DIY_EFI Digest Saturday, 7 December 1996 Volume 01 : Number 374 In this issue: Re: Flywheel/Encoder patterns Re: Flywheel/Encoder patterns Flywheel encoder patterns Engine braking???? Injector duty cycles See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: Mazda Ebrahimi Date: Fri, 06 Dec 1996 21:26:36 -0500 Subject: Re: Flywheel/Encoder patterns Jeffrey Engel wrote: > > > Subject: Re: Flywheel/Encoder patterns > > From: Kalle Pihlajasaari > > > Hi There, > > An encoder giving absolute crank position would implicitly supply an > interrupt when the position changes value. Reading crank position directly > means you wouldn't have to fool with timers or counters to derive it. You'd > also know exactly what the position is upon start-up without having to store > the last known position info upon shutdown. No way around the cam sensor tho > that I can see. The only real world advatage I see to the encoder is quicker starting with lower emissions. Updating the degree count takes very little time in the processor. We still have to employ a timer to calculate RPM, right? ------------------------------ From: Kalle Pihlajasaari Date: Sat, 7 Dec 1996 07:32:06 +0200 (sat) Subject: Re: Flywheel/Encoder patterns Hi Snake, > >>An encoder giving absolute crank position would implicitly supply an > >>interrupt when the position changes value. Reading crank position directly > > >>means you wouldn't have to fool with timers or counters to derive it. > You'd > >>also know exactly what the position is upon start-up without having to > store > >>the last known position info upon shutdown. No way around the cam sensor > tho > >>that I can see. > > > >Why not just have an encoder or sensor on the cam if you can get enough > >resolution? > > Kalle has a good idea -- some sort of retrofit device in a distributor > housing that encodes off the cam. This would work great *IF* you could get > rid of all the mechanical slop between the crank and the encoder, like > timing-chain stretch and cam/distributor gear backlash. I was thinking for 'no-brainer' retro applications one could just add a viscous brake to te shaft so after the first 20 degrees the units would then be at the extreme limit of the backlash. Problem is extra wear on components from the drag and getting something that will work at all engine speeds, perhaps something electromagnetic like a Tacho generator (plug it into your Tacho display also) You would have to go with multiple coils to keep things simple but might be able to keep the old dizzy in the boot (trunk). Getting this to work with the fuel system would take some doing but if you make your own into the existing harness you could swap the old unit back again using the old 35 tooth sensor if you get stuck in vancouver or something. Cheers *<<<-| - -- Kalle Pihlajasaari kalle@xxx.za/ip Interface Products P O Box 15775, DOORNFONTEIN, 2028, South Africa + 27 (11) 402-7750 Fax: 402-7751 http://www.ip.co.za/people/kalle ------------------------------ From: Roger Feingold Date: Sat, 7 Dec 1996 05:35:29 +0000 Subject: Flywheel encoder patterns Been following your discussions and I was wondering if you have a sensor for your application. If you have an engine operating at redline, the crankshaft pulse rate might be beyond the response of the sensor, especially if you have 180 or 360 pulses per revolution. ------------------------------ From: talltom Date: Fri, 06 Dec 1996 22:00:48 -0800 Subject: Engine braking???? A friend of mine has a 96 chev 3/4t 4x4(with a 350) and just got back from a hunting trip. This guy was a GM line mechanic for 20 years and has owned his own shop for over 15 years, and he insists that his new truck does something so that once the brake is tapped going downhill it will not under any condition gain speed. Neither he or the other mech can figuire out why, but both swear to it. My question is is it possible that the guys at ac-delco have rigged things to retard timing to the point that the compression stroke would be infringed up on as necessary for deceleration??? Makes me wonder if some wise ass has done a little abs system interfacing here???? I realize that some of the company guys have non-disclosure agreements to deal with, but I'd appreciate as much insight into this as is pheasible! ------------------------------ From: Roger Feingold Date: Sat, 7 Dec 1996 05:53:26 +0000 Subject: Injector duty cycles I'm working on sizing injectors for a '88 2.8 V6 MPFI. Does anyone have experience with the max duty cycle when at WOT and redline? My computations show stock 16 lb/hr injectors will be maxed out by the time the engine hits 5000 rpm and 12.6:1 A/F. Also, has anyone correlated the O2 sensor voltage vs. A/F ratio? Thanks, Roger. ------------------------------ End of DIY_EFI Digest V1 #374 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".