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Date: 23 Mar 2004 01:10:35 GMT
From: Dave Hinz <davehinznospamcop.net>
Subject: Re: Aquamist/water injection systems


On Mon, 22 Mar 2004 14:15:30 -0000, SAABurger <furnyburgernospamorld.com> wrote: > "9-3*Turbo" <NOSPAMnospampam> wrote in message > > A professional engineer friend recently did a lot of research on this > subject. OK, what's he a professional engineer _of_, please? > His conclusions were : > i) There is a lot of utter drivel spoken and written on this subject. True. > ii) The belief that water will increase power is unjustified under most > conditions. Not applicable. The "under most conditions" doesn't take into account Saab's system of boosting just up to the point of pre-detonation. WI raises the pressure at which this happens, so even late 1980's Saabs take advantage of WI for this reason. > iii) Benefit might occur in regions where only low octane fuel is available, > in exceptionally high ambient temperatures, or if maximum boost pressure has > been raised from the manufacturer's original setting. Nope, again, I can't help but think your engineer friend doesn't know Saab's engine management systems, or the basics of how they work. > iv) Improved intercooling offers similar benefits under the same > circumstances. Similar, yes. In conjunction with an effective intercooler, WI will work more effectively than if either of the two wasn't there. > v) If the engine does not suffer from pre-ignition (pinking / knock) then > you do not need to bother with water injection. Ah, yes. Like I said - the Saab engine management, again, going back almost two decades now, will increase the base boost (and later, the spark timing on a per-cylinder, per-power stroke basis) to juuuuuust short of the pre-ignition point. By adding water, you allow that to happen at a higher boost and/or an earlier spark, getting more power. > On the subject corrosion, it seems most unlikely that water injection will > have a deleterious effect on the turbo or anything else. Yeah, being downstream from the turbo and all... > Reason - the main > products of fuel combustion are carbon dioxide and ........... wait for it > .............. H2O. Lots and lots of water vapour passes through your turbo > every time you use the car whether or not you have water injection or not! This much is correct, yes, water vapor in the exhaust is a non-issue. Adrian, while your engineer friend's opinions on the matter might apply to a car with a fixed boost point and "set by timing light" ignition timing, they don't apply to a car which was designed to, by nature, maximize the power of each power stroke by sensing what the engine is doing. If they didn't have the sensors and computers to monitor and adjust, I could see this being applicable, but it's not the case. You might want to mention World War 2 and Rolls Royce aircraft engines to him, by the way. Dave Hinz

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