Briggs carb fro turbo setup

I recently mounted a VW turbo of a 50hp diesel golf on my 12hp Briggs flathead. It spools nice and builds about 1-2 psi of boost, wich is plenty to add some good power, but as expected the carb is acting up. Does anyone have some tips on making a blow trough carb. Im using a 16 hp carb. For pressurising the floatbowl I was thinking about drilling a small hole before the throttle plate to connect boost pressure to the float bowl. The current float vent is at the intake side behind the gasket, so i think i should be fine with just leaving it as is. Do you think this would work?
I'll post some more pics and video when i get around to making some, but until now that's it.

That’s pretty sweet man! Nice job

That's awesome! Nice job, man!

I'm trying to think about what exactly is going wrong with the carb.  When boost in created is it keeping the venturi effect in the carb from working or is the pressure keeping the needle valve closed causing there to be no fuel in the bowl and leaning it out?

Are you going to do something different with the oil lines?  It looks like you capped off the lines for now.  Did you fill it will oil first?

I was wondering about oil delivery for the turbocharger as well. Maybe a seperate reservoir and pump of some sort? Either way, nice setup so far!

I think turbos have a bronze bushing or something for the bearing don't they? Be careful with no oil pressure at all, not sure how long that will hold up. But cool setup!

Why not just use a draw through design with the carb? Bolt it on the intake side of the turbo.

I got the info you need

Putting the carb after the turbo, is hard as hell to get working. If it is to hard to get the carb working right after the turbo, then you can put it before the turbo on the inlet of the turbo and would be able to use the stock fuel system with no modification. It's that simple this way.

So, putting the carb after the turbo creates a fuel flow problem. You have to think about the atmosphere pressure and the turbo is changing this from a suction to a pressure then to a suction by rpm's. By doing this, when the carb is under pressure, the fuel is being pushed out of the fuel lines and back into the gas tank and the venturi stops working and starving the engine of fuel while the intake is under pressure. The pressure WILL come out somewhere and the fuel system is the weak link with a carburetor, since the engine is not consuming the pressure fast enough. Yes, this is called BOOST, LOL, and for the engine to take advantage of the boost, it has to stay in the engine. Now that the problem is identified, I'll move on.

To fix this pressure problem........
To fix this, you need to fool the carburetor to think that nothing is changing when under boost. Under boost, the venturi stalls because the pressure is overcoming the suction of the venturi because the rest of the fuel system is under atmosphere pressure, not boost. Which includes the fuel bowl, intake (before and after carb), fuel lines, gas tank, and (if equipped) a fuel pump. Everybody forgets about the fuel lines, fuel pump, and the gas tank on this kind of setup. You need to modify all the fuel delivery system to make the engine run right.

Modifying the carburetor. The carb has a vent to the fuel bowl on the inlet of the carb.the boost needs to get to the fuel bowl, so make sure the inlet of the carb is sealed good and this vent is not blocked off doing this. The idea is when you are under boost, the fuel bowl is under boost. Ofcourse, make sure the carb is sealed to the intake to the engine side also. Carb jetting will need to be bigger, so a carb with an adjustable screw will be needed and don't be surprised if you need to drill the jet bigger for more fuel.

The rest of the fuel system needs to be modified also to fool the carburetor. The rest of the fuel system will include the fuel lines, fuel pump (pulse type and electric), intake (before carburetor) and gas tank. Ofcourse, you don't need to do anything to the fuel lines and the fuel pump (if equipped) but still needs to be mentioned. Which leaves the intake before the carburetor and the gas tank. You need to get the boost to the gas tank so the boost from the carb doesn't push the fuel back into the gas tank. This boost signal needs to come from before the carburetor and after the turbo section of intake. Put a fitting on this section of intake going to the gas tank vent. Which means the gas tank needs to be sealed since it will be pressurized from the boost from the turbo. Since there will be a line from this section of intake before the carburetor, when the engine is under boost the gas tank will be under boost, and when the engine is not under boost the gas tank will not be under boost. The gas tank needs to be the same atmosphere as the inlet side of the carburetor for the whole system to deliver fuel correctly.

Blow through carbs are a pain to get working but that is how you do it. As I mentioned in the beginning of this post, if you can't get the carb working right with it after the turbo then just put it before the turbo and you wouldn't have to worry about pressurizing the whole fuel system when under boost. If the carburetor is before the turbocharger then you just have to worry about jetting then and nothing else.

As for oiling the turbo, putting a reservoir of oil on the oil inlet and a line from the oil outlet to the reservoir would be fine. The turbo's bearings spinning would move the oil through the turbo enough to oil it and circulate it through the reservoir. And the reservoir should be level with the oil inlet side for the oil to circulate with ease.

Have fun........

Thanks for all the replies. The picture was very early in the build. I used an old fuel tank and one of those clack clack clack fuel pumps for the oil supply. There’s not a whole lot of pressure, put I think it should be fine.
If the carb I have won’t work I’ll try to get an adjustable motorcycle carb. Is that doesn’t work, I’ll try to get my old EFI system back out.
For fuel I’m just going to plumb a boost line into the fuel tank.
Pics coming this afternoon after I’m back from school

I would think as long as some oil pressure is there it should be fine. Pretty cool!

This afternoon i started modifying the carb, by drilling a passage between the floatbowl and the front of the carb, but i haven't closed the 2 big carb vents on the engine side. I was hoping the manifold and gasket would seal of the old vents nicely, but no luck as you can see in one of the pictures. I found an old aluminium throttle body I build for that manifold, cut it in half and use about 1/4 inch as a spacer and to seal of the old vents. I've also just added some pictures of my oiling system.

The other thing concerning the oil is that it's designed to have 180 degree oil pumped through it. I wonder if the turbo will be properly lubricated if the oil is colder.

Colder oil would just put a little drag on the bearings, if anything the turbo would spool up just a little slower.

Oil system should be good for the turbo.

Interesting setup you have there. I've always been a little bit doubtful if it would be worth fitting a turbo to a small engine, especially if it takes time/effort/money to fit it. Do you notice any difference in power/torque compared with a non turbo Briggs flathead?