Today while I was reading my Management text book I cooked up an idea for a duel guage setup of some kind. Basically I had to put the book down for this one.

If somehow you can measure the amount of time it takes to spark the ignition coils from when the crank sensor hits top dead center, and then take that amount of time and put it into some sort of equation for how fast the engne is rotating... ok now that I have you all confused, I was basically aiming for an idea of having a Timing guage on our cars; more specifically, a dual guage for both leading and trailing.

okok. I know you are all thinking why what how when and what the hell is wrong with this guy... I think this would be a very cool guage.

If it were possible to make a guage of this setup then we can tell what timing we are running at any rpm and also be able to tell if the engine is experiencing knock due to a "quick" timing retard.

I need an electrical engineer to answer this one cause I have no knowledge of building circuits from scratch but I bet this one would be easy.

 

If there was a gauge to tell how advanced or retarded the timing was from inside the cockpit, I'd buy it.

 

Heck ya.

I bet it can be done with the setup I said before and one (or 2) volt meters which measure from -12 to +12 volts

 

A typical distributor has a crankshaft position sensor and a TDC sensor. These combined with the signal from the coil can be obtained to calculate the timing. And with the proper electronics these sigals can be converted to display on a gauge. Good Idea.

 

OK so who wants to build the electronics???

 

First, knock never happens from timing retardation, it's advance that does the trick.

Second, the advance is going to be whatever it's told to be by the maps in the ECU. Get the programming and you'll know what it is at any combination of throttle position and RPM. If you're trying to control it with an aftermarket program, you already know what the advance is.

So what is the point of the guage? It's not something you can control without a Haltech or whatever. This is stuff that should be "tuned" on a dyno and you're done. What am I missing?

 

yeah a data logger for this would be great to do a base line setup for stand alone computer I have no Idea how to set that up yet

 

I think you are thinking too much.

This idea would just monitor the degree of timing from top dead center. If the timing guage takes a dip tward retard for no real apparent reason at full throttle then you can assume that the engine is experiencing some kind of pinging or knock (You see a retardation by the computer because the computer senses the knock and makes the timing retard).

No way would this guage save your engine from detonation or anything like boost creep... but it would tell us what the ig timing is at all times.

If you see a sharp retard for no apparent reason than you can assume the engine is having some knocking and you can let off before it knocks again, and again, and again and then hopefully fix the problem or buy fuel mods of some kind.

 

I'm sorta trying to do something along these lines.. So i'll toss my thoughts up in here..

From what I understand, the CAS only reports 30 degree increments of the e-shaft.. Tho, i believe one of these is as TDC... So, while you can't directly get the crank position, it can be interpolated...somehow..

From the speed at which the CAS reports positions, you should be able to determine RPM.. Or from the signal wire from the coils... Even if retarded/advanced, they should give the same RPM. just out of phase, but that shouldn't matter..

The spark timing would come directly from the signal wire on the coils.. I haven't checked yet.. but i believe this is a 0/+12V pulse train.

It may be possible to somehow feed this data into an actual computer... perhaps via the parallel port (after some circuit to make the signals friendly).. hmm

-Tesla

 

there are two outputs from the crank angle sensor. there is a home signal and another signal every 30degrees.

mike

 

OK so now we just need someone to design some sort of computer program or circuit to measure the timing......

 

I believe the TDC output comes every 180deg from the CAS. Run this into a PLL multiplier to bump the frequency by 180 (1 pulse per degree, compensated for RPMs). Use the TDC output to also clear a counter that runs off the frequency above. When the coil fires, latch the value of the counter. You now have the delta (advance) in degrees in digital form. Attach to display and away you go. You may need to pre-load the counter with an offset to compensate for fixed offsets or delays. It is left to the student to implement (I really hated when my profs said that...)

Henrik
87TII

 

I believe that the coils are inductors, if they are you could use the equation v=L di/dt which is also equal to -Ve^(-t/tau(subL), considering this when integrating you could determine the amount of time it takes for the inductor to fully charge. after this is determined, from the resulting current wave pattern the amount of time between the full charges can be measured. give me a day or two to figure out how to get a guage to read everything. laters.