Advanced CIS Turbo Tuning Discussion Thread. Ultimate?

[911st]

Control pressure flows from the lower chamber to the area above the Control Plunger.

If you block off the CP line you will probably hydro lock the Plunger and not be able to advance it quickly.

You could leave the WR in place and it would act as a hydro spring. Then make your own arm to work against the plunger via the steeper motor. No need to mod the plunger.

[WinRice]

Originally Posted by 911st

Control pressure flows from the lower chamber to the area above the Control Plunger.

If you block off the CP line you will probably hydro lock the Plunger and not be able to advance it quickly.

You could leave the WR in place and it would act as a hydro spring. Then make your own arm to work against the plunger via the steeper motor. No need to mod the plunger.

Very true! "Blockoff' wasn't a good choice of words, more like reduce the CP as low as possible so the stepper wasn't working against the pressure.

The only reason I would pull the WUR is to make sure I have nothing else in the system that would control the plunger, except the stepper. So maybe the WUR gets replaces with a fixed pressure regulator so it's always constant?

Using the arm would be slick, because you could vary the arm to pivot length to fit whatever the stepper throw you have.

[911st]

I would not wast my effort. Just unplug the manifold boost line to the WUR and keep it in place as your pressure reg.

Look at the surface area of the top of the plunger to the hot control pressure and calculate the pressure on the top.

If you feel you need to counter this to some degree, add a spring to the arm acting on the bottom of the plunger.

If you want more purchase on the plunger you could mount the steper motor so it acts on the original metering arm.


You might be able to take RPM and duty cycle from the EFI controller and write some type of program to translate that to the position you need the steeper motor at.

Example, 800rpm at 5% duty cycle is idle might be 5% steeper position, 80% duty cycle at 6000rpm (peak HP) is near full control plunger position.


Gross fueling might actually be extended to some degree. I belive the metering plate stalls and dose not advance the control pin to its furthest position. However, the Fuel Distributor will be subject to the same gross fueling limitations. (Which we know how to extend if needed.)

[IMONBOOST]

Hey, worry not, I can be the EE you are looking for, actually computer engineer, I can take care of the servo motor and MS no problem, worst case scenario, if I get stuck at some point since currently I am doing management work rather than programming, I work at a software shop, including devices so resources are more than available. I need to source parts for a prototype and probably use my Carrera 3.0 as the guinea pig. Time is my worst enemy, but I will find it for a project like this.

[WinRice]

Originally Posted by 911st

I would not wast my effort. Just unplug the manifold boost line to the WUR and keep it in place as your pressure reg

Remember, the WUR has a bimetallic spring that changes the CP with ambient temperature. I would want the electronics to fully control the mixture without any other variables thrown in the mix.

[WinRice]

Originally Posted by IMONBOOST

Hey, worry not, I can be the EE you are looking for, actually computer engineer, I can take care of the servo motor and MS no problem, worst case scenario, if I get stuck at some point since currently I am doing management work rather than programming, I work at a software shop, including devices so resources are more than available. I need to source parts for a prototype and probably use my Carrera 3.0 as the guinea pig. Time is my worst enemy, but I will find it for a project like this.

That's the spirit!

At one point, just as an experiment, I thought of using a high-end brushless RC servo to control the arm. RC servos use a PWM control signal over a narrow band, that could probably be driven with a modified ECU. I don't know if I would trust it over the long haul.

[911st]

Originally Posted by WinRice

Remember, the WUR has a bimetallic spring that changes the CP with ambient temperature. I would want the electronics to fully control the mixture without any other variables thrown in the mix.

How about also disconnecting the 12v to the WUR at the same time you disable the boost line. Then it will just act as a simple pressure reg at something close to cold control pressure. It will also maintain residual pressure in the FD as needed for the next start up.

Again, we are just using it as a spring and CP level or calibration should not be an issue.

Depending on the stepper motor and the amount of purchase/leverage you design into its connection, you may or may not even need any spring on the bottom side.

By leaving as much OE stuff in place like not modding the Plunger or removing the WUR, it makes the conversion just a bit simpler and keeps it easer should one want to go back to stock.

[WinRice]

Originally Posted by 911st

How about also disconnecting the 12v to the WUR at the same time you disable the boost line. Then it will just act as a simple pressure reg at something close to cold control pressure. It will also maintain residual pressure in the FD as needed for the next start up.

Again, we are just using it as a spring and CP level or calibration should not be an issue.

The bimetal spring is effected by ambient air temp around the engine and the 12V coil. The coil just accelerates the bimetal spring from cold state to warm state, so it doesn't stay in the rich position as long. If you remove the 12V wire the bimetal spring will still cool to the rich (or start) position when the engine is off, then warm up with engine temp until it slowly gets to the normal (or warm) position.

Now, all this doesn't matter to the plunger if we are controlling it mechanically, because we control it over it's total travel. It does change the CP in the lower chamber, which is also how the OEM lambda system fine tunes the AFR in closed loop, and will effect the final mixture. So we need a constant CP to eliminate any variables to deal with when using electronic control.

My thought was to use a simple needle and seat, basically a fixed orifice, in place of the WUR. Just dial the needle to a set CP and leave it there. It could also be used to fine tune the system, since it does control chamber pressure.

I guess you could remove the 12V and the bimetal spring and call it good, then the WUR would just be a regulator.

[IMONBOOST]

I have one of the first revisions of MS, I will rescue it and see if it still works after 4 years or so stored away. This should be good for prototyping...for the final version I would purchase a recent revision of MS board. I think I will get a CIS setup from a water cooled VW for the prototyping seen a couple very cheap. Then move to test on the Carrera 3.0 and then the final tests on the turbo 3.6.

[911st]

Originally Posted by WinRice

... It does change the CP in the lower chamber, which is also how the OEM lambda system fine tunes the AFR in closed loop...
, and will effect the final mixture. So we need a constant CP to eliminate any variables to deal with when using electronic control...

Good to be going over this.

What is the range of cold to warm CP?

Control pressure only effects AFR's by working against the metering plate's force.

Blocking the WUR exit would not effect system pressure or AFR's if the control plunger is being moved by a steeper motor.

The pressure above the plunger would however increase to equal system pressure and system pressure it's self will not be effected in any manner.

The fuel that was going to be passed through the WUR would just pass out the FD's system pressure regulator and go back to the fuel tank.

Blocking the Lambda Frequency Valve however would effect AFR's as it would reduce the pressure differential. Doing this will not effect System Pressure ether. Just lower chamber / differential pressure.

Thus, there is no reason to maintain any special level of Control Pressure unless it is going to be used as a spring / force to keep the control plunger from advancing unnecessarily and or it is to high, as if blocked, it might take somthing like 25 lbs of force to push the control pin up against it. (Anyone know the surfice area of the control plunger.)

A simple over the counter pressure reg (as suggested) in the place of the WUR that is calabrated would work just as well and alow such a system to be offered in a standardized kit form. Or just leave the WUR in place and work with it.

Again, good stuff.

[WinRice]

Originally Posted by IMONBOOST

I have one of the first revisions of MS, I will rescue it and see if it still works after 4 years or so stored away. This should be good for prototyping...for the final version I would purchase a recent revision of MS board. I think I will get a CIS setup from a water cooled VW for the prototyping seen a couple very cheap. Then move to test on the Carrera 3.0 and then the final tests on the turbo 3.6.

Yep, the original MSI should be fine for a working prototype, and cheap to play with.

Looking forward to your experiments!

I need to quit messing around with my suspension and get my car back on the road.

[WinRice]

Originally Posted by 911st

The pressure above the plunger would however increase to equal system pressure and system pressure it's self will not be effected in any manner.

The fuel that was going to be passed through the WUR would just pass out the FD's system pressure regulator and go back to the fuel tank.

Blocking the Lambda Frequency Valve however would effect AFR's as it would reduce the pressure differential. Doing this will not effect System Pressure ether. Just lower chamber / differential pressure.

Thus, there is no reason to maintain any special level of Control Pressure unless it is going to be used as a spring / force to keep the control plunger from advancing unnecessarily and or it is to high, as if blocked, it might take somthing like 25 lbs of force to push the control pin up against it. (Anyone know the surfice area of the control plunger.)

A simple over the counter pressure reg (as suggested) in the place of the WUR that is calabrated would work just as well and alow such a system to be offered in a standardized kit form. Or just leave the WUR in place and work with it.

Again, good stuff.

I pretty much agree, I was going off you first comment that blocking off the WUR would effect the lower chamber pressure, and from my highly tuned memory () of the system. Now I'm looking at the Bosch manual.

The lower chamber sees the regulated system pressure, then the upper part of the plunger sees pressure from the 'decoupling restriction' which then leads to the WUR.

So if you blocked off the WUR, the plunger would see the full system pressure. If your stepper or servo could handle the force, it wouldn't be an issue. That could be a sizable force. Looking at the 928 rebuild guide, my highly calibrated eye () estimates the plunger diameter to be around 3/4" dia, so at 100 PSI that would be 44 pounds of force. No wonder the flap needs a good mechanical advantage through the lever. So you would want to bleed this off as much as possible to make the plunger easier to move.

I guess the proper way to block this off, would be to seal off the 'decoupling restriction' and the return line from the WUR to the system regulator, then you shouldn't have any CP?

Or just tie the WUR lines together and return all the fuel from the top of the plunger.

[JFairman]

I just measured the diameter of the control plunger on a spare 930 fuel head and it is 17mm.

The "decoupling restriction" mentioned earlier is just a tiny pin hole orifice the fuel has to go through to reach and replenish the fuel in the control pressure cavity on top of the plunger.

This fuel, after going through that orifice is no longer going to be used by the fuel head for fuel injection into the motor on this trip from the gas tank.. the fuel head is now using it as extremely low viscosity hydraulic fluid pushing the control plunger downward in it's cylinder with 6 metering slits on the side to counter the force from the air flow meter pushing up on the bottom of the control plunger and the WUR or control pressure regulator controls the level of this petrol hydraulic fluid because the WUR can return it to the gas tank faster than it can squeeze through that tiny orifice leading to the control pressure cavity on top of the control plunger.

Yeah... the guy that designed CIS was a mechanical genious.
I wish he did a few things differently to make it more adjustable though.

[911st]

Just keeping the WUR or replacing it with a fixed rate fuel pressure reg is a lot easer than doing surgery on the FD to block the restricter that feeds control pressure.


Jim,

Thx for the info on the Control Plunger size!

Also, do you recall what the hot and cold control pressure range is about?

Do you agree that even if we disconnected the 12v to the WUR it still gets enough heat the increase control pressure?

[WinRice]

Originally Posted by JFairman

I just measured the diameter of the control plunger on a spare 930 fuel head and it is 17mm.

Dang it, that's closer to 5/8", my highly calibrated eye must be off!

[WinRice]

Originally Posted by 911st

Just keeping the WUR or replacing it with a fixed rate fuel pressure reg is a lot easer than doing surgery on the FD to block the restricter that feeds control pressure.

Also, do you recall what the hot and cold control pressure range is about?

I wouldn't want to do surgery on the FD just yet, but if the stepper system works well, that might be the next step in development. Get down to the least parts.

The 'white' book for 78-81 3.3L shows this:

CP Warm -- 3.65 +- 0.20 bar
Full Throttle Enrichment -- 2.90 +- 0.20 bar
Cold -- 1.0-1.45 @ 10C to 2.6-3.0 @ 35C

So using Jim's dia of 17mm, and a warm CP of 3.65 bar, that gives 18.62 lbs of force on the plunger. That's still a pretty good force.

[JFairman]

"Do you agree that even if we disconnected the 12v to the WUR it still gets enough heat the increase control pressure?"

No, I don't think heat transfer from the engine would ever come close to raising CP to full operating temp specs...

The bimetallic springs in both warm up devices get 12 volts continuously from the rear fuel pump relay and they both need it.
When getting 12 volts the WUR is fully warmed up and CP is as high as it will get in about 1-2 minutes after starting the car.

Both mechanical warm up devices are mounted on brackets that partially isolate them from heat soak from the engine case. They get some heat transfer and react to it but not enough, even after driving and then parking and letting it heat soak for 30 minutes on a 95 dgree day in S. Florida.

It's easy to test that.. just unplug the heater element plugs form them and see what happens on a hot day while the engine is hot. Then drive tha car.
The result on mine when doing that is it runs rich from the WUR not getting hot enough and it idles around 1800 rpm from the AAV not getting hot enough.

[IMONBOOST]

Parts sourcing for prototype update, today I went out to a couple of Junk/Salvage Yards thinking they would be begging to get rid of CIS devices. Even went to an old friend from back when I was hot rodding watercooled VWs, he now owns a great Water Cooled VW Service Center and told me the CIS systems are scarce. Turns out nobody has them, this was a complete surprise, specially when just about every european car from the 70s and 80s had such a system on them, but not a show stopper, I will try ebay, if not then the Carrera 3.0 will have to become the prototype and test environment.

On another note, based on research, a regular stepper motor will not give us the resolution and speed that we need for accurate control so I am looking for the right servo motor and driver combination. I was also thinking of an intermediate prototype phase just to test the ability of the servo to control the plunger by controlling it with a MAF and an intermediate signal conditioner in between. The reason behind this, the plunger is controlled by an air meter, a very archaic by today's standards, but that's what it is. So I am thinking of a Fly by wire Plunger Controller by reading Mass Air Flow from a MAF sensor and not having to touch the rest of the cars setup. It would be a stand alone solution.

911st, WinRice and the rest of the crowd, keep up with the conversations your having, they will become very helpful soon.

[IMONBOOST]

BTW - Looks like we might need to keep the arm to reduce the torque required by the servo motor. Regardless, it will not interfere with air flow because air will no longer have to go thru the whole FD, plunger box assembly, all we have to do is put an Air filter straight to the turbo inlet go BOV to atmosphere. Just thinking out loud.

[WinRice]

Originally Posted by JFairman

No, I don't think heat transfer from the engine would ever come close to raising CP to full operating temp specs...

That's what I've found on mine. It get's enough heat to change the CP, but not enough to go into full warm mode.