Carb Fuel Pressure

[m.i-man 0]

What is the correct fuel pressure to supply a pair of DHLA 48's with? I have set mine up to hold 2psi, as I read Des Hammill suggestions of between 1.5 and 2.5psi under all conditions.

 

But whilst searching for the answers on the forums, people have suggested up to twice that, at 5psi.

 

Who is right? Or what are the consequences of getting it wrong?

 

 

Cheers

 

Rich.

[Kitsune 0]

My 45's were set to around the 5psi mark. Had no problems.

[m.i-man 0]

My pressure alters around 0.5-1psi depending what load the car is under.

 

Did yours run 5psi on idle? 5psi on full song? Or both?

[Matt Holley 11]

I ran my old gti6 on carbs at around 5 psi also this is were it ticked over well and went well, but if I upped it one click on the reg it seemed to pull harded at high revs but didnt tick over as well

[Kitsune 0]

My pressure alters around 0.5-1psi depending what load the car is under.

 

Did yours run 5psi on idle? 5psi on full song? Or both?

 

Pass, it was set up at EFI some years back when Phil was top dog there.

[shine 0]

Regarding to the Weber book around 0,25 to 0,3 kg ( 5 psi ) is a good setting. ( 15 psi is around 1 kg)

 

I've run with 5 psi and that works fine. My pressure is stable from idle to high end.

[m.i-man 0]

Thanks for the replys guys, I will up mine to around the 5psi mark I think, and go with the flow. (bad pun I know!!)

[ashley peddle 3]

mine is on 3.5 (but thats an 8v on 40's so probably irrelavent)

[m.i-man 0]

I was told today that 2psi is good, as carbs don't rely on pressure, they rely purely on volume.... which is why you need to make sure the fuel pump can maintain 2psi under all loads, as any less indicates the pumps' inefficiency to supply the carbs with the correct volume.

[m.i-man 0]

I incereased the pressure today from 3psi to 5psi, and they have become alot more smoother. She doesn't bog down under load, apart from between 2-3000 rpm, but these carbs were off of a rally car, so I'm wondering if they've been setup up in a specific way to which low rpm is of no concern!

[rjw205 8 3 Cars]

Mine were set at 4psi... and no-one has answered you what happens if too high... They will blow the float chambers. There is a chap on here who is the carb king.. dont know his nmae.. but he would know for sure.

 

Rich

[m.i-man 0]

Oh, maybe I'll drop it a little then, I don't want to have to start having problems like that!

[mfield 20]

5 psi does seem high, i would go for 3.5-4psi max tbh. As said to high and you'll have float problems, dunno if it damages them just they won't be able to hold the fuel back and you'll get flooding ( and quite possibly a leak )

[rallyman 0]

Ive messed around with DCOE's and DHLA's for ages and the best thing I can say is to get the car on a rolling road. If the guy there knows his stuff he will be able to set it up, along with the carbs. He should ask you what type of driving/competing you do with it, as this will have a bearing on how it is set up!

The bogging down could be down to carb setup, probably too rich! - though if you have a tall cam in it - this will also cause it to bog down.

Too high a pressure and you will damaged the floats/valves. then the seals will fail!!! Then perhaps a nice little fire!

Fuel volume is correct as you are not running an injector - you just need to keep it full!

Have a ring around your local RRoad centres - dont just take it to the first one, do some asking before you hand over your keys!!

I spose people on here can recommend places!

Michael

[m.i-man 0]

Ok cheers for that. I've heard Richard Longmans down Christchurch is fairly good, may go there when she's mot'd.