DIY_EFI Digest Thursday, December 2 1999 Volume 04 : Number 671 In this issue: RE: QNX Floppy Tools? (Was DIACOM) Re: Transients. Re:KLUTCH!!! Re: Data Acquisition Re:Transients See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Thu, 2 Dec 1999 02:28:52 -0800 (PST) From: Jon Watts Subject: RE: QNX Floppy Tools? (Was DIACOM) > From: "Jim Velasquez" > Subject: QNX Floppy Tools? (Was DIACOM) > > The QNX Demo Disk is one of my favorite examples of a small, > focused embeddable product! (That, and the Linux Router Project's > single-disk, run-from-ram concept). - ------------- QNX is way too expensive for any kind of hobbyist to use (thousands of dollars for a development license). The design is very simplistic (in a good way) but it mostly finds it way into video poker machines and such. What I'm surprised at is that there's not more talk of Linux on this list. By itself it could handle an EFI system and host it's own analysis software. With real-time Linux (www.rtlinux.org) this is now a certainty. Sooner or later someone will build a PC-104 (or smaller) EFI unit. This would be a great project, but by the time you're done you could easily have bought an Electomotive or MoTec setup. Unless Lego comes out with EFI sensors for the Mind Storm....... :) ===== Jon õ¿õ __________________________________________________ Do You Yahoo!? Thousands of Stores. Millions of Products. All in one place. Yahoo! Shopping: http://shopping.yahoo.com ------------------------------ Date: Thu, 2 Dec 1999 07:08:29 -0800 From: "John Dammeyer" Subject: Re: Transients. > >Date: Thu, 2 Dec 1999 09:43:31 +1300 >From: Tony Bryant >Subject: RE: Transients > > >> | 6) A richer mixture (i.e. more powerful) is needed to accelerate the >> engine. >> | Bollocks. Running a seriously rich mixture at say >> 1300RPM/0" vac, does not >> | help >> | the problem. Neither does serious amounts of dMap/dt. >> dTPS/dt helps a >> | little, >> | but not much. >> >> Then try going very lean, ahh, see, problem gets worse > >That because on your first 100% VE cycle after the transition, the >fuelling will still generally be set-up for the pre-transition >conditions. Leaner there, gives much leaner post transition. > I have experienced much the same sort of problem and also have that post Throttle Open Stumble. I use a dTPS/dt to increase the amount of fuel injected based on how large the dTPS/dt is. I also have a timer that runs for 1 second maintaining the longer pulse width but I still have a stumble of sorts. >> | ---------------------- >> | Having stated what I think its not, here's what I think it is: >> | 1) Fueling delays. The ECU not responding to changes in MAP as >> | quickly as the engine. The engine will respond on a cycle by cycle >> | basis, whereas an ECU and MAP sensor most likely will not. >> I don't think it's totally engine response on a cycle by cycle basis but maybe a lack of knowledge of how much extra fuel to pour in. Here's my quandary. My maximum pulse width is limited to 12.8 milliseconds at 7000RPM. So the dTPS/dt calculation can, at most inject no more than 12.8ms per cylinder for 'n' seconds after the throttle is snapped open. I suspect that the engine requires far more than 12.8ms of fuel at this point even though at 6600RPM I'm using that much to generate maximum horsepower. i.e.: theory says that at WOT and 95% VE that if the 12.8ms is enough at 6600RPM then it should also be enough at high dTPS/dt; yet it's not. So why? At 1200RPm each engine rev takes 50ms. Each stroke therefore takes 25ms. This means if I'm updating my TPS and therefore my Injector pulse width more often than every 25ms I should see the 12.8ms pulse width within one stroke at low RPM. That's not equivalent to a .25 to .5 second stumble that real life provides so why the stumble? This stumble is quite real, the engine can actually cough and almost stall if the mixture or the duration of the enrichment is too slow. My Jeep Cherokee, when the throttle is matted to the floor, has a brief brief pause before it winds up but it never really stumbles. Same with my SAAB Turbo (MAF sensor and turbo) so things are different. But in either case the FI handles the dTPS/dt without a real stumble before accelerating. What are they doing? Regards, John ------------------------------ Date: Thu, 02 Dec 1999 10:09:18 -0500 (EST) From: Andris Subject: Re:KLUTCH!!! > Date: Thu, 2 Dec 1999 01:50:53 EST > From: A70Duster@xxx.com > Subject: KLUTCH!!! > Could one use an AC clutch to engage and disengage the impeller. At idle and > cruise, the impeller doesn't turn, but for gettin' giggy, fire up the > "blower" and blow past the NIGHT RIDER!!!!! > > Can an AC clutch "hold together" when attached to a blower??? Granted, it would be a cool gizmo, and all, but I really don't think you'll gain anything by it. At the lower rpms and cruise, the blower isn't really working too hard, so your parasitic losses would be quite small. If you still want to do it, I doubt the AC clutch would hold. Making a WAG, I'd say the AC compressor might take max 20hp to turn (guessing since my timeslips are .2sec and 2mph slower w/ the AC). At full boost, I've heard that superchargers take 75+hp to spin. You would need something a bit stronger. A small puck/disc-style clutch (like in the drivetrain) should hold. Maybe something from a racing bike? Anyways, I've rambled enough, and don't think you'll see much gain. Andris Skulte Z28tt - 89 IROC T56 DFI Twin Turbo ------------------------------ Date: Thu, 02 Dec 1999 07:29:55 PST From: "scott christensen" Subject: Re: Data Acquisition Andris, This place sells PC data acquisition boards about as cheap as anybody: http://www.advantech.com/ But you will need several cards (and they add up $$$): PCL-711 DAS card to go in PC (or the 812PG is good too) PCLD-774 board for external connections (regular sensors) PCLD-779 amp board with isolation (thermocouple conditioning) Thermocouples open a can of worms. These suckers have very very small voltages that need externally amplified for generic PC A-to-D cards to handle. Additionally if you do not get an amp board that electrically isolates each thermocouple from each other (i.e. stay away from "single ended" types), then if you connect the thermocouples' tips together electrically (by touching multiple tips to the same conductor, the engine in this case) then it will "short out" and your system won't work. Been there done that. Might be cheaper to buy an external "box" designed for reading thermocouples and reports the temps back to the PC via a serial port. I've seen them advertized in the back of electronic magazines. Good luck. - -scott ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com ------------------------------ Date: Thu, 2 Dec 1999 10:59:46 -0600 From: "G. Scott Ponton" Subject: Re:Transients First the disclaimer. I tend to speak in a way that some people have a problem with. I can come across as being condescending and the like. This isn't my intention so I hope you will all take this for what it is worth. I am putting on my flame retardant suit and placing my CSH nearby just in case they are needed. I may be completely wrong here as it has been nearly 25 years since I studied fluid dynamics on a daily basis. I think, through experience and experimenting, that many times the actuality of the interaction of air flow, fueling, intake tract sizing and cam specs is severely misunderstood. VE is also many times misunderstood as to how it relates to the engine during a variety of operating speeds and conditions. There is no way to give a short and simple answer to all the questions that come with this subject. All of the points made have an effect and they are all tied together to effect the throttle response of any particular engine combination. But ...... ( knew that would be there didn't y'all) The first step in understanding this is simpler than it seems. Throttle response = how quickly we can go from an idle condition to a full power condition, Correct? If we "fix" certain variables, air density and humidity, for the sake of the argument, what is the difference between idle conditions and full throttle conditions in the combustion chamber and intake manifold? How does intake tract volume affect this? How does the cam spec effect it? Where does rod/stroke ratio come into the picture? What affect does compression ratio have on this? In carburated apps how does the size of the carb affect this? Each of these questions is interconnected. Each has an effect on the "total" picture. They all need to be addressed in turn and yet at once. VE is a curve that is related closer to the rod stroke ratio and cam spec than anything else. Yes, tuning the intake runners, exhaust manifolds/headers for size and length has an affect too. It's just not as large an affect as the proper cam selection for each engine. It all relates to the time needed for an event to occur. Assuming everything else remains the same, VE at idle is directly related to the density of the air charge in the cylinder/intake. The swept volume of a cylinder doesn't change between idle and WOT. Only the density if the air does. It is only after the throttle is opened that we run into how the other components affect the VE of an engine. ( I am trying to keep this related to the idle/WOT transition only). So ...... At idle we are metering the density of the air in order to control engine speed. As we go to WOT there is a transition period equal to the lenth of time it takes for the air, at atmosferic pressure, to move past the throttle and reach the cylinder. This is why IR intakes tend to have better throttle response than common plenum intakes. The throttle plates are closer to the cylinder therefor less time to affect a change in air density. If we confuse the issue at this point with upper engine speed VE and the like we will miss the point. The cam, compression, and exhaust system have the greatest affect at this point. Each affects the time needed for the air charge to reach the cylinder at full density. If we add too much or not enough fuel at the wrong moment the throttle response suffers do to the cylinder being either too lean or too rich. I have used up enough bandwdth for now. Obviously this is a very simplistic view of all the variables and how they interact. Hope it will help some. Back to lurk mode. Scott ------------------------------ End of DIY_EFI Digest V4 #671 ***************************** 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".