DIY_EFI Digest Friday, 6 September 1996 Volume 01 : Number 263 In this issue: Condensor/Capacitor for Ignition Coil RE: Re: hi compressions: wasDIY_EFI Digest V1 #258 RE: Ancient History RE: Electronic Ignition RE: Ancient History RE: Electronic Ignition RE: Multispark ignition "computers" RE: Ancient History Re: Knock sensor spectrum? RE: Re: hi compressions: wasDIY_EFI Digest V1 #258 re: Electronic Ignition Re: Ancient History Sequential VS Batch fire systems Water Injection Re: Ancient History Re: Sequential VS Batch fire systems Re: hi compressions Re: Ancient History Re: Water Injection Re: DIY_EFI Digest V1 #262 troubleshooting a taurus Re: hi compressions: wasDIY_EFI Digest V1 #258 Re: troubleshooting a taurus Re: troubleshooting a taurus See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: Kalle Pihlajasaari Date: Fri, 6 Sep 1996 12:22:51 +0200 (sat) Subject: Condensor/Capacitor for Ignition Coil Hi All, Long discource on Points capacitors. Steve Ravet wrote > "Tony Bryant" Wrote: > | Does the ignition condensor/capactitor serve any function > | other than to reduce arcing across points? Do I need one > | if I switch using a transistor? (with 400V zener clamp) > | > | Facts, not theories, please.. > | > | *********************************************************** > | * "Insanity is the only sane response to an insane world" * > | * >> bryantt@xxx.nz << * > | *********************************************************** > > Are you talking about electronic ignition or point ignition? I've never > actually worked on a point ignition (not that old), but I'm pretty sure the > condensor stores a charge, which is discharged thru the coil to make a > spark. That is CD (capacitive discharge) ignition. Electronic ignitions > usually charge the coil primary during the dwell period, interrupting the > charge causes the field to collapse and generate a spark, no capacitor > needed. HEI ignitions (from GM) are electronic, but have a condensor. The > only purpose of the condensor is noise suppression for the radio, however. > The car will run fine without it. There are a few things getting mixed up here. We have the oldie Ignition coil system that stores the spark energy in the magnetic field of the SOFT iron in the middle of the coil the energy is not stored in the windings (primary or secondary) but is charged or discharged using these windings. The Capacitor Discharge Ignition systems store the energy in the potential of a capacitor and they are ususally charged to a higher than battery voltage with some sort of chopper circuit in high energy devices otherwise you need a large capacitor and a low impedance coil usually a standard 9 Volt ingnition coil, the high voltage CD systems can use smaller high impedance coils with much less Iron in them as they do no want to store the energy in the core, they want the spark when they dump the cap into the coil not when the field collapses. The electronic points system is a standard Mag storage system with just a transistor switch to save on contact errosion on a set of points. There is also a high frequency system used in some cars that makes use of a Ironless low impedance coil and drives it with a high frequency to get multiple sparks during the time the distributor rotor is pointing at the cylinder starting at the firing point this means that turbulence cannot cause a misfire. ===== NOW ===== That little capacitor in the Mag store systems across the points OR the transistor switch. It is required. Back in the Boys Brigade {similar to scouts} when I was an ignorant 11, I took an instructor to task about it being only for suppression but he maintained it was for storage (we were both wrong). I was so cock-sure that we ended up trooping out to test this on the instructors car and sure enough it would not run without the cap in place (big blow to my ego). Later when styding 1st year Circuit theory at university we used the Ignition coil and Capacitor TANK cicuit as an example for damped occilation calculations. The Capacitor and coil form a resonant circuit which does not allow the magnetic field to collapse too fast. The two results of a too fast collapse are firstly that the voltage on the coil primary may rise to the point that it arcs across the points, this will cause a sustained current in the primary and will result in too slow a discharge of the magnetif field and hence a low voltage long spark. The other result you will find in the case of no points (or transistor) arcing is that the spark will be too high a voltage and will flash over in the insulation inside or outside the coil and cause the spark to be quenched before it has a chance to ignite the fuel-air mix. Plug lead inductance can cause the voltage to arc first inside the coil before your real fast spark even gets to the plugs. ===== cut ===== The suppression capacitor is the one you often see attached to the B+ terminal on a Alternator and is to get rid of the alternator whine from the radio &c. If you want a faster rise time and higher voltage shorter striking spark you can try using less capacitance and the rise time will be reduced, you can try two capacitors in series (buy two at the same time othewise you may exceed the voltage rating of one) or if you think that a lower strike voltage is enough you can use two capacitors in parallel. Remember that all of this only matters until the arc is formed at the spark plug at which point you have a constant energy discharge that will dissapate the stored magnetic field at a much lower sustaining voltage of about 2-5kV whilst the striking voltage is between 8 and 16 kV. Cheers - -- Kalle Pihlajasaari kalle@xxx.za Interface Products Box 15775, Doornfontein, 2028, South Africa +27 (11) 402-7750 Fax: +27 (11) 402-7751 ------------------------------ From: Mark Pitts Date: Fri, 6 Sep 1996 11:51:36 +-200 Subject: RE: Re: hi compressions: wasDIY_EFI Digest V1 #258 - ------ =_NextPart_000_01BB9BF1.0F3CFF60 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable You are better off with oval pistons, seeing as pistons cant turn, and = makes the head a much better shape for fitting multi valves into , or = just 2 big valves, but remember guys.... If you want revs as well = (which, I don't think many of you Americans do... (cubes don't make = revs)), you need small low mass valves so that they can close in time! Here is a silly twin spark idea: =20 If you get my drift (or for that matter....... My email works :)) Mark - ---------- From: SRavet@xxx.com] Sent: Friday, September 06, 1996 1:17 AM To: diy_efi@xxx.edu Subject: re: Re: hi compressions: wasDIY_EFI Digest V1 #258 Daniel Ridge Wrote: | Todd's right about chamber shape and flame proopgation. Multivalves = are a | hack around the hard limits that geometry places on things -- we're | constrained to have circular valves, it's tough to use real estate = well | when you are nesting circles(valves) in circles(cylinder(head)s). The | multivalve people didn't want multivales -- they really wanted=20 rectangular | valves :). This might be a dumb question, but why not non-circular valves? I guess = they wouldn't be able to spin. Is that a problem? I can see corners = being=20 bad, but what about a nice oval shape? - --steve Steve Ravet sravet@xxx.com Baby you're a genius when it comes to cooking up some chili sauce... - ------ =_NextPart_000_01BB9BF1.0F3CFF60-- ------------------------------ From: Mark Pitts Date: Fri, 6 Sep 1996 11:54:32 +-200 Subject: RE: Ancient History To an Englishman, these figures are crazy! How many ponies are you getting out of these engines? Mark - ---------- From: SnoMo1@xxx.com] Sent: Wednesday, September 04, 1996 5:53 PM To: diy_efi@xxx.edu Subject: Re: Ancient History Gentlemen, I have been on this list for some time now, and have found your discussions informative, and interesting. This latest thread (discussions of gas milage from a big block) has finally prompted me to ask a question. Why is it a 3500 lb big block car can get 12mpg when on the other end of the weight (and size) spectrum, my parents have a 14,000 +lb motorhome powered by a 454 chevy (tbi), with ovedrive, 5.13 ? gears, 20" wheels (rim dia) , and the areodynamics of a house, and still get 10-11mpg on the highway. And, when pulling a towed 3700lb vehicle (Brono II 4x4) they still get 8-10mpg. This has been documented over 10's of thousands of miles. And yet, if I buy a full size truck with 4-wheel drive and a 5.0 to 5.8 litre V-8, I can only excpect 16mpg? Do you think that possibly many vehicles are being over-geared? I recently changed the gears on my 2.8 L ford ranger from 3.73 to 4.11 and actually saw a slight increase in mileage. I think this was cause by always having the foot to the floor. Now, the engine revs higher, but I notice the pedal isn't constantly kissing the carpet. And, by the way I did take into account the odometer error after changing the gears (plural, 4-wheel drive makes changing gears a pain!). Just thinking outloud again, Mark ------------------------------ From: Mark Pitts Date: Fri, 6 Sep 1996 11:46:39 +-200 Subject: RE: Electronic Ignition Come on now guys.... The cap on points is to stop arcing at the points, = and therefore erosion of the breaker terminals. If you take the cap off, = it all still works, but the contact breaker pads weld to each other, = then the distributor cam forces them apart, ripping the surface off one = side, this is generally considered BAD! CD ignition requires a much bigger cap, as it is the cap discharging = into the coil that gives all the 'bang', not the collapse of the mag = field.=20 Theory simplified: Transformers are AC. They induce a current in the secondary proportional to that in the = primary (by number of turns primary to no. turns secodary). Normal points ignition gets the coil 'saturated'. I.e. it has dc flowing = through it. This DC comes from the points. They bit that induces the = spark is when the points open, and the magnetic field no longer is = supported by the DC. Something has to give. The current would continue = to flow for a short time AFTER the points open, through plasma as the = points arc. This is taken care of by the condenser 'buffering' this = effect, by allowing current to flow for a short time thro' it, mean = while the points are sufficiently open for the relatively small back EMF = from the coil not to jump the gap, and the dielectric in the cap is also = strong enough to hold it.=20 So now we have a coil with a magnetic field that is about to collapse. = The back EMF caused by the collapsing field will try and go anywhere. = The points are now safe, they are open, with sufficient gap that arcing = wont happen there, and the insulator (dielectric) in the cap (condenser) = is strong enough to cope without breakdown, so the only other rout out = for all this energy is through the secondary (which has a hell of a lot = more turns, (if you want transformers which is what a coil is = explained.. ask) and therefor a lot more voltage, but less current, but = its volts that jump gaps (like spark plugs!). Cap discharge... charge up a big cap to hold the energy, instead of creating a stable mag = field. Connect this cap to a coil primary with a big mosfet or whatever you = fancy. Coils do not like building up magfields, they create BACK EMF to oppose = the current trying to flow through them. This back emf is also induced = on the secondary, but higher voltage, and this jumps the plug gap, = thereby giving a rout for the energy to dissipate. Before anybody kicks my ass... I know this isnt complete, and I know its = not all strictly correct, but if ya know that... I didn't write this for = you! This is quite good enough for most people to follow (I hope :)). Mark. - ---------- From: SRavet@xxx.com] Sent: Friday, September 06, 1996 1:24 AM To: diy_efi@xxx.edu Subject: re: Electronic Ignition "Tony Bryant" Wrote: |=20 | Does the ignition condensor/capactitor serve any function | other than to reduce arcing across points? Do I need one | if I switch using a transistor? (with 400V zener clamp) |=20 | Facts, not theories, please.. |=20 | *********************************************************** | * "Insanity is the only sane response to an insane world" * | * >> bryantt@xxx.nz << * | *********************************************************** |=20 Are you talking about electronic ignition or point ignition? I've never = actually worked on a point ignition (not that old), but I'm pretty sure = the=20 condensor stores a charge, which is discharged thru the coil to make a=20 spark. That is CD (capacitive discharge) ignition. Electronic = ignitions=20 usually charge the coil primary during the dwell period, interrupting = the=20 charge causes the field to collapse and generate a spark, no capacitor=20 needed. HEI ignitions (from GM) are electronic, but have a condensor. = The=20 only purpose of the condensor is noise suppression for the radio, = however. =20 The car will run fine without it. - --steve Steve Ravet sravet@xxx.com Baby you're a genius when it comes to cooking up some chili sauce... ------------------------------ From: Mark Pitts Date: Fri, 6 Sep 1996 12:12:29 +-200 Subject: RE: Ancient History A few points: for real serious stuff 2 injectors are good... 1 hi flo and 1 lo flo, = with the lo flo for tick over, and fine adjust the big injector. This = gives fine control at closed throttle, and the high flo is good for WOT. Running injects flat out can cause them to stick, and overheat, and burn = out the driver electronics. Mark - ---------- From: Sandy[SMTP:sganz@xxx.com] Sent: Thursday, September 05, 1996 3:39 AM To: diy_efi@xxx.edu Subject: Re: Ancient History > Once you go to full throttle the injector pulsewidth should approach >100%; basically the injector is on all the time. At idle and low RPM I'm not sure how close to 100% is good, I have the idea that is should = be less then that as that can lead to injector and driver overheating. ------------------------------ From: Mark Pitts Date: Fri, 6 Sep 1996 12:26:42 +-200 Subject: RE: Electronic Ignition Hey dude... right list already... we do the bang bit here as well as the squirty bit! Mark - ---------- From: GEORGE LERM[SMTP:GEORGE@xxx.za] Sent: Thursday, September 05, 1996 2:32 PM To: DIY_EFI@xxx.edu Subject: Electronic Ignition Hi Cool list! Does anyone know of any DIY_Electronic Ignition mailing lists. I would like to explore the options of experimenting with a distributorless ignition for my VW Beetle. Any suggestions,help or comments would be appreciated. ------------------------------ From: Mark Pitts Date: Fri, 6 Sep 1996 12:28:13 +-200 Subject: RE: Multispark ignition "computers" Speak to me later... Ive got some friends into 3.5s I can chat to... who race on the strip, and go offroading! Mark - ---------- From: Fredrik Jeppsson[SMTP:fredrik.jeppsson@xxx.se] Sent: Thursday, September 05, 1996 11:29 PM To: diy_efi@xxx.edu Subject: Multispark ignition "computers" Hello from Sweden, I am considering upgrading the stock Lucas/Bosch ignitiion in my 1988 EFI Range Rover (3.5 liter ex buick V8). I would really appreciate some opinions and words of experience on the performance / smoothness improvements after adding one of those boxes between the trigger device and the ignition amplifier. I am also interested in the effect of performance coils marketed by the same companies (Jacobs, MSD and others). Fredrik Jeppsson * FAE, Embedded development tools * * Nohau Elektronik AB, Malmoe, Sweden * * * * 1988 Range Rover EFI * * 1990 Citroen XM V6 * ------------------------------ From: Mark Pitts Date: Fri, 6 Sep 1996 12:14:39 +-200 Subject: RE: Ancient History Well it was basically a pipe with the throttle plate in it, and a wick = hanging out of the float bowl... and they used to work fine... (1920's) :) Mark - ---------- From: = RABBITT_Andrew@xxx.au] Sent: Thursday, September 05, 1996 10:57 AM To: diy_efi@xxx.edu Subject: re: Ancient History >In that case, how did the early wick carbs work? Never seen one! I would guess that since they're not around now, they=20 didn't (work, that is!) ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Fri, 6 Sep 1996 07:12:17 -0500 Subject: Re: Knock sensor spectrum? >At 03:16 PM 9/5/96 -0500, you wrote: >>>How about posting it to John's FTP site? >> >>Be glad to .... what's it?? >> > >The site address (at last recollection) > >ftp://efi332.eng.ohio-state.edu > >Place the files in the 'Incomming' directory > >Sandy > Okay, did it !! Don't know if I did it right -- was I supposed to have left a note or something about what I transferred to 'incoming' ? I transferred two files, for all what's interested: (Youse can log onto the above ftp site and xfr stuff out of the incoming directory). spra039.pdf the data on the k-knock sensor using a TMS320 DSP. caldemo.zip Mike Wesley's demo program of his 'calibrator' for the Ford EEC-IV. Tom ------------------------------ From: Mark Pitts Date: Fri, 6 Sep 1996 14:21:45 +-200 Subject: RE: Re: hi compressions: wasDIY_EFI Digest V1 #258 Oops diagram didn't work... if anybody wants to see my idea... ill see = if I can attach it to a mail again! Mark - ---------- From: Mark Pitts[SMTP:saxon@xxx.org] Sent: Friday, September 06, 1996 1:52 PM To: 'DIY EFI'; 'SRavet@xxx.com' Subject: RE: Re: hi compressions: wasDIY_EFI Digest V1 #258 You are better off with oval pistons, seeing as pistons cant turn, and = makes the head a much better shape for fitting multi valves into , or = just 2 big valves, but remember guys.... If you want revs as well = (which, I don't think many of you Americans do... (cubes don't make = revs)), you need small low mass valves so that they can close in time! Here is a silly twin spark idea: =20 If you get my drift (or for that matter....... My email works :)) Mark - ---------- From: SRavet@xxx.com] Sent: Friday, September 06, 1996 1:17 AM To: diy_efi@xxx.edu Subject: re: Re: hi compressions: wasDIY_EFI Digest V1 #258 Daniel Ridge Wrote: | Todd's right about chamber shape and flame proopgation. Multivalves = are a | hack around the hard limits that geometry places on things -- we're | constrained to have circular valves, it's tough to use real estate = well | when you are nesting circles(valves) in circles(cylinder(head)s). The | multivalve people didn't want multivales -- they really wanted=20 rectangular | valves :). This might be a dumb question, but why not non-circular valves? I guess = they wouldn't be able to spin. Is that a problem? I can see corners = being=20 bad, but what about a nice oval shape? - --steve Steve Ravet sravet@xxx.com Baby you're a genius when it comes to cooking up some chili sauce... ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Fri, 6 Sep 1996 07:46:40 -0500 Subject: re: Electronic Ignition >"Tony Bryant" Wrote: >| >| Does the ignition condensor/capactitor serve any function >| other than to reduce arcing across points? Do I need one >| if I switch using a transistor? (with 400V zener clamp) >| >| Facts, not theories, please.. [ snip ] >Are you talking about electronic ignition or point ignition? I've never >actually worked on a point ignition (not that old), but I'm pretty sure the >condensor stores a charge, which is discharged thru the coil to make a >spark. That is CD (capacitive discharge) ignition. Electronic ignitions >usually charge the coil primary during the dwell period, interrupting the >charge causes the field to collapse and generate a spark, no capacitor >needed. HEI ignitions (from GM) are electronic, but have a condensor. The >only purpose of the condensor is noise suppression for the radio, however. >The car will run fine without it. > A coil (inductor) stores magnetic energy. When a current is passed through it (maybe 4 amps for an auto coil) and then the exciting voltage is removed, the collapsing magnetic field effectively tries to keep the current at 4 amps -- impossible with no load -- so, the voltage reverses and goes to a very high value. That's not theory, it's fact. So, when points close, current begins to flow while magnetic field expands (this is why 'dwell' is important -- need time for the field to expand sufficiently). When field reaches its max, the current is also at its max. This is all done at the applied 12 volts (approx). The coil is an autotransformer (meaning the secondary and primary are the same winding). When the points open, the coil responds with a nasty reverse voltage (maybe 300 volts on ignition coil), which is stepped up by secondary to approx 100 times that amount -- or until something arcs over (i.e. the plug). Now, it's the nasty 300 volts and attempted 4 amperes that is generated when the points open that generate a nice arc across them as they are opening, effectively doing an arc weld job on them. The capacitor's job is to absorb that transient voltage / current spike for a brief time, effectively bypassing it around your points and protecting them. Transistor and CD systems only use the points for switching an electronic circuit. There is no 'real' inductance attached to the points any- more -- therefore no real need for a cap. In fact, the cap will slow down the rise/fall of the signal, so it really should NOT be there. Tom ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Fri, 6 Sep 1996 08:06:18 -0500 Subject: Re: Ancient History >At 02:44 PM 9/3/96 -0500, you wrote: >>I think 12 mpg from a 455 is fantastic. Can't see how you get this >>good -- FI or carbed. What's your rear end ratio? >> >>tom > >OK, I new I'd get some mail when I said that, so for the curious, my car is a: > >'78 Trans Am >1970 455 2bolt main from a Bonneville >stored heads from that motor (10.25:1 cr too high) > [ snip ] I haven't dug up my stuff about VE and CFM and displacement, but seems to me that an xxx CID engine is a pump that always pumps xxx CI of air every two revolutions (assuming a 4-stroke). All that changes is the density (i.e. throttle closed = lower density A/F charge). And I thought that running R-E-A-L lean meant burning things up (I KNOW it does!). So, it takes a certain amount of fuel to just coast, much less make any power. Like I said, I haven't dug up the stuff, but I remember trying to mathematically anticipate 'good' mileage for my 351-W with a 3.50:1 ratio diff and was able to think 14 to 16 would be a reasonable goal with higher values theoretically feasible. So, how does one take a 400+ CID engine and get that kind of mileage unless he's running a 1.7:1 rear end (i.e. L-O-W r's) -- even if he had 100% VE ? Tom ------------------------------ From: Fred Francis Date: Fri, 06 Sep 1996 10:02:39 -0500 Subject: Sequential VS Batch fire systems RABBITT Wrote: .... All the applications that Robert J. Harris quoted in his original post were high-speed, high power applications, and sequential fuelling is not going to give you anything here. What sequential injection does give is better low speed, part load combustion stability leading to better real-world driveability. Would anyone like to comment on batch fire vs sequential injection systems? What are the real world advantages to each under specific circumstances? GM went to sequential systems recently on the new camaros and corvettes, WHY? Is anything really gained with a sequential system in terms of performance, efficiency or driveablility? ~~fred ------------------------------ From: scicior@xxx.com (Steve Ciciora) Date: Fri, 6 Sep 1996 08:26:15 -0600 Subject: Water Injection O.K., My daily driver (w/ 160k miles) is starting to knock unless I use premium. I think I'll put in a water injection system, but have a few questions. Can you dump in too much water? I plan on a winshield washer pump, and to have it vaccum operated. I will monitor the map signal and start pumping water when the engine gets below a certian vaccum. What I could do with another op-amp and a 555 is have the water pump come in at 50% duty cycle at one vaccum, and full on when it drops below another vaccum. I don't think I'll get carried away with using a pic chip, because I really don't know the relationship between engine load and knock. Would it be better to have the water controlled off throttle position? Thanks for your time, - -Steven Ciciora ------------------------------ From: Todd Knighton Date: Fri, 06 Sep 1996 09:05:39 +0000 Subject: Re: Ancient History > > I haven't dug up my stuff about VE and CFM and displacement, but seems to > me that an xxx CID engine is a pump that always pumps xxx CI of air every > two revolutions (assuming a 4-stroke). All that changes is the density > (i.e. throttle closed = lower density A/F charge). And I thought that > running R-E-A-L lean meant burning things up (I KNOW it does!). So, it > takes a certain amount of fuel to just coast, much less make any power. > > Like I said, I haven't dug up the stuff, but I remember trying to mathematically > anticipate 'good' mileage for my 351-W with a 3.50:1 ratio diff and was able > to think 14 to 16 would be a reasonable goal with higher values theoretically > feasible. > > So, how does one take a 400+ CID engine and get that kind of mileage > unless he's running a 1.7:1 rear end (i.e. L-O-W r's) -- even if he had > 100% VE ? > > Tom Tom, who cares about CFM, it varies too much too worry about. As well as your air fuel ratio is determined by mass not CFM. You only run 100%VE at close to or wide open throttle, unless you're turbo'd. At very light throttle conditions, your VE is determined by pressure AND rpm's. Sure, your VE still follows your torque curve, but your mass flow into the engine is very minimal at high vacuum situations. For example, running down the road at 100%VE, or WOT, you might be running 8 to 10 ms injector timing, where as at light throttle conditions, you might see 1.5 to 2 ms. Same RPM, different pressure, thus less fuel. Sure it's the same CFM inside the manifold, but prior to the throttle body (at atmospheric pressure) the CFM is much lower. Todd Knighton Protomotive Engineering ------------------------------ From: Dirk Wright Date: Fri, 6 Sep 1996 12:19:42 -0400 (EDT) Subject: Re: Sequential VS Batch fire systems On Fri, 6 Sep 1996, Fred Francis wrote: > Would anyone like to comment on batch fire vs sequential injection systems? > What are the real world advantages to each under specific circumstances? GM > went to sequential systems recently on the new camaros and corvettes, WHY? Is > anything really gained with a sequential system in terms of performance, > efficiency or driveablility? > Off the cuff, I'd say that batch fire vs sequential fire might not make much difference at very high revs, since the fuel injected to the closed intake ports woudl only sit there for a short time, while at low revs the sitting time is longer, which would reduce drivability. For a 4 cylinder engine at 6,000rpm, 180deg of crankshaft rotation takes 5msec. If the fuel is injected at the begining of the exhaust stroke (intake closed, batch injection of 2 at a time, this is the "odd" injector), the fuel sits there for 5msec before the intake opens. At 1,000rpm the fuel will sit there 30msec. Assuming the evaporation and droplet enlargement follow an exponetial function of the general form y(t) = y(0)*e^at, and that the amount of fuel injected at the initial time y(0) is the same for each case (a gross simplification), and normalizing by letting a = 1, gives a simple expontial function. The value of e^0.005 = 1.005012520859 and e^0.030 = 1.030454533954. Which I calculate as only a 2.5% increase. Unless y(0) is very different for each case, then there isn't much difference between the two. Of course, this could be completely wrong..... **************************************************************************** Dirk Wright wright@xxx.gov "I speak for myself and not my employer." 1974 Porsche 914 2.0 "A real hifi glows in the dark and has horns." 1965 Goodman House **************************************************************************** ------------------------------ From: Todd King Date: Fri, 06 Sep 96 09:25:00 PDT Subject: Re: hi compressions <<< From: Todd Knighton Date: Thu, 05 Sep 1996 13:25:09 +0000 Subject: Re: hi compressions: wasDIY_EFI Digest V1 #258 John Faubion wrote: > Actually the big reason for multivalve chambers is more area is exposed > around the valve to flow fuel. Two small valves have much more flow > capacity than 1 large valve but is more expensive that manufacture. That's also what Yamaha though, they went to 5 valves to get even more flow. They did pick up flow, but on the F1 motors the 4 valve engines made more power still. Point is. It's not all flow, but combustion chamber shape and flame propogation as well. >>> Ahh, Yamaha's 5 valve with the lens-shaped comb. chamber. The 3 smaller valves maximize the use of the available chamber area plus expose much more total opening (perimeter) quicker than two (or one) larger valves, kind of like getting a free increase in cam ramp steepness. As Todd said, people were puzzled that the engine was down on power compared to the 4 valve; one symptom I heard about was that it liked a surprising amount of ignition advance, indicating a slow burn, although the chamber was "engineered" for a fast burn. A benefit of the fast burn chambers is the ability to increase compression ratio ("outrun the fuse", as someone had recently posted) so the street version was set up for around 11:1 CR. I wonder if Yamaha had enough of a squish area in their chamber? All that valve stuffing may have cut down on the available squish area... Wish I had a job like that, designing chambers, playin' on the dyno, etc. Gee Todd K., need any help over there? :-) Todd Todd_King@xxx.com ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Fri, 6 Sep 1996 12:55:49 -0500 Subject: Re: Ancient History [ snip ] >> So, how does one take a 400+ CID engine and get that kind of mileage >> unless he's running a 1.7:1 rear end (i.e. L-O-W r's) -- even if he had >> 100% VE ? >> >> Tom > >Tom, > who cares about CFM, it varies too much too worry about. As well as >your air fuel ratio is determined by mass not CFM. > You only run 100%VE at close to or wide open throttle, unless you're >turbo'd. At very light throttle conditions, your VE is determined by >pressure AND rpm's. Sure, your VE still follows your torque curve, but >your mass flow into the engine is very minimal at high vacuum >situations. > For example, running down the road at 100%VE, or WOT, you might be >running 8 to 10 ms injector timing, where as at light throttle >conditions, you might see 1.5 to 2 ms. Same RPM, different pressure, >thus less fuel. > Sure it's the same CFM inside the manifold, but prior to the throttle >body (at atmospheric pressure) the CFM is much lower. > >Todd Knighton >Protomotive Engineering > So, you're telling me these mpg figures don't bother you? Tom ------------------------------ From: John Napoli Date: Fri, 6 Sep 1996 14:41:13 -0400 (EDT) Subject: Re: Water Injection Why not just one decarbonizing treatment to eliminate the accumulated goo? Run the engine at a fast idle and spritz in water from a spray bottle. Steam cleans it all right out. GM supposedly sells some snake oil that does the same thing. I seem to recall that good old ATF works the best of all. Then you won't need water injection. If you really want to go ahead with your design, I think you'll need to add a solenoid valve between the manifold and the pump to avoid high vacuum sucking the water right past. John On Fri, 6 Sep 1996, Steve Ciciora wrote: > > O.K., My daily driver (w/ 160k miles) is starting to knock unless I use > premium. I think I'll put in a water injection system, but have a few > questions. Can you dump in too much water? I plan on a winshield washer > pump, and to have it vaccum operated. I will monitor the map signal and > start pumping water when the engine gets below a certian vaccum. What > I could do with another op-amp and a 555 is have the water pump come in > at 50% duty cycle at one vaccum, and full on when it drops below another > vaccum. I don't think I'll get carried away with using a pic chip, > because I really don't know the relationship between engine load and > knock. > Would it be better to have the water controlled off throttle position? > Thanks for your time, > -Steven Ciciora > ------------------------------ From: talltom Date: Fri, 6 Sep 1996 12:28:17 -0700 (PDT) Subject: Re: DIY_EFI Digest V1 #262 > >From: RABBITT_Andrew@xxx.au >Date: Fri, 6 Sep 1996 11:30:32 est >Subject: re: Manifold/throttle bodys-ED:-) > >>In a message dated 96-09-04 16:06:27 EDT, wright@xxx.gov (Dirk >>Wright) >>writes: >> >>>I remember my old alfa with the spica mechanical injection had one >>>throttle per cylinder. pretty cool. >> >>So does the Lotus Turbo Esprit, but with elctronic fuel injection.... > >So do all EFI Alfa 33/145/146 boxer engines. > >Does anyone know what would happen if you joined all the chokes >together on the down-stream side of each throttle, kind of like >forming a mini-plenum for improving balance robustness at low throttle >openings, but still allowing the correct runner design and plenum >volume up-stream of the blades for WOT performance? > >Anyone tried this? Any theories? Yeah! I got a theory or two! Balance robustness should be tuneable without mini-plenums. The most I can see is a dinky vacuum line between ports to establish a average vacuum reference for the ecu. Any real tuner :-) would be more than happy to get out the mercury tubes to balance out their turbocharged, intercooled, nitrous injected, port throttled efi v-8 :-> Anybody know where I can get some rubber to put around the asphalt roller I'm going to need for rear tire? ------------------------------ From: "Mike Fahrion" Date: Fri, 6 Sep 1996 15:20:04 +0000 Subject: troubleshooting a taurus Sorry if this is a bit off subject. A coworker has paid an insane sum to a dealer to fix a problem which hasn't gone away - and I believe that it should be a simple EFI problem. The taurus has a very hard time starting after sitting overnite or over perhaps 8-10 hours. Takes a large amount of cranking with no firing, then stumbles slowly to life. Ambient temperature doesn't seem to have any effect. Computer reveals no fault codes, pump and filter are good. Isn't there a fuel accumulator which should maintain fuel pressure when sitting? If this was faulty would it allow pressure to drop - forcing the pump to charge the system again before it could start? Any insight would be appreciated TIA - -mike mfahrion@xxx.com ------------------------------ From: "John Faubion" Date: Fri, 6 Sep 1996 15:58:31 -0500 Subject: Re: hi compressions: wasDIY_EFI Digest V1 #258 > John Faubion wrote: > > > > Actually the big reason for multivalve chambers is more area is exposed > > around the valve to flow fuel. Two small valves have much more flow > > capacity than 1 large valve but is more expensive that manufacture. > > That's also what Yamaha though, they went to 5 valves to get even more > flow. They did pick up flow, but on the F1 motors the 4 valve engines > made more power still. > Point is. It's not all flow, but combustion chamber shape and flame > propogation as well. I agree in as much as with everything there is a break even point. Considering how crowded a four valve chamber is and how the two open valves affect each others flow, I can only imagine the problems with three open valves! John Faubion jfaubion@xxx.net ------------------------------ From: rickydik@xxx.com (RD Rick) Date: Fri, 6 Sep 1996 14:31:38 -0700 Subject: Re: troubleshooting a taurus mike wrote: >... >The taurus has a very hard time starting after sitting overnite or >over perhaps 8-10 hours. Takes a large amount of cranking with no >firing, then stumbles slowly to life. Ambient temperature doesn't >seem to have any effect. Computer reveals no fault codes, pump and >filter are good. > >Isn't there a fuel accumulator which should maintain fuel pressure >when sitting? If this was faulty would it allow pressure to drop - >forcing the pump to charge the system again before it could start? No accumulator, it needs to be a leak-free system, for obvious reasons. It does sound like fuel pressure has gone away. Assuming this is a V6, (you don't say, and you don't even say what year) there is a Shrader valve near the front where you can measure fuel pressure. It should be 35 psi at idle, and about 25-30 after sitting. Turning on the ign should cause fuel pump to run a couple of seconds, then stop. Try switching on and off once or twice before starting to see if that helps. EFI in my '86 Sable V6 has been almost flawless in 115K miles. Had to correct a weak idle recently by de-coking the air bypass. RD ------------------------------ From: "George Najarian" Date: Fri, 06 Sep 96 14:37:40 -0800 Subject: Re: troubleshooting a taurus Fuel pressure bleeds down overnight, but should build to normal in ~2 seconds or less. On Fri, 6 Sep 1996 15:20:04 +0000, Mike Fahrion wrote: >Sorry if this is a bit off subject. > >A coworker has paid an insane sum to a dealer to fix a problem which >hasn't gone away - and I believe that it should be a simple EFI >problem. > >The taurus has a very hard time starting after sitting overnite or >over perhaps 8-10 hours. Takes a large amount of cranking with no >firing, then stumbles slowly to life. Ambient temperature doesn't >seem to have any effect. Computer reveals no fault codes, pump and >filter are good. > >Isn't there a fuel accumulator which should maintain fuel pressure >when sitting? If this was faulty would it allow pressure to drop - >forcing the pump to charge the system again before it could start? > >Any insight would be appreciated > >TIA >-mike >mfahrion@xxx.com > George Najarian | '95 Ford Mustang GTS E/SP (14.21/100.81) najay@xxx.0/93) http://users.deltanet.com/~najay/ Team.Net Team OS/2 ------------------------------ End of DIY_EFI Digest V1 #263 ***************************** 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".