Batch injection with siamese ports, injector timing
Posted: Wed Jul 04, 2018 6:26 am
Hi all
Thought I'd better create a new topic to continue this discussion:
https://pcmhacking.net/forums/viewt ... 5&start=40
Specifically we're talking about a VN V6 setup on a Holden grey engine (with $12P). Its already been physically set up with 3 injectors in the manifold near the ports, using the V6 coil pack with the original crank angle sensor. Its running with a factory tune and some injector size adjustments, not particularly well but nothing worse than I'd expect from a completely un-tuned engine.
It was mentioned in the link above that Mini engines are pretty much a no-go with the siamese ports and batch injection, however I think that's a worse case than this due to the small number of cylinders and firing order - it will always have the cylinders sharing an intake port firing one after the other making it very difficult to supply the correct fuel to the second. With the six and a firing order of 1-5-3-6-2-4 this isn't the case. If we label the ports A (1 and 2), B (3 and 4) and C (5 and 6) for argument's sake, then the intake port order is:
1-5-3-6-2-4
A-C-B-C-A-B
with respect to the cylinder firing order. To my mind this means that with double fire injection (once per revolution rather than once per cycle), then each intake port has a fresh injection event unless the injection is for cylinder 5 (C-B-C) or 2 (A-B-A) - then the port needs to be used twice in one revolution. But at least not twice in succession, and every other starting position does not involve using the same port in a revolution.
Does the above make sense?
I know that the ECU doesn't have a position reference and would normally start injecting based on pulse inputs at any position. Being run by a V6 ignition module which does use a position (so it can fire the correct coils), does it solve this problem by starting the signal to the ECU at the right point, or is this just passed straight though? Unfortunately I'm thinking its the second which doesn't help. Is there any way to get around this, so it always starts the input to the ECU at #1?
When exactly do the injectors fire in relation to the spark? Tweaking the timing of this somehow may also be an option to improve the above problem, to stop the first cylinder in a shared intake port from removing too much fuel.
What is the limiting factor for double fire injection? Its not exactly a high revving engine.
Thanks for any input.
Thought I'd better create a new topic to continue this discussion:
https://pcmhacking.net/forums/viewt ... 5&start=40
Specifically we're talking about a VN V6 setup on a Holden grey engine (with $12P). Its already been physically set up with 3 injectors in the manifold near the ports, using the V6 coil pack with the original crank angle sensor. Its running with a factory tune and some injector size adjustments, not particularly well but nothing worse than I'd expect from a completely un-tuned engine.
It was mentioned in the link above that Mini engines are pretty much a no-go with the siamese ports and batch injection, however I think that's a worse case than this due to the small number of cylinders and firing order - it will always have the cylinders sharing an intake port firing one after the other making it very difficult to supply the correct fuel to the second. With the six and a firing order of 1-5-3-6-2-4 this isn't the case. If we label the ports A (1 and 2), B (3 and 4) and C (5 and 6) for argument's sake, then the intake port order is:
1-5-3-6-2-4
A-C-B-C-A-B
with respect to the cylinder firing order. To my mind this means that with double fire injection (once per revolution rather than once per cycle), then each intake port has a fresh injection event unless the injection is for cylinder 5 (C-B-C) or 2 (A-B-A) - then the port needs to be used twice in one revolution. But at least not twice in succession, and every other starting position does not involve using the same port in a revolution.
Does the above make sense?
I know that the ECU doesn't have a position reference and would normally start injecting based on pulse inputs at any position. Being run by a V6 ignition module which does use a position (so it can fire the correct coils), does it solve this problem by starting the signal to the ECU at the right point, or is this just passed straight though? Unfortunately I'm thinking its the second which doesn't help. Is there any way to get around this, so it always starts the input to the ECU at #1?
When exactly do the injectors fire in relation to the spark? Tweaking the timing of this somehow may also be an option to improve the above problem, to stop the first cylinder in a shared intake port from removing too much fuel.
What is the limiting factor for double fire injection? Its not exactly a high revving engine.
Thanks for any input.