DIY_EFI Digest Sunday, 3 March 1996 Volume 01 : Number 063 In this issue: Re: u-bends Re: Hi-resolution Crank angle sensor Re: Ducted Fan Engine Re: Ducted Fan Engine See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: Sam Stoney Date: Sat, 2 Mar 1996 10:22:58 -0800 Subject: Re: u-bends >From: renns@xxx.com (Roger Enns) >Date: Fri, 1 Mar 1996 07:48:34 GMT >Subject: Re: Totally tubular, man > >> >>Where can I find mandrel bent "U" shaped aluminum and steel tubing for >>fabricating intake and exhaust plumbing? >> >> Dan Bocek > >Check out the exhaust section of your JC Whitney catalog. I've bought a lot of tubing from JC Whitney. They are by far the lowest price I've found but they are inconsistant in both delivery and tube wall thickness. Usually I get 20 guage, but ometimes it comes as 18 guage or thicker. The stuff is real good for test pipes but if you're goung to make something real nice and chrome it or something go to Aircone in Henderson, NV. These guys are much more expensive, though. They will also make up tapers and colectors. As far as other materials: Kinsler sells AL U-bends; funny thing, they're not cheap. Not a very good selection, either. I don't know of another source for AL and I'd like to know of one. Aircraft Spruce sells thinwall Stainless u-bends. Their # is 800 824 1930. They have all sorts of other materials in their catalogue, and they sell in small quantities, too. Anybody got a lead for TI tubing? Sam ------------------------------ From: "Paul E. Campbell" Date: Sat, 2 Mar 1996 16:56:53 -0500 (EST) Subject: Re: Hi-resolution Crank angle sensor Darrell A. Norquay wrote: > > As a matter of interest the Nissan 300 ZX Twin Turbo distributor has 2 > > sensors in it. One reads crank angle from the 360 lines on the disc and the > > other reads an encoded cylinder number from the 3 digit code. Japanese > > engineering! > > I was actually surprised that no one was doing this. (until now, that is) > This is a combination of a relative position sensor (the 360 lines) and an > absolute position sensor (the 3 digit coded portion of the wheel) There > are many examples of commercially available encoders of both types, but > to my knowledge there is no combination of the 2 used in industrial > position sensing. For a DIS type system, should be easy to substitute an > optical encoder for the guts of the distributor and get any timing accuracy > you want. Optical encoders are notoriously fragile, however, and you may > have a hard time finding one that will live a long and fruitful life in the > underhood environment... Okay..I didn't bother to mention this because I figured it was more trouble than it was worth but I was thinking in terms of optical encoders instead of magnetic ones because optical encoders are infinitely easier to work with for home construction because I can simply take a flat disk and drill hole patterns in it with much better precision than I think I could get away with making a toothed ring/gear. As for survivability, I think the only way to get an optical encoder to survive is to get it really good and sealed up. I'm thinking that the part that holds the interruptor modules should be part of a shroud that totally encases the optical encoder wheel except for maybe a hole at the bottom for drainage and a hole for the shaft that is turning. As for using the standard white/black markings, I don't think this is a good idea. Putting a hole completely through a disk lets you put sensors on either side and as long as the holes don't get clogged (easier to clean than munging up a nice optical encoder pattern on plain white paper) is probably just as easy to make. Also, standard emitter/receiver pairs are available for about $3 (check a Digikey catalog) that are already set up for that arrangement. The advantage of the magnetic encoder is that there's much less opportunity for the disk to get munged up since it is just a gear and will tend to centerfuge off anything that isn't sufficiently sticky (assuming you have it exposed). I don't know what your controller would think of having the encoder immersed half in water or some really nasty mud though. Now..to comment on a few other things that were said..the reason I was thinking in terms of totally analog PLL's instead of digital ones is that in analog, making up the various filters in the loops requires only a couple fairly cheap op-amps. Reading the resulting output can be done with counters. I was trying to come up with a way that the CPU could just read an external 8 bit register whenever it was ready and the hardware would handle most of the filtering before it got to the CPU. I figured a simple 1 or 2 pole filter on a PLL (which inherently cleans up noise and does the differentiation on the input signal) would be a cheaper and simpler route than doing all the data smoothing/cleaning in the CPU. You'll have to use an A/D on the error voltage then (okay..you can do slope integration and such but it's still A/D when you get down to it), but the loop does all the filtering. I was still trying to think in terms of something that could be easily constructed for the .1 kilobuck range. But..I just found out about the ADSP2181 this week so I may be tempted back into the totally digital filtering realm (the problem with the $10 ADSP2105 was the development system cost..the ADSP2181 development system is $90 which changes the picture significantly). ------------------------------ From: Mitsu16v@xxx.com Date: Sat, 2 Mar 1996 22:44:42 -0500 Subject: Re: Ducted Fan Engine In a message dated 96-03-01 09:43:50 EST, you write: >How about a free-piston engine to drive the turbine directly? Or, yet, a >combustion chamber (a la a real gas turbine engine) to generate hot gas? > > Pardon my density... but... what IS a free-piston engine? ------------------------------ From: Mitsu16v@xxx.com Date: Sat, 2 Mar 1996 22:51:28 -0500 Subject: Re: Ducted Fan Engine In a message dated 96-03-01 03:17:46 EST, you write: >There is available very powerful electric motors to be used in >electric r/c aeroplanes, those might be usable also. I think they >are available about same power levels as glow-plug model engines. Yeah there are some available that put out comparable levels of power.. but they're mainly equivalent to .049's and the like.. and when you put them in the high heat environs under the hood, the lifespan and the efficiency are going to go WAY down... :< Guess I'm gonna have to spring for that full on exhaust manifold and turbo system... :< Anybody got any other ideas about increasing the power?? I have heard there are some "run-what-ya-brung" type things to increase efficiency By tuning... ------------------------------ End of DIY_EFI Digest V1 #63 **************************** 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".