Preturbo 335i Strange Results

[Richard L]

Originally Posted by rudypoochris

So basically the shaft speed may be less, but the work is around the same? Then really the turbo is seeing less "damage" due to overspeed but roughly equal thrust loading wear?

Methanol comes on at a boost switch set too low atm (8psi). It is not progressive at the moment, but I may switch it to be progressive with boost. The check valve makes it not progressive since the tank is pre-boosted to whatever the last pull left it at.

Are other people seeing reduced shaft speed or reduced work with pre-turbo meth?

Although water is heavy but compared to the mass of air going through the turbo, it is much less. There will not be to much variation on the BCV's PWM.

You cannot guarantee the distribution of water drop when it travels toward the compressor wheel. Some will pool on the flange wall and migrate/trickle towards the utmost tip of the turbo. This will exert most load on the turbo. Long term, it will unbalance and pit the compressor wheel, followed by excessive shaft wear.

I am not sure why you are using methanol instead of water. Water has more cooling capacity.

Until you have balanced the air against the meth flow fed to the nozzle, you cannot
guarantee how well the mixture is atomised. I suggest running run water for one test, clip the jet on the windshield and see how well the spray is atomised. (driving test)

If you have a air compressor handy, you can do it without driving the car. You can also measure exactly how much water/methanol is injected for 1 minute.

[rudypoochris]

Originally Posted by Richard L

Although water is heavy but compared to the mass of air going through the turbo, it is much less. There will not be to much variation on the BCV's PWM.

You cannot guarantee the distribution of water drop when it travels toward the compressor wheel. Some will pool on the flange wall and migrate/trickle towards the utmost tip of the turbo. This will exert most load on the turbo. Long term, it will unbalance and pit the compressor wheel, followed by excessive shaft wear.

I am not sure why you are using methanol instead of water. Water has more cooling capacity.

Until you have balanced the air against the meth flow fed to the nozzle, you cannot
guarantee how well the mixture is atomised. I suggest running run water for one test, clip the jet on the windshield and see how well the spray is atomised. (driving test)

If you have a air compressor handy, you can do it without driving the car. You can also measure exactly how much water/methanol is injected for 1 minute.

If PWM/work doesn't drop, what is the benefit of injecting pre-turbo? I thought the idea was to get more air through the turbo before going out of the efficiency range (increased efficiency). It seems if work in is the same and so is boost air out, that I haven't changed the efficiency at all. Or is it that the turbo is equally efficient, but can handle more flow before overspeed?

Are people actually documenting erosion? I haven't been able to find a solid source of it yet? It makes sense to me for large droplets or saturated walls, but it would seem the walls of the tubing in the engine bay are quite hot and the speed of the air high enough that pooling probably doesn't occur. I of course have no way of testing for this right now. I do know though that a lot of PCV is diverted through the turbo inlets and that does not erode the compressor despite being likely significantly larger unatomized drops.

Interesting. I might do the atomization test. I am not sure how knowing exact water/meth quantity will help. I do have the aquamist flow sensor feeding into the DME though and you can see it in the logs above. Half scale should be 600ml/min or so.

What do you mean by balancing the air against the meth flow? You mean the flow into the 2-port nozzles? The boost air will always be higher than the pressure of the fluid by a couple points. Say 17.5 psi boost with 15ps or so water/meth.

I am using a combination of water/meth since I speculated meth evaporates quicker (reducing chance of erosion) and because the meth helps out with the fueling a little bit. I could go full water or full meth if I needed I guess.

[Richard L]

Originally Posted by rudypoochris

What do you mean by balancing the air against the meth flow? You mean the flow into the 2-port nozzles? The boost air will always be higher than the pressure of the fluid by a couple points. Say 17.5 psi boost with 15ps or so water/meth.

I am using a combination of water/meth since I speculated meth evaporates quicker (reducing chance of erosion) and because the meth helps out with the fueling a little bit. I could go full water or full meth if I needed I guess.

It is quite tricky to set up an air assisted nozzle. You really need minimum amount of pressure on the fluid and ample air pressure. If you have too much fluid pressure, the atomisation is not that good.

Look at the following pictures, the difference is very visible.

[rudypoochris]

Originally Posted by Richard L

It is quite tricky to set up an air assisted nozzle. You really need minimum amount of pressure on the fluid and ample air pressure. If you have too much fluid pressure, the atomisation is not that good.

Look at the following pictures, the difference is very visible.

I can throw a pressure regulator onto it no problem - can you recommend a pressure? Currently flow is controlled using a simple valve with a screw on it. I can tighten that up as an alternative.