Thanks for the response, this is the exact type of answer I was looking for. If the factory lines are smaller than 5/16 then there is certainly flow gains to be made by upgrading to at least 5/16, and I'd have to imagine 3/8 (-6 AN) lines and hardware are cheaper.
DIY : PTFE line- tank to HPFP + inline fuel filter upgrade
- Thread starter Blaster3500
- Start date
-6an is used most common and by far the cheapest option to use and easy to obtain.
The biggest issue with the stock setup is the LPFP hardline on the fuel pump and inlet filter, the actual plastic fuel line is good for 550 to 600 hp
from what I seen.
The biggest issue with the stock setup is the LPFP hardline on the fuel pump and inlet filter, the actual plastic fuel line is good for 550 to 600 hp
from what I seen.
Oof. Any way around that one? All these little pieces that few people pay attention to are the real killers...
There is a few kits around I custom made my own.
I personally have not looked into any as I make my own fittings which get quite expensive.
I personally have not looked into any as I make my own fittings which get quite expensive.
So, just to confirm, is drilling the inlet hole for the fuel rail a benefit, or not?
I see that taking out the filter is a good choice to reduce restriction. Are there any negatives to drilling the supply hole in the fuel rail?
My setup - PR stage 2.5 LPFP > PR in-tank regulator and filter > PR lines >HPFP.
Thank you.
I see that taking out the filter is a good choice to reduce restriction. Are there any negatives to drilling the supply hole in the fuel rail?
My setup - PR stage 2.5 LPFP > PR in-tank regulator and filter > PR lines >HPFP.
Thank you.
I thought I saw a couple times in this thread that drilling the fuel rail should only be done if you have something increasing the flow from your HPFP, like a shotgun/PFS POD/Helix?
I helped a friend here reach his goal of 400rwk with no overdrive and only a stage 2 lpfp.
One of the main restrictions is the fuel rail amongst others, putting phenolic gaskets between the rail and head lowers the gas temp
and keeps the fuel denser so you dont have to inject as much and keeping the fuel pressure up.
Whilst all these gains are very minimal they all add up to around 5 to 10% gain in pressure when you are on the edge of running out of flow.
One of the main restrictions is the fuel rail amongst others, putting phenolic gaskets between the rail and head lowers the gas temp
and keeps the fuel denser so you dont have to inject as much and keeping the fuel pressure up.
Whilst all these gains are very minimal they all add up to around 5 to 10% gain in pressure when you are on the edge of running out of flow.
If you remove the filter on the rail you need to add an inline filter to replace it. Bmw put a filter there for a reason. You wouldn't remove any other filter on your engine for more performance now would you? Remember, not all inline filters are the same, many lie about their filtering ability and obviously you don't want this new in line filter to be much of a restriction. Buy a good quality in line filter that actually goes down to the correct microns of filtering ability. I forget what the stock one is, I am sure someone can chime in.
Removing the filter and drilling the rail is the old VTT trick they used to charge $400 for 5 minutes of work. They literally charged for this mod. Assfucks. Does it give you a tiny bit more flow? Yes. However if you 'need' this small amount of flow it means you are running your fuel system literally on the ragged edge.
Generally you want to leave at least 10% flow and 10% injector. What I mean is no one who is smart runs their injectors at 100% flow. You leave headroom. This is why every fuel injector calculator online it defaults to 10% headroom. You do the same with your HPFP LPFP etc. This is why the small gain from this mod is kind of meh. Sure do it and add in a quality inline filter but if you need this for your car to run right at WOT you are running way too close to the maximum capacity of the fuel system which in general is considered a very bad idea. You want headroom. You don't run a fuel system so you have zero headroom/capacity. One hiccup in flow and boom you go super lean pop a piston and there goes your engine. Same reason maxing out the stock DI is so dangerous. No one does it because it is asking to pop an engine.
Do the mod, do it right by adding in a inline filter, and then never run your fuel system at the limit. It is asking for trouble.
Removing the filter and drilling the rail is the old VTT trick they used to charge $400 for 5 minutes of work. They literally charged for this mod. Assfucks. Does it give you a tiny bit more flow? Yes. However if you 'need' this small amount of flow it means you are running your fuel system literally on the ragged edge.
Generally you want to leave at least 10% flow and 10% injector. What I mean is no one who is smart runs their injectors at 100% flow. You leave headroom. This is why every fuel injector calculator online it defaults to 10% headroom. You do the same with your HPFP LPFP etc. This is why the small gain from this mod is kind of meh. Sure do it and add in a quality inline filter but if you need this for your car to run right at WOT you are running way too close to the maximum capacity of the fuel system which in general is considered a very bad idea. You want headroom. You don't run a fuel system so you have zero headroom/capacity. One hiccup in flow and boom you go super lean pop a piston and there goes your engine. Same reason maxing out the stock DI is so dangerous. No one does it because it is asking to pop an engine.
Do the mod, do it right by adding in a inline filter, and then never run your fuel system at the limit. It is asking for trouble.
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The only thing one will be running at the limit is their hpfp, these injectors can handle 2 to 3x the flow the hpfp can provide and nothing else.
You are running at the limit of the hpfp which is a fuel pump and you never run ANY of your fuel pumps maxed out giving you 100% of the flow they can give with zero headroom for more flow. It is asking for issues, not if but when. You always leave headroom and never run any component at 100% with zero headroom. This is fuel injection 101.
The oem hpfp also are known to wear out and decrease their flow. Not what you want when you have it maxed out. Because you gave it zero headroom guess what happens then?
Leave a little on the table for safety. Or don't wtf do I care about other people's motors? Anyone reading this do yourself a favor and read up on fuel system design best practices. HINT: Maxing out a pump with no headroom is never suggested.
If more flow is needed adding a second pump is small money. If you run out of hpfp have your tunah back off the DI. Ask them to leave roughly 10% of the flow the hpfp can give on the table and then add PI. PI is less expensive then overspinning a hpfp. The general consensus is overspinning a hpfp works, but there have been major reliability issues, sound issues, leaking issues, etc. PI is the way. It also cleans your valves and removes the restriction which is the stock DI injectors.
The oem hpfp also are known to wear out and decrease their flow. Not what you want when you have it maxed out. Because you gave it zero headroom guess what happens then?
Leave a little on the table for safety. Or don't wtf do I care about other people's motors? Anyone reading this do yourself a favor and read up on fuel system design best practices. HINT: Maxing out a pump with no headroom is never suggested.
If more flow is needed adding a second pump is small money. If you run out of hpfp have your tunah back off the DI. Ask them to leave roughly 10% of the flow the hpfp can give on the table and then add PI. PI is less expensive then overspinning a hpfp. The general consensus is overspinning a hpfp works, but there have been major reliability issues, sound issues, leaking issues, etc. PI is the way. It also cleans your valves and removes the restriction which is the stock DI injectors.
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The hpfp is no problem at 100% as they can flow a lot more by overspinning them.
Running them at 90 or 100% will not make them last longer.
Nothing last for ever, you want to make power you have to sacrifice one way or another, even if you convert to pi only your sacrificing economy and drivability.
Running them at 90 or 100% will not make them last longer.
Nothing last for ever, you want to make power you have to sacrifice one way or another, even if you convert to pi only your sacrificing economy and drivability.
Just for clarity, at the end of the day you wouldn't be running your fuel system at max or beyond it's envelope unless your tuner had pushed it to those levels, correct? With these modifications it's not going to tax itself out unless the tune is pushing it that hard, right?
I'm working with Wedge on the final revisions to my tune, after I get some fueling issues sorted out, but I'd personally want to make sure he or any other tuner wasn't pushing my system to the ragged edge. I'm of the philosophy of if everything you bought says "built for 900hp" then you run it at 750.
I'm working with Wedge on the final revisions to my tune, after I get some fueling issues sorted out, but I'd personally want to make sure he or any other tuner wasn't pushing my system to the ragged edge. I'm of the philosophy of if everything you bought says "built for 900hp" then you run it at 750.
I wouldn't run any n54 block past 550hp, they are weak and only a ticking timebomb. You want a good reliable cheap base get a b58 and save your self the hassle.
Just bringing this back up from page 11 because now I'm confused. At different parts of this thread it's been claimed that drilling the inlet to the fuel rail will both benefit AND harm rail pressure...
The smaller hole in the rail is to stop drain back in the system when the car is off and nothing else.
It does not hurt rail pressure in any way.
It does not hurt rail pressure in any way.
What size are we drilling the rail inlet hole to? I've generally seen 1/16, but there's also a mention of 3/16 earlier in this thread, which is obviously much larger. Considering I have no plans to run an overdrive of any sort in the near future, what size is optimal? Also, IIRC we're not drilling the rail outlets that feed the injectors?
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Anything bigger than stock as long as it's nothing bigger to cut into the seat of the factory connection that will hurt the seal.
Pulled the rail yesterday to drill out the inlet and after seeing the seal, realized I could drill this thing out to like 1/4" if I wanted to. Anyways, ended up just doing 3/32" on the inlet and left the outlets to the injectors alone. For a bit of context, I'm currently tuning for an e30 blend and on my last 18psi pull the rail pressure dropped to about 900psi... clearly no bueno. Did a test run this morning to see if drilling the rail inlet on it's own would make any noticeable difference on pressure and on my first 3rd gear pull rail pressure didn't drop below 1800psi! For those doing the math at home, that's a 900psi gain in rail pressure! I was expecting a bit of a bump, but not literal doubling of the rail pressure at 7000rpm! Heck yes!
But drilling doesn't do anything, there is even a bigger restriction you might want to take care off, the lpfp sensor line but that requires a bit of fab work. If you leave it stock keep an eye on your lpfp pressures and get rid of the factory hpfp filter as that can cause starvation issues to your hpfp pump even though you have full lpfp pressure and cause premature failure of the pump.
