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Old 13th May 2005, 07:51 AM   #41 (permalink)
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Quote:
Originally Posted by SteveN
i prefer to rely on GOOD mapping so the car dont det
with good mapping you can advance the ignition timing when the water is running to get more power.

Drew
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Old 13th May 2005, 09:59 AM   #42 (permalink)
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Drew, indeed your right, but unfortunatley I still dont have anywhere near enough faith in relying on W.I. to do that.

When it comes down to it, if your intercooler is doing a good enough job (ie kepping charge temps far less than 40deg) it should have no real effect anyhow, and id much prefer to have a decent intercooler setup first and foremost.

Pre-compressor injection I can see an advantage of (at least in theory) as however well the intercooler cools the charge, its still incredibly hot (and hence not very dense) pre-intercooler, somthing pre-compressor inj should help, giving an obvious advantage.
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Last edited by SteveN; 13th May 2005 at 10:05 AM..
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Old 13th May 2005, 10:21 AM   #43 (permalink)
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Quote:
Originally Posted by SteveN
Drew, indeed your right, but unfortunatley I still dont have anywhere near enough faith in relying on W.I. to do that.

When it comes down to it, if your intercooler is doing a good enough job (ie kepping charge temps far less than 40deg) it should have no real effect anyhow, and id much prefer to have a decent intercooler setup first and foremost.

Pre-compressor injection I can see an advantage of (at least in theory) as however well the intercooler cools the charge, its still incredibly hot (and hence not very dense) pre-intercooler, somthing pre-compressor inj should help, giving an obvious advantage.
Steve, I think you'll find that water acts as an anti detonant, and regardless of IC efficiencies, or charge temps, can allow higher BMEP's without detonation.
Studies have been done on it's effects, on a lab engine fed with cool compressed air. It effectively increases the octane of the fuel mix, so is not just used to lower charge temps.

I agree with you on reliability, melting pistons if the WI fails.
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Old 13th May 2005, 10:28 AM   #44 (permalink)
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i have a DTA P8 ecu and one of aquamists water flow sensors.

the flow sensor outputs 0-5v = 0-450ml/min water flowing past it.
the DTA has a 0-5v input with fuel and ignition compensations referenced to it.

so when the water is flowing, the sensor detects it, the ecu compensates for it.
no water flowing, no ignition advance.

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Old 13th May 2005, 10:49 AM   #45 (permalink)
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Is this on an RB engine Drew?
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Old 13th May 2005, 10:59 AM   #46 (permalink)
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For me its all the balance between performance and cost, ie value for money, and trying to decide the most cost effective way to use W.I. (if at all, obviously) is making my head hurt...
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Old 13th May 2005, 12:21 PM   #47 (permalink)
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I have used an Aquamist WI injection pump on my car and have experienced it failing.

I did not at the time have any means to judge whether the pump was working or not, so it is a bit scary if you are running on the limit of ignition advance / detonation.
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Old 13th May 2005, 01:09 PM   #48 (permalink)
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yeah aquamist kits arnt cheap. i think you'd need around £500-600+vat for a useable kit with the extra fail safe features. plus a water tank in the boot.

not knowing how much extra power you would get from it makes it a little difficalt to justify the cost.

no ive not used it on an RB mate

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Old 13th May 2005, 02:40 PM   #49 (permalink)
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ERL pumps are notoriously unreliable, Flowjet pumps are allegedly the ones to use...

http://www.randbmotorsport.co.uk/sho...?ProductID=140
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Old 13th May 2005, 03:52 PM   #50 (permalink)
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only thing that would concern me with that is its very low pressure.

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Old 13th May 2005, 04:08 PM   #51 (permalink)
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pumps dont do pressure, they do flow, pressure is determined mainly by pipe/jet size.
I think the person that actually wrote that just dont know what they on about...
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Old 13th May 2005, 05:10 PM   #52 (permalink)
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flow is always rated at a pressure value. Doesn't mean that the pump can't work under higher pressures, just a reference for comparison. The flow drops off as the pressure rises. This can be very rapid on some pumps, so you need to find out the flow rate at the pressure your going to operate the thing at. That is if you know in the first place.
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Old 13th May 2005, 10:33 PM   #53 (permalink)
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Quote:
Originally Posted by Hugh Keir
kingsley,

I haven't grasped why you would want to inject pre compressor.

Traditionally you use the intercooler to remove as much heat from the air as possible, post intercooler inject the water / methanol and use the latent heat of evaporation to pull the temps down further.

Injecting at any time pre intercooler means that you are reducing the temperature differential at the intercooler which is kinda self defeating.
Hi Hugh,

I am not explicitly saying that it is or isn't good to inject pre-compressor; I was merely passing on some info from a friend of mine who tried it.

I agree that the intercooler would remove more heat from the air if it was to enter at a higher temperature as it is the temperature differential that 'drives' the heat transfer.

However, what my friend discovered was nevertheless interesting.
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Old 13th May 2005, 10:37 PM   #54 (permalink)
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Simply having a pressure switch to turn on the WI is IMHO quite crude. If you hit threshold boost at 4000rpm then by and large you're going to get twice as much water into the cylinders per cycle at 4000rpm than you are at 8000rpm. At higher rpm, you will be running a 'weaker' water mix.

I'm wondering whether a staged system might be more optimal; the system could be triggered on boost and then the rpm would determine how many nozzles to activate. The mix vs rpm graph would still be 'steppy' but would be a closer approximation to a straight line than a single nozzle system.

Not sure how precise an art this is.
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Old 13th May 2005, 10:43 PM   #55 (permalink)
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Regarding pump reliability/failures, someone else I know once put a 3.0 V6 into an Astra and then twin turbocharged it. He did a few experiments with WI and had his fair share of problems.

One problem he had was the pump failing. Another that the nozzle blocked up (presumably due to not using a proper water filter).

In the end, he had a pressure sensor in the water line. If we refer to X as the pressure in the water lines with a properly working pump and a non-blocked nozzle, then he rigged up a system to check whether the pressure veered much from this. If the pressure was below X then either the pump wasn't working or there was probably a leak somewhere. If the pressure was above X then the nozzle was getting blocked. A pressure of X indicated maximum water flow.

I'm not sure whether he linked this to any automatic boost cut or whatever; he had so many other reliability problems with the whole thing that he gave up after a while. Still, it was an interesting idea.
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Old 14th May 2005, 09:45 AM   #56 (permalink)
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i see, i thought 3bar was its maximum. inject that into the intake with 1bar boost pushing the other way, you only get 2 bar water pressure through the nozzle.

from what ive seen you need to get the water at around 10-15% of the fuel you pumping in.
so lets say you have 6 x 700cc injectors.
6x 700 = 4200cc/min max flow
at max the injectors might run at 85% duty cycle.
4200 x 0.85 = 3570cc/min

you need 15% water to fuel so
3570 x 0.15 = 535.5cc/min max water flow.

the water is controlled by a valve which mimics the injector pulse. in theory you will always get the correct water to fuel percentage.
http://www.aquamist.co.uk/sl/plist/p...9/806-009.html

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Old 14th May 2005, 09:54 AM   #57 (permalink)
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i had some fairly in-depth conversations with Paul Waite on Evo forum a few years back about WI and he was dead against it, having known on more that one occasion of nozzles getting dirty and "dribbling" water into the engine, ruining the rings etc.
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Old 14th May 2005, 03:33 PM   #58 (permalink)
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Due to a few things ive heard Paul Waite say in the past that I know for a fact are total and utter shat, unfortunatley i have very little faith in what he has to say about cars and engines.

How the **** can it dribble water into the engine anyhow? Makes little if any sence...
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Old 14th May 2005, 04:01 PM   #59 (permalink)
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just repeating what i was told.

from what i could gather the water no longer atomised and the nozzle dribbled, and this water found itself into the inlet and did damage.

he also didn't like the fact you cannot monitor the nozzles performance.


was a few years ago mind
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Old 15th May 2005, 10:32 AM   #60 (permalink)
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The next edition of the GTR Owners Club magazine "Skylines" has an article about Water Injection.
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