Toymods Car Club Inc: Tech & Conversions => Aftermarket ECU's vs Drivability

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oldcorollas
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Kita-Ku, Sapporo, Japan
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January 2003

Re: Aftermarket ECU's vs Drivability	Mon, 06 October 2003 01:55

well, no war to be started but it comes down to a few things. what inputs the ECU has, what algorithms it uses, what enrichments ae available, what it's accuracy is (in terms of injector pulsewidth, not rpm resolution) when you think of the early toyota injection, it was analog, using AFM rpm and temp for inputs. no closed loop etc... the DELCO is actually a pretty advanced unit, even tho it was made years ago. get in contact with Richard Wakeling for info, he is by all reports excellent with that ECU. driveability is the ECU's ability to respond to transient events. economy is based on the tuning, and the ability to run closed loop at cruise, but mostly good tuning in the acceleration part of the map. for drivability and ease of use, i think you need. a)priming pulse and afterstart enrichment (so it doesn't keep stalling when you turn the key) b) warmup enrichment, so you don't have to wait 5 mins for it to warm up. c) acceleration enrichment and deceleration cut, so you don't have hesitation, and you don't have backfires (or blow mufflers) d)you want correction for intake air temp, since we have vastly different temps here, but air pressure correction is not as much of an issue (but a correction on startup would be nice. that way if you say.. drive to the snow, you can stop when you start getting to higher alt, and it readjusts the mapping) for economy (in both cruise and accelerating) i think you need, a) an 'intelligent table' where the injector pulsewidth is interpolated for all rpm vs MAP or AFM, rather than a step function. b) good pulsewidth resolution for accurate fuelling (maybe 0.1ms is good, since minimum opening time is in the order of 1-2ms, and max opening at 80% duty cycle @8000rpm is 12ms) c) closed loop feedback for stoich mixture at cruising (and be able to adjust how much and under what conditions closed loop occurs) d) good tuning. e) really good tuning stock systems work for stock motors, but i think a lot of the issues such as poor driveability and poor economy come from either too radical, or improper engine design. for example 300+ deg cams don't work so well at 'around town revs'.... another thing is ECU processor and bus speed. the Motecs run at around 32MHZ processor (not sure on bus), but the Megasquirt is only 8MHZ processor and bus, but has only 15-20% CPU loading. older ECU's run at even lower speeds, and iirc older stock putas run at 1MHZ or less... in closing (sorry for such a long post) you want a seamless table of fuel mapping (not 'cruise' and 'power' maps), you want various enrichments to counter adverse temps (both coolant and air), you want accel and decel features, you want closed loop (but even that is not necessary with good tuning), and also datalogging is great... all of this is available with the Megasquirt (since it was designed to take advantage and build upon current systems) oh, and MOST of all, you want good tuning software. nothing so frustrating as crappy software. check out Megatune 2.15 on the Megasquirt yahoo site, for a good example of easy to use software Cya, Stewart [Updated on: Mon, 06 October 2003 01:58] [Report message to a moderator]

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