connection of 2 injector outputs to 1 injector

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bofelix
Posts: 27
Joined: Mon Apr 01, 2013 2:53 pm
ECU Model: S60 Pro
Distributor: roverdose
Firmware Version: 66

connection of 2 injector outputs to 1 injector

Post by bofelix »

Hello,

is it possible to connect 2 injector outputs of the S60 ECU to the same injector? Or will this damage the injector drivers / power stages?

Why?

I would like to build a single point injection unit from a single carburator with one Magneti Marelli Pico IWP069 injector inside, which injects on the throttle plate. I need 2 injections per engine revolution (4 cylinder engine). With the setting "injectors in 2 stroke mode" i will just get one injection per revolution. So I need 2 injector outputs and injectors in 2 stroke mode. It is for an aircooled flat 4 engine in a VW beetle (1300cc, 32 kW, single intake port). These cylinder heads does not allow to fit 2 injectors in the head due to the single intake port for 2 cylinders.

The IWP069 injector is big enough, so that injector duty cycle is lower than 85% and there is enough reserve for addional cold start fuelling.

Thank you very much for your answers / thoughts!

best regards, have a nice day
Stefan
Rob Stevens
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Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: connection of 2 injector outputs to 1 injector

Post by Rob Stevens »

I don't know why you would want to do this, it will work fine with one injector? However If it is anything like the BMC A series with 5 ports you may have to do something with 2 injectors per port and run sequentially to avoid charge robbing. I'm sure Alex can clarify, do the paired cylinders fire 360 degrees apart? Sorry not familiar with vw flat 4, if so it would be fine on one injector and output
katana
Posts: 455
Joined: Sun Jan 27, 2013 6:08 pm
ECU Model: S60 Pro
Firmware Version: 29

Re: connection of 2 injector outputs to 1 injector

Post by katana »

My thinking is surely if the original engine manages with a single carb ie single point fuel source, it will equally function with a single fuel injector? But the real question is why supply a complex EFI system and replicate an antiquated inefficient OEM installation? Surely if each cylinder has an inlet runner an individual injector boss could be fitted to each and use a single throttle body to meter the air supply - far more efficient!
bofelix
Posts: 27
Joined: Mon Apr 01, 2013 2:53 pm
ECU Model: S60 Pro
Distributor: roverdose
Firmware Version: 66

Re: connection of 2 injector outputs to 1 injector

Post by bofelix »

Hello Rob,

the flat 4 engine has unequal firing angles at both sides. Two cylinders at one engine side are sharing the intake port.
The firing order is 1-4-3-2, so the cylinders at one side are firing direct one after the other with only 180°CA difference, then 540°CA. Even with the very mild stock cam timing the valve inlet events are slightly overlapping.
I have also put some thoughts on a multi point full sequential concept with 4 Bosch EV14 injectors which are injecting fuel on the inlet valves. This solution could work (and will work!), but there is some welding and machining on the cylinder heads and/or intake manifold necessary. It would take much time to work this out.

The single point injection in the carburetor would be much more faster and a first step to get also injection running. The ignition is running since 4 years on the S60. First thought was to add 2 injectors in the carburetor, but it is very small and one injector is easier to integrate, because there is only one fuel supply necessary.

thank you and best regards
Stefan
Alex DTA
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Joined: Fri Feb 28, 2014 1:03 pm
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79

Re: connection of 2 injector outputs to 1 injector

Post by Alex DTA »

To join two injector outputs, you must put diodes inline to prevent back feeding in to the ECU inputs.
You must also be very careful not to go above about 50% duty cycle, or you could end up with both injector outputs on at the same time. This includes cold start, so you'll fine this very difficult to do.

It's not something I would recommend, especially when there are throttle bodies that will fit the original manifold.
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
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Location: Norn Iron

Re: connection of 2 injector outputs to 1 injector

Post by stevieturbo »

Why do you feel you need whatever number of injection events for whatever ? For a wet setup, I'd doubt it would be overly critical

if you're injecting pre-TB, which is probably the easiest option for a Siamesed setup.....I wouldn't worry too much. Or just run a couple of injectors ?

With the A-series, most seem to use Megasuirt with code specifically designed in a sequential mode so that injector opening times will correlate with the relevant valve events ( port injection ) to minimise charge robbing, and they will also monitor lambda on all 3 exhaust ports to determine to some degree if things are all ok.
This often requires quite large injectors, as the window/time for injection events gets smaller with rpm

With a wet manifold setup like a SPI, it seems to be far less of an issue. More so when distance from the throttle/injector is a fair length, which I presume is the case with most flat 4's

IMO, single injector is easy....give it a try first without any strange wiring or setup
bofelix
Posts: 27
Joined: Mon Apr 01, 2013 2:53 pm
ECU Model: S60 Pro
Distributor: roverdose
Firmware Version: 66

Re: connection of 2 injector outputs to 1 injector

Post by bofelix »

Hello,

thank you for all the answers, thoughts, recommendations.

It is true, there is no need for 2 injections per revolution, one should also work. But as far as I remember the first Bosch Monomotronic had just one 1 injection per rev and later on there was an update on Monomotronic 1.2 which hat 2 injections per rev in order to improve carburation with focus on emissions and fuel consumption.

I will try to get two injectors in and run the injection in two stroke mode. Then I do have the 2 injections per rev.

Thank you and best regards
Stefan
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