Alternate fueling/adding port injection 2.0T

[davidsain]

I've searched high and low and haven't found any concrete info. Some hints is all. I'm thinking about a project for my near stock B7 A4. It'll see some upgrades soon, but want to start thinking about this specific thing if at all possible.

We all know the carbon build-up issue on the DI engines. Why not wash with fuel all the time?

Here's the thought. Purchase an IE intake manifold, weld-in bungs, fuel rail and small injectors. Drill and weld in the bungs. Weld on mounts for the fuel rail. Recoat the manifold.

Fill the fuel rail from the low pressure supply by installing a tee before the HPFP.

Drive it with a MegaSquirt, sensing off of the cam sensor.

My LPFP puts out about 70psi. That would be enough to spray fuel. With fuel being diverted before the HPFP, the ECU tuning for a rich condition would call for less fuel at the Direct Injectors, so the total supply needed from the LPFP shouldn't change.

I would guess that the injector would spray at a predetermined time before TDC and that would be based on RPM. Wouldn't have to spray a lot, but would like to think of it adding to the stock injectors to increase fuel in a curve to match flow of a larger injector. I would surmise the spray timing would have to follow a curve accounting for valve open time, air flow velocity and how far the atomized mist would travel before the valve closed. I think of it like putting S3 injectors in. The ECU doesn't know they are S3 injectors, it just sees how rich fuel is at the O2 sensor adjusts accordingly.

The Integrated Engineering intake would require a tune for the flap delete and the tune I want has a number of other requirements (HPFP upgrade, injectors, exhaust, intake). But that shouldn't be a problem.

But there are questions...
Would one need a return line and a regulator on the low pressure fuel injector side?
Would the ECU compensate sufficiently to increased fuel without a tune/with a tune?
MegaSquirt (some of them anyway) can live on the CAN bus (2.0B 29bit). But what format does Audi use, A or B in 2008? Would it be able to read the sensors directly from the bus? Would have to identify and decode the desired messages which might be very difficult.
I can look at the cam sensor with a scope without affecting operation, so if directly connected, would the MegaSquirt pull down the signal (if high resistance input, I would think not)?

Just started thinking about this, and know some questions will beget others.

If possible, there would be a lot one could do.

Input please. And don't hesitate to tell me I'm crazy for wanting this.

[turbo944s2]

Hmm you are going to spend a lot of money just to avoid some elbow grease. Water injection/Water meth will be a cheaper solution.

[a4lownslow]

Sounds like $$$ and a waste of time for limited benefit. Just take two hours to clean carbon every 50k.


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[aluthman]

You will need to divorce the DI side from the port injection side. The low pressure side of the DI system changes too much to be able to reliably tune the port injectors. This is easiest to do by using a dual pump surge tank with one pump for each. You need to switch to a return style fuel system.

[Charles.waite]

You will need to divorce the DI side from the port injection side. The low pressure side of the DI system changes too much to be able to reliably tune the port injectors. This is easiest to do by using a dual pump surge tank with one pump for each. You need to switch to a return style fuel system.

If he’s adding tiny amounts just for valve wash, he could probably just pipe off the main HPFP inlet and run a single injector before the throttle body, you don’t really need precise fuel pressures and a dedicated pump in that case

The question then becomes, can you spray a small enough amount of fuel to provide a valve washing effect but not appreciably alter AFR and mess with fuel trims too badly? I would think yes, but I don’t know much about all that so I can’t answer that.

[Redryuu]

I would still go with a meth kit instead, run stronger than 50/50