Bypass Fuel System 1.0

[Infomaniac]

Put together a quick fuel system today for a dual carb blower deal. Version 1.0 ;)
My requirements are pretty simple. But not necessairily easy to buy ready to go.
An affordable reliable fuel pump
Bypass regulator plumbed after the carbs
Enough fuel volume - large enough fuel lines
Free unrestricted flow of fuel from the pump to the carbs
Found EFI fuel rail stock that has a 9/16 intenal passage. Perfect for tapping 3/8 NPT threads.
Maybe I will try a Kinsler bypass valve next time. (Version 2.0) Not as pricey as the BG diaphram bypass valve.
http://www.***boat.com/image_center/data/504/211Bypass_System.jpg
Ran the Bypass back to the inlet of this Clay Smith mechaincal pump. Much less plumbing to deal with returning to tanks. Not recommended by BG but I have done it many times in the past without any problems.
I do return farther away from the pump whenever practical.
http://www.***boat.com/image_center/data/504/211Bypass_Pump.jpg

[Hallett]

Very Clean & Simple Looks Good Info.

[Kindsvater Flat]

Ok now where did you get the efi fuel rail stock?

[Hallett]

I Think Bds Has Them.

[HP350SC]

Looks good, I don't like the reducer on inlet side, why not correct tee?
Sorry hit edit instead of quote

[Infomaniac]

Looks good, I don't like the reducer on inlet side, why not correct tee?
This is prototype verson 1.0 :smile:
The pump has a 1/2 NPT inlet. The pipe threads on the "T" are on the run. I did not have one lying around in the shop with 1/2 NPT threads. That is where most everything came from.
There are a few things I will do different next time until I am completely happy with everything. The EFI fuel rail is billet 6061 T-6, it was pretty heavy. When I have more time I will find something else. If I can find a #8 female to 1/4 NPT fitting it would clean up the carb line connections also.
Going to the dyno tomorrow with this engine. I will check the local hose supply and see if they have the correct "T". Will be steel if they have one.
--------------------------------------------------------------------------------

[Infomaniac]

Ok now where did you get the efi fuel rail stock?
I picked up this one here (http://www.injector.com/prorails.php)

[Taylorman]

Very nice and clean setup. I like your style info.

[058]

Info, Shouldn't the return be plumbed back into the tank rather than the inlet side of the fuel pump? Seems to me the return to the inlet side of the pump would interfere with flow and possibly airate the fuel.

[Infomaniac]

The recommended way is to return to the air space of the tank. The would work harder to pump the fuel all the way back to the tank.
I have done it this way many times with no problems. I normally return to the point that the tanks are tied together. I have even mounted the relief valve to the pump outlet and returned to the inlet.
Just for the sake of discussion:
There would have to be air in the system in order to airate the fuel? Air would compress under pressure and any air would leave when it hit the float chamber. Don't pumps with an internal bypass relieve the fuel back to the inlet side of the pump?

[Unforgiven]

Info, Shouldn't the return be plumbed back into the tank rather than the inlet side of the fuel pump? Seems to me the return to the inlet side of the pump would interfere with flow and possibly airate the fuel.
we run returns in the same idea as his ...we have pump loops and returns...have run them boat ways...no change

[HP350SC]

I see nothing wrong with returning to suction side. Could have overflowing on a dual tank setup if returned to tanks. I will return to fuel separator when I change my setup this Winter. I had initially bought 2 tees for fuel tank fill hose returns, but saw a thread where overflowing occurred. Less plumbing just returning to separator anyway.

[058]

The recommended way is to return to the air space of the tank. The would work harder to pump the fuel all the way back to the tank.
I have done it this way many times with no problems. I normally return to the point that the tanks are tied together. I have even mounted the relief valve to the pump outlet and returned to the inlet.
Just for the sake of discussion:
There would have to be air in the system in order to airate the fuel? Air would compress under pressure and any air would leave when it hit the float chamber. Don't pumps with an internal bypass relieve the fuel back to the inlet side of the pump?OK...just wondering outloud. I return the fuel back to the tank because the tank is mounted behind the engine making the return easy. As to air in the system, can't cavatation create air bubbles?

[superdave013]

Looks good, I don't like the reducer on inlet side, why not correct tee?
Sorry hit edit instead of quote
A -8 tee with 1/2" NPT on the run is a real odd ball. To get a 1/2" on the run you would need to run a -10.
Now that you got me thinking. I have a ton of weld bungs and I could just fab some up. Info, what do ya think? Some bungs, tubing and tig time. Could be real nice. Maybe a -10 inlet with a -6 or -8 return port. Hummmmmmmmm

[HP350SC]

Info- How about a -10 on the run with 1/2 NPT into pump. Then adapt the bypass if neccessary, as it's not as critical.

[Taylorman]

Info- How about a -10 on the run with 1/2 NPT into pump. Then adapt the bypass if neccessary, as it's not as critical.
I thought i was the only one crazy like that with fittings.

[Heatseeker]

Here's what my set up looks like:
http://www.***boat.com/image_center/data/500/99side_mounted1.jpg
I was running a BG 2 port before the log previously. After reading about the benefits of a bypass system here, I changed over to this earlier this season. The return line runs back to the tank tee block that I made up. I haven't had any problems with it so far. I was thinking about re-mounting the reg. to the tee block directly to clean up the install a bit. Any feedback?
Oh yea, the scoop in the pic has been finished and polished since this pic was taken.

[Infomaniac]

Cool - What kind of log is that?
The bypass will work at the "T" or in the line between the log and the "T"
HP350SC - I would prefer a 10 with 1/2 NPT on the run but would not want to adapt the bypass. More hose ends and fittings ($$) involved.
Actually my bypass only needed to be #6 but the reducer was the least amount of adapting I could think of.

[Heatseeker]

Cool - What kind of log is that?
Thanks. Couldn't have done it without you.
Made the log myself :D !

[superdave013]

Heatseeker, I like that. But I'm not a fan of forged 90's in fuel systems. Also I don't like teflon tape as it always seems to get in the needle & seats.
I'd keep the regulator close to the log myself.
Info, I'm sure he made that as I know he's pretty crafty. Looks like he did a nice job on that scoop too.
I plan to start making them also but I'm going to weld AN bungs on them. Like I said, maybe we could come up with a slick tee on the inlet too.

[hondajoey]

i have a question on this type of bypass
wont the fuel just take the path of least resistance and just keep flowing out the bypass instead of filling up the bowls, i know you guys are running them with out problems im just thinking you would end up with starvation

[Infomaniac]

i have a question on this type of bypass
wont the fuel just take the path of least resistance and just keep flowing out the bypass instead of filling up the bowls, i know you guys are running them with out problems im just thinking you would end up with starvation
That is a very good question.
The bypass valve is closed until the pressure AHEAD of it reaches the pressure you have set it to.
It will then open as much as necessary to MAINTAIN the pressure you set it to.
That is the wonderful advantage of a bypass system. It is in parallel with the carbs and not in series. The carbs have fuel "priority" so to speak.

[hondajoey]

so i just reread your original post and i think i see how you are plumbing this, so you have the regulator before the return line after your fill line and that is how you are regulating your pressure?

[Infomaniac]

so i just reread your original post and i think i see how you are plumbing this, so you have the regulator before the return line after your fill line and that is how you are regulating your pressure?
You got it.
This is much better than a typical regulator. A typical regulator is in between the pump and carbs. It regulates pressure after itself and is very restrictive.
In this type of system fuel flows freely between the pump and carbs. Except for my forged 90 degree fittings LOL

[Heatseeker]

Heatseeker, I like that. But I'm not a fan of forged 90's in fuel systems. Also I don't like teflon tape as it always seems to get in the needle & seats.
I'd keep the regulator close to the log myself.
Info, I'm sure he made that as I know he's pretty crafty. Looks like he did a nice job on that scoop too.
I plan to start making them also but I'm going to weld AN bungs on them. Like I said, maybe we could come up with a slick tee on the inlet too.
Thanks for the props!
Here's another shot of the scoop after it was finished:
http://www.***boat.com/image_center/data/520/99scoopfrt.jpg
I added the dogleg to the opening to make it look a little different. I'm not sure if I like it or not yet. The scoop was a bitch to fab/polish(it's made from .060" 316 stainless sheet). I probably have around 15 hours in it start to finish!
I would have used weld AN bungs if I knew they were available when I made the log two years ago(maybe I'll make another one,dammit!). So far I've been lucky with the teflon tape. It just never seemed right to use the teflon paste to me. It seems like the gas would dissolve it. I guess I'm a little hard headed :notam: . I'm open to a slicker log inlet. Let's see what you can come up with.

[Taylorman]

Thanks for the props!
Here's another shot of the scoop after it was finished:
http://www.***boat.com/image_center/data/520/99scoopfrt.jpg
I added the dogleg to the opening to make it look a little different. I'm not sure if I like it or not yet. The scoop was a bitch to fab/polish(it's made from .060" 316 stainless sheet). I probably have around 15 hours in it start to finish!
I would have used weld AN bungs if I knew they were available when I made the log two years ago(maybe I'll make another one,dammit!). So far I've been lucky with the teflon tape. It just never seemed right to use the teflon paste to me. It seems like the gas would dissolve it. I guess I'm a little hard headed :notam: . I'm open to a slicker log inlet. Let's see what you can come up with.
The only thing i would do different is eliminate the forged 90 fittings. The two that go to the carb you could replace with a straight NPT-Female swivel AN fitting. They would screw into the log and attach to the an fitting on the carb lines. One like this. Also put a 90 hose end instead of the forged 90 adapter fitting on the fuel inlet on the log.
http://www.russellperformance.com/auto/adapt/images/23-3.jpg

[Taylorman]

Here is a little diagram of how im going to plumb my nitrous with a bypass regulator. Im going with a small nitrous kit and im going to use a 3 outlet regulator. 2 outlets to the carb one to nitrous. Any suggestions?

[Infomaniac]

The only thing i would do different is eliminate the forged 90 fittings. The two that go to the carb you could replace with a straight NPT-Female swivel AN fitting. They would screw into the log and attach to the an fitting on the carb lines. One like this. Also put a 90 hose end instead of the forged 90 adapter fitting on the fuel inlet on the log.
http://www.russellperformance.com/auto/adapt/images/23-3.jpg
Where do you get those NPT swivel fittings?
Does SuperDave013 have them?

[Taylorman]

http://www.russellperformance.com/auto/adapt/adapt_fit_an.shtml

[superdave013]

Where do you get those NPT swivel fittings?
Does SuperDave013 have them?
that's one item I have not ordered yet. But it's in the plan. Info, if you want them I'll put in the order today!

[Infomaniac]

that's one item I have not ordered yet. But it's in the plan. Info, if you want them I'll put in the order today!
Yes SD - you are my plumbing supplier. I will need at least 4 of them. 1/4 NPT and #6 female swivel.
Thanks Taylorman. I have been looking. Obviously not in the right place. Check your new Rep points.

[Taylorman]

I see nothing wrong with returning to suction side. Could have overflowing on a dual tank setup if returned to tanks. I will return to fuel separator when I change my setup this Winter.
Has anyone ever returned to a fuel water separator. I have two inlets on mine and only one being used. Could the other be used for return line from a bypass regulator? Would that be the same principal as returning it to the inlet side of a mechanical fuel pump?

[HP350SC]

Yes it is, and looks a little cleaner too. Should also help keep fuel from heating up with an electric pump, which is my next project. As long as your separator is before the pump, which it should be.

[franky]

Yes, I run the return fuel back to the inlet side of a Teague filter/separator on a Vortech blown motor. I used a Merc early style (tube bundle heat exchanger type) PS fluid cooler on the return line to keep the fuel cooled down fearing that looping back through the pump (electric) would heat up the fuel. Works great.

[VD CRUISER]

Bypass returned to fuel filter/separator
.http://www.***boat.com/image_center/data/520/1410100_1625.JPG
Home made fuel log with BG bypass regulator. http://www.***boat.com/image_center/data/520/1410100_1626.JPG
Sorry about the big pictures, they're either too small or too big.

[Infomaniac]

Nice stuff man.
Nice "Do" also. :cool:

[VD CRUISER]

Thanks Info.

[Taylorman]

Two words for you VD, bling and bling. Nice rig.
By the way, im glad your name has Cruiser behind it.

[PC Rat]

Here is a little diagram of how im going to plumb my nitrous with a bypass regulator. Im going with a small nitrous kit and im going to use a 3 outlet regulator. 2 outlets to the carb one to nitrous. Any suggestions?
Your diagram shows your supply coming from both tanks, but the return going back to one tank.

[Infomaniac]

Your diagram shows your supply coming from both tanks, but the return going back to one tank.
I would return to the "T" that ties the tanks together. If you do not return to the water sep.
I have used a BG "Y" to do this. It has a 1/8 NPT port and I opened it to 1/4 NPT for the return.

[Taylorman]

I think i will leave it as it is now and return the bypass to the seperator. When i was drawing that diagram my thought was to have the bypass to one tank since i would put the line connecting the two tanks to keep the fuel levels equal. I did not think it mattered whether i returned to one tank or two since the fuel levels would be equal.

[Taylorman]

I think im going to leave my fuel setup as is and just return the fuel to the seperator. I was going to eliminate my fuel tank selector valve cause i thought it was going to be to restrictive. I took it off yesterday and took a close look at it and it is no more restricitive than a forged 90 fitting 6AN x 1/4NPT. I don't think my fuel demands will be greater than than can flow.
So what will be signs of fuel lines being to restrictive. Would it be low fuel pressure? Right now im getting 7-8 psi with dual carbs.

[PC Rat]

The recommended way is to return to the air space of the tank. The would work harder to pump the fuel all the way back to the tank.
I have done it this way many times with no problems. I normally return to the point that the tanks are tied together. I have even mounted the relief valve to the pump outlet and returned to the inlet.
Just for the sake of discussion:
There would have to be air in the system in order to airate the fuel? Air would compress under pressure and any air would leave when it hit the float chamber. Don't pumps with an internal bypass relieve the fuel back to the inlet side of the pump?
Airation of the fuel has been discussed a bit, but would fuel pump cavitation be the same thing in this situation? You would need air in the system to cavitate the fuel pump? Would airation be any more of an issue with an electric fuel pump than with the mechanical?
Sorry to keep bringing this topic up, but I want to redo my current system and don't want to build a grenade. 540ci Chevy with Big Shot NOS plate, a filter and Holley Blue pump for each tank, then to a Tee, -8 to a dead head regulator, two out to carb and one out to NOS solenoid. Just a little leary of those Blue pumps and I'd like to do a bypass system.
Brian

[Slyder]

I highly suggest that you use a separate regulator for the nitrous system. It is unlikely that your nitrous tuneup will require the exact same fuel pressure as your engine.
My suggestion would be to "Y" off of the fuel pump and get a holley 2-port regulator exclusively for your nitrous system. This way you have complete control of both systems. Run a gauge on one port for adjustment and run free flowing fittings out to the NOS fuel regulator on the other.
Good luck and have fun,
Paul

[PC Rat]

According to NOS website: All systems require a minimum flowing fuel pressure of 5.5 - 6 psi; 6-7 psi for Fogger systems on V-8s.
My nitrous system is a plate, and since the above says they are MINIMUM requirements- I don't think there would be a problem if I'm running 6.5-7 psi for the carb and nitrous both.
Still trying to figure out the best way to run a bypass system with two fuel tanks. I know Infomaniac said that he hasn't had a problem returning the bypassed fuel back to the supply line - but that was with a mechanical fuel pump. Is there a difference if it's an electric? I just keep hearing people say that it's going to cavitate the fuel pump.
Brian

[Taylorman]

If you have a fuel filter/water separator, return the fuel to there.

[Havasu Hangin']

If you have a fuel filter/water separator, return the fuel to there.
Since there is suction on that line, won't it be trying to pull the bypass spring open?

[Slyder]

Mechanical injection runs a bypass for main and a bypass for highspeed if used. I have seen mechanical injection systems run a return directly to a tee fitting into the pump inlet and others return directly to the tank.
I currently run my electric fuel pump bypass back into my fuel filter which is after my saddle tanks tee together, and before my pump inlet, and have had no adverse effects.
I figure if a constant flow system can be run like this, a carburated electric or mechanical system should have no problems.
Paul

[Slyder]

If you are running a low horsepower system (150hp or less) then I'm sure you could probably get away with running without a separate reg. However, from an insurance standpoint, I think that it would be wise to run a separate regulator.
Most people have no idea what happens to there fuel pressure, let alone fuel volume, after they stab the throttle. At the end of a 1/4 mile run, you might be shocked at what you see.
Since carbs. have a reserve of fuel in the float bowls, pressure, and to an extent volume, isn't as critical as long as it does not come to a stop. With a nitrous system, however, there is no reserve of fuel. The NOS jet is spraying plenty of cold N2O, but if the fuel system is weak then it directly affects your tuneup......and if you have ever used an oxy. cutting torch.....well, you will know it pretty quickly.
Just my .02
Paul

[Taylorman]

Since there is suction on that line, won't it be trying to pull the bypass spring open?
Got me there, how am i suppose to know :confused: Im just repeating what Infomaniac and one other guy said he did.

[Havasu Hangin']

Got me there, how am i suppose to know :confused: Im just repeating what Infomaniac and one other guy said he did.
Well, if you know nothing...that's still more than me.
:D

[Taylorman]

Well, if you know nothing...that's still more than me.
:D
I was thinking that the suction pulling the spring open should not be an issue since your also sucking from the tank.

[Havasu Hangin']

I was thinking that the suction pulling the spring open should not be an issue since your also sucking from the tank.
Probably. But I also know that the vacum is going to take the path of least resistance (I found this out a couple years ago- leaking fuel pickup).
Like I said...I'm an idiot, though. Just though I'd ask.

[jrork]

I think i will leave it as it is now and return the bypass to the seperator. When i was drawing that diagram my thought was to have the bypass to one tank since i would put the line connecting the two tanks to keep the fuel levels equal. I did not think it mattered whether i returned to one tank or two since the fuel levels would be equal.
Just dragging this idea back up cuz I'm curious if this would work. Seems simple and clean.

[Infomaniac]

It is always best to return to the tank. Like stated before I have returned to the pump inlet without any problems.
But It does depend on what type of bypass regulator or valve I used. The BG Diaphram regulator works well but I did try an Enderle in-line valve and it did not like it.
One other issue I had not returning to the tank was returning to a "Y" valve where the tanks tie together. It was positioned lower than the tanks so there was a head pressure at the "Y"

[wetnreckless]

Just a quick note, BDS has a fuel rail with a pill type bypass check valve that
can be adjusted for carbs ( 5-8 lbs. ) I had an odd carb adapter ? and they
machined my rail for a different center to center for the fuel line fittings,they
come set up with -8 inlet and -6 return. Simple set up but cost is around
$160.00 with check valve. part # 108 , they say good to 1200 hp.

[jrork]

One other issue I had not returning to the tank was returning to a "Y" valve where the tanks tie together. It was positioned lower than the tanks so there was a head pressure at the "Y"
That is a good catch. I know on mine the separator is below the tanks so it also would have some head pressure.
Just a quick note, BDS has a fuel rail with a pill type bypass check valve that
can be adjusted for carbs ( 5-8 lbs. ) I had an odd carb adapter ? and they
machined my rail for a different center to center for the fuel line fittings,they
come set up with -8 inlet and -6 return. Simple set up but cost is around
$160.00 with check valve. part # 108 , they say good to 1200 hp.
Wetnreckless, you have any pics of that setup you'd be willing to share?
Thanks guys..........cool topic and very informative.....John

[superdave013]

Those fuel rails use the Enderly deals.
I make a hardline set up for them too. I'll post some pics tomorrow.

[wetnreckless]

jrork, This is the rail I was talking about. Only pics I have at the moment,
My plumbing is -8 from tanks to a tee, -10 to filter / seperator
-10 to Clay Smith pump, -8 to fuel rail, -6 return to a tee before pump.
This seems to work fine for my application.
http://www.***boat.com/image_center/data/521/blower_001.jpg
http://www.***boat.com/image_center/data/521/Daytona_motor.jpg

[Beer-30]

You spoke of the weight of the fuel injector rail stock (too heavy).
Do you think square aluminum tubing would be lighter maybe? http://www.metalsdepot.com/pics/altube.jpg
Say 3/4 or 1". The flat sides would allow tapping (if thick wall) or weld-on bungs of whatever size. All tig-welding, including end caps, would match today's influx of fabricated valve covers.
One could even do an outlet-per-inlet for the fuel bowls. Four outlets on the rail for individual tubes to each inlet on dual carbs. It would take two more "T"s out of the loop.

[jrork]

Reckless, very clean and simple. What size pill are you running to keep your pressure in check? Any maintenance involved with a pill/check valve? Sorry for the ignorance.
John

[wetnreckless]

jrork, actually you can add or subtract shims to change pressure
i,m running about 6 lbs. for maintenance just unscrew from rail
and wash out. I believe Super Dave has something similar, He's
a easy guy to work with, and does what he says he'll do.
hope this helps.
http://www.***boat.com/image_center/data/500/medium/fuel_rail.jpg
http://www.***boat.com/image_center/data/500/fuel_rail_2.jpg

[superdave013]

Here is one I just made. It also uses the pill/shim style bypass from Enderly. This one has a -10 inlet, 5/8" id, -6 port for the bypass, 1/8NPT port for a gauge and 2 -8 O ring boss ports. The ports are on 9 3/4" centers and will be used with a pair of Dominators with the stainless fuel line kit like wetnreckless's except they have the upgraded -8 inlet tees.
http://www.***boat.com/image_center/data/500/fuellog.JPG

[VDRIVERACING]

You spoke of the weight of the fuel injector rail stock (too heavy).
Do you think square aluminum tubing would be lighter maybe? http://www.metalsdepot.com/pics/altube.jpg
Say 3/4 or 1". The flat sides would allow tapping (if thick wall) or weld-on bungs of whatever size. All tig-welding, including end caps, would match today's influx of fabricated valve covers.
One could even do an outlet-per-inlet for the fuel bowls. Four outlets on the rail for individual tubes to each inlet on dual carbs. It would take two more "T"s out of the loop.
Duh... Sometimes a great idea is right in front of our eyes. Thanks for the idea!