Water injection

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Russbif
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Water injection

Post by Russbif »

Whereabouts should I fit my injection nozzle, post charger and pre IAT or between IAT and inlet manifold?
hybrid
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Re: Water injection

Post by hybrid »

Mine is post charger, but before IAT so the sensor can compensate for the air temp changes.
If you go post charger, just make sure the injection is working at enough pressure to overcome boost pressure.
Do not load someone elses tune and expect it to work for you!
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Russbif
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Re: Water injection

Post by Russbif »

Thanks, hadn’t thought about boost stopping the spray
R100RT
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Re: Water injection

Post by R100RT »

Best water (or water/ meth) injection results are from a high pressure delivery, finely atomized.
Pretty sure that's what you guys would be working with but just saying. Even working with limited real estate on a motorbike there are miniature pumps that can get you up above 100psi without taking up much room.
1983 BMW R100RT Motorbike
Turbocharged - Water/Meth
Sequential Ignition & Fuel
"Perky Sleeper" that excites bike enthusiasts once discovered (or being passed)
Newest project - 1995 BMW K75 is V3 Microsquirt, "Turbocharger - Of Course"
rickb794
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Re: Water injection

Post by rickb794 »

Try an Espresso machine boiler feed pump and a cigarette lighter sized inverter to power it?
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pmbrunelle
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Re: Water injection

Post by pmbrunelle »

Not sure how I feel about the IAT being placed after the turbo.

I tested the response time of an open-element GM IAT.

I placed the sensor in an airstream (the suction of a vacuum cleaner).

Then, all of a sudden, I blew hot air (from a hot-air gun, the kind used for heat-shrink tubes) onto the sensor.

Response time was long... as in 5 seconds for a step temperature change. So I don't think it's useful for measuring the temperature rise of compression.

That said, I did recently see a factory turbo setup, with speed-density fuel injection, and the IAT in the intake manifold.

On my own car, I will put the IAT upstream of the compressor.
R100RT
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Re: Water injection

Post by R100RT »

rickb794 wrote:Try an Espresso machine boiler feed pump and a cigarette lighter sized inverter to power it?
That's very novel, probably a diaphragm type pump? I utilize a very miniature Peerless diaphragm pump in 12v trim - it is sized for proper flow rates on my size of engine etc.
Regarding IAT post turbo, wasn't really aware of problems in temp lag readings, when you utilize the open element GM style. My "Post Turbo" readings seem to follow quite accurately on hard roll ons, but equally haven't noted ill effects on behaviour so hasn't been on the radar.
If you read temp pre turbo it will never react to the heat build that compression brings (regardless of how efficient a cooler might be).
1983 BMW R100RT Motorbike
Turbocharged - Water/Meth
Sequential Ignition & Fuel
"Perky Sleeper" that excites bike enthusiasts once discovered (or being passed)
Newest project - 1995 BMW K75 is V3 Microsquirt, "Turbocharger - Of Course"
pmbrunelle
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Re: Water injection

Post by pmbrunelle »

In a real car, maybe you have more air velocity than what I had with the shop-vac. With air blowing by the sensor faster, it might have a quicker response time.

For an intercooled turbo, I think I would just go with MAF.

For a non-intercooled turbo, my hypothesis is that you don't need to measure the heat rise due to the compression of the air.

Suppose that to hit 175 kPa MAP at a certain RPM, your compressor needs to operate at a pressure ratio of 2. From that pressure ratio and mass air flow rate, you know that your compressor was running at 72% efficiency.

If you know the adiabatic efficiency, then the compressor's outlet temperature can be determined, based on the inlet temperature.

So if the above always repeats, then you wouldn't need a post-compressor air temperature measurement.

So the question is, which evil do you prefer to live with:
1. The response time of the sensor (will cause a time-dependent error as you roll into boost)
2. The non-repeatability of the compressor's heat of compression (causes an error depending on pressure ratio, but does not have any relation to time)

The practical effect of a pre-turbo measurement will be that the VE table values will be lower than expected in boost, because there is not the leaning effect of measuring hot, low-density air in boost.

I decided that I didn't like post-turbo due to time lag... not sure pre-turbo is gonna be any better though. I'll find out!
hybrid
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Re: Water injection

Post by hybrid »

There is no way I would go pre turbo/supercharger with a temp sensor.

I saw 70C+ air from my supercharger going into my engine, which is why I added water injection. No way would I have known that otherwise, perhaps until something was damaged.
Now I can use IAT ignition retard to pull some timing if things get too hot.

At the track, I saw my intake temps climb within a second or two of boost being applied.

For the record, I'm using a 31 series sea flo marine pump.
http://www.seaflo.com/en-us/product/detail/603.html

In this pic, you can see intake temps drop pretty much as soon as the meth/water starts to inject (at 3-4psi).
Image

So I can't say I'm seeing the delays you have seen.
Do not load someone elses tune and expect it to work for you!
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