911 aircooled developments

[PeteKz]

Neil, DI does not allow more time to inject fuel. Actually the opposite because the fuel should be injected only between the end of the exhaust stroke and a little before the top of the compression stroke. Whereas, with port injection, you can inject continuously throughout the full 4 strokes. As you know, with CIS, fuel is injected continuously into the ports, even at low throttle. With EFI, the injectors open and close: at low throttle, they are closed more of the cycle than they are open, but at full throttle, they approach open 100% of the cycle, so it's like CIS at WOT.

Some manufacturers have recently employed both port injection and DI together to get the advantages of both systems, particularly for engines with variable turbo vanes and multiple turbos. That level of complexity scares the crap outta me.

[Neil Harvey]

Complexity does not scare me as its a opportunity to learn. It should never be
taken for granter though.

I'm looking at port injection as a start. It makes it a little more simple to build. I have no idea how it will work as I have found no other application of just high pressure port injection. I do lose the opportunity to inject into the chamber when the Inlet Valve is closed where as DI can continue.

My hope if this is successful is to raise the CR number and lower the knock level.

We have conducted some tests over the years and found that even with current EFI, the mixtures are not a very homogeneous mixture. Low pressure and the turn that the air has to make in these engines works against a good mix. This is why we see a lot of residue fuel droplets on the runner walls that become part of the fuel entering the chamber but not part of the programmed injected amounts. Common issue with most engines not just Porsche. However the Porsche "turn" is one of the worse.

If the higher pressure helps lower this effect, it should result is some level of performance gain. If I can raise the CR number this hopefully will allow these older engines to survive and make more power.

A lot to do still. The list grows every day. Starting to assemble the parts required and the more we accumulate the more we find we do not know.

[PeteKz]

I don't mean literally that complexity "scares" me, but it does cause me a lot of concern for more crap to go wrong, harder to figure out problems, and opportunities for Murphy to get involved. One of the reasons I drive an olde air-cooled 911 is that it is dirt simple, and I can fix anything on the car, or even make new parts if I have to. Not that I have to, because virtually every part is available from OE suppliers or aftermarket.

DI does offer the possibility of higher CR's. My wife's former 2009 Cayenne S had the DI V8 engine. It also had the alusil block cylinder failure. In troubleshooting why I was burning oil in two cylinders, I found that the compression test was so high that I had to use my diesel compression tester. The test numbers were in the range of 285psi! That works out to a static CR of almost 20:1. I later found out that the dynamic CR is much lower, and it's managed by changing the valve timing through the cam timing phaser.

Also for DI, the injector location, angles, combustion chamber/piston shapes have been developed through lots of R&D by Bosch and the vehicle manufacturers. If you decide to use DI, try to copy what has already been developed by the manufacturers. Plagiarize shamelessly!

[Neil Harvey]

The first application will be port injection with the Injector placed like the new ITB runner shows. I will see what challenges that gives me. One step at a time.

[PeteKz]

A wise approach.

[Neil Harvey]

Today spent some time with the new rotating parts for Project 24. Weighed the Crankshaft and we have saved more than I had calculated. I have a target weight for the Crankshaft, Rods, Pistons, Pins, Rings and Clips. This saving is really good and we are below our calculated target weight. With the rotating weight lower than calculated it is all about the heads now. There is only so much that can be done to these 2V heads. Most has already been done. Now its about finding the "Golden Ticket".

I'm running a way higher CR number and hope that with the DI injection this will allow.
We will find out. This whole project is about trying and learning something.

[PeteKz]

Neil, let me ask to be sure. How are you implementing DI on the Porsche air-cooled heads?

[Neil Harvey]

Everything about this project is about learning something new.

My intention is to start with port Injection to understand the characteristics of DI on these old engines.

A simple approach first. These injectors are large along with the hardware that supports them. If this is any way successful a more direct install of the Injector facing the back of the valve may be the next iteration.

The current idea is to try passive pre chamber technology using one of the Spark plug positions.

We are a long way from this but this is the plan.

[PeteKz]

I may not be understanding your use of terminology. DI or direct injection, means injecting fuel directly into the combustion chamber, like a diesel. Is that what you are working up to? If so, how will you install a DI injector into the combustion chamber?

[Henry Schmidt]

Originally Posted by PeteKz

I may not be understanding your use of terminology. DI or direct injection, means injecting fuel directly into the combustion chamber, like a diesel. Is that what you are working up to? If so, how will you install a DI injector into the combustion chamber?

The simplest way the use direct injection in a two valve 911 head might be to install a COP ignition in the bottom plug hole of a twin plug head and a sleeved adapter into the upper plug hole for the injector.
Ignition control and injection timing will become indefinitely critical to pull that off. Bosch makes a shorter MFI injector (Mercedes) with a 12mm thread vs 10mm on the 911 injector that might make fitment more straight forward. There might even be a diesel injector that would satisfy that challenge using Piezo technology.

[Neil Harvey]

I have a lot to learn. I have no idea how this will work so my intention is to get a handle on running an old engine with modern high pressure FI. Starting with port injection first. Once I understand the characteristics of this then we can think about passive chamber injection.

[jac1976]

Neil, I had to chuckle at “I have a lot to learn.” I appreciate the humility and adhere to a life of learning myself. If you “have a lot to learn,” I can’t machine the amount the rest of us have to learn.

[Neil Harvey]

Some years ago when we got back into building some air cooled engines compared to the water engines, I felt that life got easier. Where did I go wrong?

I was reminded of that saying, if it ain't broke".

[PeteKz]

One time, late at night, I tried to count up the number of joints, gaskets, etc. that oil can leak out of a 911 engine. I got up to about a hundred, then fell asleep. I still don't know the definitive answer.

Then I counted the number of places an American V8 can leak oil: About a dozen. If you count places where coolant can leak, less than a dozen. Two dozen is simpler than 100+.

But I still think of a 911 engine as simple...

[Henry Schmidt]

Originally Posted by Neil Harvey

I was reminded of that saying, if it ain't broke".

I've always thought of that statement with the question: At what level is less functional considered "broke" ?