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Date: 13 May 2002 13:04:46 GMT
From: davehinznopsamcop.net
Subject: Water injection with T7 ecu? (Was: Clueless dealer)


Someone who looks an awful lot like Andrew Hookins <andrew.hookinsnopsamamnopsamodata.co.uk> wrote: > Dave, > I think the short answer is that water injection is more fuel > effecient using this scheme, but that conventional ignition > mapping methods actually reduce fuel efficiency when water > injection is used. I think it's certainly saying that it's taking it into account, if nothing else. The fact that the system can detect and adjust for humidity is intriguing. > I don't know how far SAAB have taken this scheme in T5 > or new T7 ECUs. My interpretation of this paper is that > water injection increases inlet manifold pressure Yes, I saw that too. > and that a > conventional MAP sensor based ignition advance/retard > scheme would retard slightly to compensate for a perceived > increase in engine load. This action actually reduces engine > torque further because the humid air burns/ignites later than > a dry air/fuel mixture. Yes, that would be the traditional way of doing it. > However, using this scheme to sense > when peak cylinder pressure is achieved and using this to > advance the ignition timing to compensate for the slower > ignition/burn characteristic of the humidified air/fuel mixture > actually increased engine torque by a couple of percent. Hrrm, so this sounds like water injection *would* work. Do you recall what the effect on combustion chamber temps is? Intuition would say that it lowers temps, but ??? > Perhaps re-posting this under a different heading would give > rise to an interesting thread (snip) Done. OK, so back in the CIS and Jetronic days, Saab sold a water injection system as a performance accessory, which would, when the WOT switch was closed (Wide Open Throttle), would spray a water mist into the intake manifold, just in from the throttle plate. Anyone recall what effect that had on performance, and maybe emissions? Do they have a duty-cycle limitation, or does the WOT switch take care of that (what percent of time does someone *really* drive around at wide-open-throttle?) Dave Hinz > AndyH > <davehinznopsamcop.net> wrote in message > news:abdshj$hg4gs$3nopsam34476.news.dfncis.de... >> Someone who looks an awful lot like Andrew Hookins > <andrew.hookinsnopsamamnopsamodata.co.uk> wrote: >> > Lee Marshalls, >> >> > My finger in the air guess is a pressure leak causing the ECU >> > to either get an incorrect manifold pressure indication, or >> > something preventing the wastegate working properly. >> >> One would hope they've checked for leaks in the components and ducts, but >> yes, false air would cause all sorts of odd problems. Given all >> they've changed, though, well I'd hope that's unlikely this far >> in to the exercise. >> >> > Dave Hinz, >> >> > Have a look here to see how the DI cartridge / spark plugs are >> > used sense what is going on in the combustion chamber: >> >> > http://www.vehicular.isy.liu.se/~larer/Projects/main.html >> >> Cool, thanks. It's even in English, which makes it a bit easier >> to read. >> >> > Interestingly this control scheme can actually actually adapt to >> > changes in air humidity because it can 'measure' when peak >> > pressure occurs. >> >> I've just done a very cursory read, but am printing it out for >> study. A question - is this how it's done in, say, the T7 ECU? >> My initial thought is that I wonder if this means water injection >> would be more, or less, effective using this sort of an engine >> management system. >> >> Thanks for the link, Andy. >> >> Dave Hinz >> --

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