Tuning MS2 Manual clarification

[Philip Lochner]

I require some clarification on the following paragraph from the MS2 tuning manual please:
 
"Once you have it started and running, let it warm-up fully, and note the injector pulse width at idle. Then you can reset the REQ_FUEL value back to its original number. It is very easy to change without having to re-enter the VE numbers. In MegaTune, go to 'Tables/VE Table 1/Tools/VE Specific/Reset ReqFuel' and enter your original and new REQ_FUEL values, make sure the 'Reset Req_Fuel in Constants' box is checked and click on OK. This adjusts the VE table and resets the Req_Fuel. "
 
1) What is the purpose of "note the injector  pulse width at idle"?  What am I supposed to do with the injector pw @ idle after I noted it?
2) "Then you can reset the REQ_FUEL value back to its original number": In the context of the text, Req fuel was changed to keep the engine from stalling.  WHY should I reset it back to the original number?  Is it because the VE table is incorrect and not the REQ_FUEL?
 
Thank you
Philip
MS-2/V3/2.35/MT2.25

Posted by email.

[Philip Lochner]

Thanks Lance
 
So, if I may rephrase in my own words:
 
1) I start with a best guess req_fuel value and VE table;
2) Once its running and warmed up I adjust req_fuel on the "Injection control" page (lower window) until I get a good idle and this "adjusted" req_fuel value is then what it really should be.  Now I note the idle pw;
3) But now the VE table is wrong, so I use the reset function on the Tables/VE page to change the req_fuel to this new "adjusted" value and recompute the new VE table;
4) after this the idle pw should be the same as noted above
 
Is this OK?
 
Kind regards
Philip Lochner

-----Original Message-----
From: lance [mailto:megasquirt@shaw.ca]



Phil,

The PW at idle is a generally useful bit of information, and if you note it you can verify that it is in fact the same after doing #2.

Yes, #2, both resets the req_fuel AND recomputes the VE table to match the correct req_fuel, so that you get the same PW as noted in #1.

If you don't get the same PW, then something has gone wrong...

Lance.

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[max@zl2max.gen.nz]

Well I am not much help to you, but I have always been confused by this as well.

I never bother about redoing the VE table, once I have required feul and idle, I just let autotune do its magic. As long as I don't get crazy figures in the VE table, I guess outside of 40-120 ( without looking ) I have been happy.

Works for me....

Max

[sebch]

Thanks Lance
 
So, if I may rephrase in my own words:
 
1) I start with a best guess req_fuel value and VE table;
2) Once its running and warmed up I adjust req_fuel on the "Injection control" page (lower window) until I get a good idle and this "adjusted" req_fuel value is then what it really should be.  Now I note the idle pw;
3) But now the VE table is wrong, so I use the reset function on the Tables/VE page to change the req_fuel to this new "adjusted" value and recompute the new VE table;
4) after this the idle pw should be the same as noted above

Philip,
I don't get it exactly the same way as you. Your 1) is definitely right. 2) is partially right, i.e. until the words "good idle". Then, IMHO, the Req_fuel you have come to type in in order to get the smooth idle (what you call the "adjusted" value) still is not the good one. The god one is always the one that MS computed for you in the first place. Now your req_is different from that (since you have altered it). But since your idle is good, you want MS to keep injecting exactly what it squirts with your adjusted value, BUT using the calculated value. In order to get this, you'll want to reset the req_fuel to the original (MS calculated) value and then adjust the VE table so it still squirts the same amount (eg. 2.5 ms, that's why you've taken a mental note of it). For example: your calculated req_fuel was 15.2. Then you fiddle a bit and find your idle is good at 14.2ms, wih a pulsewidth of say 5.4 ms. This means the VA values in the idling zone are a perfect match for 14.2. Now you want to use 15.2 anyway because it's the real optimal value. So you reenter manually 15.2 in the constant page. But then, your VE map is too rich and your pulses will be more than 5.4. So you need to scale your VE map from 14.2 to 15.2, in fact making the VE numbers smaller to accomodate the greater Req_fuel. In this, your 3) is exactly the opposite of what it should be! Then 4) is again correct: in my example, you should be back to 5.4 ms

Now guess what: I haven't done it and I think I should have! The option I chose was to act directly on the VE map to get a good idle. I'm still looking for it!!

Hope this helps, Séb

[Philip Lochner]

Thank you Seb
 
Your description has helped and I think its making more sense to me (I'm blond... :-) ) so let's check:
 
1) Start with a best guess req_fuel value and VE table (as computed by MT),
2) Note the req_fuel value;
3) Once it running and warmed up, adjust req_fuel on the "Injection control" page (lower window) until you get a good idle. Now note the idle pw;
4) But now, both the req_fuel and the VE table is wrong, to correct, use the reset function on the Tables/VE page to change both the req_fuel back to its original value AND to recompute the new VE table. Current ReqFuel Value will be the value you arrived at to get the good idle and New ReqFuel Value will be the original "best guess" value (which was changed in the process of getting it to start and getting a good idle);
5) after this the idle pw should be the same as noted in step 3

Is that it?
 
Kind regards
Philip Lochner
MS-2/V3/2.35/MT2.25
 

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[scottymk2]

hi there,
interesting post as i am also a bit confused about the same thing.

not meaning to hijack the thread, but i already have a well tuned VE table, from someone with an identical setup to me. i know this wont be exactly right, but it should be pretty close, at least to start with.

if i change and then reset my req-fuel, will it change the entire tuned-VE table, and make it incorrect? or alternatively, would it be possible to just change the values of the tuned VE table, around the idle point, manually?
surely this would avoid changing the whole table, but have the same effect as changing the req-fuel at idle?

cheers

scott

[Philip Lochner]

Hi Scott
 
I did not have confirmation to my previous post so at this time you must take what I say with a great deal of caution.  IF my understanding is right then:

if i change and then reset my req-fuel, will it change the entire tuned-VE table, and make it incorrect?  
PL: Your current VE map is based on your current Req_fuel setting and is delivering fuel based on the current Req_fuel setting.  Since it seems that your req_fuel setting is not what it should be, the map is making up for it, resulting in pulse widths that ARE right. So, using the reset function should?? then change the Req_fuel setting on the Injection control page AND should change the entire VE map but all of this should still result in the same pulse widths as before - over the entire map.  You can try it, just make SURE you have saved your current msq file in a very safe place so you can go back to it if needed.
 
 or alternatively, would it be possible to just change the values of the tuned VE table, around the idle point, manually? 
PL: It is certainly possible to change the values around the idle point and there are at least two ways of doing it a) on the VE table itself and b) under "tuning"  section on the 3d map.  (Just remember to "burn") But if I read your next sentence I get the impression you may not understand something (assuming of course that I do .... )
 
 surely this would avoid changing the whole table, but have the same effect as changing the req-fuel at idle? 
PL: Req_fuel does not affect only idle.  It is used for the ENTIRE map.  Look at the formula used for calculating pulse widths (see you should paid more attention to your maths at school :LOL: ) 
 
Again, I sincerely hope a true boffin will confirm what I wrote.
 
It seems to me you are not happy with idle.  If that's the case, I suggest you start a thread on how to achieve a good idle.  You will have at least one supporter, moi!!
 
Kind regards
Philip
MS2/2.35/V3/MT 2.25
 

Posted by email.

[scottymk2]

Thanks for the reply philip! i havent actually got the engine started yet.. but was just reading up in readiness!

so just to clarify -

i should tune the req fuel at idle even if it idles 'ok'.
then , i shoudl reset it using the above method, which will change the whole VE table..
the VE table i have is from someone elses identical, and good setup.
the values in the VE table will change but the fuel delievered will stay the same , therefore still giving me a good VE table?

i guess im just confused as to whether
A) i will still be left with a tuned VE table, or
B) whether re-setting req-fuel will render the table untuned, and i shoudl just change the idle values in the VE, manually.

im also confused as to why you need to change the req-fuel in the first place!

many thanks!
best regards

scott

[Philip Lochner]

Hi Scott

See my replies below. Again, keep in mind everything I say is based on my own and very first MS-II ECU experience (or should that be INexperience...)

just reading up in readiness!
PL: My approach too

i should tune the req fuel at idle even if it idles 'ok'.
PL: Careful, what is your definition of "OK"? OK idle is stable (not hunting), correct timing, enough air and correct AFR!!! This last item is what I THINK is the main reason for changing the req_fuel in the first place. I don't get a good idle if my mixture is not rich enough richer than 13.

then , i shoudl reset it using the above method, which will change the whole VE table..
PL: Yep, that's how I understand it. But the changed VE table SHOULD produce the SAME pulsewidths iow the engine should run the same under all conditions and loads.

the VE table i have is from someone elses identical, and good setup.
the values in the VE table will change but the fuel delievered will stay the same , therefore still giving me a good VE table?
PL: Yes

i guess im just confused as to whether
A) i will still be left with a tuned VE table, or
PL: You should therefore be left with a changed but tuned VE table

B) whether re-setting req-fuel will render the table untuned, and i shoudl just change the idle values in the VE, manually.
PL: This will only fix the idle values but will render the rest of the table useless

im also confused as to why you need to change the req-fuel in the first place!
PL: a) To determine the pulsewidth needed for a good idle and to see if you get the same pw AFTER resetting the req_fuel back to the value it should be and having changed the VE table in the process.

Clear as mud?

[scottymk2]

ok! it is making more sense now!!

i got a new vb921 (after i blew the last one) and got my engine started for the first time this evening, had to change the req fuel alot to get it going!

it is idling very rough, so i need to make a fair amount of adjustments/checks but i will be resetting the req-fuel as discussed, many thanks philip for your replies!!

best regards

scott

[Philip Lochner]

Like most newby's, I've been using 1ms as my injector opening time in the absence of accurate data on my injectors.
 
This morning I measured the injector opening time with my oscilloscope.  For a laugh (and possibly stern corrections...) I'll share HOW I did this.
 
I tried both methods of changing the number of squirts and the other method of using the EGO cross-over point but neither worked for me.  So I decided to do it the way I prefer anyway - measure with test equipment if possible.
 
I used the inductive pickup from a broken timing light and put this over one of the wires going to the injector.  I certainly did not see the waveform one would get with purpose made test equipment but I could clearly see a dip at 1.3ms where surely the pintle must hammer home in the open position and a dramatic rise where the injector closes.  Programming this in has, subjectively, improved things.
 
It seems to me that there are three parameters one must have REALLY close to correct - IF you want your msq file to be repeatable :
1) injector flow rate (which implies req_fuel) - this one I'm still guessing...
2) injector opening time 
3) base timing.
 
Kind regards
Philip
MS-2/V3/2.35/MT 2.25/Innovate LC-1/LSU4.2
Land Rover 4.6 std, 4-2-1 exhaust headers, IAC
'80 Jaguar XJS V12 5.3 (10:1 CR) is waiting for its turn

 

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