Nozzles and de rating

[sdminus]

Im trying to fiqure out how much a nozzle would de rate if the supply pressure was lowered. Is there a basic formula i can apply to it.

Scott

[JohnA]

It's much like fuel injectors, if the variance is kept within reason.
Lower it too much and then atomisation goes out of the window.

[sdminus]

I have a controller for my pump which varies the cycle from the pump. I was just looking for some figures to stick in my calculation

Scott

[Richard L]

Here is something to get to your started, M7 = 7 US gallon per hour.
4x pressure = 2x flow, 100x times pressure- = 10x times flow.



Richard

[simple]

Graph look good. If you have a standard pump (160PSI) than you can run minimum atomizing pressure of 40PSI to160PSI. This actually will give you flow range of double.
Say if you start injecting at 3000RPM @40PSI than you pump will only have produce about 160PSI(or less depending on your engine volumetric efficiency) at 7000RPM.
This makes PWM controller suitable.
Any comments anyone?

[Richard L]

Fuel requirement is based on RPM x LOAD.

A dymanic range of 2x will only over 3500-7000 RPM at the same boost pressure. Most WIA system injects between two fixed pressure settings. If you include that variation in the calcutation, you need a dymanic range of may be 3x? Let say 2.5x, making the dynamic pressure span of 40 psi to 250psi. Not many pumps can do that.

I could be wrong, but on paper, the pressure related system can only cover a small operating range.

[sdminus]

Not sure if i under stand what you mean by 2x dynamic range. If you can vary the pump from 40-100 psi could you not just base the ratio on this or are you saying that 40-100psi is too narrow a band for the range of fuel you will need.

As i type think i understand where you are coming from but i will need to work it out on paper. Another problem is staring me in the face now tho. After reviewing some datalogs its gonna be difficult to get the mix correct by using a 0-5 volt from the map sensor when the car makes boost fast.

Scott :roll:

[simple]

With dynamic range, we are talking about pressure range that pump can provide with PWM controller. 40- minimum for jet, 160 ? maximum pump can provide.
According to the flow graph this range of pressure will allow you to vary amount of delivered water only in the range of x2. Say 200cc at 40PSI to 400cc at 160PSI.
This range may or may not do, depending on your motor?s specifics and WI system tune.

Using 0-5VDC from MAF is not a bad set up but not perfect. As from what I understand water delivery curve is not liner. It must spike at maximum torque and follow the engine load.


I will try to do some calculations when I will manage to get volumetric efficiency table for my AUDI motor. Until then I am guessing.

Richard L, did I miss anything?

[simple]

I managed to get this graph together.
Specs:
AUDI 2003 A4 1.8TQM: Revo/GTRS Eliminator turbo (GT28RS), Eurocode FMIC, Neuspeed Extreme TIP, 3" custom turbo-back exhaust.
Top graph Blue line is air flow (grams per second) and pink line boost in PSI multiplied by x10 for better appearance.

We can see that boost stabilizes at 14PSI @3500RPM. This is where maximum torque range starts. So if w would have WI on this car we would want to start injection at about 3400RPM. At 3400RPM we flow 110grams of air. At this point WI will start injecting @ 40PSI rate. As RPM go up air flow increases. At about 6000RPM our pump with PWM controller will be producing 160PSI and getting maxed out (220g/s air and 160PSI water which would correspond to twice as much air ? twice as much water).

Conclusion: With the given pump range of 40-160PSI and given AUDI engine volumetric efficiency, we can properly control water delivery only till about 6000RPM after which we max out delivery pump. After 6000RPM water delivery will start to ?lean out?

I would appreciate some comments / criticism.

[sdminus]

COOL.

What you have done looks very similar to what im trying to do.
Im using FC datalogit to view data. I have also used the flow tables and a chart which give water - air ratio for good atomisation at set temps.

Im starting to see problems with my lack of pump pressure. Im either gonna suffer low down or at high end. Im trying to stick together a track side calculator to alow me to adjust the amount of water injected at certain temps with ease.

Scott