Getting facts straight! (3/3)

[Greg Hermann]

>(continued from 2/3)
>
>I have no hard numbers to back up this contention, YET, but I suspect that
>if a port injected engine had MUCH BETTER fuel atomization than is
>attainable with current art injectors, and a much quicker fuel squirt--one
>timed with the high velocity flow of air in the port--that it would not
>only make more power AND have a lower BSFC at WOT conditions, but would
>ALSO want a mixture somewhat RICHER of stoich for maximum power than is the
>case with current art port injected engines! WHY?? evaporatin fuel on the
>back side of a hot intake valve allows fuel vapor to displace air--reducing
>output, whereas--getting finely atomized fuel into the cylinder, and not
>vaporizing much of it 'til after the I valve has closed not only avoids
>displacement of inlet air by fuel vapor, but takes full advantage of the
>heat absorbtion effect (as detailed above) during the compression stroke.
>- ------------------------------------------
>
>As to the best ECONOMY mixture--going lean of stoich tends to insure
>burning every last bit of the fuel, and thus improves economy. The limit is
>usually when one approaches a lean misfire condition. (Misfires waste
>fuel.) Better fuel atomization and distribution BOTH work to push this
>limit further out. Also--the basic  Otto cycle efficiency, even at WOT,
>improves with a leaner mixture. Good chamber geometry and good mixture
>turbulence during combustion push the lean limit further out, as well as
>allowing better efficiency through higher compression ratio (by avoiding
>pre-ignition and/or detonation). Furthermore-- leaner mixtures at part
>throttle (with a spark ignition engine) reduce pumping losses, improving
>economy even further at part throttle. SO--how far lean of stoich is best
>for economy--the answer is--"As far as you can get away with!"--not some
>set rule! It all depends on a large number of engine design factors.
>
>So--what are we left with that is magical about stoich? The facts that a
>stoich mixture is the point where a three way catalyst works best for
>cleaning up tailpipe emissions and that it is also the point where a
>standard EGO or HEGO exhaust oxygen sensor (as opposed to a UEGO WBO2
>sensor) switches its output. Period.
>
>In closing--I would like to say that this list will return to far better
>health once it finally get put onto a different server, and can FINALLY get
>off of the #$%^^&^*& digest mode--too many of the really knowlegeable
>people here have been driven into the lurk mode by the digest format!
>
>AND--the trick to getting good information off of the internet is the same
>as it is anywhere else in life--one has to learn to sort useful information
>out from BS!! There are always plenty of people in any field who are
>willing to spread BS indiscriminately, usually without knowing any better,
>but sometimes with premeditation and for profit! Good, old fashioned
>fundamental education taken together with the ability and experience with
>applying it is one of the most effective tools for accomplishing this
>sorting process!
>
>Unfortunately, high performance engines seem to attract more than their
>proportionate share of the BS and the profiteers (particularly the ones who
>feed on ignorance)!
>
>Although I am NOT going to be so bold as to say where, I WILL promise that
>there is a bunch of good information in this last series of posts--it's up
>to all of you to figure out where!
>
>Back to lurk mode, at least 'til we are off digest mode!
>
>Regards, Greg
>
>------------------------------
>
>Date: Mon, 6 Dec 1999 10:01:24 +0800
>From: dzorde at erggroup.com
>Subject: Re: Signal of AMC 16
>
>Mike, I had a similar problem trying to interface my Chev HEI to the
>aftermarket
>ECU, made the car undrivable as it saw multiple crossovers of the same trigger.
>Try something along the lines of.
>
>                    0.1uF    1k
>coil       ------||------/\/\/\/\/---------|--------------ECU
>                                                          <
>                                                          >  1k
>                                                          >
>                                                          |
>                                                        ----   15V zener diode
>5W
>                                                          /\
>                                                           |
>                                                         gnd
>regards
>
>Dan  dzorde at erggroup.com
>
>
>
>
>Date: Sun, 5 Dec 1999 00:56:23 -0500 (EST)
>From: Mike Comai <comai at expert.cc.purdue.edu>
>Subject: Ref. Signal off of AMC I6
>
>I am currently trying to get my first major retrofit up and running.  I
>have everything installed and when I try to start it the injector's don't
>fire.  I was told that I need a filter on the negative side of the coil
>and to feed the filtered signal into the Reference line on the ECM (which
>I am using a '747).  I was given a design for a filter which looks like
>this:
>
>------------------------------
>
>Date: Mon, 6 Dec 1999 10:14:04 +0800
>From: dzorde at erggroup.com
>Subject: Re: DIY_EFI Digest V4 #672
>
>I'm doing this on my current s/c set-up (although car is not yet driveable),
>anyway a blow off valve just venting of the air during idle and light cruise.
>Put your foot down, the valve shuts and there is instant 17psi boost.  Unlike a
>turbo, you don't get a pop when it opens, but more of a constant whistle as it
>lets a lot of air out unless wot.
>
>Due to the extremely hot air (currently don't have an intercooler yet) I'm
>reluctant to recirculate it through the intake filter (but due to the very loud
>whistle created by all this air veing vented in the engine bay I need to do
>something).  Can anyone see a problem with feeding the air from the blow off
>valve into the exhaust system before the muffler and quieten it down this way.
>The line could be fed in at 45deg angle with the exhaust flow.
>
>Dan  dzorde at erggroup.com
>
>
>Date: Thu, 2 Dec 1999 19:02:36 -0500
>From: "Jonathan Davis" <jfd125 at psu.edu>
>Subject: Re: KLUTCH!!!
>
>Another way to do this, perhaps would be a  large bypass valve that
>recirculates
>any boost until WOT.  Something like that would be intoxicating to drive -
>nice
>fat kick in the pants at WOT...
>
>------------------------------
>
>Date: Mon, 06 Dec 1999 02:19:16 -0500
>From: Chris Conlon <synchris at ricochet.net>
>Subject: re: Add-on systems which affect output pulse width?
>
>"Andrew Brownsword" <asword at telus.net> wrote:
>
>>  It seems to me that this could be problematic if the ECU was designed to
>>expect a particular voltage range and the stock airflow meter generated that
>>full range ... in other words there is no buffer for going beyond the
>>expected range of values.  This seems fairly reasonable for an N/A engine
>>since it is extremely unlikely that the car will have to deal with >1
>>atmosphere.
>
>I'm not going to get into this, really. You may very well run
>into problems, especially with ignition timing, when you try to
>trick an NA ECU into running much boost. (If you aren't
>reprogramming it, that is.)
>
>>  The alternative is to modify the ECU's output, which is a time dependant
>>pulse width.  It simply isn't possible to have full remapping control over
>>the output because by the time you know what the pulse width is, the time at
>>which you have to send it to the injectors has passed.  It occurred to me
>
>You can get very close, though, and very easily, in at least a
>couple different ways. This presumes you're running injectors a
>good bit larger than stock and will not need to lengthen the
>pulse. Take your basic HC11. Wire a switch (power mosfet most
>likely) in series with each injector drive circuit, watch for
>voltage drops, ground ref, etc. Control each switch via output
>compare line. Also wire up input compare lines so they can
>detect when the ECU is *trying* to fire the injector,
>independent of your switch's position. (If you have more than
>4 independent injector drive circuits, see 68332 instead.) Now
>you can easily read RPM and load, more or less, via input
>compares. You have a map, and for each rpm/pulse width point,
>look up a new pulse width. (Or just multiply by old injector
>size / new injector size, correct for short PW, etc etc.)
>Leave each output compare line (switches) on, until the ecu
>fires that circuit. You'll get an interrupt and time count
>via input compare. Calculate how long you want the pulse to
>be, program output compare to turn off at that time. When IC
>turns off again, take another interrupt, turn OC back on.
>
>You can update RPM and desired-PW info at each injector firing
>if desired. It is "behind reality" but not by much. Issues
>exist with p&h drivers, need a dummy load, etc, or just supply
>your own drivers. (Assorted details omitted, none too tricky.)
>
>I already have to do this (and more besides) for my semi
>insane supercharged MR2 project, ugh. Lucky for me the ECU
>already understands boost, timing retard, knock sensing,
>etc, it just needs a few white lies about airflow & injector
>sizes.
>
>
>Now I had some questions for you, since you seem to know
>Ford/Mazda stuff well. I did some searching for answers
>but got confused and set it aside. I'd like to get an
>MX-3 v6, and do some engine swapping. I've heard that a
>2.5l v6 from the MX-6 (or 626?) will basically drop in.
>Wasn't there a 2.5l *turbo* Ford Probe GT engine at one
>point? If so would it drop in w/o much work? Basically I
>think the MX-3 is cute and would get one if I knew I could
>grab a decent turbo engine (well, a whole front cut) from
>something and drop it in pretty easily. (Ignoring ECU hassles
>of course, got to have some fun!) I know there are aftermarket
>turbo kits, etc, but I was hoping for a factory turbo motor.
>Am I just real wrong or was there such a beast? I'm pretty
>sure there was a not-common MX-6 turbo... comments? Thoughts?
>
>   TIA,
>   Chris C.
>
>------------------------------
>
>End of DIY_EFI Digest V4 #678
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