4 ms·

> A cheap generic cat might have the bare minimum amount of catalyst, and might not do a very good job It depends on the car/engine. My old Mazda RX-8 had a hu

by Alupis 6y ago

> A cheap generic cat might have the bare minimum amount of catalyst, and might not do a very good job It depends on the car/engine. My old Mazda RX-8 had a huge cat - longer than the muffler and cost me $2,000 to replace (including labor) back in the late 2000's. The rotary engine in that vehicle had a terribly difficult time passing California's emission laws even when it was brand new off the lot - which led to strange "hacks" including a blower motor that moved high volumes of air through the exhaust to heat the cat sooner and somehow improve it's numbers, among other things. I assume the extra-long cat was part of the shenanigans Mazda had to go through to get it compliant.

elihu 6y ago
It's funny you mention the RX-8, since I'm in the (slow) process of converting one to electric. That weird cat blower was one of the many parts I removed while thinking "I'm glad I don't have to understand or care about why this car needed something like that in the first place".
- Alupis 6y ago
  Just talking about the RX-8 brings back great memories - what a strange, yet beautiful car! The cat blower, and the subtle whining sound it made when you started up cold was one of the ways every RX-8 owner was hazed into the fold... after calling the dealer or posting on a forum and finding out it's entirely normal! Other oddities included how it deliberately burned oil (scaring new owners into thinking they had a serious engine problem), and how you were required to drive it hard to clear out its engine ports (multiple Mazda mechanics confirmed this factoid) - driving it like a normal car would literally clog up the exhaust ports and cause a loss of power (something to do with the lack of moving valves). If memory serves right, it had only 3 (!!!) moving parts in the engine, and was perfectly content to hang out at 9,000 RPM all day - that's incredible. But, it seems the issues Mazda had maintaining it's emission certifications, and warranty issues with those apex seals (mine had 3 engine replacements over it's lifetime) eventually caused it to be retired. I was sad back then, and still sad we don't have a new improved version - there's really nothing else quite like it out there, not even the RX-7. It really was/is an enthusiast's car. Good luck on your project - sounds like a fun one!
  - elihu 6y ago
    I'm hoping LiquidPiston's rotary engine design pans out: https://news.ycombinator.com/item?id=25450477 https://news.ycombinator.com/item?id=25450477 In theory, it should fix some of the maintenance issues (apex seals are attached to a stationary part of the engine where they can be more easily lubricated) and fuel efficiency / emissions issues (combustion chamber is closer to spherical). I like the idea of the Mazda rotary engine, but I'm not really surprised they stopped making them, due to fuel economy and emissions. And at them moment, the hundred-thousand mile engine rebuild interval basically means you can get an RX-8 with a bad engine for almost nothing, which opens up a nice opportunity for EV conversion. It's hard to imagine a nicer platform to start from.
    - Alupis 6y ago
      Wow, that LiquidPiston rotary looks very interesting! I hadn't seen that before - I too hope it pans out. > I'm not really surprised they stopped making them, due to fuel economy... Eh, nobody bought that car for the fuel economy! The car sold itself... just one test drive and you had to have it. I've owned and driven muscle and other sports cars, and still nothing compares to the RX-8 - it's just such a unique experience. Not sure how you're doing the conversion, but if you're keeping the carbon fiber driveshaft (vs. a motor on each wheel I suppose), there will be nothing keeping it from screaming off the line with an electric motor under the hood (traditionally the wankel wasn't good off the line with low RPM's, power band kicking in around 6500 if I recall - could make for a great "sleeper"). Although I'm unsure if the driveshaft would stand up to the torque a motor would output, since the wankel wasn't particularly torquey. If you're not already, keep a blog and pictures of the conversion - that would make for an interesting read!
      - elihu 6y ago
        > Eh, nobody bought that car for the fuel economy! True enough, but I'm sure there are other factors in play, such as public policy. Fuel economy standards have been going up. The motor I'm putting in my conversion is a Netgain Hyper9 (high-voltage, double-ended shaft version). It's about 120 horsepower and less than 200 foot pounds of torque, so in theory the clutch/transmission/driveshaft should be fine. (I'm keeping the 6-speed transmission.) It probably won't be particularly fast, but we'll see. More powerful AC motors exist, but they tend to be expensive. I haven't posted any pictures yet; I've been meaning to, just haven't gotten around to it. There's another guy in the UK I think with a youtube channel that's doing close to the same thing, but with a Leaf motor.
kube-system 6y ago
> moved high volumes of air through the exhaust to heat the cat sooner and somehow improve it's numbers This is because the catalyst works more efficiently at higher temperatures. Emission regs also test vehicles under a cold start. The quicker the cat can be heated up, the quicker it starts working, and that equals fewer total emissions over a given period of operation.

by Alupis 6y ago

elihu 6y ago

It's funny you mention the RX-8, since I'm in the (slow) process of converting one to electric. That weird cat blower was one of the many parts I removed while thinking "I'm glad I don't have to understand or care about why this car needed something like that in the first place".

Alupis 6y ago
Just talking about the RX-8 brings back great memories - what a strange, yet beautiful car! The cat blower, and the subtle whining sound it made when you started up cold was one of the ways every RX-8 owner was hazed into the fold... after calling the dealer or posting on a forum and finding out it's entirely normal! Other oddities included how it deliberately burned oil (scaring new owners into thinking they had a serious engine problem), and how you were required to drive it hard to clear out its engine ports (multiple Mazda mechanics confirmed this factoid) - driving it like a normal car would literally clog up the exhaust ports and cause a loss of power (something to do with the lack of moving valves). If memory serves right, it had only 3 (!!!) moving parts in the engine, and was perfectly content to hang out at 9,000 RPM all day - that's incredible. But, it seems the issues Mazda had maintaining it's emission certifications, and warranty issues with those apex seals (mine had 3 engine replacements over it's lifetime) eventually caused it to be retired. I was sad back then, and still sad we don't have a new improved version - there's really nothing else quite like it out there, not even the RX-7. It really was/is an enthusiast's car. Good luck on your project - sounds like a fun one!
- elihu 6y ago
  I'm hoping LiquidPiston's rotary engine design pans out: https://news.ycombinator.com/item?id=25450477 https://news.ycombinator.com/item?id=25450477 In theory, it should fix some of the maintenance issues (apex seals are attached to a stationary part of the engine where they can be more easily lubricated) and fuel efficiency / emissions issues (combustion chamber is closer to spherical). I like the idea of the Mazda rotary engine, but I'm not really surprised they stopped making them, due to fuel economy and emissions. And at them moment, the hundred-thousand mile engine rebuild interval basically means you can get an RX-8 with a bad engine for almost nothing, which opens up a nice opportunity for EV conversion. It's hard to imagine a nicer platform to start from.
  - Alupis 6y ago
    Wow, that LiquidPiston rotary looks very interesting! I hadn't seen that before - I too hope it pans out. > I'm not really surprised they stopped making them, due to fuel economy... Eh, nobody bought that car for the fuel economy! The car sold itself... just one test drive and you had to have it. I've owned and driven muscle and other sports cars, and still nothing compares to the RX-8 - it's just such a unique experience. Not sure how you're doing the conversion, but if you're keeping the carbon fiber driveshaft (vs. a motor on each wheel I suppose), there will be nothing keeping it from screaming off the line with an electric motor under the hood (traditionally the wankel wasn't good off the line with low RPM's, power band kicking in around 6500 if I recall - could make for a great "sleeper"). Although I'm unsure if the driveshaft would stand up to the torque a motor would output, since the wankel wasn't particularly torquey. If you're not already, keep a blog and pictures of the conversion - that would make for an interesting read!
    - elihu 6y ago
      > Eh, nobody bought that car for the fuel economy! True enough, but I'm sure there are other factors in play, such as public policy. Fuel economy standards have been going up. The motor I'm putting in my conversion is a Netgain Hyper9 (high-voltage, double-ended shaft version). It's about 120 horsepower and less than 200 foot pounds of torque, so in theory the clutch/transmission/driveshaft should be fine. (I'm keeping the 6-speed transmission.) It probably won't be particularly fast, but we'll see. More powerful AC motors exist, but they tend to be expensive. I haven't posted any pictures yet; I've been meaning to, just haven't gotten around to it. There's another guy in the UK I think with a youtube channel that's doing close to the same thing, but with a Leaf motor.

kube-system 6y ago

> moved high volumes of air through the exhaust to heat the cat sooner and somehow improve it's numbers This is because the catalyst works more efficiently at higher temperatures. Emission regs also test vehicles under a cold start. The quicker the cat can be heated up, the quicker it starts working, and that equals fewer total emissions over a given period of operation.