MFI self build pump setup and tuning

[BartdeBruijn]

Hi Jonny,

Thanks for gratulations, but to early….
Will tell you why(also in last part of my previous post)
With the 3000 rpm and full throttle I started at 58 CC. You stated in your earlier mail that this condition should be controlled by the rack screw so I did. I had to give it 9 clicks CW to reduce to get 55 (was not very responsive)
What I feared was that by using the rack screw I altered the earlier quantities. What was proven as after getting to 55 CC the 2000 rpm and 29.5 load was down to 19 CC instead of the earlier 24.5 CC.
Iread read somewhere (maybe from you) that each spring will generate a part of the total spring curve and the stiffness can be adjusted separately, however the whole curve can be shifted over the y-axes by using the rack……
If that is the case should I use the white screws for the 3000 rpm condition? (Something Mark suggested on PP) choice to go on two forums makes live bit complicated ��
I am a novice in this and just learning and like all the knowledge arround! Would never got so far if your thread wasn’t there!

Cheers,
Bart

[BartdeBruijn]

Hi Mark, Jonny and others,

I dare to say that it was a successful Sunday as I believe I cracked it ;-)
It is late now and I will write my findings and kind of protocol down coming days.
Happy and also a bit sad as it was big fun getting closer and starting to understand how it works.

Now I still have to build the engine I plan and will write down the spec list down in another thread.
That’s all for now, more later!

Cheers,
Bart

[2.5MFI]

Great work Bart. Glad you're going to post your engine specs too.

[BartdeBruijn]

Part 4

Hi!
As already mentioned in the last mail, I finally calibrated my MFI pump ;-)
I will try to write down my experiences and learnings.

First I would like to thank the forum and in particular Mark Jung from MFIwerks and Jonny for there support and input they were a great help in this jungle of springs, screws and CC’s…..
Below is just my experience based on the very first steps in this field and everyone is more than welcome to comment!

Anyway I focussed to get the following settings correct.

Rpm load rack CC’s time/1000cycles adjust
1) 2000 full 7.0 47.0-48.5 0:30 rack
2) 400 0 4.45 13.5-14.5 2:30 idle
3) 800 8.3 4.25 14.0-15.0 1:15 black
4) 2000 29.5 4.75 24.0-25.0 0:30 white
5) 3000 full 7.3 52.0-54.0 0:20 white

For 1) focus on quantity and equal over cilinders

First I put a lot of energy to get the rack displacement correct, however later on, you realize that CC’s are the dominating factor to get right. Yes they are connected but the focus and attention should go in my opinion to the fuel quantities.

When I, after a lot of runs, got everything correct from test 1-4 test5 (3000/full) gave to much CC. Changing the white screws would automatically influence the 2000/29.5 test. When I started adjusting the white screws for test 5, I felt that they where way less (not) responsive (influencing the rack movement) as in test 4. One should realize that all the springs behind the capsule are pretensioned by the different screws and all interact. So it can be seen as a graph where 3 spring stiffnesses who are connected/interacting. Each spring has a certain stiffness range being controlled by pretensioning the screws (idle = idle, mid rand = black and high range = white). This all will influence the movement of the rack through the flyweight assembly that is influenced/restricted by these different springs. (Maybe I should draw this graph (has been done before in the forum….) the rack screw will move this 3-spring graph up or down in total!
Found it, a graph explains it better [Graph from JCGE] Interesting read anyway:

http://forums.pelicanparts.com/porsc...surgery-7.html

So back to my issue on the high volumes in test 5. The only solution I saw was moving the graph down by adjusting the rack and consequently using the different spring screws to correct quantities again after the rack adjustment, remember the rack adjustment influences the whole rev range.
.
Something else I learned, at least it worked for me is starting with test 5 and than working your way down. Reason seems that the spring differences are big, so when the highest stiffness spring is adjusted correctly(white screws) it will have little influence on the less stiffer spring (black screws) etc. The other way around that if you adjust the black ones correct for 800/8.3 and you have to adjust the white screw later these will have an impact one the earlier setting (800/8.3)

In the end it will be a bit back and forth and double check but as Jonny already said if you get it right because you understand the internals the satisfaction is sweet!

Another observation is that if one cilinder is on the low side of the range in one test, in another test it can be another cilinder. (By the way I have 6 new injectors tested with the injector tester from: https://mercedessource.com/store/mfi...s-demand-video

So these are my vallues

Rpm load rack 1 2 3 4 5 6 must
400 0 4.23 14.0 14.0 13.5 14.0 14.5 14.5 13.5-14.5
800 8.3 4.04 15.0 14.5 14.5 15.0 15.0 15.0 14-15
2000 29.5 4.51 25.5 25.0 25.0 25.0 25.0 25.0 24-25
3000 full 7.09 52.5 52.5 52.5 52.5 52.0 52.5 52-54

Here a run at 3000 pump rpms and full load……pretty impressive if you stand that close! https://youtu.be/VIkHr7-ULH0

Some fine tuning can be done but I guess when I finished my new engine build (will be another thread) I will mount a LM-1 and see what is really going on!

I also added a picture of a few of the notes I made to get it all right.

That’s all for now!
Cheers,
Bart

P.s. I have no idea how to get the tables well alligned (They look good in the editing box but not in the preview)

[2.5MFI]

Bart, You have accomplished an awful lot of work on this project. Excellent write up Bart. Im fairly sure you have just about mastered the MFI pump adjustments. Using the LM-1 when you get your engine done will open up a few more adjustments may be needed. Great work.

[BartdeBruijn]

Thanks Mark,

As said it is big fun when you start understanding the ‘internals’

Engine spec will follow this weeknd and is more then open to discussion ;-)

Cheers,
Bart