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Interesting thought!

Thinking out loud, I wonder if changes in system pressure can effect fuel delivery enough to give us the control we need.

If so this would be a simple plumbing job.

There are a couple of other ways we might approach this.

Another thought might be to put a spring under the control plunger pushing toward full open and use a frequency valve plumbed in place of the WUR to move the control plunger's position. At a low duty cycle pressure would build pressure above the control plunger and push it down, high duty cycle would let it rise.

Or as you noted before to use an injector to meter fuel instead of the control plungers position against the metering slits. This would probably be the most controllable and accurate.

Then the question is how do we get the injectors fuel to the upper chamber?

Or, how about a custom distribution block that replaces the Fuel Distributor totally and holds the injector.

Not sure about this as part of what the FD dose is equalize fuel delivery to each cylinder. Basically every injector supply has its own regulator built in that I think is self compensating for changes in fuel or system pressure. (why I am not sure controlling system pressure will work.)

Now, depending on the approach, will we still be living withing the same gross fuel deliver potential. That is if a stock FD and modified WUR can support say 450chp, will that be our limit and is that ok?
Old 09-16-2010, 01:06 PM
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ps, I have been trading email as to if the injector you noted will work at near 100psi sustained.
Old 09-16-2010, 01:07 PM
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Quote:
Originally Posted by 911st View Post
We can do this by engineering how the Metering plate and cone works.

The plate and cone design along with CP's determined by the WUR are the "chip" or MFI "space cam" of the CIS system. Change them and you reprogram the fuel deliver curves and quantity up to the fuel quantity limit of the head.

So how can we do this.

One way is to re-configure the cone by extending it or changing the angles. This would be a major effort.

Another way I learned of from the CIS expert I retained is to add a wedge or volume to add windage to the top of the MP. This keeps the profile of the MP higher up in the cone so the air pressure can push it down further for more gross fuel flow.

This is a picture of how it might look.


This would be a very easy way to do this. Would it not be cool if all you had to for more fuel to support your new big turbo is to replace the metering plate?

There is /was such!
Hello,
I seem to remember on my 300CE Benz, that the additional plate picture provided by another person(silver disc) was actually at the BOTTOM of the flat plate, which I found odd, but then it made sense as to smooth out the flow, instead of creating more vortices's/turbulence.

Aerodynamics is a very tricky, black art...glad someone else is thinking of this as well...would like to hear or see some results.

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Old 09-16-2010, 03:23 PM
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911st, I think we are very much in synch, although I never thought of the spring under the plunger option and replace the WUR with an injector to manipulate the control pressure, I think the theory on this one is very clear and doable. We just have to make sure the plunger does not stay open when the car is shutdown. But this can be achieved pretty easily letting the pump run for a few seconds after shutdown to build up pressure that will overcome the spring. I have a 911 Carrera 3.0 I can use as the guinea pig before plunging into the turbo 3.6.

On the other hand, I need more details on the inner workings of the FD. I am craving CIS K-Jetronic info and have been reading all over the internet. I am gonna try and get a CIS system from a Junkyard for experimenting.

Back to your spring under the plunger idea, this does achieve getting rid of the metering plate and have a single point of control, the big fuel injector which combined with an ECU and the other signals (TPS, MAP, etc) should do the trick.

Update: http://www.porsche928forums.com/download/manuals/CISRebuild.pdf, all credit to it's author Richard Andrade. This certainly confirms your concerns on controlling fuel with simple plumbing and pressure, the FD is a little monster. I have yet to understand the function of the diaphragm and springs for every injection port. I will figure it out, unless someone already knows the answer and chimes in before I do :-).
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Last edited by IMONBOOST; 09-16-2010 at 07:55 PM..
Old 09-16-2010, 07:28 PM
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I suspect one of the things the FD dose is compensate for the fuel pump should it go out of spec and even system pressure if it goes out of spec. That is the AFR's will be maintained to the best of its abilities. It is the upper lower chamber differential that determins how much fuel is delivered not system pressure.

I think raising and lowering system pressure might only effect things at the highest delivery rates. That is, if system pressure is down to 80psi, it might have solid AFR's until say 300hp and then go lean. But if you move SP to say 100psi it might deliver fuel just fine up to 400hp or such. (Not to be comfused with the metering plate stall at higher air flow.)


The spring idea could be with removing the metering plate and installing a spring on the lever, or removing the lever to and putting it right under the control plunger. This would push the control plunger it toward WOT delivery.

I to wondered about shut down. However on EFI when the injectors close, fuel pressure is maintained in the fuel rail so the residual pressure should ( I hope) keep the CP in the idle position.

The check valves at the injectors will retain pressure there. On top of that there is a dampener that helps keep the CIS ready.

I am just not sure how accurately we can move the CP up and down. Can we maintain a 14/1 AFR at idle. Move it for accell fuel and hold it at cruse without something without a feed back loop or reference system that knows the position of the CP at all times.

Changes in control pressure against the metering arm seems to be accurate enough to maintain constant AFR's w/o a feed back or reference circuit.

This also would not require much of a frequency valve or injector. We might just use a normal Lambda Frequency Valve or source an Andial FV. It could also operate at about the same pressures as the WUR or higher if we need more fedility or response time.

Also, a Lambda style CIS might work will as it will fine tune the AFR's at idle and cruse. The EFI might even take control of this for fine tuning and or accelation fueling.

I am out of town until Monday on a golf holiday. When I get back I have the 91 Turbo technical guide with pictures and description of the CIS I might be able to share.

Will give this all some more though.
Old 09-17-2010, 10:55 AM
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Regarding the possible choices of FV, I'm interested in trying this - but how best to adapt an injector designed with a fuel rail top fitting and a manifold port below to a hose connector both ends instead?

What kind of pressures would this FV be seeing? If I'm understanding this correctly, I realise that the return bleed on the bottom isn't as high pressure as the supply/inlet side - but is that inlet getting CIS system pressure?

There's some older FI injectors with hose barbs on the top - but they aren't designed for 6.0 bar. And almost all the high-capacity injectors are of a more modern design.
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Old 09-17-2010, 01:16 PM
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The inlet is seeing System Pressure. Just before the fuel return on the FD there is basically a fuel pressure reg built in. Every thing between the fuel pump and there should be at system pressure or SP less the upper lower differential. The exception being the control pressure exit port on the top of the FD. I believe.

If you use a standard style injector probably have to make a manifold for it and it might hold the injector kind of like a D cell battery.

There are several Frequency Valves including the one Porsche used on the Lambda style FD's that have hose fittings on them. See post #73 on page 4 of this thread of a FV that I sourced from Andial for my programmable fueler.

As to what pressure it would see it depends on if it is on the system pressure side or for moving the control plunger up and down. And with that it depends on the spring tension we use.
Old 09-17-2010, 09:13 PM
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OK, the vendor for that large EFI injector emailed me it would function at a steady 100psi if needed.
Old 09-20-2010, 03:49 PM
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Quote:
Originally Posted by 911st View Post
OK, the vendor for that large EFI injector emailed me it would function at a steady 100psi if needed.
Cool!

I found a fitting which seems to go at least part of the way towards adapting a stock injector to provide hose end fittings http://www.electromotive-inc.com/efi_parts.html (Fuel Injector Boss, Cap and Assembly, at the bottom of the page).
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Old 09-21-2010, 09:28 AM
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Might be able to use the supply side fitting on the injection side instead of using the manifold bung as the O rings seem the same size.

Old 09-21-2010, 07:14 PM
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Then the question is how are we going to get fuel in to the upper chamber via the injector?

One path is through the metering slots?

One way would be to come in from the top of the Fuel Distributor. However this would probably require modifying the F D with a larger hole in from where the Control pressure fitting goes. And modifying the control plunger so fuel could get down from the top

Another way would be to come in from the bottom of the FD via a replacement for the Control Plunger that blocks the lower chamber supply source and leaves an open path to the upper metering slots. This might be more of a bolt on and not require taking the FD apart. It would require a fitting to enter the metering housing. Could bring it in the arm pivot.

I am thinking we cold make a fitting that replaces the control pin, and has O rings on it to seal off the lower chamber supply and deliver fuel to the upper chamber.

What would really be cool is if we could hide/house the injector inside the metering housing.


Last edited by 911st; 09-21-2010 at 07:27 PM..
Old 09-21-2010, 07:24 PM
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I got it, we remove the control plunger, use the lower chamber's system pressure to supply down the control plungers hole, to the injector, put the injector in the bottom of the metering housing, and feed the upper chamber up the center of the fitting we replaced the control plunger with.

Simple, no external supply fittings or clues except a couple of wires going in side of the back of the metering housing.

To cool!!!
Old 09-21-2010, 07:35 PM
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So you are saying, connect the bottom of the FD with plunger removed to the input of the injector and the output of the injector to the top of the FD? Could you explain a little deeper I think I may not be getting it right. The control pressure is controlled by the FD integrated pressure regulator? Without the plunger, there would be no upper and lower pressure and the pressure would be equalized. Is this then exploring the path of controlling the overall pressure of the system rather than pressure differential? Sorry I was away...was on a trip..I am very interested in a solution like this.
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Old 09-21-2010, 09:20 PM
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I still think there is some merit in removing the whole air flap and arm, then controlling the plunger directly with a stepper motor, actuator, servo, or some device that will give direct control over the plunger. It could be hidden in the housing. Then you could remove the WUR, start injector and various other components.
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Old 09-22-2010, 06:08 AM
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The way the FD works is Supply Pressure enters at the bottom of the control plunger area, goes up its side and as the metering slits are uncovered flows into the upper chamber.

We would have to remove the control plunger and replace is with a manifold that slips up into the FD. It would have two sections sealed off with O rings. One would seal above and below the supply ports. The other section would be to the area above the supply ports to the metering slits/ports.

Fuel would come down the manifold to supply the injector. Then be returned up the center of the manifold to the metering slit port area.

Said manifold would have to be sealed off above the metering ports to cap off the control pressure circuit that is tied in to the bottom chamber.

Thus, the manifold that would occupy the space of the Control Plunger would have three O ring seals. Bottom, mid, top with two passages. One to the bottom half to acces SP and one to the upper half to feed the upper chamber.

It might be easyer to just make a simple manfold that just blocks the lower ports and get fuel off the supply conection.
Old 09-22-2010, 08:05 AM
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Stepper Motor.

Yes, this is workable and it could be concealed inside the metering housing. We just need to replace the control plunger valveing with some other type of valving.

Both approaches would probably remove the metering plate, arm and the WUR. If one wanted they could just leave the WUR in place even if it is not functional.

It just seems that it is easyer to adapt almost any EFI driver to run an Injector / Frequency Valve based system.

Which ever is used we do have less air flow restriction and better tailoring and adapting of fuel and ignition to varying operating conditions. We would get much of the benefits of an EFI conversion except maybe expanded gross fueling without all the heavy plumbing modification and a bit less electrical work.
Old 09-22-2010, 08:17 AM
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Ok, I am inclined to work on the servo motor, I think it will provide more control than the frequency valve. I think the frequency valve will be a lot more challenging to get it to work within acceptable margin of error in an open loop mode. Obviously, this is just speculation, I have not done any scientific process to prove this. Just that the stepper motor will not violate the original CIS design in terms of how the pressure differential is controlled (plunger). I have started doing research with the designs used for fly by wire throttle body control. There is readily available documentation of people using PIC microcontrollers for a to d conversion and using a PWM signal which is probably the logical signal to use from the EFI ECU.
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Old 09-22-2010, 07:44 PM
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The stepper motor system could work very well.

To me the challenge is on the software side and finding a suitable driver. There are systems that will drive a steeper motor but I suspect not for the application planed. I could be wrong on this but looking into this might be a good next steep.

With a Frequency Valve we can probably use a normal EFI system. w/o modification.
Old 09-23-2010, 11:40 AM
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Quote:
Originally Posted by 911st View Post
Stepper Motor.

Yes, this is workable and it could be concealed inside the metering housing. We just need to replace the control plunger valveing with some other type of valving.

Both approaches would probably remove the metering plate, arm and the WUR. If one wanted they could just leave the WUR in place even if it is not functional.
Pull the WUR and block off the CP to the fuel head so the plunger has the most freedom (least resistance) to move. Remove the arm and plate, then drill and tap the bottom of the plunger for connection to the stepper. Then build a mount for the stepper. That would be the cheapest approach.

Now all you need is the stepper motor and the control electronics. Something open source like MegaSquirt could be adapted with a change in the source code. And it already has the basic input devices covered like MAP, IAT, RPM. We need an EE to step in!

I've had this rolling through my head for years, just never did anything with it, and don't have the EE skills to dig deep into the MegaSquirt.
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Old 09-23-2010, 11:45 AM
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Quote:
Originally Posted by IMONBOOST View Post
Just that the stepper motor will not violate the original CIS design in terms of how the pressure differential is controlled (plunger).
My thoughts exactly, keep it as original as possible, but change the control elements slightly.

Quote:
Originally Posted by IMONBOOST View Post
I have started doing research with the designs used for fly by wire throttle body control. There is readily available documentation of people using PIC microcontrollers for a to d conversion and using a PWM signal which is probably the logical signal to use from the EFI ECU.
That was my next thought, to keep things simple, just build an outboard stepper motor driver that accepts the PWM signal from the ECU. If all works well, then implement the stepper motor driver internal to the ECU.

FWIW I built a MegaSquirt I and play with it using the STIM and my o-scope. Haven't done anything else with it. I might be tempted to donate it to the cause.

Here's a good source for all things MegaSquirt:

DIYAutoTune.com Megasquirt Kits / Assembled Engine Management Systems, Wideband o2 Sensor Systems and tuning products
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Old 09-23-2010, 12:16 PM
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