Sequential Siamese mode questions

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Sequential Siamese mode questions

Postby Graham T » Wed Oct 28, 2015 2:25 pm

Jean,
It’s probably a bit late in the day now to be trying to understand some of the basics, but can you give me some clarification on the below from your “sequential Injection Code for MS2” documentation.

“…The effecitve pulse in mid-pulse mode is the injection pulse without the opening time. This means that if the pulse width is 5ms and the opening time is 1ms, the injection pulse will start 3ms before the injection timing point and end 2ms after…”


I’m sure this is simple but I’m being a little slow here, I’m not making too much sense of it at the moment and I’m trying to work out the actually beginning and end of my pulses in engine degree’s to make sure that I am not overlapping pulses between inner and outer cylinders.
My best power run to date was on primary injectors only and it was at 29.3% duty cycle, producing 161HP.
I had really not expected to be anywhere near that sort of power, hence why I had not yet set staging.
Anyhow, that duty cycle % is way too high, and I’m sure I had pulses overlapping at that point, so I want to work out a formula to show when I have, or am getting near any overlap, as obviously that will affect how I change the timing.

So, I have an injector opening time of 1ms
At 5684RPM (peak power), I have a pulse width of 6.182ms
So understanding your above, that means I have an effective pulse width of 5.182ms
Timing figure for both injection events is set at 0, so the effective pulse width would start at 5.182/2 ms before 0degs and end at 5.182/2 ms after 0 degs.
Or starting at +88.36 Deg and ending at -88.36 Deg (if I have my calculations correct)
However, because the opening time now has to be added, the pulse would actually start at (5.182/2)ms + 1ms before 0 degrees, but still end at 5.182/2ms after 0 Degrees?
So that would equate to:
88.36 + 34.1 = +122.47 Deg and ending at -88.36Deg

So ultimately:
Take the opening time off of the pulse width to get the effective pulse width
start of pulse is then half the effective pulse width plus opening time before the timing value
End of pulse is half the effective pulse width after the timing value?

Can you confirm I have my thinking straight?
Thanks
Graham

edit: Changed thread title
Last edited by Graham T on Sat Nov 07, 2015 8:50 am, edited 1 time in total.
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Re: Undertanding mid-pulse mode with siamese-port timing

Postby jbelanger » Wed Oct 28, 2015 4:42 pm

Graham,

That's correct and I get the same numbers from my own computations.

However, it might be simpler to use the end-of-pulse mode. This way, you only have to compute the timing for the beginning of the outer cylinder pulse and then make sure this is less than the inner cylinder timing (taking into account the 180 degree split due to the base sequential injection split). You will also want to have some margin to make sure the injector can open and close and remain in the linear region.

You already have the pulse duration in degrees: 210.83. That means you need at least 30.83 degrees more timing for the inner cylinders just to avoid overlap. You should probably get around 2ms of margin to start to be in the linear region so that means an additional 68.21 degrees. So you should have at least 100 degrees more advance for the inner cylinders. More margin would likely be better depending on your injectors.

And I agree with you, seeing a pulse duration of more than 180 degrees means you are really pushing the limit and you're probably over it. You're at 58.5% duty cycle (remember you have 2 pulses per injector). Paul has mentioned 40%; I don't know how much margin he was adding but that certainly would make sense to cover any inaccuracy in the timing tune, the actual timing and any impact from external parameters (temp, baro, acceleration,...).

So you should keep a close eye on your AFR with this setup. I assume you will update it to get more fueling capacity in the near future.

Jean
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Re: Undertanding mid-pulse mode with siamese-port timing

Postby Graham T » Thu Oct 29, 2015 5:05 am

Thanks for the confirmation Jean.
I’d also calculated that I was getting around 30Deg overlap, but that 1ms, or 34deg makes a big difference in our injection window, hence the need for clarification.

Putting that into my spreadsheet with the data from the power run shows that there was actually overlap on the pulses from ~4847RPM on up. It Maybe coincidence, but that’s actually the point that the torque starts to drop off.
It’s also the point that AFR’s between inner and outer Cylinders started to diverge. At this point (start of pulse overlap) I had 11.1AFR inners and 11.2AFR outers, steadily separating to 11.7AFR on the inners and 10.8AFR on the outers at max power.
That may not seem a lot, but I had seen earlier on in the dyno session that a 0.4AFR increase dropped me 3HP at around 3700RPM, 12PSI boost, so that rich state on the Outers probably did not help the max power, as the lean state on the Inners will not help when we get to the next dyno session to sort the ignition timing.
So advancing the Inner injection timing is a must.
I had always worked on 40% duty cycle as my max, but never thought to also add a margin, instead giving myself exactly 180Deg injection window as max target.
Also, I agree with changing to the end of pulse timing. In my original project car, 998cc NA, I started with end of pulse timing, but was persuaded to move to mid-pulse.
I have 875cc/min primary and secondary injectors, so once I get staged injection working, I should have plenty of capacity without getting anywhere near any pulse overlap.

I’m still trying to work out a regime for the staging as my only attempt on this engine saw a gross over rich state as gradual staging cut in – the primary injects continued on the same pulse width as the secondary’s gradually increased in pulse width, hence the over fuelling. I’d imagined the primary pulse width would reduce in line with the secondary pulse width increasing, hence keeping a stable mixture, but I probably got something wrong with my settings.
Once staging was fully on, mixture was perfect.

Currently, I’m mid-way through changing out my airfilter for 2 reasons:
The original filter used to date was a foam ITG, which was open in the engine bay.
At the dyno session it was pulling air directly from the engine bay and as a result IAT was around 50DegC. Obviously losing me the ability to set ignition advance and presumably losing me power due to less fuelling.
Secondly, all the data shows that at higher revs/boost, there was actually a drop in pressure at the air filter, perhaps indicating that the foam filter was impeding airflow.
Hence I’m now constructing an airbox around a K&N filter with hopes to alleviate both issues.
Lots more to do with tuning , once I sort out a few fundamental issues, but the more I look at the data, the more I am sure I can actually safely get more out of the engine for the boost/ rpm levels I’m at.
As stated, ignition is not set, so I am what I believe, and the dyno operator also confirmed, well below what I could have for maximum advance once the IAT is sorted and I get injection timing and staged injection sorted.
Also, boost for the power run was at 15.5PSI, and we saw a 5HP increase for every 1PSI of boost, so with a target of 19PSI, it should be looking good for a lot more power.
Just to put perspective on the figures, this is a 1310cc A series Turbo’d engine, Dyno’d at 161Hp / 163Lbs/ft so far.
Anyhow, thanks again jean. Appreciate your help thus far.

Graham
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Re: Undertanding mid-pulse mode with siamese-port timing

Postby jbelanger » Fri Oct 30, 2015 12:51 pm

Graham,

What is your power target? I ask because it seems to me that having 875cc/min injectors for both primary and secondary might be a bit overkill. I would think that having a somewhat smaller primary (around 500cc/min?) would make it easier to tune at low RPM and load.

Of course if you want to go significantly higher in power than what you have right now, you might well need both 875cc/min injectors if you want to stay below 40% duty cycle.

Another question I have is the AFR you're seeing. Do you need such a rich mixture to get the power or are you being cautious? I would think that with well matched inner and outer AFR you could optimise those a bit and still be safe. That would also give you some more margin on injector capacity and duty cycle. Of course, that depends on your setup but if you can get a cooler IAT I think that a slightly leaner mixture should work. And both should give you more power.

In any case, I look forward to seeing more results from you.

Jean
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Re: Undertanding mid-pulse mode with siamese-port timing

Postby Graham T » Sat Oct 31, 2015 5:24 am

Jean,
My target is 200HP, or maybe a shade over that.
I’m going to be trying smaller primary injectors, but for a slightly different reason than controllability…
I have an oddity with the injection timing I use below 2900RPM, but that I believe is down to my manifold design. I have to run the injection timing for the outer cylinders at -180deg, so basically I am sharing part of the outer cylinder pulse with the inner cylinders. This I suspect is down to the 7deg angle that I have the injectors in the runner, so they are biased to the outer cylinder. The 7deg angle in the runner was needed to ensure I could get both injectors in the runner side by side, but I think my measuring was slightly off and I have over cooked the angle, or more specifically I have mounted the injectors too close to the head, so the fuel stream maybe hitting the valve throat, rather than the back of the head port where the inner and outer valve throats split. (if that makes sense??)


Image


The original injectors I bought for the project were 640cc/min and 857cc/min, which I calculated at the time (many years back now) would be sufficient.
The 640cc/min have 26deg spray pattern and the 875cc/min have a 15deg spray pattern.
I’m hoping that the 26deg spray pattern will help overcome the injector direction a little so that I can bring the outer cylinder pulse back around and not need to share it with the inner cylinder.
Although I can get good AFR distribution at the lower Rev/s, the engine just does not feel as good as it could low down, perhaps because the fuel for the inner cylinder is pooling on the valve for nearly a full revolution of the engine, so I have a bad mix/ atomisation??
Once I get over 2900rpm, the whole engine comes alive and injector angle alters significantly, almost like the air speed in the runner overcomes my design flaw.
I just have concerns over how those different spray patterns will affect injection timing once staging is on, hence again I’m trying, if possible to use the same primary and secondary injectors to take some of the variables out of the mix.

I’m not sure, but I think a total of 1515cc/min is still going to be a bit tight to achieve my target as that would rely on hitting the injection window perfectly to make full use of the 40% duty cycle I have, without room for any margin.
Hence I decided on the 2 x 875cc/min injectors per port to make sure I had plenty of capacity.
So far, running the 875cc/min injectors has not caused too much of a problem with controllability at low revs/load or tickover, nonetheless, I will give the smaller injectors a try.

AFR’s are also in my opinion too high. I relied on the dyno technician for fine tuning and as he is an A series expert, went with what he felt was right.
Of course, with the inherent charge robbing issues, he has done the right thing in making the mixture richer to compensate for the perceived leaner mixture on the outers, and I guess part of that rich mixture is also required to keep the valves cool.
At this point, I’m happier sacrificing a small amount of HP for a safer engine, especially as the result we got on 16PSI was much higher than I had anticipated

In the next dyno session, after he has sorted the ignition, I will get the fuelling a bit leaner. But as I’m not a tuner, I will still have to rely on his experience and knowledge.
I think that I worked out that if I could get IAT back down to what I see on the road, around 30Deg, it should theoretically give me an extra 7HP, just on fuel alone, without the fact Ignition could be advanced more safely, but that’s just my over simplified theory. Proof will be in the testing…
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Re: Undertanding mid-pulse mode with siamese-port timing

Postby Graham T » Sat Oct 31, 2015 5:45 am

Also, It’s a bit messy/full, but here’s a graph depicting the PW’s V Injection timing:

Image

I think you can see with my VE table, where the PW merging started to have an effect.

Image

Could those highlighted area’s be lower because in essence, as the injector is already open due to the Inner Pulse width still being in progress, there is no actual dead time for the outer pulse, hence more fuel flowing than the ECU is aware of?


And dyno result v datalogging:
Image

Inlet temperatures and monitoring.

Image

One question on the Temperatures, they are somewhat erratic. Is this a case of changing the lag factors to smooth them out?
The last set of data for inlet monitoring is gained from Rod S’s ADC Extender board: viewtopic.php?f=9&t=1543&p=8377#p8377
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Re: Undertanding mid-pulse mode with siamese-port timing

Postby jbelanger » Sat Oct 31, 2015 11:19 am

One thing you could also try is to use the hybrid mode. This would let you use a higher percentage of the duty cycle for actual fueling when it goes in single pulse mode. And that would do something similar to what you had with the pulse overlap. I agree with you that this lower VE value is likely due to having more fuel due to losing the dead time but with the single pulse mode, that would be intentional and controlled.

It seems like a good idea to try the injectors with the wider spray angle. But I agree with you that you will likely fall short in capacity for 200hp with those.

Jean
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Re: Undertanding mid-pulse mode with siamese-port timing

Postby Graham T » Sun Nov 01, 2015 2:14 pm

Ok, thanks Jean.
I have the 640cc/min injectors installed now, but not had a chance to drive out.
I'll keep you posted and maybe try the hybrid mode if necessary, though I'd rather try to stick with the 2 independent pulses if possible.
More to follow...
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Sequential Siamese mode questions

Postby Graham T » Sat Nov 07, 2015 8:48 am

Jean, next set of questions, Injector Staging this time…

Below are the graphs for the second run at 16PSI boost on the Dyno, which had to be aborted.
On this run we actually included Staging, which in all honesty I had forgot we did.
The run was aborted because there was an O’ring failure on one of the secondary injectors, so fuel was spraying all over the turbo and exhaust manifold.

It’s actually a shame we had to abort the run, because what we did get looked like it promised to produce better power than in the previous run at 16PSi. We had let the engine/ engine bay cool and reduced fuelling just a little, which looks like it could have help improve power at the top end.
3 of the rolling road power results:


Image

Staging was set with 2 parameters, RPM and MAP, with gradual transitioning set for 150 Ignition events.
You can see in the below where staging kicked in and created massive over fuelling, which lost a fair amount of power until the gradual transition was complete.

Image

Also this shows how the staging should/does help with Pulse width overlap:

Image

What I’m not clear on is whether the way that the staging gradual transition worked in the above is how it should work?
I expected Secondary Pulse widths to increase at the same rate as the Primary pulse widths decreased, hence keeping fuelling uniform during the transition.

This morning I have spent a bit of time with the MS2 on the JimStim, working through all the Staged injection options, so far the only way I can get it to work without any potential issues is without gradual Transitioning enabled, or setting the staging transition events to very low numbers to avoid the over fuelling. As yet, I’ve not tried that in the car, as it’s pretty wet here.
I’m hoping I will not need the gradual transition set, but I just wanted to know if there is something obvious I need to set.
Staging set with Duty cycle as the Primary parameter does work at all.

I also tried using the Staged injection table, but this produced some unexpected results:

Image

The issue here of course being that PW2 drops during the staging transition from 2850 to 3000RPM, which means my Inner Cylinders will lean out.

So far, the only way I can see to get Staged injection operational with sequential Siamese is to set the Staged injection parameters to RPM, TPS or MAP, with the possibility of a Secondary Parameter if required, but with no Gradual transitioning set.
This may not be a problem, but I’m just trying to understand if I may have something set wrong or whether what I am trying to do is just not possible and what, if anything, I can do if non graduated Staging causes me issues.


Thanks

Graham
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Re: Sequential Siamese mode questions

Postby jbelanger » Sat Nov 07, 2015 11:47 am

Graham,

It has been a long time since I've done any work on the siamese code and played with staging. There might have been some code modifications that have introduced conflicts or may not work as intended. Or it might just be a setting.

I will need to have a copy of your msq and datalog(s) to get a better idea.

Jean
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Re: Sequential Siamese mode questions

Postby Graham T » Sun Nov 08, 2015 5:51 am

Jean,
It looks like we already discussed the table issues back in 2010 on the turbominis forum-

http://www.turbominis.co.uk/forums/inde ... tid=385919

At the time you believed it was due to the table being backported from the MS3 code. In any case it probably would not be the right option for what I am trying to do. I've attached a datalog of it non the less.

It also looks like with no graduated transition in the code back then, it was more the injection timing that was causing me issues rather than the staging.
I'm stuck on MS2Extra 3.1.1 because of changes I have the code, which I've not been able to include on subsequent versions, so it maybe a case of make the best of what I have.
If "no graduation" set gives me any issues, I could possibly set the transition to a very short duration which would help to overcome potential lean outs. And there is also the ability to add the secondary staging enrichment.

Of course, I need to get some testing under my belt with staging, but it was really just to get confirmation that I have everything set as it should be.
Attachments
staged_table.msl
(201.93 KiB) Downloaded 66 times
staged_PrimaryParam_NoGrad.msl
(237.33 KiB) Downloaded 65 times
staged_PrimaryParam.msl
(229.83 KiB) Downloaded 62 times
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Re: Sequential Siamese mode questions

Postby Graham T » Sun Nov 08, 2015 5:52 am

And as I could only include 3 attachements in the previous post, here is the MSQ.


Thanks

Graham
Attachments
A1310_TC.msq
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