PorschePhD

I have had some say they were getting at leas that with other mods, although I will not guarantee that. The idea here is to raise the bar and add some safety to the system. Your 7th injectors, enrichment systems can not add more flow. They only drop the control pressure. Max flow is, well max-ed. By modifying the fuel head the system is able to add more fuel. Your piggy back systems will not help up top where it becomes an issue.

Sameer

Stephen,
What happens when the FEC drops the control pressure? I do feel that the FEC although not as good as the fuel head mod but still does enrich the fueling. What good isit if it does'nt add anymore fuel than stock? Surely theres something to it. Pls read below:

I got this off the Andial website where they mention that the fuel is enrichened:

"It will automatically enrich fuel system from boost pressure of 0.8 Bar on and higher. Actual fuel quantity is adjustable manually by means of potentiometer.
The Andial Enrichment System prevents this by simulating a cold engine condition, through manipulating the warm-up regulator, when additional fuel is needed. This is accomplished using a pressure switch that is set to activate at approximately 0.6 bar of boost pressure. A small control box initiates the process and the fuel control pressure is altered through a Bosch frequency valve, which is supplied. The kit also includes a potentiometer switch that lets you manually adjust the amount of enrichment required for that particular engine. The switch will increase the duty-cycle of the frequency valve in increments of 10%, with the first position being the "off" or inactive position. Once the optimum setting is determined no further adjustment is necessary. "

PT

Sameer, if your system is already max-ing out the flow capacity of the fuel head, with or without Andial system, then dropping the control pressure will not give you more fuel.

I have the Andial system and I have a European fuel head that came with the car. Based upon what the LM1 tells me, I can even turn off my Andial & still run rich (~12.1 AFR at full boost on track). So you really need to know the AFR before adding fuel enrichment (ok - silly me to start) or doing the fuel mod IMHO.

JoeMag

PT- what's your full boost (at red line) and you're getting 12.1 all the way to red line?

Sameer

Ok thanks guys

m42racer

Would some one who knows answer a nagging question I have had for sometime.
The CIS system has a plunger with slots in it. The arm is pushed down with inlet air which pushes against the "control" pressure. Is this correct? By adjusting the control pressure the plunger can go further and open up more of the slots and feed in more fuel. The WUR with the bi metalic can adjust the control pressure. If you run too high a system pressure the overall fueling is off. At idle it would be to rich?
This is a very simple version I know. Is this some what correct. So my question is this. If the system pressure is set by shimming the relief valve, and the control pressure is regulated by the WUR, and the volume of fuel is based upon the opening exposed on the plunger, do bigger Injector Lines make any difference?

Seems to me the the best way would be to use a additional Injector system and take the extra fuel for those Injectors before the main CIS fuel Head. The pump will always pump against the system pressure. Adjusting the frequency Valve should work if the overall max volume is accepted as what the Fuel head can deliver. This is my question regarding the Lines. If there is more fuel in reserve in the larger lines, will this make any difference? Is there ant restriction in the Lines, banjo's etc at the Fuel head. Seems it would be quite simple to open up the fuel head. The slots could be opened up and the ports could be also. I'm not sure what is done, but it cannot be rocket science. So if you open up the fuel head, is the restriction then in the Lines and banjo's. Has anyone flowed these things to see where the restriction is? If the pressure is fixed, then only the volume can be changed. If you supply more volume thro the system, and then could adjust the control pressure, then you would have a pretty good system.

jhunt@huntinter

good question. The factory used larger fuel lines on the earlier ('79 and earlier) and euro models.

PorschePhD

Simon,

You are correct in understanding that how the plunger reacts. However what has been a misconception is that by allowing the plunger to have less pressure (lower CP) the pin will drop farther. Yes and no. It does drop farther at any given position naturally causing the system to add more fuel at that particular spot of the pin. The part that needs to be clarified is that the pin when at full travel by the stoppers of the box is max open. Looking at the slit in the bore will show that the system cannot really open any more. So regardless of control pressure at that time the system will not add more fuel up top. In order to achieve this the flow needs to be increased. You can do this with pressure to a degree. Much like moving to a 5 bar on a system running a 3 bar. While that helps some it often causes issues with the ability of the WUR to control cold and hot. The WUR also has a boost circuit in it that will cause the WUR to drop pressure to the head while under boost. It can be manipulated to a point as well, but the end issue of flow up top remains. This is what we do by remaining the head to a larger port size and matching the pin. Also the lower half is modified to reopen the differential ports to the upper and lower chamber.

You could use a AIC and a separate set of injectors, or even plum another set of injectors as you mention and control it with a WUR and lambda, however the cost of the additional WUR and separate components often don’t make sense. The cost of the WUR has jumped over the last few years as well as injectors.

The lines are restrictive above 500HP Crank. Considering each setup is a tad different this number will vary. It is a good point to start from though. The testing originally done I found that on the systems we build producing between 450-475 HP the system made no change in AFR by switching lines and or injectors to previous version. The commonly known euro version. It was believed that in or around 81-82 the use of the Euro head was no longer needed and the lines became the restriction. The continued using the Euro lines and injectors on the smaller US (silver) head until realized that there was no benefit there. This is why you see some Euro cars with US heads and euro lines. Some without the lambda pressure port. The banjo fittings also have remained the same through the years. The port size is exactly what it was in the earlier cars as it remained through 94. Also you will find two versions of the euro head. One that can be port adjusted externally and one that is internally shimmed per port. Both are cast.

In the end your question can be answered with the lines ultimately become the restriction. But not before most bail out and move to EFI for a multitude of reasons. The most being the ability to control fuel curve. The CIS dump is only controllable by changing the WUR pressure at a given map based on RPM/KPA. The finical investment in time and money often is a valid reason to simply move to EFI.

m42racer

Stephen,

Thank you. I mis spoke. The slits sre in the Plunger housing on the Plunger itself, right?

So from what you are saying its volume not pressure that will make the difference. Does this mean that any change in volume has to be carefully calculated, otherwise the whole fuel curce can get out of whack. I suppose it could.

From your last sentence I get that if you could increase the flow at some known rate, and then could adjust the System pressure via a Frequency Valve, based upon RPM verses MAP, this would then allow any increase in volume to be metered as required.

The product out there now I understand just give a set Frequency rate, so the A/F is good is one place but either too rich or too lean in another part.

PorschePhD

In the center of the fuel head is a bore called a metering cylinder. This has 6 metering ports ( rectangular slots) that run from this cylinder (bore) These are in turn controlled by the plunger (control pin) which is moved by the air plate. The plunger is shaped to open and close those ports based on the piston of the control plunger. So it is shaped with a bigger end and smaller center to allow fuel to pass from the inlet port to the metering slots.

Correct. Those ports are the issue. Not the amount of movement of the pin as once thought.

You would actually adjust the control pressure, not the system pressure. The system has to maintain an overall pressure. So the system pressure comes from the pumps and is maintained by an internal valve in the head that returns fuel to the tank when that pressure is achieved. The control pressure controls the pressure on the lower half of the fuel head and will raise or lower the pressure on the lower chamber to create more ort less resistance on the diaphragm which in turns allows the plate to move harder or easier. The control pressure needs the system pressure to be at its range in order to function properly. They are two separate things.

You could control the control pressure to fluctuate the plate at a give RPM/Kpa in order to achieve a specific AFR in that cell. This would increase the volume in this range as long as the port was not WOT and all the way open. At that point it makes no difference. The port is full bore to the feed in the head. The control pin is allowing max flow.

It bypasses the lambda control line and feeds its own feed from the return line to the control line thus simulating a lean condition and allowing the add on frequency valve to control pressure and drop the pressure off the lower chamber thus enriching in that range. Typically .4 bar on.

Yes, CIS dump as we call it can be somewhat tuned out with an AIC controlling that frequency valve to hold more pressure on boost surge then even out and drop across the range until flow is maxed. Any mappable system could be tuned if it will control a frequency valve which is more or less an inline fuel injector.

Correct. In fact it is a very fine line between running and not. Go to far and the system wants a very high CO to idle. To low and you will have a net zero result.

Hope this helps.

m42racer

Stephen,

We are talking about the same pressures, I'm mistakenly calling them by the wrong name.

Ok, so if the slots are the restriction, then I suppose they could be opened by EDM process to make them larger. This would allow more fuel to flow thro the system, but as you say, go too much and you have a very rich system. I suppose the fuel flow is measurable thro the Fuel Head and any change in slot size could be calculated before changing. Then use a system that can control the "control" pressure based upon Engine Speed verses MAP and you have a very "mappable" mechanical fuel system. Seems the combination of some electronics and some mechanical mods could net a very good system that would allow those who do not wish to go to the expense of EFI to have their cake and eat it too.

I understand what you mean about the max flow. Any additional change will make no difference. What I was thinking was

Sameer

Stephen,
Thanks for the info. I really do learn a lot from your replies.

PorschePhD

Yes, however the caveat here is that will not completely allow for a well running system. Each port then needs to be adjusted and flowed accordingly.

Your theories are correct. The interesting thing is the CIS did not die with Porsche. If you look at Volvo and Audi’s late systems they used a combination of what you are asking. The fuel plate was no longer attached to the fuel head. It was still present, but was attached to an interpreter that would sense the position of the plate and send a signal to the head which would inject fuel like any CIS system. CIS-KE was used in the early 90s with Audi. It was a completely mappable system and used an ECM to control the amount of pressures and flow based on the “electro hydraulic actuator” (pressure actuator) on the side of the metering plate. The system would more or less split the pressure from the system pressure to create a flow from the differential ports to control flow. The biggest difference between this and say a frequency valve is the FV is a series of pulses where the KE system uses a steady state of current to control pressure since the arm is no longer controlling the metering pin. Transition therefore remains smooth and seamless.

Sameer

Did'nt the turbo 3.6 use the KE Jetronic system?

PorschePhD

No, it had a different enrichment system, but the injection still used a WUR and control pin in the head.