MFI self build pump setup and tuning

[Rick Cabell]

You guys should consider going in the pump rebuilding business. Decent money and all who do it as a business are booked way in advance. Consider it a side hobby.

[Jonny042]

You guys should consider going in the pump rebuilding business. Decent money and all who do it as a business are booked way in advance. Consider it a side hobby.

I do take on the odd job for other Canadians who are hesitant to ship their pumps across the border. It's been very rewarding helping a few people get their cars running better. It is pretty time consuming, however, and difficult to charge for the actual amount of time spent.

As for the practicality of DIY'ing a calibration setup like shown in this thread, Eisenbrandt in Germany have released their 2023 price list and a pump rebuild is 4,558 Euros. If you don't want to wait you can buy a pump outright from them for around 10,000.00.

[BartdeBruijn]

Just to add - I think the "Bosch Data" in the book has been transposed and interpreted to some degree in the book - there is a lot of duplication in the sheet, for instance the conditions in test (A) are revisited in test (C). It's not particularly well presented or explained. And at a glance it appears more complicated than it is.

Since you had your pump completely apart the fuel delivery settings for the individual cylinders would need to be set with the adjusting collars so they are not only even, but have the specified fuel delivery at, say, 7.00mm rack movement. Once that is accomplished you can ignore test A and go onto test C, really, and only do the 3 tests that are shaded/highlighted and add a max throttle 3000RPM test and be done!

So here's a summary -

1. Spin the pump at 2000RPM/Full throttle and adjust the main rack screw so that you are getting 7.00mm travel. Set all your cylinders to pump 47-48.5 ml/1000. Get them as even as possible as this is your only chance to set the individual cylinder "trim".

2. Do four tests:

400RPM/Closed throttle (adjust the idle screw)
800RPM/8.3 deg throttle (adjust the black screws)
2000RPM/29.5 degree throttle (adjust the white screws)
3000RPM/Full throttle (adjust the main rack)

3. Repeat the tests in step two until the settings are correct.

It's not actually necessary to do full timed volumetric tests for each test, the dial indicator on the main rack can be used to get a relative measurement as soon as the pump is up to speed and this can be a help to get in the ballpark by looking at the rack movement instead of going through a full volumetric test.

Looking at the Bosch Data for the 2.4S it looks like there's some issue with the co-relation between the rack movement specs and delivery rates so take anything on those spec sheets with a grain of salt!

Hi Jonny,

Thanks for the valuable info. I received the original Bosch datasheet today and the values are all the same, however I agree that they do look odd if you try to find some logic in them. I will also focus on the steps you mention and see how far I get. Understanding you correctly the rack screw will rase the whole curve and the capsule screws will alter the shape of this curve.

If you start such a journey you are looking for the logic behind and this support helps a lot. Funny part is that first time revving pump to 2000 rpm is quite something. Now I am used to it but the next one is 3000 rpms…..if you think about it kinetic energy wise, however I never heard about a MFI pump exploding so will be fine ;-)

Will be continued and posted in a few days as I am fairly busy at the moment!
Bart

[BartdeBruijn]

You guys should consider going in the pump rebuilding business. Decent money and all who do it as a business are booked way in advance. Consider it a side hobby.

Hi Rick,

I am not at that level for sure, however it is big fun to understand this great piece of mechanical engineering! I have always been intrigued by the MFI and when I finished my 911T from ‘69 after 20 year restoration also the fun discussions with the in depth Porsche guys stopped. Now building this engine etc. Will open up this opportunity again where you see a part in this thread! Will be continued

[Rick Cabell]

I’ll be watching

[Jonny042]

If you start such a journey you are looking for the logic behind and this support helps a lot. Funny part is that first time revving pump to 2000 rpm is quite something. Now I am used to it but the next one is 3000 rpms…..if you think about it kinetic energy wise, however I never heard about a MFI pump exploding so will be fine ;-)

It's amazing how "busy" the pump and injection system are at 3000RPM (6000RPM engine speed!). Here's a video from my youtube channel of a 3000RPM test:

https://youtu.be/PpPtxS3-Xn8

[BartdeBruijn]

Just to add - I think the "Bosch Data" in the book has been transposed and interpreted to some degree in the book - there is a lot of duplication in the sheet, for instance the conditions in test (A) are revisited in test (C). It's not particularly well presented or explained. And at a glance it appears more complicated than it is.

Since you had your pump completely apart the fuel delivery settings for the individual cylinders would need to be set with the adjusting collars so they are not only even, but have the specified fuel delivery at, say, 7.00mm rack movement. Once that is accomplished you can ignore test A and go onto test C, really, and only do the 3 tests that are shaded/highlighted and add a max throttle 3000RPM test and be done!

So here's a summary -

1. Spin the pump at 2000RPM/Full throttle and adjust the main rack screw so that you are getting 7.00mm travel. Set all your cylinders to pump 47-48.5 ml/1000. Get them as even as possible as this is your only chance to set the individual cylinder "trim".

2. Do four tests:

400RPM/Closed throttle (adjust the idle screw)
800RPM/8.3 deg throttle (adjust the black screws)
2000RPM/29.5 degree throttle (adjust the white screws)
3000RPM/Full throttle (adjust the main rack)

3. Repeat the tests in step two until the settings are correct.

It's not actually necessary to do full timed volumetric tests for each test, the dial indicator on the main rack can be used to get a relative measurement as soon as the pump is up to speed and this can be a help to get in the ballpark by looking at the rack movement instead of going through a full volumetric test.

Looking at the Bosch Data for the 2.4S it looks like there's some issue with the co-relation between the rack movement specs and delivery rates so take anything on those spec sheets with a grain of salt!

Hi Jonny,

I had question left on your summary.

I just did test 1 (run 2000 rpms at full load resulting in rack travel of precisely 7.01 mm.
Fuel quantities are with this run the following
Cil
1. 49.5
2. 48.0
3. 48.5
4. 48.5
5. 49.0
6. 49.0

So my question is do I adjust the values to get them closer between the needed 47.0-48.5 by turning the rack head screw to get the whole range a bit down and than equalize them through the 6 separate piston/rack clamp screws? Or do I leave the rack head screw and I lower each separate cilinder quantity by adjusting 6 separate piston/rack clamp screws?

For step 2 it seems clear as the cilinders are already equalized the adjustments go through the different screws, right!?
Hope my question is clear?

Thanks,
Bart

[Jonny042]

You could do it either way, and at the end of it all it will make no difference - although I would probably leave the rack setting as is and adjust the individual cylinders as close to 48.5 as possible - that way you can leave two of them alone!

[BartdeBruijn]

Part 3

Finally found some time this weekend to work on my pump.

Taking Jonny’a advise I started with
2000 rpm full throttle position
After some tweeking the clamps/collars on the main rack the results were:

Rack movement 7.02 mm.
Cylinder 1 2 3 4 5 6
CC. 48.5 48.5 48.5 48 48.5 48.5 [47 -48.5]
So check, that one is ok!

Now moving on to the next 4 tests
400 rpm; 0 load; run time 2:30
Cylinder 1 2 3 4 5 6
CC. 14 13.5 13.5 14 14.5 14 [13.5 - 14.5]
OK too!

800 rpm; 8.3 load; run time 1:15
Cylinder 1 2 3 4 5 6
CC. 15 14.5 14.5 15 15 15 [14 - 15]
OK too!

2000 rpm; 29.5 load; run time 30
Cylinder 1 2 3 4 5 6
CC. 25 24 24.5 24 24.5 24.5 [24 - 25]
OK too!


3000 rpm; full load; run time 0:20
Cylinder 1 2 3 4 5 6
CC. 54 54 54.5 54.5 55 55 [48.5 - 50]
NOK. I had to turn the rack 10 clicks CW (Less rack travel) but seem s to react slowly and only moved +/- 3CC by 10 clicks. I can go further of course to get to the 48.5 - 50 range, however I was afraid that I ruined the earlier settings…..
I did a check after this 3000 rpm full load exercise by redo the 2000rpm and 29.5 load. this resulted not in the earlier tuned 24.5 ‘ish CC but in 20’ish. This sounds logic as I turned the rack to achieve the 3000 rpm and full load volumes…..
So I am running in circles somehow!

I was pretty happy till the last bit. Is this me not understanding the system or drill!?
Thanks,
Bart

[Jonny042]

Bart, your 3000RPM full throttle spec on the sheet is 52.0-54.0 isn't it? In which case I will congratulate you on getting your pump calibrated!!! 55 is close enough IMO.

You'll want to install a wideband Air/fuel ration monitor on the car to get the pump truly tuned to your engine but you have a great starting point.