[Diy_efi] injecting 5 port head

[Tom Visel]

Has anyone considered poppet-type injectors like GM's 5.7l Vortec truck 
engine?  With their relatively small diameter at the nozzle end, they 
could be placed right near the valve, perhaps eliminating shared fuel 
problems.  It might be simply a matter of making a sheet metal bracket 
that sandwiches in between the manifold and head like the gasket, and 
extends into the port to hold/aim the nozzles.  The pipes for the 
nozzles run to some convenient place in the manifold where the actual 
injector bodies sit with their electrical and fuel connections.
TomV

Adam Wade wrote:

>--- Jean Belanger <jean at jeanbelanger.net> wrote:
>
>  
>
>>I was not forgetting that, I was just simplifying
>>things for a general explanation.
>>    
>>
>
>It seems you "simplified out" the main problem, unless
>I missed something.
>
>  
>
>>As for making it easier with multiple injectors,
>>Rover did not seem to think so when they made the
>>MPi Mini.
>>    
>>
>
>Unless you have at your disposal an engine dyno with
>at least 4-gas analysis and full engineering access to
>your ECU, and some long-term professional injection
>system designers and programmers, I doubt that Rover's
>solution would be "easier" to develop.  I was looking
>for the simplest way that could be managed with a
>fairly low-tech solution that would be reasonably
>cost-effective for a hobbyist, and I think the
>solution I offered is one of the easier/cheaper
>approaches for a hobbyist with limited funds and
>tuning tools.
>
>  
>
>>You should have a look at the Rover patent because
>>they describe 2 modes of operation. One mode is the
>>obvious pulse on an open valve and the second is
>>a single pulse which starts when the number 2 (or 3)
>>cylinder valve is open and finishes when the number
>>1 (or 4) cylinder valve is open covering the
>>overlap region. I don't know if the MPi engine uses
>>them both but it seems the best way to go to high
>>RPM and still have a reasonable size injector
>>without worrying about the time needed to open and
>>close the injector during the intake overlap.
>>    
>>
>
>That's a reasonable assessment.  However, I'd wager
>that one could produce more power using a more
>"discerning" setup, even at high rpm; unless I'm not
>clear on something, it would seem that there would
>still be mixture distribution issues with that
>technology, albeit of a much lesser nature than at
>lower engine speeds.
>
>  
>
>>I assume that this mode also requires a cam which
>>does not have an excessive amount of overlap between
>>intake and exhaust otherwise you'd be injecting fuel
>>out the exhaust.
>>    
>>
>
>I suppose it would depend on what sort of fuel economy
>and emissions profile were required by the designer;
>if you're not running a cat, unless you're concerned
>about emissions or fuel economy, there's no reason to
>worry much about unburned fuel passing into the
>exhaust.
>
>  
>
>>>In particular, as I understand it, you cannot
>>>inject fuel prior to the closing of the "inside"
>>>cylinder's intake valve and have any of that fuel
>>>end up in the "outside" cylinder -- for cylinders 2
>>>and 3, you are limited to the time between the
>>>closing of the #2/3 intake valve and the closing
>>>of the #1/4 intake valve, which is a pretty short
>>>period, especially at higher rpms.
>>>      
>>>
>
>  
>
>>This is true for discrete injection pulse per
>>cylinder but with the mode described above it is
>>no longer true if you time the pulse correctly
>>(which has to be done anyway). 
>>    
>>
>
>I'd assume that the dynamics of intake flow, and where
>it goes when, at what velocity, is a very complicated
>thing indeed in siamesed-port intakes like the one
>described, and would probably vary radically with
>changes in throttle and engine speed.  This is one of
>the reasons why I lean toward a solution that pretty
>much confines a certain injetor's contribution to a
>particular cylinder; it would be far easier to tune
>without needing CFD or experimental flow rate and
>direction data to insure reasonable mixture
>distribution, IMO.
>
>  
>
>>During the intake overlap, some fuel will go to both
>>cylinders but the amount to each should be similar
>>from cycle to cycle.
>>    
>>
>
>In a steady-state condition, I'd say "more or less". 
>In a dynamic condition, I'd be willing to bet the
>numbers fluctuate pretty heavily, and if someone were
>to try that, I'd suspect their four-gas exhaust data
>would support that theory.  I don't have access to
>anything like that, but if anyone on list does, I'd be
>VERY interested in seeing it.
>
>  
>
>>So you just need to time the injection pulse to get
>>a constant AFR between the cylinder pair.
>>    
>>
>
>Which, as I noted, is likely a lot tricker than it
>sounds when looking at the entire operating range of
>the engine, and which would be either very
>time-consuming or very difficult (or both!) to achieve
>without pretty solid knowledge of the true dynamics
>within the manifold, under a given set of operating
>conditions.
>
>  
>
>>>I think a staged injector system might be in order
>>>here; in fact, it's possible that the optimal
>>>combination would be a single sat. drive injector
>>>for cylinders 2 and 3, and staged dual injectors
>>>for cylinders 1 and 4, which would allow a honkin'
>>>big injector for higher-load running and a small
>>>injector to handle idle control.
>>>      
>>>
>
>  
>
>>And this is simpler than one injector per port?
>>    
>>
>
>In terms of achieving even and correct fueling for
>each cylinder individually?  Yes, much simpler indeed.
> With that setup, you can deliver fuel for #2/3 in
>much of the before the cylinder's intake valve opens
>(and before the #1/4 intake valve opens), and can
>deliver enough fuel for cylinder #1/4 ONLY during the
>time period where its intake valve is open and #2/3
>intake valve is closed.  Once you have the code set up
>so that for a given value in a map cell each of the
>two different styles of injector setup deliver the
>same amount of fuel, it then becomes very easy to test
>and tune for best possible power without having to do
>any fancy trickery or computations (or measurement
>while on the dyno) to keep fueling consistent between
>all cylinders.
>
>  
>
>>It seems quite complex for both hardware and
>>software.
>>    
>>
>
>I wouldn't think it would be terribly difficult for
>software.  You'd be running 2 cylinders staged and 2
>cylinders not staged.  If you were concerned about the
>code, you could use 8 staged injectors and not have to
>worry about code balancing the two different types of
>injection; this would cost a little more in hardware,
>but would make programming a no-brainer using any
>system that can handle staged injection, as long as
>there is real estate available for mounting all 8
>injectors.
>
>  
>
>>But for this staging you only need 2 injectors per
>>port not the 3 you're suggesting
>>    
>>
>
>It sounds like you're relying on your claim above that
>it is easily "do-able" to use either a single injector
>or a single pair of staged injectors to fuel the
>adjacent cylinders through the single port, and I
>don't think that is within the abilities and means of
>most people on this list.  I suppose it would be
>possible with proper resources, but even if it were,
>it would likely be a much simpler and quicker
>implementation to just insure that there is one
>injection event per cylinder delivered by a dedicated
>injector (or staged pair), since you don't have to
>computer intake flow throughout the operating range,
>or test via trial and error and four-gas data to tweak
>the injection timing throughout the full operating
>range (and then you have to do the computation as well
>to determine if the optimal injector opening times
>have changed, and to insure they are triggered on
>schedule).
>
>  
>
>>(or is it 5 total?).
>>    
>>
>
>6.  I'm not sure how 5 would be workable in any
>meaningful sense.
>
>  
>
>>>Timing the injection on the
>>>center pair of cylinders will be critical.
>>>      
>>>
>
>  
>
>>I agree that timing is critical but it's for the
>>outside cylinders.
>>    
>>
>
>Sorry about that.  I wrote the reply and had
>everything backwards regarding the cylinder pairs,
>then went through and corrected them all.  Looks like
>I missed that one in my editing.
>
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