OPEN diff vs LSD vs WELDED diff - VISUALLY + In depth EXPLAINED - Version 2

so today we're talking about this very heavy but very beautiful thing right here and this is a limited slip differential in today's video we'll be comparing this to open and welded differentials to see how they influence the handling and traction characteristics of your car by the way this embodiment of mechanical genius was supplied to me by midship garage who is sponsoring this and other videos in this series which will be covering limited slip differentials in great detail now midship garage is a grassroots business that goes above and beyond when it comes to supplying high quality parts for all generations of the toyota mr2 the toyota silica and other car platforms they also do actual r d and create completely unique and bespoke parts for these pretty ancient car platforms stuff that you really can't find anywhere else and they're absolute wizards when it comes to sourcing hard to find parts on top of that they're a business led by actual car enthusiasts with actual knowledge on cars and how to modify them as an mr2 owner and enthusiast of course i have purchased stuff from midship garage and i have to say that the experience was always more than positive today i'm grateful that i have the opportunity to work with midship garage through my videos and i hope that through my videos i can draw some attention to them because in all honesty this business is a blessing for the mr2 and celica car communities of course links to midship garage and this differential and more stuff are down below now in today's video we won't be explaining how different types of differentials work we'll cover that in future videos instead we'll see how different types of differentials affect your handling and what they do for your traction in different scenarios so we're talking about the things that matter to you while you're driving rather than the things that might interest you from an engineering perspective again the engineering perspective will be covered in future videos now i really wanted to make this video but to be honest i really struggled on how to make it i couldn't find a good visual aid that will demonstrate in a simple and easy to understand matter how different differentials affect handling i considered hiring somebody to do complicated 3d animations i even considered making a model vehicle with exchangeable actual differentials and i had a bunch of other ideas but all of them were either too complicated or simply impossible to implement that is until i realized that the solution was right in front of my nose well not really in front of my nose but actually in a box in my basement yes legos something that i really used to enjoy playing with and something that i really missed playing with now here's our open differential and here's our limited slip differential and finally our welded differential we're going to start of course with the open differential this is something that you're going to find in the vast majority of cars on the road today especially in normal or non-performance cars the open differential has one key purpose and that is to allow you to take a corner in other words the open differential allows two wheels on the same axle to rotate at different speeds and to see how this works we're going to install our open differential into a simple little lego car that i made and here it is as you can see it's battery powered and driven by an electric motor and it has a very simple steering mechanism now we're going to install our open differential and then we're going to drive our little car around in a circle if you observe the two lines taken by the two driven rear wheels you will notice that the inner wheel is covering a shorter distance than the outer wheel because it's covering a shorter distance it obviously rotates slower than the outer wheel in other words it needs to make less rotations than the outer wheel over the same period of time and the differential makes this possible hence its name different show it enables different speeds of the two wheels connected to it so what would happen if we didn't have a differential well we can easily demonstrate that by replacing our open differential with our welded differential we simulate the welding by simply joining the two axles together because the two wheels are now physically joined together they are unable to rotate at different speeds because of this one of the wheels has to make up for the difference in speed by sliding skipping hopping or whatever else you can observe the same behavior on a real car with a welded differential if you take such a car and try to negotiate a parking lot or any tight turns with it of course this isn't really a desirable scenario as it not only wears out your tires much faster but it puts a lot of strain on your axles and other dry mind components on top of this it can make a lot of noise and draw unwanted attention obviously none of these issues will be present with a normal open differential but as you can see in the case of our lego model car there's no skipping hopping or sliding or anything because the tires have too much grip instead the next weakest link are the gears and you can hear them grinding and skipping teeth and if you drive the car long enough the stresses are actually so great that they pull one of the axles out of the differential casing so how does an lsd or a limited slip differential compare to this and why would you want one well if you're driving a car normally that is if you're driving on a daily basis from a to b and you're doing zero racing zero spirited driving zero driving in bad weather especially in snow then there's zero chances that you will notice the benefits of a limited slop differential to better understand the limited slip differential we have to go back to the open differential and to understand the drawbacks of the open differential we're going to observe it in a scenario where a open differential equipped car has one wheel on a low friction surface such as ice for example and the other wheel on a good friction surface such as asphalt for example and we're going to imagine that our engine for the sake of simplicity can generate a maximum of 100 newton meters of torque now the engine sends this torque to through the drivetrain and the goal of the drivetrain is to convert torque from the engine to torque at the wheels now in reality the gearing of the transmission is going to significantly multiply torque from the engine by the time it gets to the wheels but for the sake of simplicity we're going to ignore this and we're going to observe torque at the wheels in the scale of engine torque so what we can observe in this scenario is that it obviously takes less torque to break traction on the wheel on ice because it's on a low friction surface so for example let's say that it takes 15 meters to break the traction on the wheel on ice when this happens the open differential is going to prevent the other wheel the wheel that's on a good traction surface from receiving any more than 15 newton meters of torque so in other words when wheel slip occurs in a car equipped with an open differential it limits the amount of torque that the other wheel can receive the good traction wheel cannot receive any more torque than it takes to break the traction on the wheel that's on a low friction surface so our engine can generate a maximum of 100 meters of torque but as you can see here we're just putting 30 newton meters of torque to the ground which means that the open differential in this scenario wastes the torque potential of the engine and if the friction on the low friction wheel is so low that the amount of torque transferred to the other wheel is very low too and the overall torque is insufficient to overcome the inertia of the vehicle then you will remain stuck we can also demonstrate the same thing using our lego car we're going to simulate the whole traction on one driven wheel by removing a tire so now we can pretend this one is on ice and the other one is on asphalt as you can see our old friction wheel does indeed slip but our vehicle eventually takes off and doesn't remain stuck we aren't stuck because the amount of torque needed to break traction on our tireless wheel is high enough to overcome the inertia of our vehicle and get it moving this lego motor can generate 0.7 meters of torque so it's assumed that it takes only 0.3 newton meters of torque to break traction uh on the wheel without a tire this means that the outer wheel the one with the tire is also only getting 0.3 newton meters and all this means that overall just around half of the total torque potential of the engine is being transferred to the ground however in our case this is enough to overcome the inertia of the vehicle and get it moving but as you can see it isn't enough to move it very fast now let's replace the open differential with our limited slip differential as you can see with the limited sub differential there is no real slipping the vehicle takes off immediately and it travels at much higher speed the answer to how the limited differential can do this is in the name itself limited slip differential it limits wheel slip in contrast to this you could call the open differential in unlimited sub differential because it has no way of limiting wheel slip our particular differential is a torque biasing differential which means that it limits slip by biasing torque to the wheel which has more traction so in the same scenario with one wheel on ice the limited zip differential will not allow the slipping wheel to waste the torque potential of the engine it will not allow the slipping wheel to prevent the wheel retraction from receiving more torque so if it takes 15 meters to break traction on the ice wheel the other wheel will not be limited to 15 newton meters as well instead the limited slip differential will bias torque to that wheel and that wheel will receive more torque a torque biasing differential can have a biasing ratio as high as 4 to 1. this means that if it takes 15 newton meters to break traction on the ice wheel the lsd can bias as much as 16 newton meters to the wheel on asphalt which is more than enough to get the vehicle moving quickly and without any wheel slipping so what about the welded differential as you can see it too has zero issues taking off and there's zero wheel slip occurring this is because the welder differential effectively turns the rear axle into a solid common axle and the entire rear axle now behaves as a single unit which means that the low friction on one wheel becomes totally irrelevant and now 100 of the engine's torque is available to both wheels all of the time now don't let this confuse you because this doesn't mean that the engine's torque has now been magically doubled perhaps a less confusing perspective is to observe the rear axle as a whole as a single unit and see that all the torque is available to the entire axle all the time although the differential can achieve such a torque output because in this scenario it doesn't just limit wheel slip it completely prevents it from ever occurring the two wheels are now one and thus neater can rotate faster or slower than the other this means that the wheel with traction will determine the speed of rotation for both wheels the result is that the welder differential is best at putting down the most torque on the ground in this scenario however as soon as you start taking corners especially on a good friction surface its many drawbacks quickly become very apparent so this explains taking off in a straight line from a standstill in poor traction situations but what about aggressive cornering well to better understand that we're going to analyze how different differentials behave through a corner in three different vehicle setups front engine front wheel drive front engine rear wheel drive and mid-engined rear wheel drive [Applause] now first let's observe a front engine front-wheel drive car to recorder let's imagine that we just stopped braking and that we applied full throttle to try to get out of the corner as fast as possible to understand what's happening in this situation we first must understand the weight transfer occurring in the car at this time now when it comes to weight transfer in cars it always occurs at the opposite direction of vehicle travel so that means when you're accelerating you're going forward that means that weight transfer occurs in the opposite direction so weight is being transferred away from the front of the vehicle towards the rear end you can easily observe this in real cars when they're accelerating hard the nose comes up because weight is being transferred away from the front towards the rear weight is being transferred at the opposite direction of vehicle travel what's also happening happening during a corner is that weight is being transferred to the half of the car that's on the outer side the outer edge of the quarter because we're taking a right corner weight is being transferred towards the left side of the vehicle again at the opposite direction of travel now weight transfer is extremely important for vehicle cornering because it determines the amount of weight above each of the wheels now the amount of weight above the wheels plays a key role in traction because the more weight there is above the wheel the more downward force there is pressing the wheel against the road and the more downward force there is pressing the wheel against the road the more traction that wheel is going to have so in this scenario it's pretty obvious that this wheel the inside wheel has the least amount of traction because weight is moving away from it this means that this wheel is the easiest one to slip and if it slips or rather when it slips it's going to limit the amount of torque available to the outside wheel as well this means that with front wheel drive it's pretty easy to realize the drawbacks of an open differential because weight is moving away from the front driven wheels when we're accelerating out of a corner the result is usually understeer because the total torque planted to the ground can be insufficient to overcome the inertia of the vehicle which just wants to keep pushing the vehicle forward in a straight line a limited sub differential can greatly remedy this situation because it can bias torque to the outside wheel which means that overall more torque can be planted to the ground and it can overcome the inertia of the vehicle and dramatically reduce understeer so what about a welded differential in a front wheel drive car well it guarantees that the inside wheel is going to slip because it has to accommodate the rotational speed of the outside wheel but you're likely going to slip the inside wheel anyway so this doesn't really bother you that much in theory the welder differential should ensure that more torque is pointed to the ground which should in theory improve cornering in practice results vary greatly with an over with a welded differential in front wheel drive car and are highly dependent on the vehicle setup the type of road surface and driver skill in many cases being successful with a front wheel drive car with a volta differential is going to require significant adaptations of your driving technique but again it's best reserved for a budget racer because a well differential front wheel drive car is going to have dramatically increased tire wear as well as wear and tear of various components in your drivetrain so what about front engine rear wheel drive in the same scenario well in this scenario because the driven wheels are actually at the back of the car the weight transfer towards the back of the car when accelerating actually benefits us because we're transferring weight above the rear wheels we're increasing the down force on the rear wheels which means that we're increasing their traction and this is why rear wheel drive overall has a greater cornering potential than front wheel drive so does this mean there's no benefit to an lsd on a rear wheel drive vehicle actually no the only scenario where there's no benefits is when your engine is so underpowered that it doesn't have enough torque to break traction on the inner wheel in reality there really are no rear wheel drive platforms with such low torque engines that they can't break traction on the inner wheel even the most underpowered popular rear wheel drive platform such as the mazda mx-5 slash miata or toyota a86 still have enough torque to break traction on the inner wheel when they're driven aggressively enough so what about the welded differential in the same scenario front engine rear wheel drive well the welder differential as we know guarantees that one wheel will break traction that one wheel will slip because the two wheels are physically joined together they cannot have different speeds of rotation in this case the inside wheel is always going to slip through the corner with a welded differential because it has to accommodate the number of rotations of the outside wheel what does this mean well it actually means that the same car front engine rear wheel drive with an open differential will out corner an identical car with a welded differential as long as the engine doesn't have enough torque to break traction on the inner wheel with an open differential it means that it will maintain more to a more grip more traction at the rear and the open differential will out corner it will exit the corner better and faster than a welded differential and although it will out corner it the open differential won't be able to out drift the welder differential because we have less overall grip in the rear with a welded differential we're guaranteed to slip one wheel we're guaranteed to break traction as soon as we take the corner it's easier to initiate a drift with a welded differential rear wheel drive vehicle as an added bonus we also still have substantial torque available to the outside wheel which means that we have still substantial torque available to maintain the desired angle of oversteer which means that welding a differential on a rear wheel drive car is a good idea for a very budget oriented drift car that you really don't care much about because we still have the same downsides of a welded differential which is reduced usability increased tire wear and increased stresses and shocks to your drivetrain so what about the mid-engine rear wheel drive setup we have the same driven wheels the one at the back of the car which means we're again benefiting from the weight transfer towards the back of the car but this time we also have the engine and the transmission the single greatest concentration of weight in the car also towards the back of the car and it's there to even further aid the weight transfer it's there to generate even more downward force on the back wheels which means we're getting even more grip during corner exit this means that in theory at least the mid engine setup has the greatest cornering potential of all of our three discussed setups so does this mean that the lsd is completely useless in a mid-engined car no it just means that a mid-engined car needs more torque to break traction on the inner wheel than a front-engined rear-wheel drive car now my car which is a toyota mr2 mark 1 in its factory stock 4 made 130 newton meters of torque this is okay for the 80s but it's a joke by today's standards and this is why this car which is lightweight uh you really have to drive it like a maniac to an extremely tight corner to get the inner wheel to break traction which means you don't really realize the downsides of the open differential which is why this car came from the factory fitted with an open differential but then came the second generation of the toyota mr2 and it was blessed with a turbocharged engine which in its highest powered form made around 300 newton meters of torque more than twice that of generation one and this was more than enough to break traction on the inner wheel which is why toyota offered the second generation with a optional limited slip differential by the way you can still get these brand new oem viscous type limited sub differentials through midship garage along with a bunch of other awesome parts links are down below now i'm following the same logic i'm building a new engine for my toyota mr2 mark 1 and my goal is to try and aim for around 300 horsepower around 50 more than the highest powered version of the engine in the mark ii which means i do have more than enough torque to break traction on the inner wheel which is why i'm fitting a limited slip differential i needed to maintain the good handling characteristics of my car because i'm increasing the torque coming from the engine which will now be more than enough to break the traction on the inner wheel which will realize all the downsides of an open differential but why don't i just weld the differential instead well i really want to be able to park my car normally but other than that welding the differential on a mid-engined car isn't really a sensible move you're reducing the grip in the rear because you're forcing one of the wheels to slip and the whole point of a mid engine platform is to have really good grip during corner exit but you're killing that with a welded differential which means you're reducing the cornering potential of your car so you're trying to make it into a drift car but that's also a bit of a waste because naturally the mid engine platform isn't inclined to drifting as a front engine rear wheel drive platform because it has more weight in the back which means it's not just harder to initiate the grip it's also harder to maintain it because of a different weight distribution so overall welding differential on a mid-engined car not pretty sensible which is why not many people do it at all so limited slip differentials are the clear winner here they outperform open differentials by a thick margin but they also give you the same usability because they allow different wheels on the same axle to turn at different speeds unlike the welter differential which basically kills usability but there's got to be a downside here right they cannot be that good well there is a downside and that is that limits of differentials have increased complexity and therefore obviously increased cost also some limits of differentials need regular maintenance which isn't the case with open differentials which usually last the lifetime of the car but this is why i got this one the quave atb automatic torque biasing and this one is maintenance free zero maintenance it's also pretty much indestructible because it's gear based you put in the car and you forget it but more details about this one and other types of differentials in future videos and there you have it that's pretty much it when it comes to the comparison of handling characteristics of open limited slip and welded differentials i hope you enjoyed this video found it informative and i hope it helps you make a better more educated decision for the differential in your next build as always thanks a lot for watching and i'll be seeing you soon with more fun and useful stuff on the d4a channel

Channel: driving 4 answers

Views: 27,516

Rating: 4.971581 out of 5

Keywords: LSD, limited slip differential, lsd, differential, open differential vs limited, open differential vs lsd, welded differential, welded differential daily driving, open diff vs lsd vs welded diff, lsd vs welded diff, limited slip differential vs welded, quaife atb, ff vs fr vs mr, limited slip differetnial fwd, limited slip differential rwd, limited slip differential benefits, limited slip differential in snow, welded diff pros and cons, welded diff daily, lsd problems

Id: 1B1FNs5bgrE

Length: 22min 56sec (1376 seconds)

Published: Fri Apr 09 2021