Non-hybrid IC engines really need to be sized for merging on to a busy, yet quick flowing freeway without getting yourself rear-ended, bucking a strong headwind, or climbing a steep grade at a non-obstructing pace. And yes, this makes them considerably oversized for level cruise conditions with no headwind.
If all cars had the power/weight ratio of a loaded 18 wheeler, then they would all cause the same traffic disruption that occurs when one of those behemoths is trying to merge onto the freeway, or lumbering it’s way over a mountain pass.
I’ve never seen the movie. Twenty years ago, a friend of mine had an RX7. I was fascinated by the engine. I’m not into cars so I would have no idea about an RX8.
So all car engines are operating at below optimal power most of the time. Doesn’t that mean for almost every car, increasing the engine displacement would make the engine even more overpowered, and therefore less efficient?
Cars have brakes, they are perfectly capable of slowing down to allow even the most underpowered truck to merge onto the freeway. If you really don’t like that, you can avoid the right-most lane except when necessary.
I don’t believe this is true. If you look at the mpg figures for a model available with several engine choices, the smaller engine almost without exception gives better feul economy.
2007 Mazda MAZDA6 i 5-Door Touring 2.3L 156 hp I4 FWD 24/31 - 32
2007 Mazda MAZDA6 s 5-Door Value Edition 3.0L 212 hp V6 FWD 19 - 20/27
2007 Audi A3 2.0 T DSG 2.0L 200 hp I4 FWD 25/32
2007 Audi A3 3.2 DSG 3.2L 250 hp V6 FWD 21/27
2007 Dodge Caliber Sport Appearance 1.8L 148 hp I4 FWD 26 - 27/30 - 32
2007 Dodge Caliber R/T FWD 2.4L 172 hp I4 FWD 23/26
I think scr4 is correct in pointing out that engines are not efffeciant when making much less than their max hp. If our goal were only efficiency, why have 8 sets of pistons and rods, and all necessary valving and such, when 4 would create enough power to move down the road?
Those numbers prove nothing unless you also include vehicle weight with fluids in place as well as tire sizes and final drive ratio. A sub-optimal gearing choice can cause a 15% gas mileage hit all by itself.
On my car the base engine gets the ‘efficient’ final drive ratio while the upgraded engine gets the ‘sporty’ final drive ratio.
Also, in most vehicles the big engines get added to the loaded models, not the stripped ones.
Also, in the case of the Audi, you are comparing a 2.0 l turbocharged engine with a naturally aspirated VR6.
Maybe I was using a poor choice of words. My contention is that as far as the amount of fuel used to move a particular vehicle a certain distance is concerned, the displacement of the internal combustion engine used isn’t really indicative of anything. You can use a big engine that will do it in fewer cycles, or a little engine that will do it in more cycles, the amount of work going through the transmission is the same, and if the transmission efficiently moves the power to the wheels, there will be little difference between the two.
You are correct in that car models with larger, more powerful engines typically use more fuel in tests such as those you cite, but as others have pointed out, the discrepancy is due to factors other than the engine displacement. How much fuel is consumed by a vehicle, I would say, is 80% dependent on the driving style, and 20% dependent on the gearing.
I think this mod is pretty much the antithesis of a “popular” modification, since you will get neverending crap from FD purists about it.
And I will echo the poor gas mileage, although 20 mpg for a 12 second car is not actually THAT bad. Defintely not as good as the 30 mpg I get out of my S2000…
Well that opens up a whole new can of worms, but I think it also proves my point. Why bother with an expensive turbo? Because it allows you to use a smaller, more efficiant motor for cruising, yet provides the power consumers want for passing and merging.
The auto makers test their cars in absolute best possible scenarios. I don’t believe for a minute that these numbers are caused by the tester having a lead foot.
Most sanctioning bodies count it as a 2.6, since it’s more similar to a 2-stroke. Others will specify rotaries specifically in the classes where they need to be.
Yep, can confirm that the UK DVLA classed it as a 2.6-litre. Not that that affects the tax band any more, as that’s now calculated on CO[sub]2[/sub] emissions, which for the RX-8 are predictably enormous.
At least one model-aircraft engine maker advertises a Wankel engine for sale (in addition to a flat four and a radial five. There’s some serious esoterical out there). I’ve no idea how many units they shift.
