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Except in Mazdas case the data was there to characterize it. They were notorious for failing very early and suffered bad seals around the rotary shaft. This has

by 14 3y ago

Except in Mazdas case the data was there to characterize it. They were notorious for failing very early and suffered bad seals around the rotary shaft. This has been well known for a long time. Many Rx owners knew ride it for 100k miles then sell it before it is too late.

Retric 3y ago
That rate isn’t a deal killer for a plug in hybrid. The engine might see ~1/4th the ware per mile spending the vast majority of its time off. Meanwhile hybrids really want a small and lightweight engine because of all the extra equipment.
- willis936 3y ago
  Right but then why not use a more efficient and reliable engine? The motors will last hundreds of thousands of miles. The power circuitry should have a similar run if kept cool. Why have an ICE that's more likely to fail with lower thermal efficiency? The engine used in Toyota's most popular cars runs in Atkinson most of the time with a 40% thermal efficiency. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7425626/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7425626/
  - Retric 3y ago
    Because the engine isn’t the only thing being optimized. Suppose your options are 50 miles of effective plug in range and a 40% efficient engine or a 35% efficient engine and a 100 miles of plug in range. The second option might use a lot less gas. It’s not just the cost of batteries that’s a concern resulting in short plug in hybrid ranges. Weight is a real limiting factor when you also need a gas engine and large fuel tank.
    - willis936 3y ago
      That would be a worthy trade, but that is vastly overstating the weight of aluminum block engines compared to Li+ and not at all realistic.
      - Retric 3y ago
        Atkinson engines have poor power to weight ratio at maximum efficiency, if you’re going to maintain that 40% then the engine needs to be oversized and under utilized. This is why many hybrids have seemingly much more power than they need. Thus the 194HP Prius vs 75 HP on a CX-90 plug in SUV. Also it’s not just that you can have extra Li+ it’s also pushing around less dead weight when the engine is off. So you can get fairly close to a 50 mile range difference depending on exact setup. Alternatively you can have a smaller Atkinson engine and a larger reserve on the battery, but that also costs range while still being heavier.
        pfdietz 3y ago
        It could make more sense to use a conventional engine, but get extra expansion (the kind an Atkinson/Miller cycle engine gets from the longer expansion stroke) by turbo-compounding. That is, exhaust gases (still at greater than ambient pressure) go through a turbine that is coupled to the output shaft, or to another generator, rather than being used to drive a compressor as in a conventional turbo. Or, attach a motor/generator to a conventional turbo and be able to have it operate in both modes and use the battery to help overcome turbo lag.
        Retric 3y ago
        Possibly, but that’s a lot of separate systems. It might make sense to look into a turbine engine on a hybrid. Though that’s probably been investigated I doubt anyone has invested the kind of time and money needed to make a real shot of it.
      - eptcyka 3y ago
        You will never be able to match the weight of a Wankel with a regular reciprocating piston engine, all other parameters being equal.
  - fransje26 3y ago
    > The motors will last hundreds of thousands of miles. They might, but with the current average build quality of the car industry, the rest of the car will die well before that..
  - everybodyknows 3y ago
    > The engine uses port and side direct fuel injection systems (PFI/GDI, referred to by Toyota as D-4S); a cooled, external exhaust gas recirculation system (cEGR); and a wide range of authority variable valve timing with electric phasing on the intake camshaft and hydraulic phasing on the exhaust camshaft. Atkinson Cycle is implemented using late intake valve closing (LIVC). Effective compression ratio is varied by varying intake camshaft phasing. Clever indeed.
Supermancho 3y ago
I had an RX-8 for years. It was made in 2007. Someone defaulted on the loan or lost it in a divorce and drove it into a lake, marking it salvage. I bought it for 25k and was the owner from 2009 to 2019, from 60k to over 150k mi. The maintenance was a bit pricey, due to the fuel injection problems and the electronics would fail in extreme heat of sustained 110+ outside temp (southern california heat) or cold (seattle mornings). I eventually sold it for 9k to a collector. Not a bad deal at all.
- nogridbag 3y ago
  Wait you paid 25k for a used/salvage RX-8 in 2009? That sounds crazy. I think I bought one new for around 26k in 2008.
  - kcrwfrd_ 3y ago
    That does sound crazy. The sticker price for the brand new Subaru BRZ limited manual transmission I got in 2012 was $28k.
  - Supermancho 3y ago
    A new RX8 Gran Touring in 2009 was ~38k out the door, iirc. I completed the purchase of one red new gran touring from Mazda, for delivery. The inventory was already taken, so they tried to swap a yellow and I cancelled. The next shipment was in another 8 months. Obviously, the internet RX8 community was active and I knew what was a reasonable pricing, at the time. I looked locally and I had a salvage checked out at Mazda. It was clean. As I mentioned, I sold it to a collector for 9k ~10 years later, as it was still in near-mint condition, regardless of the title status.
- amatecha 3y ago
  $25k USD? That does sound really high for a salvage RX-8 in 2009. My 2005 RX-8 was about $12k CAD in 2011 and was not salvage status. Though I guess yours was just a couple years old, mine was older, but still. In regards to reliability, not long into owning it I had to get the engine rebuilt due to low compression (luckily JUST within the extended warranty period which Mazda offered due to the very issue everyone in here is mentioning, loss of compression due to failing seals).

by 14 3y ago

Retric 3y ago

That rate isn’t a deal killer for a plug in hybrid. The engine might see ~1/4th the ware per mile spending the vast majority of its time off. Meanwhile hybrids really want a small and lightweight engine because of all the extra equipment.

willis936 3y ago
Right but then why not use a more efficient and reliable engine? The motors will last hundreds of thousands of miles. The power circuitry should have a similar run if kept cool. Why have an ICE that's more likely to fail with lower thermal efficiency? The engine used in Toyota's most popular cars runs in Atkinson most of the time with a 40% thermal efficiency. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7425626/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7425626/
- Retric 3y ago
  Because the engine isn’t the only thing being optimized. Suppose your options are 50 miles of effective plug in range and a 40% efficient engine or a 35% efficient engine and a 100 miles of plug in range. The second option might use a lot less gas. It’s not just the cost of batteries that’s a concern resulting in short plug in hybrid ranges. Weight is a real limiting factor when you also need a gas engine and large fuel tank.
  - willis936 3y ago
    That would be a worthy trade, but that is vastly overstating the weight of aluminum block engines compared to Li+ and not at all realistic.
    - Retric 3y ago
      Atkinson engines have poor power to weight ratio at maximum efficiency, if you’re going to maintain that 40% then the engine needs to be oversized and under utilized. This is why many hybrids have seemingly much more power than they need. Thus the 194HP Prius vs 75 HP on a CX-90 plug in SUV. Also it’s not just that you can have extra Li+ it’s also pushing around less dead weight when the engine is off. So you can get fairly close to a 50 mile range difference depending on exact setup. Alternatively you can have a smaller Atkinson engine and a larger reserve on the battery, but that also costs range while still being heavier.
      - pfdietz 3y ago
        It could make more sense to use a conventional engine, but get extra expansion (the kind an Atkinson/Miller cycle engine gets from the longer expansion stroke) by turbo-compounding. That is, exhaust gases (still at greater than ambient pressure) go through a turbine that is coupled to the output shaft, or to another generator, rather than being used to drive a compressor as in a conventional turbo. Or, attach a motor/generator to a conventional turbo and be able to have it operate in both modes and use the battery to help overcome turbo lag.
        Retric 3y ago
        Possibly, but that’s a lot of separate systems. It might make sense to look into a turbine engine on a hybrid. Though that’s probably been investigated I doubt anyone has invested the kind of time and money needed to make a real shot of it.
    - eptcyka 3y ago
      You will never be able to match the weight of a Wankel with a regular reciprocating piston engine, all other parameters being equal.
- fransje26 3y ago
  > The motors will last hundreds of thousands of miles. They might, but with the current average build quality of the car industry, the rest of the car will die well before that..
- everybodyknows 3y ago
  > The engine uses port and side direct fuel injection systems (PFI/GDI, referred to by Toyota as D-4S); a cooled, external exhaust gas recirculation system (cEGR); and a wide range of authority variable valve timing with electric phasing on the intake camshaft and hydraulic phasing on the exhaust camshaft. Atkinson Cycle is implemented using late intake valve closing (LIVC). Effective compression ratio is varied by varying intake camshaft phasing. Clever indeed.

Supermancho 3y ago

I had an RX-8 for years. It was made in 2007. Someone defaulted on the loan or lost it in a divorce and drove it into a lake, marking it salvage. I bought it for 25k and was the owner from 2009 to 2019, from 60k to over 150k mi. The maintenance was a bit pricey, due to the fuel injection problems and the electronics would fail in extreme heat of sustained 110+ outside temp (southern california heat) or cold (seattle mornings). I eventually sold it for 9k to a collector. Not a bad deal at all.

nogridbag 3y ago
Wait you paid 25k for a used/salvage RX-8 in 2009? That sounds crazy. I think I bought one new for around 26k in 2008.
- kcrwfrd_ 3y ago
  That does sound crazy. The sticker price for the brand new Subaru BRZ limited manual transmission I got in 2012 was $28k.
- Supermancho 3y ago
  A new RX8 Gran Touring in 2009 was ~38k out the door, iirc. I completed the purchase of one red new gran touring from Mazda, for delivery. The inventory was already taken, so they tried to swap a yellow and I cancelled. The next shipment was in another 8 months. Obviously, the internet RX8 community was active and I knew what was a reasonable pricing, at the time. I looked locally and I had a salvage checked out at Mazda. It was clean. As I mentioned, I sold it to a collector for 9k ~10 years later, as it was still in near-mint condition, regardless of the title status.
amatecha 3y ago
$25k USD? That does sound really high for a salvage RX-8 in 2009. My 2005 RX-8 was about $12k CAD in 2011 and was not salvage status. Though I guess yours was just a couple years old, mine was older, but still. In regards to reliability, not long into owning it I had to get the engine rebuilt due to low compression (luckily JUST within the extended warranty period which Mazda offered due to the very issue everyone in here is mentioning, loss of compression due to failing seals).