CIS Flow mods, who can help/enlighten

[awjens]

The shop made 6 spools. They are ready for EDM. The nozzles will be completed this week. I am building a stand to flow these. I took a 2.7, 3.0 SC, 3.3 Turbo apart. They took pictures of the slots (and measured them)and they are checking the nozzles with pin gauges. Oddly enough the 2.7 appeared to have a 1.0 mm longer slot than the stock 3.0. I will have to confirm this as well as the nozzle sizes. After talking to Reanimotion I think for my boosted engine the solution is to get sufficient fuel flowing thru the nozzles and slots with the frequency valve closed for most driving, and then when I need more fuel the MS will control the frequency valve and get me the extra. I don't think this will be easy, but I thinks its possible. I am going to run some tests on a stock SC 3.0 that is on the stand. I'm concerned about low speed drivability and AFR. Opening this up too much and it will be pig rich on the low end. It may be that the frankenCIS and MS can handle the changes thru the WUR circuit and for the boost let MS run the frequency valve. If anyone has a good source for the fittings on the fuel distributors please chime in. the system will have the pump, accumulator filter to simulate the car. I flowed two heads, then reassembled them and flowed them again. I did this 5 times on the SC head. Moving the position of springs, nozzles, and the pieces under the springs had little to no affect on the flow numbers. It appeared the highest one stayed in the same spot no matter the position of the other parts. this might be related to the spool and slots as that always stayed in the same position.

[jsveb]

Updates?

[awjens]

Been out of town so this has taken a back seat. Hoping to assemble and flow the head with mods over the next week. Other car is done so hopefully I can come up with the fuel I need thru this head so I can finish this one. I don't like running the additional injectors and having fuel in the airbox.

[kevin930t]

Any good news??

Sent from my SM-N910T using Tapatalk

[awjens]

Flowed some more heads and took some measurements. All the parts are manufactured waiting on results of flow and some calculations before we modify anything. This is from a -027 head.

[micheloaks]

updates

[Phoffren]

Has this project finalized?

[awjens]

The spool bodies were made teardropped shaped for for more fuel on the high end. I used a CNC EDM machine and used an oscillating method we used to produce shaped holes in turbine blades for Rolls Royce jet engines using round tungsten electrodes. I believe the original EDM work was a shaped graphite electrode. To avoid the brittle graphite I opted to use the tungsten and move the body back and forth enlarging the slot. This way I was able to modify the same spool, (it took 7 attempts) each time increasing the width of the slot at one end. We measured fuel flow at WOT and weighed the fuel to see the percentage of increase after each cut. I had trouble with leaks after re-assembling the head. Someone on here told me of the Indian Head shellac sealer and that solved the leak problem. Mike at Franken CIS helped with the tuning. The car was completed just before I moved in 2016 and it started easily from -10 F to 90. I had plenty of fuel and boosted it a high as 15 LBS. I had the microsquirt in auto tune and drove it only around 200 miles before I sold it. The car is now in the UK. The bottom line is these heads can be modified but to get more fuel the slots in the body had to be bigger. You can get a small increase in flow using the adjustment screws on the head, but its minimal. I believe some people claiming to increase the fuel flow on here did just that. They slots were the limiting factor. I had installed knock sensors along with the map sensor, the cylinder head temp sensor and a throttle position sensor. All of these were wired into the microsquirt. I don't have any more air cooled 911's so for me this adventure is over. The airbox with the pressure relief valve was key to keeping this thing from popping airboxes. It was 3/16" aluminum tig welded on a fixture. I believe there are pictures of the finished product on here someplace. If I find the pictures of the modified spools I will post them. They were taken on my old android phone. I logged in here today as I am back in Michigan cleaning the garage and I found the engine stand I built to run this engine out of the car. That was key as I had to keep r&r'ing the fuel head to see if the flow was increasing.

[moparrob]

Thank you for your service sir. I just found this thread and must say it has been the most informative piece I have ever read, which provides an accurate and scientific discussion as to the limitations, and potential solutions thereto, of the Bosch CIS system as it relates to our air-cooled Porsches.

I am in awe of the time you spent, and your dedication in trying to achieve a solution to the limitations contained in this 40-plus year old design.

You have raised the bar and have motivated me to push my own limits as I explore other more contemporary solutions to this dilemma.

Thank you.

[pkabush]

It’s a shame you sold that beast. Amazing motor in so many ways. I love that engine test stand you have f/s as well. I wish it were closer.
I may have missed it but, do you have any more modified spool bodies available ?

[moparrob]

Subscribed for any more recent activity or thoughts on the subject.

[Edelweiss]

It went the way as forecasted ...