More Efficiency rather than Power
 

Hey,

I just bought a 2004 Six Speed Manual GT with only 32K miles.
It runs great (as far as I can tell) and looks almost new.
I am averaging 18.7 mpg over 2348 miles, which has included
far more highway driving than I typically do most of the year.
I drive to Atlanta 100 miles or more round trip at least 15 times every
September, but only 1-3 times a month the rest of the year.
I expect to get my average over 20 mpg on tanks that are just to and from my store and around town driving. I do a lot of coasting. With the hills in my area, I can beep second gear and simply roll to my next stop light or turn, which can be as much as a mile further down the road. Sometimes I can do a 2-3 mile stretch of gentle hills with a few brief bursts in 3rd, 4th, or 5th gear.
I have driven a 1992 Miata since 1998, and have put 180K of 220K miles on it.
I have driven manual transmission cars since a 1968 Corvette 4 Speed in 1987.
I'd been a GM American Big Block V8 Torque head, with my first car being a 1972 Oldsmobile Toronado (455 Cubic Inch V8)... with about the same horsepower as an RX-8, but twice as much torque to move a car that weighed almost twice as much. In my RX-8, I would leave me driving the Toro in the dust at about 55 mph, and never look back. I doubt that I ever had my 455 over 3000K rpm... but that car did feel like it was floating along the road. Later I drove several V8 automatic 70's Olds Cutlasses that never quite got tricked out, but always ran hard.

A 1979 Toyota Supra (first model year) was my first Japanese car, and the car that I really got into the manual transmission. That Supra had the best trans ever... until I drove the RX-8!
Since then, I have also owned several other vehicles, both V8 and manual trans, with my Dodge Ram Extended Cab 1500 having both. I have no complaints about the RX-8 mileage after owning that. I do miss the 10 inch throws on the Ram shifter though! ;-)
Between stints of driving the Miata, I was driving a Dodge Caravan (for work and dog reasons). And prior to the minivan for a couple of years I had a fantastic 5-Speed V6 1992 Chevy Cavalier Z24 that got about 20 miles to the gallon and was purchased for $100.

Getting back to my point, I got my car for a few thousand $$ less than I was planning to spend. I am trying to decide if any modifications are beneficial to my style of driving. I am already driving in a manner that gets me higher mileage than most RX-8 owners. My car idles much of the time while I roll down and up hills.

I intend to replace my plugs, wires, coils, all fluids, and an ECU Flash to the latest and greatest, I do not know if any of these items have been addressed ever before. Part of me wants to believe that it is already running at it's peak of stock performance, while the other *more* of me really hopes that replacing these consumables makes it "Go to Eleven."

If I wanted more efficient throttle response, leaner idle, and general efficiency boost, where should I start? Keep in mind, I am driving this on country back roads most of the time, and occasionally at sustained highway speeds, with rare rush hour stop and go. Daily driving involves some high rpm runs followed by long lulls at idle. Most highway involves getting to the posted speed limit in the fewest steps possible, then cruising in 6th.

Is the current stock ECU Flash as good or better than aftermarket options?
I was thinking that a lightweight under-drive pulley set might make sense.
When I have to replace my clutch or feel like doing the work, a Mazdaspeed flywheel seems like the best option for low weight and moment of inertia - I'm open to suggestions though.
I love these wheels, but will consider others when I am ready to replace these tires - they will need to be lighter and easier to clean.

I've read too many opinions on Intake and Exhaust mods to have any idea whether they help or harm performance and gas mileage. My car already goes plenty fast for where and how I have to drive regularly and will not let me down in the situations where I drive occasionally. I've always been a fan of cold air or ram air setups, but I don't know whether the ECU plays nice to make it worth while.

I don't need a turbo right now... maybe when I convert my Miata! However, I am looking for suggestions on which upgrades will provide access to more power while improving gas consumption.

I want to increase my idle efficiency.
I would like to shorten the distance between 3000 and 6000 in Gears 1, 2, & 3.
I would like the motor to spin up to it's operating speed more efficiently - to any speed from idle or any other speed up to red line.

I am curious as to whether anyone has found a "Sweet Spot" while cruising...
Is the engine more efficient with the secondary injectors open, around 3750, or with the primaries maxed out at 3600?

In a month of driving my RX-8, I am finding that it really prefers to be finessed rather than mashed. In my car, I really have to hold the throttle where the engine wants it most. I find that I cannot just mash it to the floor and wait for the engine to catch up. My acceleration is measured in millimeters of right foot. Most of the time, I find myself using a very light pedal, just in from idle, in the most appropriate gear. When I want to accelerate rapidly in 1, 2, or 3, I depress the accelerator gradually, to maybe halfway at 5000 rpm and fully after 6500.

Does anybody have advice for how they finesse their throttle?
What mods would you recommend that can increase fuel economy and open up the power band? I'm happy enough with my mpg, I'm not really whining there, though I am willing to invest some money and time in improving it and making changes that also improve performance. I don't need anything that will increase power at the expense of mpg.

Thanks!

1. Coasting in gear saves more fuel than coasting in neutral.

2. Replace coils, plug wires with better aftermarket product but keep the oem plugs.

3. Get a Cobb Accessport and a custom tune from MM

4. Get a midpipe, lightened flywheel for better throttle response.

5. The throttle application is the same as most other car, as long as you know how to downshift 2 or 3 gear and stay in the powerband 6k to 9k.

6. You cannot have your cake and eat it too.

7. Do more reading on stickies and such, all these has been covered already.

8. Search plz

add a super charger.. you will get better highway mileage...

If you wanted efficiency you shouldn't have bought an 8.

biggest thing I did was an accident. I needed shocks, said what to heck, spring too, cheap, and no extra work. I lowered the front about an inch and got an instant 1.5 to 2.0 MPG. This will pay for the springs in 12 months.

I now have a COBB, and am looking at mileage. I 'think' the benefit was most between about 40 and 60 mph and is from getting through the air better. It 'seems' to be less at 80 MPH, but is still there (last trip to Savannah).

Like above, plugs, coils, I think wires are an option, I did not do them. I have an MM tune coming, but I am very late in the queue. Will be able to tell you more later.

There is a sweet spot, above 3,750 RPM (tach reads high several hundred RPM), where the motor supposedly leans out the mixture at cruising speed. I do not know if it is still there in the MM tune, again, have not had time to play. You can search to find that thread, it is like 6 years old.

What I really want, and do not know how to get, is a 6th gear that does 80 at 3,000 rpm.

I think the record is something like 25 mpg, no higher.

If this is your fist, check the threads in my sig, one is good, one is mine....

They are all good reads. At leat one of which was linked by 04Green above!


https://www.rx8club.com/new-member-forum-197/congratulations-you-got-8-a-202548/

https://www.rx8club.com/new-member-forum-197/new-potential-owners-start-here-202454/

https://www.rx8club.com/showthread.p...&highlight=FAQ

The cake is a lie.

Doh, I thought only the Lamp is a Lie

To bring back something rather old in this forum that used to appear all the time by Chrism................."I like Pie!" :yumyum:

[matrix]There is no cake[/matrix]

The cake is a pie!

get a Z06 IF YOU WANT BBETTER EFFICIENCY

Make Mine Peach Pie with Whipped Cream
 

Yummy! Peach Pie.

Thanks for the spirited conversation, as well as the RTFM and "Search the Forum" suggestions. I've been searching and browsing these threads since getting the car home from the dealer a month ago. It seems the more I read about some topics, the less I know... like oil weight, oil brand/type, premix, any mod, or mileage test, etc. There are threads that look promising that turn out to be old theories or just lunatic raving. Some interesting project details start out with updates posted minute by minute during install, then no follow up reports later of actual gain, loss, or disaster. Really, it's also tough to get through some of the 4 year old flame wars - I'm glad most of the threads have been edited to only include the important ones. As for wasting your time suggesting I buy a different car, I intend to ride this for 200K miles, and I want to have as much fun as possible. Turbo and Supercharger people - I can see forced induction in my future for a rotary Miata, but not now for this 8.

As for everything else, thanks for the suggestions, I'm glad there are still members willing to help a new owner who wants to learn more.
I've read much of these threads during marathon browsing, but thanks for pointing out the threads. I needed to reread some of this. Less sure now though that pulleys or flywheel even matter enough for me.

I have started the First $100 list with the AC Insulating and Re-Program, and bought my contact cleaner to clean the MAF tomorrow. Going to order my plugs, coils, and wires, then work on the other cooling improvements. It can get a little hot here in Hotlanta.

@yiksing - I believe the engine is running richer at idle than at load rpm, however I expect I can play around to find a no-load rpm that leans the mix a little while I can still enjoy the gravity drive. I've coasted in every manual I've ever driven, and my local driving is better suited to the RX-8 than any car I have ever owned. Going to play around with gentle revs as I coast for the next few tanks.

I think the RX-8 has plenty of "Cake and eat it too."
There aren't many other cars where you can be cruising along in 6th gear,
and drop it into 3rd for a little explosion of "See Ya!"
My feel for the rotary is that it will happily go balls out.
I have no doubt about it's prowess at 6000-9400 rpm.
That power is reliably there when I need it, and I know how to apply it. The other 95% of my drive time is restricted by other drivers or posted speed limits.
What I am really wanting to learn more about is how an RX-8 operates at low and mid-range rpm. Am I saving fuel, or just missing out on performance when I'm below 3000 rpm rather than over 4000 rpm.
My favorite place to be is a nice curve accelerating 3rd gear through 6000 rpm. I will always be there when given the option, the rest of the time I want to save a few pennies. In between moments where 9000 rpm is appropriate, I am content to hum along cruising in 6th gear at 2600.

However, I would hate to find out 10000 miles later that instead of 2600 rpm, I could be enjoying fourth gear at 4200 rpm and be consuming less fuel at an effective cruising speed. I also find the RX-8 to be incredibly easy to hold at a specific speed or rpm, but my reading would indicate that steady speeds (over 4000 at least) may cause the ECU to make the mixture richer, burning more fuel rather than gaining efficiency from lower or sustained speeds.

I have definitely felt that mashing the pedal in a gear that is too high will just bog the engine and waste fuel. It is not unusual to go a little faster when letting off the gas slightly from a cruising speed, especially in higher gears. But downshifting to 2nd or 3rd at over 5500 rpm is like hitting hyperspace. I think the Renesis responds to finesse and technique more than anything I have ever driven. I love being being just a flick of the wrist from instant zoom-zoom.

When I am cruising, is a steady speed more efficient than a wave?
Are there times when 4th gear is more efficient than 6th?
Personally, I have been able to cruise in 6th down to 40 mph, but any acceleration requires the most delicate pressure on the pedal, or a downshift.
I seem to be developing a driving technique that involves occasional high rpm runs close to or into the beep zone in gears 1, 2, & 3.
Much more of the time, I am just getting rolling in first.
Second then gradually gets me into higher revs then quite quickly to desired speed or beep. Unless a car in front of me requires a more gentle approach, in which case, I tend to up-shift at 3000 rpm or lower.
If I'm headed to a highway then third or fourth add some speed.
I like to get to cruising from rolling as quick as practical, or as gentle as possible.
Usually Neutral lets me roll the hills until my next stop or turn.
I experience occasional flat or slightly uphill segments of my drive where I cruise in the highest gear possible, or coast in neutral with occasional kicks in 4th or 5th gear to get up the next hill before coasting some more.

Worst case scenario, my fuel consumption isn't going to change much more than $10 a week in either direction. It's not even a huge concern to me, but I have been getting 30 mpg in my Miata, and was considering a 40 mpg Mini as one of my options, but it was a toy compared to the RX-8 samurai jet fighter. I love driving the RX-8 more than any car I have owned or driven. I definitely have the rotary addiction now that I have tasted it!

@ 04Green, I think 25 mpg is a great target. I might be able to do it on my daily commute with the hills... never gonna touch it if highway speeds are involved.
Don't really care, and am not going to worry much about the final mpg. Will probably play around with it for months though to see what helps and what doesn't.

I've probably only had 1-2 cars that didn't burn some oil.
At least the RX-8 owns up to it.
In my 2000 miles, I've maybe put in 1/3 liter of oil in two portions.
Mazda could have made the dipstick more readable and accessible!

I want to spend 97% of my time with the engine at its optimal happy place.
The other 3% of the time, I want to exploit the system for it's optimum performance. Occasional short bursts of intense performance between long miles of peak efficiency. This is "Cake and Eat it Too!"

This is enough for now.

When it comes to dessert, it's fresh Peach Pie all the way! I grow my own.
I'm hoping to have long and detailed discussions about the power, efficiency, and fun of RX-8 driving for years to come! Peace!

Access Port from MM
Flywheel for more response and HP and milage
Lighter racing wheels like Enkei

http://www.rotaryresurrection.com/kl...rum/callbs.jpg

http://www.rotaryresurrection.com/kl...um/bsmeter.gif

I'm just gonna be honost... thats way to much to read. I think i made it to line 4...

Unless something changed, while coasting in gear, no fuel is being injected as opposed to coasting in neutral.

Get to 6th gear asap without lugging engine for best mpg, lower revs always yield better mpg. Honestly it doesn't matter much, I keep a mpg log for my car and what I found out is, driving aggressively i get about 15mpg vs upshifting at 3k to 4k rpm yields 16 mpg.

Most posts here are only interested in getting more performance out of the car. I applaud you on
stating one that speaks tward efficency.

There is a lot to digest here, so let me take a couple of points.

Mazda has to serve many masters. The government wants good fuel mileage, but wants good emissions even more. This requires the engine to run rich to lengthen the life of the catalytic converter. Once the car is sold to us we mostly don't have to worry about this anymore. The Accessport with a MazdaManiac tune does lean out the mixture and should provide better mileage. If he knows you run a cat-less exhaust, he will lean the mixture even more.
I put a Mazdaspeed LW Flywheel on my car when my transmission was being rebuilt. I found it to be a good investment. There are lighter ones available.
The pulleys on the car don't weight that much. Getting lighter ones woundn't help that much. Underdrive pulleys may help a little. You will reduce the load on the engine from driving the alternator and the water pump. In certain situations, on the street, this could also be detrimental. Underdriving the water pump, for instance, could lead to overheating at low speeds.

The ECU will see any changes you make to the intake or exhaust and automatically make adjustments to it's programmed ideal f/a ratio. The car already has a cold air intake that works pretty good. There are a couple of free tweaks that can be made that you probably have already read about. Racing Beat makes a ram air duct that can not only work with their replacement intake, but can also work with the OEM intake.

One thing I didn't see you ask about are fluids. Changing the transmission and the differential fluid to a synthetic type (I use Redline) should reduce parasitic losses and improve mileage.
Theoretically, lowering the car should improve gas mileage. I don't see how it could by as much as the previous poster claims.

Dear RotaryResurrection Dude..

Sorry man, I did not believe it either, I changed nothing else. Did not even disconnect batter to do the work. There were a few threads that hinted at it as well, I blew them off. My work to home and back cycle is pretty consistent. I got right around 20 mpg, sometime dip down into high 19's. sometimes up to 20.5. First tank after change, just over 21 (tank was about half full). after that 21.8, 22.1, up in that range through at least 8 tanks. Used to get 265 to 275 miles before gas light on, now 285 to 290. I have actually seen 300 on the trip meter (reset at fill up), never got that far before. Benefits seem to fall off at really high speed, but still there.

I can also tell you there is less wind noise at about 50 to 60, that points to an aero benefit. If it was not such a bitch, I might try switch back to confirm. But that was a lot of work.

I had a 1977 Toyota Celica GT Liftback (first model year for that one as well) and agree that it had a great transmission.