ken-x8

We have 240V in the US. Standard wiring is 3-phase 240V. 120 across each side for the regular 120V lights and stuff, and 240 across both sides for dryers, stoves, HVAC, etc.

Nice thing about a plug-in electric car is that it's completely clean, as long as you don't live next to the coal fired powerplant or the toxic dump for worn out batteries.

Ken

ASH8

Oh OK Ken, I thought most domestic household stuff is 120V...

Here all homes and small businesses are 220-240V for everything.

Then 3 phase 440V for Heavy Businesses or Machinery..

Yes, I agree about Electric cars, Imagine if everyone started the switch, the Grid would not handle it...

nycgps

iTrader: (1)

Well there are 240v like Ken said, my A/C uses them.

but imagine everybody start using 240v even wire it for 330v like my uncle's factory did ... Do you guys think the power grid here can handle it ? It couldn't even handle normal load without issues. Pathetic

blackenedwings

The Corvette gets its advertised mileage only through turning off half of its engine at low load, if you ever actually drive it and use the accelerator the mileage drops like a stone.

The Miata and the Elise are both INCREDIBLY light cars with very small 4 cylinder engines and low power output. If the new rotary can put out 300 hp and be in a body as light as the Miata I'll take the increased fuel usage for the power and weight distribution.

Honestly I can't speak to the Cayman I don't know enough about it, but the other cars you listed are hardly fair comparisons. Try comparing it to the 370Z or the Hyundai Genesis which have 300 hp 6 cylinder motors which more closely match the output of the proposed 16X rotary. Just because its a 1.3L motor does not mean it is a 4-cylinder. RIWWP is bang on with that.

paulmasoner

iTrader: (1)

holy crap kersh!!! i didnt know anyone god that bad anymore unless they were BONE STOCK... hell, all i have that matters is Ray's coils, no cat, and MM's AP tune and i see like 24-25hwy

I'm keeping fingers crossed that over the next few years i'll squeeze another mile or two out of it... loosing rotating mass in the fly/clutch/wheels area

blackenedwings

I got ~27 mpg 100% highway when I was commuting to Reston VA for a week when I was NA. Now... my mileage isn't the best, but I <3 boost.

paulmasoner

iTrader: (1)

hehe i bet you do

i've never recorded a 100% hwy test to see. hell the only time i ever emptied a tank ALL hwy was drving the car to Atlanta to have it shipped out here to Belgium.

If it makes any guesses though, my parents followed me to drop off. 2008 Accord with 18.5 gal capacity. RX-8 15.9 gal capacity. Both started the trip by filling up - parents record mileage religiously, they were on fumes when we stopped for fuel. They got their typical 26.x mpg - I was still near 1/4 tank..... whatever that roughly equates to

ken-x8

Most domestic stuff here is 120...which tends to be referred to as 110 or 115. Japan is the same. But 240 3-phase service has been standard in the US for probably 50 years. The full 240 tends to be used for the heavy stuff. And they learned to split down to 120 at the breaker panel, not run 240 to a kitchen duplex outlet and split it there.

For some reason I never understood, HVAC in commercial buildings is often 277 volts.

At least they did away with DC for everything except electric railroads.

Ken

kersh4w

iTrader: (3)

someone said try comparing it to other sports cars, i did. other sports cars seem to manage. and the C5 corvette gets 29mpg, and that was before cylinder deactivation technology came into play. its simply a low slung car, not a lot of drag. and it has gobs of torque. it can cruise at 1500-1700rpms at highway speeds.

and you cant compare it to the 370z or the genesis coupe because, while the mpg is the same, the hp numbers are vaaaasstttlllyy diffferent. we need aftermarket turbos to just get to their hp ranges.

changing to the cobbs economy map doesnt seem to really do anything, so i run the cobb stage 1. i have the bhr flywheel and an act hd pp and 4 puck clutch. took quite a few lbs off everything. not a bit of difference. best mpg i ever got, strictly highway, 24.5mpg. i had to travel 65mph in the right lane. i usually do 80-90mph on the highway. 4500-5000rpm is a big difference from 1700rpm on an LS v8.

TeamRX8

iTrader: (25)

Some of the people responding here aren't firing on all their cylinders either

kersh4w

iTrader: (3)

ZumnRx8

llolll team rx8

Rote8

They need the Porsche variable vane turbocharger and add about 20 psi stock to the 16X.....

tmak26b

[QUOTE=blackenedwings;3293770]The Corvette gets its advertised mileage only through turning off half of its engine at low load, if you ever actually drive it and use the accelerator the mileage drops like a stone./QUOTE]

Ahh..no. My Corvette ran on all 8 cylinder cruising on the highway, it made more torque at 2300RPM than my RX-8 at 5500RPM. Even if i beat on it, the mileage is only slightly worse than the RX-8.

shazy

How much does it make at 1k rpm?

TeamRX8

iTrader: (25)

Enough to idle off the line in 2nd gear easier than an RX-8 does in 1st with throttle

blackenedwings

The nature of how a rotary works will always require more fuel than a piston motor as more fuel has to be injected to ensure enough fuel is present to ignite properly due to the shape of the combustion area. That being said I've seen 27 mpg on my NA RX-8 on stock plugs on a highway only cruise. So sure I believe a C5 made 29 mpg at 1500 rpms at ~65 mph. However, I don't believe for a minute that a C5 being hammered on got anywhere near 18 mpg. I've had a small block Corvette and a LT1 Z28 (the iron block Corvette motor prior to the LS1 in the C5) and both drank fuel ridiculously. The RX-8 is thirsty in boost, but naturally aspirated I spent much less in fuel than my Z28 which I drove like a grandma for the last couple of years before I sold it.

Also for whoever said we need aftermarket turbo kits to hit the stock power levels for a 350Z... most of that is due to getting almost no benefit from naturally aspirated modifications. With an aftermarket turbo kit the RX-8 is easily capable of over 100 hp more than those cars stock power while losing nothing of it's handling capability. As an example, I just drove my friend's brand new 2009 STi the other day for a while, and I would bet money I could thrash that car on the street.

RIWWP

iTrader: (2)

So I am going to summarize the MPG debate included in this thread so far:

- The RX-8 is deemed to have horrible gas mileage, in the 18-22mpg range.
- The RX-8 has been shown to have better than 22mpg highway by several owners, with 27mpg the highest reported yet
- The RX-8 has also been shown to have significantly worse mileage by several other owners.

- Other cars with lots of power and lots of low end torque can cruise at 1/3rd or less of the RPMs we do
- Other cars with lots of power and lots of low end torque can post slightly better MPG if they stay in high gear lugging it with their torque, having similar weights, better power to weight ratio.

- The RX-8 doesn't have that torque, so much sit higher in the RPM range, about 3 times higher, but does not have 3 times the fuel consumption

- We also know that the ability to make power is directly proportional to the amount of air you flow.
- We also know that the 'best' A/F ratio is around 12.5
- Therefore the amount of power is also directly related to the amount of fuel you flow.
- That means that more power WILL equal higher fuel consumption. Not exact % changes, due to how efficiently your engine uses the fuel, but generally, true.
- Piston engines with today's technology are thermodynamically more efficient than rotary engines. (I believe I saw ~85% vs ~70% quoted somewhere)



So basically, the complaints are:
1: When I am not on the gas, the MPG is only slightly worse than cars with a significantly better power to weight ratio
2: When I am on the gas, the MPG drops like a rock
3: My 8's engine isn't in perfect health.

#2 is true of all cars. Period. No one has really mentioned power-on MPG for these other cars that they think we should be as good as, because their MPG drops to single digits also.

#3 is partly the responsibility of the owner (ignition health), partly the fault of Mazda's inadequate lubrication and cooling design (compression health), which is an acknowledged and accepted by the community, and we hope that Mazda won't repeat for future rotarys. So #3 is a non-issue for the future, as long as the owner takes care of their car.

#1 is the single best answer. Drop weight so our power to weight improves. Even with identical gearing, it will require less throttle input to keep cruising speeds, although a redesign could also change the 6th gear so that our 6th gear cruise RPM at highway speed is ~2,000 or 2,500. Entirely possible if we shave 400-600lbs off the car. This will also greatly improve one of the other complaints, straight line acceleration. As well as another high point we have, handling.


So do you see why I consider the MPG complaints as baseless and not worth our time? MPG itself is still something to watch, because it is an indicator of the health of the engine, but we hardly have crappy mileage, even given the circumstances. If you do, well, I suggest you get your ignition and compression looked at.


A RX-8 with a healthy engine still makes better MPG, with complaints, than a fair number of commuter cars our there, without complaints. The outside world has to be thinking 1.3L 3cyl or 4cyl, and comparing our engine to that of the Honda Fit, the Honda Insight, the Smart ForTwo, Motorcycles, etc...

tmak26b

I have owned the following car

04 350z 287HP City: 19mpg Hwy:28mpg Track: 7.5mpg
05 400HP C6 City: 16.5mpg Hwy:26mpg Track:7mpg
06 232HP (Mazda HP, so subtract another 20HP) RX-8 City: 17mpg Hwy:21.5mpg Track: 9mpg

RIWWP

iTrader: (2)

So you are comparable for city, significantly better (+20-28%) for track. 18-24% worse on highway (still better than a PT Cruiser), due to having to run at a higher RPM than the other 2 cars, since the other 2 have the torque to lug them around.

I don't get the "my mileage is worse than cars with more power" complaint, because it is fairly cut-and-dried WHY.

Thanks for the info, I can see why anyone would choose MPG as their choice of sports car. The RX-8 clearly pwns with mileage on the track.

BReal-10EC

I've always wondered if they could create and Atkinson Wankel engine. But you need forced induction to make the Atkinson effective (think Miller Cycle Millenia). Basically- the Atkinson design requires the expansion stroke to be longer than the compressions stroke. This is done on Otto cycle piston engines by leaving he intake valves open during the first part of the compression stroke. So it's theoretically possible to gain some efficiency with that same principle applied to the Wankel, but then forced induction is needed to offset the n/a power lost.

madcows

While I don't have exact numbers, I would say the overall gas mileage I get out of my 8 is comparable to my leased '07 impreza 2.5, which I have to hammer on in order to go nowhere fast. Even a prius can be made to get relatively poor gas mileage (<18mpg), as Top Gear has previously demonstrated.


I do however think that there is still hope for the rotary, and that a series hybrid is part of the solution - as long as battery/capacitor size is minimal. So, what's the other part of the solution? Ever heard of "Turbo compound" engines? No, I'm not talking about equipping the rotary with a turbo, and a supercharger. I'm talking about a large turbine on the exhaust where the shaft rotation is used to help rotate the crank. This technology was initially used during WW2 on aircraft engines which not only helped increase the power by a substantial amount, but it did so at the expense of practically NO ADDITIONAL FUEL!

Just to give you a brief idea of what this setup achieved, take the Curtiss-Wright R3350-TC radial engine. In non-turbo compound form, it produced 2,700HP, but by reclaiming what would be wasted energy leaving out through the exhaust utilizing turbo-compounding, the engine put out 3,500HP! When all was said and done, both versions put out about 1HP/LB, but used roughly the same amount of fuel.... for an extra 800HP!!

Power gains using turbo-compounding in a rotary would be proportionally better than what could be achieved in a piston engine, and Paul Lamar explains why:

(There's a lot to read, so sit down and enjoy!)
http://www.rotaryeng.net/sum-turbo-comp.html
http://www.rotaryeng.net/turbo-compound.html


If you already know about turbo compounding, or you read through those pages a bit, you would see the main drawback of such a setup is the need for a limited RPM range, and *that* is why it would be PERFECT for series hybrid duties.

Symbioticgenius

Kersh, I usually learn so much from you, so I'll be gentle.

1. You compared 8 Mileage to a C5 vette which makes 335 or 350 HP, and laid out valid reasons why it gets better mileage, yet didn't compare to a 350 or Genesis, cause "the hp numbers are vaaaasstttlllyy diffferent" Interesting.

2. you then stated that when you drove the speed limit (which is the EPA test speed) and got the EPA Rated Mileage... (gratz BTW... your engine is healthy) . but then showed the reason for your bad gas mileage (18 from earlier posts) was due to you usually driving between 80-90.

I'm sure you already know where I'm going with this, but allow me to point out to everyone else here, that the speed at which you travel GREATLY affects your MPG.
I got a 4 banger in which I can count on for 18-21 MPG combined because in the city im doing 45 Stop and go, and highway a constant 70-80, with spurts of 120 every so often.

As RIWWP stated, MPG is a great indicator of Engine health, but overall MPG is more affected by the driver than the engine.

alz0rz

iTrader: (41)

mpg can't be correlated to engine health, unless you're just pumping gasoline out of the exhaust.

olddragger

iTrader: (3)

physics do not lie:
1/2 lb of fuel per hour per hp. firgue everything from there/
how many hp does it take to accelerate the car--to maintain the 70mph interstate speed etc.
there you have it
yes efficently does play a small affect.
OD