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1267 Posts Member #: 831 Post Whore Montreal, Canada |
15th Jan, 2006 at 06:02:28pm
If you look at the same picture (Fig.4), the dashed line represents the mode I was talking about. They mention this in the text as an alternative mode starting at the bottom of page 6.
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47 Posts Member #: 830 Member SLC, UT |
15th Jan, 2006 at 08:29:23pm
On 15/01/2006 15:56:33 jbelanger said:
Injectors are rated in cc/min or lbs/hr. From this rating you get the amount of power the injector can supply when combined with the BSFC and the IDC. The IDC is just the amount of time the injector will be open during this minute or hour, irrespective of engine cycle or number of cylinders. The injector can be supplying 1 or 4 cylinders and the engine can be running at 3000 RPM or 8000 RPM, that will not make a difference. I agree with you that there are problems with the computations but for a different reason. If you take 220cc, 58% (or 440cc, 29%) and BSFC of 0.5, you get that the maximum power would be around 49HP which is less than what the MPi engine can produce at the crank. I don't know what mode of injection is used in the MPi. Is it injecting in a pulse-pulse-wait-wait method or injecting once per 360 degrees? If it's the first one, then the maximum effective IDC certainly won't be 58% because you have to include the injector opening time within the injection window. But it will not be 29% but some other value that has to be computed as I mentioned in the previous post. If it's the latter method, then the 58% is valid since the opening time has plenty of time to occur outside the window in the 42% remaining time. If you look at the 58% and 440cc, that would allow a maximum power of about 98HP at the crank which doesn't look bad if you consider the losses and a certain margin the manufacturer would want to have. Also it fits pretty well with what has been produced with modified MPi engines with stock injection which have produce aroud 85HP max at the wheels if I remember correctly. By the way, the 2 problems you mention about injector sizing are the reason for injector staging. Of course they require twice the number of injectors but you can have one injector that will handle idle and low load and another one that will handle the top end (with the help of the smaller one). However, with a good ECU and correct setup, you can make the engine idle reasonably with rather large injectors. What size do you come up with for your setup if you take around 40-50% IDC? Jean I'm not sure quite what you're asking at the end there. Do you mean, taking my 998 w/ a projected rating of 70hp and a redline of 6000rpm, what size injectors do I get with a max of 50%IDC? I think we're having a miscommunication here, because that's kind of irrelevant. What I am trying to get across is that you do not have 50 or 58% of 720degrees to get the fuel into one cyl. You only have 25%(depends on cam specs, but I"m going to start using this because it makes my math easy) of 720 deg. That is, 25% IDC to get fuel for one cyl. That is my only point. 50%IDC is what the injector may see, but that is for 2 cyls, and the first cyl in a pair is not a problem. It won't really ever be a problem so I'm not concerning myself with it. It doesn't matter if we use a batch setup firing both ports every 360deg as has been suggested or a more sequential setup where one port fires 2 times in 360, and then the other fires twice in the second 360, or if you have 4 injectors. Getting fuel to the first cyl in each pair is easy. So, going on what you are saying, what do you calculate the size of injectors(2, 1 per port) should be for a 998cc motor that makes 70hp, will rev to 6k, and the effective valve open time is 180 degrees? Also, from those numbers you have, can you conclude that you get enough fuel into the outside cyls? The calcs don't help you there. -Tyler
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
15th Jan, 2006 at 10:14:55pm
Let's forget for one second that we're talking about siamese port and look at the fact that the injector is open for 360 degrees out of 720 degrees so it's duty cycle is 50%. So we have 70hp with 2 injectors, an effective IDC of 50%, and let's assume a BSFC of 0.5. So that means you need at least: (70hp * 0.5 lb/hr/hp)/ (2 injectors * 50%) = 35lb/hr or about 368cc/min.
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47 Posts Member #: 830 Member SLC, UT |
16th Jan, 2006 at 01:59:32am
On 15/01/2006 22:14:55 jbelanger said:
That means now that you have a single injection event lasting 360 degrees out of 720 degrees so the IDC is 50%. How would that be different from having 2 injection pulses of 180 degrees in 720 degrees? Regards, Jean because you have not guaranteed that enough fuel has reached the proper cyl. I understand what you are saying, and the injector will "see" 50% duty cycle in this case. I guess the difference is that, in my mind, there are two distinct events that occur in 720 degrees for a single port. One is 180 out of 720deg or 25% of the available time, and the other is 180 out of 720 or 25% of the available time. Since these are two separate windows, the injector must be adequate for each window individually. Maybe I shouldn't be using the term IDC because that implies a limit on the injector, which isn't the case. The limit is the time a single intake valve is open. But this requires us to size the injector to handle that. Basically, all I want to get across is that supplying enough fuel to a port in a 50%IDC does not guarantee an even split and I dont' see this as an adequate solution to the problem. From another viewpoint, if we use 4 injectors, the IDC is 25%, if we use 2 injectors we should treat them as 4. So each injector sees 2 distinct, different 25%DC, which IS different from 1 50% DC. -Tyler
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
16th Jan, 2006 at 02:41:09am
Unless the 2 distinct events result in different pulse widths, there is not difference.
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
16th Jan, 2006 at 02:56:12am
I should add one thing. Even though I'm sure about this injector sizing issue, I don't know what should be used as the actual injection window size. And I'm not sure that until there is a test done with your specific cam, intake, and injector location, if there is a way to actually get a reasonable value for your specific window size (or anyone else's). Once people start experimenting with different setups there will be more information available to draw some conclusion on that issue.
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47 Posts Member #: 830 Member SLC, UT |
16th Jan, 2006 at 05:04:00pm
I understand what you're saying. the Injector will operate at 50% IDC.
-Tyler
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47 Posts Member #: 830 Member SLC, UT |
16th Jan, 2006 at 05:14:40pm
I know I said that would be my last post, but this will be.
-Tyler
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
16th Jan, 2006 at 09:16:48pm
On 16/01/2006 17:04:00 mrbell said:
I understand what you're saying. the Injector will operate at 50% IDC. What I am saying and what I'm trying to make clear is that 50% is not an important number. Here are the last few things I will say on this: Does 29% as opposed to 58% fix the equations on marcels page? Does a 4 stroke engine have a 720 cycle and is 208 29% of 720? Since we have 4 injection events in an engine cycle, using the rc engineering calculator substituting 4 in the number of injectors(since essentially, we are treating one injector like two), does 29%IDC give us what we need? If we were to subsitiute a properly timed sequential injection ECU into this system, and wired two adjacent injector drivers to a single injector, would the IDC be 29%? The answer to all of those is YES. You're simply wrong that the 50% is not important. That's the real number you need to size the injector. 58% is just one number on Marcel's page that you can change to arrive at your desired result. I just realized what'is not correct on the page. He took 3700 as the RPM. That might be fine for fuel consumption but it certainly is not for the max IDC. So the 255ml/min he gets at the end should be adjusted to the max RPM. Assuming that it's 6500RPM that gives: 255ml/min * 6500RPM/3700RPM * 1/0.58 / 2 injectors = 386ml/min If you consider that you want some margin on the window size and you put 50% instead you get 448ml/min. So with the approximation on the fuel comsumption and the margin, I think this is close enough to the 440cc/min. The computation you make are ok if you have 4 injectors but if you have only 2, you're wrong. The RC engineering computation is for the actual number of injectors. It does not matter if it's for a "normal" port injection, TBI injection, or siamese-port injection. If you do the computation for a TBI for a V8 engine and the TBI has 4 injectors, you put 4 in the computation not 8 because there are 8 cylinders. The same applies here. If you were to use 2 injector drivers, each driver would be opening the injector 29% of the time so the injector would be open for 58% of the time. So no, you're not correct, you're just reaching wrong conclusions based on wrong assumptions. On 16/01/2006 17:14:40 mrbell said:
I know I said that would be my last post, but this will be. What will the pulsewidth be sent to the injector? Ideally, it will be something along the lines of 2.5ms @6000rpm. This is 25%IDC for an engine cycle that takes 10ms. Just because there are two of them, makes very little difference because they are not for the same cylinder event. By the way, one cycle at 6000 RPM is 20ms since it's 720 degrees. So the pulse width will be 5 ms (180 degrees) but there are going to be 2 of them so the injector is open for 10 ms out of 20 ms which is 50%. I'm not trying to antagonize you but you seem to be stuck on this notion that everything has to be done with respect to a single cylinder. That is correct to compute the injection window size. Once this is done then you just need to see what the injector will have to do and it will have to inject twice in a cycle and from that you compute the correct size. I'm sorry that you don't get this and I hope you'll try to understand because otherwise you'll have a very hard time getting further along in the understanding of all the issues of siamese-port injection. This part is actually quite basic compared to other issues. Regards, Jean |
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47 Posts Member #: 830 Member SLC, UT |
17th Jan, 2006 at 12:10:17am
On 16/01/2006 21:16:48 jbelanger said:
I'm not trying to antagonize you... I'm sorry that you don't get this and I hope you'll try to understand because otherwise you'll have a very hard time getting further along in the understanding of all the issues of siamese-port injection. This part is actually quite basic compared to other issues. Regards, Jean No worries, I know we're just trying to attain the same goal, but I believe we just have different methods. I'm just not doing a good job of explaining myself. I'm sorry about the bad math earlier this morning, I don't think I was awake yet, or I was being distracted by something shiney because I don't remember writing some of that. In any case, I believe we all will come up w/ the proper solution and they will all be very similiar, I just seem to value one part of the problem while you value another. Neither is wrong, I don't think, they're just different perspectives. -Tyler
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
17th Jan, 2006 at 12:29:53am
Fair enough. We do have different perspectives :)
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Forum Mod 10980 Posts Member #: 17 ***16*** SouthPark, Colorado |
17th Jan, 2006 at 01:02:46am
Jump in anytime Marcel....
On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY |
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 20 Posts Member #: 799 Member Canada, eh? |
17th Jan, 2006 at 05:50:54am
On 17/01/2006 01:02:46 TurboDave said:
Jump in anytime Marcel....  Nope, not gonna. While you yobs are blathering away on things that one simple experiment could solve, I'm out in the workshop actually DOING something. I test fired the Elder EFI 8-port tonight. It made noise for about 3 cycles but the battery didn't have enough juice to go any further. It will charge overnight and I'll fire it up properly tomorrow.
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Forum Mod 10980 Posts Member #: 17 ***16*** SouthPark, Colorado |
17th Jan, 2006 at 01:54:03pm
ha ha ha!
On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY |
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
17th Jan, 2006 at 02:34:05pm
Marcel,
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20 Posts Member #: 799 Member Canada, eh? |
17th Jan, 2006 at 05:10:14pm
There are lots of errors in the thesis on my web page, I did, afterall, do the research in a vacuum 5 years ago with DTA naysaying every step of the way. I knew I was getting close when Emerald refused to talk to me anymore
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Forum Mod 10980 Posts Member #: 17 ***16*** SouthPark, Colorado |
17th Jan, 2006 at 05:18:32pm
Maga7ine - Are you willing to pay for a development ECU that Jean can program up and send to Marcel? On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY |
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1267 Posts Member #: 831 Post Whore Montreal, Canada |
17th Jan, 2006 at 11:39:01pm
If Maga7ine and Marcel are up to it, that would be great. I estimate that within a month of having an ECU I could have a version that is quite solid and has much fewer restrictions than the current version (such as ignition).
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20 Posts Member #: 799 Member Canada, eh? |
18th Jan, 2006 at 05:18:22pm
On 17/01/2006 23:39:01 jbelanger said:
About your work, do you have other material not on your site that you'd care to share? I summarized all my research on my page. It was done quick 'n dirty primarily because there were others hunting the same pot-O-gold at the same time and I wanted to stake my claim first. As it turns out, neither Emerald nor Keith Calver actually got far enough to publish anything anyway. What I do have is a sort of recipe for success which I will post somewhere on this forum as a separate item. Each point in the recipe is backed up by research, most of which is documented in the stuff on my site. I never got around to summarizing my research on injector reaction time but I’ll be redoing that this spring. I also don’t have equipment to investigate the travel speed of fuel pulses. I need a variable speed strobe light to do this and I ain’t gonna buy one! These data can be inferred by physical testing in a real engine. The recipe is a thesis open to scientific scrutiny, but it has to be done by qualified people, in a scientific way by replicating my experiments. Throwing opinion darts by naysayers will accomplish nothing.
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