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Old 05-16-2009, 02:06 PM   #1
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Default Hybrid EBC/MBC/WI/two-stage boost system on-line

This week I completed my hybrid electronic boost control (EBC)/manual boost control (MBC)/water injection (WI) so I'm posting this up for those who are interested in how it works.

First of all, here is the operational concept:
1. The EBC is the primary boost controller. It is being controlled open-loop (for now) by the Adaptronic via ground-switched pulse width modulation (PWM). The open-loop control in the Adaptronic works the same way, and is tuned the same way, as the Megasquirt; there is an RPM based table that regulates the valve duty cycle.
2. When the WI is turned on, and activated by the boost switch, a switch on the high pressure side of the WI pump is closed. One side of the switch is grounded to the chassis. The other side is tapped into the ground trigger wire for the EBC. So, when the switch closes, the EBC goes to 100% DC (closed).
3. There is an MBC plumbed in parallel with the EBC. This does two things. One, the boost can never exceed the MBC boost set point no matter what the EBC is doing. Two, when the EBC goes to 100% DC (see #2 above) the MBC is in control of boost. Thus, when the WI is on, and the nozzle is pressurized, the MBC takes over. This allows for fail-safe two-stage boost control.
4. There is a WI arming switch in the cab. When this switch is off, EBC is in control, and everything works normally. When the switch is on, the WI system is armed, and when it is triggered by the boost switch, will spray water into the system AND run boost off of the MBC. In my case, I have the MBC set to a higher level of boost than the EBC.

Here is a thread with more discussion on the whole hybrid EBC/MBC idea.

So, on to the pictures:

Here is the diagram of how I wired it all up. I do not want to redo this in visio today so you will just have to live with my sketch for now. There is one minor deviation; the pressure switch that grounds the EBC is between the WI pump outlet and the check valve, not between the check valve and the nozzle as drawn. It was a cleaner install this way, and still works.



Here is an image of the vacuum tap (boost signal) for the wastegate


Here is the WI check valve and nozzle


Here is the WI pump assembly


Here is the water supply tap and the float switch at the windshield washer fluid bottle


And finally, here is the EBC/MBC assembly


If you want to see larger versions of the images, here is a link to the Picasa folder
Picasa Web Albums - John - EBC-MBC-WI
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Old 05-16-2009, 02:10 PM   #2
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GJ man if i ever got my ebc to work properly, i would so do that.
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Old 05-16-2009, 02:17 PM   #3
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Thanks.

I meant to mention there are other ways of using this setup. For example you could do a Joe Perez style fail safe. That is, the signal from the pressure switch at the pump could be used to trigger a more aggressive timing map. This can work with the MS, and with the Adaptronic.

Also, though this is a fail-safe setup, it is not a completely fool-proof fail-safe (no such thing really). That is, if the injector nozzle is clogged, the system will still 'think' there is flow and trigger the higher boost level. This could be corrected with a flow switch in series with the pressure switch. In fact I might add a flow switch later. That way, if there is a clog, it will not activate. If there is a large leak, like a failed water fitting, it will not activate.
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Old 05-18-2009, 11:15 AM   #4
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So if I understand this correctly, the intention is to allow higher boost once water pressure is verified, right? Looks like it would work.

BTW, I notices there's no solenoid depicted in your waterline. How do you know water won't flow due to gravity/siphon, etc...?
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Old 05-18-2009, 11:27 AM   #5
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Yep it most definitely works. I was playing with it this weekend
The check valve prevents vacuum from pulling water into the manifold.
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