Toyota Supra twin turbo and water injection.

Greg Hermann bearbvd at sni.net
Sat Apr 3 19:00:02 GMT 1999


>  Having studied the water injection techniques used by others, and
>getting ready to install my own system:  injecting water pre-intercooler
>is counter productive as the inter-cooler *cools* and this is not what you
>want to do to the water being injected.  You also do not, I am sure
>everyone knows this but just in case there is someone who does not, want
>to inject water pre turbo! The water will destroy the turbo blades.
>  I am injecting the water *after* the throttle body.  Any obstruction
>will, or could, collect droplets, so the throttle plate could distract
>from business.  I would think that the best place to inject water would be
>immediately after the throttle plate; anyway, that is where I plan to
>install my nozzle.

Other possibilities, once the water is on board include:

1. Have the cooling air side of an air to air intercooler coated with stuff
called "heresite" (stops corrosion), and spray water on the upstream face
of the cooling air side of the IC--This will depress the temp of the
cooling air to somewhere near the ambient wet bulb temp, and give you
cooler charge air WITHOUT adding any moisture to the combustion air.
Significant gains to be had here--maybe 3 or 4%.

2. A small amount of water (maybe 10% of fuel mass flow rate) after the
intercooler will yield some evaporative cooling of the charge air, and give
you a net gain of maybe 1% after correcting for the amount of oxygen which
is displaced by the resulting water vapor.

3. Beyond these amounts, applied in the places described, any injected
water is only desireable as finely atomized droplets which do not evaporate
until they are inside the cylinder, and not until after the intake valve
has closed. If you can achieve this situation, a water injection rate of
about 80% of the fuel mass flow rate can be extremely beneficial to power
output--like maybe an 8 or 10% increase--but it is not exactly easy to
accomplish this sort of water injection. Something along the lines of
compressed air atomization of port injected water, with the injection timed
to coincide with high intake port air velocity would be necessary to get it
done. The actual optimum water mass flow rate will vary with an engine's
effective compression ratio. Any amount of water above and beyond that
which will saturate the combustion chamber volume at TDC (at the (much
lower because of the injected water) TDC temperature) will reduce power
output.

The gain in power output from this (3.) approach is the net effect of a
vast reduction in the work which the engine must do on its compression
stroke balanced against a loss in Carnot efficiency due to lower peak cycle
temperatures. There is still more power to be had from this approach,
though, because the lower temps AND the anti -detonation qualities of the
water will allow you to go to quite a bit higher compression ratio on a
practical basis.

Regards, Greg
>
>At 10:59 PM 4/2/99 -0500, you wrote:
>>
>>-----Original Message-----
>>From: ECMnut at aol.com <ECMnut at aol.com>
>>To: diy_efi at esl.eng.ohio-state.edu <diy_efi at esl.eng.ohio-state.edu>
>>Date: Friday, April 02, 1999 10:37 PM
>>Subject: Re: Toyota Supra twin turbo and water injection.
>>
>>Yikes, now ya got me thinking.  I've done it pre cooler, but none of the
>>stuff has had a clear enough shot to see into the cooler's core.  Have you
>>seen this happen?.
>>Being steam can one of the chemical types say what we might expect?.
>>Simple answer would be distilled water, I quess.
>>Bruce
>>
>>
>>>> Having twin,sequential turbos suggests I inject water *after*
>>>>  the intercooler,maybe just in front of the throttle body? Or should I
>>>>  be injecting elsewhere?
>>>Hi Chris,
>>>Sounds like the right place.  You don't want to crud-up the
>>>inside of the IC core.  They are not intended to be hosed
>>>with water.   The crud that tap water causes to form on
>>>aluminum will reduce the thermal efficiency of the IC also.
>>>After the IC, but before the TB is a good location.
>>>GL
>>>Mike V
>>
>>
>>
>IZCC #3426
> 1982 280ZX Turbo GL
> 1966 El Camino
> 1982 Yamaha Maxim XJ-1101J Motorcycle
> 1975 Honda CB750 SS (black engine)
> 1986 Snapper Comet lawn mower
>Clarence Wood
>Software&Such...
>clarencewood at centuryinter.net
>Savannah, TN.





More information about the Diy_efi mailing list