Suzuki RG500 GAMMA

Date: Tue, 11 Aug 1998 03:03:31 EDT
From: ScanRan@aol.com
Subject: water injection

Hello 2smokers-

Numbers first, theory later. But there is a caveat, so you have to read the
notes afterward.  And these are not my usual cylinders, so don't compare this
to any prior stuff I've posted.  advantage w/ water was from 6.25K to 8.75 or
so Krpm.

run #1,  for a baseline. powervalve on auto.

run #3, water injection active.  consists of a generic 12V windshield washer
pump, connected to #67 main jets tapped into the headpipe 6.5" downstream
from the exh flange on each pipe.  hp readings  Pvalve fixed CLOSED (hi rpm
position) see notes.

RPM     run1   H20 run
6K         31.1      26
6.25       32.4      39.5
6.5        35.4       47.4
6.75      40.8       54.7
7           46.4      62.0
7.25      52.7       68.6
7.5       57.8       75.9
7.75      64.3       81.0
8          71.1       84.7
8.25     79.7       87.6
8.5       85.2        88.7
8.75     86.2        86.7
9          88.1       80.3
9.25      92.1       75.1
etc etc after this water inj dies quickly. H20 reduced the peaking rpm of the
motor from 10500 to 8500 rpm. 

as you can see, there is a massive increase in torque, approx 30% boost in
places.  So the question is not whether it works, it works VERY WELL!   the Q
is , is it worth the hassles?  for an extra 18 hp? try that vs any other bolt
on  :)

today's hassles: nozzles siphoning into the pipes all the time, lotsa extra
water collecting and  then blowing out all over the 1st time we tried it,
 how to switch RPM vs throttle vs???  there would be a major kick in torque
if this comes on when you don''t expect it,  purging air from the lines so no
time is lost filling the lines w/ water, how to get a good spray pattern from
a 5 psi pump, or switch to a higher output pump, pipes blowing bubbles into
the lines under normal operation,  good source for nozzles providing approx
.05-.07 GPM flow rate?

here's the bad news for RG owners. I mentioned this before but now it's
relevant again.  The Suzuki does not alter the exhaust port height like a
YPVS. The RGs exhaust valve functions by killing the exhaust pulse before it
gets to the chamber. That way it prevents the pipe from adversely affecting
scavenging when the pipe is off-tune from the motor.

well, it really works. when the valve is open (low rpm pos) it basically
makes the exhaust pipe go away. this prevents negative effects of an off-tune
pipe. It also defeats the helpful effect of water injection.  we got little
benefit from the H20 w/ the p valve on auto.  locking the valve in the hi-rpm
position (closed) allowed the pipe to function below 8000 rpm and the h20
then had a big effect.

so to get the H20 to work, you need to have the Pvalve closed. in fact, it
completely negated the flat spot normally present when the P valve is fixed
closed. Valve  would basically not be needed in a racing situation, I
suppose.

there was no noticable water in the exhaust on the 'good' run. on the 1st
water run, it just spewed water out the back. the pipes had water sitting in
them I suppose and it was quite a mess.  really disgusting!  so there are the
crap-ejectors, true to prediction.

I imagine this will work nicely on a 125 with a little sorting. The net
result on my bike was the powerband effectively started 1000 rpm sooner.
  Going to install it on the RD350 next.  the entire setup weighs very little
when empty. Just add water when you want to go faster!

Randy N.
scanran@aol.com
>>>


Run 1 is with the motor functioning normally, with powervalve on auto. run 2
is with the water injection. 

the h20 has me above 40
ft-lbs 1000 rpm sooner than without. (40 ft lbs by 6600 RPM) and it will be
better with my usual cylinders.

 I'm not an expert but I've spent a fair amount of
effort researching this subject in past months-- I can refer you to three SAE
papers on the subject; SAE 942515,
SAE 911228, and SAE 911226. 

to quote:  " Some two stroke manufactuers have used exhaust resonators to
improve low speed torque.  By dissipating the exhaust blowdown pressure pulse
into a separate chamber at low speeds, the returning pressure pulse has a
very low amplitude, and thus does not have such a drastic effect on engine
performance."

this attenuation of the exhaust pulse is what prevents the newly in-tune
water fed pipe from *helping* at lower rpms.  we did a run with the valve on
auto, and got mediocre results, then thought about it for awhile and repeated
the run with the valve shut (hi rpm position), at which point there was a
very large torque increase. so that seemed to bear out what I read in the SAE
paper about our powervalve's operation. This understanding did not just occur
to me in a flash of genius;  without my outside research I would also be
under the volume/ resonance misconception.

SAE 931506 covers water injection, and oddly enough, I followed their setup
by and large, and achieved very similar relative gains (their test motor was
a 125)

The current setup is this:

NOS rpm switch, 'arms' the system between 6000 and 8400 rpm.  in order to
inject water, the motor must be between those rpms and also there are 2
switches that control the system, one senses when the powervalve is in the
high rpm position, and the other is a throttle position switch.  so, half+
throttle,  revs btwn 6k and 8400 rpm, and valves "shut" will inject water.

the entire setup is turned on or off by a master switch on the dash.

I use a variable exhaust valve controller made by BDK, and the dial for this
is also on the dash. so, wherever I set the exhaust valve, the water will come
on in synch with the valve.

a 3 qt tank is mounted under the tail. this feeds a generic windshield washer
pump (thru a filter). the pump puts out 5 psi.  this injects into the
headpipes thru #70 round head Mikuni main jets.  bungs welded onto the pipes
accept brass fittings, which have jets tapped into them where they go into the
pipe, and have 6" of 1/8 steel brake line 'leaders' coming out to keep from
melting the plastic water lines.  I have 3 psi check valves installed just
upstream of the jets to prevent water from siphoning into the pipes.

the 3 qt tank has a low level indicator , which lights up the sidestand
indicator when the water is low.

this setup will provide about 180 seconds of injection to 4 pipes.  that
doesn't sound like a lot, but it lasted hours in frequent use in mountain
riding.  on the track, 1 qt lasted me thru a 20 minute practice session.

The only real problem I have anymore is the switch on the powervalve, which
is a cheap piece of crap and keeps crapping out on me.  I guess I need to
drive PAST radio shack, and get a real switch.

Randy N.

PS there is a water injection setup for sale on the factory pipe website, for
use in watercraft.  it is an old outboard racing trick, nothing really new.

Rob Koopman ( Rob.Koopman@inter.NL.net ) ^{RG500 Index}