Setting Fuel Pressure

[thedugan]

Trying to figure out what fuel pressure to set my regulator at.

I have 55pound injectors on my SB383 blower motor. Its a procharger D1SC that will run at 12psi.

I do not want to use the boost port on the regulator as its mounted in the back near my tank and I'd rather let the Fuel map add pressure as needed.

So two questions.

What should I set the fuel pressure at?
Is it a good idea to use the fuel map or should I use the boost port?

[camcojb]

Trying to figure out what fuel pressure to set my regulator at.

I have 55pound injectors on my SB383 blower motor. Its a procharger D1SC that will run at 12psi.

I do not want to use the boost port on the regulator as its mounted in the back near my tank and I'd rather let the Fuel map add pressure as needed.

So two questions.

What should I set the fuel pressure at?
Is it a good idea to use the fuel map or should I use the boost port?

if you don't use a boost reference you'll want like 55-60 psi ( late model LS are 58 psi stock), due to the intake pressure fighting the fuel going into the port. In other words, if you set it to the normal 43 psi and run 15 psi you'll end up with a net 28 psi of fuel out of the injector. May not be exactly that way as there's other factors, but should disrupt the fuel spray pattern I'd think.

I run a rear mounted regulator and as an experiment I ran some silicone hose as a boost reference to the rear regulator; everyone thought there may be tuning issues, fat a/f coming off boost, etc. but it ran fine. I'll likely keep it. I now run 45 psi at idle, and 62 psi under 15-16 psi of boost.

Jody

[thedugan]

cool
im running a aeromotive bypass near the tank and I already ran the line but did not hook it up.

[thedugan]

im thinking of setting the fuel pressure at idle at 45 and then going from there. so it will add pressure as the motor adds boost right.

[camcojb]

im thinking of setting the fuel pressure at idle at 45 and then going from there. so it will add pressure as the motor adds boost right.
yes.

[MonzaRacer]

Best go high and drop down as needed rather than going light and being lean, and hope you have a wideband O2 sensor.

[INTMD8]

With a forced induction application it is always best to run the fuel pressure regulator boost referenced. Also the regulator should be mounted up front/under the hood as it cannot overcome pressure drop across the feed line when mounted in the back. (meaning you may not get a true 1-1 increase in fuel pressure with boost)

[camcojb]

With a forced induction application it is always best to run the fuel pressure regulator boost referenced. Also the regulator should be mounted up front/under the hood as it cannot overcome pressure drop across the feed line when mounted in the back. (meaning you may not get a true 1-1 increase in fuel pressure with boost)


Just an FYI, I like rear-mounted regulators and almost always run boost. I have not been running a reference line, but always had plenty of injector and ran more than normal pressure.

With my latest twin turbo I still have the rear-mounted regulator but added a reference line just to see. 15 psi of boost added almost exactly 15 psi of fuel pressure, and I didn't notice any tuning issues or hiccups due to the length of the line required to reach it.

So far it's worked fine for me, but I'll do more testing first. I've always heard the same as you, the length of the line will cause issues. Probably more critical in a max effort build, but in the 1000 hp range it seems to work fine.


Edit: I'm not following you around here, I just noticed I replied to another of your posts...................:cheers:
Jody

[INTMD8]

It seems then that at your hp level you have a large enough feed line to see zero pressure drop.

I guess another way of putting it is your fuel system will carry you further with the regulator mounted near the engine.

Say you have 58psi base pressure at the rear mounted regulator and flow enough fuel to the front of the car you may get a loss of pressure at the rails due to pressure drop across the line.

You may still get a pressure drop across the line with a front mounted regulator but it is not "seen" by the engine as the regulator is near it.

Just my opinion and they way I like to do things. Boost referencing the regulator will also give you much more range on the fuel injectors, allowing the use of a smaller injector with better driveability.

[camcojb]

It seems then that at your hp level you have a large enough feed line to see zero pressure drop.

I guess another way of putting it is your fuel system will carry you further with the regulator mounted near the engine.

Say you have 58psi base pressure at the rear mounted regulator and flow enough fuel to the front of the car you may get a loss of pressure at the rails due to pressure drop across the line.

You may still get a pressure drop across the line with a front mounted regulator but it is not "seen" by the engine as the regulator is near it.

Just my opinion and they way I like to do things. Boost referencing the regulator will also give you much more range on the fuel injectors, allowing the use of a smaller injector with better driveability.
I switched to rear mount regulators for two reasons. One, simplicity. Two, because of fuel heating issues which many have experienced with large pumps and a front mounted regulator.

Until it doesn't work I'll keep using it. I don't build anything that doesn't run on pump gas, so no max effort deals. I build them to drive long distances so fuel heating is an issue. I limit them to 1000 hp or so, and it seems to work fine at those levels.

On a max effort build I would run a front mount regulator, but they don't have fuel heating, longevity, pump gas to deal with.

Jody

[INTMD8]

Sure, I'm not saying it cannot work, just saying the way I prefer to do it based on my experiences.

Also, I've never tested fuel temps with either setup but I would be curious to know the difference. I think a step down box, or triggering the 2nd pump so total fuel recirculation is reduced would have more effect on fuel temps than regulator position.

With it rear mounted you are not recirculating fuel that has been through the hot rails but you also have much more stagnant fuel in the rail which may or may not have time to reach the same temp.