Psylence

Yes, but some of us get horrible *horrible* mileage no matter what. I suffered through several tanks of fuel shifting below 3500 each time, only to get 13mpg. Best I have ever gotten was 19, and that was with an avg. speed in the low 60's on the highway. (Again, also torturous) Lets not even talk about mileage when driving the car in a relatively spirited fashion. A 220hp car that gets no better mileage than a Ferrari Modena is just plain wrong .

While the trigger wheel does sound a little far fetched, I'm just desperate enough to check it out. Have no other options really, and no one else seems to have any better ideas why some cars are so awful.. so off I go on the hunt this morning.

If I can snag the sine wave, I'll post it up later.

rx8wannahave

Psylence...wow, sorry to hear about your 8's horrid fuel economy. I know you probably complained to Mazda but mybe you need to compain more. If I was getting 13mpg I'd be on the news...doing interviews where I'm sitting in a chair with no lights and a robotic voice, you name it....

SOMEONE is going to explain to me why a car listed at 18/24 does not even COME CLOSE to those numbers. EPA, Mazda....someone...

Keep us posted...

clyde

I get a solid 13MPG when I'm commuting. Short distance, lots of traffic.

I get a solid 24MPG with a fully loaded car on long distance trips over level ground with the cruise control set in the low 70s.

I don't blame Mazda for mileage. The EPA told them what numbers they have to use. Anyone that isn't happy about it should write to the EPA to ask them to modernize their testing procedures and/or to their Congressman and Senators asking them to introduce legislation to direct the EPA to do the same. That's the only way the system will get fixed.

Brice-RX8

Sorry Simo, from what I have gathered from this board that 90% of what works well or can be checked on a bonker engine can't be related back to a rotory, just too different, but you had a pretty good idea to begin with.

Glyphon

i average 18.5mpg 70/30 mixed driving. with my 100% city tanks, i've gotten between 16 and 18 mpg, and never had a tank below 16. my best tank was 23.6mpg and that was 30/70 mixed driving. and i've had 2 or 3 20+ mpg tanks with 50/50.

i'm by far not grandma driving it. my secrets? i get in, and drive off. no prolonged warmup. i just drive it easy until after its warmed up. on the highway, i set cruise at 74mph. Also, to keep the carbon buildup away, i hit redline at least once a day, if not more, and more often than not once per "startup". when driving in atlanta's horrid traffic, i shift between 2000-3000rpm and stay in as high a gear as possible to keep the engine from bogging, which doesn't happen until its below ~1300rpm.

so, averaging 18.5 mixed, with ~17mpg city and 23mpg highway, i don't think the epa numbers where that far off. most peoples fuel economy problems come from long idle times at startup and a heavy right foot.

Nubo

I would really be surprised that the ECU could be "fooled" by a missing tooth or erratic signal. Don't you think it would count all the signals and realize when there were some missing between TDCs?

zoom44

if it didnt get the signal it was "expecting" it wouldnt run period.

therm8

I get those numbers.

zoom44

so do many- wannahave it is either the car, the driver or the parameters of the drive not the rating.

Dragonrider

I was informed that US imports specifically have been detuned deliberately to accommodate the import standards for longevity of the CAT. :p

When I took my cat out my 8 started throwing 10 to 15 ft fire *****. Got a Canzommer cz 1/2 and leaned it out and got it down to a minor spit of fire every now and then.

I did learn one interesting bit of info lately on this subject.

Since most who are complaining of low hp do so because of DYNO readings, including myself, I found that none of us took some very important characteristics into account.

On a DYNO of course the car is not moving so there is lower air flow and thus higher heat. I did not know this, but when a rotary heats up, the ecu starts reducing HP for self-preservation. Also learned that for a true HP reading we need the front wheels turning with the back wheels.

Those are just two the variables that attempting to get a true HP reading on the 8 on a DYNO a bit challenging.

Who knows, we all may be getting the HP we thought, but we just can get a true reading at this point to verify.

Still, in the MPG arena, mine is a tad on the low side like most everyone else due to the overweight right foot problem. Maybe we should consider OWRFA (Over Weight Right Foot Anomalous) organization to help with the low MPG. Nah, let the over-weight right foots like me have our fun. :D

This are just some of what I have just learned that might be causing some of the challenges with the supposed low hp.

zoom44

nobody and i mean nobody start a hp arguement here in response to dragonrider or they get a 3 day suspension

dragonrider- the hp things and dyno things you mention are well known and well discussed topics on this forum. there are oterh threads for that . this one is about the possibility of trigger wheel damge causing the car to not operate correctly.

all- the topic here has nothing to do at all with rated mpg or HP. it is about those who have docummented continuous extremly poor mpg and/or power when compared to other 8s with the same package/accessories adn flash level etc. in other words all things being equal their car performs very poorly in these parameters when compared to other 8s.

r0tor

iTrader: (1)

i guess if this makes a difference or not comes down to if the ecu does a tooth count check or not.

If its just set up to fire the plugs and deliver gas at a certain amount of degrees past an index point and not do a double check of the tooth count, i could see where things could fall out of timing and the ecu not pick it up.

simo

ok guys , let me tell you something...

Whatever ECU either of the RX8 or a piston engine are made to detect the signal from the trigger wheel with the Hall sensor.

The Ecu , since is not given a human intelligence, has a little tollerance to accept or not accept a signal , otherwise the car wouldn't run.

The tollerance is +1 Volts to +5 volts per 100 rpm increase untill 1500 then it goes higher untill reaching , for you guys 9000 rpm.

So for a ECU , i repeat is not a human, doesn't metter that the signal from the Hall is little bit lower then the other theeth.The Ecu wouldn't fire if the signal would be absent more the 3 or more theeth or more, or untill it would see the signal.

Bosch Motronic for example has been studied that the ecu wouldn't fire untill it gets the signal.
So let's say you take apart the hall sensor while you are crancking the engine and then you put it closer , then the ecu will start to count and fire but only after it sees the gap to calculate the TDC.

The 8 might even be a different system but i know it would accept a bent tooth or a ovalized wheel.

This is becouse your Ecu has a tollerance and whatever there is in that tollerance is acceptable.

Let's say you have a lambda sensor and lean is 1 volt and reach is 10 if for some reason you have a problem with this sensor and it gives to the ECU a 10 volt signal constant you will run lean and the ECU will not show any orange light, unless it has a program that would not accept a rich or lean run for more then a certain time.


But with the trigger wheel even if a tooth is missing the ECU wouldn't stop the engine becouse the process is so fast that it's like it is you are crancking the engine again and so unless you have a strobo you can't be sure about your timing.

The RX8 is a car of 35000 and there are planes that cost 1 million times that and i can tell you the ECU is not so sofisticated.

There is a car that impressed me with a sofisticated ECU and this is a Mclaren with 3, i say 3 trigger wheels, and 6 hall sensor.

Ferrari just upgraded to 3 lately.


I am not trying to convince anybody, i just want to help .
I remember that my car , with piston engine, was showing , with the ECU rader, 35 degrees BTDC and with the strobo you could see the timing jump fro 15 to 20 degrees and only one piston was recieving the right timing.

Once i saw that with my eyes i understood that the ECu was lying.

I reality it was not becouse the ecu counts ONLY THE TOP MIDDLE AND BOTTOM OF THE WAVE, IF ON IS MISSING THE ECU WOULD GET THE NEXT ONE WITHOUT COUNTING THE MISSING ONE.

if you don't believe me get the map of your ECU and see the program under the name TIMING.

You would read ,maybe becouse yours is a different car, wave form counting:

Top, 1/2 down, next 1/, 0 , ect.

I am saying to see the wave for those that experience only loss of power associeted with high fuel consumption

therm8

While reading this thread, I can only think of Occam's Razor. It's worth a shot . Things are built with tolerances from the factory. I find it hard to believe that the wheel must be exactly right for the car to run. If it's off just a bit, it could have an effect.

\\Konig\\

iTrader: (4)

Simo is it that hard to tell us the actual name of "your car?"

SAFD1450

I am not a car expert by any means, but I think somebody that is getting really low mpg should send him what he wants. The guy at least has good intentions. He isnt asking for any money or payment of any type. Just my 2 cents.

simo

my Car is a Calibra 2.0 L 16 V naturally aspirated

Hyperborea

Not sure if this is a source of problems with the RX-8 but for owners of my previous car model this was a problem - sort of. It was more often the other way around. The Hall sensors would fail. If they were only partially failing and giving a bad signal then you would see low power and bad gas mileage. If they failed fully (or at least too much) then the car wouldn't run.

The reasons that the Hall sensors failed on my previous car model was that they were getting old - late 80's / early 90's sports cars. Now, if the Hall sensor failure can cause this then why not the reverse? Why couldn't trigger wheel imprerfections cause this too?

What we need is somebody with a "problem" car and oscilloscope to check this out.

\\Konig\\

iTrader: (4)

ok, thank you.

zoom44

re-read MazdaManiacs post.

Psylence

I'll have a waveform from my car next week. Would have had it Friday but our engineers were in the field with the 'scopes checking out some of our new equipment..

Anything is worth a shot.. hell I'd start burning candles and sacrificing chickens if I thought it would work

rxeightr

Here is a little more detail to what zoom44 posted earlier.

There is a MIL code if the sensor provides erratic readings, so I personally doubt this is the cause of poor mileage.

olddragger

iTrader: (3)

Could be something to it. Its a complex thing. For instance why does the maf voltage vary from car to car,event to event? Read the CZ threads. Who the hell know WHAT this ecu is exactly doing! If someone fully understood it then the by pass engineering could be done NOW.
Must break out that old Captain Hero decoder ring and plug it into my tandy.
Olddragger

zoom44

Psylence- when i come home for christmas we''ll go out on the turnpike in your car for a couple of full tanks and see what mpg we get. if i cant get you close to 24 mpg then we'll know you have a problem.

zoom44

i have the answer to that actually i spent awhile researching it. and the variability is much less than you would expect or have been led to believe. most of the variances are because of actaul throttle posistion and the amount of air flowing in. i was a stead fast believer in the phenomenom myself until doing the research. of course there are some who will choose to believe other wise no matter what the truth is.