Water injectin: How much? Or maybe propane?

[Daniel Houlton]

Regarding my new ERL water pump in my previous message, I have some 
questions on how much water to inject.

First, I'm running an Isuzu 2.6l 4 cylinder that I turbocharged using
junkyard parts (rebuilt the turbo though).  Max boost is 9 psi.  
Compression is 8.6:1.  On regular gas, I get detonation at about 5 - 6 
psi.  On 92 octane, it holds off to 8 - 9 psi and even then not all the
time.  It depends on how hot out it is and how long I've been driving 
(open K&N in the engine bay.  Not good I know.  I'm working on it).  I 
am not yet running an intercooler either.

Max HP according to HomeDyno is 140 at the wheels, up from 94 before the
turbo.  The before turbo run was calibrated against a chassis dyno run so
I know the HomeDyno results are accurate.  This is a bit below the 150 
or so mathematical HP I should get with 9 psi, but I assume this is because
of the large heat buildup.

Any idea how much water I should be injecting?  I was hoping to modulate
the pump by using a MAP sensor and sending increasing voltage to the signal
wire as boost goes up.  I'm now thinking that I can use a tee to two 
nozzles.  Plumb one side of the tee through a solenoid.  Have the pump come
on at say 4 psi, injecting through one nozzle.  At say 6 or 7 psi, open 
the solenoid so it's injecting through 2 nozzles.

This is just an idea to conserve water and still get injection in the lower
boost areas.  I'd like to be able to run regular 87 or 88 octane gas again.
I'll need to start injecting by at least 4 psi I think.

I typically only hit about 5 or 6 psi unless I'm really on it so if I can
hold off injecting the full amount of water until then it means I won't 
have to refill nearly as often (in theory anyways).  Any flaws in this or
should I just dump all I can as soon as I can.  It's only water after all.
I'm planning a second tank underneath some where anyways so I should be
able to get 2 or 3 gallons total storage.

The idea is the upper (winshield washer) tank will feed the pump.  When
it's low water level switch closes it'll power the pump in the lower tank
to re-plentish the upper.  The low level sensor in the lower tank I'll 
wire to a light in the cab somewhere.


The other question is about injecing liquid propane through the nozzles
instead of water.  The pump is sealed so the liquid is seperated from
the pump mechanism.  I haven't asked ERL yet about propane, but they 
do say it's safe for ethenol, methenol, etc.

The propane would increase octane and decrease temps as well.  Also,
if I'm injecting only under boost (this is theory now) the temps should
be high enough and the duration low enough that I don't have to worry
about nozzles freezing up.

The final thing is that I have a shortage of fuel at high boost.  I 
haven't yet switched to larger injectors, run an additional injector or
anything else to increase fuel.  I'm wondering if I could tweak it 
enough that the propane in addition to doing what the water would do
would work as the extra fuel I'd need.   I know there are more issues
with makeing it play nicely with the ECM and getting the A/F ratio 
correct, but I'm just wondering if it's technically possible or is it
hair-brained?  

I'd probably at least figure out how to control the pump (or break down
and get the MF2 controller ERL sells) so that I could have a nearly 
infinite injection range rather than a 1 or 2 step on/off kind of switch.


thanks
--Dan
houlster at inficad.com
http://www.inficad.com/~houlster/amigo.htm