Post by thread:[EE]: Ignition design question

As the first step toward my traction control device, I want to build a circuit that will cut out cylinders with the push of a button. I want to use a pic that will count and pass along the pulses from the distributor points - to the ignition box, and determine which pulses to intercept and not pass along to cut cylinders. My distributor uses an armature and reluctor for triggering the ignition box. The wave form goes positive, then cuts straight down negative. I assume the ignition box looks for the negative edge. I need a circuit so that the pic can see the signal from the reluctor. What would be a good place to start with that. Then I need a circuit so the pic can trigger the ignition box. I can use the points input on the box for that, so all I need there is a good 12v square wave. What would be a good starting point for that type of circuit. Or perhaps, could the pic 'shunt' the signal from the reluctor? Would that be easier? Thanks John -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> >I need a circuit so that the pic can see the signal from the reluctor. >What would be a good place to start with that. Op-amp to amplify and square up the signal. >Then I need a circuit so the pic can trigger the ignition box. I can use >the points input on the box for that, so all I need there is a good 12v >square wave. What would be a good starting point for that type of circuit. Skipping ignition pulses isn't very fuel efficient. If it's injection, you could turn off the injectors on a cylinder-by-cylinder basis, and then save that fuel. There are also some interesting things that can happen with a slug of fuel-air mix in the exhaust system when the next cylinder fires.. :) >Or perhaps, could the pic 'shunt' the signal from the reluctor? Would that >be easier? You could probably take the signal away from the ignition, but don't take it away from yourself too! -- Dave's Engineering Page: http://www.dvanhorn.org Where's dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9 -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

> Skipping ignition pulses isn't very fuel efficient. > If it's injection, you could turn off the injectors on a > cylinder-by-cylinder basis, and then save that fuel. Also, overheats the catalytic converter (if so equipped). Possibly detonates it :) Even if not equipped with one, raw fuel air mixture hitting hot exhaust often detonates in the manifold blowing out the muffler (don't ask me hoe I know THAT one... ). Steve -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

> As the first step toward my traction control device, I want to build a > circuit that will cut out cylinders with the push of a button. > I want to use a pic that will count and pass along the pulses from the > distributor points - to the ignition box, and determine which pulses to > intercept and not pass along to cut cylinders. YEOUCH! DON'T CUT IGNITION! This is a sure fire way to erode your exhaust manifolds, piston heads, and valves (or apex seals if you're in a rotary engine'd vehicle). It'll also cause quicker failure of the catalytic converter, possible backfires, and premature wearing of the O2 sensor. It is FAR better to cut specific fuel injectors. Also make sure that the cut injectors are on opposite sides of the stroke at even/opposite distances on the crank to minimize crank flexing (and wear on the crank bearings). FWIW, My background was designing a computer for drag racing that had to run to 15KRPMs and account for engine knock, timing, and fuel injection control. It used an AVR micro and a Philips XA micro. -->Neil ------------------------------------------------------------------------------- Neil Bradley There'd be no more N'Sync if everyone had guns. Synthcom Systems, Inc. ICQ #29402898 -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

It's all true. If your engine is not fully upto temperature you will get a lean mixture when you turn the injectors on again due to the lack of fuel puddling which was there before. Obviously you have to re- enable the injector when it is turned off. Have you looked at retarding the spark to reduce power output? Martin {Quote hidden}> > Skipping ignition pulses isn't very fuel efficient. > > If it's injection, you could turn off the injectors on a > > cylinder-by-cylinder basis, and then save that fuel. > > Also, overheats the catalytic converter (if so equipped). Possibly detonates it :) > > Even if not equipped with one, raw fuel air mixture hitting hot exhaust often detonates in the manifold blowing out the muffler (don't ask me hoe I know THAT one... ). > > Steve > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestspam_OUTmitvma.mit.edu

Steven J. Devine wrote: > > > Skipping ignition pulses isn't very fuel efficient. > > If it's injection, you could turn off the injectors on a > > cylinder-by-cylinder basis, and then save that fuel. > > Also, overheats the catalytic converter (if so equipped). Possibly detonates it :) > > Even if not equipped with one, raw fuel air mixture hitting hot exhaust often detonates in the manifold blowing out the muffler (don't ask me hoe I know THAT one... ). Absolutely. Guys on motorcycles often hit the "kill button" on the handlebar, this cuts ignition for a fraction of a second, then when you put it back on that fuel detonates with a loud explosion through the exhaust system. I don't do it as it can bend exhaust valves on the cylinder head, but some young hoons do it to get attention from their buddies. If you want to control traction for anti-wheelspin might I suggest retarding the timing, you can still burn the fuel safely, but with the spark occuring when the piston is further down the bore there will be a big decrease in power. :o) More info needed?? -Roman -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu

Yes, retarding the spark is my preffered method of power reduction. Many Street Class drag racers, who must use street rires, use computers to tailor a 'soft' power curve. But too expensive and too difficult to make. Thanks ---------- {Quote hidden}> From: Martin Hill <KILLspameaxmjhiKILLspamNOTTINGHAM.AC.UK> > To: RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU > Subject: Re: [EE]: Ignition design question > Date: Thursday, March 22, 2001 1:18 AM > > It's all true. If your engine is not fully upto temperature you will get a > lean mixture when you turn the injectors on again due to the lack of > fuel puddling which was there before. Obviously you have to re- > enable the injector when it is turned off. > > Have you looked at retarding the spark to reduce power output? > > Martin > > > > Skipping ignition pulses isn't very fuel efficient. > > > If it's injection, you could turn off the injectors on a > > > cylinder-by-cylinder basis, and then save that fuel. > > > > Also, overheats the catalytic converter (if so equipped). Possibly detonates it :) > > > > Even if not equipped with one, raw fuel air mixture hitting hot exhaust often detonates in the manifold blowing out the muffler (don't ask me hoe I know THAT one... ). {Quote hidden}> > > > Steve > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email spamBeGonelistservspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body > > > > > > -- > http://www.piclist.com hint: To leave the PICList > TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu > -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

John Pearson wrote: > > Yes, retarding the spark is my preffered method of power reduction. Many > Street Class drag racers, who must use street rires, use computers to > tailor a 'soft' power curve. But too expensive and too difficult to make. John, is this really that hard? Surely the traction control will only be needed in a narrow rev-band near the motor's peak power. Say 6000-9000rpm for a 9000rpm redline motor? So what's hard about spark retard as your rev limiter, why not just add a preset delay to the signal, taking it from a few degrees BTDC to well after TDC. If you want to get fussy you can use the PIC to measure revs and adjust the spark delay accordingly, this is not that hard either as there are finite rates that an engine can accelerate and decelerate, and mechanical averaging. It would be pretty scary to selectively cut spark to some cylinders of a carburetted engine, you really risk flash and backfire and other scary problems. My racing motorcycle has inbuilt revlimiting, where the fuel injection AND spark are cut. Cutting spark and leaving fuel scares me... BOOOMMM!! :o) -Roman -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestEraseME.....mitvma.mit.edu