Hi everyone, my name is Simo and i wanted to share with you why some of the RX8 have a hi fuel consumption and not the claimed HP.

Believe it or not the prob lem is in the pulse generator wheel!

I had the same problem in other cars a long time ago and the ecu was showing no errors and so the dealer didn't do anything.

so i started to replace all the sensor and the ECU and nothing happen.
After 2,5 years i went to do a course in Modena(Italy) and took a course to diagnose electronic injection problem wit the oscilloscope.

After that course i found 1 week later the problem.

For those that have a hi fuel consumption and low hp can contact me at
simonecavallo77@hotmail.com

I am not charging anything i just want to help! i know how terrible is to be in that condition, i was getting crazy!

If you know somebody that has an oscilloscope check the signal from ths Hall sensor and it as to appear as a smooth wave with no interruption.
If you get at least 1 minut signal and send it to me by email i can tell you if that is the problem or not.

^be a bit more specific as in what we need to look for?

...Believe it or not the prob lem is in the pulse generator wheel!
HUH???

I checked my pulse while touching the generator and the wheel and it was fine..... Is that what you meant?

I get 13 mpg...is that low enough?

HUH???

The Hall sensor is used to detect the position of the crankshaft. Not sure exactly what the issue that Simo is talking about but a problem with the Hall sensor sounds like it could plausibly lead to low power / high gas usage.

Yeah, I get 11-13 mpg as well. What and where do I need to check? I've got all sorts of gear here for our engineers to use, so testing a sensor output is no prob. I'd do it right now if I knew what and where....

Did anybody e-mail this guy yet?

ok guys most of you don't know that cars today have digital spark timing adjustment.

As you know the advance timing means Power.If for same reason your timing is retarded you are loosing power and since the ecu is still injecting the same amount of fuel you are burning something that is not contribuing to push the car forward and so your mpg goes bad.

Now let's get down to business.

The Pulse generator wheel is a wheel with 60 teeh or so and 2 missing teeh.
Tje 2 missing teeh is the TDC and the other teeh are for the ECU to know when firing.
The Hall sensor is a sensor with a magnet and if you pass a piece of metal close to it, it will generate a pic of electricity.
Whenn this wheel, that is attached to the cranck shaft , spinns the hall sensor, that is very close to the perifery of this wheel, will make a wave and this wave is sent to the ECU.

EVERY WAVE IS A CERTAIN DEGREE OF THE CRANCK SHAFT, AND IF THE SIGNAL IS DIRTY THE ECU WILL NEVER SHOW ANY ERROR BECOUSE THE PICK OF THE SIGNAL IS STILL IN THE SPECS BUT ONE OR MORE WAVES ARE ABSENT AND SO THE ECU WILL COUNT , LET'S SAY 25 DEGREES ADVANCE, BUT IN REALITY THERE ARE 15 OR 10.

DO NOT BELIVE WHAT THE ECU SAY: WHEN THE ECU SAY 20 DEGREES ADVANCE IT'S NOT A REAL ADVANCE, BECOUSE IT IS ANLY COUNTING 25 TEETH, AND SO IF ONE OR MORE TEEH ARE MISSING THE ECU IS STILL COUNTNING 25 BUT IN REALITY THE POSITION IT IS FIRING IS AT THE 27 OR TOOTH.

THAT IS HAPPENED TO ME

he is saying something about the wave form sent from the sensor on the trigger wheel not being correct and causing low mpg and low hp? do i understand that correctly?

Yes You Are Right

The Trigger Wheel Is Bent Somehow Or It Is Loose

How did you fix it on your car?

Interesting

replaced the wheel, the previus one had 4 bent teeh

Ok, badass. Now to get to finding this thing on my car and testing it. Anyone got a diagram?

the wheel itself costed me 20 euro, but to replace it i had to take the engine apart becouse in my car it was inside.

My the 8 is outside and it is easy to check.

Can we check this without removing parts or jacking up our cars? I'd like to inspect this myself.

you need an oscilloscope and you have to attach the two terminals at the exit of the Hall sensor.
Register the signal in a GIF format and send it to me and i'll tell you if you have a problem with this wheel.

can someone post a picture?

it is very easy to check it.

You have to find the hall sensor and mesure the signal coming out of it, that's it!

I believe you have to remove few things to reach it.
Since i don't have this car i can't tell you where to look for, but i can tell you that the tha Hall sensor is very close to the trigger wheel and the trigger wheel is alligned with the crackshaft, so knowing that i would say check along the longitudinal axe of the engine.

Well I know what I'll be doing first thing in the morning here at work.. hunting up that sensor. Will email a gif of the output as soon as I have it.

Sorry, but I'm very skeptical about this. I'm almost positive that engine speed AND crank position are both derived from a pulse signal that is generated as the teeth of the FLYWHEEL pass by a magnetic pickup. It's similar to what you're describing, but there is no separate "trigger wheel" that I am aware of. Look at the attached pic--see the teeth on the circumference of the flywheel (MS flywheel shown as an example, pic courtesy of cortc)? There are on the order of 200 teeth on the flywheel, which gives adequate resolution for crank position. If what you are claiming is true about a trigger wheel with 60 teeth, the crank position would only have a resolution of about 6 degrees... that doesn't seem adequate to me. (BTW I am using the term crank position but I guess it's really eccentric shaft position in the case of the rotary). Now tell me how the teeth of the flywheel are going to bend to mess up the signal??? It's just not going to happen. Now if I'm wrong, I'd like to learn more.

I have never heard of an engine running off of a flywheel pickup. Tell me where TDC falls on your flywheel? ;) Oh wait, theres no reference markings! Thats because it doesn't work that way.

This is the stuff that trigger wheels and crank angle sensors are for.

I am going to laugh my ass off if this ends up being a real fix. This fella seems sincre and we certainly thank him for that. Again this forum is great.
olddragger

Yeah, just about anything is worth tryin' at this point. Especially if you already have 'scopes sitting around anyway :)

I have never heard of an engine running off of a flywheel pickup. Tell me where TDC falls on your flywheel? ;) Oh wait, theres no reference markings! Thats because it doesn't work that way.

This is the stuff that trigger wheels and crank angle sensors are for.Like I said, I'm willing to learn. :) I guess I don't see why it would be so hard to put a reference marking on the flywheel and install in the proper orientation so it could measure crank position. It seems to me that this would be more efficient than having two separate pickups for crank speed and crank position.

The shaft position sensor is definitely on the front, behind the bottom pulley. The sensor has two wires, and at connector B1.27 they are Y/R & Y/B.

Mr. Buckeye is looking at the ring gear.
S

So your telling me were going to get more mpg and more horsepower?

I sure hope your right

Do you mean to tell me that the whole time we've been looking for a software solution that the problem is, in actuality, a mechanical one?? It would be great if it is but something doesn't add up.

The low(er) mileage and loss in horsepower and Mazda's changing of the rating for our cars from 250hp to 238hp indicates that this is an across the board type problem. I can't imagine that the manufacturing and assembly procedures are so poor as to allow every single RX-8 out the factory with defects on this pullyorwhateveritis. I'm still a bit skeptical. Hopeful, but skeptical.

i didn't say this is for sure your problem, but if you check the scope and see something strange happening to it then you found the prob.

the picture you showed us is for the starter to start the engine, that's not a pulse generator wheel

The low(er) mileage and loss in horsepower and Mazda's changing of the rating for our cars from 250hp to 238hp indicates that this is an across the board type problem. I can't imagine that the manufacturing and assembly procedures are so poor as to allow every single RX-8 out the factory with defects on this pullyorwhateveritis. I'm still a bit skeptical. Hopeful, but skeptical.

My screen name says it all. I was wondering if I was the only skeptical one. This just gives me the gut feeling along the lines of an "electric turbocharger" or one of those "power capacitors".

The loss of power i am talking about is not the 250 to 238 rated from the Mazda, i am talking about the loss of power of those guys that miss power all the way up to 9000.

I know it is strange and unbelieveble but my pulse generator wheel was bent, and i can't explain why.

It is somthing that spins with the engine and it seems impossible that it can loose it's concentricity, but i can tell you mine was almost oval!!!!

so how much of a HP/MPG gain did you get?

he is talkign about those individuals whose car is geting like 12-13 mpg and whos 8 is slower than other people's 8. he himself does no thave an 8 but he was experiencing really low mpg with his car and found this to be the answer for his car. he is suggesting that rx-8z which get extremely poor gas mileage may also have this problem with the triggger wheel

i had a aspirated 2.0 L 16 valves and it was supposed to deliver 154HP.
I was missing 25 corrected hp and nobody could explain my why.

After i replaced my trigger wheel i gained back was i was supposed to have.

I suggest to those that are in high fuel consumption to get the cope pattern and to compare it with those that don't have this problem at all.

Let me know
Simo

here is what is commonly called the trigger wheel for our cars. also known as the e-shaft position plate. remember the 20 brakes stomp reset also resets the eshaft position plate profile in the pcm memory.

http://www.rx8club.com/attachment.php?attachmentid=55065

he is talkign about those individuals whose car is geting like 12-13 mpg and whos 8 is slower than other people's 8. he himself does no thave an 8 but he was experiencing really low mpg with his car and found this to be the answer for his car. he is suggesting that rx-8z which get extremely poor gas mileage may also have this problem with the triggger wheel

yea i knew he didn't have our car i was just wondering what it did for his car.

i wasnt speaking directly to you GR8 just in general to the thread in case that was missed by some;)

oh ok lol

where is the e-shaft position plate located?

are those sine waves on that diagram what our o-scope reading is supposed to look like for the 8

well that must not affect me because while I do get poor mileage I think mine runs on the strong side power-wise, the low mileage is probably a right-foot control issue :angel:

the picture you showed us is for the starter to start the engine, that's not a pulse generator wheel


it's called a flywheel, let's not start another "lower rocker arm" thread :D

it's called a flywheel, let's not start another "lower rocker arm" thread :D

LOL where did he get a starter from ? LOL
man where R/G

Yes that picture above shows the exat sinewave that an o-scope should show as the wheel turns. The wheel is not a 60-1 or 60-2. The most common wheels out there are 36-1 or 36-2 wheels. The RX-8 wheel is a 36-2-2-2. Look at the above picture to see how this works. Notice that each individual tooth is 10 degrees apart center to center. Since we only have 360 degrees in a full circle, we divide that number by the degrees of separation to arrive at 36 base number of teeth. However we see that there are flat spots. Notice that in the middle of these flat spots is what looks like the top of a tooth. It is. Also note that the teeth at the ends of these flat spots are exactly 30 degrees apart. Each tooth is measured from the center of the tooth to the center of the next. Since at least 5 degrees per side is going into the gap between the teeth, that leaves us with 20 usable degrees left in this large flat area. This means that we are missing 2 teeth per flat side. This shows up as the -2. There are 3 sides like this. -2-2-2. 36 base teeth, 3 gaps of -2 teeth = 36-2-2-2. Currently only the stock ecu or a Motececu can read this pattern as it is unique in the automotive world.

The ecu code is written to read these large areas without usable teeth but it also reads the number of teeth between these gaps. This is how it knows how to time the engine and also how to verify which rotor it is firing at. This whole sequence is only used to determine where top dead center is or more appropriately 5 degrees btdc is for both the front and rear rotor. That's all the trigger wheel does. The ecu uses this base as a starting point for which to start adjusting timing either advanced or retarded. If there is any problem with the way that the ecu sees the pattern of the teeth, the car will not run. It can't as the ecu is no longer getting the correct signal. Any problems would be located in the software and not with the wheel.

I could go on as to how this would or wouldn't have an effect on the car's performance but I am going to say that the reason some cars are getting bad mileage is not a result of the trigger wheel. Someone is really going to have direct verifiable proof before I will believe that. Sorry.

Thanks RG for the explanation. I was a bit skeptical but at the same time getting a little excited that the HP and MPG could be solved with a piece of hardware. Still, if someone could get their hands dirty and verify this, it would be great.

If someone could just get a reading and send it off to see what he has to say it would be great. I agree with RG though, it will take some hard proof to convince me that this is the problem. Thanks simo and RG.

Uh, lets see. No, no and no. http://www.mazdamaniac.com/images/smiles/icon_no2.gif

On older mid OBD-I cars, until right up to the end of the OBD-II, the crank angle sensor was one of two signals used to determine ignition timing. The other was typically on the distributor or camshaft.
Now it is done entirely by statistical prediction.
The e-shaft position plate is a really nifty way to get crank angle, but the engine wouldn't fire at all if any of the teeth were bent or missing because the PCM will go failsafe. It is really cranky about that (no pun intended). You can really toast a rotary engine under load with dodgy timing.

I'd be interested to hear what vehicle Simo is talking about, however.

hmm, this is interesting I'm going to look into this

Ahhhh I though the poor gas mileage and lower hp were contributed to the reprograming of the ecu so the engine runs rich? I thought Mazda did this to keep the cat from burning out?

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.

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...

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...

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.

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.

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...


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.

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?

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

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...

I get those numbers.

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

Ahhhh I though the poor gas mileage and lower hp were contributed to the reprograming of the ecu so the engine runs rich? I thought Mazda did this to keep the cat from burning out?

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 balls. :eek: Got a Canzommer cz 1/2 and leaned it out and got it down to a minor spit of fire every now and then. :rolleyes:

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. :rolleyes: 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.

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

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.

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.

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

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.

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

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.

my Car is a Calibra 2.0 L 16 V naturally aspirated

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.


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.

my Car is a Calibra 2.0 L 16 V naturally aspirated
ok, thank you.

re-read MazdaManiacs post.

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 :)

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.

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

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 :)


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.

For instance why does the maf voltage vary from car to car,event to event?


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.

Thanks Zoom----- we live and learn. As I am not an expert I will take your word for it. So the MAF's are actually closer than what we oridgenally believed?
Actually this ecu is a work of art. Just not to us modders.
Olddragger

A work of art indeed.. in that its completely unfathomable except to the original artist ;)

Seriously, someone crack this nut for the good of all RX8 drivers.. please come up with an ECU solution that will still allow me to pass inspection when necesary. First person to do this will have a goldmine on their hands. I don't understand how this car passes emissions what with all the fuel dumping goin' on...

from experiance with fitting a haltech to a motor with a motronic style 60-2 trigger wheel the car can run with a number of different wireing configurations for the sensor and angle where it is trigered. in the haltech manual it states something along the lines of 'it wont run quite right' but the difference between right and wrong wasn't detectable to me. so it is possible the ecu will still work with something wrong it will just do things silightly out of sequence.

Has anyone checked what Simo requested? I'd like to know if he was right.

here is what is commonly called the trigger wheel for our cars. also known as the e-shaft position plate. remember the 20 brakes stomp reset also resets the eshaft position plate profile in the pcm memory.

http://www.rx8club.com/attachment.php?attachmentid=55065


Uh, 20 brakes stomp reset???!

And...

The trigger or synchronisation wheel on the Renesis engine is NOT a 60-2 teeth wheel (that's a Bosch standard), but has a more complex pattern : it's a 36 teeth wheel (teeth spaced by 10°) with 6 missing teeth at one place and 3 at another.
The tigger signal coming from the INDUCTIVE (Not Hall effect) sensor (also called Variable Reluctance Sensor) looks like this : TDC - 12 small pulse - wide synch pulse - 15 small pulses - wide synch pulse - wide synch pulse - ... (repeat)

If there was a signal problem, I guess the engine would not synchronise and probably would not start at all!

Source : MAZTECH Mazda Technician Training Manual, October 2003

If there was a signal problem, I guess the engine would not synchronise and probably would not start at all!


I write software for a living and have done some embedded software in the past (the ECU is embedded software) so I have some experience with similar systems. A lot of whether it won't start or how bad it would run will depend on the error correction / tolerance that is programmed in. No sensors are 100% perfect so there must be some tolerance for a missing pulse. If there was was no expectation that a missing pulse could occur there would be no need for any synch pulse at all as the ECU could always assume that it's pulse count was 100% accurate.

What we don't know is the error correction just to reset the ECU's computed position when it sees a synch pulse? (i.e. the ECU thinks that it has seen 14 pulses and then the synch pulse comes along and it just goes with that) Or does the ECU keep some sort of count of how often it sees a missed pulse condition and if they occur too often (x missed pulse conditions in y revolutions) it shuts downs or goes into "limp home" mode. Or perhaps it doesn't care about a single missed pulse condition but only if it misses 2 or more pulses in a revolution. We won't know unless we get one of the Mazda software engineers posting here or somebody reverse engineers the ECU (not an easy task).

Did anyone ever try this? This would be a trivial measurement for an electrical engineer (like me!) as long as you could find the sensor and probe it without a belt or pully-wheel tearing all your fingers off. Does anyone have a picture of the sensor position in the RX-8?

Fortunately for me I am getting 17+mpg with 1700 miles on my RX-8 so I'm not worried about mileage, but I am curious about the reasons behind the cars getting 12 to 13mpg.

A 220hp car that gets no better mileage than a Ferrari Modena is just plain wrong .


My 6 speed MT is rated at 238bhp, after the downward adjustment by Mazda (from 250bhp).

Am I correct?

do you guys like mustard or mayo on your balonie sandwich? :molepoke:

This is all interesting. I was hoping someone would come forward having looked into this for Simo.

I average about 17.5 to 18mpg, so I frankly feel little motivation to think about getting my hands dirty.

My 6 speed MT is rated at 238bhp, after the downward adjustment by Mazda (from 250bhp).

Am I correct?

You are correct. Your car is rated at 238bhp. :FIREdevil

if it didnt get the signal it was "expecting" it wouldnt run period.
I totally agree. It probably wouln't even start.

The sensor is located at the bottom front of the engine. Looking at the crankshaft pulley, it's right behind at the 4 o'clock position. Should have a 2 wire connector. It's only held in by one bolt. When looking at the sensor, you should also be able to see the teeth of the trigger wheel (right behind the pulley). Book says the stand alone sensor should read 950-1250 ohms at room temperature.