MFI Pump Dyno build- My newest project

[David E. Clark]

The level of technical proficiency of some people on this board is simply amazing! My hat's off to you Mark! Keep up the great work and please keep us up to date.

[356RS]

Thanks to all of you. Scott; The AC Tech unit is the motor control system. The control unit is programmable. I have set the min. RPM for 400 and the max. RPM at 4000 controlled by a potentiometer, set the ramp-up speed to max and the ramp-down to max. the ramp-up is very important because at tests at 2000 RPM and up I need the motor to get there from a dead stop to (example 3000 RPM) in less that 1 sec. At 4000 RPM it takes about 1 sec. At these high RPMs I have to do a little loss calculations at the start-ups.
John; I will post some pictures of the pump that had the intermittent stuck piston.
John Bell; Let me know what you need. I'll be glad to help.
Next Pump will be a RS space cam installation in a 015. I will first flow test the stock 015 and document the flows, then R & R the space cam and recalibrate for RS specs.

[356RS]

I finally got around to taking apart the MFI pump that had an intermittent sticking piston during one of the first pump Dyno Tests. I found corrosion on some of the piston pressure valves. Posting pictures of disassembly so far today.

[356RS]

Well, I found the reason why the piston was sticking all right! I'm surprised they were working at all. The pump head area were the fuel enters and exits is full of corrosion. Some kind of white powder crystal stuff. Photos below show the problem.







What kind of solvent can I use to clean out the pump head fuel area? Look at these photos.



That's an all full lot of buildup in the head.

[jcge]

Thanks for posting all of your findings Mark.

White powder looks like corrosion of the alloy body- a couple of options....modest to extreme
If it is corrosion, the solvent wont help directly, but it will dissolve any other gum/fuel based deposits in the fuel manifold.

1) solvent (eg Shellite, Stoddard, Kerosene etc)
2) solvent in ultrasonic cleaner (mind the fire hazrad..)
3) take it to a local electroplating works - they may be able to strip and passivate/chromate the surface (mind the epoxied in fittings)
4) soda blasting
..
..
99) mask machined surfaces with hot wax then alkali dip - eg NaOH
100) mask machined surfaces with hot wax then acid dip - eg phoshoric, (please don't try HF - very nasty stuff)

The ultrasonic will "chip away" at the corrosion in all of the areas you can't reach

Regards
John

[356RS]

Thanks John. I'll see what's available here in the NW and let you know how it plays out.
It looks like the pistons and related parts can be cleaned up. The rest of the pump and governor are in good shape so I hope I can save the fuel head portion.

[jbell959]

That looks nasty inside... it's deceiving because the outside of the pump looks nice. Hope it cleans up so you can save the pump.

[daepp]

Originally Posted by 356RS

Is that the space cam, or some type of drive shaft?

[356RS]

It's not the "space cam". It is the camshaft that lies on the bottom of the main pump assembly. It operates the pistons in the pump assembly and also extends into the governor portion of the MFI pump and there the "space cam" and flyweights are attached. I will post some photos of all the parts attached to the camshaft.

[daepp]

I find the whole MFI system fascinating - and a little bit scary.

All I know about them is what I've read on Pelican. I drive an MFI car several times a week, and although the engine was rebuilt, the MFI has never been touched.

I am amazed at how well the engine runs, how smooth it is. I am intimidated by having to repair it some day, but until then, I'll just try and learn as much as I can and enjoy driving it!

It is so interesting what mechanical engineers were able to do without computers and integrated circuits. By being smart enough to know the givens, they were able to design a variable system that was both complex and reliable.

[356RS]

Keep driving her David and enjoy. Below is just some of the basic parts. The space cam is the first part to the right of the camshaft, in between the flyweights and camshaft. It has a black zip tie around it.

[304065]

That is magnesium corrosion-- be VERY careful with any acids around it or the thing will literally melt away in your hands. I would blast it with glass beads, make sure you tape over the data plates. Then treat the mag with a browning coating like the one Henkel makes. Or there's a poly-fiber product that's not that expensive.

[WoodSport]

That's a nice test rig, Mark! Let me know if you're interested in automating your test and measurement processes or collecting data; it could help improve your accuracy and repeatability quite a bit. I used to work in precision mechanical and electronic calibration and then moved into writing control software and measurement applications. I've built a lot of home-brew test gear like this and would be happy to help, if possible. I'm not too far up the road from you.

/Jon

[356RS]

Thank you John and John. I will be very careful on how I proceed.

[356RS]

Jon, Funny you should mention that. I have been searching for a "High Pressure, Low Flow Meter" to record the flow in-line before each injector. This would save lots of time during the flow recording process. Timing and reading then dumping the test flows is very time consuming. If I had a digital flow meter calibrated in mL/min and way to record the space cam plots, rpm and throttle degree, that would be fantastic. I have been looking at flow sensors, and so far non of them seem to be able to support the pressures of 250 to 300 psi and read a very low flow rate.

[WoodSport]

That's exactly what I (used to) do - test automation. I've worked with micro-flow meters quite a bit, and I'm sure we can find some suitable units. PM me with your email if you want to discuss the gory details without clogging up your thread here.

Also, I don't have any experience with the space cam but, if I understand the theory properly, I have an idea for a simple and very accurate mapping device, without requiring an aerospace-grade laboratory and lasers. Not that there is anything wrong with lasers - they can be fun - I just can't afford that kind of equipment.

/Jon

[lateapex911]

Wow...awesome effort. It makes me wish I still had MFI on my car....sorta!

(Quick side comment: I got my 911E in 93 or so, and in the late 90s I needed an new engine. Time and money were tight. I ended up upgrading to a 2.7 with Solex cams and SSIs and Webers. Which have been replaced with PMOs.

I did that because, 10 years ago, we just didn't have a community that has such intimate knowledge of the MFI system. At the time, the "gurus" were few, far between and rather pricey. What a difference a few years and the magic of the internet has made.Marvelously ironic that such "modern" technology such as instant data sharing would revive the nearly lost art of Mechanical Fuel Injection tuning.)

Touche' all!

[shbop]

This is great stuff. Very nice Mark. Looking forward to hearing about the cleaning method used.

[356RS]

Well my cleaning method was picks, sharpened narrow head screw drivers, a 12mm drill bit (down through the center bore), wheel cylinder hones, more sharp metal picks, round wire brushes on a drill motor, small round wire brushes on a drummel tool, and 4 hours of elbow grease. I think it's now ready for the "Henkel Magnesium Treatment Kit" I ordered today and will be here by Friday. I think it looks very good inside now. I can't seem to get any more flakes out. Flushed and flushed with solvent then air gun dry. Also used the wire brushes to clean the outer surface of the pump head. I got a little carried away on that.









This is after I spent 4 hours on it:

[356RS]

I know were a little off track on the original thread of "MFI Pump Dyno build" but this all comes together after I reassemble the magnesium corroded pump and recalibrate it. Now remember this pump is totality out of calibration now. Just getting it back together will be a miracle, and the flow test results should be entertaining. You gotta love it.