PhineasFellOff

310 guy, if you can take a short distance trip to say northern California or Las Vegas, try experimenting by going 70 or 75 mph on cruise control the whole way (for one leg). If you can get AT LEAST 22 to 24 mpg, then your engine is probably fine.

If I were in your position, wondering whether it's just the way I drive or something is actually wrong with my engine, I would DEFINITELY start with the above experiment and go forward from there.

310Guy

Yeah, I've got a road trip this coming weekend (5/22) to northern California.

If I get over 20 mpg during this trip, I would agree that my engine is probably "okay."

However, if the M calibratoin is done on 5/18 I may never know what was really going on; all I care is to get SOME improvement.

Since I've been keeping a mileage log, I've driven almost 2,500 miles and my average is 14.53 mpg.

RevRaz

So just go jump on the FWY for about 60-100 miles and see what mileage you get before you flash.

310Guy

Well I won't have the time before the service visit but the "best" tank mileage I got was 17.36 mpg which included approximately 150 freeway miles to and from West L.A. to El Toro Base in Orange County. Total miles on the tank was 230.

PhineasFellOff

The first tank after getting the L flash got me 23 mpg and the second tank after the L flash was the start of my cross-country trip, during which I IMMEDIATELY got outstanding mileage (the trip is fully documented in my mileage thread in the Discussion forum). However, under normal mostly hwy driving around LA, my average before the L flash was 20.5 mpg and after the L flash has been 21.5 mpg.

So I'm saying the L or the M flash should probably get you better mileage just about immediately. If you don't see improvement on the drive there, then test again on the trip home. The trip home should get you slightly higher mileage anyway, which I've found out myself (going south on the 5 from northern California PLUS south on the Grapevine isn't as bad as going north).

Finally, you don't really need to worry about what your car could have gotten ideally before the M flash. With the M flash, either your car will see almost immediate improvement or it will not. If not, then you can infer that something is wrong with your engine. If you get improvement, then focus on how much improvement. If the improvement is great, such as 22 to 24 mpg, then you can infer that the M flash helped AND your engine is normal. If the improvement is just a little over your best of 17.36 mpg, such as something like 19 to 20, then you can infer somewhat tentatively that the M flash may have helped BUT something is still wrong with the engine that is not related to the fuel management aspect of the ECU.

Genshie

If you want good fuel mileage, keep the engine at or below 3750 RPMs on the highway. However, this limits you to 74 MPH. Anything above this opens up the secondary ports and then you consume more fuel.

Kurt G.

RevRaz

Well, my recent 125+mph did lower my mileage, I got 21.9 mpg instead of my norm 22.8 :p

Mikelikes2drive

so black soot on your exhaust tips is bad? I'm running rich? wat can i do to stop it from running rich? why do i want to stop it? haha sorry im a newb.

PhineasFellOff

Mike,

Get the latest reflash, which is the M. That flash runs leaner.

310Guy

"The oxygen sensor is part of the emissions control system and feeds data to the engine management computer. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.

The engine burns gas in the presence of oxygen. The "perfect" ratio is 14.7:1 (different fuels have different perfect ratios -- the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). If there is less air than this perfect ratio, then there will be fuel left over after combustion. This is called a rich mixture which is usually seen by black exhaust smoke and black soot on the exhaust tips. If there is more air than this perfect ratio, then there is excess oxygen. This is called a lean mixture which is usually seen by blue exhaust smoke."


So, this black soot is telling me that my 8 is running rich and, in essence, wasting fuel; hence poor fuel economy.


My baby is now at Galpin. I'll know what they did tomorrow afternoon (Wed.).

Mikelikes2drive

i did get the M reflash :/ so what can i do to not make my 8 run rich and in essence not waste fuel? does it have anything to do with the way i drive? i am getting pretty bad mpg like around 15. can i complain to the dealer somehow and get it fixed? thanks guys

Genshie

Another solution would be to create a custom cold air ram intake. This will feed a larger volume of air to the combustion chamber, therefore more completely burning the fuel. I did this on my RX7 and the difference in fuel economy was amazing. Not only did I boost HP (especially at higher speeds) but I went up by 4-5 MPG. I am not sure what effect it will have on the RX8. There may be a more complex MAF/MAS system nowadays that will trigger off a check engine code, but it is definitely worth a try. Adding more air will help lean out the mixture a little.

Kurt G.

310Guy

It is my understanding that rotory engines "normally" run a bit rich.

Adding more air would be the way but as said above, today's MAS would almost have to be re-programmed (hacked) to deal with more air from an intake.

It should be interesting after my re-flashes. After a couple of tankfuls I'm going to install my K&N intake and see how that effects mileage, if at all.

d0 Luck

ding ding! we got a winner!!

rotaries do need to run a bit rich so as to keep the motor cool!!

btw, 3000lb. car + rotary motor won't add up to 16 and above MPG!!

you guys are dreaming..

GiN

The 275 miles on my trip meter (reset after last fillup) is wrong...
Plus, the gauge reading of 13.06 gallons at the gas pump (after a full fillup) is wrong too...
I have been dreaming for the past dozen or so trips to the gas station.

310Guy

Just ignore him GiN otherwise he'll keep posting...


Besides, he doesn't even own an RX-8.

Just another loser who needs to find a better way to spend his time.

RevRaz

I should take a pick of my Odometer, gas pump and receipt and post it so that moron will shut up.

310Guy

Okay, I’ve had the "M" calibration at Galpin Mazda.

The Service Rep, Sam, was everything the others have mentioned elsewhere on this board: he was great. Took care of my car, listened to my issues and actually seemed to know about the RX-8. (Unlike the moron Jack Rollens at Santa Monica Mazda.)

Anyway, my initial impressions are as follows:

- power does seem a bit more linear and smooth unlike before; there is no sudden "surge" around 3,500 to 4,000 rpm

- engine definitely starts immediately; I was having issues with my 8 sometimes starting only after holding the key in the 'start' position for a second or two; don’t have that now at all

Only time will tell about the gas mileage, if it will improve or not...

I am just glad to have my 8 back. I had a loaner, a Saturn Ion. While the Saturn serves its purpose, it made me appreciate my 8 even more – with or without my fuel mileage issues.

My road trip up to northern California is not going to happen this weekend but I do plan on driving my car quite a bit to see how my fuel mileage stacks up after the "M" calibration.

Either way, next weekend I'll be installing the K&N intake. I've done everything possible with Mazda about my mpg issue.

BTW, even AutoWeek mag made some comments about the fuel mileage being a bit "off" from what is reported...

http://www.autoweek.com/search/searc...47004&record=1

"We also worry about the Wankel's fuel economy, at least at this early stage where we've determined the car's smallish, 15.9-gallon fuel tank isn't up to the powerplant's prodigious thirst. Our fuel numbers have hit as low as 13 mpg, which is a surprise for a 3000-pound sports car that comes with federal fuel economy estimates of 18 city, 24 highway."

No ****.

RevRaz

They also stated they kept it at high RPM's too. You cant expect 18/24 at 7000-9000 RPMs.

310Guy

Yeah but I drive my 8 under 6000 rpm and I'm only getting 14.5 mpg average.

Oh well. Things seem pretty good so far after the M calibration. 200 miles on the tank and I've got about 1/4 tank left; mixed driving this past weekend. More details after my re-fill.

RevRaz

They were also using a MT, not AT.

Loaded8

I think I got the "M" flash or the latest they had last week... I noticed the car idles at a little less than 1,000 now. It seems funny but someone else posted about how their gas tank gauge seemed to register differently, I think mine is too ??... I don't think I've seen an improvement in gas mileage but I've been doing a bit of city driving so we'll see after a tank or two. My mileage wasn't bad before the flash (around 18-19 avg) but I think Mazda really should change the stickers to reflect the general averages not the extremely good cases. I've never had a car that I couldn't get the printed mileage, this is a first for me but not enough to make me unhappy with my baby.

310Guy

First fill after the M calibration.

208 miles/12.6 gallons = 16 mpg on 91 octane.

It was a combination of city and some highway over the weekend. I drove from West L.A. to Long Beach (and back) on Sunday. Also drove from West L.A. to Lake Hollywood (and back) twice over the weekend. That driving was probably about half of the 208 total miles.

My mileage was obtained with "spirited shifting" in my AT (paddle shifters). This was done on purpose to really drive the car hard to see the result; i.e. I drove the car the way the car was designed (rotary = high rev).

I am VERY pleased with this result. I'm trying to not get too excited but after averaging 14.5 mpg this is a huge improvement.

I'm going to drive and log miles until Friday, re-fill and then install my intake (finally!). This week will be almost all city driving, to and from work. If it's still around 16 or better, I'm golden. :D

mikeb

finally good news from 310

nice

Xyntax

Is it just me or does 87 octane + M flash has better throttle response? I just noticed it when I decided to fill up 87 yesterday. I have yet to see what kind of mileage I would be getting. Before M, 87 felt more responsive on the lower RPMs but got almost the same MPG with the 91.

Anyone tested this yet?