Yo people...

Doing a carb conversion...

I have a facet 1.5-4psi solid state pump..

I was going to run a tpiece return, however I dont think its powerful enough, or has the flow rate to cope with fuelling the carbs and the return line.

I did a small test earlier, with a pipe on the outlet of the pump, with a tpiece, the straight through part going to where carbs would, and all the fuel just took the shortest route out of the t part which would be the return.

so maybe when the fuel level in the tank is higher than the return back into the tank, there would be some resistance, making the fuel go to the carbs...but could i just run the pump, unregulated, with no return...as it should only deliver 4psi maximum?

confused...i dont want to be pushing past needles in the float chambers and overfuelling, however i dont want to be getting fuel starvation as its all going down the return lol??

With that pump just running something like a filterking regulator would be fine, t-piece relies on the back pressure in the line to pressurise the carb feed once the floats close the pressure in the carb feed is near enough 0 (depending on pump type this might also pulse to about 1 psi, normally facet pumps act like this).

to run with out a regulator you would need a pump that switches off when there is no demand.

As for the return line, i know on the mk3's the return is part of the sender unit and is on top of the tank, one might assume that the 6n tank design might be similar.

Yeah on a mk4 the sender unit is like a basket that sits in the tank, and the return is just in the top, so when fuel is less than full it would be like dripping in, not submerged into fuel.

Could do with like a low pressure valve kinda thing, that takes like 1psi to open it up, hmm.

Issue is the car has 8mm fuel lines, as does the facet, but the carbs have 10mm so there will be a pressure drop where it steps up due to the increased volume demand.

Can anyone recommend something !

I run a t-piece with no regulators at all with stock injection pumps and have no issues with fuelling, but what the same system would do with a small facet is another matter.

Having some sort of pressure release valve in the return line could be the answer but id have one that opens at around 3psi just to keep a constant 2.5-3ish pressure before it.

Swirl pot might sort it.

You could make a little restrictor in the return line to up the pressure to the carbs slightly. Like a little hose joiner but with a smaller diameter hole running through it. You could experiment with different sized holes running through it by drilling the hole bigger each time...

You could make a little restrictor in the return line to up the pressure to the carbs slightly. Like a little hose joiner but with a smaller diameter hole running through it. You could experiment with different sized holes running through it by drilling the hole bigger each time...

I can see what you are saying but personally I would use a regulator so you know exactly what pressure the carbs are getting rather than guessing with a 'restricter'

You could make a little restrictor in the return line to up the pressure to the carbs slightly. Like a little hose joiner but with a smaller diameter hole running through it. You could experiment with different sized holes running through it by drilling the hole bigger each time...

I can see what you are saying but personally I would use a regulator so you know exactly what pressure the carbs are getting rather than guessing with a 'restricter'

So would I :-D And I did use a regulator myself. But only if you aren't running a return line would I suggest it. Unless the regulator itself has a return of course.

You could temporarily fit an inline pressure guage whilst you experiment with the restrictor size in the return line, that way you could get the pressure right for what you want.

You arent supposed to leave the guage in a regulator permanently fitted anyway because it will read wrong after a while, so this wouldn't be any different once you have the right pressure :-D

I don't wanna be running a regulator tbh, I think the t piece method is better.

Maybe I should order a higher pressure facet? Like a 10psi one? Not really keen on using like a 30psi+ injection pump. I know it shouldnt build up pressure but yeah.

Or maybe i should just use standard pump and tpiece? :s

does that mean mines not gonna work either?

I'm soon fitting my bike carbs and I've got a low pressure posi flow like yours. I bought it specifically as I'm certain I read with it as it's such low pressure you don't need a regulator. erixtar1992 was using this set up I think - I'll ask him.

yeah i ran a low pressure facet, 1-4psi i think? deff below 5psi. used it with a regulator at first, had no problems but it was drinking alot of fuel, ditched the regulator and used the t-piece method so it was set up with the t piece in between the pump and the carbs, had no problems whatsoever with it on the 1.3 or the 1.4 16v. used less petrol too. return ftw!

oh also, i had the t piece pointed upwards, so that the return went in a small loop upwards meaning the fuel had to go against gravity slightly, so the fuel would find it easiest to go to the carbs if this is what your asking. i did have it without it pointing upwards on the afh and it seemed to make no difference, just did it just incase it would help

Edited 26 September, 201114 yr by erixtar1992

cool mate thats brilliant news!

just to double check - it was this one?

http://www.fuelpumpsonline.co.uk/facet-pos...60104-907-p.asp

and you t pieced off the standard diameter hose? If so.. brill!

edit- seen your second post.. thats a good idea. so the fuel pumped up with the carb spur horizontal so it would go that way first.

I get you!

Edited 26 September, 201114 yr by runforrestrun

cool mate thats brilliant news!

just to double check - it was this one?

http://www.fuelpumpsonline.co.uk/facet-pos...60104-907-p.asp

and you t pieced off the standard diameter hose? If so.. brill!

edit- seen your second post.. thats a good idea. so the fuel pumped up with the carb spur horizontal so it would go that way first.

I get you!

nah i have one of the square gold-ish coloured ones, around the same psi though.

yeh standard hose, on mine though the return is 6mm and the fuel in hose is 8mm , i didnt realise so i just bought an 8mm t piece haha. but a bit of wiggling and patience and i managed to stretch it over.

yeah just basically means that the section after the t-piece would basically have to fill up before the pressure pushes it up over the return loop. so in theory my carbs should have a constant supply of fuel

you can see what imrambling on about here, the pipe looping over on the left of the bay, thats my return

I don't wanna be running a regulator tbh, I think the t piece method is better.

Maybe I should order a higher pressure facet? Like a 10psi one? Not really keen on using like a 30psi+ injection pump. I know it shouldnt build up pressure but yeah.

Or maybe i should just use standard pump and tpiece? :s

I did have a pressure build up once when i caught a branch in the road (it was that or the rest of the tree) and it kinked the return line, the carbs just over fuelled and cut the engine in my case but things could have been worse.

Anyone wanna buy a facet and a modified mk4 sender unit? :)

I may as well talk to a brick wall

I don't want to fuck about with setting the right pressure as I don't know what fuel pressure a 1.6 8v car needs through the range on 600cc motorbike carbs..get me?

Unless someone knows a definitive pressure which they can guarantee it will be spot on, I'd rather tpiece, as the fuels always there. Unless the return is smaller than the feed like, or the return gets damaged, pressure won't build up at the carbs.

I wasn't keen on running an injection pump as it seems odd just to have fuel flowing around a loop constantly at a fastish rate.

I might swap my pump for a 7-10psi one

My pump is no more than 5.5psi max, had worked fine for years via the T-piece until it started struggling to keep up sometimes with the 1.6 16v. Swirl pot sorted it.

The petrol travels from the tank and back to it very quickly, literally only takes a couple of seconds. But the pressure never builds up, so the pump runs loose at about 2psi, which is what the carbs get. And the fuel gets filtered many times over.

my regulator was set at 3psi when i was using it. iv heard someone used a regulator AND a t piece, cant remember what car

my regulator was set at 3psi when i was using it. iv heard someone used a regulator AND a t piece, cant remember what car

I remember that one, told him to run one or the other and not both

Think he removed the regulator and all was well.

ah fair play!! was it not working very well?

from memory i think the term "bag of crap" was used to define how good it was running.

Sure its somewhere in the trolling monster that the Bike Carb FAQ is.

The t-piece does just technically turn the petrol tank into a giant swirlpot + it gives a constant feed of nice cold fuel. :)