Need help tapping into the Rx8 RPM signal
 

Ok so I have used the search button like crazy. I have read the Rx8 doesn't have a rpm signal wire. You have to tap into a coil, but it will only have 1/2 the signal. So you would have to tap into two wires. How IDK.

The reason I want to tap into the RPM signal is because I'm going to be running a shift light. Since I'm installing my SC I want to set the shift light to 7.5k/8k rpms.

Has anyone done this successfully and/or can shed some knowledge?

It would be easy if you had OBD2

Watcha mean?

Are you looking to just signal a red light / green light visible notification at various RPM points or do you need further integration?

An OBD2 reader running on an Android could do it very easily.

Well the shift light displays the RPM digitally. And I can set it to light up Red at any rpm range.

As far as an Android. Do you mean having something connect to the OBD2 and running it to a small tablet of some sort?

tablet or phone, yup. App could go full screen and show nothing but the RPM in a cool digital font in the foreground color of your choice with some basic parameters defined for when to change color / intensity.

Torque (and other apps) probably already have such a feature. It wouldn't take too much time to code one up for you if you had a reader if Torque and other apps were a dud.

yup, sure enough.

https://play.google.com/store/apps/d...ftLights&hl=en

The apps are pretty cool. But the last thing I want is something plugged into the OBD2 and a mount for a phone or tablet when I'm on the track. I found 2 guys on you tube that did it. I messaged them. Hopefully they get back to me.

Got this link from my boy Dave if anyone is ever looking for the same info.



Racepak.com • View topic - RPM Signal for G2X from RX-8

an ultragauge will give you a shift point, a beep and a will flash the display. It will also give you a lot of other information...

There's an easier, much better way.

1. Remove one of the bolts from the main crank pulley.
2. Replace this bolt with a stud that protrudes beyond the pulley.
3. Mount any functional Hall Effects Sensor in a way that the longer stud triggers the Hall Effects Sensor. (You need to fabricate a bracket for this sensor. Ensure that solid material is used, as thin walled brackets might vibrate too much and render the sensor useless)

You have an RPM pickup, without messing with any ecu wiring, coil wiring or anything that might cause an electronic problem.

I have done this as I use a Powermod Pro ECU for the main management, piggybacked onto the stock Delphi ECU, and the general purpose output from a secondary ECU to map the Pulse Width Modulated signal used in this case to control the pulse width at different RPM's regulating the boost control solenoid extremely accurately.

I have tried several external boost controllers, even some of the best in our racing cars, IE GReddy, etc, etc and they're all CRAP. I never have any boost spikes, boost dropoff or creep.

Best of all, no blown motors.....

Trust this helps

Greddy RPM adapter :uhh:

I'm with you on this one. A simple cheap bluetooth adapter on the OBD2 port and you're good to go. 100X times the useful info for a fraction of the price and labor.

Or use the VFAD circuit to turn on the light if you have an Accessport :)

Now that's novel. Great idea Dan.

So what if I was just looking for a straight RPM signal? Ie for the Profec e-01?

I know there's a GReddy adapter for it but it seems simple enough to fabricate your own adapter?

As far as searching the forums resulted, all I get is that the signals of either the leading or the trailing coils need to be combined. Does this mean I can just wire tap into each signal wire, combine them and feed them into the Profec e-01? The GReddy adapter seems to combine all 4 signals and requires a ground.

The vid above seems to indicate that the light goes off around mid-4000 rpm which makes sense if he only used the signal from one coil?

BTW the link for the RacePak doesn't seem to work anymore and a few quick Google searches can't seem to find any related page.

There is a wire for engine rpm. I spliced into it for mine. Ill have to look up the signal wire. It is in the install info for ark designs multi function dash.

There is??? I could've sworn I've looked over the ECU pinout several times and searches yield the same "signals need to come from coils, etc." Where did you find the wire? Can't seem to find any install info on the ARKdesign MFD (is it the MFD 1 or MFD 2?)

well I guess it could be coil based, but I didn't have to set it up. I just hooked it up and compared the rpm to my cobb it is dead on.

MFD1

Yes, it is needed for remote starters. The remote starter ECU monitors the RPM wire in order to determine when to kill the starter motor (on cars that do not have auto starter kills it is needed in order to not grind the starter when the engine starts).

Have not looked into it particularly, not do i know how are car interprets the signal 0-5v scale or more complex etc....

This is on my list of developments for another application, just cannot find the time to start.

Hmm could you tell me which coil you tapped? Does it matter which one you tap into? Does the MFD1 have a setting where you pick the engine size so it can "decipher" the signal?

As I understand it, there is no simple RPM signal from the ECU as all of that is done by the CAN bus. The ECU derives the RPM output for the gauge cluster (also probably to calculate ignition and fuel timing, but not 100% sure about this) via the crankshaft position sensor. The problem with the RX-8 crankshaft wheel is that it has a rather odd tooth pattern: 36-2-2-2 so it's not like I can hookup a simple tie in to translate the signal that does not cost as much as the GReddy adapter.

There is the option to add an extra Hall Effects sensor like mentioned above but that adds an extra sensor (hence more work to set it up along with the little wiring required).

Just wondering, what Hall Effects sensor can be used and where can I find them?