Weber draw through fuel system help

[advinnie]

I know this one, fit a boost sensitive fuel pressure regulator

[Buggsy]

These single side drafts have a very small float bowl, and a somewhat small needle inlet and seat. For 8 to 10 pounds boost, you may get away with an unregulated pump at 2 psi fuel pressure. Personally, I wouldn't take the chance. For any more boost than 10 pounds, you should absolutely have a regulator that is referenced to boost pressure, so you can keep up with the volume of fuel that the engine will need. Run a 60 psi EFI pump with a return line going back to the tank, and a Malpassi or similar boost referenced regulator. Set it down to 2 or 3 psi, and you'll never have to worry about running lean, ever. That is the way it has been done for decades. Read Turbomania from the 90's. Mr. Craineum's reference to thermodynamics is mis-used in this circumstance.

[advinnie]

Buggsy is spot on I at first was running only 10psi boost with a non boost sensitive fuel pressure regulator witch was set to 3psi and even at 3psi I was over powering the floats on my Weber DCOE carb and if I stayed at 10psi for more than a few seconds I was getting lean popping and bang (not good) so I followed the advice on this thread and fitted a boost sensitive fuel pressure regulator wind my idle pressure down to 2.5psi (witch for some reason is the lowest it will go) and now I can happy sit at 13 psi boost with out going lean

[gbaker770]

Bingo!

[Chip Birks]

u don't need to raise fuel pressure on a draw through, been running one for about 3 yrs now about 13 lbs of boost with 3lbs fuel pressure. I'm no scientist but remember the law of fluid dynamics, pressure goes up and volume goes down. the only reason to increase fuel pressure in a blowthrough is so that the boost doesn't go higher than fuel pressure and push fuel backwards out of the fuel bowl , not an issue on draw through

Are you running a sidedraft weber or dellorto?

[advinnie]

Me ?
I’m running a Weber DCOE side draft

[Chip Birks]

Me ?
I’m running a Weber DCOE side draft

Not you, the guy I quoted. Eveyone I know that runs a sidedraft has a fuel enrichment setup.

[gbaker770]

Hey richard cranium, can you please answer the question I asked?

[Clonebug]

u don't need to raise fuel pressure on a draw through, been running one for about 3 yrs now about 13 lbs of boost with 3lbs fuel pressure. I'm no scientist but remember the law of fluid dynamics, pressure goes up and volume goes down. the only reason to increase fuel pressure in a blowthrough is so that the boost doesn't go higher than fuel pressure and push fuel backwards out of the fuel bowl , not an issue on draw through

Are you running a sidedraft weber or dellorto?

He is running a modified DCOE that is now a split shaft vacuum progressive carb. It's on the theSamba.

[panel]

Samba link anyone ? (saves me searching)

[Clonebug]

Damn iPhone won't let me copy a link.

Performance forum on page 3. Progressive Weber thread...

[gbaker770]

So you're saying this will support 20+ psi in 4th gear in a 2 liter motor?
If so you have probably just done something that noone has ever done with a sidedraft at 3psi of fuel pressure.

[gbaker770]

Keep us posted when you put a performance motor in it. I'd like to seethe pics of how your testing goes. And if its a 94 bore I know where you can get heaps of cylinders for cheap. You're gonna need them.

[madmike]

been there too

[rs58rag]

if u mean me, it's actually on a 1600 (for now) and I did not exceed 20lbs. but yes 3lbs of fuel pressure. I don't get why this seems odd. say if we were talking small block Chevy or Ford and u build a 13:1 compression motor, u don't need to increase fuel pressure for this motor which has a higher compression than say a stock motor, compression doesn't affect the carb. draw through is same concept

It's all about the carburetor being used, weber sidedraft has a small float bowl. You need to boost reference the fuel pressure regulator to keep fuel bowl supply happy when on sustained turbo boost.