DIY_EFI Digest Wednesday, December 1 1999 Volume 04 : Number 668 In this issue: Re: DIY_EFI Digest V4 #667 Transient enrichment Re: Transient enrichment QNX Floppy Tools? (Was DIACOM) Sunbird wiring See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Tue, 30 Nov 1999 17:19:35 -0500 From: Todd Israels Subject: Re: DIY_EFI Digest V4 #667 > >Date: Mon, 29 Nov 1999 23:13:32 EST >From: PHXSYS@xxx.com >Subject: HC11 starter system > >Hi > >I am used to programming PIC microcontrollers. I know that the HC11 is more >suited for automotive applications. I was wondering if someone could >recommend some good resources for getting started with the HC11? > >What compilers are available? >Good books to start with? >Hardware packages to make it easy to start testing code? > >Thanks > >Jon > >------------------------------ > There are many resources available with a simple web search. You may want to look for Technological Arts they have an inexpensive board for using a HC11 with a breadboard. Check out programing 101 and the GMecm list. A 7730 has all the code on the eprom so it can be hacked, replaced or modified, I picked up one at a bone yard for $40 . ------------------------------ Date: Wed, 1 Dec 1999 11:18:34 +1300 From: Tony Bryant Subject: Transient enrichment This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. - ------_=_NextPart_000_01BF3B80.DAB95076 Content-Type: text/plain; charset="iso-8859-1" I've spend a while now trying to get to the bottom of the need for transient enrichment on MAP systems, especially that involved with transitioning out of a low rpm idle. For those not in the know, snapping the throttle open at a low rpm idle causes a 1/2 second lean-out stumble. This is worse the lower rpm you go, and worse the more cam overlap you run. I run across bazillions of different theories, all of which I've decided are crap (feel free to correct me though). e.g. 1) The flow change lags behind the pressure change. Bollocks. That would make it run rich, and besides the pressure change is CAUSED by the flow. 2) The intake runners have columns of air that need to be accelerated to the new conditions. Bollocks. That would also make it run rich, and besides the flow always tops between intake cycles anyway. 3) There is a delay getting the fuel in the port to the cylinder. Bollocks. Its squirted directly on the back of the valve, at low rpm it'll just run in under the influence of gravity, when the valve is opened. 4) Manifold wall wetting effects Bollocks. This is port injection, the walls don't ever see fuel. 5) The vapourised fuel in the port condenses because of the pressure increase. Maybe, but it seems that this would not cause a major change in fuelling, as its hard to see how the fuel in the cylinder will not be burnt. 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. 7) Ram Air effect of the flow coming into the manfold. Perhaps, but hard to see how this will have more than about 10% percent, running that much richer steady state doesn't seem to help. - ---------------------- 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. 2) The fact that the fuel is injected before the IVO (intake valve open) event, but the engine "samples" MAP at IVO. Therefore it may not be predictable what the fuel will need to be, when the fuel is squirted in, because the MAP can change significantly then and IVO. A carb will also experience delays in fueling, mainly due to distance from the port, so hence the need for the throttle pump. Q. How do TBI system deal with this? Weber DCOEs throttle pumps will squirt seriously far and fast, and these carbs are known for being able to acheive exceptionally good throttle response. SU carbs combat this by momentarily restricting the airflow, thereby bypassing the problem. Plus the excellent vapourisation at low flows, will make the engine more resistant to lean misfire. I've heard rumours of some OEM ECUs, doing multiple injections per revolution to effect their enrichment, based upon dTPS/dt, this would certainly help. Obviously the other idea that may help, it calculating the fuelling and injecting at late as possible in the cycle, i.e. to coincide with the closing of the valve. 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Lots of things come into play. I'm addressing a street engine, as opposed to streetable or racing. Snip | I run across bazillions of different theories, all of which I've | decided are crap (feel free to correct me though). Everyone is entitled to their opinion, weither you call it crap or not is immaterial. | e.g. | 1) The flow change lags behind the pressure change. | Bollocks. That would make it run rich, and besides the | pressure change is CAUSED by the flow. The further from street toward race this does matter, more and more. | 2) The intake runners have columns of air that need to be | accelerated to the new conditions. | Bollocks. That would also make it run rich, and besides the | flow always tops between intake cycles anyway. Why then is cross sectional area so important to throttle response?. | 3) There is a delay getting the fuel in the port to the cylinder. | Bollocks. Its squirted directly on the back of the valve, at low rpm | it'll just run in under the influence of gravity, when the valve is | opened. Gravity ain't fast enough for cylinder filling of puddled fuel. | 4) Manifold wall wetting effects | Bollocks. This is port injection, the walls don't ever see fuel. Look again, where does the fuel go when sprayed against a closed valve?. The back of the valve, and splashs the walls, not the entire lenght like a carb set up, but still some. | 5) The vapourised fuel in the port condenses because of the pressure | increase. | Maybe, but it seems that this would not cause a major change in fuelling, | as its hard to see how the fuel in the cylinder will not be burnt. If the droplets are large enough it won't.. | 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 | 7) Ram Air effect of the flow coming into the manfold. | Perhaps, but hard to see how this will have more than about 10% percent, | running | that much richer steady state doesn't seem to help. | ---------------------- | 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. If you've changed cams, or got too much volume in the MAP sensor line, then the filtering rate may be off. The ecm can play a chess game between ignition cycles. Time/response not an issue or no high performance engine could run one. | 2) The fact that the fuel is injected before the IVO (intake valve open) | event, but the engine "samples" MAP at IVO. Therefore it may not be | predictable what the fuel will need to be, when the fuel is squirted in, | because the MAP can change significantly then and IVO. For vaporization, (ie street) you want the fuel to hit the back of a closed valve, also, the shearing action against the fuel as the valve opens. | A carb will also experience delays in fueling, mainly due to distance | from the port, so hence the need for the throttle pump. Q. How do TBI system | deal with this? About the same as TPI... | Weber DCOEs throttle pumps will squirt seriously far and fast, and these | carbs are known for | being able to acheive exceptionally good throttle response. Only when calibrated correctly, and the same for EFI... | SU carbs combat this by momentarily restricting the airflow, thereby | bypassing | the problem. Plus the excellent vapourisation at low flows, will make the | engine more resistant to lean misfire. At the expense of poor throttle response (compared to weber whenboth are right). | I've heard rumours of some OEM ECUs, doing multiple injections per | revolution | to effect their enrichment, based upon dTPS/dt, this would certainly help. Yes. Grumpy | Obviously the other idea that may help, it calculating the fuelling and | injecting at | late as possible in the cycle, i.e. to coincide with the closing of the | valve. | | Open to the floor for comments/flames..... ------------------------------ Date: Tue, 30 Nov 1999 20:16:35 -0700 From: "Jim Velasquez" Subject: QNX Floppy Tools? (Was DIACOM) /de-lurk/ [snippage] > and your point is? I preffer shareware w/ source then > I can be my techsupport line. Have you seen the QNX demo disk? > I have an aldl interface, and a bunch of other stuff (including > a posix os, and gui) all on one disk! OK this begs the question: Any plans to share this little gem? 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). /re-lurk/ - -Jim Velasquez ------------------------------ Date: Tue, 30 Nov 1999 22:19:58 -0700 From: cwagner@xxx.net Subject: Sunbird wiring Does anyone have a wiring diagram for a 2.0 Sunbird using the 7749? Need it for a conversion. Also, does anyone have a list of where the data tables are located on the chip? ------------------------------ End of DIY_EFI Digest V4 #668 ***************************** 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".