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 8604 Posts Member #: 573 Formerly Axel Podland |
15th May, 2009 at 06:16:07pm
I think that the problem is the injector itself.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
15th May, 2009 at 06:27:11pm
But if you have a reversing pulse, shouldn't you also get some reflection which means you have some sort of ram effect? And doesn't the shape of the injector pintle come into consideration (as well as the shape of the whole passage in the injector and fuel line)?
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 (2)[/url] by [url=https://www.flickr.com/photos/150672766@N03/]Rod Sugden[/url], on Fli) 5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
15th May, 2009 at 06:30:57pm
The article is interesting (no mention of low vs high z which I still think (hope?) makes a difference) but the lack of linearity is at low pulse widths.
Schrödinger's cat - so which one am I ??? |
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8604 Posts Member #: 573 Formerly Axel Podland |
15th May, 2009 at 06:32:08pm
My K1200 head also looks very appealing. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
15th May, 2009 at 06:36:20pm
On 15th May, 2009 Paul S said:
My K1200 head also looks very appealing. Somehow I just know you won't give up on this :) Otherwise next you'll be saying VEMS...... Schrödinger's cat - so which one am I ??? |
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8604 Posts Member #: 573 Formerly Axel Podland |
15th May, 2009 at 07:08:52pm
No it's Megasquirt all the way for me. No point in having to learn something else.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
15th May, 2009 at 07:22:25pm
The frustration is obvious and I only came into this late so my input is minimal at the moment.
Edited by Rod S on 15th May, 2009. Schrödinger's cat - so which one am I ??? |
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 12307 Posts Member #: 565 Carlos Fandango Burnham-on-Crouch, Essex |
15th May, 2009 at 09:47:01pm
I must say i commend you Paul, Rod & Jean for spending so much time, morey and effort on this.
On 28th Aug, 2011 Kean said:
At the risk of being sigged... Joe, do you have a photo of your tool? http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1 https://joe1977.imgbb.com/ |
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5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
15th May, 2009 at 10:14:15pm
The thing is I'm not frustrated yet, but that's because I'm following and that is an envious position to be in because you learn from what the one(s) in front have done and their results.
Edited by Rod S on 15th May, 2009. Schrödinger's cat - so which one am I ??? |
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8 Posts Member #: 5706 Junior Member Raleigh, North Carolina, US |
16th May, 2009 at 04:14:56am
On 15th May, 2009 jbelanger said: What about making it so the two pulses merge in a graceful and predictable manner? A third table just seems like too much complication. I can think of better uses for the memory.
...In any case, I agree that the way forward is the hybrid mode with all the flexibility that will bring. And it will simplify tuning by removing some variables, some fiddling, and some unintended side effects. I'll see where I'll fit the additional tables and how the transition will be handled. Hopefully I'll be able to do that relatively quickly and have a new release soon. Jean I'd be interested in trying a configuration where the start/middle/end pulse modes could be set independently for the inners and outers. One could set the inners to run in end-pulse mode, and the outers in beginning-pulse mode, thus being able to guarantee that they remain separate by a known amount. I'm still focused on exhausting the possibilities of fully exploiting the timing method that I proposed on the msextra site for my B. |
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
16th May, 2009 at 05:43:27am
I would like to do it without having to use a third table but how? I tried to think of a way to actually do it but I don't see it. You could add the 2 tables contribution but then from the merge point on, you'd need to tune 2 tables to get a single pulse which doesn't make sense. And you'd still need a third timing table.
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4314 Posts Member #: 700 Formerly British Open Classic The West Country |
16th May, 2009 at 09:25:41am
On 15th May, 2009 Rod S said:
It's a shame others aren't trying it yet I think this morning is the first time I've read one of the EFI posts and actually understood it, but I'm still not at a level of understanding where I can really add much. On 15th May, 2009 Paul S said:
The problem is that the injection window for each cylinder is no bigger than the intake stroke, so maximum of 25% for each pulse. Then you have to take away the minimum rest period between pulses which leaves you with 15-20% depending on how much your injector needs. I understand where you're coming from and how you go 25% but wouldn't the actual value be considerably less and driven by the cam choice, assuming you want to avoid having fuel loitering in the ports? Isambard Kingdom Brunel said:
Nothing is impossible if you are an Engineer |
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5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
16th May, 2009 at 10:40:49am
On 16th May, 2009 Gerald O said:
What about making it so the two pulses merge in a graceful and predictable manner? ....etc. Having had a good night's sleep I am now thinking the same. Assuming what I saw on the scope was representative of all possible setups, although the point of merge was a bit messy and random, once they had fully merged, they seemed to fall into a perfectly symettrical patteren - it just wasn't what we were expecting with alternating short and long lengths. The end points all seemed right (as expected at least) but they alternately started at the wrong point. Is there a fundamental reason for this that could be "fixed" easily. Although my intention remains to have large enough injectors (or staged) so the merge is avoided, I think I could live with the messy merge so long as the resultant pulses were wht I expected (mathematically). Schrödinger's cat - so which one am I ??? |
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
16th May, 2009 at 03:03:46pm
On 16th May, 2009 Rod S said:
Is there a fundamental reason for this that could be "fixed" easily. At the moment, each pulse is scheduled individually and the start of a pulse is scheduled at the wheel tooth before the desired angle. When the code wants to schedule the start of a pulse and sees that it's already injecting (collision between pulses) it waits for the following wheel tooth and forces the start at that tooth no matter if the previous pulse has ended or not. This works well with a normal engine where the collisions occur only when approaching 100% duty cycle. It does affect timing (delayed until the following tooth) but at that point it's not important. And it does cut short the previous pulse but since you're starting a new one, you're at 100% duty cycle or more. And once the pulse width goes down to a "normal" duty cycle, the timing is re-established together with the pulse width. The problem with the siamese code is that the pulses are not evenly distributed and they are not for the same cylinder. So when they merge, the inner cylinder pulse can be cut short by the forced start for the outer cylinders. Also, the timing for the outer cylinders is delayed by up to a wheel tooth (or 2 in some cases). The problem about fixing it is that it would be necessary to compute both the beginning and end of the inner cylinder and check if there is an overlap with the outers start. That's not trivial and it's computation intensive. Also, what do you do with the collision? Merge the pulse width and advance the outers pulse and delay the inners pulse? Advance the whole thing to preserve the overall pulse width? Then there is the issue of the 2 opening time durations that need to be re-adjusted to one but then there may not be an overlap after that. And so forth. As you can see, handling a graceful correct merging of the pulses is a very complex computation intensive process. And there would still be a need to have some user inputs to resolve certain parameters that would be different for different setups. So the 3 tables for going from 2-pulse to 1-pulse mode and having beginning-of-pulse timing for outers and end-of-pulse for inners would be the cleanest solution I can think of. It's still not an easy setup for tuning but leaves all the flexibility to handle any setup from the almost standard engine setup which could get by with only the 2-pulse mode and 2 injectors all the way to a very highly boosted engine which will need 4 injectors with the transition to single pulse mode and staged injection. Jean |
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5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
16th May, 2009 at 03:37:18pm
Jean I (think) I understand your explanation but it's this part that doesn't make sense
On 16th May, 2009 jbelanger said:
The problem with the siamese code is that the pulses are not evenly distributed and they are not for the same cylinder. So when they merge, the inner cylinder pulse can be cut short by the forced start for the outer cylinders. Also, the timing for the outer cylinders is delayed by up to a wheel tooth (or 2 in some cases). If the inner gets cut short why is it that what I'm actually seeing is the inner delayed but the outer apparently OK even after a ragged merge 
The top trace is the cam pulse (from JimStim) so at a fixed point in the cycle. So I only show one injector. Unless I'm totally confused, the purple circle shows me the outer pulse always finishing at the intended time but the green lines show the inner starting alternately on time, then late. I've picked the trace I got just as the pulses were merging (the one in the middle isn't quite there yet) but the symettry is too much to be random. Also, even if "cut short" could become "started late" depending on the timing setting choice of "start of pulse/mid pulse/end of pulse", it doesn't equate to a tooth length - there must be 72 teeth between the cam pulses, the difference in green lines is much more than 1/72nd. Rod. Schrödinger's cat - so which one am I ??? |
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
16th May, 2009 at 03:50:59pm
Rod,
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5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
16th May, 2009 at 04:10:10pm
Jean,
Schrödinger's cat - so which one am I ??? |
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