HS carburettor
Turbo Mini Forums

This is most likely a very simple question But I know less about this hole turbo a series than Home and Away ( and I only know that’s on some thing called a TV) is it possible to turbo trough a HS carb be it 1" 1/2 or 1" 1/4.

Edited by PaulH on 8th Jun, 2008.

Hi,
I'm not going to say it's impossible as I don't know.
But you'd have all the hard work to do, I've not heard of anyone running one...
Cheers,
Gavin :)

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Yes, you can convert them.

I am currently looking at converting a 2" HS to blow through turbo use, so will let you know how it goes once i finish. I should write a little write up, as it seems these questions get asked a lot.

From what i can tell you need to do quite a few mods:

1. Seal throttle spindles
2. Seal dashpot
3. Possibly stronger spring on choke lever as boost can force the jet down
4. rising rate fuel pressure regulator that increases fuel pressure with boost.
5. Plugged fuel bowl vent etc.
6. This is the one i think you have to experiment with - either a restrictor plate to the inlet of the carb, or a boost line from close to the turbo to the fuel bowl.

Basically carbs work more on gas speed than density, so they have troubles metering when the difference in pressure between before the carb and the bridge in the carb is small. A restrictor plate before the entrance of the carb creates a couple psi pressure differential so that the pressure in the float bowl is higher than the bridge - forcing fuel out the jet.

Another way i have heard of doing this is running a boost line from close to the turbo straight to the fuel bowl. The pressure here should be a couple psi higher than what the carb see's due to loss through the IC / pipes etc.

I'm going to try get mine working with the 2nd idea, and if that doesnt work i will try the restrictor plate.


Oh and you may have to foam fill the float if you are running high boost. They can fail at highish boost levels apparently

point 6. is the crucial one as you say. The metro turbo HIF with the plenum fitted is a great solution to the problem of keeping the fuel pressure above the charge pressure.

Sealing the dashpot and spindle are probably a good idea but not trrictly necessary IMO, as long as the spindle bearings etc. are all in good nick.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Thanks lads,
Ill have a think on this one need to do some research on this one me thinks
Has any one got any pic or info on how this metro turbo plenum over came this presure difference problam
Regards
Paul

There is a restrictor ring in the plenum, this reduces the pressure across the jet buy a few psi while the float bowl sees the full pressure in the plenum.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph