Holden 202 SC14 Carby LPG WI Considerations

[lawton20]

I am considering water injection for my supercharged Holden 202Ci 6cyl, circa 1980. It runs dual fuel, 98 RON Petrol and LPG (Autogas). Supercharger is a Toyota SC14.





I have been experimenting with systems to use the low temperature of the LPG fuel as it decompresses from the liquid state in the tank by regulating the rate of heating that prevents the system from freezing. There were gains, but nothing to write home about and the balancing act of a system that heats so easily and fast but cools slowly presents too much difficulty and not enough gain. I?m not ready to launch into direct injected liquid LPG yet, so I want to water inject.
Currently it is parked due to gearbox failure, but once I correct that I will look to improve my supercharger setup.

Improvements will include:
- Dedicated LPG fuel system by a Gas Research Carburettor.
Factory carby is currently retained to support installation regulations and certification of the LPG system. The carby is small, so it introduces vacuum during wide open throttle between it and the supercharger inlet at moderate to high RPM.
Petrol is almost useless in this draw through supercharger system, it sticks to the rotors of the supercharger at low RPM, causing the system to run lean until the rotors are saturated with fuel. When RPM is increased, fuel is thrown off the rotors centripetally and causes the system to run rich until a new equilibrium is established. LPG has a higher RON rating, is cheaper, and being a gas it completely mixes with air and does not stick to the supercharger rotors!

- Cold air intake
Less restrictive, cooler air can be piped in more easily to a GRA carb because it is side draft, the original Stromberg is down draft with hat style filter.

- Introduction of a bypass valve.
Currently there is no bypass valve to allow the supercharger to ?freewheel?. This seems to have resulted in a lot of sprocket and bearing wear on my supercharger making it very rattly.

- Ignition timing computer.
I?ve tried to fit one before, but due to system noise being recognised as crank angle sensor pulses, it could never rev past 1500RPM. The original plan was to have two timing maps to suit each fuel. Since petrol will be removed, the dual maps are not required. However being able to boost retard will be useful.

- Smaller supercharger pulley.
I have a few pulleys I can use, but I can only achieve a maximum of around 5PSI boost on a good day before detonation on LPG and lower on petrol. Detonation is also more frequent on petrol due to it sticking to rotors and detonation issues are more apparent due to inefficient supercharger type, restrictive throttle body, hot intake air temp and lack of intercooler.

Intercooling or a more efficient supercharger are options for my situation. But for this car it isn?t worth redesigning the intake system post supercharger, and I quite like the way it looks at the moment.

Enter Water Injection.
I love the Aquamist kits for their supreme quality and the FAV based design, resulting in accurate progressive water delivery. Pioneers of fuel injection found PWM of valves with regulated pressure behind them to be most effective for accurate delivery of fuel, great for WI too. I?m hoping WI will be enough to cool my intake charge and allow me to tune beyond 5PSI of boost and improve power. Economy gain is always good too.

Since I will be relying on the WI in my tune for my engine to survive, a good WI system is required. It needs to come on quickly and reliably because boost is instant with a roots supercharger. I?m also a gadget man and electronics engineer, so HFS3 with gauge is the kit for me.

I have come to the forum for some advice because my fuel delivery system is not electronic, and would like some advice from others experienced in using HFS3 systems on engines without ECU?s. If I ever make it to direct liquid injection of LPG, I will have an ECU, but for now I don?t.

My proposed setup:
- Trigger by boost, I will need to use a MAP sensor
- 3 jets post supercharger at the beginning of each of my 3 intake runners
- Checkvalve jets to combat pressure differences in intake runners during vacuum conditions.
- Pump in the engine bay. The car is a ute (pickup for the Americans) so no trunk.

Proposed Aquamist equipment list
- HFS3-V3 kit (806-063)
- 0.3mm Checkvalve Jets (806-493C) Qty 4 (one spare/future aux throttle body injection)
- 4 way manifold (806-403)
- Jet adaptors (806-357N) Qty 2 (+ two supplied in kit)

Questions:
- How does one adjust water delivery for boost-only controlled systems? IDC systems are well covered by the instruction manual, but boost-only is not. I will be setting the jumper system to trigger by ?MPS? and cutting/soldering the ?MPS? link on the controller board. Any other advice on how to tune the progressive water delivery?
- If I?m cruising at 2000RPM and plant the foot, full boost is immediately available (less than a second). How fast can the Aquamist HFS3 system begin water delivery?
- Are extra filters than the ones in the jets and one in the tank important? My engine will swallow things larger than 30?m with ease.
- Can the HFS3 kit be sold without jets for a discount price, or sold with checkvalve jets at a kit price?
- What is the difference between Checkvalve Jets P/N: 806-493C and P/N: 806-493C+? More flow?
- Does the Aquamist pump require shielding when mounted in the engine bay? I don?t expect it to get hot, but if it?s designed to be trunk mounted and I put it in the engine bay it could get wet or covered in grime. Will I have to make an enclosure for it?
- When running strait LPG, my engine valves will need lubricant (such as flashlube). Can the Aquamist system deliver anything like that?
- Any suggestions to my proposed system?

[Richard L]

The same method is used for boost. Set the "thres" and "gain".

1. You need to cut the IDC link on the underside of the circuit and solder link the MPS. The system is now solely based on MPS.
a. Move the IDC jumper link over to MPS.
b. If you don't have MAP sensor on board, you need to purchase one.

Rest of your questions:

2. Smaller filter less than 50um will clog quickly. The filter supplied is for the jets, not intended for the engine.

3. Not normally, depending on who you purchase the system from. Some suppliers only sell kits. If you purchase from aquamist directly, we can credit the standard jet against the filtered jet. But the filtered jet only apply to the smaller 0.3mm nozzle.

4. The smaller jets comes with three flow rates A, B or C (commonly supplied). C+ jst spray a bit more. For aquamist, you can specify the preferred flow rate, we can make it for you at the same price.

5. The casing is zinc plated steel, in time, it will rust as the Zinc plating depletes. The cable gland must be sealed or water will trickle into the pump and corrodes the bearing.

6. If the lube is hydrocarbon based and gets into the aquamist system, it will destroy the pump and valve within mijutes. All rubber seals are EPDM based, it will swell up like a balloon when in contact with any hydrocarbon.

[lawton20]

Thanks for the response Richard, one question didn't get an answer though:

- If I’m cruising at 2000RPM and plant the foot, full boost is immediately available (less than a second). How fast can the Aquamist HFS3 system begin water delivery?

[Richard L]

I think around 10mS