (Electric Power Steering) pump, at least 2 feet. Maybe just as bad, wire wasn't twisted very much.
Twisting a differential pair does interesting things. It causes "mutual shielding", and allows the wire to become more like a "transmission line"- much more stable and efficient at carrying high frequency signals. The main difference between CAT3, CAT4, CAT5, CAT6, is the higher the number, the more twists per unit of length. The more twists, the cleaner the signal will remain, so you can push the speed up.
Tearing into wire harnesses isn't fun, but I spliced in some wire to take the CAN bus down to the EPS, a very short stub tap, then more twisted pair up and spliced in where I cut it to add the correct loop of twisted pair. All made me wonder if there were other compromises with CAN bus wire, taps, etc.
It sounds like you might not have control over the physical wiring. Sounds like factory sensor / controller systems? I've done some of that too.
There are limits to the total length of a single CAN bus. That's a lot of devices, so I might wonder if they're all on one CAN bus? Or are there many busses connected to a multi-port hub (gateway / concentrator)?
There are CAN bus analyzers that can check for signaling problems, data errors, etc. In most communication systems there's the OSI model and layers. There are protocol layers at the hardware level that most upper layers might not see. For example, and Ethernet interface does hardware protocol / handshaking voltage timing verification, conditioning, error checking, etc., so you might need an analyzer to find where the problems are. You might be able to rent one.
Again, critical that there's a terminator resistor at each end of the CAN bus, normally 120 ohms. So anywhere along the bus, with things turned off, you should read ~60 ohms wire to wire.
Many times there will be a device at each end, and it might have a switch or jumper to enable an internal 120 ohm resistor. Maybe someone forgot to do that? An actual resistor would need to be added if the device doesn't have built-in terminator option.
This is interesting, LMK.
(Score: 4, Interesting) by epitaxial on Sunday May 03, @07:19PM
Jalopnik is nearly 100% AI now.
(Score: 2) by mcgrew on Monday May 04, @01:28PM (2 children)
The whole point of the number of cylinders is to tamp down vibration. A V8 takes less room than an inline eight cylinder and its V shape makes it more efficient.
What it sounds like has nothing to do with it. Obviously, the submitter was younger than my kids, I'm guessing early twenties. Kids love noise.
How does the way the pistons are aligned have anything to do with its torque? Torque is the reason semis use diesel and trains are electric, even diesel doesn't have enough torque to pull a train, its diesel engine runs a generator that powers the electric motors.
My dad's big brothers fought a world war against men like Donald Trump and his cabinet when he was a teenager.
(Score: 2, Informative) by pTamok on Monday May 04, @02:00PM
Cough.
There's a few diesel-hydraulic locomotives that would like a word with you...
https://en.wikipedia.org/wiki/Diesel_locomotive#Diesel%E2%80%93hydraulic [wikipedia.org]
https://en.wikipedia.org/wiki/Voith_Maxima [wikipedia.org]
(Score: 2) by lentilla on Monday May 04, @02:02PM
I'm sure diesel engines have plenty of torque, it's mainly the torque from stationary that's the problem. So you run diesel-electric [wikipedia.org], ditching the torque convertor and the gearbox, and you get maximum torque from stationary and have less stuff to go wrong. Well, that's how understood it, anyway.
There is something about certain cylinder combinations being less prone to vibration. Something to do with avoiding the need for balancing components which I've never fully understood. Certain combinations of which straight sixes and ninety-degree V-8 avoid these issues. Somebody else might be able to chime in on the details here.
(Score: 2, Funny) by DECbot on Monday May 04, @07:11PM
4) The V8 engine is for JavaScript. Serious long hauls should use strongly typed, compiled languages. Interpreted languages tend to run slower, and JS ends up being a spaghetti mess after a few years after it gets thrown over the wall into production. This makes maintenance of the codebase much more difficult as the tech debt grows. Yes, V8 accelerates JavaScrpt, but it would have been faster in C, and even faster if baked in hardware. (Also, the V8 JavaScript engine is also a Google product.)
cats~$ sudo chown -R us /home/base
(Score: 5, Funny) by pe1rxq on Sunday May 03, @03:29PM (15 children)
The V8 is only really needed for a few niche products.
Most of the time it just acts as a penile prosthetic.
Why they love it in the U.S. I don't know... they probably have lots of niches...
(Score: 0, Offtopic) by Deep Blue on Sunday May 03, @04:23PM (9 children)
What the fuck is wrong with you?
You don't have to start calling people names, just cause you don't understand something. Better a "penile prostetic", than being an dumb asshole like you.
(Score: 3, Touché) by Anonymous Coward on Sunday May 03, @05:15PM (3 children)
You were saying?
(Score: 1, Offtopic) by Deep Blue on Sunday May 03, @05:31PM (2 children)
Yeah, you left out the important part, so pretty much missed the point there. Just calling it out like it is. I can break that down for you:
The dumb-part comes from "not understanding something someone else likes, but themself not liking it". You don't need to understand it, but you can leave it be, if you are not interested in it and not act like you are somehow superior for not liking it. The asshole-part comes from mocking people for liking something they do not like.
Got it?
(Score: 2, Troll) by pe1rxq on Sunday May 03, @07:55PM
That is a lot of words... So you like yelling 'vroom vroom' while masturbating and you are pissed I did not share your fetish?
(Score: 0) by Anonymous Coward on Monday May 04, @03:23AM
You must be new to the Internet.
(Score: 2, Troll) by pe1rxq on Sunday May 03, @07:52PM (3 children)
I guess you are a v8 enthousiast in a not-so-niche area? Does it come with a gun-rack and a MAGA hat?
(Score: 1, Troll) by Anonymous Coward on Sunday May 03, @11:00PM (1 child)
My prius came with a copy of Das Kapital and a coupon for sex change surgery. They just know their demographics, is all.
(Score: 3, Insightful) by mcgrew on Monday May 04, @01:37PM
There's a drinking buddy of mine, a MAGAT, who was sure I was a Democrat because I drive an EV. That's really stupid, I bought it so I wouldn't have to stand in the freezing weather babysitting it while it fills.
If they still had full service gas stations I'd still be driving a costly, inefficient gasoline burner and like everyone else wouldn't have a clue about EVs' many advantages.
But IMO anybody who chooses ANYTHING, especially something costing thousands, on the basis of politics is an idiot who needs help tying his shoes.
My dad's big brothers fought a world war against men like Donald Trump and his cabinet when he was a teenager.
(Score: 2) by Deep Blue on Monday May 04, @03:55PM
You don't know me, yet you keep being an asshole.
Seriously what is wrong with you? You just continue mocking something you understand nothing about. You are the one with the maga hat or some woke feather. Both just as bad. Both people who mock everything else than what they deem acceptable.
Weird thing that you are so obsessed with other people's dick size. Tell s a story about you.
(Score: 1, Informative) by Anonymous Coward on Monday May 04, @06:57AM
Good Lord...I thought the comment was hilariously accurate, given I am an American and have witnessed first-hand demonstration of the described phenomena.
Yes, I own one of these huge, heavy machines, 7.3 Liter, Naturally Aspirated. Diesel.
Mine gets a steady diet of animal fat from a meat-rendering plant. A local ARCO station carries it. B99.
I bought this machine over 20 years ago. It was old then. All warranties expired. That old machine continues to haul me and my crap all over the place. Admittedly, it had intermittent electrical problems when I got it. Eventually, I have got those either fixed or personally redesigned.
I wouldn't have a new diesel. The new ones are way too finicky and failure prone for my taste. I wonder why anyone would want one. Big PITA as far as I am concerned. From what the old diesel mechanic advised me, there is only one other Diesel design out there better-designed than my International Harvester 7.3 Liter purely mechanical IDI engine, and that is second-generation Cummins 6BT.. apparently, it is even higher compression and will start sans glow plugs. I seem to have a natural sense for properly controlling glow plugs, so being the existing glow plug controller was causing so many problems, I replaced it with an industrial Emerson White-Rodgers refrigeration contactor and a spring-return toggle switch. Ten years now - no more problems or destroyed plugs.
,
Everything is driven via shafts, cams, and gears, I chose it for its simplicity and its reliability.
I really like the simplicity of this beast. There simply isn't anything out there I would rather have.
And anyone thinks it's a penile enhancer, let me brag that in its present naturally aspirated configuration, under optimal conditions, it's rated for a whopping 185 horsepower. I have the fuel injector dialed way lean, as at times at elevation ( Cajon Pass ), this thing can barely get enough air and tries to roll coal. I pull every trick I know to keep it from doing this.
Diesels have some limitations that either make messes and destroy engines if one is unaware of the thermodynamics they operate under.
I suppose if I really worked at it, I could get a speeding ticket... but the only attention from Law Enforcement I have gotten in this thing was a supposed illegal left turn ..that I didn't do! I had not even got to the intersection yet where I was written up for doing the deed.
(Score: 3, Funny) by Rich on Sunday May 03, @09:15PM (3 children)
Congratulations on the coveted (Score:5, Troll) moderation! One less life achievement to check off. :)
(Score: 3, Interesting) by corey on Sunday May 03, @09:25PM (2 children)
For the most part the only people here (AU) who drive those huge American Utes with gas guzzling V8s are men. It does seem like a masculine ego thing. But I get it doesn’t really need to be said here I suppose , it just offends people.
(Score: 0) by Anonymous Coward on Monday May 04, @03:26AM
I'm in the northeastern USA and a co-worker drives a Holden (Chevy) SS with a V8, probably 5.7L but I'm guessing.
(Score: 2, Informative) by Anonymous Coward on Monday May 04, @03:40AM
> ... drive those huge American Utes with gas guzzling V8s are men.
I see plenty of women (all sizes) driving pickup trucks and large SUVs here in the USA.
Just wait a bit and, assuming that US car culture is still a worldwide thing, this will make it to your part of the world fairly soon (unless your country has import restrictions or tax/gas-tax penalties for large vehicles).
Btw, in addition to the reasons given by VLM in his first post, another reason to have more cylinders is smoother power delivery, more power pulses per engine revolution. Before V8 engines were popular, some luxury cars had straight 8 engines (as an upgrade from a straight 6). Moving up still higher in price, for many years there have been V12 & V16 engines in the top class of luxury cars. While they may make more power, the smoothness of the power delivery is a big part of the attraction to more cylinders.
Before the BEV converts check in, I'll just mention that electric motors check all the same boxes, assuming they have enough motor poles to not have significant cogging effects (varying torque output relative to rotation phase angle).
(Score: 1, Interesting) by Anonymous Coward on Monday May 04, @03:52AM
V8s give good power, smoothly. The more cylinders you have, generally the smoother the engine feels due to more overlap between piston / cylinder power pulses.
Don't take that too far- for sure you can hotrod them and they won't be so smooth.
V8s tend to be a good compromise. V10 and V12 would be smoother, but obviously more costly to build and maintain, so they're generally only used in high-end luxury and performance / sports cars.
Some V6s have been some of the most powerful production engines, for example the turbocharged Buick 3.8L in the Grand National / GNX was one of the fastest production cars ever in its time- late 1980s.
All that said, my turbocharged 5 cylinder is remarkably smooth.
(Score: 1, Informative) by Anonymous Coward on Monday May 04, @03:59AM
This keeps coming around, it seems that the AI (tfa author) is just parroting what ignorant journalists have been writing since I can remember.
> A V8 makes great horsepower, but towing heavy loads is all about torque. The inline-6 engines powering most modern semis make between 400 and 600 horsepower. That's not much more power than a well-equipped pickup truck these days, and is likely all the horsepower you really need anyway.
If you want more torque at the drive wheels, use a lower gear. It's really that simple. It's true that diesels usually make a lot of torque at low rpm, where higher-rpm gas engines are designed with the torque peak at higher rpms, different designs for different applications. Compared to most light vehicles, trucks are vastly underpowered, look at all the low gears they need to get started, and notice how loaded trucks slow when climbing gentile hills.
The real reason that truck engines are larger displacement and/or turbocharged (and thus make more torque at the flywheel) is because they are designed and rated to operate near peak power all the time. The "little" pickup truck V8 might make 400+hp peak, but it won't last long if it's operating at that power all day--it's designed to operate at an average power well below the peak power.
(Score: 3, Interesting) by lars_stefan_axelsson on Monday May 04, @06:52AM
Well Bruce Wilson does not agree: https://www.youtube.com/watch?v=gwBQwkSBT-U&pp=ygUPdXMgc2NhbmlhIHRydWNr [youtube.com]
He's famously managed to license a Scania V8 for US use (it's complicated) and reactions are very positive. So he'd like a V8 at least... (But of course not just for the V8.)
Stefan Axelsson