Staged Injection
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Here is my first attempt at modifying the MPI inlet manifold I am using to utilise a secondary set of injectors, for staged injection, once I have my Turbo charged engine.
New injector bosses have been welded on the existing MPI manifold, these are on the outside of the inlet tract, which points the injectors at the inner wall of the inlet tract.







The angle of the bosses from the inlet tract is greater than I would have like, but this was done to accommodate the larger bodied 42Lbs/hr hour injectors that I am currently running. (That said I over did the angle a bit from what I had planned.)
The pictures show the thinner 63 Lbs/ hr Seimens injectors installed, which I have planned for use with the turbo engine.
The plan was to run the smaller primary injectors in the new bosses and the larger secondary injectors in the original MPI injector bosses.
The outcome with running the 42Lbs /hr injectors in the new bosses was disappointing, but not entirely unexpected.
I had to move Inj timing 2 to -95degs at tick over, this from the -35deg being run when the injectors are located in the central bosses. Additionally, I needed to increase the Inj 1 VE table values by 30 points over Inj VE table 2.
Even then tickover was fairly rough and the AFR’s “floated” around 14.5 on both inners and outers.

My next step is to try the 63 Lbs/hr injectors in the new bosses and see what difference they make to tickover, although I’m guessing with the injectors at the angle they are, I’m squirting the fuel directly across the tract and onto the opposing wall.
I’m not expecting this to make much difference, but as it only involves swapping 4 wires around, I’ll try this before removing the inlet manifold again to work out whether I can in fact reduce the boss angle and install injectors on the inner side of the inlet tract.

I the meantime, I’m working through setting up the Megasquirt on the JimStim for staged injection…

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The angle of the second ones is a lot worse than I was expecting from your previous descriptions but they are in approximately the same location (which I wasn't expecting) so transit times should be similar.

The change of AFRs at idle with your previous settings could be down to the fact there is little mixing of the fuel and air as the air velocities are so low, hence the direction of the injector becomes more important..... Have you run it up through the RPM / load range on the original settings on just the angled injectors to see if it reverts back to its previous AFRs on just the angled injectors at high loads ???

If not - and you're obviously the first to try this - it might be Paul's proposal of three injectors (the additional two being equal and opposite sides so cancelling direction out) is the only solution.

I hope not because I intend to try two only (but at much shallower angles).

Schrödinger's cat - so which one am I ???

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As per the above post, here is a part of the log taken.



Max RPM I was able to get was 3817.
I tried changes to both injection timing 2 and increasing Fuel VE Table 1, using the base of -95 for inj timing 2 and Fuel VE table 1 being 30 points higher than Fuel VE table 2. This is as per the settings I used to get a “fairly good” tickover. Although it reduced the AFR variation, I was still 2 – 3 points out.
So I think this is a no go…
If my understanding of staged injection is correct from the limited testing I have done on the jimStim, the secondary injectors use the same injection timing tables as the Primary’s, so Injector timing tables 1 & 2. So, If I could get the engine running well with the angled injectors, my secondary staged injectors would be running the same Injection angles, which would not be good…
The below plot is using a set of 63Lbs/hr in the original MPI bosses and the good Megasquirt settings for the 42 Lbs/ Hr injectors.



Although it’s running very rich, the AFR variation between inner and outer cylinders is fairly minimal, infact around the same as I get when running the 42Lbs/ hr injectors in the MPI bosses.

I’m working on bringing these AFR’s up to an acceptable level now so that I have a basis to work from when I actual get to staging, that’s after I work out how to squeeze in the secondary injectors…

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Graham,

You're correct that the same timing tables are used with staging on or off. The idea was that you would have values where staging is brought on which would provide good results but would be different from what you would need from either set of injectors.

If that is too big of a constraint for a lot of setups then that might need to be revisited in the code. However in this case, I'm not sure that having different timing for primary and secondary injectors would change much since it doesn't look like you can get back to a good AFR distribution with the side injectors.

What kind of spray pattern do these injectors have? I'm just wondering if there is too much contribution from wall wetting in the fueling which would make timing somewhat almost irrelevant. Maybe injectors which can provide finer droplets would make this geometry more usable.

Jean

http://www.jbperf.com/

The 42 Lbs/ hr injectors I am using are these:
http://www.racetronix.biz/itemdesc.asp?ic=01D030x&eq=&Tp=
The only info on the link is that they are TRI-Cone. What the cone angle is I am not sure.

I think though for now, I’m going to measure up and see if I can get another set of bosses installed on the top of the inlet tract, just in front (head side) of the standard MPI bosses. It looks like it might be doable, considering the injectors sit fairly well back in the MPI bosses. If it can be done, I think I will be restricted to using the slim bodied Siemens injectors, to get as small an angle as possible to the inlet tract.

With regard to setting the megasquirt for staged injection using the sequential Siamese setup, what are the basis settings? And how are the pulse widths calculated once staging is activated?

I have been testing staging on the JimStim and get injection banks 1 and 2 operating correctly, with banks 3 & 4 coming in by using RPM as the first parameter. Once the staging is active, pulse widths on banks 1 & 2 drop, and pulse widths on all 4 banks are identical, then once I drop below the staging threshold, banks 3 & 4 drop to 0msec and banks 1 & 2 return to their normal operating pulse widths.
Once in the car, things go a bit wrong: once the staging threshold is reached, I believe injectors are cutting out. Tunerstudio shows the pulse widths of banks 1 and 2 drop to zero and no pulse width on banks 3 and 4. Once the revs drop below the staging threshold, banks 1 and 2 activate again. Could this be a wiring issue?
On the JimSTim, if I try setting staged injection with the staged injection table as the first parameter, banks 1 and 2 are fine up until the staging threshold, then once over the threshold, pulse widths on banks 2, 3 and 4 become identical (but lower) and bank 1 remains as would be if staging is not active.
I’ve not tried this in the car yet.
I’m sure it’s a setting, but not sure what setting.

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Staging should behave as described in your first test on the JimStim. Pulse widths should be the same for all 4 channels only if you have the same VE in tables 1 and 2 (or if you only use table 3). The pulse width will simply be scaled with respect to the injector sizes: if you have the same size for primary and secondary then the pulse width will be halved, if the secondary are twice as big the pulse width will be divided by 3 and so forth (ratio of primary over primary+secondary). Of course this scaling is done only on the effective pulse width which doesn't include the dead time (opening time).

What you see on the car looks like a configuration issue because I don't see how a wiring issue would make channels 1 and 2 go to a 0 pulse width. Are you sure you don't have some rev limiter set? Can you post your msq?

As for the staged injection table, this is a relatively new option that was back ported from MS3 and it is possible that it's not compatible with the siamese code. I haven't looked at it and looked at how this is implemented in the code so it is possible that I will need to change a few things to make it work. What you describe as the behaviour is not correct.

The staged injection table is to allow staging to be done partially depending on RPM and load. You can decide to bring on the secondary injectors gradually from 0 to 100% where 100% is the fully staged setup with both injectors running the same pulse width and 0% is staging off. This is more useful for engines with secondary throttle bodies or widely different injector placements and I don't think it will be useful with the siamese-port engine but it should still work as intended.

Jean

http://www.jbperf.com/

Hopefully the MSQ is attached...

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http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

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After a bit of testing with the megasquirt on the JimStim, I’ve recreated the problem I was seeing on the car when I first tried setting staged injection.
I appears that I never power cycled the Megasquirt after making changes to either the staged injection settings or turning on injector banks 3 and 4 in the sequential injection settings window.
That problem sorted, I now have the car running on staged injection.
I over cooked the amount of timing advance required with staging active, so I actually have the inner cylinders running leaner than the outer cylinders.
The staging was set to come in at 2000rpm, with no second staging parameter set.


I’ve now changed the settings to 3000rpm for the first staging parameter AND 75KPa for the second staging parameter. No run done as yet with these settings.

For the time being, I’ve left the secondary injector bosses as is. Time is against me at the moment, so I’m hoping to get another MPI manifold. This way I can take my time on getting the secondary injector bosses in a better position / angle without having to worry about getting the car back together and running at the end of each day.

’77 Clubman build thread
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

Siamese 5 port EFI testing
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=611675

It's a bit difficult to read the scales and legend on that plot but it looks like you're gaining (ie, going week) by 2.5AFR on the inners when staging cuts in.

That sort of implies from a crude mechanical view that the second injector is bouncing its fuel off the innerwall of the manifold and aiming it at the outer cylinder. If so, I doubt you'll correct it with timing.

But the yellow trace confuses me - if its INJ timing outer (I think that's what I can read) then there must surely be an error on the bottom row of your timing table as it swings wildly when MAP hits near zero on a gearchange ???

Also you need some more AE at low RPMs (first active part of the log).

Schrödinger's cat - so which one am I ???

’77 Clubman build thread
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Siamese 5 port EFI testing
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Schrödinger's cat - so which one am I ???

This is a slightly out of date version, but I already had it in photo bucketeThere are Just a few differences to the actual table I'm using now, but I think it should make things clearer.

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I"m sorry I didn't get back to you before or have a look at the msq. But you seem to have solved the issue.

As for the timing table, I'm really surprised you need to do this but if it works then it should be fine. The low pressure will be evaporating more of the fuel already on the walls so that will skew fueling but I would have thought that would have been taken care of in the fuel tables and not the timing table.

Also, with staging, you will likely want to have some sort of discontinuity in your timing table at the point where you turn staging on. Granted there aren't many points in the table but if you can have a column just before the switching point and one just at the switching point then you could play with the staged and unstaged timing relatively independently.

Jean

http://www.jbperf.com/

Jean, I’ve just found that problem…

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Not withstanding Jean's comments above, I'm really surprised the four bottom right cells work for your fuelling.

Obviously it's what I saw on the yellow trace and if it works, I just don't understand why.

But you are he first on this (staged siamese) so keep it going.....

Schrödinger's cat - so which one am I ???

Did you really get resets or were those error messages? If the fuel pump output turns on and off every second and RPM goes to 65535 then this is a configuration error.

You can read the error message by opening the mini term window in TS and cycling the power. The error message will be written in the mini term window and should tell you what the problem is.

Jean

http://www.jbperf.com/

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The reset error was to do with not having staging gradual transition turned on. Specifically no staging transition events, which you can only specify by turning on the staging gradual transition option.

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Well that's looking a lot better.

Apart from just after the last gear change (which I don't understand) the other deviations are (1) at the staged transition which could just need a little more work on the table as per Jean's suggestion and (2) at the gearchanges which seems AE/wall wetting related so should be possible to dial out with the AE settings. That last one though (the lean spikes on the inners shortly after the final gear change) doesn't make sense yet....

Schrödinger's cat - so which one am I ???

Could that deviation at the last gear change be anything to do with the lower speed of acceleration of the engine once in 4th gear? The engine is taking longer to go through the staging transition.

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Schrödinger's cat - so which one am I ???

I've just changed the Hysteresis on the staging to 1rpm and set the last "unstaged columns" in injection timing and fuel VE tables to 2999rpm, with staging coming in at 3000rpm. Although it's on a relatively cold engine, 60deg (about 103WUE%) the inner cylinder lean out is gone. It was enough to cause a stutter as the engine went through the Staging Transition - even when under warm up enrichment. That stutter is now gone.
I'll test properly later.

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Just a quick update on this...

I eventually found that I could not tune out the lean spikes on the inners after gear change, when using Injection timing to balance AFR's. There was a fairly radical shift necessary of 55deg for injection timing 2 (advancing from -35 to -85) once the staged injectors activated.
So I changed to fixing the injection timing to 0 for injection timing 1 and -30 for injection timing 2 ( these being the best figures I found for tick over) and used 2 Fuel VE fuel tables, balancing AFR by offsetting the cells between the 2 tables. This actual gave very good results with staging inactive. However with staging active, I ended up with a massive difference in figures between the two tables. For example: In the 4300rpm/ 100Kpa cell, fuel VE table 1 was set at 200 and in fuel VE table 2 it was set to 69. Although I got the AFR's matching, I could not get lower than 15.4AFR, above 3000RPM and from approx. 75KPa up.

So, at the moment the staged injection testing is on hold, until I sort out the position of the stage injectors.

I have finally source another MPI manifold and started looking at how I can fit the injectors in.
There's just enough room behind/ under the primary injectors, but this will mean removing the standard MPI fuel rail and making a bespoke fuel rail.




Mounted like this the nozzle of the staged injector will be approx 30mm further back the inlet tract than the Primary injector nozzle. However, it is a bit further out of the airflow than I had hoped.
The primary Injectors will be the Siemens deka 63Lbs/ hr injectors, 26deg cone spray pattern, which I am currently using in the 998 NA and the eventual staged injectors will be the Siemens Deka 4 80Lbs/hr injector, pencil spray pattern.

Before I go ahead and start butchering another Inlet manifold I have 2 questions:
Because the staged injectors are Pencil spray pattern , would this offset the fact that they are mounted some 30mm further back than the primary injectors? (in relation to transit times)
And would the fact that they are so far out of the airflow be a problem?

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I can't answer your questions as I have never tried staged injection.

However, I would suggest using the same spray pattern on each of the injectors and setting them the same distance from the valve, even if it means shifting the primaries back a bit.

I still think that you are using too many variables in your setup to get an understanding of what is going on. Two VE tables and two injection timing tables is four times the chance of getting it wrong.

What we need is a "Secondary Injection Timing" table as MS3. Also a graduated transition, again an MS3 feature, would be a real boon.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."