Fuel Injector Help

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digginfool
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Fuel Injector Help

Postby digginfool » Wed Feb 21, 2018 9:02 pm

Ran Diacom on my engine again today and once again I've found a very disconcerting data point. The pulse width for my fuel injectors is hitting 23 ms. This is way too much as the maximum these injectors should see is 18 ms (they are rated at 54 lbs/hr). As much as I despise the MEFI system, I have determined that it is also a self-learning system, although on a much slower (and probably lower) scale than other systems available. This over-working of the injectors could be why I've had a failure already. Is there a step up from here that would integrate with my current tune? 60 lb? 64 lb? I would be hesitant to jump to 80 lb injectors. Sure would appreciate some guidance.
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Smuggler
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Re: Fuel Injector Help

Postby Smuggler » Thu Feb 22, 2018 7:04 am

Anytime you change the injector size you should modify the tune. Most of the CTS-V guys that run the LS9 cam and a pulley change like running the ID850s. They claim the ID850s are the smallest injectors they like to run with the LS9 cam and pulley swap. Those injectors come with the accurate characterization tables for GM PCM tuning. If it was me I would put the ID850s in it and have Jeremy Formato tune it. He is a tuning genius and really knows the LSA. Also he comes to your area to tune a lot. You could catch him while he's down there and save yourself a trip to Tampa..

loudmouse
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Re: Fuel Injector Help

Postby loudmouse » Thu Feb 22, 2018 7:24 am

Diggn, if you have the ability to adjust fuel pressure, keep adding pressure until the ms comes down. But something is wrong here. No reason the injectors gm supplies with the engine wouldnt be enough. Maybe they need cleaning, or fuel filter plugged, or u have low fuel pressure, fuel line too small, roll over valve still in fuel line from manufacturer?
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

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Scarecrow
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Re: Fuel Injector Help

Postby Scarecrow » Thu Feb 22, 2018 7:48 am

Diggin, you should look into a low maintenance kayak.

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Smuggler
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Re: Fuel Injector Help

Postby Smuggler » Thu Feb 22, 2018 8:18 am

loudmouse wrote: No reason the injectors gm supplies with the engine wouldnt be enough.


He swapped the LSA cam for the LS9 cam. That in its self pushes the duty cycle limits of the injectors GM specked for that combo. Now throw a supercharger pulley swap into the mix and your flirting with disaster because now we need even more fuel.. it’s a whole safer on the engine when we don’t push the designed duty cycle of the injectors. Of course this is all IMO...

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digginfool
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Re: Fuel Injector Help

Postby digginfool » Thu Feb 22, 2018 8:18 am

loudmouse wrote:Diggn, if you have the ability to adjust fuel pressure, keep adding pressure until the ms comes down. But something is wrong here. No reason the injectors gm supplies with the engine wouldnt be enough. Maybe they need cleaning, or fuel filter plugged, or u have low fuel pressure, fuel line too small, roll over valve still in fuel line from manufacturer?


Fuel pressure is staying at or above 60 psi all the way to WOT so I don't believe there's any restrictions. I do have an adjustable regulator so that may be worth a try. I know from the research I've done that the stock injectors are at their limit at 675 HP, which is right about where my engine would be with a perfect tune. Super Chevy did a 2 part series on extracting power from the LSA and they put in larger injectors right after the level on the conversions I've done. At 24 ms, the injectors are firing continuously which may be leading to false AFR readings. I'm pulling plugs today to check what they look like. In any event, everything I've read says ideally, pulse width should be in the 15 - 18 ms range and anything above that means you need bigger injectors. However, I slept in my own bed last night and I'm missing out on all that Holiday Inn Express empowerment. 8) Always open to suggestions.
“When plunder becomes a way of life for a group of men living together in society, they create for themselves in the course of time a legal system that authorizes it and a moral code that glorifies it” - Bastiat

loudmouse
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Re: Fuel Injector Help

Postby loudmouse » Thu Feb 22, 2018 9:37 am

Forgot about the cam an pulley change. It needs to be tuned and maybe the injectors changed. The self learn will only adjust the tune based on parameters previously set an these parameters maybe correct or maybe not for the application. How many times are the injectors firing per cycle? This makes a big difference on duty cycle of the injector. Mine is set at 4 times per cycle. Depending on size and required fuel, you could run out of time between cycles. The tune needs to be redone for your application and not rely on the autotune.
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

Life is short, eat your dessert first! :downtown:


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