Jump to content
HybridZ
RefreshRate

FPR and Fuel Pressure Help

Recommended Posts

So I am doing a Megasquirt EFI swap as well as a Turbo motor swap, using Green Giant 440cc injectors. I have a brand new stock replacement fuel pump already installed on the car, and I know the stock FPR is around 35-38psi if I remember correctly. What is the maximum fuel pressure the stock pump can put out? I am looking at getting a new FPR as I will need more fuel pressure for this setup, but I am trying to figure out exactly how much I will be needing and also if my stock fuel pump needs to be replaced in order to achieve higher pressure. 

 

Any suggestions on a good FPR would be great as well. (and fuel pump if needed) 

 

1.Can I use my stock replacement fuel pump?

2. How much fuel pressure should the turbo motor and megasquirt setup have? (green giant 440cc injectors, p90 head, dished pistons 7.31:1 cr, base tune of 220-230hp apox. will be tuned to 300whp)

3. FPR reccomendations? 

Share this post


Link to post
Share on other sites

1. 

Doubt it.     Have no clue, maybe at 40ish psi.

2.

Most injectors are rated at 43.5 psi. So if you use that it makes it easy for you, if you use 80psi your 440cc/min injectors flows ~600cc/min.

440cc (43.5psi)  into this (http://www.witchhunter.com/injectorcalc1.php) calculator seems to give a max HP of about 330hp crank (bsfc 0.65 ).

600cc (80psi)  into this (http://www.witchhunter.com/injectorcalc1.php) calculator seems to give a max HP of about 420hp crank.

Why not run as high as possible? I guess it's just put's extra load on pump, fittings and FPR. Not sure how much pressure stock system can take (hoses, filter etc). The fuel pressure is set by wit a knob on the FPR

3. 
Aeromotive are popular

Edited by turbogrill

Share this post


Link to post
Share on other sites
59 minutes ago, turbogrill said:

1. 

Doubt it.     Have no clue, maybe at 40ish psi.

2.

Most injectors are rated at 43.5 psi. So if you use that it makes it easy for you, if you use 80psi your 440cc/min injectors flows ~600cc/min.

440cc (43.5psi)  into this (http://www.witchhunter.com/injectorcalc1.php) calculator seems to give a max HP of about 330hp crank (bsfc 0.65 ).

600cc (80psi)  into this (http://www.witchhunter.com/injectorcalc1.php) calculator seems to give a max HP of about 420hp crank.

Why not run as high as possible? I guess it's just put's extra load on pump, fittings and FPR. Not sure how much pressure stock system can take (hoses, filter etc). The fuel pressure is set by wit a knob on the FPR

3. 
Aeromotive are popular

1. I have no problem with buying a higher pressure fuel pump, I just couldn't find what the stock one is rated at to see if it is needed in the first place. (What would be a good aftermarket alternative?)

 

2. Okay cool, that gives me a general idea of where I need to be at least. 

 

3.  Thats exactly what I was looking at, good to know. 

 

Thanks for your input, you've been extremely helpful! 

 

 

Edited by RefreshRate

Share this post


Link to post
Share on other sites
30 minutes ago, turbogrill said:

Where did you find that?

 

1.

So no, since 43.5psi minus boost_psi will be your max fuel pressure.

If you want to run 10psi boost your fuel pressure will have to be set at  32psi. Probably not enough with your performance goal. (maybe ~250hp)

If you need to maintain 43.5psi pressure on 10psi boost, you have to be able to flow fuel at 53.5psi.

Share this post


Link to post
Share on other sites
3 hours ago, RefreshRate said:

stock replacement fuel pump

What do you mean by this? Is it an OEM pump? Is it an aftermarket pump that looks like an OEM pump? Is it a universal aftermarket pump that looks nothing like the original?

Really you shouldn't be worrying about what the specs were for the stock pump, you should get the specs for the pump you actually have (from the manufacturer).

As others have said, whatever pump you have probably won't cut it once you account for boost pressure. I personally wouldn't risk it for something that is a fairly small cost in the scheme of turbo builds.

Share this post


Link to post
Share on other sites
Just now, ZHoob2004 said:

What do you mean by this? Is it an OEM pump? Is it an aftermarket pump that looks like an OEM pump? Is it a universal aftermarket pump that looks nothing like the original?

Really you shouldn't be worrying about what the specs were for the stock pump, you should get the specs for the pump you actually have (from the manufacturer).

As others have said, whatever pump you have probably won't cut it once you account for boost pressure. I personally wouldn't risk it for something that is a fairly small cost in the scheme of turbo builds.

stock replacement from a new manufacturer, looks identical to the original. I couldn't find any specs on what the fuel pump put out from the listing. 

Share this post


Link to post
Share on other sites

Also, at some point you will need to take a decision if you want to get steel braided or rubber hoses. 

 

You will see a lot of builds have steel braided, it looks cool and it's probably safer as well BUT it's harder to do right.

I spent a fortune on high quality steel braided and high end fittings, but I have 2 fuel leaks because I suck at fabbing the hose ends. 

Fresh rubber might have been better for me...

Share this post


Link to post
Share on other sites

Aeromotive 13129 EFI regulator will also work just fine, is a quality part and has a reasonable price.  

https://www.summitracing.com/int/parts/aei-13129/overview/

The stock FPR simply cannot handle the  Bypass return volume that a High Volume pump provides at idle and low RPM's.  Internal orifice is simply too small. At idle, with bigger injectors and a high volume pump you can be Bypassing 80 percent of the fuel volume back to the Tank. FPR has to be designed internally to handle this amount of flow and maintain a steady pressure. 

Many new cars use a PWM Fuel pump that reduces flow at low loads to aid in maintaining a properly regulated rail pressure.  

 

 

 

Edited by Chickenman

Share this post


Link to post
Share on other sites
On 11/14/2017 at 4:16 PM, turbogrill said:

2.

<snip>

Why not run as high as possible? I guess it's just put's extra load on pump, fittings and FPR. Not sure how much pressure stock system can take (hoses, filter etc). The fuel pressure is set by wit a knob on the FPR

3. 
Aeromotive are popular

You can run higher base pressures, and it can have some benefits for the spray pattern, but in general increasing pressure has a negative effect on the pump's ability to flow fuel:

Bosch_044_vs_Walbro_255HP_vs_Aeromotive_A1000EFI.JPG

Also, as others have already noted the stock na fuel pump has an internal pressure relief set at roughly 55psi, so increasing the base pressure will directly limit how much boost you can run with that pump.  As I recall the stock turbo pump's pressure relief was set to ~65psi.

Edited by TimZ

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


×