DIY_EFI Digest Sunday, December 5 1999 Volume 04 : Number 676 In this issue: New list member with a project (very long) Re: DIY_EFI Digest V4 #675 Re: guessing re: Complaining Ref. Signal off of AMC I6 See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Sat, 04 Dec 1999 16:33:42 -0800 From: "Andrew Brownsword" Subject: New list member with a project (very long) Hello, I just joined the list a couple of days ago. I am in the middle of a project that I thought you folks might be able to offer advice on. I tried posting a description of this to the list already, but I think I got the email address wrong last time. If you get two copies, I apologize in advance. Before starting I'll just let you know that I'm a relative novice in all things automotive, but am a software engineer in the computer games industry so I know something about programming and microprocessors. Anyway, on with the adventure: My project car is a 1993 Ford Probe GT. It has a Mazda engine, the KL-03. This is a 2.5L DOHC V6, OBD-I, and of course EFI. The airflow sensor is a vane airflow meter (VAF), which is flapper door style. The ECU is a version of the MC68HC11, with an assortment of support chips. About 6 months ago I had a local shop install a turbocharger (Garrett T04E 52). The original plan for fuel delivery was to use a CarTech adjustable FMU. That is what the car has been running on since then, but the stock injectors turned out to be fairly anemic (220cc/min) and even doubling the fuel pressure doesn't allow me to run at my target boost level (6-7 psi) without going extremely lean. In addition it raises the fuel pressure at idle slightly, causing the car to idle more poorly than stock. I've been running at 2-3 psi while I work out a solution. Part 1 of the solution was to obtain higher flow injectors from the only source available -- VENOM. It took longer than necessary, but thats a different story. Suffice it to say that I now have 6 350cc/min injectors sitting on my shelf. The first attempt to install them ran into, predictably enough, problems. The stock ECU obviously doesn't understand high flow injectors and thus the car can't possibly run without some modification to the injector control logic. Part 2 of the solution, therefore, was to reprogram the ECU. The initial naive attempt was to modify the one table that the shop's ROM mapping software knows about in these cars -- it turns out to be a Load vs. RPM fuel enrichment table. Unfortunately this table can't be tuned "downward", and it certainly doesn't help with idle. Clearly a more extensive reprogramming was to be required, especially since completely replacing the ECU is not something that I really want to entertain. My next step (part 3, if you're keeping track) was to obtain a bunch of hardware and ROM information from a very helpful and knowledgeable fellow PGT owner (who happens to be on the same PGT mailing list that I am on). >From him I obtained a lot of hardware information, an initial ROM image, and a few starting points. I also got the ROM image from my own car and wrote a MC68HC11 disassembler (rather cool, if I do say so myself), and another program which makes scripted changes to a ROM image (it scales values according to the injector ratio, recalcs the checksum, etc). I've spent the last month working backward from the functions which actually control the injectors. At this point I have figured out the 7 places from which the injectors are fired, and located a ROM value or table which is used to scale the value before it is passed to the injector functions. Next week I'm going back to the shop and we're going to try installing the program to see if it actually leans out the mixture like I expect it to. If it does we'll drop in the high flow injectors and hopefully we'll be in business. The only (known) additional likely complication is that the stock airflow meter (the VAF) may not be able to read values > 1 atmosphere. If this is the case I'm going to need a supplement or replacement. I have several options at this point: piggyback computer, alternative VAF, lean the injectors out a bit more and keep the FMU. There are two piggyback computers that might do the trick. Neither of them support this engine directly, but there is another PGT owner out there that has tried them both. They are the SuperAFC and the Link AFM. The Link AFM includes a MAP sensor, the SuperAFC purportedly has inputs for a MAP sensor. Both of them modify the VAF's input voltage to the ECU, tricking it into a longer duty cycle. There is one possible replacement VAF: 2nd gen 87-88 RX-7. It looks like exactly the same design, but is used in a car which runs about 6 psi. This seems like a very appealing solution if the VAF on the PGT can't handle boost. Hopefully we could just recalibrate the VAF's interpolation table in the ECU and thing would work (yeah, it sounds optimistic to me too). Keeping the FMU is my least favourite solution, but it is the easiest one and will likely work in the short term. By telling the ECU to lean it out a bit more we can compensate for the slightly higher idle fuel pressure that the FMU causes. Basically its a hack until a better solution is available. Whew, this turned out WAY longer than I intended. Thanks for reading this far, and if you have any suggestions, tips, experience, advice, comments, insights or trivial... please let me know. Andrew Brownsword PS: The end result is definitely worth it. The KL-03s biggest problem is that it doesn't breathe well and delivers only about 135 hp to the wheels in stock form. We dyno'd mine @ 5psi up to 5500 RPM where it really leaned out and measured 210hp at the wheels. Even at only 2-3 psi it hauls. ------------------------------ Date: Sat, 4 Dec 1999 21:46:33 EST From: Fisystems@xxx.com Subject: Re: DIY_EFI Digest V4 #675 Looking for good Air/Fuel gauge! Can anyone suggest one? Needs to be some type of wide band o2 or Horiba sensor. Fast acting and very accurate. It would also be nice if it could log data, like AFR Vs RPM. ------------------------------ Date: Sat, 4 Dec 1999 21:52:02 -0500 From: "Clare Snyder" Subject: Re: guessing > ------------------------------ > > Date: Sat, 04 Dec 1999 02:23:36 +1100 > From: Phil Lamovie > Subject: Stop guessing at facts. > > Hi All, > > I really must protest ! > Absolutely no guessing on my part. The reference to "best guess" is to the method used to determine how much enrichment is required - carbed or injected. I KNOW it is not a hard and fast calculation, and many itterations are gone through before a "successful" calibration is arrived at. > There is a very large amount of misinformation being posted to the > list > of late. > > Stoich is the point where all of the fuel inhaled by the engine is > combined > > with all of the available oxygen in the cyl. And what is a better explanation? Mabee change it to "stoich is acheived at the point" Lets not fight over semantics. Any leaner means less > than > > optimum power. Any richer means less than optimum power per lb of > > fuel used, as some is not burned, as well as less power overall. And what is wrong with this? Too lean means reduced power. Too rich means less power from every pound of fuel than possible, and less power period, after a point. > This is but a mild example. > > 1.0 " Stoich is the point... Not True ! Stoich is only the ratio of > required air > to ingested air the quality of combustion is not in any way > relevant. Required air to injested air? I am not following you. We are talking mixture - stoichiometry is a branch of Chemistry relating to composition of compounds by weight. - > > 2.0 " Any leaner means.... Not True ! Optimum power is not an > engineering concept. It is neither peak power, peak torque or > peak > efficiency. Nothing of interest happens at stoich because it is > only > theoretical. 14:1, or whatever, is theoretical. Actual stoich is the ratio at which all hydrocarbons and all oxygen are combined to produce water and co2. Never fully acheived in ral world conditions, but a moving target to be aimed at. Most engines need 15 to 20 % more fuel than stoich to > > make peak power and 10% less to make peak efficiency. > > The problem I have with all of this is that our topic is 100% physics > yet > many of the posts seem to not be happy with this state of affairs. > Physics AND chemistry > > The problem remains that as long as the list is a home for risky > physics and those who have real working answers are less inclined to > contribute as they know that the readers/lurkers will have great > difficulty > sorting fact from fiction. > Sometimes things have to be simplified in order to be understood. Once the basic understanding is achieved, the details can be reintroduced. ------------------------------ Date: Sat, 4 Dec 1999 23:31:16 -0500 (EST) From: "Clive Apps Techno-Logicals 416 510 0020" Subject: re: Complaining > > From: A70Duster@xxx.com > Subject: Soap box > > Phil writes > > << Most engines need 15 to 20% more fuel than stoich to > make peak power and 10% less to make peak efficiency. >> > > and > > <> > > Three helpful tidbits and a bunch of complaining. If you need to unsubscribe > then BEFORE THIS TURNS INTO A FLAME WAR: If you consider advocating for accuracy as complaining maybe YOU should put on your cowboy hat and ride out of town we need facts not 1/2 fact half baked ideas, backed up by ego and attitude check your ego/attitude at the door this forum is for exchanging ideas and facts I see a lot of mis-info info here and it becomes a problem for people that do not know the theory and/or practice of engine design and mistakes in these calculations can expensive very fast If you don't know know, don't guess, and if you do guess, say so most engines do make max power at about 12:1 A:F ratios and max fuel efficiency at about 16:1 these are right at the +20/-10% stoich numbers and 7000 RPM on a 4 stoke is ~14ms ~80% PW 60x1000x.8/7000/2 Clive ------------------------------ Date: Sun, 5 Dec 1999 00:56:23 -0500 (EST) From: Mike Comai 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: 5K 10K Coil -----/\/\/\/---------/\/\/\/\------------ ECM | | ----- ----- ----- 15uf -----100pf | | gnd gnd When the filter is in place, the injector don't fire. When I remove the filter and connect the coil directly to the ecm it appears to flood out the engine :( If someone could explain what voltages levels and shapes are present on the neg. side of the coil and what it needs to get conditioned to for the ECM that would be great too. Appreciate any help yall could give. Mike Comai '79 CJ5 ------------------------------ End of DIY_EFI Digest V4 #676 ***************************** 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".