CIS to MFI

h20cooled7 · 03-10-2009, 04:47 PM

I almost have had it with CIS! Tired of chucking money at this fuel system! Whats the list of crap I need to convert to MFI? Or is there a link somewhere on here? Will this kill the value of my car or increase it?

RarlyL8 · RarlyL8's Garage

MFI is difficult for a 930 as you need to recalibrate the pump and fit everything.
EFI is expensive unless total DIY.
Have you tried stripping off the entire CIS, cleaning and re-installing only the parts absolutely necessary for function? Vac leaks and aged off-spec components are a difficult thing to troubleshoot.

Speedy Squirrel · Speedy Squirrel's Garage

MFI? Yeah, I think that will hurt the value a tad. That would be, like, Amish Turbo or something. Do not shun electricity. A nice EFI install, plus keeping all your original CIS stuff would add to the value. While not cheap, its not harvest a kidney expensive either.

h20cooled7 · 03-11-2009, 06:45 AM

heres the list
Brian Leask wur w/heavier diaphram
remaned Jaytan fuel head
r/r intake check for any leaks,also r/r injector blocks with seals
front and rear fuel pumps
new plugs wires
innovate a/f guage
system pressures at 90 psi
cold pressure is 50 psi
warm pressure 70 psi
tried adjusting down but would not go below 30 for my temp at the time
resent back to Brian he bench tested and said it was back to spec
reinstalled and still have the above pressures
want to try another warm up regulator to see if pressures come down.
is there anything else that would throw my pressures high?
Pete

stownsen914 · 03-12-2009, 06:46 AM

MFI can work well for a normally aspirated car, but I suspect you'd have a really hard time making it work well on a turbo. By the time you finished all the trial and error of calibrating the MFI pump (which could require multiple rebuilds by a qualified pump recalibrator), you would spend lots of time and probably lots of $$ too.

Scott

JBL930 · 09:09 AM

MFI is mega bucks, but top dog for high HP, 935's used this set up, as did some F1 engines. I believe the old 2.7RS was also MFI.
You could probably buy and install full Motec EFI, with a full engine rebuild for the same money as just getting the parts you need. This is the system fitted to the 935 Kugelfischer

onboost · 03-12-2009, 09:04 AM

You think you've got issues now, MFI is a whole nother learning cure especially with a Turbo.. how much you wanna spend?

Understand you're a VW tech, know you're way around the system to some degree and have access to the tools. However, since you've been "chucking money at this fuel system," and it still ain't right... why not get it to one of the local gurus that we're lucky enough to have in our area and get it dialed in?

Closest guy to you is... Taylor Chapman@ German Auto Group in Springfield..
Then there is :
- Intersport in Tyson's corner
- ASG in Merrifield/Dunn Loring
- IMA Motorsport in Chantilly
- Auto-Therapy in Gaithersburg (Roger is the 930 Tech-rep for the local PCA Chapter)

Your call Poppy..

RarlyL8 · RarlyL8's Garage

I don't believe you acually meant to say MFI, but rather EFI. MFI is not a viable alternative for most.
One point that is suspect is the rebuilt fuel head. Even though you have a system pressure of 90psi your fuel head may be flowing incorrect volume. You only need a fuel head and a WUR for the car to run. Concentrate on those two components.

h20cooled7 · 03-12-2009, 09:29 AM

God nobody wants to touch this one,almost rebuilt this whole injection system!

Helmsy · Helmsy's Garage

I feel your pain h20 and as you are aware I am in a similar situation with mine.

I am sure there is an answer and you might find by taking it to someone and getting them to look at it and give you their opinion (before they do any major work) may just have the answer you are looking for. It may take a few 'experts' to have a look and come up with a solution.

The only other viable solution I would consider would be EFI but I don't have the dollars or the time and I am sure/hope we can make this CIS work the way it was intended.

h20cooled7 · 03-12-2009, 03:50 PM

Helmsy ,didnt ditch you, just frustrated! wanted to have the answer for you though.I was able to get system pressure back up to 90 psi with a new front pump. Im sourcing another WUR to substitute my current setup,Im convinced its the WUR,but could be wrong. The bring it to a specialist option played through my mind,but Im a full time Volkswagen Tech and a weekend warrior wannabe Porsche Junkie,and hardheaded ,and dont want to give up yet. I hate to see a Awesome Vehicle sit , while my Harley neighbors are firing up their crap. No offense to Harley owners but a flat six with a Zork blows their $h!t away!

cole930 · 07:03 PM

H20,

I don't know what all you've done but here are a couple tips you might try.
System Pressure is ok but if it seems not to stay where you want it.

Just as a place to start pull the pressure regulator out and clean everything with solvent and replace it.

Now your control pressures suck. Should be looking at around 26 cold and 50 warm +/_ 3 . Anyones first suspicion would be WUR but if you just got it back from Brian saying it was good yet on your car it turns to s--- again, check the following.

Restriction in the return line from the fuel dist. to the tank
Restriction in the return line from the WUR to the fuel dist.

Take the lines loose and blow them out, check inside all the fittings and orifices for s---.

Hope this helps. CIS isn't impossible you just have to outlast it !!!!

Cole

DDDD · 03-12-2009, 08:01 PM

Wouldn't it be easier to go to carbs than MFI?

Carbs look awesome.

h20cooled7 · 03-13-2009, 05:09 PM

So does mechanical injection, but wouldnt want the problems that go along with that system!

h20cooled7 · 03-13-2009, 05:10 PM

Cole thanks for the inside tip ,Ill print out and check this weekend!

cole930 · 03-13-2009, 05:44 PM

H20,

Hope it helps. Bosch says only 3 things will cause CP to go high on a CIS. Those two areas that may be obstructed or a faulty WUR. According to Brian's saying the WUR is good you've got a good shot at finding the problem. Good Luck !!!!!!

Cole

h20cooled7 · 03-14-2009, 02:30 PM

Is a 1980 supposed to have a frequency valve,if so would there be any advantage to unplugging this? In some of the pics in the Porsche repair manual they dont show a frequency valve,just a straight hose.

h20cooled7 · 03-14-2009, 03:16 PM

I was just taking the return line from the WUR to the distributor and blew out to make sure it wasnt clogged. I noticed fine water droplets on the end of the banjo fitting. As I stated before I started having this problem after refueling. How can I be sure I have water in the fuel? I just had the fuel level sender out and didnt see any debris in the tank or anything unusual in the tank.If water is present will this raise my cold and warm pressures? and can I use a fuel system drier or a BG product to clear this up without having to disassemble my whole fuel system? What components will water damage if left to fester to long?

Ken911 · 03-15-2009, 11:38 AM

I had the very same issue with mine when it was first started up . the car had been apart for several years. it ended up being a clogged fuel head. I also had an adjustable WUR and sent it to Brian to be rechecked. I put that imagine auto fuel head on it and it worked great after that. there were a lot of other issues with the fuel system from it sitting so long but the high pressure problem was the fuel head.

h20cooled7 · 03-15-2009, 12:08 PM

The fuel head was done by Jay tan recently and it was doing this before I had them do it. I took off all the return lines and didnt find any obstructions and blew everything out with compressed air and reassembled . I retested the pressures and they did not come down. Im trying to find a new WUR now and see where that takes me .