Here is what I'm working with now , I'm running a small fuel cell under my hood with a electric pump to use with 104 octane fuel for my nitrous and I'm running my regular fuel tank off of a mechanical with a return line which will have 91 octane/no ethanol fuel. I will be turning on the electric fuel pump and opening a electric valve on the fuel cell line and closing the mechanical fuel line between the pump and carb. but it will still be able to pump back through the return line. Is this workable. Feel free to ask any questions.

 

Shouldn't be any difference than when the seat closes in the carb., would it?

 

Wouldn't a fuel tank selector valve be a better choice?

8Mike9 - I think he is trying to avoid pumping his 104 fuel back to the fuel tank with the 91 octane.

 

I took it as he has an electric valve, one way for 104 and electric pump, the other way for the manual pump from the tank, in effect an electric selector switch?

 

OK, now that I re-read it, I can see it that way.
And I will agree with 8Mike9, no problem dead-heading the mechanical with the return line still connected.

 

Sorry folks my questions can be confusing but this is the answer I'm looking for , one more question if I may- can you dead head a mechanical that has a return line on the pump by just plugging the return line on the pump. Not going to do it but would just like to know.

 

Yes I'm using two electric solenoid valves . One is normally closed and the other is normally open , I have one switch that activates both at the same time,

 

Well it is in effect a selector switch, it allows me to select the fuel tank to run off of.

 

Thanks , I appreciate the advice,

 

I'm not sure on all pumps, but the original fuel pump from a '70 BBC LS5 Vette had a return to the tank as well, when my dad put the engine in his '57 PU, be blocked the return and never had an issue with it. I know this as he put the engine in the PU in late '70, I drove it through HS and off and on for years later.

Now, that said, the only time it would dead head would be when the seat in the bowl closed.

 

Just for safety sake, I'd run a relay that activates the fuel pump and the solenoids.

Put the NO solenoid on an NC contacts, use the other two NO contacts of the relay for the fuel pump and NC solenoid.

This would simplify your wiring and just require one switch to activate/deactivate the setup.

 

I have a couple of extra relays , can you tell me how that will be for safety on the Fuel pump and solenoids. I'm trying to figure out how to fuse it also. I really don't want the pump to quit when I'm on the nitrous -- can I run the pump and nitrous solenoid on the same fuse. So if the fuse ever burns out everything will shut down. What fuse should I be looking at. Any thought are welcome.

 

Safety for the wiring, let the relay carry the load of the fuel pump and solenoids, not a switch.

I'll sit down later tonight with a cold one and see about making a redundant circuit to shut down both the Nitrous and fuel pump at the same time. It can be done by using an additional relay(s) to latch the primary relay on.

Now if you could find an inexpensive PLC to run the relays, we could whip it up ladder logic right quick

Edit:

The reason you don't want to run both off the same fuse (parallel) is in order to size the fuse to handle current of both devices, it will be over sized for each individual device, i/e say your fuel pump draws 10 amps and the solenoid draws 5 amps, depending on the type of fuse used, you probably run a 20 amp fuse, but...if the solenoid started drawing 10 amps an burnt open the coil, it still wouldn't be enough current to blow the fuse and the nitrous would still be flowing. It (fuse) would work if either device shorted out and then the current draw would increase to blow the fuse. Besides, solenoid have what is called an inrush current, where when they are activated, they draw a high amount of current, then settle down to their "operating" level.

 

I have this kinda drawn out. Hopefully able to put it up here for you later tonight, making me dig deep for motor controls...lol

 

Thanks , I really appreciate the suggestions, I realized the fuse situation right after I asked but being verified is a good thing.

 

OP
I assume you are connecting your 104 fuel line directly the N2O system fuel solenoid for the enrichment fuel?
If you leave the carb side alone you will get (91+104 ) / 2 = 97.5 octane in the combustion chamber which should keep you safe, but I know nothing about your setup. (compression ratio, etc.)

If you are trying to get pure 104 octane while on the gun, you will need to burn thru all the 91 octane in the carb feed fuel line and bowls first while letting the line and bowls fill with the 104. You could do this at the track in the pits and during the burn out and staging.

I would just "tee" into the carb fuel line with your 104 line:
1 way valve on the 104 line at the tee
1 way valve and shut off valve on the carb fuel line downstream of the tee.
When you use shut off the valve on the carb fuel line your 91 octane will circulate back to the tank via the return line on your mechanical pump.

Rough sketch below.

 

Love it, that's about were I'm at but tell me about these one way valves , I'll be using a always open valve and a always closed valve, that would seem to solve the problem of one pump pumping up the other pumps fuel line. I'll copy this and print it up , thanks . Any other thoughts are more then welcome. I also have access to 110 by the gallon.

 

https://aeromotiveinc.com/product/on...check-valve-2/

If you install a check valve (one way valve) on the 104 fuel line you don't have to install a normally closed electric valve (one less component to wire) and you can wire the fuel pump on the 104 fuel line to turn on when you close the 91 octane valve.

You would not need check valve on the 91 octane side, I show one because I don't know how much room you have to work with. Having one let's you put that close to the Tee to prevent back flow and gives you space to install the shut off valve down stream.

 

That's sweet, other then the fact I can get a normally closed valve for $17.00 Any thoughts

 

"The Bitterness of Poor Quality Remains Long After the Sweetness of a Low Price is Forgotten”.

I would not trust a $17 valve from Amazon for a Nitrous system. A failure would do a lot more damage than what was saved on a cheap part.

The old timers at the speed shop used to tell me: "When building a race car you have 3 options BUT you can only pick two: Cheap, Fast, Reliable"

Cheap & Fast won't be Reliable
Cheap & Reliable won't be Fast
Fast & Reliable won't be Cheap
Another one was "how do you make 1 million dollars with a race car? Start with two million"

We all have budgets to balance, my advise is save up for quality reliable parts from a Mfg. with a solid history in Motorsports. I save the Amazon purchases for items that my life doesn't depend on.

 

My friend at my age you don't wait for anything. It's literally the highest regarded valve, among every one they sell no matter what the price , I know these companies that I'm looking at, these are the most well know and highly regarded companies in the field. I'm going to back away from this thread if I may. Maybe we should take odds on how many times I use this before it blows up. By the way , It won't. Thanks everyone. I've got some advice that will help. It is much appreciated.