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  #51  
Old 02-26-2021, 10:48 AM
jacoby jacoby is offline
 
Join Date: Jul 2018
Location: WNC
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Quote:
Originally Posted by lr172 View Post
The poster made claims that semi-sequential injection is better. I also would like to understand the rationale for that claim, as I also question it. Also would like to know what he means by it, as the industry only refers to batch or sequential injector firing; Never heard of semi-sequential prior to this post. Nothing wrong with calling out a vendor to back up his claims, advertiser or not. I personally appreciate those that ask for backup details on claims of improvement.

From my experience, proper sequential injector firing is not possible without a cam position sensor.

Larry
My understanding is semi-sequential is similar to wasted spark but for injectors. So instead of firing all [4,6] injectors at the same time you fire pairs twice per revolution. At least that's how it's used in the MegaSquirt world. I don't know how it's used in the EFII32 system.

See this from Toyota's TCCS docs:

Simultaneous = Batch
[2,3] Groups = Semi-Sequential
Independent = Sequential

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  #52  
Old 02-26-2021, 11:18 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Quote:
Originally Posted by jacoby View Post
My understanding is semi-sequential is similar to wasted spark but for injectors. So instead of firing all [4,6] injectors at the same time you fire pairs twice per revolution. At least that's how it's used in the MegaSquirt world. I don't know how it's used in the EFII32 system.

See this from Toyota's TCCS docs:

Simultaneous = Batch
[2,3] Groups = Semi-Sequential
Independent = Sequential


I did a megasquit install on a 6 cyl porsche. It was batch fire with two discrete banks. I still consider all of these approaches as batch, as firing an injector, other than when the valve is open, all pretty much nets the same result, leaving out wall wetting and other minor differences, regardless of how far from valve opening the shot is made. That is my understanding, but am open to being schooled by those more knowledgable.

Note that the toyota approach essentially uses a cam pos sensor (signal picked up on the dist vs the crank) to fire the groups on the intake stroke, so possibly some benefit there. The EFII system does not have a cam pos sensor, so can't do this. They have no way to differentiate the power and intake strokes, as you can't put a cam sensor on the lyc and the mag runs 1:1 unlike an auto dist at 1:2. TOyota says that semi-seq requires knowing the intake stroke, yet Robert still claims semi-seq without it. Curious how he is doing it. Possibly he has a different definition.

Larry
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Last edited by lr172 : 02-26-2021 at 11:27 AM.
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  #53  
Old 02-26-2021, 11:23 AM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
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Location: Calgary, Canada
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Batch fire doesn't care about where the valve or piston is at all, any more than that is a concern on Bendix style mechanical injection which is continuous flow.

When the valve opens, fuel and air mixture is drawn into the cylinder.

Of note, even on "sequential" injection (I prefer the term timed), at high rpm and high throttle, there isn't enough time to inject all the fuel required when the valve is open so even sequential systems inject some fuel when the valve is closed at high power and rpm. Sequential is useful for low rpm, part throttle conditions in cars with emission standards to meet. Not much of those conditions in aircraft (mostly at or near WOT and no emissions).

We've triggered injectors in ones, pairs, threes and six at once over the years depending on application. They all ran just fine from idle to full power. Injection events are typically at half crank frequency (cam frequency).
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 445.9 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


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  #54  
Old 02-26-2021, 12:26 PM
rocketman1988 rocketman1988 is offline
 
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Location: Sunman, IN
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Default Marketing

Quote:
Originally Posted by airguy View Post
Or perhaps it's simply time to get answers to the questions? Or do we just close down threads one after another to avoid have a fact-based discussion in favor of marketing?
I certainly see a lot of “marketing”...

...and that’s all I have to say about that...

Now back to flying! Done with Phase 1!

Thank you Robert, the EFII system has been flawless...
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Last edited by rocketman1988 : 02-26-2021 at 12:29 PM.
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  #55  
Old 02-26-2021, 12:37 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by jacoby View Post
I don't know how it's used in the EFII32 system.
Which remains as the simple question on the table.
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  #56  
Old 02-28-2021, 01:32 PM
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skylor skylor is offline
 
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Location: Southern California
Posts: 960
Default Cam Sensor?

Quote:
Originally Posted by rv6ejguy View Post
All the talk about sequential (can't do on a Lyc. without a cam sensor)...
Ross,

Great information in your post, as always!

I am, however, curious why you would need a cam sensor on an engine with fixed cam timing to use sequential injection? On Lycoming's, since the cam is directly driven at 1/2 crankshaft speed, I would think that you could directly derive the cam timing from a crankshaft trigger wheel such and Dan Horton is using for his EDIS ignition system. Of course it's all a moot point, really, because as you pointed out, there really isn't an advantage to sequential injection on our low speed, steady state (and large induction system volume) Lyconental engines...

EDIT: I may have just answered my own question, because I realize there's that pesky issue of determining which cycle each cylinder is on...

Skylor

Last edited by skylor : 02-28-2021 at 01:37 PM.
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  #57  
Old 02-28-2021, 02:40 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by skylor View Post
Ross,

Great information in your post, as always!

I am, however, curious why you would need a cam sensor on an engine with fixed cam timing to use sequential injection? On Lycoming's, since the cam is directly driven at 1/2 crankshaft speed, I would think that you could directly derive the cam timing from a crankshaft trigger wheel such and Dan Horton is using for his EDIS ignition system. Of course it's all a moot point, really, because as you pointed out, there really isn't an advantage to sequential injection on our low speed, steady state (and large induction system volume) Lyconental engines...

EDIT: I may have just answered my own question, because I realize there's that pesky issue of determining which cycle each cylinder is on...

Skylor
Yes, your edit is correct.

We've been asked many dozens of times over the years how injectors are timed to valve opening- short answer, they aren't and it doesn't matter how the injector drive wires are hooked up, except in the case of systems with fuel trim where we do have to have the right transistor driving the right injector so that you trim the correct injector/ cylinder with the programmer.

Dave Anders did a lot of flight testing on induction tubes lengths (still ongoing BTW) and found the fuel trim indispensable for determining if he was getting more airflow or less. He really wanted to time injector spray to valve open time but there is no way to do this without a cam sensor and again, you'd need very large injectors to get the squirt done in the available time the valve is open at high power.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 445.9 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


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  #58  
Old 02-28-2021, 06:15 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
...you'd need very large injectors to get the squirt done in the available time the valve is open at high power.
So Ross, when and how long does an SDS system open its injectors? Pick whatever RPM and A/F you like. Let's see the result...here's the base diagram.
-
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  #59  
Old 02-28-2021, 09:04 PM
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airguy airguy is offline
 
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Quote:
Originally Posted by DanH View Post
So Ross, when and how long does an SDS system open its injectors? Pick whatever RPM and A/F you like. Let's see the result...here's the base diagram.
-
It's going to depend on fuel rail pressure and delta across the injector face - but since Ralph Inkster has been kind enough to publicly share his EM-5 map, we can use his for an example. Mine largely dovetails.
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Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #60  
Old 03-01-2021, 07:40 AM
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rv6ejguy rv6ejguy is offline
 
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Dan,

I'll try to find time tonight to look at some in-flight logging and grab a couple screenshots showing the injector pulse widths at different MAP/RPMs for you. Not sure I logged much in the gauge screen, mostly would have been in the graphical mode which displays duty cycle.

As far as when the injector pulse occurs after the trigger pulse occurs, I'd say I don't know the answer to that as it's not something we have a reason to care about as outlined above. It's unimportant in a batch fire system like SDS. I think you have a couple SDS ECUs there. If you have a dual trace scope, you can check that for your own interest.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 445.9 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


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