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Thread: 100% of fuel in BTDC is the 50/50 split a lie?

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    Advanced Tuner JaegerWrenching's Avatar
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    100% of fuel in BTDC is the 50/50 split a lie?

    Here is a link to a video of them trying 120% BTDC all the way down to 100% ATDC, i thought the rule was to stay away from anything over a 50/50 split? What do you other tuners have to say? https://www.youtube.com/watch?v=nemSh0cxsQc

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    Ummm, a CR 5.9 has plenty of cells that are 200+% before top dead center, even getting above 300% BTDC, in stock form. All these rules of 50/50 are junk to follow. I?ve seen so many people say don?t follow them, why people insist on following it is beyond me. Big name tuners don?t follow that junk. If anything, which you aren?t going to look inside and see, you want combustion burn just slight after top dead center, not injection pulsewidth but your combustion burn.

    On high engine load is where you want to be careful with exceeding beyond a 50/50 pulsewidth split if you want to follow it. Lower rpms you will easily hear if it?s being injected too soon, Upper rpms you most likely not hear anything if it?s too early till a connecting rod is pushed through your oil pan.

    A stock CR 5.9 max fueling and timing it can cleanly take is about 3200us pulsewidth and 32 degrees BTDC, this is above 60% BTDC. The upper end of rpm and load you would want to use a dyno to push things to the absolute max so you can watch what is happening with the torque.

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    That guys explaination on p pumps is horrible

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    Advanced Tuner JaegerWrenching's Avatar
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    Quote Originally Posted by Jim P View Post
    Ummm, a CR 5.9 has plenty of cells that are 200+% before top dead center, even getting above 300% BTDC, in stock form. All these rules of 50/50 are junk to follow. I?ve seen so many people say don?t follow them, why people insist on following it is beyond me. Big name tuners don?t follow that junk. If anything, which you aren?t going to look inside and see, you want combustion burn just slight after top dead center, not injection pulsewidth but your combustion burn.

    On high engine load is where you want to be careful with exceeding beyond a 50/50 pulsewidth split if you want to follow it. Lower rpms you will easily hear if it?s being injected too soon, Upper rpms you most likely not hear anything if it?s too early till a connecting rod is pushed through your oil pan.

    A stock CR 5.9 max fueling and timing it can cleanly take is about 3200us pulsewidth and 32 degrees BTDC, this is above 60% BTDC. The upper end of rpm and load you would want to use a dyno to push things to the absolute max so you can watch what is happening with the torque.
    That's what i thought, i'm at a 55/45 on my ford and it seems to run very clean and strong at 1280us, it is slightly noisy at 26-2800 rpm with 11.3* Dyno time incoming soon! Yes his his explanation of the P-pump is crap. How does the P pump stuff work? does it start it's injection at X degrees no matter the PW? or what would be it's PW since it's mechanical?

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    Timing on the p pump is static. Doesn?t change unless the gear were to slip or you yourself change it. I?m the pump is a rack that allows more or less pressure to build through the plungers to deliver more or less fuel through the delivery valves to go to the injectors. The more you push on the throttle the more the linkage moves the fuel rack in the pump to allow more into the plungers building higher pressure and more fuel flow. Timing never changes but volume through increased pressure delivers more fuel. It is pure crap his explaination of the p pump, it?s timing and fuel delivery.

    Here?s a very old school video from Bosch on the p pump.

    https://youtu.be/lig3L_F5Qo4