1 (edited by MZAVARIN 2020-04-16 08:45 PM)

Topic: Running fuel lines in carburetor vs fuel injected car

My 1987 Honda Prelude (manual tranny, fuel injected) got squished, so I got another one, but could only find a carburetor , auto tranny )....so now I'm swapping stuff.  damn, this is a lot of work, I can't even imagine how people make these Franken-cars....!!!
I am working on the fuel system....and learning the difference between a fuel system on a fuel injected car and a carburetor car...
What a pain.  I had to take out the fuel tanks, since the FI car has a special spot with 2 hoses coming out for fuel going in/out, and the carb car has a special spot with only one hose. (not counting the breather hose)

Question:

and I guess since the FI system is high pressure, I need good, solid hose clamps for the fuel pump swap.  Hose clamps on carb car were tiny ones

Question:
1- On race car (as well as the carb car) there is a fuel line that goes from the fuel pump (mounted outside rear wheel well) toward fuel rail, but on race car, looks like there is a nut coupling that attaches to the hose coming off the  fuel pump (on the carb car, it is just a rubber hose with clamp).  Any suggestion on how to attach the threaded end coming off FI fuel pump hose to the regular nipple pipe on the carb car going toward engine compartment? Maybe buy something that screws into the fuel pump hose (female end) with a hose nipple for a rubber hose to attach to??). To clarify (or confuse further...)
Race car: fuel pump>special hose>with threaded female end>threaded male end>steel fuel hose going into interior of car
Carb car: fuel pump>rubber hose>metal nipple hose going into interior of car

Need: fuel pump>special hose> with threaded female end attached tometal nipple hose going into interior of carb car

2- On FI race car, there is a return hose coming off fuel rail attaching to metal pipe that goes through the cabin and exits near fuel pump.  I need to install something like this in the carb car for fuel return,  Should I just run a rubber hose going through the cabin?  Safe enough?

Thanks

MarioKart Driving School: 1987 Honda Prelude Si (Opus #28) 
Loudon, NH 2014 - Millville, NJ, Lightening 2019 (RIP)
New and improved: 1987 Honda Prelude Si (Opus #11) Pittsburgh, PA 2021 - ??
and finally won something, Class C Win: Loudon, NH 2022

Re: Running fuel lines in carburetor vs fuel injected car

As you said, fuel injection runs at higher pressure, so you want a more solid connection than just a hose clamped onto a tube.

There are tube to threaded fitting adapters available that use compression ferrules to seal to the tube, that would be one option for connecting to the factory fuel line. Another would be to flare the ends of the hard line and use flared fitting adapters.


Regarding return line:

Should I just run a rubber hose going through the cabin?  Safe enough?

No.

3.F.6 Fuel, Oil, and Coolant in the Cockpit. Any fuel, oil, or coolant reservoirs or lines that are exposed to, or pass through, the driving compartment must be encased by heavy-duty conduit, durable steel or aluminum pipe, or strong metal plate. OE metal lines in good condition in their original location are exempt from this rule, but encasement is still recommended.

Run it under the car, alongside the supply line. Braided line would be preferable to rubber, which is much more likely to get damaged, leak, and hella catch shit on fire.

Sorry For Party Racing! - 1985 Pontiac Firebird - Car #35

A race car exists only in two states: broken or in the process of becoming that way.

Re: Running fuel lines in carburetor vs fuel injected car

Hey Mike its Manny.....
Give me a call and I'll help you figure it out.

Manny

Re: Running fuel lines in carburetor vs fuel injected car

Just to make sure I understand, you're swapping entire engine/trans, and entire fuel system except for the fuel line from the pump to the rail, and the return line from the rail to the tank?
If you're going to need to add a fuel return line where there isn't one, why not put a new fuel feed line in while you're at it?  It's budget exempt and will give you peace of mind and solve your problem.  Also a carb style fuel line may not allow sufficient flow for a FI system and also may not be rated to safely withstand the pressure applied by the FI fuel pump.  Also its over 30 years old.

Re: Running fuel lines in carburetor vs fuel injected car

Complete used braided AN lines are often cheap on Ebay,I would prefer to have AN connections front to back for EFI.

Apocalyptic Racing - Occupy Pit Lane racing
Racing the "Toylet" Toyota Celica powered by Chevrolet Ecotec.
24x Loser with the Celica. 16x loser in other fine machines
Overall winner Gingerman 2019

6 (edited by jimbbski 2020-04-17 10:34 AM)

Re: Running fuel lines in carburetor vs fuel injected car

I would use 3/8 steel brake line for most of the run and then use adapters at each end to make the connections. I like solid metal lines over A/N SS braided lines since you don't have to worry about the lines having to be flexible for most of the length between the tank and engine.

I did that on one race car and used 3/8 to A/N hose adaptor.  Much cheaper too!

If it wasn't a race car I'd use the high pressure plastic line the OEM's use.  I also plumed a car using this tubing and it wasn't a FI car but carb.

Re: Running fuel lines in carburetor vs fuel injected car

Agree. Just run hard line. It only needs to flex coming out of the tank and going into the injector rail.

Mistake By The Lake Racing (MBTL)
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Re: Running fuel lines in carburetor vs fuel injected car

FWIW, when I adapted an EFI engine to a carb body I used the carb fuel line as the return and added a larger steel hard line for supply.  Note that you want to use the special high pressure fuel hose where needed instead of the low pressure carb stuff and the very special submersible high pressure fuel hose if it's inside the fuel tank.  Also, if your high pressure pump is outside the tank, consider putting a regular low pressure pump as a lift pump feeding it.  High pressure pumps generally blow well but suck at sucking.

1990 RX7 "Mazdarita"  1964 Sunbeam Imp (IOE 2013 Sears Pointless) 2002 Jaguar x-type (Winner C-Class 2021 Sears Pointless)
Gone bye-bye
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Re: Running fuel lines in carburetor vs fuel injected car

I once did something very similar with a pair of 86 CRXs.  I swapped the entire fuel tank/lines/etc from the rusty FI car to the clean carb chassis.

Chris from 3 Pedal Mafia

Re: Running fuel lines in carburetor vs fuel injected car

(wow!...this is fantastic)
so the outside diameter of the feeder fuel line that goes through the cabin is 0.31 inch on both cars. (so smaller than 3/8 inch)
On carb car, the ends are flared to accept a fuel hose at the engine bay and the wheel well, at fuel pump
On FI car, the ends have screw on connector.  All the connections on the feeder fuel line are screw on up to the fuel rail
Return line on FI car is all hose clamps

--"There are tube to threaded fitting adapters available that use compression ferrules to seal to the tube, that would be one option for connecting to the factory fuel line."  I like that idea.  Do you know where to buy, what to look for, where, example?  These attach to the flared ends of the carb fuel line to attach to the screew on connector of FI car?
--Running return line under car:  so just use a U shaped hanger and bolt it to the underside? 
- Thanks Manny, I'll give you a call this weekend.  I need to get the car to roll, so I could get it to the cage builder on Sunday....not cheap, will cost me $ouch.00 dollars...but he's done lots of them, does a nice job, and even fixed my circle track cage on old race car to pass tech.
- King1: good thought
-AN connections?? I'll need to Google this...
--"FWIW, when I adapted an EFI engine to a carb body I used the carb fuel line as the return and added a larger steel hard line for supply. 
             Great idea to use the carb fuel line as the return.  That would be easy
  Also, if your high pressure pump is outside the tank, consider putting a regular low pressure pump as a lift pump feeding it.  High pressure pumps generally blow well but suck at sucking"
             Yes it is outside.  So what is a "regular low pressure pump as a lift pump feeding it."/  Should I just connect the carb fuel pump upstream from the FI pump?  Or is this something specific I need to buy?  And just wire it to the FI fuel pump electrical connection?

MarioKart Driving School: 1987 Honda Prelude Si (Opus #28) 
Loudon, NH 2014 - Millville, NJ, Lightening 2019 (RIP)
New and improved: 1987 Honda Prelude Si (Opus #11) Pittsburgh, PA 2021 - ??
and finally won something, Class C Win: Loudon, NH 2022

Re: Running fuel lines in carburetor vs fuel injected car

Sonic wrote:

I once did something very similar with a pair of 86 CRXs.  I swapped the entire fuel tank/lines/etc from the rusty FI car to the clean carb chassis.

Basically what I am trying to do...but the steel fuel lines in the cabin on FI car is under welded circle track cage...not accessible, not removable,

MarioKart Driving School: 1987 Honda Prelude Si (Opus #28) 
Loudon, NH 2014 - Millville, NJ, Lightening 2019 (RIP)
New and improved: 1987 Honda Prelude Si (Opus #11) Pittsburgh, PA 2021 - ??
and finally won something, Class C Win: Loudon, NH 2022

12 (edited by Lemon_Newton-Metre 2020-04-18 02:34 AM)

Re: Running fuel lines in carburetor vs fuel injected car

[edit]:

3.F.6 Fuel, Oil, and Coolant in the Cockpit. Any fuel ... lines that ... pass through ... the driving compartment must be encased ... . OE metal lines in good condition in their original location are exempt from this rule, but encasement is still recommended.

Re: Running fuel lines in carburetor vs fuel injected car

You might consider using the stock fuel hardline as your feed and installing a larger diameter line for the return.

Yes, there is more flow through the feed than the return, but pressure drop (i.e. flow restriction) in the return can impede the fuel pressure regulator's ability to... regulate fuel pressure.

14 (edited by MZAVARIN 2020-04-18 05:52 PM)

Re: Running fuel lines in carburetor vs fuel injected car

Lemon_Newton-Metre wrote:

[edit]:

3.F.6 Fuel, Oil, and Coolant in the Cockpit. Any fuel ... lines that ... pass through ... the driving compartment must be encased ... . OE metal lines in good condition in their original location are exempt from this rule, but encasement is still recommended.

--I guess if installing a new fuel line, and not using the stock OEM, then best to run it outside...

MarioKart Driving School: 1987 Honda Prelude Si (Opus #28) 
Loudon, NH 2014 - Millville, NJ, Lightening 2019 (RIP)
New and improved: 1987 Honda Prelude Si (Opus #11) Pittsburgh, PA 2021 - ??
and finally won something, Class C Win: Loudon, NH 2022

15 (edited by MZAVARIN 2020-04-18 05:52 PM)

Re: Running fuel lines in carburetor vs fuel injected car

hoverducky wrote:

You might consider using the stock fuel hardline as your feed and installing a larger diameter line for the return.

Yes, there is more flow through the feed than the return, but pressure drop (i.e. flow restriction) in the return can impede the fuel pressure regulator's ability to... regulate fuel pressure.

--I can't use the stock fuel hardline as the feed, it is not removable from donor, and the receiving carburetor car has a fuel line that just has the flared nipple ends that attach to regular rubber fuel hoses....not the screw on types that the FI car has...
and I don't think there are any adapters that I can use to convert the carburetor car fuel line ends to the FI  car fuel line ends....

MarioKart Driving School: 1987 Honda Prelude Si (Opus #28) 
Loudon, NH 2014 - Millville, NJ, Lightening 2019 (RIP)
New and improved: 1987 Honda Prelude Si (Opus #11) Pittsburgh, PA 2021 - ??
and finally won something, Class C Win: Loudon, NH 2022

Re: Running fuel lines in carburetor vs fuel injected car

Disclaimer: Non-Professional

Underneath is where my Land Rover fuel line is. It's not as if your race car will see 200k miles and 25 years over the road in MA, so you don't need to protect it from salt by running it through the passenger compartment, right?

Though:
Flare tool, like for brakes? Conduit+bender? There are tons of adapters at my local NAPA store.

LinesToGo.com. They have Civic fuel line selection available for some years. And other Honda and other metric-standard cars as well.

Just some thoughts.

Re: Running fuel lines in carburetor vs fuel injected car

You can totally install fuel injection-rated rubber hose over beaded ends on hard line in a high-pressure setup.  Good FI hose clamps are recommended.

Re: Running fuel lines in carburetor vs fuel injected car

Hi
Thanks everybody for your wisdom and input.
I installed the FI engine into the carb car, and  due to ease/laziness/time/cost etc, what I did was

---I used the Carb supply line that runs inside the car and opens in the engine bay as the return line and just attached it to the fuel rail with a good fuel hose and good clamps.  The diameter is the same as in the original FI car.  And then attached it to the hose pipe that runs near the wheel well on left side that goes to the fuel tank (that I needed to replace since the fuel tank on carb car and FI car are different i found out....unfortunately...)

---For the supply line, I purchase a heavy solid (?stainless) steel line (same diameter as stock) and ran if from the fuel pump near the wheel well under the car, well protected, close to floor, away from exhaust, up into the engine bay, attached to fire wall, and to fuel filter, which has the stock fuel line going to the fuel rail.   I used these Gator Gripper brass compression hose adapters to join the metal hoses....I tried making flares, but they looked like...s...t, so decided against that.

Hopefully this will function...I have not started up the car yet...we'll see...
Still some work to be done but getting close....mainly it needs some custom engine mount fabrication done...and then a long list of little stuff

MarioKart Driving School: 1987 Honda Prelude Si (Opus #28) 
Loudon, NH 2014 - Millville, NJ, Lightening 2019 (RIP)
New and improved: 1987 Honda Prelude Si (Opus #11) Pittsburgh, PA 2021 - ??
and finally won something, Class C Win: Loudon, NH 2022