Fuel Injector End Angle

[944m3]

I’m starting to get more into the weeds of my MaxxECU. While fine tuning my idle, I came across the Injector Angle table (other standalones refer to it as Injector End Angle or End Of Injection), which was all set to zero across the RPM band. After some reading and YouTube videos I learned that this setting impacts idle and low RPM running.

Following some general suggestions, I changed the setting from 0 degrees to 400 degrees. Immediately the engine idle tone changed to a quieter idle and my lamda line flattened a little more. It definitely impacted the engine running, which has really peaked my curiosity.

I’m now working on the math suggested on some Holley forums to work out what is best degrees to use based on Pulse Width and RPM along with other variables. Using logs for some of the data. Definitely in the weeds but wondering if anyone else has played around with this setting.

[944m3]

Great video.

I’m continuing to try different angles. So far I’ve settled at 583 degrees after top dead center ATDC for my End of Injection event edge. Meaning my injector will always close at 583 degrees during the ignition cycle.

I settled on this angle after doing some behind the napkin math. The angle is right before the exhaust valve opening overlap on a stock cam. The theory is that unburnt fuel will not escape through the exhaust valve opening overlap. My injector duty cycle at idle is ~3%, which means the injector will complete its duty cycle way after the valve is open and all fuel will go into the intake port before exhaust port opens. Of course because I’m still using batch injector firing, the other half of the fuel hits the top of the intake port (while closed) which is fine. But at least I’m getting the second injection all into the intake port.

I’ve read people suggest that injector angle doesn’t matter. I disagree 100%, especially for larger injectors (I’m using 80lbs). I clearly see my lambda line flatten at my current 583 degrees. Even without graphs, I can also clearly feel the engine smooth out at idle.

To really find and configure the best angle for each rev point I do need to go to a dyno. The presenter on the video gave an example that on one particular engine he gained 10% HP just by tuning for the correct angle. Eventually I will, though I’m not saying I would gain that much but if it improves combustion efficiency then I’m happy. But for now, I’m satisfied with my findings.

Still curious to hear any feedback from other standalone users.

[Bergerac]

Injector timing is set to 400deg standard on Link from memory, it's on my list of things to look into but I haven't got around to playing with it yet.

[cda951]

Of course because I’m still using batch injector firing, the other half of the fuel hits the top of the intake port (while closed) which is fine. But at least I’m getting the second injection all into the intake port.

I’ve read people suggest that injector angle doesn’t matter. I disagree 100%, especially for larger injectors (I’m using 80lbs). I clearly see my lambda line flatten at my current 583 degrees. Even without graphs, I can also clearly feel the engine smooth out at idle.

To really find and configure the best angle for each rev point I do need to go to a dyno. The presenter on the video gave an example that on one particular engine he gained 10% HP just by tuning for the correct angle. Eventually I will, though I’m not saying I would gain that much but if it improves combustion efficiency then I’m happy. But for now, I’m satisfied with my findings.

Still curious to hear any feedback from other standalone users.

I just re-read your post and saw that you are still using batch-fired injection---the fact that you see and feel a difference shows that injector timing can is important, at least at idle. Which fuel injectors do you have, and what is the injector pulse width at idle with your current settings? I have VEMS with batch-fired Siemens-Deka 110324 injectors (bought nearly 10 years ago from Five-O motorsports, they now show as "obsolete" and the company offers a custom replacement version, see link below), and my internally stock 951 idles better than factory, passes CA smog with an idle pulsewidth of ~1.8 ms. I'll update the post with whatever the default VEMS injector timing settings are, have not changed this for my car.

My pipe dream of a 07K swap in CA is increasingly unlikely, and my original engine wiring harness has long been on borrowed time, so I've considered going to the VEMS US-made custom 951 harness wired for sequential fuel injection (with cam sync), but that would require re-tuning, and if the injector pulse width is cut in half for sequential injection, 80-lb injectors may not be accurate at such a small injection time.

https://www.fiveomotorsport.com/845cc-s ... iv-110324/

[944m3]

I’m using Siemens Deka 80lbs, which I purchased from Vitesse about 3 years ago. But I’m using MaxxECU’s built in configuration for those injectors. So I’m not able to see the settings used, or at least I don’t know how to view them. Basically I’m letting the ECU handle it after I picked them from the config list. They do seem to be doing better than the manual settings I had. I can check logs to figure out the idle pulse width.

Not sure if this is what you meant but I believe batch firing halves the injector pulse width. Meaning sequential injection will have a single injection event per cycle. Which I believe will be a longer pulse width compared to a batch fire. But please correct me if I’m wrong. If correct though would idle be easier with the larger injectors and sequential or half pulse width with batch injection?