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I want to change my fuel filter/pressure regulator on my 2000 C5. But I'm reading that the fuel pressure and pressure stability on even the AC/Delco units aren't what they once were, quality wise. Has anyone here found this to be true? TIA........
What brand, and parts "stuff?" My tuner says there has to be an aftermarket pump in there, because there's no way a stock C5 pump, even with a boost a pump, could keep up with 600chp. My stuff under the hood is all aftermarket except the LS7 block and heads. Wondering if it's the regulator. It is an OEM C5 filter/regulator. No trouble with this setup@500whp. But Tony Mamo spec'd a bit hotter cam and reworked my LS7 heads. Plus I have a Vararam intake and airbridge on there now, rather than the stock C5 airbridge with a Blackwing filter before. This was all installed after the 500whp dyno run. Maybe I was at the ragged edge then, and this pushed me over, IDK......
Hmmm... In the past I made 500rw on a walbro 255lph with factory lines and whichever injectors came with the A&A kit.
The Z06 has a pair of walbro/ti auto 450lph non drain back pumps, LPE passenger pump fpr bypass, single 8an line through a Red Horse inline filter and forward to the AFPR behind the driver wheel we'll. I do not recall the brand but will look. The return comes off that AFPR as a 6an line. The rest goes 8an to the rails which flow from rear of driver around forward to termination at rear of passenger. This is the same way they run the lines from GM on the C7 Z06 so it seemed engineer approved and follows the laws of fluid dynamics.
Thank you. Anyone else have any experience on this subject?
Sure bud 27 years here tuning and setting up 500-2000hp fuel systems for daily drivers
What most people want but do not realize until later is, easy access to their fuel system components.
For example, a fuel pressure regulator under the hood, where it can be dealt with directly, adjusted, replaced, etc...
Long lasting components, use Aeromotive regulators and quality braided hose or EFI hose.
A 5/16" Fuel lines good to about 600rwhp in gasoline E10 applications. Hose clamps are simple and reliable / track legal, even hose clamped braided is track legal.
You want the lowest fuel pressure possible to reduce fuel heating, voltage drop. Low pressure also improves fuel pump flow rate, and will increase fuel pump lifespan. And less likely to leak.
I generally run 35 to 38psi of baseline fuel pressure in seq-efi port injected engines. Vacuum regulators are needed to drop that down to about 30 or 32psi at idle/cruise which greatly improves many aspects of the fuel system I Listed.
Mind you the setups I tune run 30 to 45psi of boost so a 35psi baseline is actually 75psi at wide open throttle in some apps, it gets very high when in demand.
Factory fuel systems often put the regulators in the fuel tank. This is bad for hobby level and performance applications because, A. non adjustable, B. no vacuum reference relaxation, C. unable to inspect/replace/maintain at a glance. So I do not generally allow people to keep their regulators in the fuel tank like factory unless its a very basic original setup I suppose. Its just a cheap garbage way of doing things, there is no performance or benefit to gain from that stock setup in the tank, it is all the wrong things for a reliable performance vehicle.
Oh yeah, I also have a doctorate in engineering. I keep forgetting that
Anyways on the fuel pump end, I don't know why people still use 255lph pumps. There are adequate Aeromotive 340lph pumps just as quiet (look up aeromotive stealth) which offer 500 to 600rwhp dynojet at 13v with 38psi of fuel pressure baseline on gasoline with 5/16" hose and 2000run hours. This is a traditional in-tank quiet pump for a generic performance vehicle running gasoline. Those 255 is kind of, 80's stuff, obsolete. They dont last longer, they aren't quieter, why use them?
Next the challenge of vehicle like corvette is fuel pump access. The tank is difficult. So what I generally will recommend, if possible, is a twin in-tank setup right off the bat. Put two pumps side by side, vibration resistant, well wired, use Mcmaster carr's gasoline/ethanol heat shrinkable crimp connectors and their highest quality corrosion resistant wiring for in the tank exposure. And you run the pumps on a switch, so today you use one, tomorrow you use the other one, never both at the same time (unless you are at the level 800rwhp alcohol or something). This way when one pump dies you have a backup and don't need to drop the tank. This mod generally only adds a small fraction of the price to the installation that it costs to R&R the entire fuel tank when the single pump dies, which, they all do eventually.
This also gives a chance to add the fuel return line for the chassis.
This is the correct way to do a hobby level daily driver performance application fuel system. Fuel return line + Regulator underhood + vacuum reference + lowest possible pressure + largest possible injector (ID1000 are my choice for 600-700rwhp gasoline because you can fit 700lbf-ft worth of fuel into the 300*-230* injection timing window post EVC)
This way now there are many solutions to any issues which arise, hoses are easy to replace & service thanks to traditional hose clamps, two pumps is one (two is 1 and 1 is none), regulator and lines are underhood easy to service and set as needed, yeah this is how its done.
Thanks for your input, Kingtalon. I have another question. Why the lower pressure vs OEM? I figured the higher pressure may help atomize the fuel. You apparently don't think so. We both know it takes x amount of fuel to produce 600chp, or 500, or 400, etc. Thus, my question. Isn't atomization and spray pattern more desirable at higher pressure? Or does it become redundant after 20-25lbs?
Thanks for your input, Kingtalon. I have another question. Why the lower pressure vs OEM? I figured the higher pressure may help atomize the fuel. You apparently don't think so. We both know it takes x amount of fuel to produce 600chp, or 500, or 400, etc. Thus, my question. Isn't atomization and spray pattern more desirable at higher pressure? Or does it become redundant after 20-25lbs?
We've got to take a full 720 degree perspective on this issue. As the engine rotates, 4-stroke, the intake valve is closed most of the time. So the fuel is going to puddle on the intake valve and vaporize, absorbing heat from the valve, especially anytime injector duty is over say 18 to 25%.
There is no significant 'atomization due to injection' in those cases. And even if you could, you wouldn't want it; If the fuel injector energy supplied could atomize fuel instead of the heat from the engine, then running rich won't pull heat out of engine parts on gasoline volatile fuels - In other words, the more pressure/atomization is used, the less heat of vaporization is available from gasoline to pull heat from engine parts it comes into contact with. Not good! Gasoline like other liquids can remove heat from parts but only if it comes into contact with those parts as a liquid first.
2. When the fuel and engine is very cold, there isn't much heat to vaporize the fuel, so it can wash down the cylinder walls and create poor engine performance, stumbles/misfires/etc... So as the engine is COLDER the time for injection is SOONER before the intake valve opens...
3. Because injectors are typically 'too small' from OEM (they achieve duty cycles above 30% frequently) The only viable OEM injection strategy is to place fuel onto the closed intake valve, otherwise its a risk of spraying into overlap, which almost always guarantees poor performance, fuel wasting/washing, awful fuel smell in the exhaust. This is more noticeable with long overlap periods... A stock spray injection angle with a long duration cam frequently produces complains from customers "The car bucks and bogs at low speeds" & "The car trailer hitches at highway speeds" & "The car smells like raw fuel most of the time".
On to aftermarket tuning and/or with way oversized injectors: Yes we can spray fuel post exhaust valve closed if you know what you are doing and willing to spray through overlap if/when the ECU(depends on the ECU) back calculates injection pulses that are longer than the intake stroke itself at high output... but you had better know what you are doing or it can have wear/tear long term issues with engine longevity/ health if fuel starts washing down cyl walls especially when the engine is cold. It can be even more troublesome when using alcohol fuels which seem to be more easily 'corrosive/oxidative/dilutive' to an engine/oil quality/oil system.
Some OEM Ecu allow you to move the timing based on conditions, but some like Gen3 GM do not. It can be a trade off for those.
here is a Haltech example showing how you can move the injection timing post EVC at high output To get a torque boost (just an example) And also back to post EVC Spray when at idle and low speeds to keep from smelling like fuel. The timing numbers are in BTDCC (before top dead center compression). So 440* is 440* before top dead center compression or a good 100 degres or so before intake valve opens.
I would argue that with my dying breath Boosted applications especially it is a VERY keen player - I have gained up to 120hp with injection timing alone on twin turbo setups below 3000 rpms Not to mention if when done correctly and at a linear retard rate with rpms IT WILL increase torque enough to rip the tires loose whereas it may not have before... Just takes some playing and getting right for the particular application.
This is a kind of, secret, because it has far reaching influence on engine health, and power output, and depending on the tuner and ECU you may trade one for the other sometimes. If you don't know what you are doing it can really screw things up. For educational purposes I will give a sort of summary
A. Spraying before intake valve opens = OEM strategy. Considered safe. Puddle fuel, vaporize fuel from valve, fuel becomes a gas before the intake valve opens. When engine is cold, spray happens much earlier. Never spray during overlap. Spray is back calculated generally from the latest possible spray before the intake valve opens. Spray pressure/atomization is not a factor in performance since the valve is closed.
B. Spraying after the intake valve opens = can be risky, but also may have benefits for large cam engines and certain types of intake systems. Air is a fluid and when fluid gains momentum, having a properly positioned injection spray burst can supplement that momentum/kinetic energy and increase engine torque. It depends how and where the injector is positioned and how its spray time *on* is tailored to work with the incoming air flow, or not. The spray can just as easily cause turbulence and lost momentum & lost power this way, stock engines may have losses because they do not depend heavily on flow momentum to fill a cylinder, stock tend to rely more on exhaust scavenging and intake suction (pressure drop from piston + exhaust to conserve energy = more economy).
It is an empirical investigation. Usually to see gains a very large injector is used to keep duty cycle down near 20 to 30% at wide open throttle so most of the spray can fit between exhaust valve closed, peak piston velocity, and bottom dead center (approx 320 to 220* BTDCC)
Pressure at < 100psi is not really a factor in any of this. If you had a competition where forced induction was forbidden and any fuel pressure could be used, you'd want say 500psi or 1000psi or something, it could be like a mini-supercharger having all that fluid blasting in at high pressure can help pull the airflow along. At our level of 40 to 80psi however the difference in energy input is negligible, instead the real key player is WHEN(timing) and for HOW LONG (duty cycle vs piston position) in conjunction with valve timing events can relieve poor drivability, fuel smell, and boost torque in the mid-range.
What is desired in reliability apps at high output is, reliability, so low fuel pressure = easy pump lyfe. Low fuel system stress. Long fuel system lifespan. Low heating of fuel and fuel related parts. And all of this also leads to increased fuel pump capacity for flow at high output which is safer. Setting up low pressure fuel systems can support high output with long life span. And all of the benefits of timing is still there - you time it right, use the right size injector, empirical test to find ideal trade offs depending on the ECU's capability. That is how you tune the fuel system really fully.
Since this is image heavy, I used Spoiler tags to have them all condensed.
So since about May Last year I have been looking for a better fix. The Radium Kit (LINK) was interesting. It used a 4Bar (58.2psi) OEM Grade Bosch Regulator with availability EVERYWHERE. Unfortunately, it was only rated for up to a 255LP which isn't great or common on this platform.
The Radium filter & their mount kit (Link) looked good until you realize there's no return & you also have to adapt from -10Orb to 3/8 Female which is difficult with one fitting but they do exist (linked later). This would be over a $500 setup from 2-3 vendors to have a 58.2psi regulator that was limited. Not great, but an option!
Spoiler
A good friend of mine went with a regulator from Racetronix (LINK) since he has their fuel system and their support about this product & further communication was poor. WILD since their fuel pump support was great from what he said.
Getting all the fittings and a filter for it was also a PITA as Racetronix doesn't sell a -6ORB to 3/8 FEMALE like the stock filter but I found one from Fore Innovations (LINK) that would also be needed on the Radium Setup. We rigged it so the fuel would go into his filter, then the regulator & return off the bottom of the regulator after trying the regulator being pre-filter and there wasn't really a change.
They mentioned they had a Corvette style Filter coming out (LINK) but it's still not available & they wouldn't provide pictures or any ETA other than 2026. So we plumbed theirs up and it worked well but now after 3000 miles and 1 track event it's already low & from what he's been told, non-servicable FPR. They also then told us it shouldn't be under the car in it's factory location AFTER recommending it in that area. So we plumbed it near the brake Booster & still had issues.
His car has their highest volume pump without a Boost-A-Pump, a High Compression LS1, Stage 4 Cam, High Idle and it's not a far comparison to say a stock car with this & a normal Low-Pressure in tank pump, but they also took 3 weeks to return 12 calls and 6 emails soo.....
Spoiler
After that, he went for the Radium adjustable regulator with their mount (Link). The Direct Mount regulator on their website unfortunately doesn't work as a "Dead Head" style regulator in the engine bay as their support staff said, so he had to run a fuel line from front to back of his car but I expected as much. It works well, but if you key off you do have to key on and prime the regulator a bit since it's at the engine bay & drops pressure nearly instantly from a key off. Great from a safety standpoint and most of the hot fuel dumps back into the tank. He did revise his tune from the other regulator and made more power with the same fuel pressure but that could be other variables as well.
Spoiler
NOW we are on the cusp of an actual easy button solution.
Deatschwerks has a DWFFR-X (Link) which goes in the stock locations & is setup to be a simple plug and play fix with a serviceable FPR & easy to service 10 micron filter with your choice of size.
MY ONLY issue with it is their website doesn't have a proper 1 click solution. We need a 3/8 Male SAE Quick Connect to 8AN Orb for the Inlet, a Male 5/16 SAE Quick Connect Outlet to 6AN Orb for the return, and a 3/8 Female SAE to 10AN Orb for the Outlet to go to the factory connections.
But it's the most affordable & simple solution. I've emailed Deatschwerks Support about trying to get a All-In-One option on their website.
We have lots of options, but in my opinion this is the easiest option especially for stock ECU cars or things that don't need a vacuum reference fuel regulator.
I bought a Wix from Summit last year. It was $70. Fuel pressure was 90psi.
Wix sold out and now buys from whatever cheesy manufacturer will build them. Junk. Maybe you get lucky?
All sorts of folks make these. I think all are junk.
If I ever need one for my C5 I’ll engineer a separate regulator and filter setup.
New C5 fuel filter/pressure regulators
Boosted applications especially it is a VERY keen player - I have gained up to 120hp with injection timing alone on twin turbo setups below 3000 rpms 
