mfi pump- which one do I have? How to adjust?

[TR]

Hi
I have just got my 2.7RS spec engine running after a long engine building process. The engine is fitted with an mfi pump which was on and engine with a green shroud I thought it was a 2.4E The pump was rebuilt in America about 14 years ago and then put into storage.

The car idles great and accelerates well except through second gear.

I know it is most likely the wrong pump for a 2.7RS spec engine but, is there any thing which can be done to improve the problem of starvation at low speeds. The car absolutely rips above 3000RPM but doesn't like driving in second gear when cornering at slow speeds. splutters a bit. very embarrassing.

I'm at the stage of ditching the whole system and looking for carburettors. It would be a real pity because every thing inside the motor including all the injectors are new.

Pump number is 42123579, type number is 0408 126 019

i'll go out and see if I can get some more info off the pump.

Any help would be good.

thanks

Terry

[TR]

hi can't see any more numbers through the mfi stacks but the distributor number is JFUD-6 0231 184 004

Is this the right distributor for RS cams? and pump?

Thanks

terry

[boba]

You have a 019 pump which is the correct pump for a 2.7 RS. There is a lot of information on this board on MFI. This link should get you started:

Ultimate MFI resources thread

Read become familiar with and use CMA as it is written to set up your MFI. If you have access to AFR meter you can use that to help. On my car after we had it running well we used a high temp gun to check each exhaust primary, and found a variation on one one bank. Ed Mayo was then able to adjust the individual pistons on the pump to get that bank balanced. The car has run great since, that has been over 3 years ago when I switched to a sport muffler. Once you get MFI set it will be very reliable. Changes seem to come with component wear over time or if you are starting with worn linkage or throttle bodies.

Good luck getting it tuned and hope you are enjoying it soon.

[tobluforu]

How are you able to adjust pistons in the pump?

[boba]

I have not done it personally but did watch Ed do it. You have to take off the side cover and the pistons are exposed. You can then turn them which will adjust them up or down and change the volume. This will either richen or lean that cylinder. I think this would be a final, very fine tune after everything is set and working well. We did not have EGT for each port so we used a Temp gun at the port to spot a variance port to port. This was not done by using an absolute temp target. It was done to balance a bank.

[GrantG]

Originally Posted by Terrance Raath

I'm at the stage of ditching the whole system and looking for carburettors. It would be a real pity because every thing inside the motor including all the injectors are new.

Terry - Don't ditch the MFI - it is superior to carbs (power, throttle response, cold-starting, automatic altitude compensation) for a 2.7RS motor when working properly, imo. Since it seems you have the correct pump (and presumably space cam), it is certainly well worth the effort to tune it properly. Use the resources on this board (the adjustments are quite easily made, if the pump is in good general repair).

Good luck!

[BigD9146gt]

Tezza,

As Grant said, try and stick it out! I felt the same way about MFI because I didn't fully understand how it worked... only that it was awesome. However, I debated between MFI and EFI. Carbs have their own headaches too, while initially simpler to deal with, fine tuning for power across the rpm range and longevity they are no match against MFI.

As boba said, start reading the CMA front to back, several times. THEN start asking questions on
the board, save posts and links to posts you find valuable... Your in a great spot mate, there are very knowledgeable guys on this board who are extremely generous and helpful with that knowledge.

I'm getting close to having my pump dialed in, and I gotta say its an awesome and very gratifying feeling. throttle response, sound, dude, mfi is soooo worth it!

Heres my thread, sound familiar? How long did it take you to dial in a 2.8 MFI?

Cheers, d

[TR]

OK
so I was up half the night reading mfi posts and it seems pretty logical to me but as my pump was rebuilt in the USA I don't want to mess with it too much. I will start by measuring all the linkages.

the throttle bodies were also reconditioned but i didn't buy new linkages. best I can do is to try and check every thing.

If my cams are right and the pump is right can the dizzy be wrong?

I bought the motor in 1996 in Belgium from some crazy Flemish guys who operated out of a barn. I went there because these guys could get new old stock Porsche parts. Initially I wanted stock mahle E pistons and a engine rebuild kit for the original 2.2 which is in the car.
I left with a newly rebuild 2.4 ( I thought) in 2.7 RS spec. The guys wife was diagnosed with cancer right in the middle of the rebuild and I was due to leave the country so I just wrapped up the motor and left.

Got back to Australia, put the motor in the car and it leaked oil. Took it out again and sent it to my Ozzy mechanic ( now retired). Pump and throttle bodies went to the USA for overhaul.

Alls back together now only had one minor problem with a leak in the oil cooler.

So being in Australia and far away from any one who knows much about mfi it is going to be a long haul in getting this right.

Option 1 drive the car 1000 miles to Melbourne to the only Porsche dealer who apparently can work on the mfi.
option 2 let the Bosch injection guy give it a go, he's old so i know he has some knowledge, Told me he would have to read up a bit as its been a while since he has had to look at one.
Option 3 Puddle through it.

Funny thing is I have mfi on my old 2.2E and it has always fired up and run perfectly with out any fiddling. pitty about the worn rings.
Anyway thanks for the encouragement, looks like the mfi will stay. Got some work to do.

thanks

Terry

[dicklague]

I would highly recommend a good AFR instrument. That is what really helped me sort out my 2.7 MFI. Our host sells the Daytona Sensors Wego IV and the Innovate. I have the Daytona sensors and love it. I am now involved in the distribution of the Wevo IV now so I may be a little biased, but check it out. Logs 2 hours of AFR and RPM data.

You can get a chart to convert CO to AFR as well.

Good luck. Good running MFI is worth the bother.

[BigD9146gt]

Originally Posted by dicklague

I would highly recommend a good AFR instrument. That is what really helped me sort out my 2.7 MFI. Our host sells the Daytona Sensors Wego IV and the Innovate. I have the Daytona sensors and love it. I am now involved in the distribution of the Wevo IV now so I may be a little biased, but check it out. Logs 2 hours of AFR and RPM data.

You can get a chart to convert CO to AFR as well.

Good luck. Good running MFI is worth the bother.

+1,000,000 on that! I've been borrowing my friends Innovative... the pure definition of an educated adjustment to the MFI.

[TR]

Hi
I'll look into it.
Can any one tell me if im using the correct distributor before i mess with the mfi?

[al lkosmal]

Terrance,
You might want to contact Mark Yung (356RS) regarding your MFI questions. He, in my opinion, is an expert.

Regards,

al

[Jeff Higgins]

I think just about any reasonable advance curve will work with MFI. I ran a couple of different spec distributors on my 2.4 T motor, from its stock unit, to an S unit, and finally a Barry Hershon recurved unit that had full mechanical advance come in at 2,000 rpm. I initially ran my 3.0 (when it was still single plug) on a similar Barry Hershon worked distributor, with full advance coming in at 2,000 as well. Now that it is twin plugged, I run it with an Electromotive unit set up with a very simple curve - 12 degrees initial and 25 total, which comes in at 3,000 rpm.

That's kind of a long way of saying I don't think your distributor can be "wrong enough" to cause the problems you describe. I would begin by going through CMA in its entirety. Don't skip anything, no matter how inconsequential it may appear. Be exacting and precise.

Once you are through that, do what these guys suggest - get a quality A/F meter and use it. I have an old LM1 that I swear I could no longer live without. The information it provides is absolutely invaluable in tuning one of these systems.

And, above all, keep the faith - once sorted, there is nothing more fun to drive. The throttle response offered by this system is still unmatched by anything else.

[boba]

Terry,

I think the dist # you listed may be a Bosch #, the Porsche # is 911 602 031 06.

231 184 004 is the Bosch # as found on this Bosch document, second item down.



http://www.automotive-tradition.de/download/ausruestungslisten/mf1644.pdf

[356RS]

Terry, Your getting great information hear. Also reading the Ultimate MFI Threads put together by David Clark is a wealth of information. BTY you have a very good source of MFI information in Australia. Look up John "jcge" on this board.
Jeff Higgins and others have mentioned getting a quality A/F meter, and I must agree.
This would be the best way to find out what is really going on during your possible fuel starvation when corning.
Keep the MFI.

[TR]

Hi
I have read a whole bunch of the posts now and have a better understanding of how the mfi pump works.

I also took the car out today for another drive. It purrs along in mid range and top end with out any apparent issues. Acceleration is quite awsome but with a 110 km speed limit its not ideal testing. It's been so long since I drove the damnd thing that I inadvertantly put it in a gear too high for the speed I'm travelling. That is just my stupidity. long legs in the 5 speed 901 box.
I checked all the linkages, they appear tight with little play. The micro switch to the shut off solenoid appears to be working. When coasting down hill fuel doesn't seem to be dumped into the motor, no back fire and only a little rummbling and minor popping when really slowing down for corners.

I can't tell if the cold start thermostate works correctly or not. Can it be shutting off too much?

The cold start thermostate came off the old 2.2 motor. I don't know how many disks there should be in there for the 2.7


I'm not going to touch anything at all untill I can get some info on the correct measurements for all the external components.

I need to write a dot point list of procedures and work out all the measurements for all the external components. I have found one shop that preps GT3's the guy said he has some experience with mfi. He's 250 miles from my house so its getting better.

The car will idle smoothly at about 600rpm with the throttle handle off. Is that about right?
Can I disconnect the shut off solenoid ? Is that a valid test to see if it could be the cause of the starvation?---Or will i get the massive fuel dump and back fire? Can that cause a fire? I thought this might be the issue?

Test equipment is on the cards --if i can sneek it past the wife--I'll be in the dog house soon.

Thanks for all the advice I am not as freaked out as last week when all I could see was a huge bill looming.

cheers

Terry

[tobluforu]

MFI should idle around 850; Measure the linkage that connects from the main rack down to the pump as it should be 114mm.
What kind of plugs are you running and what do they look like, is the car in good tune-new points adjusted properly, new cap and rotor, plug wires, valves adjusted, etc.. Does it have the heater hoses connected from the HE to the pump? Make sure the car in in perfect tune before you start futzing with the mfi-pump wise.

[TR]

Every thing new, built by a Porsche trained technician, had the new motor in storage for three years prior to fitting. The mechanic has since retired. The motor started first go after priming with fuel and oil. Every thing was set in the shop but the guy who built the engine has never seen it running as he move away after retiring.
the fact that it runs almost perfectly is a testament to how well he put it together on the stand.

I'll measure the rod in the morning .

thanks

Terry

[dicklague]

Terry,

You are getting a lot of great advice here. I know what you are up against, I have been down the same path. I have had my 2.7 1973 RS clone for 11 years and put over 100,000 miles on it. Did not do too much with the MFI in the beginning. I was afraid to mess with it. My mechanic had it running pretty well, so I did not touch it. With the help of this forum and the CMA I started to get more familiar and more confident in tuning.

Again the AFR was a real breakthrough. CMA refers to CO measurements and the use of an early, now very crude instrument and road testing. We are very lucky that we now have the wideband AFR sensors from Bosch and others that give us such great data. I am biased, but my research showed me that the Daytona Sensors Wego IV is the best value for the money. Retails for $440.00 USD from our site sponsor. Best thing is on a Porsche, the RPM portion is an easy one wire hookup. Also data logging is a must. You can log 2 hours of running data. I can't emphasize enough how valuable it is to be able to sit at your computer and analyze what happened on the run. It is just like a dyno run.

Here is a chart of a recent run of mine. This is a one minute slice.



This charting gives you the ability to see what happens as the engine warms up and runs under varying conditions. I know other AFR instruments will do charting, but I don't know of a package in the $400 range that includes data logging, software, Bosch wideband sensor, wiring, and extreme accuracy for this price.

You can also download all data on a spread sheet and read it that way.

Good luck with your MFI journey. There is lots of satisfaction when it all works well, and you know that you did it.

[dicklague]

Looking at your post had me looking at the MFI posts again, and I decided to recheck the linkage to the MFI pump. Not sure who the last one to check it was, but not me. It is supposed to be 114mm center to center. I removed the linkage and checked it several times and it was 111.7 which is of course a bit too small. I adjusted it to the 114 spec and retested the car on a 15 mile drive.

Idle is now spot on at 869 rather than too high, and the MFI stays nice and rich through the acceleration range, where is was a bit on the lean side before. Makes sense. The pump is more rich because of the longer rod.

I will tweek the idle mixture later.