Water Injection vs. Larger Intercooler??
01-02-2002, 12:39 PM
#1
Cruisin'
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Water Injection vs. Larger Intercooler??
I have a friend that runs (auto cross & rally) a HIGHLY modified, AWD turbo Eclipse. He has just installed a water injection system to supplement his upgraded intercooler. With the addition of the modestly priced $250 water injection system, he is running 4 more pounds of boost – 20 pounds! – with no detonation.
Briefly, I have a 1978 California 930 running B & B header/exhaust and large turbo. When I purchased the new turbo, I was told that it was a K27-7006. My new mechanic later told me that the unit appeared to a K29. Be that as it may, the compressor side is significantly larger than the K27-11 another friend installed in his ’79 930. After a brief experiment with adjustable boost, I have installed a 1.0 bar spring that, according to my Ruf boost gauge, is actually providing a modest 0.9 bar of boost. I had to replace the stock CD unit—opting for an integrated coil unit from Perma-Tune. The spark must be stronger than the stock unit as I had to retard about 2-3 degrees from stock timing when the Perma-Tune was installed. My intercooler is stock.
I have never heard of anyone installing a water injection system in a Porsche turbo but, given that we all operate under the same laws of physics and the apparent significant price/performance benefit water injection, thought I would put it out there. Per my brief Internet research, water injection has been successfully used in a number turbo applications such as: F1 in the ‘80s; rally cars since ’95; and, OE in Saab 9-5s.
My questions:
1) Has anyone installed a water injection system in a 930? What brand? Aquamist out of the UK was particularly informative and appears to offer a quality system. Aquamist also convincingly argues that, despite some public bias against, water injection is a very effective cooling medium to supplement a stock intercooler. Water detonation suppression allows you to safely run higher boost and, at the same time, will clean any carbon buildup in the motor.
2) Apparently, people commonly use the windshield water bottle as the source for the injection system. Though convenient, do I need to be concerned with lateral g forces? I would hate to have the water pump sucking air while driving through turns. What other tanks are out there?
3) As high-energy ignition systems are recommended with water injection, am I covered on this front with the Perma-Tune?
4) What boost should I be able to SAFELY run with a properly installed water injection system given the configuration of my 930? As high as 1.1 or 1.2 bar? My friend with the Eclipse increased his boost from 16 to 20 pounds of boost. Incidentally, his water injection is set to kick-in whenever his turbo spools above 10 psi.
5) Whatever the max SAFE boost may be, I assume my stock “european” fuel system will be sufficient given my motor config. I have read the stock fuel system will handle up to 450 hp.
6) What about timing? I believe my California car comes stock with additional timing retardation that was not installed on the other US cars.
7) Where is the best place to locate the water injector? My guess would be right above the throttle body at a 90-degree angle with the airflow. Per the Aquamist folks, they maximize the mist effect by injecting water with a 7 bar water pump.
8) What size injector should I use?
9) Any other thoughts/suggestions/warnings?
Any input will be greatly appreciated.
Briefly, I have a 1978 California 930 running B & B header/exhaust and large turbo. When I purchased the new turbo, I was told that it was a K27-7006. My new mechanic later told me that the unit appeared to a K29. Be that as it may, the compressor side is significantly larger than the K27-11 another friend installed in his ’79 930. After a brief experiment with adjustable boost, I have installed a 1.0 bar spring that, according to my Ruf boost gauge, is actually providing a modest 0.9 bar of boost. I had to replace the stock CD unit—opting for an integrated coil unit from Perma-Tune. The spark must be stronger than the stock unit as I had to retard about 2-3 degrees from stock timing when the Perma-Tune was installed. My intercooler is stock.
I have never heard of anyone installing a water injection system in a Porsche turbo but, given that we all operate under the same laws of physics and the apparent significant price/performance benefit water injection, thought I would put it out there. Per my brief Internet research, water injection has been successfully used in a number turbo applications such as: F1 in the ‘80s; rally cars since ’95; and, OE in Saab 9-5s.
My questions:
1) Has anyone installed a water injection system in a 930? What brand? Aquamist out of the UK was particularly informative and appears to offer a quality system. Aquamist also convincingly argues that, despite some public bias against, water injection is a very effective cooling medium to supplement a stock intercooler. Water detonation suppression allows you to safely run higher boost and, at the same time, will clean any carbon buildup in the motor.
2) Apparently, people commonly use the windshield water bottle as the source for the injection system. Though convenient, do I need to be concerned with lateral g forces? I would hate to have the water pump sucking air while driving through turns. What other tanks are out there?
3) As high-energy ignition systems are recommended with water injection, am I covered on this front with the Perma-Tune?
4) What boost should I be able to SAFELY run with a properly installed water injection system given the configuration of my 930? As high as 1.1 or 1.2 bar? My friend with the Eclipse increased his boost from 16 to 20 pounds of boost. Incidentally, his water injection is set to kick-in whenever his turbo spools above 10 psi.
5) Whatever the max SAFE boost may be, I assume my stock “european” fuel system will be sufficient given my motor config. I have read the stock fuel system will handle up to 450 hp.
6) What about timing? I believe my California car comes stock with additional timing retardation that was not installed on the other US cars.
7) Where is the best place to locate the water injector? My guess would be right above the throttle body at a 90-degree angle with the airflow. Per the Aquamist folks, they maximize the mist effect by injecting water with a 7 bar water pump.
8) What size injector should I use?
9) Any other thoughts/suggestions/warnings?
Any input will be greatly appreciated.
01-03-2002, 10:22 AM
#2
Cruisin'
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FYI - I e-mailed a copy of my inquiry to Aquamist:
Hello Brian,
Thank you for contacting me.
I will go straight to your questions:
1) I don't know for sure that a 930 has used our water injection as we
very
rarely sell direct to customers and so far we have not heard anyone
contact
us - people tend to call us if there is a problem otherwise we don't
hear
from them. We have however supplied to a few Porsches as well as a few
GT
racers in secret as they are not meant to be using them. The cooling a
detonation control is a fact -make sure that you only buy systems that
provides high water pressure as uneven distribution to the cylinders
will
make the entire installation in-effective.
2) Most serious Aquamist users design their own tank, some fancy design
has
multiple compartments as well as a small anti-surge tank below the main
tank. over half of people we know installed the outlet pipe on the
front of
the tank - a mistake they have realised later when they experienced
water
surge problems - don't make the same mistake.
3) You only need to use high energy coil if you run more than 25% of
water
to fuel - normal ratio is between 8-15%.
4) and 5) The Boost is limited to fuel quality, compression ratio. fore
10%
water, you can run approximately 4 psi or one compression ratio over
stock -
make certain that you have enough fuel. More water is needed if you
want to
run air.fuel ratio between 12:1 to 12.5:1 - best ratio for power.
6) You should advance the timing from stock approximately 3 degrees
from
stock - water slow down the flame speed by 2-3 degrees. You may be able
to
run even more advance due to the lowered combustion temperature. The
best
way to determine ignition timing for a given fuel grade is to monitor
the
knock and EGT -below 900C for cast pistons and below 950-975C for
forged
pistons.
7) Best position is immediately after the intercooler.
8) Size on jet is determined by working out your maximum fuel flow and
divided by ten.
9) You must treat the addition of a water injection system seriously to
get
the best out of it, planning with care and attention must be exercised.
We
are launching some new water flow sensing products on the coming UK
autosports show in January, preview on our site. www.aquamist.co.uk
Regards
Richard Lamb
erl@aquamist.co.uk
Hello Brian,
Thank you for contacting me.
I will go straight to your questions:
1) I don't know for sure that a 930 has used our water injection as we
very
rarely sell direct to customers and so far we have not heard anyone
contact
us - people tend to call us if there is a problem otherwise we don't
hear
from them. We have however supplied to a few Porsches as well as a few
GT
racers in secret as they are not meant to be using them. The cooling a
detonation control is a fact -make sure that you only buy systems that
provides high water pressure as uneven distribution to the cylinders
will
make the entire installation in-effective.
2) Most serious Aquamist users design their own tank, some fancy design
has
multiple compartments as well as a small anti-surge tank below the main
tank. over half of people we know installed the outlet pipe on the
front of
the tank - a mistake they have realised later when they experienced
water
surge problems - don't make the same mistake.
3) You only need to use high energy coil if you run more than 25% of
water
to fuel - normal ratio is between 8-15%.
4) and 5) The Boost is limited to fuel quality, compression ratio. fore
10%
water, you can run approximately 4 psi or one compression ratio over
stock -
make certain that you have enough fuel. More water is needed if you
want to
run air.fuel ratio between 12:1 to 12.5:1 - best ratio for power.
6) You should advance the timing from stock approximately 3 degrees
from
stock - water slow down the flame speed by 2-3 degrees. You may be able
to
run even more advance due to the lowered combustion temperature. The
best
way to determine ignition timing for a given fuel grade is to monitor
the
knock and EGT -below 900C for cast pistons and below 950-975C for
forged
pistons.
7) Best position is immediately after the intercooler.
8) Size on jet is determined by working out your maximum fuel flow and
divided by ten.
9) You must treat the addition of a water injection system seriously to
get
the best out of it, planning with care and attention must be exercised.
We
are launching some new water flow sensing products on the coming UK
autosports show in January, preview on our site. www.aquamist.co.uk
Regards
Richard Lamb
erl@aquamist.co.uk
01-06-2002, 08:32 PM
#3
As far as I have read, water injection is an old fashioned technology they used in the early 70's until they perfected intercooling. I run a big Koklyn intercooler and a K29 and am very happy with it. No danger of it not working...
A good book you might want to read is "Maximum Boost : Designing, Testing, and Installing Turbocharger Systems" by Korky Bell. It explains all the physics behind what you're asking.
Maximum Boost : Designing, Testing, and Installing Turbocharger Systems
A good book you might want to read is "Maximum Boost : Designing, Testing, and Installing Turbocharger Systems" by Korky Bell. It explains all the physics behind what you're asking.
Maximum Boost : Designing, Testing, and Installing Turbocharger Systems
01-07-2002, 11:50 PM
#4
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Water injection system are not obsolete, rally cars with big *** intercoolers use them, and at the moment those are the most sophisticated turbo cars out there. Porsche probably would use it if they could but it is outlawed for LeMans etc. Even most drag racing sactioning bodies have outlawed it or move you to another class! Hmmm I wonder why? Not because of fire hazard that's for sure. Outlawed with CART as well.
P.S. lets keep this our little secret ok.
P.S. lets keep this our little secret ok.
03-06-2002, 04:47 AM
#5
Bell's book is an excellent reference on the subject of turbocharging. However, he does have a bias against water injection. I'm in agreement with others on its place with boosted cars. The only downside is keeping track of the water and its associated circuitry, making sure you have some when its on boost. An efficient IC is a low/no-maintenance item.
I wouldn't suggest a lot of boost on any engine without adding instrumentation to verify things aren't about to melt inside your engine. That means monitoring exhaust gas temp, knock and air/fuel mixture. Melting a DSM engine (Mits) is one thing. Doing this on a 930 is very expensive.
Sherwood Lee
<a href="http://members.rennlist.org/911pcars" target="_blank">http://members.rennlist.org/911pcars</a>
<a href="http://www.seinesystems.com" target="_blank">www.seinesystems.com</a>
I wouldn't suggest a lot of boost on any engine without adding instrumentation to verify things aren't about to melt inside your engine. That means monitoring exhaust gas temp, knock and air/fuel mixture. Melting a DSM engine (Mits) is one thing. Doing this on a 930 is very expensive.
Sherwood Lee
<a href="http://members.rennlist.org/911pcars" target="_blank">http://members.rennlist.org/911pcars</a>
<a href="http://www.seinesystems.com" target="_blank">www.seinesystems.com</a>
03-07-2002, 05:54 AM
#6
RL Technical Advisor
This is a complex subject but I'd just like to chime in here and offer few points based upon operating, maintaining, and racing turbocharged Porsche race cars (935's) for a number of years.
1) Manifold pressures at, and above 1.0 bar in 930 engines are strongly discouraged. The CIS system is truly incapable of supporting these engines beyond 450 HP with the quantity of fuel and air without serious internal damage.
2) 935 engines used very different internals and were designed for 600-750 HP from 3.2 litres. Even with special and strengthened studs, heads, very different cooling, cylinders, rods, and many internal oiling differences, these engines needed total overhaul at or before the 24 hour mark depending upon boost pressures. Typically, these engines raced at 1.2 to 1.4 bar.
3) Water doesn't burn. Further, water inside the chamber cools the combustion process and displaces fuel and air needed for power production. Although cylinder temps and pressures are reduced to help prevent and supress detonation, this very same process lowers the power output unless other parameters are changed. For these air-cooled engines anyway, its much better to install and use a larger and efficient intercooler to control charge-air temps instead of water injection.
One of the very best ways to help supress and control detonation in the 930 is to install twin-ignition. This lowers the need for 32-34 degrees of ignition advance to 26-27 degrees for proper combustion and full efficiency. This translates into lower cylinder head temps, sharper throttle response and more torque. There are some other benefits too, that can be seen at:
<a href="http://www.rennsportsystems.com/~porsche/2a.html" target="_blank">Gasoline, Detonation, and Twin Ignition</a>
Hope this helps,
1) Manifold pressures at, and above 1.0 bar in 930 engines are strongly discouraged. The CIS system is truly incapable of supporting these engines beyond 450 HP with the quantity of fuel and air without serious internal damage.
2) 935 engines used very different internals and were designed for 600-750 HP from 3.2 litres. Even with special and strengthened studs, heads, very different cooling, cylinders, rods, and many internal oiling differences, these engines needed total overhaul at or before the 24 hour mark depending upon boost pressures. Typically, these engines raced at 1.2 to 1.4 bar.
3) Water doesn't burn. Further, water inside the chamber cools the combustion process and displaces fuel and air needed for power production. Although cylinder temps and pressures are reduced to help prevent and supress detonation, this very same process lowers the power output unless other parameters are changed. For these air-cooled engines anyway, its much better to install and use a larger and efficient intercooler to control charge-air temps instead of water injection.
One of the very best ways to help supress and control detonation in the 930 is to install twin-ignition. This lowers the need for 32-34 degrees of ignition advance to 26-27 degrees for proper combustion and full efficiency. This translates into lower cylinder head temps, sharper throttle response and more torque. There are some other benefits too, that can be seen at:
<a href="http://www.rennsportsystems.com/~porsche/2a.html" target="_blank">Gasoline, Detonation, and Twin Ignition</a>
Hope this helps,
