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Old 02-12-2017, 06:34 AM
mm3boost mm3boost is offline
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Default E46 M3 WMI Design

Hey Guys,

I'm about to order an HSF4 WMI setup for my maximum PSI E46 M3. My current specs are:

Precision 6870 turbo / .82 AR
3.5" straight exhaust, no restrictions
3" Intake
ID1050cc injectors
Currently 9 psi low boost pump gas 500 rwhp / 385 tq
High boost is set to 19 psi on MS109 ~730 rwhp

Goals:
With WMI, I would like to be able to run 13-15 psi (550-600 rwhp) on pump gas and 21-24psi (750-800 rwhp) on MS109.
At the moment the plan is not to tune for the WMI, just to add boost and use it as a knock deterrent.



The challenge of this setup is the intake manifold design has a large surge tank and the MAF sensor sits right before the manifold as well. The only position I see that is of value would be direct injection into each throttle body, I've attached a picture of my planned placement.


My main question is that the several of the technical papers I've read on this forum support data that shows the best water/fuel mass ratios to use are between 100-150%, but the Aquamist website claims 10-25% depending on your WM ratio. I'm unsure what injectors to purchase at the moment until I get a better clarification on what the proper ratio to run.



Regards,


~Anthony


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Old 03-12-2017, 08:54 AM
Richard L Richard L is offline
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Default Re: E46 M3 WMI Design

As seen on the charts below, it is not practical to inject high percentage. Excessive cooling will rob power. Also putting undue stress on the stock ignition system (high % of water).
You can inject high percent of w/m but make sure you have a good flow monitoring setup to reduce power to a safe level should the wmi system fails.




10Kg of air, Gasoline's latent heat capacityof 350KJ/Kg

Water's latent heat capacity of 2256KJ/Kg

Methanol's latent heat capacity of 1109KJ/Kg



Injection water at different ratio to fuel at 100% water and 75% Water/25% Methanol. You can see the at 100% water injection, only 3% of w/f fuel ratio is enough to replace 2.5 point of a/f ratio (dotted line). As soon as 25% of Methanol is added, the a/f ratio is dropprd to 12.0 - loosing some cooling capacity









Each of the following chart show a 25% percent increase in Methanol concentration of the mix.







lastly, just methanol is added and no water. The chart on the right is 100% water









The two charts show (first and last) that you will require to inject twice the amount of methanol to equal the latent heat of water alone. Methanol is relatively low cost and very effective as a coolant so what is the problem?



When higher concertration of methanol is injected, you need to lean your engines a/f ratio to accomendate the extra fuel or your engine will bog down and loose power. Consequentially - one runs the risk of putting the engine into heat stress if the supply of methanol is suddenly interrupted. Injecting water does not affect the a/f ratio. It appears that 50/50 mix has the best of both worlds.


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Old 04-12-2017, 06:14 PM
mm3boost mm3boost is offline
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Default Re: E46 M3 WMI Design

Wow, thank you for that great info.

Can I make the assumption that the amount of heat absorption is a direct correlation to knock prevention?

My goal is to add power through knock prevention alone and not timing/afr advancements; therefore, with your comments it would seem that 100% water would be a better method over 50/50 mixture?


~Anthony
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Old 04-12-2017, 11:17 PM
rotrex rotrex is offline
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Default Re: E46 M3 WMI Design

Sorry,
but i'd not add 60% power without retuning.

50:50 mix by weight is the easiest to tune.
You nozzle locations will work. Just place them dead on top of the little runners in line with the fuel injectors.

Regarding injector size, Richard's rule of thumb works well. Inject some 1.5ml/min per HP. For you that ends up at some 1000ml/min at full chat.
The Aquamist 0.5mm checkvalve jets should work well.

Knock suppression happens to a significant part through mist being present near the edges of the combustion chamber. This is where it knocks the most as shockwaves hit their reflection from the cylinder wall leading to peak pressures. If the mist is non-uniformly introduced into the chamber, it does not get to all the edges, especially front and back of the cylinder well. The spray direction and location should resemble that of the fuel injectors. As you cannot point towards the intake port like a fuel injector, spraying perpendicularly downwards works well enough.

This picture illustrates a typical fuel flow from a port injection engine. Fuel nicely spreads over the front and rear portion of the intake valves. you need to maintain that balance.
Injection from the bottom or the side causes the spray to only partly fill the chamber. Only from the top, the spray has to take the least turns and covers the intake valves in the most uniform way.



The rest of the fine mist helps reducing peak temperatures during the compression cycle and while the flame front runs across the combustion chamber.

Ignition timing will have to be significantly increased with that amount of mix being injected. With pure water even more so. Flame initiation and flame propagation speeds are reduced in the presence of water.
Higher boost will partly compensate for this.
You will also have to pull some fuel injecting significant amounts of 50:50 mix.
The engines commonly like to run at lambda 0.75 to 0.9 under water. Any richer than 0.75 and often achievable power drops.

If you inject much less, it also has much less effect.

These numbers of 100% water to fuel came from WW2 experiments. The tractor pulling guys use it, but for the road, it is impractical. It would only be worth the trouble if you would run way more boost than what you anticipate, e.g. 45 PSI or higher.

Regarding the numbers and their cooling capacity. These numbers are only realistic if all the fluid evaporates. Water evaporates really slowly, even in a combustion chamber. Droplet lifetimes exceed 10s of milliseconds in a cylinder once the droplets are bigger. This is why direct port injection with a good injector position works so well and why nozzles in front of a curved intake manifold have so little effect. The droplets hit the walls in the turns and form a stream of fluid. This passes right through the engine.

The Aquamist failsafe systems with flow sensors work really well. You can have the HSF controller open the boost control valve of the waste gate dropping boost to spring pressure.


Just read the thread "Questions on my direct port meth setup" a few posts down. He applied some of the above with great success (=power) in a Mitsubishi Evo in Singapore.
He gained 132HP at the wheels and has now more than 620HP a the crank. He runs 30PSI on track. 4x 0.5mm jets.

http://www.youtube.com/watch?v=uD8Xq8RF_qM

Your engine is pretty much a 50% bigger version due to 2 extra cylinders. But you have to tune. Going untuned from 500HP to 800HP will very likely blow your engine.

Last edited by rotrex; 05-12-2017 at 12:05 AM.
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Old 05-12-2017, 02:39 PM
mm3boost mm3boost is offline
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Default Re: E46 M3 WMI Design

Thank you guys, you've answered my main questions.

My last question is a thought I had recently about the gains from cooling the intake charge. Where I currently have the injectors planned to be installed there won't be much of an intake cooling effect as the majority of the water will be directly into the throttle bodies and introduced into the chamber (which is the intent). Would it be overkill to install two additional injectors at the bottom of my intake plenum (see picture in first post) to lightly mist the intake plenum surge tank which might be able to cool some of that turbulent air in that area?

I haven't been able to find much data on what an intake plenum surge tank really does so I'm not sure how the air truly flows in that lower portion but assuming the air swirls down there prior to entering the throttle bodies I imagine that would be an opportunity to cool the charge? I don't see any negatives to the concept but figure'd I'd ask the experts.


Thanks,


~Anthony
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Old 05-12-2017, 05:42 PM
Richard L Richard L is offline
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Default Re: E46 M3 WMI Design

do you have an intercooler?
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Old 05-12-2017, 10:43 PM
mm3boost mm3boost is offline
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Default Re: E46 M3 WMI Design

Quote:
Originally Posted by Richard L View Post
do you have an intercooler?
Yes but the MAF is placed right after the intercooler and before the intake surge tank.
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Old 05-12-2017, 11:17 PM
rotrex rotrex is offline
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Default Re: E46 M3 WMI Design

IMHO there is litte to be gained. You willl have a hard time getting a good distribution across the 6 cylinders. Any droplets hitting the wall of the chamber will be cooling the metal, not the gas. As this vapor needs space, the oxygen concentration drops.
Only droplets evaporating in gas lead to a significant density increase as they cool the gas. Cooling the walls get you the vapour volume, but not the cooler gas with its higher density.
I posted a scientific publication in the publication section of this forum on this effect.

Unless you have intake air temperatures exceeding some 60C under sustained WOT, I would not bother. Compared to the direct port jets, there is litte extra effect.

Last edited by rotrex; 06-12-2017 at 07:35 PM.
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Old 06-12-2017, 09:41 AM
Richard L Richard L is offline
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Default Re: E46 M3 WMI Design

Ideally the jet should be place immediately after the IC.
Everytime you snap the throttle shut, water will be everywhere due to the turbulance state of air within the charge pipe. Reason why the location of MAF location is not important.
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