3 ms·

I will say I’m surprised how far apart the two boxes are in the car. I guess they’re not where I thought. I would assume they’re both up near the dash.

by MBCook 7mo ago

kube-system 7mo ago
The passenger side kick panel or behind the glove box are two very common places for vehicle computers -- some cars have them under the hood, which I always thought was a bad idea.
- msisk6 7mo ago
  My RAM truck with the Cummins diesel engine has the engine computer mounted on the engine block. You'd think the heat and exposure to the elements would make that a bad idea, but I suppose Cummins knows what they're doing.
  - kube-system 7mo ago
    Hehe I was thinking about FCA/Stellantis vehicles when I wrote that. I know it works and there are components made to work in that environment but it always felt intuitively wrong to me. Especially when the other side of the firewall is a much better environment and not far away
    - yearolinuxdsktp 7mo ago
      It’s because when placed inside the engine bay, the large wiring harness is shorter, which is not only cheaper, but also shorter wiring helps with the consistency of electrical timing and reduces noise.
  - yearolinuxdsktp 7mo ago
    Yes they do. They can tolerate engine bay heat, but not exhaust heat. They are usually shielded from getting soaked. Some Mazdas put the metal-cased engine computer in a plastic air box that feeds cold air from the front, to help ensure the engine computer stays cool enough. In general, I believe the cooling airflow from the frontal air and the cooling fans keeps engine bay in check. For example, this is the board that’s used in Mazda CX-5 2017+ engine computers (mfr Denso), it lists max temperature range of +150C: https://www.renesas.com/en/document/mah/rh850e1l-users-manual-hardware?r=1255086 https://www.renesas.com/en/document/mah/rh850e1l-users-manua...
    - msisk6 7mo ago
      Yeah, on the Cummins the ECU is mounted on the intake side of the engine away from the exhaust and turbo and toward the front right under the fuel injection pump so it gets lots of cooling air. This thread is interesting to me 'cause I'm also a software guy and recently took a job dealing with building fighter jets and the amount of engineering going into the wiring and computers on those things is insane. It's been a very interesting learning experience.
  - phil21 7mo ago
    My car has it under the passenger seat. Sounds alright until you realize after spilling a bunch of flower vases in the trunk (hatchback) that the computer has literally no case on it and immediately shorts out while driving. Or a passenger spills a drink in the rear seat cup holder. There is now a recall notice to pull the back seat out to install a $5 plastic cover over the thing. And yep, it’s the main computer for the car which controls the electronic transmission etc. Immediate full on engine-shuts-off at speed on the freeway and you require a flatbed to tow it away level of broken. I’m sure the engine ECU is in the engine bay, but holy hell what a surprise!
    - bdunks 7mo ago
      I had a car with an all wheel drive computer in a similar spot in the late 2000s. I had a small crack in the rubber seal around my sunroof from parking outside in the elements. When it rained, water seeped in, made its way down the a-pillar, pooled under the seat, and fried the computer. Expensive fix but I was able to drive it to the shop.
  - cuvinny 7mo ago
    Could be because they sale crate engines.
- kotaKat 7mo ago
  If you'd like the cursed location for a vehicle computer, have the Smart fortwo's SAM. It's the fuse box! It's also notorious for having awful solder connections and failing outright. https://evilution.co.uk/mod/sam-unit-solder-repair.htm https://evilution.co.uk/mod/sam-unit-solder-repair.htm (and Aging Wheels: https://www.youtube.com/watch?v=n8AAleKR33Q https://www.youtube.com/watch?v=n8AAleKR33Q)

I will say I’m surprised how far apart the two boxes are in the car. I guess they’re not where I thought. I would assume they’re both up near the dash.

by MBCook 7mo ago

I will say I’m surprised how far apart the two boxes are in the car. I guess they’re not where I thought. I would assume they’re both up near the dash.

kube-system 7mo ago

The passenger side kick panel or behind the glove box are two very common places for vehicle computers -- some cars have them under the hood, which I always thought was a bad idea.

msisk6 7mo ago
My RAM truck with the Cummins diesel engine has the engine computer mounted on the engine block. You'd think the heat and exposure to the elements would make that a bad idea, but I suppose Cummins knows what they're doing.
- kube-system 7mo ago
  Hehe I was thinking about FCA/Stellantis vehicles when I wrote that. I know it works and there are components made to work in that environment but it always felt intuitively wrong to me. Especially when the other side of the firewall is a much better environment and not far away
  - yearolinuxdsktp 7mo ago
    It’s because when placed inside the engine bay, the large wiring harness is shorter, which is not only cheaper, but also shorter wiring helps with the consistency of electrical timing and reduces noise.
- yearolinuxdsktp 7mo ago
  Yes they do. They can tolerate engine bay heat, but not exhaust heat. They are usually shielded from getting soaked. Some Mazdas put the metal-cased engine computer in a plastic air box that feeds cold air from the front, to help ensure the engine computer stays cool enough. In general, I believe the cooling airflow from the frontal air and the cooling fans keeps engine bay in check. For example, this is the board that’s used in Mazda CX-5 2017+ engine computers (mfr Denso), it lists max temperature range of +150C: https://www.renesas.com/en/document/mah/rh850e1l-users-manual-hardware?r=1255086 https://www.renesas.com/en/document/mah/rh850e1l-users-manua...
  - msisk6 7mo ago
    Yeah, on the Cummins the ECU is mounted on the intake side of the engine away from the exhaust and turbo and toward the front right under the fuel injection pump so it gets lots of cooling air. This thread is interesting to me 'cause I'm also a software guy and recently took a job dealing with building fighter jets and the amount of engineering going into the wiring and computers on those things is insane. It's been a very interesting learning experience.
- phil21 7mo ago
  My car has it under the passenger seat. Sounds alright until you realize after spilling a bunch of flower vases in the trunk (hatchback) that the computer has literally no case on it and immediately shorts out while driving. Or a passenger spills a drink in the rear seat cup holder. There is now a recall notice to pull the back seat out to install a $5 plastic cover over the thing. And yep, it’s the main computer for the car which controls the electronic transmission etc. Immediate full on engine-shuts-off at speed on the freeway and you require a flatbed to tow it away level of broken. I’m sure the engine ECU is in the engine bay, but holy hell what a surprise!
  - bdunks 7mo ago
    I had a car with an all wheel drive computer in a similar spot in the late 2000s. I had a small crack in the rubber seal around my sunroof from parking outside in the elements. When it rained, water seeped in, made its way down the a-pillar, pooled under the seat, and fried the computer. Expensive fix but I was able to drive it to the shop.
- cuvinny 7mo ago
  Could be because they sale crate engines.
kotaKat 7mo ago
If you'd like the cursed location for a vehicle computer, have the Smart fortwo's SAM. It's the fuse box! It's also notorious for having awful solder connections and failing outright. https://evilution.co.uk/mod/sam-unit-solder-repair.htm https://evilution.co.uk/mod/sam-unit-solder-repair.htm (and Aging Wheels: https://www.youtube.com/watch?v=n8AAleKR33Q https://www.youtube.com/watch?v=n8AAleKR33Q)