fuel system upgrade

[benjimatt]

So I just need a couple of suggestions.

I want 500hp to be my goal. 550 at most.

I will be running e85 with 1600cc or 1400cc injectors

Also Ill be running a 255hp in-tank and 255 in-line

Controlled by a Aeromotive fpr

My question is with my fuel lines. Can I just make everything -6an or am I going to have to go -8. If I can get away with -6an it will save me lots of time and money and just make everything easier.

 

[pneumo]

-6 will work. Just make sure there aren't any other restrictions or neck-downs in the fuel line, and use a high flow filter. Here's a good, inexpensive filter that's easy to install with -6 lines Summit SUM-G1512 - Summit® Chrome Fuel Filters – SummitRacing.com

 

[benjimatt]

Well I just accendentally purchased a golan filter on ebay that has -10an fittings on the end :-(

SO I think im going to go do -10 hose to the rail. and ill either change the rest to -8 or -6. And im going to tap my stock fuel rail to accept -10. well 1/2 npt maybe

 

[Jafro]

-10 is overkill and will cost you out the ass for fittings and hose alike. Plus did I mention it's overkill? -6AN can provide enough flow for 2000+cc injectors.

Here are some pics of my fuel line installation, -6AN. Basically the old-skool SteveTek principle. < Click and read. Now, here's what's not in the Stevetek article.

One of the things I did was utilize my stock fuel sender line as my return line to save the expense of the -6AN hose. Interestingly enough, the factory fuel line will thread directly into a Russell -6AN straight hose fitting with a slight bit of Teflon tape, and no leaking. All the sealing really gets done by the tapered flange, so it's just a precaution. The teflon will dissolve if you leak fuel, so it's really just an indicator if anything. The right stuff to use if you have leaking problems is this stuff right here. It's pretty much the only approved sealant that you can use on gasoline fittings.

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I'm using an Aeromotive FPR with -6 fittings. It made plumbing the return a piece of cake.

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Because the high-pressure send line is now being used as a return, and because the fuel sending unit has a hose nipple with a clamp, I just cut the fitting off the end of the old send line and smoothed it out, then installed a compression barb fitting on it. I didn't have a flare kit at the time, but that would work better than the barb because the barb fitting's inner diameter is about 3/4 the size of the line, and it knocks out 3 potential spots for leaks to just clamp a hose on it. I wouldn't do that without the flare on the line because you're dealing with fuel.

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As you can see, the same principle applies to the fuel sending line at the tank. -6AN screws right on. You'd better hold the fuel sender line with a wrench while removing the old line or honking the new line down tight because it's very fragile and you'll be replacing the whole fuel sending unit if you don't.

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I used cushion clamps along the underside of the car...

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... and zip tied the other end of the line to the brake lines/fuel return so that they don't get hung up on anything or crushed by jacks/lifts.

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As for your fuel filter, you can get adapter fittings to allow it to fit, but I'd return it and get a -6AN racing filter. Mainly because you'll have to buy fittings and adapters instead of just buying fittings.

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I'm using the Russell -6AN filter, and it has a re-usable stainless filter than can be cleaned and replaced. It's worked out fine for 40k miles on a street-driven car without a single issue.

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I hope these suggestions help you figure some things out.

 

[benjimatt]

Hey man thats for the suggestions. I ended up keeping the golan filter and from the filter to the rail im just going to go -10an. I know its huge but it was the cheapest option.

For the other side of the filter I just got a reducer to -8an and am going -8an all the way to the fuel pump. I think I am going to use your suggestion for the fuel return thought. That looks like a really good Idea.

 

[Jafro]

Sounds like a plan!

The only thing I'd be concerned about is the return line not being able to flow enough of the un-used fuel back to the tank at idle. It shouldn't be a problem IMO, but I don't know what kind of a beast your fuel pump is. If the return is smaller than the send line and your fuel pump can flow what a -8AN line can, it could be a restriction that could raise your fuel pressure. But I don't see any reason to do that differently since the return line at the tank isn't any bigger than the old fuel sender line.

BTW: -8AN fittings will not screw on to the fuel sender at the tank. How are you going to work around that? Are you running an external fuel pump/fuel cell?

 

[benjimatt]

Sounds like a plan!

The only thing I'd be concerned about is the return line not being able to flow enough of the un-used fuel back to the tank at idle. It shouldn't be a problem IMO, but I don't know what kind of a beast your fuel pump is. If the return is smaller than the send line and your fuel pump can flow what a -8AN line can, it could be a restriction that could raise your fuel pressure. But I don't see any reason to do that differently since the return line at the tank isn't any bigger than the old fuel sender line.

BTW: -8AN fittings will not screw on to the fuel sender at the tank. How are you going to work around that? Are you running an external fuel pump/fuel cell?

Whn I changed my fuel pump to the 255 I accidentally broke the metal pipe. So I had to fab up a new section. So now I have 3/8" (-6an) right at the fuel pump. So now I have to figure out how to make the 3/8" line to a 5/8" line.

 

[Jafro]

Snap a pic. Brainstorming would be easier if I could see what you're working with. Sounds to me like it would require some brazing, though.

...man those things are easy to break.

 

[benjimatt]

Ill be sure to snap some pictures for you when I get home.

 

[Jafro]

I know I beat the -6 horse already... It's already dead, but think of this as stress relief. I know there's no room for mistakes with your fuel system, so this is the time to do it right. When determining -AN sizes, basically you place the AN size over 16 and reduce the fraction.

-6 = 3/8"
-8 = 1/2"
-10 = 5/8"

If the inside of the factory fuel sending unit is smaller than 1/2", then running -8 would nearly be pointless because of the restriction that occurs right at the pump before it leaves the 3/8" sending unit. So in order to need 1/2" fuel lines (to take full advantage of...), you'd need that restriction eliminated. I don't remember what the inside of my sending unit looks like because it's been 6 years since I've been in there, but it might not be easy, maybe even not possible. It could even be possible that your fuel pump would work harder to re-pressurize the 1/2" line under heavy load because of the greater fuel volume on the other side of the restriction.

Clearly you're are planning to flow a lot of fuel. So much that I will be envious of the acceleration you will experience. If you do figure out your injectors would allow you to flow more than 10 lpm of methanol (or E85) when you're wide-open, then you'd definitely need a bigger-than -6AN setup.... but if you don't, it's probably going to save you a lot of headaches to use -6. You should be able to calculate the fuel volume necessary to max out 1600 cc injectors with the equation used in the stevetek article.

I have a shelf full of parts I ordered that turned out to be wrong on my last build, but I eventually found uses for them on other cars. Can't say that I'm disappointed with the outcome now, but it sucked then when I was on a tight budget.

 

[benjimatt]

I know I beat the -6 horse already... It's already dead, but think of this as stress relief. I know there's no room for mistakes with your fuel system, so this is the time to do it right. When determining -AN sizes, basically you place the AN size over 16 and reduce the fraction.

-6 = 3/8"
-8 = 1/2"
-10 = 5/8"

If the inside of the factory fuel sending unit is smaller than 1/2", then running -8 would nearly be pointless because of the restriction that occurs right at the pump before it leaves the 3/8" sending unit. So in order to need 1/2" fuel lines (to take full advantage of...), you'd need that restriction eliminated. I don't remember what the inside of my sending unit looks like because it's been 6 years since I've been in there, but it might not be easy, maybe even not possible. It could even be possible that your fuel pump would work harder to re-pressurize the 1/2" line under heavy load because of the greater fuel volume on the other side of the restriction.

Clearly you're are planning to flow a lot of fuel. So much that I will be envious of the acceleration you will experience. If you do figure out your injectors would allow you to flow more than 10 lpm of methanol (or E85) when you're wide-open, then you'd definitely need a bigger-than -6AN setup.... but if you don't, it's probably going to save you a lot of headaches to use -6. You should be able to calculate the fuel volume necessary to max out 1600 cc injectors with the equation used in the stevetek article.

I have a shelf full of parts I ordered that turned out to be wrong on my last build, but I eventually found uses for them on other cars. Can't say that I'm disappointed with the outcome now, but it sucked then when I was on a tight budget.

I unserstand your concern. When I look at the stock lines and a -6an lines they seem pretty close to the same to me so thats why I think a -8an upgrade is more of an actual upgrade than the -6an. From what I see the worst case scenario is that the intank walbro isnt big enough and id have to go with the bosch in-tank but I have seen multiple e85 setups that people are using -8 lines. This is why I am not that worried.

Alsthough unfortunately I may need to upgrade my return line but we will see. Im not so sure just yet.

 

[2gGSX]

Something to keep in mind is that by going to a -8 line, the total mass of fuel inside your fuel system increases, which in turn increases the amount of stress on your fuel pumps. Your fuel pumps are going to be the real limit on your fuel system, so this extra stress will only work against your goals.

 

[Jafro]

The lines delivering the fuel on the factory system are called 5/16" lines, but the outer diameter of those lines is only used as a point of reference when you're standing at the parts counter. Their inner diameter is about 3/16". Since AN lines are spec'd by their inner diameter, -6 is about twice the size of the factory lines.

At 60 PSI, 1600cc x 4 injectors = 6400ml or 6.4 Lpm at full duty cycle. Of course a DSM only runs 43.5 PSI, so it's really more like 4.6 Lpm.

The stevetek article's liquid flowbench tests proved -6AN could carry 10Lpm. Maxing out a 10Lpm fuel system would require 2500cc injectors (or a set of eight 1200's if you're running 2 fuel rails). At that point with -6AN, the only limiting factor would really be the pump and whether or not it could keep up with demand.

Now, with all that considered... remember that Stevetek didn't consider the flow volume of an in-tank fuel pump. I'm running the 255Lph Walbro Hi-pressure pump. It takes me 2 minutes to fill a 5gal gas can when changing over my fuel. 5 gallons = 18.93 Liters. That's about 3.9 Lpm with the car off (at 12v instead of 14v). The 255lph Walbro is spec'd by the manufacturer in Liters Per Hour, so 255÷60 minutes=4.25 liters per minute. That math should be about right based on the my test if the car were running at 14v. That's really close to what Walbro specified.

What I'm getting at here is that an in-tank fuel pump can't even flow what a -6AN line can, and the cars you saw with 1/2" lines probably aren't using the stock tank and fuel sending unit. 1600cc injectors are about all you can get away with through the stock fuel sending unit even with a Walbro/Denso no matter what size lines you run to the rail, so there's really no benefit to running -8AN without replacing the tank with a fuel cell and getting an external pump.

But if that's the setup you need, then by all means run bigger lines. With 500-550whp being your goals, I wouldn't think that's the case, and you shouldn't even need 1000cc injectors to pull off those numbers. I'm running 357awhp with a lowly set of RC550's (for now ). I built my fuel system to be future-proofed because I plan to run something bigger than a regular old big16g someday soon. I overbuilt a lot of stuff on my car. Heck, I could have bought a 90-92.5 1g and saved myself $3500 worth of internals and machining but I wanted it my way. I don't want to discourage you from building what you want, I just want you to have the numbers to consider so you know it's done right, and so you don't run into problems or out of money. You'll need that money for other mods.

 

[benjimatt]

Just to let you guys know. since I already bought the stuff im probably going to use it . Im pretty stubborn. At least thats what my local board says . Well right now im on e85 and using 750s which are already at around 85% duty cycle and this is only at 17psi.

When I was on pump I ran 27 psi with about 90% duty cycle.

I could have gotten away with 1300cc-1400cc but for the extra head room I went with 1600scc

 

[benjimatt]

Also I was wondering. Does the pump just shoot out the same amount of flow when its on. Or does the ecu tell it to use less at certain times?

 

[Jafro]

If you've re-wired it to the battery with a relay like many people do, then it always pumps the same volume. If you're still running the factory harness to the pump, then the only time it decreases is when your turn signals are blinking, when the bass hits hard and your amp puts a hit on the battery, or if you have your wipers on.

In principle, it always flows the same amount. The ECU doesn't try to change its flow for any reason, it just turns it on and off with the MPI relay. But in reality, the only thing that causes a variation in flow is other electrical items in the car pulling current out of the circuit that the fuel pump needs. DSMs have weak alternators IMO. Their output is pretty weak considering how may powered options they have. If you have a Walbro, you've no doubt heard what I'm talking about when you flip your turn signal and the fuel pump changes pitch. This is the reason many DSMers rewire it. You wouldn't want your turn signals causing you to go lean when they blink or because Jeezy's new album makes girls' asses hit the floor.

It's okay if you bought all that stuff. I'm sure you'll figure out how to make it work because you sound determined.

 

[Flash]

Well I just accendentally purchased a golan filter on ebay that has -10an fittings on the end :-(

SO I think im going to go do -10 hose to the rail. and ill either change the rest to -8 or -6. And im going to tap my stock fuel rail to accept -10. well 1/2 npt maybe

They do make a -10 to -6 conversion, browse JEG's.

 

[benjimatt]

Ok guys I need some help. I have decided to go -8 an all the way to the rail but here is my dilemma.

I bought 20' of stainless -8 an hose and for some reason I thought that I could just use some push lock fittings on certain parts of the hose. But it looks like you cant just use the pushlock or barbed npt fittings with stainless steel hose I did not know this.

So to make this work am I going to have to have an fittings from the fuel pump, then two others on the inline fuel pump and then another on the end of the line going to the fuel filter. and so on all the way to the rail?

 

[Jafro]

Ok guys I need some help. I have decided to go -8 an all the way to the rail but here is my dilemma.

I bought 20' of stainless -8 an hose and for some reason I thought that I could just use some push lock fittings on certain parts of the hose. But it looks like you cant just use the pushlock or barbed npt fittings with stainless steel hose I did not know this.

So to make this work am I going to have to have an fittings from the fuel pump, then two others on the inline fuel pump and then another on the end of the line going to the fuel filter. and so on all the way to the rail?

Dang. Sorry to hear that, man.

You need the full-flow style fittings for that hose. If you look at the Summit Racing site, the hose ends you select recommend the right hoses for it and warn you of this on the product page if you click "add-to-cart". I get them mixed up all the time. Different styles of fittings are indeed dependent on different hose-types.

Also, the Summit brand AN fittings are cheaper than all the others if the red/blue color scheme works out for you, and they're basically identical to the Russell brand.

 

[benjimatt]

So everything is pretty much working out. I finished the feed line and I had enough line to do that return also +1

So now my system is -8an feed and -8an return.

One problem though. I was wondering is there even really a point in upgrading the fuel system at all.
So my fuel pump has a super small outlet. But after that there is no more restrictions. But on my return line I have it going to the afpr and those inlets are really small.

Then my return to the tank has a small out let too. So is there any reason to even upgrade the return lines.

 

[Jafro]

So my fuel pump has a super small outlet. But after that there is no more restrictions. But on my return line I have it going to the afpr and those inlets are really small.

Then my return to the tank has a small out let too. So is there any reason to even upgrade the return lines.

Really it all depends on the capacity of your fuel pump(s). Chances are you're not going to need to flow any more than 10lpm of fuel, which is what a 3/8" line can deliver. I believe the return tube on your sending unit is 1/4"... but that shouldn't create a problem because some of the fuel is being used, and realistically you probably will only be moving 6-7 LPM with both pumps. There is a huge benefit in upgrading the fuel lines if you're ridding your fuel system of the banjo bolts, in fact, it's really the biggest benefit of replacing the lines.

You mentioned that you had an Aeromotive FPR in your 1st post. You should be able to thread whatever size fitting into its ports is necessary to match your fuel lines. If you're referring to the size of the hole inside the AFPR (when you un-screw the fittings), it's bigger than your fuel tank's return inlet, and that unit can handle -8AN. I've even seen -10 lines going through one of those on an IHRA rail car, though I don't know if it was modded for that purpose? I was just like, "cool, I've got one of those".

 

[benjimatt]

Thanks

Last question and I think Ill be finished. My fuel system should be finished today. I have all the fittings in and everything is set. How do I go about testing the fuel pumps to make sure everything is running correctly. I did a couple of things ghetto and I want to make sure there are no leaks .

Do I need use the 12v test connection on the firewall (if I can find it). Or should I use tmo logger to activate the fuel pumps. And is this safe to do? How long can I do it for. Is 5 minutes oging to hurt anything?

 

[Jafro]

Turning the key to the ACC position will prime the pump, but it won't stay on. Jumping power to the pump would work, but the logger method is your best bet. Are both fuel pumps on the same circuit?

Turning on the pumps won't hurt anything unless you're using household current to power them. Then it would all be over with very quickly. Otherwise, you're safe with DC power for any amount of time.

At 43PSI, tiny leaks will mist so fine you'll barely be able to see them. Get a bright shop light (preferably not incandescent unless you've got a fire extinguisher handy), and scrutinize those fittings. The fine mist from a leak makes a flash-ignition hazard, so there's no way you want to test the fuel system with the car on. A hot manifold would be all it takes.

On my car, I didn't do that. I had a fine leak as well as a nicked o-ring on the afpr... but caught it quickly because there was someone else helping me for the 1st start-up. My nose told me there was something wrong, and I found it eventually. What would help to find possible leaks since they're so hard to see is to grab your fittings with a dry paper towel for a half-minute or so while the fuel pump is running and check the towel to see if anything's wet afterward, both visually and by smell. A single drop of fuel is bad. Check every fitting.

 

[benjimatt]

Well My base psi is 38 psi. Should I increase it for test purposes?

Also I rewired my stock fuel pump and put the new inline one with that so power wise they are running together with the new relay.

So Ill try to use one of those methods when I get home.

I am also doing a lot of reading and people are saying that on e85 they are using
12:1 - 12.5:1 AFRs (gasoline calibrated wideband)

Now since I am in albuquerque new mexico and my altitude it 5000+ feet do these numbers still apply to me on e85??

 

[Jafro]

Well My base psi is 38 psi. Should I increase it for test purposes?

Remember that your FP increases 1 PSI for every pound of boost you're hitting. I'd test it worst-case-scenario, or at least 55 PSI. If it hasn't leaked by then, I doubt you'll have any trouble with it.

Now since I am in albuquerque new mexico and my altitude it 5000+ feet do these numbers still apply to me on e85??

That's way beyond my sea-level gasoline-burning ass to answer. Someone else?