fuel reg AFTER carbies

[merc-blue]

i was suggested to do this by a mate,
bassicaly this is how it goes
run a high pressure fuel pump up to and past the carbie then a regulator after the carbie with teh excess returned to the fuel tank
bassicaly this way the pressure over the carbie rating/reg setting is pissed back into the tank but under heavy work there is always plenty of fuel there if the engine/carbie needs it'has anyone else done this
there are 3 or 4 guys who i know who run this "EFI" style setup and love it

[MS-75]

Sounds fine.

That is how MS-6X (and possibly other model) Crown fuel systems are set-up.

ie, supply line, pump, carby, reg, return line.

Just make sure you have an oil pressure switch fitted up so the electric pump (if you use one) only runs when you have oil pressure, otherwise it will run all the time when the ignition is on which is dangerous in the case of an accident/roll-over.

Also, you only need a carby pump as the pressure only needs to be 6-10 psi or so, not an EFI pump, and you can scrounge the pressure reg off a Crown in a wreckers. You'll find it on the passengers side inner guard in the engine bay-you can't miss it.

Cheers
Sean

[TA-022]

what benifit would this setup have over std?

[Starfire]

Plenty of carb setups run a return line like you have described. I would not suggest running a high pressure (efi) pump though - a carb typically needs 5 - 8 psi where efi runs 40+ making it very easy for the carb to leak and start a fire.

[merc-blue]

i wasnt thinking a 40PSI a mate has a 14PSI pump that hes giving me to try

TA-022, no benefit untill you have a engine that wants it, im building a 2Tg/3T hybrid on very agressive everythigna dn when you plant it on std setup it cant get fuel, this way there is always plenty of fuel ready for the carbie

[YLD-16L]

im building a 2Tg/3T hybrid on very agressive everythigna dn when you plant it on std setup it cant get fuel,

Could you explain this with a little more detail, because if you are talking about hesitation or a "bogging" down feeling when you "plant it" at low rpm it is most likely not a case of too little fuel but in most cases is caused by excessive fuel as you 'pump' the throttle causing a feeling of hesitation or bogging down.

What sort of carbies are you running on this hybrid 2T/3T?

[merc-blue]

not bogging down just purely running out of fuel, (i think the pump and reg in there are deing), the 2T/3T for now is 40mil solexs but i wanna get a pair of webber sidedraughs

[YLD-16L]

Interesting, correctly tuned/jetted 40mm side drafts work fantastic even on a highly strung 2L and 45mm can offer more than enough.

Sounds like a pump/tune/jetting problem at the moment and bunging a fuel reg on might just be a baindaid solution??

Let us know how it goes.

I had 45mm webbers on a 2TG at one stage and ended up going back to the 40mm ones, the 45's were great at high rpm but around town they were a bit much. Oh the sweet sound of sidedraughts in the morning

[Rodger]

Merc-blue,

14psi is a bit high but you could certainly try it. Put it back near the tank and use #8 hose from it and use a smaller hose or the old steel line to form the return line. No need to get a regulator as the different hose sizes will give a lower pressure at the carby inlet.

My experience though with tuning and running the Solexes in competition.

Get a pump with around 8-10psi, place it in the boot near the tank and run this using #8 size hose from the tank.

Solexes work best at around 6-8psi and can handle the 10psi. No need for a return.

The main problem that arizes from any fuel delivery system, efi or carby, is starvation of fuel picked up from the tank especially on long corners. This was the biggest problem I had to over come with my race car initially.
So some form of surge tank is required. One I recommend is to simply gravity feed from the tank and take the pump from the surge tank.

Other things that would cause the condition you are describing, in order of checking:

1) The pump jet system on the carbies is not working correctly. May have blocked or incorrectly fitted pump jets. This is the system that squirts fuel dirrectly into the inlet ports at initial throttle movement, say from standing start or from low speed crusing.

2) The float levels are too low. This will stop long full throttle runs but not show up in above situation.

3) Loose inner venturies. This will cause back firing and generally poor rough running especially at any throttle opening above 20% open.

There are several other things you can do to make the Solexes run very well on your set up, ask if you still have issues.

Regards

Rodger

[gianttomato]

not bogging down just purely running out of fuel, (i think the pump and reg in there are deing)....

O RLY

Why would this happen if your sidedraughts have their floats correctly set? More likely you have a tune issue rather than a fuel delivery issue per se.

[mrshin]

1. There is no such thing as a '40psi pump' etc. - it's just that a given pump is able to manage a certain amount of flow at a certain pressure, and thus pressure is determined by the amount of restriction to flow. Therefore, an EFI pump is fine for a carb, with an appropriate regulator etc.
2. Oil pressure switches suck for fuel pumps, especially if your engine struggles to get oil pressure when first started for a few seconds - instead go grab a 'lock off controller' from an LPG place, and connect it to your ignition.

[CrUZida]

2. Oil pressure switches suck for fuel pumps, especially if your engine struggles to get oil pressure when first started for a few seconds.

I'm sure it would be fine for a carby, coz there should be fuel left in the bowl.

But yes, it would suck for EFI.

[Trent-KE30]

Yeah our old crowns have that fuel return line that goes back into the fuel tank