Cars can sometimes seem to work almost through black magic. Sure, most of us know that engines largely work through the principles of “suck, squeeze, bang, blow” and missing one of those can cause a no start condition. Still, you can run into some weird engineering that just makes you go “huh.” What’s a piece of car engineering that makes you scratch your head?
Most of my cars are of the German variety, so I get to sit there and think about odd engineering decisions all of the time. Sadly, I rarely get an answer to what I’m confused about, but maybe I can expose you to the same things rattling around my head.
Let’s take a look at a 2008-2015 Smart Fortwo as an example.
Smart Fortwos with the standard transparent roof get a giant roof panel made out of polycarbonate from Webasto and Bayer Material Science. When the second-generation Fortwo made its European release in 2007, this roof was a huge deal. The previous Fortwo had a glass roof that was prone to shattering, but this new panel, spanning 1.2 square meters, was then the largest polycarbonate panel put into production.
The Makrolon AG2677-branded panel was pitched as better than glass. It didn’t shatter from rocks, weighed a fraction of glass, and maintained amazing clarity. The problem was that somehow, these panels began cracking from the inside out (a process known as crazing) often as early as just 6 months in. In theory, the panel should have been able to stand up to the abuse. They had UV coatings and data sheets suggested the panel wouldn’t start to break down until around 291 degrees.
Yet, these roofs began cracking and delaminating left and right only months in. Webasto tried reformulating the polycarbonate, which made the roofs last from a handful of months to a few years, but they still failed, anyway. It’s been so many years since I last saw a Smart 451 without a damaged roof that I’m sure the only undamaged 451 roofs out there are attached to low-mile garage queens. It’s such a common problem that I had no issue finding a Smart for sale with a failing roof:
That’s just one example of strange engineering. I could prattle on all day about how my Volkswagen Phaeton’s HVAC blower motor is dead and for some reason only Volkswagen can explain, I have to remove the windshield wipers to replace it.
Stephen Walter Gossin has his own example. Remember that expensive, yet somewhat rusty Toyota Camry that Thomas wrote about? Gossin noticed how the exhaust is pretty goofy:
Yep, there’s a U-turn in there to connect to a catalytic converter. Gossin says:
Is it just me, or would placing the exhaust flex pipe further aft negate the need for that U-turn off the cat-converter? So weird!
His other thoughts:
Possible logic #1: The only logic I can think of is having an equal length of exhaust tubing from the ends of each exhaust manifold to the flex pipe, but even that seems like a straaatch to add that extra metal/material/cost and weight.
Possible logic #2 (yes, I’m still a-head-scratchin’): Maybe moving the flex pipe aft creates too much fore exhaust system weight and thus, too much pressure on the flex pipe. Still unclear and confusing either way.
I don’t have the answer to that question, but maybe you do. Also, what other examples of weird engineering have you found out there? And to make this a little harder, the existence of the Tesla Cybertruck is too easy.
I’m a real shadetree wrencher so I’m not sure if this has precedent, but it threw me for a loop:
For the 9000, Saab decided to run a coolant line off the turbo’s, thread to through the crankcase breather hose and feed it into the throttle body.
I’m pretty sure it dead ends in there. Supposedly, this is to defrost a frozen throttle body. I thought it was a vacuum line, and ended up spraying hot coolant on myself in an Advanced Auto parking lot.
That’s without getting into the difficulty of pushing a bent metal pipe through a snugly fit rubber hose.
The GMT900 trucks from GM (’07-’13) all have two battery trays. The gas trucks get one battery installed, the diesels get two. One battery tray is all the way in the back corner of the engine bay, under some brackets that reinforce the fender. Replacement of that battery requires removal of that bracket. The other battery tray is right up front, behind the headlight and right next to the fuse box and alternator.
You’d think in the gas-engine application, GM would use the tray right next to the fuse box. Nope, GM uses the awkward to access back corner location. They then run multiple heavy gauge wires all over the engine and across the engine bay to reach the fuse box and alternator. They could have gone from ~10 feet of heavy gauge wire, to like two, by relocating the battery to the closer tray.
It’s a small thing, but just very odd.
As far as your Camry exhaust goes, it is indeed done to make both bank’s exhaust lengths equal. You will see a lot of vehicles do this – notably almost any Chrysler vehicle with the 3.6L V6 (wrangler included), and certain variations of the Ford Raptor. While it may help extract a little bit more power, I suspect it’s done to give the engine a more pleasing sound. V6s with unequal headers can tend to sound a bit crude and unrefined.
That GMT900 battery is extra perplexing because the GMT400 has both battery trays in front corners where you can easily reach them.
I’m shocked this hasn’t been mentioned so far in 126 comments, but it’s the water pump/thermostat assembly on the VW EA888 Gen 3. Folks, please Google “VW SSP 616,” open to page 33, and prepare your German engineering bingo cards:
1. It’s a giant chunk of plastic that looks like a deformed octopus.
2. It’s mounted on the back of the engine…
3. …Despite the fact that all of the other accessories and the timing chains are on the front of the engine, which means it has its own bespoke drive belt off of the left balance shaft.
4. It leaks every 70k miles.
5. You have to remove the intake manifold to access it.
6. But it’s still too hard to access the drive belt so nobody bothers to change that.
7. Instead of having a traditional thermostat, it has two “rotary slide valves” that actually look more like ball valves you’d buy at Lowe’s, which rotate under force of an electric motor to direct coolant flow.
8. It has seven different modes of operation.
9. It still needs a mechanical thermostat backup.
10. It has an integrated circuit board only 1 o-ring away from hot coolant.
11. It’s four or five hundred dollars for OEM parts and coolant.
Not being able to roll down the rear windows in a middle-class sedan befuddles me.
That was pure stinginess by GM in the 70s, stupid but not baffling.
one question i would want an explanation from an automotive engineer is if wider tire = more grip how come more track cars aren’t driving with 325 wide dumpys for tires.
I get that diminishing returns exist. and at some point you would be adding so much more weight that you would be reducing track times and also a particular vehicle can only accommodate so large of a tire.. But how does an engineer pick a tire size in the first place? seems like you can almost always go at least 5-10mm wider than factory leaving performance on the table…
Wheels have to somehow fit inside wheelwells and be able to turn and not rub on suspension or bodywork
You size the driven tyres for traction, and size the undriven ones for handling balance (unless it’s FWD in which case you make them the same).
Once you can hit the vehicle performance targets you stop fitting bigger tyres. Or you fit stickier tyres instead.
Wider tyres have higher rolling resistance and more aero drag, both bad for emissions, plus you’ve got to fit them in the arches, and on the front that starts eating in to the footwell. There is also a limit on how wide a front tyre can be without hitting stuff like dampers and suspension arms on full lock, going beyond this means moving the wheel outboard, which can do horrible things to steering.
There is often additional arch clearance for snow chains, and you’ll want 5-10mm clearance just to protect for manufacturing tolerances. So fitting wider tyres than stock is usually an option.
Finally, and I can’t stress this enough, grip is less fun than sliding around. Having a good time isn’t always the same as setting a good time. Not unless you’re actually racing.
Well, you started off with an incorrect assumption. Wider tire does not(necessarily) mean more grip. For a whole lot of reasons.
go on!
There’s a trade-off for unsprung weight, packaging (bigger tires need a wider body) and running costs. At some point you hit diminishing returns, so most cars run tires that are “wide enough” to avoid the downsides.
But before you even get to considering all that, there are series regulations. Almost every racing series has very strict regulations regarding tire size and compound, it’s either a fixed maximum size or a function of vehicle weight/drive type.0
I’ve got a V8 F150 that requires two oil drain catch pans, because the oil filter is right above a suspension cross member and when you unscrew it, it dumps onto the cross member and half of it drips forward and the other half aft. The span involved is a bit much for a single pan, so I have to use two.
I get that placing the oil filter somewhere else could be too problematic, but how hard would it have been to make is so the oil only went in one direction?
The Hemi rams (2009 – present) are similarly set up, but the drain plug is close enough to the cross member that only 1 pan is needed.
The third generation Ford Explorer V8 has a similar issue, though Ford was polite enough to put a little plastic piece on the cross member to try and funnel the dripping oil to one location.
The 1-2 punch of using nylon timing chain guides and then placing the timing chain on the back of the engine. It’s one thing to pull an engine to do preventative maintenance on a fancy car like a 911, but it seems a tad excessive for something like a late ’90s Ford Explorer.
You also just described a timing chain guide replacement job on an Audi-specifically the 4.2 liter FSI engine!LOL
Almost all newer (past 10-15 years) manual trans cars with hydraulic clutches have a ‘clutch delay valve’ somewhere in the hydraulic line from the clutch master to the slave cylinders. It is basically an obstruction with a tiny hole in it that introduces a delay between clutch pedal press and the clutch actually engaging/disengaging. All this prevents very fast gearshifts because the clutch in/out takes longer. It’s especially maddening in fun cars, which are supposed to be directed at enthusiasts..
The saving grace is most of them are not very difficult to remove, but still pointless & annoying.
While it is annoying, it does serve a purpose. One of the most difficult aspects of designing a vehicle with a manual transmission is how to manage shock loads from people dumping the clutch. A vehicle with a manual transmission option will need stronger driveshafts, differentials and axle shafts than if it were just offered in an automatic. That valve helps slow down the clutch application rate, reducing shock loads.
Is that why almost all newer MT cars have clutches that feel “gummy” to me? Good to know!
One of them has to be the awd Mercedes W124 where the axle passes through the elongated spring. So ridiculous.
https://www.reddit.com/r/Autos/comments/3pmhzu/til_about_the_w124_4matic_strange_front_suspension/
I’ve never seen that before. Just… wow.
Not that ridiculous when you remember that the 4Matic system was designed after the development of the rest of the car was completed.
Retrofit engineering is going to result in compromises like this.
Another fun one on that car is the design of the belt tensioner. It’s designed to be as complicated and easy break as possible.
For a while I was the exhaust designer at an OEM. There’s a couple of things going on here, one is equal secondary exhaust lengths, the other is that flexi joints don’t flex. Terribly misleading name.
They are not supposed to bend, they are supposed to concertina in and out. Bend them and they fail. Bend them and the supplier voids the warranty.
So the acceptable position of the flexi depends on the position of the engine mounts and how they control engine rotation. Put the flexi in the right place and it just sees axial movement, put it further forward or backwards, or change the angle, and it gets bend movement and you’re having to balance durability and warranty without the supplier covering the cost. Failure mode of a flexi is a hole, a hole before the rearmost cat in a system is an emissions failure, which is bad. What’s worse is that the hole is letting out gas at a temperature height than the flashpoint of fuel, oil and even coolant, which is also very bad in a more immediate way.
So you have a very limited range of positions for a flexi, and if you want equal secondaries (and you really do) then you have to stick the extra length in as a U bend, or use a load of package space not having a vertical cat (don’t get me started) It’s horrible, but less horrible than the alternatives.
If you want a bendy exhaust decoupler you use one of those spring-loaded spherical joints. They have no axial give, which has its own issues.
I might skip the rest of the comments.
You probably just saved me from using one of these wrong in a project car one day, thanks.
I used to calibrate engines for emissions compliance and my $0.02 is that those pipes are the way they are to get the catalyst close enough to the engine to warm up before blowing whatever standard applies. They’ve been marching steadily closer for decades. I recently saw one integrated into a turbo housing.
It’s not to get the cats closer. The primary cats on that engine are already in the manifold, a few inches away from the cylinder head and upstream of the U-bend and flexi. You can see the outlet cone of the cat on the rear bank just before the start of the U-bend. There is a secondary cat further down the exhaust.
Nylon camshaft sprocket on my K5’s small block 305. Just glad there was no interference.
Mercedes of the 90’s with degradable wiring insulation. That was a stupid idea. They also ended up using soy based wire coating into the aughts. when it gets warm, it smells like peanuts, and the squirrels and other rodentia seem to not be able to resist munching on it.
The Honda Cvcc engines were bewildering yet interesting in form for the time.
V10 Touareg o2 sensors replacement step one remove engine and transmission
I laugh every time I’m under the hood of my ’15 LR4, which famously has a V6 made out of a V8. Only, Jaguar/Land Rover didn’t chop off the space left by the missing two cylinders. They just didn’t provide bores for those last two, but kept the same outer V8 casting. So, it’s a V8 with two missing bores, shorter heads, and some balancing shafts to make the 90-degree angle work with 6 cylinders. Oh, and a supercharger, because the 3.0 S/C V6 replaced the prior 5.0 N/A V8. It was a cheap way to do it, for sure. At least it has a nice exhaust note.
I just had to look that engine up. Insane!
I often wonder how the factory suspends the throout bearing in mid air while they assemble the car around it.
A car I will not name required you to remove the radiator, remove the hood, remove the oilpan, remove the head (dohc, so there was a timing chain and other non trivial stuff to deal with, remove the driveshaft, undo all the mounts. Remove the interior as best you can keeping mind that it is leather and is stitched in place around the shifter console and is essentially one big piece held in by the metal trim. Remove the shifter and transmission hump. Slide the engine and transmission forward a few inches while rotating it about 80 degrees. Unbolt transmission from the bell housing and remove through the interior you drained it before right? Now you have room to separate the engine and the clutch and can proceed normally.
As the English say assembly is this process in reverse.
Repeat in 8 months when the crummy Italian throw out bearing fails.
My wifes car was a 199 volvo V70XC for a while. Real pain to keep going. One item that comes to mind is the external fuel pump. On the FWD models, you just unbolt it from below like normal, but on the AWD model, the procedure involves removing the entire rear drivetrain, rear suspension subframe and fuel tank. Or just cutting a hole in the floor from the inside under the rear seat and doing from above. Guess which method I selected?
Mine had a hole under the seat made by a lumberjack with a hate got Swedish cars
The easy way to change the Porsche 914/6 alternator belt is to remove the passenger seat / bulkhead cover – it is all one piece , and saw a hole in the firewall.
Most 914/6s you see have a little removable panel there, but it’s not from the factory.
I asked what the other was to do is was and it is an engine out procedure.
I did one the same way. The car was priced at $400 because the previous owner was given an estimate of $2000 for replacing the fuel pump. Other than that it was in nice shape. I then sold it to my neighbor’s daughter, who enjoyed it for several trouble-free years.
That is an infamously terrible design, and a famously clever solution.
I’m going to nominate fucking plastic clips to hold just about everything together. All manufacturers take an immediate walk of shame. Now!
Buy replacement clips before you start the job, then just break them all taking it to bits. Low stress and no delays before reassembly.
I finally learnt this on my 5th BMW.
I’m not sure if there will ever be a 6th BMW.
BMW’s use of crappy plastic cooling system parts when this has been well known as the biggest reliability issue in a broad variety of their engines for DECADES. This comes in well ahead of their valve cover, oil filter housing, and oil pan gasket issues. (Toyota can make gaskets that live forever, why not BMW?) Those gaskets pretty much just leak, though, they don’t cause catastrophic engine problems the way the cooling system problems can.
95% of everything that would fail on my wife’s E46 BMW was related to failed plastic ☹️. She loved that car, but I was so happy the day we sold it.
I had B5 and B6 Audi S4s and I still get PTSD from the thought of pulling off the ENTIRE FRONT END OF THE CAR to get to the timing belt (B5) or chain guides (B6).
That’s what happens when you put the engine longitudinally in the nose of the car. Still, VW Group “service position” isn’t all that complicated. I did it in 30 minutes on my 2013 A8 L–including removing the radiator–and that was one of the more-complicated VW Group models to use that layout.
You’ll remember the Audis fondly when you have to do the same on a Subaru
Changing the diff lubricant in an old Lotus Elan requires 1) taking the body off of the chassis (at least part of the way), or 2) cutting a hole in the front wall of the spare tire well, to get at the filler plug.
B6 generation Audi A4/S4 (and probably other audis of similar vintage)
Automatic headlights were an option. If you didn’t get the option, they still had a sensor that would detect it getting dark and dim the dashboard to signal you to turn your lights on.
Let that sink in for a minute. Audi is basically like “well either way, we’re going to install hardware capable of detecting the level of light and changing the status of some lights on the car. If you pay us, we’ll have it turn on the headlights, if you don’t pay us, we’ll have it turn down a light to signal you to manually turn on the headlights”
Toyota too. I just bought a newer Sienna with all kinds of automatic features – lane keep assist, seatbelt minders, brake hold, crash avoidance, radar cruise control…and when it starts to get dark, it chimes at me to turn on the lights. Because apparently it can’t do that itself.
I’m sure it can do that, but you probably had the lights manually set to “off.” My 2004 and 2006 Jaguar XJs had similar functionality. if the headlights weren’t set to “auto”–which usually happened after they’d gone to the mechanic, which was quite often–and it got dark, you’d get a message on the IP that said “Lights are off”
Yup, there is an “auto” setting, but if the lights are set to “off” the car will chime and display a warning that can only be dismissed by turning on the lights. If the car is so adamant that the lights should be on, why not just turn them on instead of nagging me? Why have an “off” setting at all?
I’m strict about having an off setting for the highlights. I hate the idea of walking away from vehicles with the headlights still on and “trusting” that they’ll turn off, especially if I quickly enter a building or turn a corner before witnessing that.
I haven’t owned a vehicle with an auto setting yet, but it’s something that sits in my head when I’m driving someone else’s car with the feature.
Also, I assume there are situations that warrant turning off all exterior lights (beyond, say, driving to a scientific observatory at night, where there are often “headlights off” warning signs).
Don’t worry about it. It’s never happened to me. Now I’ve had brake light switches break and the brake lights get stuck on, do you worry about that?
Well, the cars with automatic headlights still had a switch with an extra position, so they saved some money by having the automatic option. Also, consider that European automakers were fairly late to the game with automatic headlights, versus American and Asian ones. The early L322 Range Rover, which was chock-full of BMW electronics and was certainly not a cheap car, did not get them standard (or perhaps at all).
But I’m with you; Audi needn’t have bothered with the sensor if they weren’t just going to go ahead and make the automatic headlights standard.
How GM couldn’t figure out a way to route the engine oil dipstick on the current 1500 trucks with the 2.7 so that you can reach it without a ladder.
My truck is stock, regular height and I’m 5’8″. I have a sloped driveway, so there I am, in the street with a stepladder or milk crate…
And a general one:
Why do so many direct injection engines still have issues with carbon in the intakes? It’s been 20+ years they’ve been around.
At least you have a dipstick. My LR4 doesn’t have one.
As for the carbon thing, I wish more automakers would do dual (port and direct) injection system’s like Toyota’s D-4S, which has been around since 2006, or what Ford does on the Coyote.
because the gasoline actually used to clean the carbon off the valves, now it is directly injected into the cylinder. Some newer direct injection engines actually have a small indirect injection nozzle now to help keep the valves clean longer.
Engine timing chain guides that made of plastic, like on the Nissan 240sx KA24. Let’s take a material that isn’t meant for high temperatures and put it inside the engine. And while we’re at it, let’s make it a single point of failure that detonates the engine if (when) it fails.
Several BMW engines would also like to be mentioned here.
As would Mercedes-Benz engines
Wait until you find out about literally most engines(plastic timing chain guides are extremely common and have been around since the 70s)
Some plastics are better than others.
Been working on cars intermittently for 35 years. I had a stocked tool box, jack and stands in college and did a lot of oil changes/tune ups/brakes/shocks/batteries/sway bar ends/alternators/starters/etc…on a vast number of makes and models. I will say the Japanese automakers usually kept an eye in design towards future servicing that the domestics did not.
1996 4.6L V8 Thunderbird. The oil filter only came out ONE way and you could not do it without dumping the contents on you/ground etc… Bonus points if hot.
My ’02 Mustang agrees with your T-bird there. At this point, I have a fairly elaborate scheme that involves multiple layers of different types of plastic bags, but I’ve yet to complete an oil change w/o spilling.
88 F-250 with a 351, 05 Navigator with a 32V Triton. Both with oil filters you had to dump over, and then squeeze over.through the front crossmenber.
the early v6 escapes placed it just above the exhaust Y pipe, you had no way to get it out without dousing the exhaust in flammable oil.