Car Chat

[r0tor]

Actually, ICE are most efficient at wide open throttle; which is why more powerful cars get worse mileage in general.

Well wide open intake valves are one of the reasons diesels are better... But we are talking only a few efficiency points difference while an electric motor is about 60% better

[Speed_Racer]

Craziness!!
https://www.thedrive.com/news/40408/ecuadors-downhill-soapbox-street-racing-is-verifiably-bananas

¡Increíble!

[FoMoJo]

Craziness!!
https://www.thedrive.com/news/40408/ecuadors-downhill-soapbox-street-racing-is-verifiably-bananas

That is one long hill.

[AutobahnSHO]

super low profile tires on a duallie super duty truck is one of the stupidest things I've seen.

[cawimmer430]

Does anyone know what the thermal efficiency of a Wankel engine is? I can't seem to find any concrete numbers on Google.

[Laconian]

Does anyone know what the thermal efficiency of a Wankel engine is? I can't seem to find any concrete numbers on Google.

IIRC it's pretty crap. Packaging, smoothness, and volumetric efficiency are their strong suits, but you don't get a Wankel for fuel efficiency...

[CaminoRacer]

ICE engines being most efficient at full throttle is a drawback. Electric motors have a wide efficiency range. If an ICE is most efficient at WOT, then the most efficient application would be a tiny tiny engine that only makes enough power to sustain highway speeds at WOT, because otherwise you can't be in your efficient range without accelerating.

[Laconian]

ICE engines being most efficient at full throttle is a drawback. Electric motors have a wide efficiency range. If an ICE is most efficient at WOT, then the most efficient application would be a tiny tiny engine that only makes enough power to sustain highway speeds at WOT, because otherwise you can't be in your efficient range without accelerating.

Sounds like my MIL's 900cc Captur It slows down on hills even with the pedal to the floor.

[Soup DeVille]

ICE engines being most efficient at full throttle is a drawback. Electric motors have a wide efficiency range. If an ICE is most efficient at WOT, then the most efficient application would be a tiny tiny engine that only makes enough power to sustain highway speeds at WOT, because otherwise you can't be in your efficient range without accelerating.

This is correct. Also the driving theory behind displacement on demand.

[FoMoJo]

This is correct. Also the driving theory behind displacement on demand.

Are they not most efficient at maximum torque?

[MX793]

Are they not most efficient at maximum torque?

Many ways to define efficiency.  Thermal efficiency, fuel efficiency, BSFC...  Some of these are characteristics of the engine.  Others characteristic of the entire vehicle system.  Fuel economy is a function of the entire vehicle system.  Same engine in 2 different vehicles with different aero, gear ratios, wheels/tires, etc will return different fuel economies.

An engine is most efficient at WOT (throttle restrictions rob efficiency).  BSFC is typically at optimum near peak torque.  Both of these are engine characteristics, not vehicle characteristics.

[Laconian]

Are CVT cars programmed to favor WOT at much higher transmission ratios to keep the engine at peak torque?

My Outback revs the engine high like you would expect a car to, but it would be nice if I could tell the ECU/AT to scoot up to speed at WOT+peak tq.

[Soup DeVille]

Are they not most efficient at maximum torque?

This depends on if you want to define efficiency as:

A: most miles per gallon

B: most power produced vs. the rate of fuel consumption (such as in gallons per minute)

or

C: power produced over time at a given rate of fuel consumption.

All of these will give you different answers.

[Soup DeVille]

Are CVT cars programmed to favor WOT at much higher transmission ratios to keep the engine at peak torque?

My Outback revs the engine high like you would expect a car to, but it would be nice if I could tell the ECU/AT to scoot up to speed at WOT+peak tq.

To an extent, but most CVTs cannot handle peak torque for long stints.

[Laconian]

To an extent, but most CVTs cannot handle peak torque for long stints.

Probably not a problem with my asthmatic N/A 2.5.

[CaminoRacer]

Probably not a problem with my asthmatic N/A 2.5.

Idk plenty of CVTs fail prematurely even behind crappy engines

[Laconian]

Subaru's CVT uses chains, not rubber bands.

[Soup DeVille]

Subaru's CVT uses chains, not rubber bands.

Yes, and it still fails quite often.

[r0tor]

IIRC it's pretty crap. Packaging, smoothness, and volumetric efficiency are their strong suits, but you don't get a Wankel for fuel efficiency...

Actually the 787B won at LeMan because of fuel efficiency... WOT wankels are actually better than a piston engine

[cawimmer430]

IIRC it's pretty crap. Packaging, smoothness, and volumetric efficiency are their strong suits, but you don't get a Wankel for fuel efficiency...

I'm expecting it to be worse than a piston-engined gasoline motor, but I can't find concrete numbers. Some articles mention that the thermal efficiency of the Wankel is "better" than a piston engine because of surface area or something... 

I just want concrete numbers. IIRC currently a modern gasoline can be 35% efficient while the most efficient Diesels are rated at 47%.

[MX793]

I'm expecting it to be worse than a piston-engined gasoline motor, but I can't find concrete numbers. Some articles mention that the thermal efficiency of the Wankel is "better" than a piston engine because of surface area or something... 

I just want concrete numbers. IIRC currently a modern gasoline can be 35% efficient while the most efficient Diesels are rated at 47%.

Wankel is still an Otto cycle, so efficiency will not rival a diesel cycle.  Wankels can theoretically run higher compression ratios than piston engines, which would help them operate at a higher thermal efficiency.  In practice, they generally are about the same as piston engines.

Thermal efficiency is not the same as fuel efficiency.

[SJ_GTI]

[cawimmer430]

Wankel is still an Otto cycle, so efficiency will not rival a diesel cycle.  Wankels can theoretically run higher compression ratios than piston engines, which would help them operate at a higher thermal efficiency.  In practice, they generally are about the same as piston engines.

Thermal efficiency is not the same as fuel efficiency.

Aha, so a Wankel can be more thermally efficient than a gasoline piston engine, but their fuel efficiency is obviously lousier.

[cawimmer430]

Hats off to this Dutch guy for driving around in a 1981 Chevrolet Caprice 350 Diesel! 

www.youtube.com/watch?v=kZIRhsOyhks

[FoMoJo]

Another F40 up in flames...A Ferrari F40 Just Burned to the Ground in Japan

[cawimmer430]

Love how positive this guy is about the Yugo. 

www.youtube.com/watch?v=wDJQoGJFO6Q

[shp4man]

Hats off to this Dutch guy for driving around in a 1981 Chevrolet Caprice 350 Diesel! 

www.youtube.com/watch?v=kZIRhsOyhks

It's literally a miracle that junk even runs. 

[cawimmer430]

It's literally a miracle that junk even runs. 

Maybe European Diesel fuel is better than American Diesel fuel!    j/k

[cawimmer430]

By the way, spotted this today! 1940 model?

Link: https://www.carspin.club/index.php?topic=977.new#new

[shp4man]

By the way, spotted this today! 1940 model?

Link: https://www.carspin.club/index.php?topic=977.new#new

Yep, a 40 Ford. Some say the most beautiful Ford ever made.