Fuel system base pressure - How low is too low?
Thread Starter
Joined: May 2012
Posts: 1,796
Likes: 59
From: Elm Creek, NE
Fuel system base pressure - How low is too low? Hanging my setup up a little, bought a vs racing billet s480 clone and Bosch 210# injectors. Obviously, that's a ton of injector, and way more than I need. But I'm not spending thousands on injectors. These work and work good.
Anyways, my system consists of twin Bosch 044's, both on an 8an separate feed from a sumped cell, y after pumps to a single then y back out at the back of the rails, pass thru rails and runs to the reg then back home to the tank.
Could I drop my base pressure to say, 30psi (1:1 boost reference) and stretch out my pumps some and that would make the injectors smaller also.
Would that effect spray pattern/atomization?
Hoping to make around 900whp on e85 with twin 044's.
Anyways, my system consists of twin Bosch 044's, both on an 8an separate feed from a sumped cell, y after pumps to a single then y back out at the back of the rails, pass thru rails and runs to the reg then back home to the tank.
Could I drop my base pressure to say, 30psi (1:1 boost reference) and stretch out my pumps some and that would make the injectors smaller also.
Would that effect spray pattern/atomization?
Hoping to make around 900whp on e85 with twin 044's.
9 Second Club
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Joined: Apr 2009
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From: Joliet,IL and Las Vegas 50/50
I've got 2000cc injectors and run a 37psi base pressure with a 1:1 regulator. It has fueled me fine thus far and I think i'm above that whp number. Not sure though since haven't been on a dyno in a long time. I'm running dual 340 pumps (Need to install my 450's) and log fuel pressure just to make sure I'm not seeing a drop.
Running 43.5 base with 210's and ~70% IDC is close to 1000hp and 155MPH @ 4k lbs on E85. Much above 900hp or 150MPH the Eliminator pump starts to drop pressure, with a BAP increasing voltage it keeps pressure solid. Your dual 044 will flow about the same amount as the Eliminator so I believe you'll be fine for 900 but keep going above that in mind.
9 Second Club
Joined: Nov 2003
Posts: 13,616
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From: Norn Iron
Hanging my setup up a little, bought a vs racing billet s480 clone and Bosch 210# injectors. Obviously, that's a ton of injector, and way more than I need. But I'm not spending thousands on injectors. These work and work good.
Anyways, my system consists of twin Bosch 044's, both on an 8an separate feed from a sumped cell, y after pumps to a single then y back out at the back of the rails, pass thru rails and runs to the reg then back home to the tank.
Could I drop my base pressure to say, 30psi (1:1 boost reference) and stretch out my pumps some and that would make the injectors smaller also.
Would that effect spray pattern/atomization?
Hoping to make around 900whp on e85 with twin 044's.
Anyways, my system consists of twin Bosch 044's, both on an 8an separate feed from a sumped cell, y after pumps to a single then y back out at the back of the rails, pass thru rails and runs to the reg then back home to the tank.
Could I drop my base pressure to say, 30psi (1:1 boost reference) and stretch out my pumps some and that would make the injectors smaller also.
Would that effect spray pattern/atomization?
Hoping to make around 900whp on e85 with twin 044's.
And a few people have mentioned before that 044's arent always happy long term with ethanol fuels.
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If you look at a 210's "spray pattern" It's non existent. It's a gas injector, not designed for fluids. You get a squirt gun "spray pattern".
Honestly I'd bet you could pull a Denmah and run it at 40-50psi base and not even boost reference it. I believe Denmah was around 900whp and 56% DC at 60ish psi of total fuel pressure with the 210's. (assuming his sensors are correct, they do bounce around alot)
Honestly I'd bet you could pull a Denmah and run it at 40-50psi base and not even boost reference it. I believe Denmah was around 900whp and 56% DC at 60ish psi of total fuel pressure with the 210's. (assuming his sensors are correct, they do bounce around alot)
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Stock programming is often injecting fuel to a closed intake valve where it may puddle and evaporate, or at least warm up before entering the cylinder. Using a stand-alone we might adjust the fuel injector to spray after the valve is open- the possible bad effect of poor fuel injector spray can show up when we choose to spray to an open valve- possibly washing the oil from the cylinder walls or providing poor vaporization character. I would say if you are using a large injector, then for lower RPM you would want a pre-valve opening spray, and increase (advance) as the engine rpm increases and more airflow is available to whip the fuel spray into a gaseous state. Large cam engines are often setup to inject just after exhaust valve close to avoid overlap, on the other hand.
TECH Fanatic
Joined: Oct 2015
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From: Pittsboro, IN
Regarding the spray patter discussion. I have two fuel pumps, while cruising if I kick the 2nd pump on my fuel pressure will go up 2-3psi and it will lean out about 0.5 AFR. Thought that was interesting.
I get that at idle as well. Adding pressure often leans the mixture out at low pulse widths. Something to do with low pulse widths and high pressure slowing the inj. opening times I believe. Defiantly does the opposite and any decent DC %.
Last edited by Forcefed86; Jun 21, 2017 at 11:41 AM.
Thread Starter
Joined: May 2012
Posts: 1,796
Likes: 59
From: Elm Creek, NE
43 is the standard minimum for decent a decent spray pattern. Higher is better. Since you have a squirt gun for an injector I don’t think it will matter much personally. Set base at 30-40 with the reference line attached. Start low boost wise to make sure you have plenty of DC cushion. At 30 psi a 210 acts like a 174ish lb injector. Dropping the ethanol percent down to 50-70 range also helps extend the fuel system a lot.
Thread Starter
Joined: May 2012
Posts: 1,796
Likes: 59
From: Elm Creek, NE
Thanks for the information man! While I have your attention, in this car I'm building et should have about a 3000# raceweight. Full Calvert suspension th400/brake. I'm thinking I'm going to go with a 3.0 gear in the rear. You think that would be too much?
Thread Starter
Joined: May 2012
Posts: 1,796
Likes: 59
From: Elm Creek, NE
I plan to street/no prep more than prep racing, I hAd a lower power combo in a heavier car with the same trans and 3.31 and it wouldn't even think about hooking on the street on a pro bracket radial. Thought if I get my slr down it would help there.
I set my buddies Holley Reg to 40 when I installed FIC 1650's.
i had to move the set screw nearly completely out.
Problem was, the diaphragm stuck there and pressure wouldn't rise with boost.
so something to watch out for
i had to move the set screw nearly completely out.
Problem was, the diaphragm stuck there and pressure wouldn't rise with boost.
so something to watch out for