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  #11  
Old 27-09-2016, 07:09 AM
sambeeb sambeeb is offline
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Default Re: WI causing knock?

thanks for that. That is an awesome post with a tonne of detail to pour over. I've since corresponded with some tuners who are familiar with my motor. They say that 4.5 degrees pull as seen in ross-tech VCDS is not necessarily 4.5 degrees pull due to solid knock - the knock sensors can apparently decipher imminent knock and pre-emptively pull timing. This means (if true) that I can run much more timing than I had previously thought safe and so there might be potential yet for water injection on this tune. Thanks for the advice so far and i'll let you know how I get on.

thanks
sam
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  #12  
Old 28-09-2016, 05:59 AM
sambeeb sambeeb is offline
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Default Re: WI causing knock?

I just wanted to be absolutely certain of something. Are you saying that at 80-100psi, that a 0.4 "C" would atomise better than an "A" because the finer nozzle needs more pressure to work correctly?
Most likely my next step will be moving a single nozzle post throttle body and running a weak meth mix. Hopefully this way the faster meth evaporation will give me better inlet coolling than I have now, and in conjunction with a better atomising bigger nozzle (if I read the above posts correctly) get more water into the cylinders.
If that gets things heading in the right direction then i'll look at committing the funds to direct port.
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  #13  
Old 28-09-2016, 11:05 AM
rotrex rotrex is offline
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Default Re: WI causing knock?

The C Type mainly provides a higher flow rate. Just use the HSV of FAV to dose the spray.
My Rover distributor ignition copes fine even with 100% flow through 4x 0.4mm C jets at 7 bar rail pressure.
I have since remapped to 85% flow rate as otherwise on track usage gets to high. you are on the throttle all the time. On the road minus sustained WOT on the autobahn, I would not bother with low flow. Even a small 4 liter tanks lasts for a fair bit of very spirited driving.

if you want the most effect in the cylinder, go direct port. This is the way forward, if you are knock limited.
if you are hampered by a low efficiency of your (too small) turbo, consider pre turbo injection.
if you are hampered with poor charge cooling and excessive IATs despite a efficient turbo, consider post IC injection.

in general, unless you inject substantial amounts of methanol, the IAT reduction from the injection is not that huge. a litte 50ml/min of methanol won't make your car go much faster.
once you inject 500 ml/min of a 50:50 mix or more, things change.
but unless you inject direct port or use a very finally atomising air assisted nozzle pre-turbo, litte of the water will make it as droplets into the cylinders, at least not uniformly in all of them. The methanol vapour will. This is why the mix works out so great for many and makes jet location less critical IMHO.
Streams of water will pass the engine with litte to no effect. streams of methanol will still oppress knock as it acts as a high octane fuel and evaporates completely in the cylinder.
Water won't.
Direct port with the jets in a similar position as the fuel injectors devoid of turns and bends for the spray to take, the water also will do its thing, in the cylinder. The result is that you get the same knock suppression at a fraction of the flow.
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  #14  
Old 28-09-2016, 10:27 PM
sambeeb sambeeb is offline
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Default Re: WI causing knock?

Despite the issues i've raised, excessive IAT's were the primary reason that I fitted the post IC WI in the first place. I didn't want to run meth from there though worried that it could affect the throttle body circuitry. In high ambient temps with water alone I did succeed in dropping IAT's from 50 to 40 degrees as measured across the short 10 inch distance from the IC outlet to the throttle body temp sensor. I understand now why I am not able to get rid of timing pull though. The plenum had always felt cold to the touch and I'd assumed from that that plenty of water in droplet form would have been getting into the cylinders, but now I see this was more than likely due to wet down walls than anything else.

"if you are hampered by a low efficiency of your (too small) turbo, consider pre turbo injection.
if you are hampered with poor charge cooling and excessive IATs despite a efficient turbo, consider post IC injection"

Since my turbo is basically INefficient at the degree to which its being pushed and post IC water injection is not having the desired anti knock effect, maybe the best thing will be pre compressor injection then. I had looked long and hard at boost pressurised systems and liked their simplicity and the fact that in a purely mechanical system you could achieve flow somewhat proportional to boost.
Can I ask a question on that topic then - it would be a system that I'd only use at hillclimbs so the IC would have to remain in place for when its street driven. Would the presence of the IC have an bearing on whether or not I run water alone or water/meth? Yes the IC is small side mount (similar to the golf mk4 setup) but it is always kept cool with a water spray, IC fan and good ducting and runs are less than 1 minute.

thanks
sam
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  #15  
Old 29-09-2016, 10:49 AM
rotrex rotrex is offline
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Default Re: WI causing knock?

I have observed condensation of pre compressor water methanol spray. it shows as temp fluctuation on the IAT sensor past the charge cooler.
This only happened for flow rates past 100cc/min.
Rice racing's work around to enhance efficiency is to inject as far away as possible from the turbocharger. He injects in the the air filter. You have to have smooth pipes without edges and steps as this would puddle the water.
this arrangement generates a very fine mist. the methanol readily evaporates, cools the intake charge and leaves a very fine water mist. Much of this mist will evaporate as it passes through the compressor. what is left, will enter the cylinder.

The advance you get from such a set-up vs. direct port is that you maximise air cooling and with it air density. you won't have too much water mist in the cylinder anymore.
The advance of direct port vs. the air assist in the filter is that you maximise knock suppression in the cylinder. The way the engine won't mind higher IATs regarding knock. I won't pull significant timing before 70C IATs.

In generell, you could consider spraying a mix contains 70% methanol by weight into the turbocharger. this would drop intake air temperatures a lot more than water.
Unless you not always stop the engine right after WOT with the intake path soaking wet, there will be no issues. The engine heat, the vacuum and air flow in the intake path will have everything evaporated by the time you rolled to the parc fermé after a hill climb and finished your engine cool down.

you usually make more power with a methanol mix than on water alone. Mapping is easier as less timing needs to be added and AFRs more max power are more in the common range of 11.8 to 12.5.
Pure water that actually enters the cylinder as spray often works better at leaner AFRs.
water in combination with rich AFRs such a 10-11:1 does not work well. it does not make power from slow burn speed and then starts knocking as you advance the ignition.

Last edited by rotrex; 29-09-2016 at 10:53 AM.
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