I Discovered Why Low Mpg And Low Hp
 

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.

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?

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 :)