Craigorypeck
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| posted on 12/1/14 at 04:31 AM |
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triggering water injection system & advice
My m45 charger is spinning way out of its efficiency range above 6000 engine rpm and its just heating the boost and detrimental to power up top.
Gearing down isn't an option as there wouldnt be any point running 2psi and a bigger charger wont fit.
On a track day I couldn't avoid engine knock from 6+k (8k Redline)
I pulled the ignition timing way back to around 7 degrees on the megajolt and it still pinged its nuts off and just seemed to hit a wall. Running
11.5:1 afr so not lean.
All the water injection kits be it off the shelf or diy ive seen are triggered by boost. But my supercharger setup is full boost from idle upwards.
What I'm trying to achieve is a progressive water injection setup that's controlled by IATs irrespective of boost.
Can this be done?
Or should engine revs via megajolt be the sole controller with a preset amount of water injection per rpm regardless of IATs?
And where's best for a water injector? Pre charger might help with cooling it and help seal it but the intercooler will fill with water? Or
after intercooler pre plenum?
I've bored you all now lol!
But any advice would be most welcome.
Cheers.
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snakebelly
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| posted on 12/1/14 at 08:57 AM |
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Funnily enough I have been having the same thought on our supercharged Volvo Tiger project, will have to see if the DTAS60 can do it, I think I can
probably use one of the optional triggers but am away at the moment, if you make any progress let me know as all the googling in the world only seems
to bring up pressure triggered systems.
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Mikef
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| posted on 12/1/14 at 09:22 AM |
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I think Messerschmidt did this on their injected 109 engines in the forties. Might be worth searching that line. I did have a look at this years ago
when I ran a supercharged 350 bike. As I was running 50% nitro , I just decided to mix some water 1% approx in the fuel, as it would mix with nitro
and methanol. Smoothed the engine out a treat.
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snakebelly
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| posted on 12/1/14 at 09:29 AM |
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this makes interesting reading:
http://www.sxoc.com/vbb/archive/index.php/t-53466.html
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dave_424
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| posted on 12/1/14 at 10:25 AM |
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I don't know if megajolt has programmable outputs for things like launch control, fan control, fuel pump etc. But on my megasquirt I could set
up an output control that switches a relay when intake temps get above a certain level.
If you would be okay with water/meth coming on at a certain RPM, you could get creative with a shift light and make that switch a relay at a certain
RPM.
Dave
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BaileyPerformance
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| posted on 12/1/14 at 01:24 PM |
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If your running an intercooler now what is your IAT at full load? If reasonable (less than 50) then water injection may not solve the det problem, you
said your total timing is 7 degrees, what boost are you running?
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Craigorypeck
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| posted on 12/1/14 at 05:17 PM |
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Hi All.
I dont actually know what my IATs are, but after a good blast its well toasty on the engine side of IC.
Running a modest 6psi into a 10.8:1CR YB, I do suspect IATs are the problem as the m45 is running quite a few thousand rpm out of its efficiency range
to get any decent boost. I know my basic ingredients are wrong but I shall persevere with trying to improve what i have for now.
The shift light idea is a good one, something I had thought about. It would be a preset flow amount tho.
There are 4 shift light outputs that could be utilized, first one to activate water pump and then maybe have more than one water injector, basically
adding water in (2-3) steps rather than progressively as engine revs increase...
This sounds like quite an easy DIY option, few relays, pump, certain flow rate nozzles, water injection solenoids... patience!
The IAT trigger idea would be more specific to weather and driving conditions and basically work like a radiator fan switch, but i see a water volume
control issue with this idea, it would only activate like an on/off setup.
Unless having a temp sensor up stream from the water injector supplying a rising rate signal to water pump voltage or water flow control, so
effectively adding more water as temps increase if that is possible? This doesn't sound as DIY friendly to me as the above option... maybe
someone would have an idea on how this could be achieved?
Both these ideas could have a washer bottle with low warning light hooked up to trigger a rev limit or retarded ignition map as a safe guard to
running dry.
Lastly, how to calculate the amount of water to add? can it be calculated to the amount of fuel flow? which might be difficult to work out on a carbed
engine or just monitor IATs downstream and tune accordingly?
anyways just thinking out loud.. 
[Edited on 12/1/14 by Craigorypeck]
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