RX4+30Years=RX8

All things being equal and all dealerships being responsible to Mazda, there should be no reason for me to have to drive even farther and waste even more gas to take it to another dealership. That is the dealership where I purchased the car and while I have no specific loyality to that one dealership I do not feel it is my responsibility to take the car elsewhere when Mazda has certified them as being prepared and able to make warranty fixes. If that is not the case, then Mazda needs to know so they can take whatever action is necessary to pull the franchise agreement.

ScandlsRx-8

I completely agree. As sad as it is it just seems that all dealerships are not equal when it comes to service. I am just familiar with Joe Myers since my parents live in Tomball and that dealership always serviced my rx-7. I never did seem to have very good luck with them. I live in Austin now, but purchased my latest rx-8 from Munday Mazda. No clue as to how their service department rates, sales experience was good though. Sorry to hear that you have had problems with your rx-8. I just hit the 600 miles mark on my 2005 today so we will see how things go on this end.

zoom44

split this conversation out from the other thread. carry on

philodox

Holy sheep ****. I did a master reset of the ECU. Not the 20 brake stomp one, but holding the trip meter button down while turning the ignition to the on position. I did that three times. Now for the amazing part. My last tank of gas was 22mpg. How the hell do I go from 10mpg to 22mpg? Could my ECU have been that confused that it was running "warm up" rich all the time? Very Very strange.......

Go48

WOW! That IS amazing. Is it possible that you may have hit on a "fix" for the low mileage problem? If I had the problem, I would immediately zero-out the PCM. Nothing to lose and everything to gain I would think.

Keep us up-to-date on your mileage in the next couple of months.

om-nc

Philodox,

FWIW I had the battery out of my car while installing a ground wire set ( I know, don't start the flames, it may not help but it shouldn't hurt). I autox'ed the next day and only had about 6 gallons of gas in the car. Filled up after the autox and the next tank mpg dropped to 13 from my normal 17+ city 20+ highway. I was about to get worried and I noticed it "gradually" crept back up. I guess it was about 3-4 tanks full before it was back to "normal". Filled up yesterday, mpg was 18 in town.

With your experience I wonder if the ECU "hiccuped" and hung in the rich mode causing the poor mpg. My experience was it took about 750-1k miles to reset itself. Could the KAM have anything to do with this?

om-nc

Howard

When they reflashed mine does that reset it? I assume it does. That didn't change my mileage.

Go48

It certainly would be nice to know a bit more about the KAM. In fact, I think I will start a new thread on this topic.

rx8cited

I had to search for it, so here it is: https://www.rx8club.com/series-i-tech-garage-22/kam-tutorial-48768/

amartin

1st Tank 18.33 mpg, cruze control set the entire way @ 85mph.
2nd Tank 20.90 mpg, cruze control set @ 85mph
3rd Tank 17.33 mpg, cruze control set @ 102mph, and upwards of 120mph at various points. (Lousiana to Texas "bridge", everyone was doing 100+)
4th Tank ??? don't know yet.

I think I missed a tank full in there...

Anyway, basically, for my RX-8, on the Highway I get ~18.5-19mpg doing around 80ish... City I'm getting 15.5ish.

Still not very impressive, and no, I'm not going to go 55mph... Speed limits here are 70mph, do 80-85mph is "common".

I still don't see how people are getting 24+ mpg.

I really think they need to change the epa mpg rating to 14/19 for this car.

zoom44

you have a problem. i can routinely get 23+ mpg on long highway stretches with cruise set 80-85. are you sure you were in 6th? the only time on the highway i got less then 22ish was when i was 95-100+ for a long ways.

MTCD01

Mine gets 21-23 mpg at varying speeds from 70-95 mph on the highway (no congestion).
About 13-14 mpg in the "round town" driving I usually do (many trips to the beep).

brillo

see my post in the gulf regional section about ways to improve your gas mileage

dmp

How long is a 'long stretch'?

And geesh...you fockers SPEED a LOT!

:D

DreRX8

Becareful on that I10 bridge 'Atchafalaya' causeway--they use aerial enforcement sometimes. A friend of mine got popped on it. With my Cobra radar, which isn't the best, I speed all the way down I10 EXCEPT for on those stretches of causeway.

zoom44

i mean all highway tanks. fill up get back on the highway and then get back off for another fill up. from portland to irvine california i never got below 23 mpg until the one stretch in cali when a whole bunch of 8s and 7s were together doing over 90 and at times as high as 120. that tank i got 19-20 mpg( there might have been one tank that was like 18.8 or something in there). same with the return trip. earlier last year when i went from portland to wenatchee WA i got 22-24.x on every all higway tank and that was with cc set at 80. before that was a trip down to monterey and back and even coming back up the winding parts of hwy 1 i still got 20 or better. i cant think of any all highway tank i got less than 19mpg.

93rdcurrent

The highest I have ever seen was when my wife drove for a tank of gas on our cruise to Santa Cruz last year. She was doing 65-70 mph with cruise control on and averaged about 22.5 mpg. I usually don't get better than 19 mpg on the freeway. In the city I'm about 15.5-16.5 mpg. I haven't ever been able to get above that and I do use 6th gear as often as I can when I'm on the freeway.

zoomallday

Ok, I am a very happy newish 8 owner. Got 700 miles. I seen 15 to 20 mpg in various driving situations.

The 8, as we know, has an engine that requires more RPMs that piston engines to get its power/torque. People used to gas engines, see an engine at 2, 3 or 4k RPM and assume it has power and just press the pedal. If the 8 is in top gear (that would be 6th), and you press the gas pedal way down, lots of gas is released but little acceleration occurs (well actually, I think very nice acceleration but not as much as in other RPM ranges and in other gears). Thus the effectiveness of gas consumption to acceleration is low. You might press the pedal half the amount and get 80% of the same acceleration. This general phenomenon makes people press the gas pedal more as opposed to shifting gear, putting the engine in a better gas/performance ratio and accelerating. Similarly, you could press the gas pedal less, get about the same acceleration but consume less gas. If you are used to a rotary engine, this would be more natural to you.

The above is based on the assumption that pressing the gas pedal does, in some way, correspond to more fuel being thrown into the rotary chambers without a computer somewhere in the middle serious tampering with the effect of pressing the gas pedal.

What do you guys think?

velociti

iTrader: (1)

*ahem*

Xyntax

There's been tons of theories about this. I have a thread that was called 3250 - 3750 rpm is the key.

All I can say to your theory is... hmmmm...

Batmobile1

uh.....i dunno. Back in the stone age when strange lumps of metal with hundreds of little holes in them called "carburators" roamed the earth and metered fuel I would have bought the theory 100%. Especially with an accelerator pump that gushed fuel into a motor when the throttle was depressed quickly. In this age of computer aided wizardry however, the pedal is often disconnected entirely from the engine. Now, a pedal is depressed to a certain degree which is assigned a corresponding value inside a tiny little black box. The magical engineering gremlins translate this number as a scale amount of desired torque. These same gremlins then converse with predetermined flow charts and graphs that ultimately decide that the best course of action is simply to pour gasoline into your spinny combustion chamber until enough exhaust is produced to turn your shiny chrome tips black; the ideal amount for power at any given RPM! I burned $12 of premium fuel in the course of 1 1/2 hours and about 18 miles last saturday on a trip through my favorite twisties. All I know is this, those engineering gremlins have managed to develope a correlation between fuel spent, and the size of my smile. I'm grinning ear to ear.

JM1FE

Close.

I call BS on the original 'theory'.

The accelerator pedal 'requests' more air to be allowed into the engine, by opening the throttle plate. More air cannot enter than leaves the engine (an internal combustion engine is basically a pump). At a given RPM (4000 for an example) there is a lower-than-ambient pressure in the intake manifold as the engine is 'hungry' for more air than your current throttle plate position will allow in. Opening the throttle plate lets in more air to 'satisfy' this hunger, and thereby raises the manifold pressure. As this increased volume of air flows towards the combustion chamber(s), the MAF (mass airflow) sensor determines that for X amount of air, Y amount of fuel is needed. This is the 'fuel mapping' that the engine computer does. You would think that it would be stoichiometric across the board (14.7:1 ratio), but in fact it may be slightly richer or leaner at different points. This is what the engine computer software (e.g. the ECU 'flash') does, in part. This increased volume of fuel & air causes the engine to accelerate above our example 4000 RPM to the point where said amount of fuel/air yields enough energy to spin the engine at a new speed (5000 RPM for an example) and no more. The fuel/air ratio stays roughly the same, controlled by the MAF/computer.

Since an engine is basically a pump, at a given RPM it can cycle only so much air in/out.

Therefore, when going up a hill and you floor it instead of downshifting, you're increasing the manifold pressure, sure. BUT, and this is key, if the RPM stays steady then the engine is only passing so much air through it. The amout of air limits the amount of fuel (due to the computer-controlled mapping ratio). Where it gets less straightforward is in the temperature differential of the air in/air out. There's all sorts of thermodynamics involved with the heating/expansion of combustion. However, the point is that there is not a lot of liquid gas gurgling unburned through your engine just because you depress the pedal without downshifting.

Edit: This also applies to the idea of reving to 3000rpm and switching off the ignition. As soon as the switch is off, no more fuel is being pumped into the engine. Any air that passes through the engine as it 'winds down' will evaporate any unburned fuel, thereby reducing (maybe eliminating) the possibility of a flood condition on restart.

Batmobile1

oh c'mon man, that was much less funny....

IcemanVKO

Okay I thought this was funny.

zoomallday

Ok, I understand that the air intake regulates throttle, vacuum and eventually gas consumption. But there has to be something that goes the change of RPM. If you simply create more vacuum the engine will stall because of lack of fuel (it takes some time for the more fuel to arrive). Essentially, this introduces what used to be called advanced timing in those antique carburator cars. Correct?

I can reword this to: does forcing the engine at low RPMs to produce more power result in a less efficient gas to power ratio? I understand the HP curve is about linear but is the gas consumption as well? There is probably a sweet spot (or range) per gear...?

???