DIY_EFI Digest Monday, August 9 1999 Volume 04 : Number 459 In this issue: Why would Honda ? See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Tue, 10 Aug 1999 00:57:50 +1000 From: Phil Lamovie Subject: Why would Honda ? Hi All, > Why would Honda put the MAP sensor just behind the throttle plate? Good question. I guess from the tone of what you wrote that you suspected that this could be an issue. I agree with you it probably is. They could of course have a table of correction factors for air temp vs non linearity vs volume. Next issue is why are they using an ambient sensor ? Doesn't the engine know what air pressure it is subject to ? To help with the lack of load points you can interpolate with a calculator and save your precious clock ticks for real work. If zero vacuum at 5,800 or so needs 12.5 ms per intake have a look at the advertised torque curve and overlay it on your fuel map. Absolutely no desire to make fun Sorry. Only bad manners on my behalf. > For a race car calculating a new injector value PW every stroke may be a > requirement but is that really needed for marine or aircraft > applications? Yes. and on second thoughts Yes. If the calculations are done per cycle then the sudden throttle and/or load change will encounter maximum of 2 bad combustions. Now that probably sounds excessively picky but if your engine goes from 250 hp to 125 hp in 1 revolution and then back again the stress cycles on the crank are enormous. Even bailing wire has a cyclic strain limit. Question ? Who blows up all those F1 engines. 1. CNC machines that can't tell a thou from a foot 2. ECU (read software) that can't keep up with the engine ? 3. Other Try creating a 4 byte map. MAX. Vacuum 1000 rpm Max Load 1000 rpm Max vacuum 6000 rpm Max Load 6000 rpm if you interpolate b/w these 4 points and each on it's own is correct then you will be on average spot on. (This doesn't include camshaft timing alterations) this would require the 6 point map. By 65,000 points I didn't mean memory locations I meant possible calculated values from rpm 8 bit X vacuum load 8 bit. thus 255 x 255 = possible outcomes. You will at some stage have to get those 4 measurements as they are the basis for all further corrections. Full load 6000 rpm is easy just pull the stick all the way and the prop will do the rest. Full load 1000 rpm has more air per cycle than 6000 rpm so give it 10% more Light load 1000 needs the rubber band to be removed. Light load 6000 needs about 10% less. say 14.0 12.5 2.2 2.0 This of course brings us to the point of when or if your system is crossing over from injecting once per revolution at light load to once every second at full load into focus. The differential b/w light and full load is on average 350% i.e. 2.0 - 6.5 ms. You need to investigate this further. There ! that's 4 bytes of eeprom all used up. You have only to get rpm from the timer ticks vs a single A/D Vacuum Load and you are ready to go. Your last air, water and accel corrections are waiting from the last stored calc. apply these and squirt. Given a 1 mHz internal clock and 6000 rpm you have 10 ms or 10,000 clock cycles to get this done. say 2000 instructions executed at worst. P.S. if this to and fro is boring the pants of others please chime in and tell me firmly. TTFN Regards Phil Lamovie injec@xxx.au cogito ergo zoom ------------------------------ End of DIY_EFI Digest V4 #459 ***************************** 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".