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Out of pump, injector, or both.

Old 09-11-2018, 02:48 PM
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Default Out of pump, injector, or both.

Setup is cam only sbe ls1 procharger and 10 pounds. Fuel is E70. Pump is external Magnafuel 4301. Injectors are deatschwerks 95 lb/hr but actually flow 89 lb/hr at the 43.5 base pressure I知 running. I知 at 95 percent duty cycle at 6600 rpm. I still have the evap system plus a -8 tip over vent in the tank. Magnafuel didn稚 like the hard 90 I have before the pump and recommended a hose bend 90 so I値l do that. I want to run a couple more pounds so curious if I should go to a 4303 pump or if I need injectors also.


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Old 09-11-2018, 03:18 PM
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If you are at 95% duty cycle already, I would highly recommend upgrading your injectors if you want to run a couple more pounds. Shoot me an email if you have any questions! [email protected]
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Old 09-11-2018, 04:08 PM
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Originally Posted by AUS Injection View Post
If you are at 95% duty cycle already, I would highly recommend upgrading your injectors if you want to run a couple more pounds. Shoot me an email if you have any questions! [email protected]
Should I really be at 95 percent duty cycle with 89 lb/hr injectors on E70 fuel at an estimated 550 to 600 rwhp?
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Old 09-11-2018, 05:42 PM
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Originally Posted by BCNUL8R View Post


Should I really be at 95 percent duty cycle with 89 lb/hr injectors on E70 fuel at an estimated 550 to 600 rwhp?
At that horsepower, your injectors should be just fine, and shouldn't be at 95%
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Old 09-11-2018, 06:11 PM
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Originally Posted by AUS Injection View Post
At that horsepower, your injectors should be just fine, and shouldn't be at 95%
That's kind of what I suspected, but thought I'd ask to make sure. It's got to be the pump maxed out or a restriction. I've got -10 from tank to pre filter with that hard 90 into filter. Then -8 out post filter all the way to rails in series. My crossover is only -6 though because I used the supplied oring fittings. The regulator is Magnafuel 9950-B and using the stock feed as a return.

So I will plan on improving a couple restrictions and have the Magnafuel 4301 rebuilt to a 4303.
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Old 09-11-2018, 06:38 PM
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Originally Posted by BCNUL8R View Post
That's kind of what I suspected, but thought I'd ask to make sure. It's got to be the pump maxed out or a restriction. I've got -10 from tank to pre filter with that hard 90 into filter. Then -8 out post filter all the way to rails in series. My crossover is only -6 though because I used the supplied oring fittings. The regulator is Magnafuel 9950-B and using the stock feed as a return.

So I will plan on improving a couple restrictions and have the Magnafuel 4301 rebuilt to a 4303.
Yes sir its gotta be your pump
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Old 09-11-2018, 08:54 PM
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Increase your base fuel pressure and see if duty cycle goes down. If it does, its your injectors. If it doesn't, its your fuel pump.
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Old 09-11-2018, 09:08 PM
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Originally Posted by JoeNova View Post
Increase your base fuel pressure and see if duty cycle goes down. If it does, its your injectors. If it doesn't, its your fuel pump.
Nice trouble shooting tip thank you.
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Old 09-14-2018, 04:28 PM
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or just monitor fuel pressure....if it's dropping, it needs fixed.
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Old 09-24-2018, 03:33 PM
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dido, get your pressure at the rail onto your logs. you might be supprised that you are dropping pressure.

is your injectors a flat base with a boost ref fuel pressure regulator? you need to log fuel pressure to ensure that your fuel pressure rises 1:1 with boost
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Old 09-29-2018, 10:27 AM
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Originally Posted by AUS Injection View Post
Yes sir its gotta be your pump
The 4301 supports up to 1500 hp and the 4303 supports up to 1700 hp. Read that 4301 is not continous duty but the 4303 is continuous duty. It only requires 12 amps, but couldn't find voltage requirements. The injectors support more than 600 hp.

So when you say "it's gotta be the pump", do you mean it is failing (not a continuous duty pump) and can't maintain maximum pressure and volume anymore?

Is the pump getting 13.5 volts at the pump at 6600 rpm, or perhaps a drop-off of voltage or amps to the pump at 6600? A lot of stock alternators drop off at 6200 rpm (or 18,500 rpm at the alternator) dependent on pulley combination (crank pulley and alt pulley). At what rpm does duty cycle raise to 95?
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Old 10-12-2018, 07:48 PM
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Originally Posted by dlandsvZ28 View Post
The 4301 supports up to 1500 hp and the 4303 supports up to 1700 hp. Read that 4301 is not continous duty but the 4303 is continuous duty. It only requires 12 amps, but couldn't find voltage requirements. The injectors support more than 600 hp.

So when you say "it's gotta be the pump", do you mean it is failing (not a continuous duty pump) and can't maintain maximum pressure and volume anymore?

Is the pump getting 13.5 volts at the pump at 6600 rpm, or perhaps a drop-off of voltage or amps to the pump at 6600? A lot of stock alternators drop off at 6200 rpm (or 18,500 rpm at the alternator) dependent on pulley combination (crank pulley and alt pulley). At what rpm does duty cycle raise to 95?
The 4301 is a continuous duty pump and supports 1500 hp on pump gas naturally aspirated at carb pressures. No way it's going to support 1500 on E85 at EFI pressure in a boosted application. I never go below 13.7 volts and the injectors hit 95% duty right at the shift point 6550 rpm. I had the pump rebuilt to 4303 specs and is back on its way to me. For reference the 4301 is done around 600 rwhp through an auto trans on E85. The 4303 should cover me to my goals.

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Old 10-15-2018, 10:41 AM
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Let us know how it works out when you get it going!
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Old 10-16-2018, 04:51 AM
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Originally Posted by AUS Injection View Post
Let us know how it works out when you get it going!
It's together running now, but all the tracks are closed for the winter. I don't think it will leave the garage again until next spring.
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Old 10-16-2018, 11:39 AM
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dang it
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Old 11-22-2018, 06:45 PM
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What's the micron rating on the pre pump filter?
What's the voltage AT the pump?
Have you done volt drop testing on both sides of the pump?
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