Gasoline Vs Diesel - 4 Major Differences

[@FourTwenny]

Honestly, this youtube channel is part of the internet that that makes me proud to be an information sharing human being. No banter, no politics, no beliefs. Just mechanical engineering that just is how it is.

[@786ALHAQ]

+FourTwenny THUMBS UP . FULLY AGREE. THIS IS WHAT THE INTERNET SUPPOSED TO BE FOR. SHARING KNOWLEDGE.

[@gweedomurray9923]

+COMMENT I love the sharing and Mr. Engineer's explanations are a joy to watch.

[@gweedomurray9923]

+bigstuffeluffaguss ? ? ?

[@FourTwenny]

Gweedo Murray He is being satirical. I cracked a smile at his comment to be honest. I agree with you on the explanations on this youtube channel. I have been subbed for like 2 years now. Hands down my favorite channel. I love how simple and straight forward it all is. I am no great mind, but i leave these videos with some understanding, every single time.

[@gweedomurray9923]

+FourTwenny Or sarcastic ? :-) Around these parts, where "it's legal", that "FourTwenny" has a significant meaning. I follow "Eric The Car Guy" too !

[@bryankirk9450]

This is a person a child like me needed in my youth.

[@Palthewall]

No youtube at your youth though.

[@angelonieuwoudt]

Palraja Pal hope you see this, stfu 👍🏼

[@TheHPGUplink]

This channel kicks so much ass. Keep up the good work.

[@EngineeringExplained]

+Kristian's Battletech Channel thanks!

[@achim07]

you got it a bit wrong there, the amount of "air poisoned" is not a function of A/F ratio but 1) fuel type 2) fuel amount 3) combustion quality

[@achim07]

I'm not saying this is not polluting the planet, you're right there but you're wrong assuming the A/F ratio has something to do with the amount poisoned. The general used unit when talking about pollution is "ppm" aka parts per million which is a concentration, which (multiplied with a constant) can be measured as a mass or mass fraction. See 2) fuel amount, I mentioned. Greenhouse effect differs from generated exhausts, CO is more harmful than CO2, CH4 is more harmful than CO2, SO2 is more harmful than CO2, etc. If fuel is not burned completely like CO or CH4 the combustion quality is lacking. See 3) combustion quality If SO2 is formed the fuel type contains sulfur. See 1) fuel type

[@achim07]

I know what air/fuel ratio means and you repeated very nicely what I said. There still is no correlation between "air/fuel ratio" and "toxic gases produced". So when one engine has an A/F ratio of 100000 and does 900mpg and another engine has an A/F ratio of 10 and does 0.1mpg what engine is worse?

[@achim07]

"if you introduce 5 times the amount of air with each gallon of fuel - you've poisoned 5 times as much air- pretty basic ." This is not how this works as I already explained several times. You can advertise your own channel spreading your own misinformation seven more times but that does not make it true. If you drill a hole in your exhaust and blow some clean air into the exhaust gast, do you pollute more air? If you say yes explain to me where you can inject clean air into the exhaust gases without producing more poisoned gas. If you say no you're right and should think a little further and tell me where the difference between injecting more air than needed before or after injecting it into the cylinder is. Again I am not saying the technology used today is clean or perfect I am just trying to educate. FYI todays diesel engines have such a high A/F ratio because exhaust gas is recirculated to lower the temperature to reduce NOx emissions.

[@EssRoxx]

It's amazing how this dude looks old and young at the same time... Great video though Mr Age Ambiguous

[@Daniel-aaaaa]

Great video! Can your next one be how jdm stickers add 150+ horsepower to my Honda Civic?

[@EngineeringExplained]

+David Fisher Haven't yet finished dyno testing, but it's looking more like 175+ HP to me.

[@BullrullarN]

+Engineering Explained Could be a good video for April fools.

[@Big_Nugget549]

My God he did it

[@Big_Nugget549]

Four years later he did it

[@OustandingTv]

Lmao

[@manugatzi6158]

Forced my kid to watch your channel to quell his questions on what I do in the garage.. ends up asking a lot more about what if's.. learned a lot for you.

[@enrichingexchanges]

I am not an engineer, and I know very little about these topics, but I do find them interesting. Your video was so clear that I cannot tell you how much I learned from it! Thank you!

[@Alpha-Alpha]

this is a seriously good channel!

[@EngineeringExplained]

+Alpha Anderson Thank you!!

[@simeunovicm]

+Engineering Explained what makes air hot to ignate air/fuel mixture in diesel engines? and what is use of intercooler to cool air if you need hot air to ignite?

[@antoinewilly7433]

+simeunovicm When the air is compressed it gets hotter. And I think intercoolers are only used for Gasoline engines. Although, I may be wrong, because intercoolers are made to make air colder. So colder air is less dense, so when air is less dense it means you can get more air into the engine.

[@stevehmi]

+simeunovicm Intake gases are heated by being compressed. In forced induction engines, this phenomenon of fluid mechanics happens twice - first by the turbocharger or supercharger, then again inside the cylinder. The purpose of an intercooler is to increase the amount of oxygen taken into the cylinder by cooling the air that was heated as it was compressed by the turbocharger or supercharger. Then, once the air is drawn into the cylinder, it is again heated by compression when the piston comes up to squeeze all the air that is in the cylinder up into the combustion chamber.

[@stevehmi]

+simeunovicm Intake gases are heated by being compressed. In forced induction engines, this phenomenon of fluid mechanics happens twice - first by the turbocharger or supercharger, then again inside the cylinder. The purpose of an intercooler is to increase the amount of oxygen taken into the cylinder by cooling the air that was heated as it was compressed by the turbocharger or supercharger. Then, once the air is drawn into the cylinder, it is again heated by compression when the piston comes up to squeeze all the air that is in the cylinder up into the combustion chamber.

[@theunknown4772]

You're like Vsauce for the car environment :P

[@maconbacon]

+Danny Contreras Cant like this one enough

[@froggamer4884]

Cars roll..... but why???

[@georgestiller8286]

@Lil' Red GTO damn right!

[@LFSPharaoh]

Seth Spurlock and then that music comes in

[@kingdavewoody]

Next please discuss Diesel vs The Rock :)

[@IlhamDefraN]

+kingdavewoody lol

[@786ALHAQ]

+kingdavewoody BOTH HAVE SMALL PISTONS

[@TheSpacefly1]

+COMMENT W

[@Mickey_Bauer]

Diesel lives a quarter mile at a time

[@koukimonster6957]

kingdavewoody omg dude you had me dying for 2 minutes straiggt bahahahahaha

[@DashboardJesus999]

I find myself already knowing the majority of things you talk about, but the way you present everything and explain it to the audience makes it really enjoyable to watch! Very good job explaining all this stuff!

[@inderawasih1]

Thanks for the video. Very useful. Summary: 1) Presence of external ignition source 2) Feasibility of throttling 3) Air/Petrol compression ratio 4) Feasibility of throttling down

[@navisolim]

i dont understand people saying they hate the diesel engine sound...i love it i dont need any music just listening at the engine working its just satisfying to hear it :)

[@nicholasruiz4464]

That turbo whistle!

[@navisolim]

Salim Saif whats that?

[@Placebo6]

I like both engines as an application, but there is something about high rpm that always gets u, u know? Seat on a cbr1000rr (just an example) and tell me im wrong. Also see amg/corevette/porsche/mustang sounds out there just nasty... Maybe the exhaust helps of course...

[@Placebo6]

One time i revved third gear (again cbr) to a personal record. I felt on drugs from adrenaline. I wasn't even going fast. Your body have to involve its weight to fight the acceleration. Diesel is fun on heavy pulls, where you feel like you are about to move a house if it's in your way. (I drove tanks in military and i am talking in the most literal sense of moving a house, even through the house it doesn't stop, and the engines are not that big, on of the puma's, very small tank, it's either GM or dodge 5.7 v8, but the torque. mmmmaaaaannnn..)

[@Patrick94GSR]

When I was really little in the early 80's my mom had a N/A diesel GM car, some Oldsmobile I think it was, or possibly a Chevy. It was a massive turd.

[@lexusvip4003]

When I need solid information, I usually just look your channel up. My good sir, you are amazing at explaining information. I can tell you truly value your research, and I know you comprehend what you are speaking about. (or you wouldn't make a video on it in the first place) Thank you for these amazing videos. They restore a little bit of my faith in humanity.

[@alterherrentspannt]

Finally, after all my life, I understand how compression braking is different in a diesel engine. Thank You!

[@EngineeringExplained]

+alter Herr Entspannt Happy to hear it, thanks for watching!

[@Taunus-Tim]

but it is completely wrong. the vacuum being pulled in the gasoline engine moves the piston up again with almost the same force, that the piston needed to pull it in the first place. engine brake in a gasoline engine has nothing to do with a closed butterfly valve. in fact, the gasoline engine has a lower braking power when the butterfly is closed as when it would stay open. the brake effect occurs solely because there are friction losses!

[@McDubz]

Just bought a turbo diesel truck came here to learn about this new world I've opened myself up to. Thanks so much!

[@jimmyboy131]

I bought my first diesel about a month ago, an AWD Chevy Equinox. So far I'm seeing around 35+ MPG around the city and 50+ MPG on the highway. Very impressive! And I like the muted diesel "bus engine" sound.

[@jaydavidson7590]

As a fellow alumni of Mechanical Engineering from NCSU (2005) I'm grateful for your channel and the refresher courses! You brought me right back to my seat time in Broughton Hall. Excellent videos and keep them coming!

[@EngineeringExplained]

+Jay Davidson Awesome! By the time I got there most classes were moving out of Broughton (graduated '12). I took statics there, maybe one more. Everything else was EB3, where I lived my last 3 semesters haha.

[@johnnyr25]

a masterclass. well done.

[@arefcr7]

Learned more about engines in 9 minutes than my entire time at school. Thanks for explanation. Keep up the good work :)

[@crissanchez2376]

Thank you man, your videos kind of gave me an insight into engines and cars, I decided to pursue an auto technician degree and am currently loving it! Keep up the good videos!

[@gutadin5]

who is more prone to overheating, gas or diesel? i am torn between the Toyota Prado gas or Prado diesel.

[@allianceofsteel]

man i'm using him from now on.. better than sleeping pills.. everytime I listen.. i'm out.. within minutes... awesome.

[@ismaelochoa6]

😂😂😂😂

[@Jak2bossbf3]

Haha very true

[@allianceofsteel]

if you look above you might see the reason for the comment... not sure why my comments seem so out of order.. but they seem very much out of place.. my apologies.. no disrespect meant if you read my other above comments.

[@allianceofsteel]

nah that couldn't possibly be it.. this isn't like the internet or anything... hehe

[@allianceofsteel]

on a side note.. Quest Remnants of Chaos check it out if you want to... work in progress.. only if you like games.

[@DesHerbert]

+ Engineering Explained. Well explained. engaging and with enthusiasm. Thought I might of turned off but find myself wanting more. I've subscribed.

[@EngineeringExplained]

+Des Herbert Happy to hear it, thanks for watching!

[@AkshayPowale]

+Engineering Explained 39b engine

[@heavymetal375]

+Akshay Powale what?

[@lindahaugh4711]

+Liam Jonigan-McGar A 3.9l 6-rotor

[@heavymetal375]

+Linda Haugh what about it?

[@SirXyloid]

Either I'm just really tired or I never realized how fun it is replying to comments on this channel.

[@yellow5n]

you just blew my mind about the fact most diesels dont have a throttle body, how did i not know this, great video

[@wolfman9999999]

I found a couple of inconsistencies. Diesels do not make more torque due to using more fuel. Diesel fuel has more energy than gasoline and burns slower. This means you get a longer burn duration vs. gasoline which has the flame pushing down on the piston longer during the power stroke. In addition, on a Jake Brake, while yes you are correct that it opens the valve near TDC (not at TDC due to clearance issues) the loss of the air also causes a vacuum in the cylinder which is also adding drag in the engine. As such this maximizes pumping losses within the engine, giving the heavy duty engine the ability to assist in slowing the truck

[@amcheung10]

Could you do a video on air/oil separators and how they work and help an engine

[@paviaaPS3]

great topic

[@mavic999]

+amcheung10 you mean Oil catch cans??

[@paviaaPS3]

+Maveric James Ching or piston rings?

[@guywholikescheese97]

+paviaaPS3 piston rings don't deserve a whole video. they seal the combustion chamber

[@paviaaPS3]

what are they made of, how many, hardness, when to replace, ect. he can esely spent 5 min on this subject...

[@Incendia]

Thanks EE, for yet another simple but brilliantly effective video. This is why EE is one of my favorite car-related entities (spanning FB, YT, etc.). No gimmicks, no controversy, no BS. Just information, presented in a simple, bite-sized manner, for the benefit of all petrolheads. You guys are awesome, keep it up!

[@souritraganguly1631]

Never came across a better explanation. Subscribed.

[@philippeanglade7043]

Hey, could you make a video about compression ratio ? And how it affects torque, power curve, fuel consumption... etc ?

[@Siberworldkhan]

+Philippe Anglade yes.

[@EngineeringExplained]

+Philippe Anglade I have a few, search my channel for "compression ratio" as well as "thermal efficiency." :)

[@philippeanglade7043]

+Engineering Explained Thanks, I just watched them ;) . But I was more thinking of question that could be interresting for petrolheads willing to change their compression ratio. Will the engine produce more torque ? Will it move the torque curve higher in rpms ? Will there be a loss of torque at some rpm ? How may it affect idle ? I know the answers, I'm just thinking it might be a good video idea ;)

[@calhobbes862]

+Engineering Explained This is completely unrelated but is it possible for a manual to have remote start?

[@fitch03]

+Daniel Gamboa Urosa I have had many vehicles with remote start that were manual. You just have to make sure that when you leave your car parked that it's in neutral. Most aftermarket remote start kits have a safety switch that won't even let the car try to start while it's in gear.

[@andy16666]

Modern GDI engines are effectively Otto cycle, with the spark plugs only acting as starting aids. These newer gas engines have compression ratios more than sufficient to ignite the fuel on injection. With such high compression ratios, gas engines are now nearly as efficient as diesels. (11:1 for Kia/Hyandai, 13:1 for Mazda, vs. 14:1 for a typical diesel.)

[@clarkie005]

Correct. Mazda brand it as skyactive but it's basically very close to a Diesel engine

[@rogercoulombe3613]

+Andrew Somerville the Otto cycle is the cycle used by traditional gasoline engines. diesel engines use the more efficient diesel cycle, though you are correct that many modern engines are starting to blur the line between these two cycles.

[@sighingsquid8571]

This guy is amazing! You learn something everyday.

[@Tonygarage132]

You'r a real automotive journalist! Thanks brother

[@traviscook9055]

I understood some of that

[@traviscook9055]

Nope :)

[@Unb3arablePain]

Either way both are much better than burning straight up crude oil.

[@Nikifuj908]

Or whale oil

[@blackdeath4eternity]

think you have a point... we need to build whale oil burning engines!

[@bkehlin]

Thanks to this video, I've finally figured out why diesel trucks have a flap on the top of exhaust stacks. Back pressure for engine braking.

[@mazemakes]

This is great! I want to suggest a sequel, talking about the advantages/disadvantages and applications of the engine types. Like why do diesels not rev as high as petrol engines, why are they "dirtier", in which vehicles is which type best used? etc. Especially in light of the vw scandal an interesting topic!

[@jonnyroy]

Could you talk about exaust gas recirculation, otto cycle engines and the mazda high compression gasoline engines?

[@sweetcheels]

+jonnyroy He's talked about them I believe once before. Search his channel for the videos. I believe they were made either early 2015 or late 2014. But yes, he's made a video on them previously.

[@theoldrsftw]

can you talk about Gas and Nitro Remote Control car engines.

[@prairiewanderer5040]

+theoldrsftw Historically nitro remote control car engines were 2-cycle engines, though there are 4-cycle engines in that class now. They basically function the same as a larger 2-cycle or 4-cycle gasoline engine, except that instead of an ignition system that provides power to a spark plug to ignite the fuel-air mixture, they use a glow plug. The glow plug is first pre-heated by a battery and is then re-heated each time the engine ignites.

[@theoldrsftw]

+prairie wanderer interesting. what is better nitro or gas?

[@prairiewanderer5040]

theoldrsftw It depends upon the application and nitro is a lot more expensive.

[@theoldrsftw]

Thank you :)

[@jamescc133n4]

Thanks for using physical parts in this video, it was much easier to understand rather than whiteboard drawings, keep up the good work

[@MadNotAngry]

Fifty years ago I asked my grandfather why semi trucks made that rapid decompressing sound when braking. He said he could explain it to my 8 year old mind, but it was too complicated. I let the moment pass. Since then till now I've wished I learned this secret. Never knew. Now I do. The circle is now complete.

[@joshthej3di681]

Cummins vs Duramax vs Powerstoke? Whats your preference and why?

[@joshthej3di681]

aeperformance48 I just asked a question...

[@aeperformance48]

you're not allowed I'm your boss

[@joshthej3di681]

+aeperformance48 Good luck with that

[@barath4545]

+Venator Mortis Cummins. Because I have seen them modified and used in way-more-than-designed-for situations and live through. And they also make engines for real trucks (or semi's) and even those can be turbo'd to insane amounts of strain and still live to tell. My current realistic dream car is a Ram 2500 6.7 I-6 Cummins AWD 4-door and then to gradually over the years tune it up safely to Motortrend Truck Challenge Top 10 numbers but keep it street-legal and still moderately economical for road use. Lavon Miller showed us it can be done. I would be happy with 80-85% of what he has today.

[@aeperformance48]

Venator Mortis Im your boss I own you, get used to it kid

[@johnnybow7045]

My question is: How then is a Diesel engine able to start without a spark plug? Does an electric motor or so combust the air at the first stroke? Or how does it work..

[@bogushavis]

When you compress air it gets hot. If you compress it enough, it will get hot enough to ignite fuel. Diesels just compress the air a lot, then fuel is injected and it just burns in the hot air.

[@johnnybow7045]

I understand that but where is the energy to ignite it taken from? If the pistons are in stillstand yet and you wanna start the engine.. How's that happening?

[@bogushavis]

Oh, engines always have an external starting mechanism. Automobiles and trucks have electric motors bolted to the engines that are used for starting the engine. The electric motor is powered by one or more batteries. The energy needed for compressing the air and injecting the fuel to start the engine comes from the battery. Once the engine is started and running, the alternator on the engine does the work of recharging the battery.

[@johnnybow7045]

Thank you mate!

[@krzysztofb7048]

each engine got something called motor started to "spin" the crank + diesel engines have glow plugs which are warming up the mixture before start

[@nickflores6543]

You're honestly the greatest youtuber ive ever watched

[@FugaziSB]

You explain things very simply but keep all the information there, what a great video!

[@Rocky-rm4bc]

I just cant understand it. Why do you call a liquid a gas?

[@thomaseb97]

Gas is short for gasoline, it is not a gas

[@Rocky-rm4bc]

Thomas Brekke ah :D

[@786ALHAQ]

+Rokas Getautas Americans refer to petrol as gasoline. GAS is short for gasoline.

[@JanBabiuchHall]

+Rokas Getautas Yeah, we American's can't be bothered saying more than one or two syllables of longer words. It's kinda our thing. Sorry bout that, bro.

[@mokocono5784]

+COMMENT Benzine or naft here

[@Beyonder1987]

Petrol is better over all. No need to worry about DPF regen. Esepcially if your doing city runs most times.

[@rangerrick1859]

diesel is better for the environment and gets so much better fuel mileage. i have a friend who's father has a vw tdi, he gets like 43mpg highway

[@Beyonder1987]

Ricardo Lupian petrol is getting better and will catch up on diesel in motorway (highway) fuel economy but if your working in mostly city based then just no point with diesel. I had constant DPF issues with my BMW. I drove it 50 miles to start getting it regenerating but kept coming back . Petrol is over all better in my view.

[@rangerrick1859]

i'll tell ya when mazda comes out with their skyactiv diesel, i will be so excited. it is available in other countries but not the U.S. i'll tell ya clean diesels like the vw tdi. will not have any DPF

[@Beyonder1987]

Ricardo Lupian every diesel car had to have a DPF installed by law in Europe

[@rangerrick1859]

my friends dad has a 2013 vw tdi his doesn't have any of that stuff. but a lot of the bigger trucks like f250's have DPF.

[@shayanibrahim4127]

I swear, I absolutely enjoy every single video you release, there is something genuine in your explanation that make me enjoy learning. well done bro.

[@BoccaBastard]

Superb, man! Literally anyone could understand this, the way you present it!

[@Exia2004]

do you have a video about torque? and why diesel have more torque and gasoline less

[@andreisharma]

+Exia2004 since diesels have a higher compression ratio, the crankshaft is bigger than one in a gas engine. this affects the torque ratios giving the diesel more torque

[@MuttleyMutter]

+Exia2004 Torque talk. Torque and power have a fixed relationship, torque x rpm = power. (to be precise Torque (lb.in) x Speed (RPM) / 63,025) = Power (HP) Look at it this way: torque is about how big a bang you make in the combustion chamber, power is about how soon you can make another bang. So, at the same rpm, such as when starting from a standstill, a diesel can apply more power to the wheels, and gets away faster than a comparable petrol engined car. Yes, it has more torque than the petrol engine, but that means that it is producing more power *at that rpm* The downside for the diesel is that you have to change gear earlier, as a diesels power output drops off sharply after about 4000 rpm, for reasons to do with the way combustion works in the diesel cycle. Now, a word about "rated power". Manufacturers will quote their engine power, say, 140 BHP - this is the maximum power the engine is designed to produce within normal operating parameters. In petrol engines this is frequently reached at 7000 rpm or more, wheras for the diesel it is usually about 4000 or a bit less. If you restricted a petrol engine to the same rev range as a diesel of the same rated power, the petrol engine would never catch up with the diesel. To put it another way, from a standing start, the diesel is *always* producing more power, because it is producing more torque.

[@ccmckernan]

how come diesels don't over heat under lean air fuel ratios like gasoline engines do?

[@Karjis]

+Collin Mckernan it is running with seriously excess air, so it is lean enough. So lean that gasoline engines would not even really run with. Also when you have high load, diesel is running richer. With low load it is lean, then amount of heat is limited. Of course slow burning of diesel fuel helps. (diesel burns much like wood, not violently and fast like gasoline)

[@UndergroundTrev]

+Karjis I was going to ask that same question. Great explanation. The example of burning like wood helps to make sense of it too!

[@frankeggers4024]

+Collin Mckernan With gasoline engines, the gasoline which enters the cylinders is not completely vaporized. Much of it enters the cylinders in droplet form. The vaporization of the gasoline in the cylinders has a significant cooling effect. For that reason, air cooled aviation engines, during take off when full power is required, run on an extra rich mixture so the vaporization of the gasoline keeps the engines from overheating. Of course that is inefficient but durability is more important at that point. Not all gasoline engines will overheat on a lean mixture, but the free O2 resulting from a lean mixture can burn valves. Engines running on a gaseous fuel, such as propane or natural gas, do not get any cooling effect from the evaporation of the fuel and therefore tend to run hotter. As a result they often use better materials for the valves to prevent valve burning. Diesel engines generally have excess air so they tend to run cooler. Also there are slightly more efficient which means that less heat has to be removed.

[@Jefff72]

I have a 2006 VW Golf TDI (Euro spec 1.9l) and I love it. If you drive it mellow and smart, it gets awesome fuel economy and yet it has the power available when you need it. It's not going to be winning drag races, but in everyday driving, it's extremely practical. I often commute with 50+mpg and when I need to pass or climb a hill, I have the torque to do so. But with VW's diesel scandal, I like to see their plug in hybrids come down in price.

[@VinayKapoor]

Nicely explained

[@FattyDoveRacing]

Why not show a Diesel engine gutted

[@blackdeath4eternity]

cuz he couldn't find one broken down. lol

[@just5444]

You didn't said most important thing: diesel for power, gasoline for speed 😉

[@ilikepie1974]

diesel for torque and efficency, gasoline for high rev/power

[@yourfavoritelawnguy2722]

actually depending on how much money you have to put into a diesel it can be for speed, torque, and hp, and mpg, but you cant have mpg with the others focused on at the same thing

[@koitorob]

Gasoline for power?How many petrol engine HGVs do you see?What engine did Audi win several Le Mans races with recently?

[@nicholasruiz4464]

Higher fuel efficiency, more torque, and less hazardous handling due to lower combustibility than gasolene. For use in heavy truck applications as well as industrial electric power generators. From your car to your truck to your tractor, to your multimillion dollar oil rig; cleaner, safer, more efficient.

[@Supraman735]

Torque isn't a function of RPM. Horsepower is calculated based on torque and RPM but peak torque isn't always highest in the lower RPMs. When you look at these low displacement N/A gas engine builds that are making big horsepower, the peak torque often isn't that much greater than it is in their stock form. However the curve will look different because the cam profiles, intake manifold/runners and head porting are optimized to make that torque higher in the rev range. Same torque at higher RPM = higher horsepower. Peak torque of an engine can be as high or low as they wanted it to be. This is why VVT is so great for drivability on higher powered low-displacement cars; it allows you to have good torque in the low/mid-range when it's on one cam profile but then when it crosses over into the second cam profile, that one is more optimized to make torque at higher RPMs. It depends entirely on how the people designing the engine want it to function.

[@jnrivers]

Clear explanation. There's more differences between the two than I thought. Subbed.

[@joachimseisay66]

Great video! Simple, economical and informative. I am perusing my helicopter license and needed a cursory explanation. Yours, sir, was among the best I have seen.

[@DonziGT230]

You have the engine braking all wrong, it's the compression stroke that slows you down not the intake stroke pulling vacuum. Wikipedia has it wrong too so unless you wrote the wikipedia on this there's more than one of you who thinks it's the vacuum that provides braking. EDIT: I fixed Wikipedia.

[@EngineeringExplained]

+DonziGT230 nope, compression in gasoline engines does not cause much engine braking. Why? Because all that energy goes right back into pushing the piston down after the compression stroke, very little is lost as heat and thus the vehicle doesn't slow much. I'm sure wiki will go back and fix your mistake, they're generally pretty good.

[@DonziGT230]

I have a stock '88 Ford 7.3 diesel with no braking parts added, open intake and exhaust, and it has more engine braking power than any gas motor I've ever driven due to it's high compression. I've also tested the theory on gas motors by turning the key off and pressing the throttle wide open, no change in braking effort at all with cars, bikes, or trucks. I'll put it out to you or anyone else who wants to feel the truth first hand. Take any traditional gas motor vehicle with a cable operated throttle and EFI, don't wanna do it with a carbureted engine as you'll be pumping raw fuel through the motor and can cause damage. Get going down a hill, turn the key off and move the throttle pedal; you'll find no change in braking effort. If the vacuum theory is true you'll loose all of the 'vacuum braking' when the throttle is opened and you'll find that it doesn't.

[@bogushavis]

Having higher or lower compression does not change the braking effect in a gasoline or diesel engine. GM and Dodge both produce gasoline engines that close off valves to half the cylinders to conserve fuel. This creates an air spring in each cylinder, the force required to compress the air in the up stroke is given back to the crank in the down stroke. A diesel engine that is turning without injecting any fuel is a big air pump. All the braking resistance is due to pumping air through the engine and out the exhaust pipe. If throttle valves have not been added to the intake, no vacuum resistance will be there to add additional resistance to the engine. A real Jake Brake adds braking by interrupting the air spring and wasting that compression stroke out the exhaust. Jake's make a lot of noise because the escaping compressed gas goes supersonic when expanding past the exhaust valve. The smaller the valve opening, the louder the Jake. Exhaust valve brakes just shut off the exhaust pipe and cause the engine to build pressure in the exhaust manifold. Not as noisy, they just hiss. The lack of vacuum is a big bonus for a diesel engine. Very worn gas engines will pull oil down the valve guides and up through the cylinder rings during high vacuum. Worn out diesels don't have this problem. However, diesel vehicles that use vacuum accessories (like vacuum assist brakes) require an additional belt driven vacuum pump. I worked my way through college driving light to medium trucks for a lumber yard. We had several 84-87 Ford diesel one tons with stick shift transmissions. They had almost no engine braking when going down steep hills. We also used 30,000# GVWR "2-tons" with 18' flat dump beds. Most ran gas engines, but mine had a Detroit Diesel Turbo. The diesel had a lot more power, got 10mpg on long runs, but had poor engine braking. The gasser's all had better engine braking. We had a cab-over Peterbuilt with a Cummins and a Jake brake, I only drove it a couple of times and I never did so without the Jake turned on. The Jake was very effective. We also ran a Ford 10 wheeler with Caterpillar V8. It had a hissing exhaust brake. Definitely not as good as the Jake. When it was loaded, if I turned off it's exhaust brake and let off the accelerator pedal, it was just like being in neutral and coasting, no brake effect at all.

[@bogushavis]

Now, about your 88. I believe it is possible for a diesel to develop more engine braking as the engine wears out. When not pressing the accelerator, thus not adding fuel to the engine. The up stroke would "attempt to" compress the air to about 20-1. Air that is lost out of leaky valves and past worn piston rings would not be there to aid in pushing the piston back on the down stroke. Therefore, it might be possible for a well worn diesel to have a kind of Jake Brake effect just due to the worn out condition of the motor.

[@DonziGT230]

The compression on it is good except for one cylinder that's a bit low. I've driven dozens of these from back when they were new and they all had about the same braking effect. Try my key off throttle open test on a gas motor and you'll see that it's not the vacuum that creates braking. I've driven many medium to heavy duty gas and diesel trucks and my experience with their engine braking is completely different than yours.

[@armesisp3201]

Ive owned diesel powered suv's before and i learned only 1 thing. Dont EVER buy diesel powered suv's.

[@max19970]

+Armesis P why not??

[@armesisp3201]

max19970 They are slow, even when turbocharged and stage 1 tuned, produce a ton of smoke even when properly maintained, unreliable and noisy. The worst part is the turbo lag. The only thing good about it was that it was economical, but only a person on pension would worry about that. My turbo diesel car used an italian engine btw, bloody awful

[@L3AP2020]

+Armesis P although alfa romeo's jtd 2.0 liter tdiesel is a one of a kind, used im the 156, and i could give you more examples of top of the line italian diesels. I think you just had a really bad experience with that car, but you shouldnt let that mold your whole idea on diesels. Diesels nowadys have none the issues they used to, with turbo lag being almost unexistant, and noise and roughness being correctly balanced out plus the great efficience that diesels carry in their dna i think there hasn't been ever a better moment to invest in one

[@bosborn1]

+Armesis P I can absolutely guarantee you my 7.3 Powerstroke diesel will generate far more torque and HP than its 460 Gas counterpart. Since modern injection systems came about (HUEI and Common Rail) staring in the mid ninties, the diesel has been king in light trucks and SUV's. The gas trucks just can't keep up. As a person who tows extensively, I would always choose a diesel over a gas motor. Its not just me, I've never seen heavy haulers use gas motors. Not only do they lack the power they generally require more service intervals don't last the 300,000-900,000 miles I expect for a truck.

[@emeraldages]

+bosborn1 YOu have a big ass turbo and a 7.3 l motor. Youre comparing against a smaller displacement non turbo application. Not really a good comparison but I do agree diesel is almost always goign to be better for towing applications.

[@GMAN142006]

Great video man! Simple to understand, yet specific details are not left out.

[@jk0340]

Sir, you are great, technically I'm studying to become a an Electrical engineer but cars are my love and you truly help in fulfilling that.Keep up the good work, ciao

[@jackhills7474]

It's a really good feeling to know almost everything that you talk about, and being able to learn a couple extra things as well. Doing my Motorsport engineering course has taught almost everything you talk about, but then you're able to go into a little more detail so I can learn a little bit more about stuff. And for that, I am extremely grateful :D

[@MFEeee]

Wonderful explanation

[@rickyde0255]

I always enjoy these videos. I wish I understood what he's saying!

[@maplesyrup2944]

This was wonderful.

[@EngineeringExplained]

Thanks Maple Syrup!

[@bumbble]

Everytime, before watching your video i will always say "hello everyone and welcome" with your tone of voice

[@Ahto42]

Jason talked about truck diesel engines about engine braking. Passenger car diesel engines have not any valves in the exhaust and no separate valve control. There is an accelerator off switch on every ECU controlled injection system, diesel and gasoline. Vehicle speed is taken from the gearbox speed sensor of from ABS. If the vehicle is moving and the acc pedal off switch is engaged, then the fuel is cut off, but is restored at low speeds for not stalling the engine. The baking is done by the compression only. The throttle valve may help a bit on a gasoline engine, but it may be un-noticeable. Diesels have higher compression rations and that way we feel more braking with the diesel engine in the same gear compared to gasoline. I own both and have rebuild both engine types(NOT TRUCK/18 wheeler).

[@madmustanggtable]

You answered a few questions I've always had about diesel

[@shameboy2395]

Great video. Couldn't have explained it any better.

[@Tinus001]

With big diesel engines, when you let you're foot off the gaspedal. You say that the exhaust valve is open to let the compressed air out, but does it close to create a vacuum. Thank you for good engineerings video's it helps me be a better engineer :).

[@johnabuick]

Some large diesel engines have a butterfly valve in the exhaust downstream of the turbo charger that blocks exhaust to slow the engine/truck. Other diesel engines like Volvo for instance have a Jacobs head and a exhaust pipe butterfly valve that gives them really strong engine braking. There are also turbo chargers like in the Duramax that have variable pitch blades that restrict exhaust flow to facilitate engine braking.

[@boosted2v749]

As someone who is friends with mostly diesel trucks thank you very much for making this lol. I have a slightly built 2003 gt and they all have cummins, powerstrokes etc and i find it hard to relate to them when we talk cars and trucks.

[@davidpardy]

Thanks for the video! I've been wanting to read up on how engine brakes in large diesels work for a while now, but always forget to. Now I know!

[@VikramRampal]

External spark reduces the mileage. You may have a question that why do we have a spark plug in a gasoline engine? It is because even if you compress gasoline in the ratio of 1:18 or more it wont burn hence it needs a spark...

[@frankeggers4024]

You did very well, especially in explaining engine braking. Some people still think that Otto cycle engines have compression braking. That mistaken idea is repeated over and over. Of course if that were true Diesel engines would have more compression braking than Otto cycle engine do, but they don't. You could also have explained that the main (but not only) reason Diesel engines are more efficient than Otto cycle engines is that the throttle valve on Otto cycle engines creates serious inefficiency but Diesel engines typically don't have a throttle valve.

[@jiroyamamoto2878]

Compression ignition and spark ignition are possible in both 2 stroke and 4 stroke cycles. 1:40. Talk about the sky active which has a 14:1 compression ration in a compression ignition engine. Also, cetane versus octane.

[@ravdeepsinghrayat8361]

It gives the best basic function of a engines. Very good

[@tomwiens3500]

cummins also compounds their compression braking from one cylinder to another, where the air thats released at TDC is then routed through the exhaust manifold into a different cylinder that's on its intake stroke. This effectively crams more air into each cylinder for more aggresive compression braking, or "jaking."

[@chamorroboy9577]

Knowledge is power! Love watching these

[@TheSnoopy1750]

+Jared Borja I agree - EE is the most informative (and interesting) auto-related YT channel.

[@EngineeringExplained]

+Jared Borja thanks, appreciate it!!

[@hansdodel6027]

very good explanation . one thing i missed was why the air is getting hotter on the compressionstroke. and i think u know the answer as much as do so.

[@BBond88]

I learn so much on this channel.

[@chrisbaker2903]

It seems that modern gasoline engines now tend to use direct injection just like a diesel and it should be feasible to run the compression ratio up and run them exactly the same way. The injection at the point in the compression stroke where the spark plug would normally ignite the mixture would initiate combustion the same way it would in a diesel which would allow the same super lean overall mixture but provide the "pockets" of combustible fuel air mixture and thus lead to greater fuel economy in gas engine vehicles. Diesel would still be better for economy because it contains more BTU's per gallon than gasoline. Diesel doesn't burn as quickly as gasoline which is why it's been used for low RPM engines for the most part. Technology is helping with that too. My question is, have the any of the car companies tried this and if so, how did it work out? it hasn't been that long since they figured out how to actually use direct injection on a gasoline engine due to the problems with lack of lubrication for the injectors like that which is provided by diesel fuel. Also, back when I was a teenager some of the higher performance gasoline engines used 14 and 15 to one compression ratios because with the lead additive to the gasoline bringing the octane ratings over 100, they could live with that high of compression. Modern engines are edging up near 12/1 ratios again, due to significant improvements in combustion chamber technology. My Suzuki 650 Vstrom had 10.5/1 compression ratio and ran on 87 octane gas. My mom's 1959 Mercury with 10/1 compression ratio pinged like mad on 93 octane. In the 60's and early 70's, 93 octane was regular and there was a mid range and "Hi test" that was over 100.

[@bogushavis]

Yes, it is called HCCI. The car companies are working hard on the technology.

[@cfwong1d300s]

i dont fully understand what you're talking about, but still, well explained, here is a cookie for you.

[@Psittac20]

Stuff I would have never known otherwise, very interesting things which are now in my brain.

[@JohnWhite-gd4tx]

Good info, but I'm surprised you decided to include engine breaking and not glow plugs.

[@TheKenjoje]

I need to correct one thing here - it's not true that high compression makes the key element in high diesel torque. actually, without turbo, diesels have much lower torque than equivalent petrols. the differences between torque are smaller than those between max. power, mainly because petrols have the ease of high revving. heavier components in diesel engines contribute to good momentum on low revs, but that stops them from reving high. let's take example of last VAG non-turbo diesel 2.0 with 75 hp. highest torque around 2200 is about 140 Nm. highest torque of average 2-litre 8-valve petrol is about 160-170 Nm about 3000-3500 revs and power is about 110-115 hp roughly. that leads to natural conclusion - at about 2000 both have comparable torque and power, only petrol goes quicker through rpm and far beyond diesel, feeling both stronger and more flexible. The proof that compression doesnt play that important part are latest mazda's engines. Both petrol and diesel have same comp. of 14. high for petrol and low for diesel. Desel is not suffering in torque and petrol doesnt benefit. Average 2-litre 16v petrol has it qbout 190-200 nm and mazda's have it about 210.

[@TheKenjoje]

***** if we take a power as criteria, we could compare some 1,4 petrol and 2,0 diesel, both with about 150 hp. then diesel will be also more efficient, but only 'just'.

[@TheHomeless080]

+TheKenjoje 21-24% more efficient thats a lot.

[@TheKenjoje]

INSERT NAMEHERE only in city

[@TheHomeless080]

TheKenjoje thats not true a good gasoline 1l engine makes 55 mpg on highways. A 1.4l diesel does 67 mpg on highways. Thats a 21% improvement

[@TheKenjoje]

INSERT NAMEHERE no and no. we compaaare it on thee base of power. 1 liiitre does well with ttturbo onnnn open road because highhhest gear is very loooong. in average 60-70 hp small engine revvvs go much higheeer on higher speed

[@roadrunnerblink]

Beautifully explained mate. Really appreciate these videos.

[@engrpinakbet24]

Would be nice to have the otto and diesel cycles up there somewhere as reference. After all, its engineering explained :)

[@Luigiweegy]

Any combustion reaction is fuel + oxygen. In a gasoline engine, you control the rate of that reaction by modulating the amount of oxygen (throttle body) and in a diesel engine you do so by modulating the amount of fuel (fuel injector). Neat! I never knew that.

[@brandosuedavison5131]

Please do a video explaining the Eco-Diesel engine.

[@djambush360]

Min: 0:28 Diesel engine uses injection not compression to start the combustion. Also the self-ingition-temperature must be always under the compression temperatur. If it's higher, the engine runs out of control to shut it down and other problems.

[@michaelcopeland8806]

Diesel engines will not start without compression. It is the compression that heats the fuel/air mixture to cause combustion. You can inject fuel all day long into a diesel engine and nothing will happen until you compress it. Compression starts the engine.

[@djambush360]

Michael Copeland _It's pure air that is compressed by the piston. A diesel do not start by compression. You would need no diesel to run the engine then The combustion starts when diesel is injected by a nozzle into the combustion chamber a little time before the piston reaches his highest point. elderly engines had a mechanical injection pump with about 150 bar (2180 psi) pressure. Modern Diesel are reaching 1200 bar (17400 psi).

[@stock9291]

Nope. It uses compression. Diesel fuel is quickly injected (sprayed) into the cylinder just before the end of the compression stroke. Air is heated via compression and that hot air heats those tiny tiny droplets of diesel fuel (in the pocket, as EE said, that has stochiometric mixture), and when those droplets reach self-ignition temperature, they ignite. Also, if the self-ignition temperature is below the compression temperature, the mixture ignites. If it's above, it doesn't ignite. Get your facts straight.

[@charleshamonsjr.8099]

Great video and explanation of the differences between gas and diesel engines. Only suggestion would have been to mention glow plugs and how they function in a diesel engine helping with starting. Where as a gas engine benefits from a spark plug that ignites the air/fuel mixture and continues to fire through out the combustion process. A glow plug is a heat source that helps to raise heat in the combustion chamber so the air/fuel mixture can fire off. It is especially helpful when the engine is cold and or in colder climates. With out it, it takes several cranks to get the necessary heat in the combustion chamber so the air/fuel mixture can ignite.

[@jayperalta2918]

Videos like this make me wish I weathered physics en route to be a mechanical engineer. Great job.

[@ariesmight4141]

I could not find a Engineering Explained video on engine bearings. I came across a diesel engine co called Gardner diesel co. I looked it up on Google. I was really impressed by the quality of engineering and craftmanship that went into them. Their engine bearings are braced both virtically and horizontally. So here is my question. What is a horizontally braced engine bearing?

[@sixroldan6742]

Dude, you're awesome. Thanks so much for this video.

[@FarmYardGaming]

Very very close to 3 million!

[@scottmkm8214]

I really enjoy your videos. I feel that your diesel "jake" brake explanation was incomplete. It's the release of the high velocity compressed air into the exhaust which spools up the turbo. That creates more intake manifold pressure and even greater braking power.

[@abeycivic7.014]

Great video man, I love watching you're videos and learning more and more from you. Great teacher!

[@MrGreyLeaf]

Great video, thank you for explaining. This was of interest as we recently purchased a Jeep diesel. Keep the videos coming Sean

[@ThoolooExpress]

This video answered a lot of questions, but it brought up one new one: Why is engine braking so important that it has to be added in to engines that don't do it on their own? It's not like friction isn't going to slow a car down once the engine isn't producing power.

[@UDumFck]

+ThoolooExpress For long downhill stretches coming down mountains, constantly using the brakes can cause them to overheat. You often see signs for semi trucks to downshift on these parts of the highway. Even if overheating is not a risk, it causes a lot of wear and premature maintenance of the brake pads.

[@DanielNebergall]

wow, definitely like that one!