AFPR - What is your fuel pressure set at?

[Garage_Defeat]

All you guys with an adjustable fuel pressure regulator, what is your fuel pressure set at Opsi boost (no vacuum or boost), at idle with vacumm (-16-20 psi vacuum) and at full boost (if you have been able to watch fuel pressure at full boost on a dyno, or have a cockpit gauge)? I just installed a Aeromotive FPR on my gvr-4. It has the 255lph HP fuel pump and is rewired, so it is running at full capacity. I figure that i should set it way lower because the 255 HP is flowing a lot more even at lower fuel psi compared to a stock fuel pump and regulator. Post your numbers please.

Thanks,

-DaN
1991 Galant VR-4 (E39A)

 

Also I would like to add to this. Does anyone have a rising rate adjustable FPR? Where the pressure is the same until the boost comes in.

 

Ok, I've got a Malpassi Rising rate reg. Last time on the dyno it was set at 45psi base pressure & at full noise it only made about 65psi (20psi boost) and trailed down to 60psi at 6500. Obviously my fuel pump isn't big enough cause in theory it should have been about 70psi under full load.
I've since dropped it back to 37psi base as my AFR was 10:1 anyway and only went to maybe 12.9:1 when it dropped down, though I haven't got back on the dyno since.

Under vac at idle (18 InHG on boost guage) it reads 27psi now (with 37psi)and read about 32psi when I had 45psi base pressure.

Moral of the story? I need a bigger fuel pump again to get more out of the 550's.

 

That sounds pretty close to stock dude. I heard that our FPR's raise the fuel pressure 1psi for every 1psi of boost. So if base is 45psi (close to stock I think) and your running 20psi, 20 + 45 = 65psi fuel pressure. Someone tell me if this is right. The RRAFPR I have is based of the Cartech unit and will not alter base FP.

 

Our stock reg's base pressure is 37psi, and I think the pump is stopping my rising rate reg from working properly

 

Factory spec is 36-38 psi base pressure (without the vacuum line connected), 27 psi with vacuum, and 1 psi added to the base pressure per pound of boost. You can run a higher base pressure if you're trying to get a little more out of your injectors, but this relationship should always remain the same: 8-10 psi lower with vacuum, and 1:1 added to base pressure with boost.
The reason for this is simple (and I've explained it here before): the pressure DIFFERENTIAL across the injector should always be the same. So, if you're running 37 psi base, there will ALWAYS be 37 psi across the injector. Think about it, the tip of the injector is in the intake tract, so if the FPR doesn't add 1 psi of fuel pressure per lb of boost, the injector would actually flow less, because of the boost pressure its fighting against.
The ECU's maps are based on the 1:1 FPR. Use a rising rate FPR, and all this theory goes out the window.
By the way, I run 43 psi base pressure with my 550's, which gives me about 36 psi with vacuum, and 60 psi with 17 lbs of boost. I have a 2g MAS, and that gets me closer to 100% fuel trims.

 

quote:Originally posted by ken inn:
AHA! you're at 43 base? wtf is your low(1k) set at? mine WAS at stock(37) and i had to lean the crap out of it(-19) to get the o2 trim to settle down. then, when it drops to idle, it goes really rich. i even backed out the screw flush, which helped, but then i did the rewire, and fp jumped up to 30 with vacuum. i had to retune to -21. Well, Ken, at the moment I'm not even running an AFC. I've been trying to tune the car without it. I'm probably not a good one to ask anyway, because, as I think I told you, even with the higher fuel pressure I have to richen things up quite a bit on the mid and high rpm's. My 550's just aren't flowing like 550's, so I don't know whats going on. I hate to go out and buy another set of 550's just to compare. I've tried running several different injector cleaners, including BG's good stuff, but it still is too lean. The FPR seems to be working right, as far as I can test.

 

[ken inn]

what is the brand of the "550's"?

i have tried every cleaner out there, nothing comes close to removing them, ultrasound, backflush, and cleaning machine. every one has come up about 20%, except the lucas ones. there was a couple of lucas 550's that were more like 5550's. scary.

 

They're Seimens/Deka I believe. The ones Hahn calls "625cc". HaHa. They are 55lb, which should be about 575cc. But, when I have to keep adding fuel, something isn't right.

 

I've heard from a bunch of Honduh people that that particular brand tends to flow less than they're rated for. I have no personal experience.

 

[ken inn]

AHA! you're at 43 base? wtf is your low(1k) set at? mine WAS at stock(37) and i had to lean the crap out of it(-19) to get the o2 trim to settle down. then, when it drops to idle, it goes really rich. i even backed out the screw flush, which helped, but then i did the rewire, and fp jumped up to 30 with vacuum. i had to retune to -21.

 

[Gabor]

quote:Originally posted by keydiver:
They're Seimens/Deka I believe. The ones Hahn calls "625cc". HaHa. So I've been driving around with these, thinking they are 660's for the last 5 years.
It ran it on a 2G with a hahn 20G, front mount, etc, AFC setting on high was -30% 12.1@111
My EGT's where always to the roof no matter how much fuel I added. If it was set at anywhere higher than -30% my trap speed get slower.
I hated that bastard from day 1 and now I find out he sold me 550's for 660's Arrgh.

I might have to get a set of real 660's now for my new setup.

Gabor
692/1000

 

quote:Originally posted by sleeper:
So I've been driving around with these, thinking they are 660's for the last 5 years.
I might have to get a set of real 660's now for my new setup.

Gabor
692/1000 I can't speak for the Hahn 660's. I'm only familiar with the "625's". I think he also had some "800"cc injectors, which are probably only 720's. His logic is that the Siemens injectors are good to at least 95% duty cycle, instead of the 90% maximum alot of injectors start to malfunction. I don't think that can explain false advertising.