I don’t have a horse in this race, but given the absurdly high RPMs required to extract horsepower from the S2000 engine, I wouldn’t be surprised if it burned fuel like crazy when driven hard.
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The Honda meets the same regs.
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What you just said proves my point exactly - with the right gearing, a big engine is just as efficient as a little one. The only difference is that with a smaller engine, you CAN’T do what the corvette does because there isn’t enough torque.
No, I’m telling you that when driven the SAME way, the big engine does get better fuel economy, and the EPA figures prove it. Whether Corvettes and Hondas are driven the SAME way in the real world is another question entirely.
I purposely chose the S2000 because it’s also a sports car and is set up with performance oriented gearing, cams etc. Of course in terms of performance and power it doesn’t hold a candle to the Vette. Comparing it to a Honda Civic would be pointless, since the Civic is not physically capable of performing like a sports car.
Do you remember the Top Gear episode where Jeremy Clarkson ran the Vette from 0-100 entirely in 5th gear(or something like that)? The big V8 engine has so much torque on tap that you can happily do that all day, and get great fuel economy, if you don’t mind economy car-like performance. You don’t have a choice with the Honda.
See cite above. What you are actually seeing is correlation, not causation - Most vehicles with big engines are either sports cars or large, heavy utility vehicles/trucks. These vehicles generally are less fuel efficient, but that isn’t because of the displacement of the engine.
Since we’re on the topic of RX-7s, one of the most popular aftermarket “modifications” to the RX-7 is to simply remove the factory rotary engine and turbo setup entirely and replace it with a store-bought GM or Ford V8. Here is one of the bigger outfits specializing in this. The weight and balance of the car remains almost unchanged, power and torque are increased significantly, and fuel economy and reliability are both much improved. This is additionally attractive due to the low cost and relative abundance of used RX-7s with non-functioning rotary engines.
Didn’t see this one. I’ve taken the seats apart on my Benz and you are completely incorrect.
I’m gonna back Throatwarbler up and say that the displacement is almost irrelevant. What matters is how much mass you’re moving, and how quickly you do it. Given a car of the same weight, a 6.2L V8 and a 2.2L I4 will burn almost the same amount of fuel if driven at the same speeds with the same coefficient of drag, intake and combustion chamber design notwithstanding. Granted, the 'vette will likely burn a lot more gas because it can go faster, but as the proud owner of a high revving honda, I can say that fuel economy is not its strong point when you drive it like it ought to be driven.
As a fun little game, you can go out to edmunds and start comparing EPA ratings for the same car with differently sized engines. I don’t have a whole lot of time to do it, but the base model 2008 accord weighs in at 32xx lbs, has a 2.4L 4 cyl, and gets 21/31. The 3.5L V6 weighs 35xx and gets 19/29. What do you think is a bigger factor there – the 1.1L of displacement and extra 2 slugs, or the extra 300 lbs that the V6 necessitates carrying around? I think if you were to compile the data and do the math, it would back up the hypothesis that smaller displacement engines get better mileage only because they weigh less.
Well you need to get with it. Buy a new one. 
http://www.mercedestechstore.com/pdfs/507%20Systems%20I/507%20HO%20SRS%20(GC%20ICC)%2010-30-02.pdf
I hope that link works.
Well, I wouldn’t really call that an “Engine”, but OK, fair enough. 
(Mine was the “Original cable” type)
While the system uses a wankel type rotor, to call it an engine is stretching the definition of what most people consider an engine.
[side comment] man what a strange way to design a pre-tensioner. Like we used to say, Mercedes Benz over-engineered like no other car in the world.[/sc]
I’m not so sure, because
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Smaller displacement on the SAME engine actually means LESS weight. The 7.0l Corvette engine weights about 30lbs less than the 5.7l Corvette engine, because the engine block is the same, except the 5.7L has an extra 1.3ls of metal.
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Even physically smaller engines don’t always weigh less. If you look at that Hinson site, you can see that the aluminum 5.7L Corvette engine (LS1) weights LESS than the 4 Cylinder Nissan KA series engine, since the Nissan is made of cast iron. The owner of the BMW Tuner shop here in Calgary drives an E36 (1991-99, I think?) BMW M3, with the old iron BMW I6 engine replaced with an aluminum Corvette engine - same result. The Corvette engine weighs less, sits lower in the engine bay and further back from the front axles, thus improving handling, and gets better fuel economy. All the extra horsepower is just gravy.
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All things considered, the difference in engine weights is pretty minor compared to the weight of the whole vehicle, even taking into consideration the heavier, beefier transmission and drivetrain in a higher powered car.
Then what exactly is the point of variable displacement engines?
And why does a Prius get better highway mileage than the Corolla? The way I understood it, hybrid cars don’t use the electric motor during sustained highway driving, and the only reason they get good highway mileage is because they have smaller engines than comparable size non-hybrid cars.
The point of variable displacement engines is to create a very minor increase in fuel economy.
They do help. Now, how much do they help?
The best way to get good gas mileage is to never use the brakes.
The second-best way to get good gas mileage in town is to have a light car.
The second-best way to get good highway gas mileage is to have a car with little wind resistance.
Its amazing that MAZDA poured so much money into the Wankel engine-given that GM, M-B, ans AUDI decided to drop the effort. I wonder if a steam engine based on a wankel would work? I did drive an RX-7 once-it really flew-and the turbine like feel (and lack of vibration) was amazing. Incidentally, a few years ago, automakers were looking at the two-stroke engine for cars-what became of that?
A few things:
-Mazda makes ( or until recently made…not sure) a Japan-only luxury car called a Cosmo that uses a dual rotor, dual turbo induced Wankle. They are available in the US as “Japanese take out” motors.
-In addition to the already mentioned O&S model airplane engine, there is a german built Wankle go-cart engine that is currently making big waves in that sport.
-Big gasoline engines suffer from excessive pumping losses when operated at light load. The 'vette avoids this by using tall gearing that keeps the engine loaded, albeit at low rpm.
-Both Wankle and reciprocating engines are examples of Otto-cycle engines. The fact that a Wankle uses different areas of the epitrichoid housing for intake, compression, expansion, and exhaust notwithstanding.
To add a little more to that, the Cosmo is actually available with the 2.0l 20B triple rotor engine, in the highest trim level. Both the 20B and 13B used in the RX7 used the same sequential twin turbo system.
That’s all true, I should have said something along the lines of “if a smaller engined car does get better gas mileage, it can more easily be explained by the decreased weight of the drivetrain than the decrease in raw displacement.” It just seems that people are so used to saying “I got the smaller engine (I4 vs V6, V6 vs V8, etc) in my vehicle because it gets better gas mileage,” that they lose sight of WHY that’s true.
Incidentally, your point about bigger engines not always being heavier is very true, which is why a corvette doesn’t weigh a whole lot more than an s2k. My limited experience has shown that a little bit of extra engine weight tends to cascade, as 50 more lbs for a V6 turns into an extra 75lbs in the beefier transmission, + heavier axles, +heavier subframe, and all that extra weight means bigger, heavier front brakes, which means bigger, heavier wheels, etc etc.
That’s absolutely not true. As I say, I ran one for three years, bought new in 2004 (only 5 or 6 months after they came out in the UK) and never had any reliability problems whatsoever. I never had to “hold it at 3000rpm” before shutting it down. The only precaution I was told to take was not to start the engine and then shut it down again without letting it run long enough for the idle speed to drop down to normal (say 2-3 mins). I forgot about this a few times but never had any problem, but I was told it could lead to the engine flooding. Also the oil use was not nearly as high as you say. I checked the level after every two or three tanks of petrol and it rarely needed topping up. I’d put in a litre about every 2000 or 3000 miles or so.
I certainly have no arguments there! I would get about 18-19mpg (and these are UK gallons!) on short journeys. From a 61 litre tank the longest I ever got, on a motorway journey, was 305 miles!
Also agree. It handled like a dream and was very fun to drive. I miss it.
I was curious about this too, but it most definitely is an engine. It converts the energy from the combustion of a chemical fuel into a mechanical force. Where it differs from what most would consider an engine is the number of cycles it is designed for. It’s pretty clever how the second and third cycles are ignited.
[OT]
Looking through that pdf, I see that the crash sensor control module on my 1992 W124 is made by Becker. I hope that they did a better job on that then the pile of junk that they call a stereo in that car.
Yes, but I bet it would be horribly inefficient if you try to extract only 30 horsepower out of it.
The issue is displacement vs. efficiency for a given power output. A typical car needs maybe 60 horsepower to maintain 70 mph*. So, if you compare a 5-liter engine vs. 1-liter engine while each one is producing 60 horsepower, what are their efficiencies?
- A guesstimate based on the fact that my car, a 4-door sedan, has a 70-horsepower engine and can get up to 75 mph or so.
Agreed - IC engines are likely to show best efficiency only in a rather narrow range of power output. The “big engines are inefficient” notion comes from using automobile engines that are substantially larger than they really need to be.