CIS Flow mods, who can help/enlighten

[kevin930t]

No problem,i will get it out tommarow....and good luck.I have complete faith in what u r trying to do..

Sent from my SM-N910T using Tapatalk

[Reanimotion]

There are three primary components in the fuel head that dictate fuel flow.

The piston or spool cartridge via the primary metering slots
The diaphragm and preload springs
The chamber outlet nozzles

the metering slots and outlet nozzles are the fixed mechanical restriction points for overall flow capability

The fuel pressure balance in the upper and lower chambers dictates the amount of diaphragm deflection and therefore the measured flow

Iron heads with the stainless steel diaphragm are operating on a fixed spring preload of 0.2 bar so are wholly dependent on the increase in fuel pressure between the two restriction points to deflect the diaphragm and allow fuel out

Iron Lambda heads alter the chamber balance via the frequency valve and trim the fuel flow, but have the same or very similar overall flow restrictions at the spool and outlet valve.

The later alloy heads have a synthetic rubber diaphragm and ceramic valve discs so have a greater range of movement for trim purposes but retain the two primary restriction points in the spool and outlet valves

The last gen CIS-E heads are inverted internally with the preload springs below the ceramic seats allowing a true fuel cut option via the electronic control but essentially operate on the same principals as the earlier designs.

the earlier spool comparison photos should also be considered in tandem with the below example of the outlet valve sizing

Originally Posted by Grupp-A

Here you can see the different size of the nozzles between the stock 911/930 head and the race head. I don´t have any pictures to compare the metering slits.

[Speedy Squirrel]

Excellent summary. I did not know about the different diaphragm materials. FYI, American Precision Machinery is a manufacturer of repair kits. Here is their repair instructions:

http://www.cis-jetronic.com/public_doc/07.3-0997-06.pdf

You will probably want to develop that ability in your own if you are going to do a lot of experimenting.

[Mr9146]

Originally Posted by awjens

I expect to change the injectors, a new better pump is sourced. It appears the lines will flow enough, The fluid engineer is working out flows thru the lines. He wants to better understand the pressure system. Pressure affects velocity which affects volume.

Taking the pumps, filter and accum. Will do these tests as it would be in the car including the length of lines from tank to engine.

He will have the head tomorrow. I'm taking it off a car i have. I was unable to find a Bosch head on ebay for 6 cylinder porsche. Every place I called to buy one wants exchange. If somebody has one that needs rebuilding we will rebuild it for free if we can use it to learn.

The steel pump diaphrams have been traced and can be cut on the wire EDM. If we start it at the end of the day, we will wake up to a new one in the morning. stacked on top of each other we can cut several at a time. Waiting to hear what affect those play in the system. (I got new ones in a rebuild kit).

I probably have a 2.7 or 3.0L non-lambda head floating around. I might be willing to donate to the cause... No spare turbo fuel distributors, though.

[awjens]

The head went to the lab this morning. It is a 0 438 100 077 with Lamda. First off I gotta say for a car that has sat for most of its life, it was incredibly clean inside. No deposits, no varnish, nor foreign debris in the screen around the metering spool body.

What a precision device. I tore it apart before our meeting at 1pm today.

We had a meeting with the four partners in this business about a future development process. So today I have at my disposal the engineers that design the tooling, fixtures etc. all at the table in the conference room. Combined 150+ years of the EDM business. After the meeting we got to the big problem... The Bosch Fuel Head.

As luck would have it one of the engineers that does development work and trial burns was at that table and said "is that a bosch fuel injection part". I said how do you know. He took me to his toolbox and showed me a very similar barrel. He had done test cuts on this thing years ago, couldn't remember the specifics. Small world. There are not identifying numbers on this spool, only the letters ELO.

The shop supervisor told me in batches of at least 6 they can produce new barrels all together. He is going to get me a no margin price, approx. 500.00 each. I may have him make me 6. Most tolerances .001 is sufficient, except the id of the spool. Ground then honed to size matching the plunger. the rest is o-ringed.

They took a lot of other dimensions so I can calculate flows.

Waiting for the fluid guy to read some and look at all the pictures, cross porting, chamber volumes, diaphragm plate thickness (.004" on this head), spring pressures etc.

Then they examined the barrel. It has 6 small pockets 60 degrees apart that were milled in the barrel, with a shaped end mil creating rounded ends on the rectangular pocket and a flat for the surface to be EDM'ed. You can see the end mill swirl marks on the flat surface. The slot was cut with a shaped electrode plunging straight down. They know this because the slots are square on the ends. If it had been wire cut they would have been rounded. I thought maybe they wire cut it because you could burn straight thru on both sides and due to the fact there are 6 cylinders 180 degrees opposite is another slot. However their explanation was hard to dispute when zooming in and looking at the squared off corners. Not perfectly square due to electrode wear but certainly not rounded from the wire EDM process or shaped hole drilling method. They also said to wire this would mean constantly "rethreading" the wire for each slot. Hardly suitable in production.

The slot was approx. .125 MM (not inches) wide, 5.0 MM long. They will have better measurements for me. It wasn't critical today. I would love to see the blueprint on this....

Comparing the slots (look at picture 1 VS. picture 3) they didn't always get the slots exactly parallel to the milled slot. So they are not perfect......

In conclusion they said they can make an electrode that size or smaller and recut the slots. There will be approx. .001" overburn. so a .006 inch slot requires a .005" electrode. They said plenty of room to burn thru to minimize taper.

So its in the works, can it be modified? They say nothing they found today leads them to believe it cant be done. Examining other heads with other flow rates will help identify exactly what they changed, that can be crosschecked with the fluid engineer. I told him he doesn't get flow slot dimensions from head #2. I want to see if his math comes up with the flow rates I observed with this slot size and all the other variables for head number 1 the -077.

Working with this group on Pelican and the guys at the shop and lab on this attempt is a thrill. When I got into these cars years ago I wouldn't have touched this distributor. The more I see the more I am astonished at the quality of this assembly. Simply brilliant people designed this. And it is so reliable.

[awjens]

Originally Posted by kevin930t

No problem,i will get it out tommarow....and good luck.I have complete faith in what u r trying to do..

Sent from my SM-N910T using Tapatalk

I cannot thank you enough. I will take good care of it. Notice the storage of the parts on this head....

[awjens]

Originally Posted by Reanimotion

There are three primary components in the fuel head that dictate fuel flow.

The piston or spool cartridge via the primary metering slots
The diaphragm and preload springs
The chamber outlet nozzles

the metering slots and outlet nozzles are the fixed mechanical restriction points for overall flow capability

The fuel pressure balance in the upper and lower chambers dictates the amount of diaphragm deflection and therefore the measured flow

Iron heads with the stainless steel diaphragm are operating on a fixed spring preload of 0.2 bar so are wholly dependent on the increase in fuel pressure between the two restriction points to deflect the diaphragm and allow fuel out

Iron Lambda heads alter the chamber balance via the frequency valve and trim the fuel flow, but have the same or very similar overall flow restrictions at the spool and outlet valve.

The later alloy heads have a synthetic rubber diaphragm and ceramic valve discs so have a greater range of movement for trim purposes but retain the two primary restriction points in the spool and outlet valves

The last gen CIS-E heads are inverted internally with the preload springs below the ceramic seats allowing a true fuel cut option via the electronic control but essentially operate on the same principals as the earlier designs.

the earlier spool comparison photos should also be considered in tandem with the below example of the outlet valve sizing

Now this is what we are talking about...... Great information. I will print this and pass it on to the fluid engineer.

[kenikh]

Best thread in a very long time. Cheers.

[awjens]

Originally Posted by willtel

I've got a cast iron fuel head off of a '79 930 engine if you need another one.

IMG_0890 by willtel, on Flickr

I can use any heads that offer potentially different flows. The same care will be taken with all. Packaged, labeled etc. Whatever you can do to help.

[awjens]

Originally Posted by Speedy Squirrel

Excellent summary. I did not know about the different diaphragm materials. FYI, American Precision Machinery is a manufacturer of repair kits. Here is their repair instructions:

http://www.cis-jetronic.com/public_doc/07.3-0997-06.pdf

You will probably want to develop that ability in your own if you are going to do a lot of experimenting.

Good news here. They can buy this material already to thickness. They can stack them and wire cut 20+ at a time. They can also grind custom thicknesses. This surely plays an important part to the whole story. Mine was .004" thick. I ordered a kit, forget where from. Will be interesting to see if thickness is exactly the same.

[Reanimotion]

Required reading -> Bosch K-Jetronic Fuel Injection - Technical Instruction

[awjens]

Originally Posted by Reanimotion

There are three primary components in the fuel head that dictate fuel flow.

The piston or spool cartridge via the primary metering slots
The diaphragm and preload springs
The chamber outlet nozzles

the metering slots and outlet nozzles are the fixed mechanical restriction points for overall flow capability

The fuel pressure balance in the upper and lower chambers dictates the amount of diaphragm deflection and therefore the measured flow

Iron heads with the stainless steel diaphragm are operating on a fixed spring preload of 0.2 bar so are wholly dependent on the increase in fuel pressure between the two restriction points to deflect the diaphragm and allow fuel out

Iron Lambda heads alter the chamber balance via the frequency valve and trim the fuel flow, but have the same or very similar overall flow restrictions at the spool and outlet valve.

The later alloy heads have a synthetic rubber diaphragm and ceramic valve discs so have a greater range of movement for trim purposes but retain the two primary restriction points in the spool and outlet valves

The last gen CIS-E heads are inverted internally with the preload springs below the ceramic seats allowing a true fuel cut option via the electronic control but essentially operate on the same principals as the earlier designs.

the earlier spool comparison photos should also be considered in tandem with the below example of the outlet valve sizing

Got a call from the fluid guy and we discussed this diaphragm. I think I saw a rubber diaphragm in some heads. He's concerned about the role the diaphragm plays in fuel quantity. He said this this is very unique device, especially for its time.

Can anyone confirm a head with a rubber diaphragm. Possibly 930 heads or higher flow? Or did they just switch to steel because of the rubber deteriorating?

[Reanimotion]

evolution is as follows

First
Iron head = Stainless Steel diaphragm (SS used directly as valve surface)

then later (until production stopped in the mid 90s)
Alloy Head = Synthetic rubber diaphragm and ceramic valve discs

As far as I'm aware
All SS diaphragms are paired with iron bodies
All Synth rubber/Ceramic are paired with alloy bodies

[Reanimotion]

the diaphragm material itself plays no real role in the operation of the head other than range of movement.

your steel head with FV between 0v0 and 12v0 gave around a +18%/-18% trim range

Eddies 924/931 head is alloy and produced +50%/-25% range

[Rawknees'Turbo]

^^^

Steve, I've read in the past that the move away from the stainless steel diaphragms was due in part to their tendency to become dented (such as with fuel pressure spikes); is that accurate?

[awjens]

Originally Posted by Reanimotion

the diaphragm material itself plays no real role in the operation of the head other than range of movement.

your steel head with FV between 0v0 and 12v0 gave around a +18%/-18% trim range

Eddies 924/931 head is alloy and produced +50%/-25% range

So are all the stainless diaphragms the same thickness?

Switching to Alloy Heads with the rubber diaphragms had no affect on flow?

When they made the change were any of the orifices sizes changed? Example same displacement engine with alloy or Cast head.

[Reanimotion]

Originally Posted by awjens

So are all the stainless diaphragms the same thickness?

Switching to Alloy Heads with the rubber diaphragms had no affect on flow?

When they made the change were any of the orifices sizes changed? Example same displacement engine with alloy or Cast head.

I believe they are all the same thickness
As they just create a flexible barrier between the upper and lower chambers, changes in thickness would have absolutely no effect on the chamber volumes when static, but would impact on the pressure differential movement if too thick.
They just have to be thin enough to flex the correct amount for the pressure flow and thick enough to seal the outlet ports without deforming.

Originally Posted by Rawknees'Turbo

Steve, I've read in the past that the move away from the stainless steel diaphragms was due in part to their tendency to become dented (such as with fuel pressure spikes); is that accurate?

I doubt it, the move would more likely have been because of the change to alloy bodies and the introduction of electronic control of the FV.
The rubber gives additional range for trim control.
The alloy is less prone to corrosion and easier to manufacture/machine and isn't compatible with SS.

[Reanimotion]

Originally Posted by awjens

The slot was approx. .125 MM (not inches) wide, 5.0 MM long.

The two important measurements so we can model and compare the various part numbers are simply the spool orifice length and width and the outlet orifice diameter
Can you accurately measure the outlet diameter on the heads you have apart?

I have a number of units here I can do the same on
Non-lambda iron head 100-027 Porsche 928 (all markets)
Lambda alloy head 100-088 Mercedes 560 (USA)
CIS-E alloy head 101-018 Mercedes 560 (USA)
CIS-E alloy head 101-016 Mercedes 560 (rare rest of world or “Euro” AMG)

[pkabush]

Originally Posted by kenikh

Best thread in a very long time. Cheers.

I'll second that. Really interesting and informative stuff. And huge props for sharing with the community. I can see this along with the great work Steve has done going along ways to help us CIS junkies get more HP out off our old sleds.

[pkabush]

Not sure if you're interested in a Euro 930 FH (higher flow cast iron) but if so I can part with mine for awhile. My motor has been out far too long long and the reality is it won't be going back in for at least two more months.