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  • Plastic engine parts in cars

    Posted on MrJimPhelps Comment on the AskWoody Lounge

    Home Forums Outside the box Rants Plastic engine parts in cars

    This topic contains 41 replies, has 11 voices, and was last updated by  Sessh 1 month, 2 weeks ago.

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    • #1954554 Reply

      MrJimPhelps
      AskWoody_MVP

      More and more car engine parts are made of plastic these days:

      Under the Hood

      This is supposedly a good thing; in my opinion, it’s only a good thing for the manufacturer, who wants to save money on the cost of building a car, even if it means that the customer gets junk. Of course, as these plastic parts break, the customer will have to replace the parts, which puts even more money into the pockets of the car companies.

      I’m not buying it. I long for the days when cars were almost all metal. Not only did they last a lot longer, but if you got in an accident, you would fare a lot better.

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    • #1954668 Reply

      OscarCP
      AskWoody Plus

      MrJohnPhelps: “Not only did they last a lot longer, but if you got in an accident, you would fare a lot better.”

      Quite so! Years ago, I was driving a compact Chevy Prizm with an-all steel body when, from the lane on my right, the driver of a big pick-up truck suddenly tried to move across my lane to make a turn at an intersection. Unfortunately at that moment, the only way to do that was by going through my car, that just happened to be inconveniently on the way. As a result, there was a violent crash that badly damaged the front passenger’s door of my car (as I later found out) and sent it into a wild spin, first crossing to the incoming lane and then back out of it to come to a stop near the ditch of what was originally my side of the road. When the movement stopped and I looked back, I could see the road strewn with pieces of car. “Oh, no!” I thought, “The other driver has demolished my car!”

      But that was not what has happened: the bits and pieces on the road were all from the body of the larger vehicle that had a lot of plastic in it. The driver was a teenage boy who kept repeating: “My Dad is going to be sooo mad when he finds out!”

      Windows 7 Professional, SP1, x64 Group B & macOS + Linux (Mint) => Win7 Group W + Mac&Lx

    • #1954735 Reply

      Microfix
      Da Boss

      Aerodynamic cooling IS good for an engine/ air intake and brakes hence the ABS shielding and ducts.
      Then there is also containment of oils and fluids should anything leak within the ABS shielding. Airbags reduce accident fatalities so, more modern cars win hands down as opposed to old dodgem cars.
      The downside is, removing all these HT/ABS parts to access working parts at a cost to the customer at a mechanics hourly rate.
      It’s the world we live in now.

      ********** Win7 x64/x86 | Win8.1 x64 | Linux Hybrids x64 **********

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    • #1954805 Reply

      MrJimPhelps
      AskWoody_MVP

      I had a 66 Dodge Dart a while back. Someone hit me broadside just in front of the driver’s door – they were doing around 55 MPH. They bent my front fender, but that was about it. I pulled the fender out from the tire by hand, and I was on my way!

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      • #1954836 Reply

        anonymous

        MrPhelps, good one! Years ago I was told by one of my relatives that he had his ’67 Cadillac at the muffler shop in his town. It was parked outside in the parking lot waiting. He went to lunch. When he got back there was police and a wrecker with a ruined (totaled??) car on the bed of the wrecker. He went over to the shop owner and was told, “your car was involved in an accident”. He walked around the car SEVERAL times and could not see anything. The shop owner pointed him to the back corner bumper tail-light and he said there was a slight scuff on the bumper and a little crack in the red lens! Remember the other car was on a wrecker not drive able being hauled away. Now that … is funny. LOL

    • #1954831 Reply

      anonymous

      Hi Mr.Phelps and Microfix. We have conversed in the past #1919075 & #1874211. Hello Oscar, nice to see you too. I love these posts with you guys.

      Mr.Phelps I agree. The manufacturers are trying to cut weight and costs but costs is the bottom line. I remember when as a child, cars had their own personality. A Chevrolet could be spotted just by the headlights, for the same. Now-a-days I have to look at the badge to see what brand car it is. Smart manufacturers make a car that stands out like the Mustang or Charger/Challenger. But whatever.

      The problem with plastic is even though mold-able and cheap to make, it won’t last. The plasticizes within will eventually evaporate out and heat/UV takes its toll then plastic components get brittle and crack or downright break. As Microfix said “it is the world we live in now” and he is right, but that does NOT mean that I like it. I prefer metals as opposed to plastic for many automotive uses.

      I had a friend that was getting a lean condition in his ’97 T-Bird. The mechanic said the plastic intake manifolds crack and leak (this appeared to be common) so he had the manifold replaced (based on historical precedence of failures). The thing that makes me sad for him was after replacement it still had the lean error appear occasionally. I believe it was the PVC hose cracked and leaking after all. Ohhh, that was bad. The point is, with the usual cast iron or aluminum manifolds this would not had been the case. Investigations would had continued for the culprit until the HOSE was found leaking. Yes, Yes you are right, they should had looked at the hoses first. They could had also used the spray carb cleaner on the suspect places or propane hose on the suspect areas looking for an idle increase.

      I am not a fan of plastic for everything. Some items needs to remain some form of metal. I see NOTHING wrong with an aluminum intake manifold if one wanted less weight than cast iron. But plastic????

      Thank you guys!

      • #1955542 Reply

        Ascaris
        AskWoody_MVP

        I see NOTHING wrong with an aluminum intake manifold if one wanted less weight than cast iron. But plastic????

        I can think of a reason why a plastic manifold would be desirable.  A plastic manifold should have a lot less heat soak, which could be a positive thing for performance (reducing intake air charge temperature).

        Most people don’t even know what an intake manifold is.  The cheaper the car manufacturer can get the thing out the door and past the warranty period, the more money they make.  A cast iron manifold would add weight, and an aluminum one would add cost, for an item that would not be much of a selling point even if it were metal.  It would add more cost to the car than it would perceived value, as long as the things don’t fail so often that they give that model of car a bad reputation.

        I don’t have any categorical opposition to a plastic intake manifold if it can survive the test of time like a metal one.  That’s a big IF, and there does seem to be a correlation between things being poorly made and plastic construction in general, but I don’t have any actual facts regarding the relative longevity of plastic to metal.  An intake manifold is generally a part that should never fail in regular use, and it’s not hard to imagine a plastic manifold becoming brittle or shrinking and cracking over time, as so many other plastic parts do… but “guilt by association” isn’t really a viable method of evaluating resins used for underhood parts!

        The newest car I have ever owned is as old as Oscar’s, and its manifold (both parts) is aluminum, fwiw.  My thoughts on keeping cars are a lot like my thoughts on keeping computers and other household electronics… I buy it to be a more or less permanent fixture in my life from that point forward.  I don’t buy it with the intent of replacing it someday.  I may have to do that eventually, but it’s not an expected part of the plan.  I expect the thing to work!

        My mom still has the microwave oven I used to warm up Hot Pockets when I was in high school in the mid ’80s.  Still works just fine!  It’s a Panasonic, and so is my much newer microwave now.  I’ve had it for 8 or 9 years, and it stopped working about a month ago.  I watched some videos about troubleshooting it, opened it up, and soon found that one of the door-closed microswitches was damaged (supposed to be NC, but was always open.  It was heat damaged, indicating possible corrosion across the contacts for some time, or some other reason for excessive resistance).

        I ordered a new Omron switch from a seller on Amazon that had no feedback indicating selling used or counterfeit parts (always a bit of a gamble), and after they sent me the right part (first time was a part whose only semblance to what I ordered was that it was a microswitch… completely wrong in size, voltage rating, and everything else), I put it in and the thing works nicely once more.  Not quite up to the standard of the 35 year old model my mom has that never needed any parts, but at least it’s working.  I’d rather pay eight dollars for a switch (shipping included) than buy a new one!  Most people would have just bought a new one, I think, and it was such a cheap and easy repair.

         

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        • #1962717 Reply

          anonymous

          I ordered a new Omron switch from a seller on Amazon that had no feedback indicating selling used or counterfeit parts

          Advice for everybody: Buying parts from Amazon or eBay is neat, but you can decrease the possibility of getting counterfeit parts by going to Digi-Key, Mouser, Allied Electronics, Sager etc. You may not find the exact part but they may be able to advise you about replacements.

      • #1962754 Reply

        wavy
        AskWoody Plus

        Well some plastics are better than others. I believe rotors on distributors are made of Bakelite and seem to hold up reasonably well.
        AS regards to why plastics are used in place of metal, it is the weight, the MPG requirements for new cars need to be met and loosing weight is one strategy.

        🍻

        Just because you don't know where you are going doesn't mean any road will get you there.
        • #1962768 Reply

          OscarCP
          AskWoody Plus

          Wavy: I remember distributor rotors; I remember Bakelite. Knowledge sometimes dates us, does it not?

          The good thing about distributor rotors was that one could remove them easily, put the rotor of one’s car in one pocket and walk away from the car with considerably certainty that it was going to be still there when one came back.

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    • #1954840 Reply

      Microfix
      Da Boss

      Well one could go for carbon fiber in place of HT/ABS plastic..dreams on

      ********** Win7 x64/x86 | Win8.1 x64 | Linux Hybrids x64 **********

    • #1955510 Reply

      OscarCP
      AskWoody Plus

      Back to my all-steel bodied car: it was then and still is a Chevy Geo Prizm ’90 (*), by now close to 30 years old and still going strong, thanks to all the tender love and care it gets once a year from the very good mechanic that has been looking after it for well over ten years — after the previous great mechanic that did that mysteriously disappeared (for reasons totally unrelated to my car, I’m sure).

      I am keeping this car as an experiment to find out for how long one can drive the same car.

      (*) A Toyota Corolla assembled by GM back when; in other words, a Cryptotoyota.

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    • #1957063 Reply

      Paul T
      AskWoody MVP

      but if you got in an accident, you would fare a lot better.

      Just not true.
      Modern cars are designed to absorb impacts so that your body doesn’t have to. It means they cost more to repair, but what cost your health?

      cheers, Paul

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      • #1958044 Reply

        OscarCP
        AskWoody Plus

        Paul T: Quite so: “crumple” bodies are designed to fail in a calculated way, while absorbing the energy of the impact. Perhaps “you fare a lot better” referred not to the driver and passengers, but to the car, instead? As I have already mentioned, my all-steel body car has survived fairly well some low-speed collisions that did no harm to me, but save me the time and expense of large repairs, or the need (and the usual hassle) of buying a new car.

        While a “crumple” body and air bags save lives, sometimes those can be diminished lives, because of the long-term effects of possible serious injuries that, even with those protections in place, may be sustained by those traveling in the damaged vehicle. Better than the alternative, no doubt, but still nothing like being in the pink of health.

        There are those that think the engineering advances in car safety available in modern vehicles make them free to drive and text, have a fight with a girlfriend over a cell phone, and pay little attention to what other drivers are doing. Practicing defensive driving, signalling turns and changes of lane ahead, not while making the move, or not at all, letting another driver get ahead and change lanes after he has done so, instead of speeding up to pass him and then cutting in front, and keeping phones and all the gadgetry off, these and others like these are still very good ideas. Maybe as good or even better than driving cars with “crumple” bodies and air bags — not that I have anything against those.

         

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        • This reply was modified 2 months, 3 weeks ago by  OscarCP.
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      • #1962668 Reply

        MrJimPhelps
        AskWoody_MVP

        Even if the modern car does its job and absorbs the impact of an accident, the car will likely be totalled. The wreck I described above would have totalled a modern small to midsize car (the size of my 66 Dodge Dart); so I definitely would not have been able to drive away.

        The idea of my car crumpling from an accident is not very reassuring; however, the idea of my car withstanding a high speed impact with very little damage is very reassuring.

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        • #1962729 Reply

          anonymous

          Hear! Hear! MrPhelps. I repeat post #1954836.

        • #1962794 Reply

          Ascaris
          AskWoody_MVP

          I don’t know about the ’66, but check out this test crash with a 1959 Chevy Bel Air and a 2009 Chevy Malibu, and in particular the area around the test driver.

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        • #1962874 Reply

          mn–
          AskWoody Lounger

          Oh, steel deforms just fine if it’s engineered right. Also a lot less finicky about metal fatigue than the lighter alloys.

          So no reason why a proper crumple structure couldn’t be made of steel.

          I’m told there were some old cars that were made of soft steel and would deform easily… even too easily, and got a bad reputation.

          making them look “Space Age”, with non-functional streamlined features and details, much shiny chrome and built large in size,

          Yeah, nonessential material on the outside, to be replaced after deforming on impact and protecting the occupants 😉 if only they were actually made to do that…

    • #1962825 Reply

      OscarCP
      AskWoody Plus

      Ascaris video shows a front-end collision at a relative high speed between two cars, a Chevy Malibu ca. 2009 with an old, if presumably in reasonably good condition, 1959 Chevy Bel Air. The Bel Air ends up showing more serious damage. And that is also true of its driver. But it’s hard to tell, after a serious collision, how much damage a car has suffered, because not all of it is readily visible. Also much depends on how a car is put together. Back in the day, the emphasis in designing car bodies was in making them look “Space Age”, with non-functional streamlined features and details, much shiny chrome and built large in size, with plenty of room inside for five occupants free  (driver excepted) to move unconstrained by seat belts. All that and more was emphasized in advertising as pluses, but not much emphasis was put on structural integrity and surviving collisions. On the other hand, newer cars, from the 80’s onward, have been built with better structural properties and are probably a lot tougher to demolish utterly in a collision.

      My old 1990 Geo Prizm (a.k.a. a Toyota Corolla assembled by GM), with its all-steel body, has survived low speed collisions with considerably larger vehicles suffering always minor damage, not symmetrical with that to the other vehicle. (Collisions all of which, believe it or not, were the other driver’s fault — it is like a curse my car has, to be attacked, as it were, at low speeds by rogue drivers of glorified bumper cars.) However, I probably shall fare poorly in this car in the event of a serious crash, with no air bags and a body that offers less protection to the driver than later models do. Although a lot better protection than that Bel Air ca. late nineteen fifties.

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    • #1968284 Reply

      anonymous

      anonymous #1954836 here. I feel plastic has its uses in various areas of the car, but the problem once again is plastics eventually loose the plasticizes and become brittle. I have been working on cars for decades. It could be something as simple as the plastic vents of the air conditioning breaking, like I have seen, to the plastic connection to the power steering pump fail and leak out fluid, then ruin the pump, all because of plastic and being cheap.

      The videos below are by Scotty Kilmer a mechanic. In both videos he shows how “plastic under the hood” is not a good idea.
      https://www.youtube[dot]com/watch?v=eS9duddPqUI go to 2:48 minutes
      https://www.youtube[dot]com/watch?v=8MmXIZPxD7A go to 3:10 minutes and at 3:25 minutes that actually happened to us.

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      • #1968411 Reply

        mn–
        AskWoody Lounger

        the problem once again is plastics eventually loose the plasticizes and become brittle. I have been working on cars for decades. It could be something as simple as the plastic vents of the air conditioning breaking,

        Then again there are metal alloys that are about as bad as some plastics about aging or thermal behaviour. Badly made cars occasionally have those. (And other things)

        Depending on climate, that might be important for some – plastic doesn’t usually rust or even oxidize much.

        And then the “soft” parts of course, where you might have a choice of plastic, rubber or leather for some parts…

        • #1968490 Reply

          anonymous

          Hello mn- you do have a point. A few years ago I was talking to a mechanic. I am not trying to be mean, but I am repeating what he said. He mentioned, he and his boss (the shop owner) made lots of money from Mercedes and BMW and went on to say that Mercedes used a metal intake manifold. This metal was something like magnesium and was very thin. The problem was after a few years the metal would corrode and get a leak. He mentioned that this could easily be remedied by plating the metal to prevent the corrosion, but they won’t do that. Manifold replacement for the car was a few thousand dollars and they made lots of money from situations like that. So yes even metal can go bad, if it is designed to.

          If you look at the videos I provided, Scotty Kilmer is a professional mechanic, and the items he mentions about plastic failures can’t be denied. The plastic power steering hose connection failed on us and that would had never happened if it were made of metal. He does go on to mention the good aspects of using plastic for other items.

          While I can understand using plastic for say, inner wheel wells in northern areas where salt is placed on the roads, I still can not go with many “plastic under the hood” components.

          Thank you mn-.

          • #1969666 Reply

            Ascaris
            AskWoody_MVP

            If you look at the videos I provided, Scotty Kilmer is a professional mechanic, and the items he mentions about plastic failures can’t be denied.

            But the metal failure you describe can’t be denied either, and it’s certainly not the only example.  If you would not conclude that metal parts are bad news because of the example of the Mercedes manifold, then why make the same assumption based on the failures of some plastic items?

            When any given part fails, you only have one point of data, that the part in question failed in x amount of time.  A mechanic will obviously see lots of parts that failed over time, and he may well know how long those parts lasted (if they were the factory part).  Still, if he were to try to establish a rough estimate of MTBF from what he’d seen, he’d be mistaken, since his sample was skewed.  He’d need a random sample to do that, and the sample of cars brought to a specific repair shop because of a problem is anything but random.

            Even if it were established that a given part had an unacceptably short service life, it would not be valid to extend that assumption to other parts that share a characteristic with the failed part without considerable further study.  About the most you could say from the Mercedes manifold would be that this particular part has a high failure rate in that particular application.  It would not be valid to say that intake manifolds are unreliable, or that magnesium parts are unreliable, or that metal parts are unreliable, or that metal intake manifolds are unreliable, or that Mercedes intake manifolds are unreliable (and so on).  Some of those statements could well be true, but it is not possible to conclude that just from the observation of a mechanic that has to replace a lot of one specific magnesium manifold on one model of car.

            A lot of people tend to think of plastic as junk, and that’s probably because plastic is cheap enough to be the material of choice when one wants to make a product cheaply… which is to say, “junk.”  Any plastic anything that fails typically elicits a “What did you expect, it’s plastic?” while anything metal that fails is “Wow, that must have been a heck of a (whatever) to break metal like this,” even if the failure that happened was specifically a failure mode of that metal (like metal fatigue).  It’s called confirmation bias, and no one’s immune to it.  After seeing how many ABS plastic bits have cracked  in my nearly 30 year old car (embrittlement), it’s one I can understand, but it wouldn’t be valid to project the fragility of those parts to different types of plastic in different applications in much newer cars.

            The use of plastic in car parts is certainly more prevalent than in years past, and it shows no sign of changing.  Naturally, the number of failures that are seen of plastic parts are also going to increase, even if the plastic parts are equally as durable/reliable as the metal parts they replace.

            If I were to guess, I’d say that plastic parts in roles like intake manifolds probably will not last as long as metal ones, but that would only be a guess.  I simply don’t have the data to support that assertion.  In other roles, plastic parts will easily outlast metal ones, as they are not usually subject to fatigue or corrosion.  It could well be that a plastic manifold in that Mercedes would outlast the metal one, since the metal one was known to have corrosion problems.

            And then, of course, is planned obsolescence, which can be engineered into anything.  A carmaker could engineer the manifold to last (essentially) forever, but why do that if a part that will last as long as the warranty is half the price?  They have to weigh the damage that failing car parts after the warranty will do to the reputation of the brand against the cost savings.

            In most cases, I’d guess that an intake manifold with a shorter life but a lower price would probably win the cost/benefit analysis most of the time.  New-car buyers are more likely to trade in the old car and buy another one at the end of the warranty period, so they’re less likely to care about the ongoing durability of the car (except to the degree that it affects resale value).  Those who buy used cars are of little concern to the carmakers.

             

             

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      • #1991083 Reply

        wavy
        AskWoody Plus

        I liked Kilmer’s vids thanks

        🍻

        Just because you don't know where you are going doesn't mean any road will get you there.
      • #1991137 Reply

        Sessh
        AskWoody Lounger

        Weird that you bring up Scotty Kilmer. I literally stumbled onto his videos for the first time yesterday. I will say that he’s absolutely right about the overuse of plastic car parts. I know a few people who work on cars and they all say the same things really. This is done to save money at the expense of quality and longevity while increasing their profits when customers pay (very high prices) to get these things fixed after the warranty is up.

        Of course they deliberately design cars to last just beyond the warranty before they start to fall apart. It’s okay to use plastic in some places and not in others such as in radiators and power steering systems which take a lot of direct heat. It should go without saying that it’s a bad idea to use plastic parts in applications where they will be exposed to very high temperatures on a regular basis. Metal will hold up, plastic won’t. It’s designed to fail.

    • #1969499 Reply

      OscarCP
      AskWoody Plus

      All-steel does not make much sense with good newer and even advanced materials of different composition available and useful to have, depending of the intended use of the vehicle, in certain, limited places in both the body, chassis and mechanical parts, as long the choice of material is correct and the parts are properly engineered. Still, given all that, an all-steel body with one of the modern designs available to make them safer under impact, is something I much rather have, not plastic. In particular it bothers me how car bumpers are now covered in this shiny layer of the same color as the front of the car, that will scuff, break and look not great with a little bad luck, be it when parallel-parking and finding the curb to be unexpectedly higher than it seemed, or when being touched by some other vehicle while parked in places where the individual spaces are narrow and some careful maneuvering is required to get in without causing problems.

      And, while on the use of all-steel in vehicle bodies, how about Musk’s choice of an all-steel body design, instead of one based on carbon-fiber, for the “Starship” spacecraft his company is building and testing and that, allegedly, will be capable of carrying 100 people to just about anywhere in the Solar System?

      https://www.space.com/elon-musk-starship-design-update-2019-preview.html

      Excerpt:

      Starship and Super Heavy [the giant rocket being developed as a booster further scaled-up in design that will follow the current  reusable, self-landing “Heavy” Space-X booster] will both be powered by SpaceX’s next-generation Raptor engine. The stainless-steel, 100-passenger ship will have six Raptors, whereas the first-stage rocket will boast 35 of the engines.” (Emphasis mine.)

      There is a video of Musk explaining the idea included in the article followed by other showing the assembly and testing of the spaceship. Quite impressive to see. Will it fly?

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    • #1969665 Reply

      Paul T
      AskWoody MVP

      capable of carrying 100 people to just about anywhere in the Solar System?

      As long as you don’t mind taking several years to get there – or has he invented FTL travel?

      cheers, Paul

      • #1971808 Reply

        OscarCP
        AskWoody Plus

        Six months to Mars, at current impulse ratings of rocket engines. A bit sooner with Starship’s set of multiple, high-impulse Raptor engines. While passengers can enjoy plenty of room to move about and privacy in Starship’s spacious (for a spacecraft) local areas and personal sleeping cubicles…

        https://en.wikipedia.org/wiki/Raptor_(rocket_engine_family)

        (In particular, have a look there at the enclosed table comparing the Raptor to other engines, near the end of the article.)

        Titan will come later, maybe with scales in: Moon, Mars, Ceres, and Ganymede. Book your Grand Tour soon, only 100 seats available in each tour!

        Now,  Mercury, well, that will take a while… No way to go directly, at present, because falling most of the way to the Sun soon gets too fast to slow down and go into Mercurian orbit with any type of engine now available. So lots of near-passes first, near Venus, Earth, and even Jupiter, to break gradually through multiple applications of the gravity-slingshot-effect maneuver. In other words: following the slow-paced Scenic Route!

        This might be high adventure in space, or pie in the sky. Who knows? Time, as always, will tell — in due course.

        And has the Tesla that Musk has sent on its way to the Asteroid Belt and back, in an eternal orbit, an all-steel body, or what?

        Tesla Model 3’s body structure is a strategic blend of aluminum and ultra high-strength steel

         

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    • #1971460 Reply

      anonymous

      Hello Ascaris. I have read your posts and feel you have very good ideas and contribute greatly. I like you and enjoy chatting with you.

      With that being said, I must ask what is the fascination of plastic underhood components people have today? I am basically a shade tree mechanic and ex hot-rodder, and know about automobiles, motorcycles, tractors, etc. and have worked on them. So I do know about cars.

      You mentioned, “I can think of a reason why a plastic manifold would be desirable. A plastic manifold should have a lot less heat soak, which could be a positive thing for performance (reducing intake air charge temperature).”

      This is a good idea. If one is solely focused on performance like a racer then yes, this fits the bill fine. But racers also understand life expectancy is not the issue, performance and winning is.

      If you are trying to lessen weight or alter heat characteristics for performance (to hot rod), or you only keep a car for 4 years, or you lease a car and when it starts to give trouble you return it for another, then I get it. If a component that rusts is replaced with a quality plastic component and this pans out and the part now lasts 10 years and the original sheet metal one lasted 6 years then I get it.

      But the only real reason manufacturers are using plastic is because with injection molding it is dirt cheap compared to casting one in Zinc, iron, “pot metal” or stamped sheet steel. Today the auto manufacturers are not concerned with making a car last much further than the warranty. Look at the resale value of Range Rover and BMW. The newer vehicles have a horrible resale value. Why? Because the quality (i.e. longevity) is not there and they use plastic everywhere. If it is not plastic then it is under engineered metal components that will just last beyond the warranty. They want you to buy a new car from them, not keep it running 15 years.

      When I was in high school we use to curse Ford and GM for using a nylon (plastic) timing gear for the camshaft. These failed on a regular basis even though used from the 1960’s. We replaced them with the normal cast iron. No more issues. No more being stranded like happened to me.

      Did you know that in the 1960’s GM – Pontiac, tried using nylon starter gears? Why, because they wanted to make it quieter when starting the engine! That is also why they were using nylon timing gears, to make it quieter. There was so much warranty work they quickly gave up on that idea. Money, money. If it saves them some then great, if it costs them then they stop using that material.

      You also mentioned, “In other roles, plastic parts will easily outlast metal ones, as they are not usually subject to fatigue or corrosion.” That is not totally true. While plastic will not corrode like metals like standard carbon steel will, is is know that plastics have a definite life expectancy from the plasticizers evaporating or leaching out of the plastic, thereby causing stress cracks from becoming more brittle. This is accelerated by heat, UV, and certain chemicals. Also don’t forget, below freezing cold makes plastic brittle and can fail too.

      As mentioned earlier in this topic, it was the plastic power steering hose connection that failed, leaked and we needed a new hose and subsequent pump. While it is true that a metal connection could have the gasket or O-Ring fail and leak, it would not had been from a stress crack failure due to the plasticizers leaching out from age and heat and the expansion/contraction associated with an underhood car part.

      For example, new cars have plastic radiator end tanks. This is because copper was getting expensive so manufacturers kept costs down by using plastic. In the very old days they had copper radiators. As time passed to cut costs the end tanks were made of brass since that is cheaper. Now they are plastic and it is not because it is better, once again, it is because injection molded plastic is “dirt cheap”.

      I do believe there are good advantages to using plastic in various areas of the automobile but I do have issues with it being on the engine or close to the exhaust manifolds.

      Thank you Ascaris (and others).

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      • #1971862 Reply

        Charlie
        AskWoody Plus

        You are so right.  I remember when the car companies started putting nylon timing chain gears in engines.  This had to be the worse design decision ever made.  I heard about so many of these plastic part engines failing at the worse times.  Most people didn’t even know that the timing chain gears were nylon.

        Win 7 Home Premium, x64, Intel i3-2120 3.3GHz, Groups B & L

        • #1971882 Reply

          OscarCP
          AskWoody Plus

          The timing chain is something like a bicycle chain that runs all around the engine block to synchronize the opening and closing of the cylinders’ valves. A broken timing chain, that usually happens suddenly and without previous warning, causes, at the very least (see the article with the link below) the engine to stop running, at once. In modern cars, that not only means that very quickly the car stops moving, for lack of wheel-propelling torque, whenever and wherever this happens (let’s say, in the fast lane of a fast moving and heavily transited freeway, with some maniac tailgating your car), but there is no longer power steering, power braking, or power anything… Breaking with the hand-brake, the only (not great) option to stop the car, at whatever speed it might be going at the time. As to that tailgating maniac coming fast just behind you…

          But that could just be the beginning of the trouble:

          https://www.carfax.com/blog/timing-chain-vs-timing-belt

          In the worst-case scenario, a broken timing belt or chain can quickly and entirely destroy a car’s engine. That’s because most of today’s power plants are what’s known as “interference” engines. With these units, when the valves open and close, they move in and out of the same cylinder space as the top of the piston. The timing system ensures the valves are out of the way when the piston comes up. If the belt or chain breaks, the valves don’t move and will be smashed by the piston head. If this happens at high rpm, a valve can snap right off and become a fast-moving projectile that leads to catastrophic engine failure.

          Windows 7 Professional, SP1, x64 Group B & macOS + Linux (Mint) => Win7 Group W + Mac&Lx

          • #1972835 Reply

            access-mdb
            AskWoody MVP

            But that’s been the case for donkey’s years. My father had a car in which the timing chain broke. I forget the damage caused and if the engine was wrecked but that was in the early 60s. As far as I’m aware, each belt has a recommended mileage. I’ve had a belt changed because the car’s mileage was the requisite value. ‘If it ain’t broke, don’t fix it’ looks a bit weak here!

            • #1973225 Reply

              mn–
              AskWoody Lounger

              As far as I’m aware, each belt has a recommended mileage. I’ve had a belt changed because the car’s mileage was the requisite value.

              Well, belt and chain wear a bit differently… and a belt will typically have BOTH a mileage limit AND an expiry date, because they’re usually made (at least partially) of materials that’ll degrade with age.

              Just booked yearly service with belt replacement, for the 7-seater.

              2 users thanked author for this post.
            • #1973347 Reply

              MrJimPhelps
              AskWoody_MVP

              When the timing chain broke (or perhaps the timing gear broke), no engine damage resulted; the car simply quit running till the problem was fixed. Therefore, you could drive forever till it broke, with no fear of engine damage.

              With a timing belt, however, you can’t do that; you have to change it according to the schedule, or you risk engine damage.

              This fabric engine part known as a “timing belt” was perhaps the first example of a “plastic” engine part. As I understand it, most cars have gone back to timing chains. I hope that the plastic intake manifolds and other plastic engine parts will be replaced by metal parts as well.

              Truly, when a car company sells a car with plastic engine parts, they are basically taking us all for fools, because what they are selling is very expensive junk, planned obsolescence.

              Group "L" (Linux Mint)
              with Windows 8.1 running in a VM
              1 user thanked author for this post.
            • #1973421 Reply

              Ascaris
              AskWoody_MVP

              It depends on whether the car uses an “interference” design or a “non-interference” design.  Many cars with timing belts have overhead cams, and a lot of these are interference designs that will crash the pistons into the valves if the cam(s) fail to turn.  The single cam, overhead-valve design of traditional in-case cams is not usually an interference design.  If it was, it would present the same issue as the belt if the timing chain were to fail.

              Edit: Dang it, Oscar beat me to it!

              Group "L" (KDE Neon User Edition 5.17.4).

              • This reply was modified 2 months, 1 week ago by  Ascaris.
            • #1973595 Reply

              OscarCP
              AskWoody Plus

              MrJimPhelps: “When the timing chain broke (or perhaps the timing gear broke), no engine damage resulted; the car simply quit running till the problem was fixed. Therefore, you could drive forever till it broke, with no fear of engine damage.

              Quite so, that was my own experience, the first time it happened to me. Thereafter, I have replaced the belt on schedule (and this reminds me that the time for a new replacement is getting close).

              But, please, notice that the excerpt from that article I copied in my previous entry starts with the words: “In the worst-case scenario…” In my opinion, “worst-case scenarios” that result in the car’s engine being wrecked, are things worth keeping in mind. Always.

              Windows 7 Professional, SP1, x64 Group B & macOS + Linux (Mint) => Win7 Group W + Mac&Lx

            • #1974011 Reply

              mn–
              AskWoody Lounger

              planned obsolescence.

              Predictable wear isn’t necessarily planned obsolescence… as long as replacements keep being made. Part commonality with other models is an advantage.

              Heh. It’s not like things like gearboxes and such are immune to that. With some people’s driving habits it’s not unheard of to arrive at the design lifetime of a gearbox in less than 5 years, from new.

            • #1989601 Reply

              MrJimPhelps
              AskWoody_MVP

              When they go from a metal intake manifold which will likely last forever to a plastic intake manifold which will likely need to be replaced after a few years, that is an example of planned obsolescence.

              I shouldn’t have to replace engine parts if I take care of my car. But I WILL have to replace them every few years if they are made out of plastic.

              Group "L" (Linux Mint)
              with Windows 8.1 running in a VM
      • #1973418 Reply

        Ascaris
        AskWoody_MVP

        Thanks for the kind words!

        Without having heard any automaker representative’s comments on the subject, I’d have to agree that the reason for the plastic underhood components is to save money.  Any given component on a car (or any other engineered product) is designed with a certain service life in mind, and as long as a plastic part will meet the requirement, it’s good, as far as they are concerned.  I don’t know that it’s necessarily a case of “designed to fail” in the classic planned obsolescence way… it may well be, or it may be a matter of “our intake manifolds are meant to have at least a five-year lifespan, and our testing shows that ours do.”  It’s not planned to fail so much as not engineered to live beyond a certain length of time, which is a subtle but real difference.

        Plastic parts that are meant to live only five years (though we, the consumers, are not likely to ever know what the actual design lifespan would be) will tend to be unreliable long-term.  That’s a function of parts being designed for short service lives, with the exact formulation of plastic being chosen for the lowest cost possible for the indicated service life.  A non-plastic part that’s only meant to live five years would potentially be just as problematic, and in the automotive world, many are.

        If one was to design a part like an intake manifold for a short life, it would probably be some form of plastic that it would be made from, but that doesn’t mean plastic itself indicates a short design (or actual) life.  It’s quite possible that a plastic part engineered to provide acceptable levels of service for 30 years would have the same effectively unlimited service life as a metal part.

        Consider the problem with metal fatigue in airliner skins, which is one reason that conventional aluminum-skinned planes are pressurized to ~8000 feet, which is quite a departure from the near sea level pressure in which most people live.  The Boeing 787 Dreamliner is constructed of carbon fiber in the fuselage– which is to say carbon-fiber reinforced resin… or plastic, which won’t fatigue like aluminum.  That allows pressurization closer to what the passengers are used to, increasing comfort and decreasing fatigue, not to mention allowing larger windows, which make the passengers happier too.  Its immunity to corrosion allows higher in-cabin humidity levels, which also increases passenger (and crew) comfort.  The great amount of wing flex that carbon fiber allows is supposed to reduce felt turbulence too, which passengers will also appreciate.

        There was an anecdote of an airline executive expressing doubt about the carbon-fiber construction.  It’s not uncommon for luggage carts and other ground equipment to smack into an aircraft.  In an aluminum plane, it typically causes a tear that can be repaired with a doubler plate.  That would not be possible with the carbon fiber fuselage of the 787, though, so what then?

        As the anecdote goes, the Boeing guy obtained some part that was an example of the material the Dreamliner was made from, and challenged him to damage it, even with a hammer.  After a short time of failing to cause any visible damage at all, as the tale goes, the executive immediately placed the order.

        Carbon-fiber reinforced resin is an example of plastic built for performance, not for extreme cost reduction.  If the carmakers wanted to make high-quality, long life plastic parts, they could do so, and perhaps some cars do.  I would love to have a carbon-fiber driveshaft for my car… there are several advantages over metal shafts, but it’s not worth the cost to me, as I never go to the drag strip (where metal shafts need to have a driveshaft loop to pass tech inspection, but not carbon fiber ones), and the resonance of the aluminum shaft I do have is not a concern, as the diff gears are worn-in and dead quiet (it did sing quite a lot when I first had the ring and pinion installed!).

        Some high-end cars may have them as factory equipment… I would guess that they do.

         

        Group "L" (KDE Neon User Edition 5.17.4).

        1 user thanked author for this post.
        • #1973604 Reply

          OscarCP
          AskWoody Plus

          Ascaris,

          While I agree with most of your comment I am responding to, I must point out that the following is not quite so: “That [the use of an advanced carbon-fiber composite in the body of the new Boeing’s “Dreamliner”] allows pressurization closer to what the passengers are used to, increasing comfort and decreasing fatigue, not to mention allowing larger windows, which make the passengers happier too.

          At least, concerning those “larger windows, which make passengers happier”, unfortunately, is not quite so, at lest not for me. Because the first thing that people do these days and totally without exception, once they are seated, is to close all the windows so they can watch videos, play games or scroll and scroll on their smart-phone screens, etc., choosing to do so quite undisturbed by natural light or terrific scenery. I loved, once upon a time, when flying to California, to look down from 10 km altitude, at the Grand Canyon system, Meteor Crater, the Rockies and other very visible landmarks through the usually clear desert air. Or the Alaskan mountains on approach to Anchorage. Well, one no longer can do that, thanks to fellow passengers’ attachment to “Tech”.

          Oh, well… Long live “Tech”!, then. Now, I always carry a book, just in case. And, sad to tell, this works for me, every single time.

          My point being that the use of good composite materials in the body of aircraft, while allowing for better structural integrity and, maybe, greater safety in flight, is not necessarily taken advantage of, even when this is actually available to them as an option, by today’s traveling public.

          Windows 7 Professional, SP1, x64 Group B & macOS + Linux (Mint) => Win7 Group W + Mac&Lx

    • #1989571 Reply

      anonymous

      Hello Ascaris et al., anon #1971460 here.

      Here is another mechanic Scotty Kilmer video on automobiles where he comments on what he has seen good or bad with newer cars.

      Scotty Kilmer https://www.youtube.com/watch?v=-skXw0I05Jg go to 6:50 if you don’t want to see the whole video.

      Thank you.

      1 user thanked author for this post.
      • #1989613 Reply

        MrJimPhelps
        AskWoody_MVP

        “If you spend $42,000 and up for an SUV, you expect quality.” -Scotty Kilmer

        Precisely.

        Group "L" (Linux Mint)
        with Windows 8.1 running in a VM

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