Car Chat

[Soup DeVille]

No, no you don't.

[cawimmer430]

No, no you don't.

Did you own one?

[cawimmer430]

Great video from Mr. AMG. The new SL looks seriously promising and the design looks both elegant and muscular. And I bet it will even drive amazing. The last two SL generations have been rather bland, this will surely inject some excitement back into the SL heritage.

www.youtube.com/watch?v=f8jmn68vmDs

[cawimmer430]

Anyone remember the 2015 Mercedes-Benz Concept IAA? This should be the current electric S-Class flagship. Elegant, dynamic, futuristic and sexy.











Instead we get this! This thing egg-shaped thing makes me laugh. 

[AutobahnSHO]

We sold our Subaru last week. Miata is going to sit in garage for a year, wife likes driving odyssey more anyway. Only put on 3k miles in 2 years.

It's been a great car since 2005 but not the best southern car, gas mileage takes a hit for that sweet sweet AWD. It will go to great peeps in NY.

Hopefully the used car mess will lighten up by next year. I hope for a CUV and/or hybrid/EV and/or small pickup to replace it.

[cawimmer430]

Adam Sandler explaining this topic. Interesting.

www.youtube.com/watch?v=_BH-N8t_1Fc

[Soup DeVille]

We sold our Subaru last week. Miata is going to sit in garage for a year, wife likes driving odyssey more anyway. Only put on 3k miles in 2 years.

It's been a great car since 2005 but not the best southern car, gas mileage takes a hit for that sweet sweet AWD. It will go to great peeps in NY.

Hopefully the used car mess will lighten up by next year. I hope for a CUV and/or hybrid/EV and/or small pickup to replace it.

The way prices are now, it might be best to sell the Miata and buy a new one in a year. You'll probably make money   

[SJ_GTI]

Adam Sandler...

[AutobahnSHO]

The way prices are now, it might be best to sell the Miata and buy a new one in a year. You'll probably make money   

Not a bad idea but Scrappy is family :)

Oh and a globe trotter

[Morris Minor]

Walked out to my garage last night. Stood there looking at both cars: the 11-year-old G37 and the eight-month-old CX-5. Despite the latter benefitting from a decade of progress in engine tech & fuel efficiency tweaks, the older car, with the venerable 3.7L V6, gets the same mileage as the modern CX-5 with its 2.5L four. Here, on these lightly-used rural roads, both get about 23 mpg.

The old sedan slips nicely through the air - frontal area & aerodynamics FTW.

[MX793]

Walked out to my garage last night. Stood there looking at both cars: the 11-year-old G37 and the eight-month-old CX-5. Despite the latter benefitting from a decade of progress in engine tech & fuel efficiency tweaks, the older car, with the venerable 3.7L V6, gets the same mileage as the modern CX-5 with its 2.5L four. Here, on these lightly-used rural roads, both get about 23 mpg.

The old sedan slips nicely through the air - frontal area & aerodynamics FTW.

My Rav only gets like 1 mpg better than my Mustang despite having half the displacement and less than half the power/torque.  In pure urban stop/go, the RAV might do a bit better, but on the highway they are about the same, maybe slight edge to the Mustang.

The two actually weigh within about 100 lbs of each other.  Toss in economy-sapping AWD, inefficiencies of a 4AT, and the aerodynamics of a brick, and there you go.

[cawimmer430]

At 150 mph today a Toyota Supra overtook me - great engine sound. That BMW motor at literally full throttle sounds marvelous! 

[AutobahnSHO]

I would like something to pull a camp trailer some day. I was just shocked to see how much an expedition can tow!! Way more than the "medium" pickups....

[MX793]

I would like something to pull a camp trailer some day. I was just shocked to see how much an expedition can tow!! Way more than the "medium" pickups....

It's built on an F-150 chassis, and the F-150 can tow like 10,000 lbs.

[cawimmer430]

Question about thermal efficiency and fuel efficiency of an ICE motor.

Does thermal efficiency actually matter? We know that only 1/3rds of of the fuel injected into a combustion chamber is used to create mechanical energy which actually moves the piston down. Does this influence fuel economy in the slightest? If instead of 1/3rd, the 2/3rds of the fuel-air mixture was put to useful energy, would this mean better fuel economy?

Thanks!

[Soup DeVille]

You'd have to be more specific about what you mean by fuel efficiency. Do you mean L/100kM? Do you mean BSFC (power output per amount of fuel burned).

In general, the two are closely related.

[cawimmer430]

You'd have to be more specific about what you mean by fuel efficiency. Do you mean L/100kM? Do you mean BSFC (power output per amount of fuel burned).

In general, the two are closely related.

I think in Liters per 100 km.

So yeah. Let's assume a gasoline-powered car with a typical ICE (23-30% thermal efficiency) gets 10 L / 100 km on a perfect drive.

If the ICE had a thermal efficiency of 60-70%, would this mean it would need less fuel under the same perfect driving conditions?

[MX793]

I think in Liters per 100 km.

So yeah. Let's assume a gasoline-powered car with a typical ICE (23-30% thermal efficiency) gets 10 L / 100 km on a perfect drive.

If the ICE had a thermal efficiency of 60-70%, would this mean it would need less fuel under the same perfect driving conditions?

Higher TE means less fuel for every horsepower produced.  Fuel economy as far as fuel consumed per distance driven (or vice versa) depends on a host of other factors like aerodynamics, weight, gearing.  Motorcycles, for example, get much better fuel mileage than cars but their engines are no more efficient, thermally.  But, generally speaking, a more efficient engine (unit power per unit fuel) will result in a more efficient vehicle (unit distance per unit fuel).

[Soup DeVille]

I think in Liters per 100 km.

So yeah. Let's assume a gasoline-powered car with a typical ICE (23-30% thermal efficiency) gets 10 L / 100 km on a perfect drive.

If the ICE had a thermal efficiency of 60-70%, would this mean it would need less fuel under the same perfect driving conditions?

Yes.

[GoCougs]

I think in Liters per 100 km.

So yeah. Let's assume a gasoline-powered car with a typical ICE (23-30% thermal efficiency) gets 10 L / 100 km on a perfect drive.

If the ICE had a thermal efficiency of 60-70%, would this mean it would need less fuel under the same perfect driving conditions?

Max theoretical for the Otto cycle is 40-45% (due to pumping losses (moving air through the engine), etc.). Add in practical considerations (i.e., how the spark ICE operates in the real world - valve train losses (compressing valve springs), bearing drag, etc.) and it drops to the max we know today (up to ~30%).

[r0tor]

F1 engine have hit 50% thermal efficiency through all the hybrid energy recovery... Of course they cost more than a house and run on stuff you can't buy.

[MX793]

F1 engine have hit 50% thermal efficiency through all the hybrid energy recovery... Of course they cost more than a house and run on stuff you can't buy.

Hybrid energy recovery is no longer purely Otto cycle.

[r0tor]

Wow... I had no idea

[GoCougs]

Plus, hybrid recovery is a mechanical efficiency bump, not thermal efficiency - i.e., does not affect the cycle itself (compression ratio, pumping losses, etc.).

[CaminoRacer]

I don't want to interrupt this conversation, but I've been browsing the local car ads this morning and it's depressing. Nothing affordable & cool for sale. Only very expensive ($60k+) models or garbage small CUVs for sale. Used cars are 50% higher than they should be.

The market needs their computer chips!

[MX793]

I don't want to interrupt this conversation, but I've been browsing the local car ads this morning and it's depressing. Nothing affordable & cool for sale. Only very expensive ($60k+) models or garbage small CUVs for sale. Used cars are 50% higher than they should be.

The market needs their computer chips!

I've found used car selection around here to suck for a long time.  If you want a CUV/SUV or truck, lots of selection.  Otherwise, anything fun was usually pricier.  WRXs are probably the only fun car you could find used pretty easily (usually modded and abused).  Even boring cars weren't often very cheap given how badly the salt uses up vehicles (it is rare to see anything over 12 years old on the road here).

Now it's the same lousy selection (maybe worse) but at ridiculous prices.

[CaminoRacer]

I saw a Ford Ecosport for $28k. Those things look horrible.

[MX793]

I saw a Ford Ecosport for $28k. Those things look horrible.

If you think they look horrible, drive one.  That's a $14k vehicle at best.  The $20k+ starting price for a base model is insulting.

[CaminoRacer]

Yeah, it looks great for the Brazil market for $14k.

[r0tor]

Plus, hybrid recovery is a mechanical efficiency bump, not thermal efficiency - i.e., does not affect the cycle itself (compression ratio, pumping losses, etc.).

In a hybid F1 engine there is a generator sitting between the hot and cold sides of the turbo that stores excess energy recovered from the exhaust in the battery pack rather than the turbo having a tradition bypass and blow off valve  .  The generator maximizes energy harvested out of the exhaust and minimizes the energy needed for the compressor which is a direct improvement on thermal efficiency.