[Diy_efi] boosted compression ratio

[Bernd Felsche]

On Sun, Dec 22, 2002 at 10:26:03PM +0000, Mike wrote:

> At 09:52 PM 22/12/2002 +0800, you wrote:
> >On Sun, Dec 22, 2002 at 09:09:47PM +0000, Mike wrote:
> >> At 08:17 PM 22/12/2002 +0800, you wrote:
> >> >> Well why the heck dont you add a water injection setup and get the
> >> >> humidty artificially - and you could chill it as well :-)

> >> >Expense and water is scarce. :-)
> >> 
> >> Yeah methanol might soon be cheaper, the way the rains are going ;)

> >> >Still trying to get a cheap inlet fogger together; that should do
> >> >the trick. In winter, I'd have to heat the fog so that the air
> >> >temperature rises as well. At 8 degrees C, air is saturated with
> >> >only about 8 g of water per kg of air. Heating the air to about 25
> >> >degrees increases that to about 20 grams. That's worth 3 Octane
> >> >points; but the temperature rise reduces the effect by 1 to 2
> >> >points. <sigh>

> >> But hang on, you dont want water vapour and you dont want too
> >> small a droplet size otherwise it will become vapour by the time
> >> it gets to the cylinders. I dont recall what boost you were

> >Yes I DO want water vapour. Check the Gasoline FAQ. It deals with
> >humidity - absolute humidity is what appears to be significant in
> >inhibiting knock.

[snip]

> In all the practical situations I've encountered, water droplets
> are preferred because the latent heat of vapourisation is high
> in comparison with the effect of the droplets becoming vapour,
> this *and* the fact you can chill the water to a degree or so Celcius
> with a peltier device etc - Is going to make all the difference,
> on its way from the nozzle to the chamber those droplets at
> a degree or so will encounter turbulence and shed some heat from
> the air... I'll check out the gasoline faq shortly,

> >I want my engine to last another 250,000km and liquid water is
> >not conducive to long engine life!

> Also I've seen a couple of engines that ran WI and they were
> far far cleaner then those that didnt, of course you have the
> safety interlocks, no WI below 1500rpm and idle engine for
> 60 secs after last WI (minimum before shutoff) and flow
> sensor/shut off solenoid on feed to nozzle etc etc
> I'd expect a properly constructed WI system to enhance engine
> life, running higher boost without WI will shorten it, in 
> any case most turbo engines need a rebuild after 250,000K
> anyway - so 'go figure' as they say in USA ;)

Mine's not a turbo engine.

Besides; the base engine of a road car shouldn't need a rebuilt
nowadays until well over 300,000 km. Turbo and exhaust probably will
require replacement at that stage in any sort of performance
application.  Various bits of plastic in the engine compartment tend
to be come brittle after 5000 hours at high temperatures, so they're
more likely the cause of problems with electrical "gremlins" and
various air leaks being par for the course.

> Sure water is bad from lots of perspectives but so is
> too much fuel or not enough etc

> What boost did you say you are running ?

Zero.

-- 
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