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Old 07-17-2019, 10:03 AM
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Nitrous fuel source

Background:

The car I have came with a wet kit installed. I've never used it, and the previous owner claims to have never used it.

The fuel cell in the trunk has two AN connections on it. I'm assuming one was meant for fuel supply while one was meant for return if being used.

The way this car is setup today, is that one line feeds the mechanical fuel pump on the car, and the other is ran to an electric fuel pump out back that feeds the solenoid up front for the nitrous system. I have never even put power to that pump, no idea if it works.

My question:

I like winter time projects that I can work on while not being able to drive the car. This year I'm considering cleaning up the trunk area and making some panels for it, so that it has a more finished look. This would include a different fuel tank. In looking at tanks today, the norm seems to be to have one pickup for a fuel source and one for a return.

Is the way that the car is plumbed right now incorrect? Do most folks just run one electric (or perhaps mechanical?) pump that can handle providing fuel to both sources when needed? Using a T of sorts up front to split off for carb and nitrous fuel? Then just regulating the fuel source for the carb's down to that 6-ish lb range? If so does the nitrous fuel solenoid need to be regulated as well?

I want to do this correctly if I dig into it, because one day I would love to get into toying with the nitrous. Not any time soon, but I do not want to ditch it all together.

Seems like it would also simplify the system a bit by only having one source line from the rear to front, and one electric fuel pump to worry about rather than one electric one and one mechanical.

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Last edited by nazarah; 07-17-2019 at 10:17 AM.
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Old 07-17-2019, 11:34 AM
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First question I've got is where do these outlets locate on the tank??
Twin about 6" apart on the rear side at the lower edge, or do they come out the top??

Those with an internal pick-up that exit from the top of the tank are street/circle track type cells that do not do well feeding nitrous systems. they can lose the draw of fuel during the launch, starving the pump and line. Rear exit cells just feed the pump harder , using the launch g-force to help rather than hinder.

Most nitrous users prefer twin pumps and twin lines, so you can isolate and set fuel pressures between carb and nitrous independent of the other.
fuel pressure in 1/4 lb increments is used as the fine tuning tool in the nitrous system....the system jetting sets the basic power levels, 100, 150, 175, 200, etc but then to get the final tune the fuel pressure is altered for the best peak power/reliability using both fuel pressure and bottle pressure levels.

The other drawback to a single line feeding both carb and nitrous is just getting a pump, filter, and line large enough to handle both...the carb has a buffer zone on the tune, the fuel that is there in the bowl....the nitrous has no buffer, if the fuel isn't there exactly as it is designed to be you get carnage.
A momentary line starvation matters not to the carb, but it sure does to the nitrous system....which is most of the reason nitrous fuel pressures are set on the regulator with the fuel flowing through a jet into a catch pail or fuel can, and not just set with a deadhead regulator and gauge.

Nitrous fuel and carb need separate pressure adjustments, so if you used a single line system you would have to split it to two regulators. Most guys don't do single line so that the carb demands can't upset the nitrous steady state flow requirements.

How many total cell outlets, and where are they all located?? Just the two from the top?? If so, without some investigation it is hard to tell if it is intended to be two outlets, a single outlet and a return, or a single outlet and a vent line.
If it is two located low out of the back side, both are intended to be feed lines and if there is no other fitting on either the top or front side upper edge then there is no current connection for a return line.

You didn't say anything about a vent connection, I'm assuming it has a vented cap??

How big are your pumps, lines, filters, engine HP, and nitrous HP you'd likely try??

Without some more detailed description of exactly how the current set up is, it looks like the previous owner was at least partially on the right track....separate systems.
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Old 07-17-2019, 11:49 AM
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I'll attach a picture here of the current setup. I think that'll answer the questions about the location of the current pickups and the venting.

Your points about twin lines make a lot of sense. I suppose it's probably better to be safe than sorry in a situation like that. It wouldn't take much to test the pump that is wired up back there just to verify it works. And the line is already ran so no work to do there.

The pump feeding the carbs I believe is the stock pump. I have a fuel pressure gauge connected there, and it provides a constant 6 lbs under any conditions so I think that one is in good shape. I'd have to grab some measurements of the other setup.

Sadly, I have no idea about the engine HP. Never had it on a dyno. For the level of nitrous, I'd ideally start very low and work up to a safe but fun level. I know that can be a fine line to walk with that type of stuff.

For this project I'd be going with a totally new fuel tank, so I'd just have to find something with the finish I'm looking for that had the right pickups in it as well as the correct sender.
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Old 07-17-2019, 03:56 PM
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You are going to have to verify that there is a fuel pick-up that goes to the bottom of the cell under both of those outlets....cells like that one line is typically just a dump back return port.

That's a cheap street or circle track cell, and it is mounted wrong directionally the way it is right now, should be mounted crosswise is the way the line connections are designed.

I see both lines going out of the trunk forward of the cell, and no electric fuel pump in the picture.
If the electric pump is also forward of the cell, as the line route would seem to indicate, it is not in a good position.
Electric pump at worst should be beside the cell no farther forward that 1/2 the length of the cell, at best it should be behind the cell, and mounted so that pump inlet is lower than the cell floor.

Appears to be a vented cap, with a hose jury-rigged to the cap vent?? It really should be a sealed cap, with an actual port in the cell with a roll-over valve/vent connection for the hose to attach to.

Something like this is what you need to be looking at. I won't even bother recommending any plastic cells. You'll have to take some measurements and do some shopping to see what will fit your space. If it needs to fit lengthwise like it is presently, you may have to get one custom built, but you may find you can get a square cell narrow enough to fit that gets enough capacity by being taller than the current piece. guessing current cell is about 15 gallon??
Current cell looks like he had the car nearly finished and realized "oh crap, I've got to have a fuel tank in here somehow" and that's your result. Poor choice, both design and fit/installation
https://www.amazon.com/15-Gallon-Alu...EH21N1ZJGY0D5M


If you intend to ever take this to a track, if they observe NHRA or IHRA rules you won't pass tech with the set-up that is in the trunk right now, and the cell isn't even the big problem.

Battery must be in a battery box.
The battery hold down bolts must be 3/8" minimum diameter.
Battery disconnect must be able to be shut off from outside the rear of the car...either cable or lever/link from back of car to the current switch or move the current switch to a point accessible from the exterior(with the trunk lid shut).
I've seen them mounted through the back-up light portion of the tail light lens on Cheveles, and I've got it that way through the back-up portion of my '72 Nova tail lens.
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Old 07-18-2019, 08:14 AM
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Thank you for the input and the recommendation on the cell.

I feel like a lot of the things I've ran across on this car were an "oh ****" at the last moment type of decision. I suppose that is what you can expect though from a car you bought instead of built. Tons of kinks to work out.

One day, I might get it out to a track. So I'll keep those last points in mind. It'll be years out though. I have all the fun I want just tooling around on the street with this car. When I take the kiddo with me he has the perma-grin while we drive too. That alone makes it worth it.
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Old 07-18-2019, 09:26 AM
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What about cells that are shaped like this one?

https://www.amazon.com/DNAMotoring-A...gateway&sr=8-8

I see that the outlets on top are mostly what you see with them in this long rectangular shape. They don't seem to have them down on the bottom ends like the square ones do. Any thoughts on how these would have to be mounted? If they could be length wise so it would run up in between the wheel tubs that might work out good. If it had to run width wise that might not be great.
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Old 07-18-2019, 10:30 AM
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Quote:
Originally Posted by nazarah View Post
What about cells that are shaped like this one?

https://www.amazon.com/DNAMotoring-A...gateway&sr=8-8

I see that the outlets on top are mostly what you see with them in this long rectangular shape. They don't seem to have them down on the bottom ends like the square ones do. Any thoughts on how these would have to be mounted? If they could be length wise so it would run up in between the wheel tubs that might work out good. If it had to run width wise that might not be great.
Well, I guess whether it would work or not depends on where the pick-up tube down t the bottom of the tank has it's entry point. If it is just straight down from one of the AN fittings, probably the central one, it could work in a hard launching car if the fuel level is kept high enough it can never pull away from that pick-up point under g-forces at launch...or cornering. Whether it is baffled or not can make a difference too.
One problem with nitrous use though....it only has one pick-up equipped outlet, the 2nd is return line and the 3rd is vent line according to the ad description.

How much distance between the roll cage bars and wheel tubs do you have to work with?
What about available front to rear space between ends of bars and trunk rear limit??
How much additional height could work??
What's the minimum capacity you could live with?? Factory tank would have been in the 18-19 gallon range IIRC, my '72 Nova is 15-16 gal IIRC.
It could give a better idea of what to look for and someone may have a connection that could help you find what you need in a more drag/street/strip type cell that would fit your space.

it would seem a large part of the lower cost(likely imported) aluminum fabricated cells are street rod/drift car oriented, where dual pick-ups are not needed.
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Old 07-18-2019, 11:36 AM
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I'm gonna have to go do some measuring to see what exactly will work in there. I drive this 100% on the street for right now, so strict track usage I don't have to worry so much about. Not saying there may not be track time in it's future one day though..........
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Old 07-19-2019, 05:26 AM
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Kinda skimmed over the thread, but did catch the part about one fuel pump for the whole deal. Yes, you can run one pump to feed both the engine and the nitrous, but a Holley blue or similar pump won't be enough. I'm a huge fan of overkill on a fuel system, because it's better to have too much than not enough, especially on the bottle. I'd recommend an Aeromotive A2000 or Magnafuel Quickstar 300 at a minimum, with the prostar 500 being a better choice. Latest and greatest is the Aeromotive A3000 setup, which is what I run on my junk at the moment....Which pump will ultimately depend on TOTAL Hp you are trying to achieve, but it's better to plan big, because once you start going faster, you'll always want to go faster....And don't say you won't......

The carb(s) will need it's own regulator, and so will the nitrous system. You can put both regulators on a fuel log and have one line from the pump feeding the log, then run lines from the regulators to the carb and fuel solenoids. For the carbs, assuming they are Holley(s), -6 lines are plenty big enough, and 5-6 psi max is plenty. It's better to run a lower pressure and bigger needle and seats.

On the nitrous side, spend the money to get the system professionally flowed and jet mapped. When you get it back, it will have fuel pressure settings, jet sizes for each power level, bottle pressure recommendations, and timing recommendations based on YOUR combo.....you can get by with running a generic system, but get outside of the tuning window to the rich side, and by by pistons.....get to lean and same deal......

Couple of other things to consider. If this is a daily driver, you have the option of running two fuel systems, one stand alone for the nitrous and the other one for engine only. It works, tons of people doing it, but has some drawbacks....more parts to fail, more lines to leak, more complexity. I'm not a fan of stand alone fuel systems for nitrous, it's better to run it all from one source.

Another consideration is fuel and octane requirements. You will need higher octane fuel when on the bottle. An issue with a stand alone system is having one fuel for the nitrous and another for the engine....the lower octane fuel will affect it once it's in the engine, and you can still run into detonation. Secondly, when nitrous systems are tuned, they are tuned for one fuel and one fuel only. It's impossible to tell what the fuel will end up at once it enters the engine, and even if the nitrous fuel is good, the engine fuel might bring the overall octane rating down enough to cause it to detonate, which is very bad......bad bad.....People do it, and successfully, but it's not the best way....A single fuel source using one fuel is best....



Regardless of which way you go, try to plan for what you will do later on.....because you WILL step it up...speed is too addictive....once you start going fast you'll always want to go faster.....nitrous only makes this worse.....
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