Rev Limiter circuit

[Lee Speakman]

Hi, im new here!

My names Lee and Im studying Electronic Engineering At Liverpool University (England)

We plan on entering the Formula Student formula next year, ive been tasked to do a home brew engine managment system if feasable, or just some kind of data logger....
But that is next year, this year im developing a PIC based Digital dash for automotive applications.

So for ive got all the functions working, RPM, SPEED, Oil temp, shift lights etc....

The next part of my design is to include an RPM limiter. I already have the code working so when the RPM rises past a user defined limit a logic 1 is outputted on one of the pins.

I want to use this to limit the engine RPM. Im thinking along the lines of shorting out the 'contact' breaker or on more modern systems the EDIS module. This would cause a smaller L(di/dt) which would cause a weaker spark. I think im on the right lines but I cant find any information anywhere.

What should I use? Thyristors, and what resistors etc.

Sorry about the long rant, any replys will get a virtual beer from me!

Cheers - Lee Speakman

[Lee Speakman]

Hi, im new here!

My names Lee and Im studying Electronic Engineering At Liverpool University (England)

We plan on entering the Formula Student formula next year, ive been tasked to do a home brew engine managment system if feasable, or just some kind of data logger....
But that is next year, this year im developing a PIC based Digital dash for automotive applications.

So for ive got all the functions working, RPM, SPEED, Oil temp, shift lights etc....

The next part of my design is to include an RPM limiter. I already have the code working so when the RPM rises past a user defined limit a logic 1 is outputted on one of the pins.

I want to use this to limit the engine RPM. Im thinking along the lines of shorting out the 'contact' breaker or on more modern systems the EDIS module. This would cause a smaller L(di/dt) which would cause a weaker spark. I think im on the right lines but I cant find any information anywhere.

What should I use? Thyristors, and what resistors etc.

Sorry about the long rant, any replys will get a virtual beer from me!

Cheers - Lee Speakman

[Lee Speakman]

P.S I think I may of met some of you. Was a couple of years ago, i think you was all holding an event at Brutingthorpe. We was camped in the same site as you, Meadow Brooks rings a bell with the Lodges. and the lake.

Some great machines. I was there with some old Fords.

When this dash is done its going in my 1974 Mk1 Escort that ive just restored with fuel injection http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[Luis Martinez]

Hi, to do the rev limiter circuit you have to interrupt the current going to the primary winding of each spark plug, this is quite difficult becuase the high voltages driven and a perfect synch with each stroke. You also have to take a look to the inverse voltajes produced when the winding is switched off, some some power diodes will be needed.
I'm right now developing a programable ECU for our F-SAE car.
Good luck.

[raska]

You could use your signal to say the normally low side of the power supply for your ignition coil drivers (ignitors, power transistors, etc) and cut ignition that way so as to avoid the problem Luis talks about above which is on a similar idea to your EDIS manipulating idea. In testing I can imagine many improvements you could start to play with to get a very solid running engine at the limit, that has excellent response to the start of motion.

[Dan G]

Lee, you should check into the Megasquirt forums www.msefi.com (http://www.msefi.com) and look up their info on EDIS systems and rev limiters. They should be able to answer some of your questions either for your homebrew EMS, or just convince you to buy a Megasquirt and make your life easier (it can control an EDIS ignition with minimal extra effort).