For those of you who are in to tuning, modifying, basicall know a lot about the mechanics of a car and especially the rotary - what can be modified (if possible) to get better mileage from the RX-8? I intend to purchase this car, but the gas mileage is a concern to me on top of having to pay for premium fuel. Some of you might say that if I am buying this car (over an Acura TSX and especially over the great engined crappy interiored G35) that I shouldn't concern myself with gas mileage. Currently I drive a 2000 protege ES (26 city miles).

 

The weight of your right foot. :p

 

WELP... 1ST OF ALL DON'T DRIVE LIKE YER 16. RUN ROYAL PURPLE 10-30W.

MY 8 IS WITH K&N ENGINEERING FOR THE WEEK BEING FITTED FOR AN INTAKE KIT WHICH WILL PROLLY TAKE 4-5MONTHS TO DEVELOPE. BUT A PERFORMANCE KIT LIKE THAT WILL HELP GREATLY.

 

Really ?? can you explain to me how exactly does it do that ? I'm curious to know, thanks !

 

3 WORDS... INCREASES AIR FLOW

 

Compared to your current car, there is no way to compete with that MPG on an RX but again look at the car type.

The MIllennia S I owned before got around 17-18 in town and 24-26 on the highway. It was rated 20/28 and used Premium gas. Could've purchased an Accord EX V-6 for a little less money and gotten better mileage AND cheaper insurance but the Millennia's looks won me over wayyyy more stylish.

In this case you have to compare cars in the same class - economy, luxury, sport, truck, suv, etc.

If you want mileage, go with an Insight. It all comes down to compromises and no vehicle completely satisfies all categories.

Oh, and as far as K & N. I cannot comment on auto application performance change but I can tell you that on Jet Skis the K & N air filters make a MAJOR difference - 2 mph gain on both of mine according to their speedos.

Question - How does the RX take to the K & N? Does its computer compensate for the increase in air?

 

DUNNO YET, ITS WITH K&N ENGINEERING FOR THE WEEK BEING FITTED FOR AN INTAKE KIT WHICH WILL PROLLY TAKE 4-5 MONTHS TO DEVELOP.

JUST TAKE A LOOK AT WHAT THEY'VE DONE WITH EVERY OTHER INTAKE SYSTEM THEY'VE LAID THEIR HANDS ON THOU.

 

RX please turn off the caps lock, it's common Net etiquette, thank you. Caps are considered yelling or shouting.

 

it has an airflow meter, so the ecu/ecm/computer knows how much air is going into the engine and can compensate* thusly.

mike

*up to a point. the sensors are calibrated to flow x amount of air at full voltage. they either run a 0-5v or 5-0v signal, if you exceed that airflow/voltage the ecu cant see it

 

I agree, I keep forgetting to mention that everytime I see one of his posts. If you want to stand out keep the color but please lose the CAPS.

 

...that's not going to help your mpg.

...not to mention, i'll be extremely interested to see what K&N think they can do to enhance performance on the "in" side of things... and if it works they're just the same as any other tube+cone system.

 

I replaced the factory intake on my '93 3000gt withthe K&N FIPK and definitley saw an increase in mpg-- went from 21mpg to almost 25-- way more than i expected. it also felt like the throttle response was better but that could be my imagination. those 3mpg really add up too as I drive 400-500 miles perweek and the 3kgt requires premium just like the rx-8. as long as the mpg numbers are similiar to my gt i will be happy as both cars are 4sp AT's with very similiar hp/lb ratios.


only thing I won't like is going from a 20 gal tank to a 16 gal tank -- a pit stop every 5 days instead of once a week

 

Changing the volumetric efficiency of an engine by making it breathe better will typically give you better power, and most times better fuel economy.

The intake of the RX-8 *will* be improved upon by someone. Car makers do have to compromise on intake designs to keep down induction noise - Mazda's design is not the end-all, be-all of intakes. Actually, I'm surprised they did as good as they did with the '8s airbox - all the RX-7 airboxes were god-awful.

*EVERY* RX-7 I've ever put a cone intake on from the stock airbox had a DRAMATIC improvement in power, especially on the top end of the powerband.

Back to the original point - there isn't a whole lot you can do to improve fuel economy. CDI boxes, like the Crane HI-6 and the MSD 6A, can and do help fuel economy, but the knowledge base on the RX-8 really isn't up to installing one of those - heck, we don't even have access to a shop manual yet . These boxes increase spark energy and create multiple sparks, which does help out.

Big thing is just your driving habits - when cruising, try to stay just over 2000 RPM and keep your foot out of it. But, it's so much fun to stamp on the loud pedal, you may not be able to .

Rotaries are just thirsty engines by nature, and you're not going to get the insane gas mileage that a 4-cylinder will get. If it truly concerns you, add up how many miles you drive a month, and figure your monthly gas expense. Then, equate that to the RX-8's fuel economy and premium fuel, and see what the difference is.

My '88 Turbo (VERY modified) drinks premium and gets 10-12 MPG because I can't keep my foot out of it. Mind, it's got firehoses for fuel injectors and makes somewhere north of 350hp . But, I smile every time I gas it up.

Dale

 

...if by "improve" you mean "create a different comprimise" then yeah, there will be someone who optimises the intake paths to work better +8000rpm for more power, but no one is going to engineer something that helps the engine from the 800-2500 rpm range.

 

I'm not sure if putting a performance intake system will help with mpg. You would end up pushing the loud pedal more thus negating any mileage saved.
It still boils down to your diving behaviour. Don't rev too high. Change to lower gears at 3000rpm. Oops! wait, there's nothing below 5000rpm. :D
Seriously rotaries aren't known for gas savings. Eventhough this renesis engine is marginally better than the previous rotories, it's still a gas guzzler. Perhaps a 4 cylinder Mazda6 might be better for your needs?

 

YEA, BEHAVE WHILE YER DIVING.:D

YEA WAKEECH, I'M SURE K&N TECHS ARE SCREAMING "SUCK BABY SUCK!"

P.S. VO-BRO-MAN
IT IS LIKE I'M YELLING, I KNOW, BUT SINCE I GOT MY 8 I HAVEN'T BEEN ABLE TO AFFORD A NEW KEYBOARD.(CAP LOX R STUCK )

 

no way on the Mazda 6. It's a nice car and all, but the cool factor of the RX-8 plus the driving feel - simply awesome. These outway gas mileage issue.

This will be the most expensive car I've owned (I've only purchased one - a 2000 protege ES). I just have to adjust to paying more for gas and getting worse gas mileage to have this car. I wonder what the mileage will be like driving around in metropolitan Los Angeles - that's where I'll be doing most of my revving.

 

RX-EVolved - try pulling the CAPS Lock key off the board, clearing out the chips and crumbs in your keyboard, then see if it works.

As for me I'm mostly doing city drving and getting 15-16 mpg. I've decided to use regular unleaded w/an occasional premium tank. The manual and other posts say its okay and should help me save a few $'s.

 

The MANUAL says it's OK???

 

Thought you'd guys would want to read this:

http://travel.howstuffworks.com/rotary-engine5.htm

Slower
Since the rotors spin at one-third the speed of the output shaft, the main moving parts of the engine move slower than the parts in a piston engine. This also helps with reliability.

Challenges
There are some challenges in designing a rotary engine:

* Typically, it is more difficult (but not impossible) to make a rotary engine meet U.S. emissions regulations.

* The manufacturing costs can be higher, mostly because the number of these engines produced is not as high as the number of piston engines.

* They typically consume more fuel than a piston engine because the thermodynamic efficiency of the engine is reduced by the long combustion-chamber shape and low compression ratio.

 

...i'd just like to point out the fallacy of these two statements: the RENESIS is reported to be no more expensive to produce than your average V6 (at least, that's what was forecast and got out to us). also, a 10:1 compression ratio isn't low. it's true that the wankel type engine has a hard time getting compression high enough to run with deisel, but it's not impossible (just need very narrow rotors).

 

Concur; this is what the manual says. Plus Heather at MNAO wrote me an email, to wit: "Mazda does recommend 91 octane gasoline for the 2004 Mazda RX-8. 87 or 89 octane gasoline will not cause engine damage, but please keep in mind it will not provide the best performance and could cause engine noise. The type of gasoline you use should not affect the gas mileage the vehicle will get."

I'm mostly using regular and getting about 16.5 mpg. I have something of a lead foot. Occasionally, I'll shift to premium and compare mileage but I don't expect it to matter.

A lot of people bitched at me about using 87 and decreasing hp by like 5%. I got a real chuckle out of this when it was discovered we're losing maybe 20-25% power via the drivetrain and no one noticed till the put it on a dyno. the fact is, the difference in performance btwen 87 and 91 octane is utterly undetectable.

 

i get about 18-20mpg out of all of my rotary cars (11-14 for the 20b) and its mostly how you drive, plus a little for the condition of the car.

mike