sonoronos

Understanding the Renesis

Renesis Displacement: 1.3L
Renesis Horsepower: 238 SAE HP
Renesis Torque: 159 SAE ft/lbs
Combined Gas Mileage: 21mpg
Renesis Horsepower/Liter: 183.0
Renesis HP/L/MPG: 8.72
Curb weight: 3029 lbs
Base MSRP: $25,180

Honda S2000:

S2000 Displacement: 2.0L
S2000 Horsepower: 240 SAE HP
S2000 Torque: 153 SAE ft/lbs
Combined Gas Mileage: 23mpg
S2000 Horsepower/Liter: 120
S2000 HP/L/MPG: 5.22
Curb weight: 2809 lbs
Base MSRP: $32,400

Nissan 350Z:
350Z Displacement: 3.5L
350Z Horsepower: 287 SAE HP
350Z Torque: 274 SAE ft/lbs
Combined Gas Mileage: 23mpg
350Z Horsepower/Liter: 82
350Z MPG/Liter: 3.57
Curb weight: 3210 lbs
Base MSRP: $24,158

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So what do these numbers mean? The RX-8 has 153% better volumetric efficiency compared to the S2000. Its volumetric efficiency is 223% better than the 350Z.

The 350Z has 244.25% better heat efficiency than the RX-8. The S2000 has 167% better heat efficiency compared to the RX-8.

So basically, your RX-8, mathematically speaking is about 91.3% less efficient overall compared to the 350Z, and about 91.6% less efficient overall compared to the S2000 in terms of volumetric and heat efficiency. Compared to the old 13B and 20B engines, that's a serious improvement.

Realistically speaking, you're driving a bigger, better looking, 4-seat equivalent of an S2000 that cost $7000.00 less than the real thing.

Bottom Line: We already knew the 350Z rules the road, but the RX-8 comes out tops as far as sportiness + practicality, and your friends can't argue that your rotary engine is junk anymore.

Don't hate...appreciate.

mikeb

what do you drive

turbojeff

You don't know what volumetric efficiency is do you? It is how much air fills the combustion chamber as a percentage of it's capacity. In a perfect world any NA motor would have 100%, a turbo motor running 1 atm boost would have 200%. Get it?

Another thing your not looking at is torque. The 350Z will do a "street start" 5-60 mph much quicker than an 8. You've got to rev the 8 to get it to move. In the real world it really shows up in traffic.

You also noticed that the 350Z gets better mpg than the 8. Hmm, more hp, less gas and your bragging about volumetric efficiency, even though you don't know what it means.

klegg

uhhhhh, I am confused. Is this a positive or negative post?

Shocka

but the real questiong if u put those 3 on a line and make a girl pick one which will they pick?

if i wanted power i wuda had the Evo.. like ive mentioned a million times before i even had a down on the Evo, but walked next door to Mazda and loved the styling and handling of the RX8 so i got it...

and i cant complain LOVE IT!

on a related note i did run a S2000 today and beat her.. yes her so i still looked like an idiot she was hot to..

mikeb

nothing better than a hot girl in a hot car

WTF no turbo

Change starting price on 8 to 25 is for auto and 197hp.

OdinGuru

While this seems accurate at first glance, the 1.3L displacement of the rotary can not be directly compared with the displacement of cylinder engines. In order to correctly compare efficiencies you need to use a cylinder engine equivelent displacement of 2.6L. The equivilent displacement is twice as big because a rotary has one combustion event per rotor per output shaft turn vs. one combustion event per cylinder for every two output turns for 4-stroke cylinder engines. So the rotary moves twice as much fuel/air per rev then its displacment implies. This also expalins why the International Engine of the Year award for the Rensis had it in the 2.6L catagory. Using this adjusted displacement yeilds much more understandable results:

Renesis Displacement: 1.3L
Renesis Cylinder Equivilent Displacement: 2.6L
Renesis Horsepower: 238 SAE HP
Renesis Torque: 159 SAE ft/lbs
Combined Gas Mileage: 21mpg
Renesis Horsepower/Liter: 91.5
Renesis HP/L/MPG: 4.36
Curb weight: 3029 lbs
Base MSRP: $25,180

Now we see that the Rensis is making a very solid 91.5 HP/L
While this is not quite the level of tune seen in the S2000, it is better than a large majority of NA production cars (like the 350Z).

The lower mpg rating for the RX-8 is inherent in the rotary design. Due to the much larger surface area of the compustion chamber, more heat from combustion is lost into the block than in a minimal surface area cylinder (as opposed to heat converted into mechanical force).

While the rotary design will never beat the best cylinder engines for fuel consumption or HP/L, its best atribute is making substantial amounts of power from a light/small engine.

Another interesting fact is that the Rensis LOVES to breate. At redline, each of these cars sweeps out its peak displaced volume per second:

RX-8:
195 L/sec @ 9000 rpm

S2000:
150 L/sec @ 9000 rpm

350Z:
192.5 L/sec @ 6600 rpm


Notice that the RX-8 sweeps out slightly more displaced volume per second at redline than even the much larger displacement 350Z. This further illustrates the reduced fuel efficiency of a rotary design as the amount of fuel consumed is directly proportional to the amount of air displaced. So in other words, the RX-8 consumes slightly more fuel then then 350Z, but generates power from that fuel more like the S2000. This is also why rotaryies are breathing resricted, not strength (rev) restricted like cylinder engines.

But while thermal efficiency is not particularly high, power / weight is quite high, and the engine produces wide output power pulses that are more like a 6 cylinder than a four cylinder. I can only immagine how smooth a 3 rotor would be.

Thoughts and feedback are appreciated.

- David

Ike

Call me crazy but isn't the base price of the 238hp model over 27K?

Ike

manbar

Uhmmm, the 238 hp version cost 27,200M plus rumors has it that mazda is jacking up the price (29,500ish)

manbar

and the 350z price should be higher than what u posted

Blue 350z

Just an FYI: The MSRP for a base model 350z is $26,370

Sneakyracer

RX8 have 215 real flywheel HP not 238hp (mazdas still overrating)

chinx

350z does NOT "rule the road"

ie, a properly maintained '93 FD3S R1 will outrun it outright, and then ditch the heck out of it come the next corner