Update:
Fixed the breather cover leak, but found 3 drips from the lower cam covers :(

Ho Hum.

ok, finally all the oil leaks are sorted.

Now, I'm intent on getting the afr sorted at part load, so does it make a difference with & without the air intake shroud ? (Thats the big piece with the air filter in it).

I'm guessing it would affect the amount of air intake, but mabye not.

It would be easier to get at the adjustment screw with it off, but if it affects the afr setting, then I have to leave it on.

Thanks. I'm determined to get there before 12 months have passed !!

It has been nearly a month and I am awaiting an update. I hope that the news is good and the only reason you have not posted is because you are flying through the paths of Europe.

Well, ahem, I'm emabrassed to say I've done nothing since.

I *will* get back to it soon.

I still have to check fuel pressure & flow, and then do the afr adjustments.

ahem, Looks like I missed my 12 month target :(

Still havent finished CMA :(

Sir G. - Ahem, some of the components are going to die of old age and dis-use first. :D

Best,
Your American namesake :) ,
Grady

yeah, go on. rub it in. ;)

and today .... I got the insurance forms in the post.

Next week ... next week.... :)

next week. ;)

OK. Taxed & Insured again :)
Now, have to blow off all the dust & get back to it. Has it really been 15 months since I started this thread ?

Anyway ... I have a few CMA steps left to do.

Check Pump timing
Measure Fuel Pressure
Measure Fuel Flow
Measure & Adjust AFR part load & idle


One thing that has been bugging me is that the hand throttle is loose. It does operate the throttle correctly but will not stay in position. When I let go of it, it simply falls down again to the off position. Is there a quick & easy fix ? Any pointers to other threads on this. (I did search !)

I presume it is assembled with the heater hand controls somehow so I'll go off and lookup the PET to see if it shows any decent diagrams.

Cheers,
Declan

edit: found this thread http://forums.pelicanparts.com/porsche-911-technical-forum/453965-missing-hand-throttle-68-coupe.html with some good info on it. I guess I need some of the cork friction washers.

OK, here we go.
I need to measure fuel pressure & fuel flow.

I've been reading up on the plumbing at the fuel filter & found Grady's photo of the corrected plumbing:
http://forums.pelicanparts.com/uploa...1226671174.jpg

OK. So I plumb my fuel pressure gauge into the return from the MFI pump: Good.

Next, for fuel flow, where should I measure this magic figure ?
Is it the flow from the filter to the MFI pump ?

I plan on doing the suggested return line into the fuel tank filler, letting the pump run for a while, then measure flow, then let it flow back into tank again for a while, measure flow rate again ... etc etc.
How long is "a while" - How long should I let it run back into the tank between measurements of flow ? 10 minutes ? 20 minutes ?

Thanks,
Declan

Right, new fuel filter in, and measurement done.

Fuel pressure without engine running is a little over 0.8bar, mabye 0.81 or 0.82. Thats 11.75psi.
Is the 11.8psi spec without engine running ?

Fuel flow. 1150ml in 30 seconds, or 2300ml in 1 minute.
I believe that is within spec.
I measured, let it flow for 5 minutes, measured again, then 10 minutes, and up to 20 minutes.
Same figure each time, so thats good.


Little CMA progress, but more than I've made in the past few months :)

I guess you folks have given up on me :(

Anyway, I checked fuel pressure again, and got around 0.65bar without engine running.

This confused me, as I originally got just over 0.80 bar.
I started the engine to see what effect, and it increased to around 0.75bar.
Revving engine made very slight fluctuation.
If I rev to around 3K, (at a guess) fuel pressure drops to around 0.65, but only for an instant, then climbs back to a steady 0.75bar and stays there.
if I drop the revs to idle, it stays at 0.75bar until I rev again, then a momentary drop & back up to 0.75bar

I preume this is good, as 0.75bar = 10.8psi and even the low 0.65bar = 9.4psi
All within spec of 11.8+/-3psi

Any advice / Suggestions ?

Is there any problem in using 8mm fuel hose instead of specified 7mm between the fuel filter & the mfi pump ?
I wouldn't think so, but thought I should check.

Ahem, cough cough.

I've been waiting since May for an answer.








well, thats my excuse for not having done any miles in the car since.
Next year. Next year. Really.

More to come later today or in the morning.
Have to run earands now.

Best,
Grady

In the meantime, I've been reading the CMA bible again.

If I understand correctly, for part load, I need to set a 9 degree angle on the
throttle plates (butterflies).

Am I understanding correctly, that I can use either

A. the special tool that clamps onto the mfi pump, (pics below from cma)
or
B. the hand throttle


But, how do I measure the 9 degrees ?

I presume I can make a tool of some sort with the 9 degree angle, but I just cant see how I can measure 9 degrees without the protractor.

Please tell me I'm just being silly, and its simple.

Thanks,
Declan

http://i24.photobucket.com/albums/c2...l_in_place.jpg

http://i24.photobucket.com/albums/c2..._load_tool.jpg

Long time no update ...

Finally got some miles on it, still tweaking mixtures, but am a bit confused at something.

I can adjust part load AFR & adjust idle AFR to nice levels.

However, when driving along at low revs, sub 3k, (maybe sub 2.5k ?) if i completely release the throttle and use engine braking, AFR goes very very lean eventually up to 19:1 / 20:1 - as if its just not getting any fuel at all. If I change down a gear and do the same thing at higher revs it seems fine - Does go a little lean, but nothing major.

Any ideas ?

Should I suspect the link from throttle "bar" to mfi pump ? I did measure it previously and it was exactly right length.

Apart from that annoyance it seems to be running very very nicely and really comes alive at about 5k revs and up. I had forgotten how good it was on the road. :)

Do you have the microswith connected which basically shuts fuel off on throttle lift?

Nope. Microswitch is removed, but cables arent insulated.

However, that should not matter, as the fuel cutoff relay/control circuit is also removed for repair. (the famous "rattle from loose transistors")

if you have the microswitch hooked up this might be normal. Is the switch and solenoid and speed sensor box all working?

When you close the throttle WITHOUT the speed switch cutting off the fuel, it's going so rich that it's overloading your sensor. I bet you have fire coming out of the tail pipe. The only other answer is that you've got the idle adjustment way too lean and the main rack way too rich and it's transitioning between the two.

The lean AFR numbers on decel are to be expected when you remove the decel enriching system. That microswitch controls the large solenoid on the pump, which on throttle closed decel enriches so you don't get backfiring.

Hmmm.

What's throwing me is that when on load, at higher revs, AFR is good. Its only at lower revs and no throttle that it goes way lean.

I thought the speed switch & no throttle caused it to cut fuel, to stop the flames out the tailpipe, not enrichen it ?

Could be wrong, thats what I was told. Then again, I do get confused easily.

declang, You are correct. The speed switch/RPM transducer/solenoid are set up to cut off the fuel on decel.

Perfectly normal and nothing at all to worry about. Decell AFR's don't mean a thing. You actually want it to read very lean.

Absolutely correct. It's called a "shutoff solenoid", not an "enrichment solenoid".

As you are discovering, however, you really don't even need that pesky little devil, the speed switch, or the switch on the rack. The mix goes lean enough without all of that claptrap to accomplish what it is supposed to anyway, which is to minimize wasted fuel on decell and/or washing of the cylinder walls.

When you lift and completely close the throttles, the pump returns to its idle delivery position. It has no way of "telling" how much air is going into the motor. At higher than idle revs, despite the closed butterflies, the motor is simply drawing in more air. Hence the lean mix. And again, that is exactly what you want on decell. Don't touch a thing.

Thanks Jeff. That sounds much more promising.

I'll have to try a few more miles & see how it goes.

Cheers :)

Uhh, you do not want a 20:1 mixture under any circumstances. Given the design of the engine, that mixture won't burn anyway- I stand behind my suspicion that if the engine is actually running and you're showing 20:1 it's false informaiton.

Bosch designed the MFI system and wouldn't have included the speed switch and overrun shutoff if they didn't think it was important to keeping the plugs clear and the fuel consumption low. When you snap off the throttle, the rack doesn't instantaneously return to idle, it takes time. Slamming the rack forward with the solenoid was their workaround to an excessively rich mixture given the behavior of the pump.

I'm not disagreeing with you Jeff, I don't have a speed switch on my race car, I find that it's helpful to keep guys off my bumper at the end of the straights when fire shoots out of my M&K exhaust. But it is counterintuitive to believe that at closed throttle the mixture goes lean-- usually it goes lean at WOT in the upper rev range.

Declan: try this-- with the engine warmed up, turn the idle adjuster two clicks left and note the reading on the AFR. Then turn it two more clicks left and note that. I bet you that rather than seeing a mixture that goes from 20:1 to 25:1, you see a mixture that goes from 20:1 to 10:1 even though you are LEANING the idle mixture. . . If it doesn't it's easy to click everything back. . . and keep going with the idle mixture, clicking to the right, until you get to 14:1.

With no load on the motor (full decell) it could be sucking almost pure air and it would not hurt anything. The motor isn't really "running" per se under these conditions, it's being driven, and would never continue to run on its own on this lean of a mix.

The systems I have checked with my LM-1 that have the shutoff circuit intact do, in fact, go leaner than the ones without one, just like we would expect. Well over 20:1. The shutoff solenoid seems to force the rack even further forward than the normal idle position.

The flyweights remain splayed to various degrees with rpm, so the stylus arm does not return to full idle until revs drop, because the space cam is aft of the idle position when the flyweights are splayed. The shutoff solenoid lifts the stylus right up off of the space cam when it forces the rack forward past the idle position.

So, in the absence of the shutoff solenoid to do that, the stylus continues to track on the space cam. The decell, therefore, remains a bit richer than it would with the shutoff solenoid in place. Not much, though. Mine hits 17-18:1 or more when I lift. The shutoff solenoid pushes it up over 20:1 when it's working. That won't hurt a thing on the decell, under no load. There is no way it can detonate or anything like that.

Jeff is 100% correct and I would like to add that with the 019 RS pump the space cam at zero degree's, throttle closed, delivers less fuel as the RPM increases. 019 RS pump flow spec: 400 pump rpm= 13-14ml; 600 pump rpm= 10.5-11.5ml; 3000 pump rpm= 9-10.5ml. Max throttle and 3000 pump rpm delivers 57-58.5ml.

Thanks for the input folks :) Makes sense to me.