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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’m running. I’m 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’t like the hard 90 I have before the pump and recommended a hose bend 90 so I’ll 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.
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! Justin@AusInjection.com
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! Justin@AusInjection.com
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%
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.
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.
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
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 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.
Update for those that offered tips and were curious how it worked out...
It was a long hard winter so I wasn’t able to do much testing until now. So I went ahead and had my 4301 pump rebuilt to a 4303. I replaced my -6 fuel rail cross over with -8 so everything from the pump to regulator is -8 minimum. Still using -10 from tank to pump, but replaced the hard 90 before the pre-filter with a hose bend that seems way less restrictive. Went ahead and put a smaller pulley on the blower as well. I left base pressure at 43.5 to start with, but seeing 14 psi at 6800 rpm I was hitting 100 percent duty cycle. I raised fuel pressure base to 50 and adjusted the tune accordingly. That dropped duty cycle dramatically and I’m still a little rich in boost while still having the ability to raise fuel pressure to the normal 58 if I choose to.
Ok I spoke to soon. Trying to add more boost, but already hitting 100 percent duty cycle. I’m at an estimated 650 rwhp with E70. Magnafuel said check filters. They look good, but I went ahead and ordered new ones just to rule that out. Here is a video I made of the fuel flow from the rails while jumping the relay to run pump. Pump tested 13.5 volts at the pump. I also gave it a few revs with my fiancé watching to verify the regulars jumping up fuel pressure when it hits boost which it did. 55 psi base, about 48 at idle and jumped up to about 58 psi with a rev. I don’t currently have a way to log fuel pressure in hptuners, but voltage never goes below 13.7 in the log. Injectors are 95 lb/hr at 43.5 psi my set tested at 940 ish cc/min so not drastically lower that advertised and well matched.
09-11-2018, 01:48 PM
Out of pump, injector, or both. 
dang it 
