hey guys, I have a 12a with a weber IDA sticking on top of it. I want to turbo this thing. How much boost will the carb take without modification?

What modifications would I need to do for, say 8lbs of boost?

I plan on fabbing my own exhaust manifold, and getting a s5 turbo.

Nothing wild here, just want some more power for cheap. (it would basically be the price of the turbo, I can fab everthing else)

 

The brass floats on the IDA can not handle much boost at all, so you need to get that fixed. You need a fuel pressure regulator that increases fuel pressure 1 lb per 1lb of boost pressure. You can actually use the s5 turbo and manifold and just modify the flange a little bit, it will bolt to the 12a.

-Marques

 

680rwhp advised me that the floats were no good for boost but he did say how to fix them. drill a small hole in the floats and fill it with the expansion foam that you can get from lowes. Then solder the hole closed.

For a fuel pressure regulator i advise a Mallory 4307M it will raise the pressure for you as descibed above.

Your also going to need a fuel pump.

 

thanks for the quick replys. I have a carter fuel pump that should be able to feed the engine fine, the fuel pressure regulator is no problem.

I was also wondering about boost leakage out of the throttle shaft holes. is this a problem in the weber IDA? or is it just the float. the foam filled float idea is great.

anybody know where I can find a turbo hat for an IDA, or will I have to fab that too.

 

the carter fuel pump will NOT work!!! you need an efi pump.

 

the turbo hat can be purchace from www.rotaryshack.com free plug for 680rwhp and your carter won't work. I think it is only capable of 7 psi. If your running your carb at say 4 psi right now then you add boost you can only do 3lbs of boost, not good. when your pressure goes over that you will starve the engine. An efi pump will supply enough pressure at all times.

 

thats right, sorry for the brain fart!

I was also wondering about boost leakage out of the throttle shaft holes. Is this a problem in the Weber IDA?
Anybody know where I can find a turbo hat for an IDA, or will I have to fab that too.

 

zenjoe,
i sent you pm

thanks

 

Just curious!

how much fuel pressure does a carb need when on full boost? it can only flow so much fuel thru it. wouldn't high fuel pressure cause fuel to foam when it sprays thru the needle and seat?

the bushings for the throttle shaft will wear on any carb

 

As air pressure in the intake increases the fuel pressure must follow it, otherwise the boost will start forcing the fuel back into the carb. The absolute pressure will change but the manifold-to-fuel pressure difference needs to remain the same.

 

The leakage that you get from the shaft will be small and not affect performance. We build the same set up on a Cosmo in Japan and had no problems as long as you change the float and get the special fuel reg like was said. We had access to a tig welder so we build the carb box our selves for next to nothing.