Something different that you guys can help me with

[Pepe]

Ah cool thanks for clarifying that!

My t piece WAS 2 male brake line connectors welded back to back then a t piece(3way female) off a mini, was ugly but worked a treat!

[hayesey]

yeah I was just talking about the fittings into the engine itself for the feed and drain.

[Pepe]

Ok folks so I've bought a refurbed charger with 0 miles since refurb, Anyone know where I can get a crank pulley for the g40?

Also is there any issues with running one longer belt running the water pump alternator, and one running the charger?

Or can I use one belt?

[PeteG40]

I have a crank and alternator twin vee pullies oem.a few marks. 10 quid plus post

[Pepe]

Yeah please man that's great, they will be off to the powder coasters with a ton of other parts so that's no real issue!

[GR40]

Ok folks so I've bought a refurbed charger with 0 miles since refurb, Anyone know where I can get a crank pulley for the g40?

Also is there any issues with running one longer belt running the water pump alternator, and one running the charger?

Or can I use one belt?

The reason they went with the twin v belt originally was to maximize friction (not the most effective setup to begin with). The belts will start slipping at high rpm or hard acceleration and you will experience a drop in power. Other than belt wear and power drop, I doubt you ll have a problem with just one belt. I would still suggest you go for 2 belts though. You could set one for the water pump, alternator and charger and one just for the crank and charger. One could tension via the charger and the other via the alternator. This way you could use different length belts. A general warning though, since we are talking about belts, avoid over-tightening the belts with any setup as the lader doesn't appreciate it.

[Pepe]

I would have gone single belt if I couldn't get the pulleys, PeteG40 you have pm also! I've swapped the absolute dog turd standard alt out for a 90a bosch one (from a rocco) and I've got an air ride setup waiting for my broken wrist to heal before I fit it so hopefully the twin V-belt setup will help out there, my only real concern with all this is the water pump but if I'm doing v-belt I think my buddy's are gonna be called upon for a customer waterpump pulley! but as you can see it looks fairly straight forward piece of engineering might even get away with it if we weld extra flange on to it so the belt runs round everything just keeping it all in check!

[Pepe]

so my charger turned up today its a completely bone stock refurbished charger, now ive offered it up in the engine bay and i think rather than make my own im going to try modify a standard g40 bracket to mount it and also i could do with a outlet dome/elbow if anyone has these parts let me know im keen to purchase them!

[PeteG40]

I have an outlet dome - call it £25 posted with the 2 pullies?

[Pepe]

Quick one, I'm pretty sure the r5 carb Won't have a boost return feature so that will obviously be getting deleted on the charger, is it literally just a case of bolting a blanking plate on and giving it a squirt of the grease every now and again? (Mileage?), if I was to go for a secondary filter would I also need the spray grease?

[G40supercharged]

I think you will have issues running a charger in blow through with no pressure regulation or bypass mechanism.

If you ran the charger suck through (carb before charger) then it's dead easy as the carb just operates like normally aspirated. The throttle on the carb limits the air through the charger and the flow/pressure will go down when you close the throttle. Old Bentleys and MGs in the 1930's used this set up with a Rootes type charger driven off the front of the engine. Unfortunately I don't think the G40 charger would survive having the petrol air mix going through it.

Running blow through means the charger intake is effectively fully open all the time and it will try to flow maximum air into the manifold all the time. On a closed throttle in the carb the pressure will build up to the maximum the charger is capable of so you will end up with a high idle speed. I think it would be really hard to get a carb to run well like that; pressure will go down with increasing throttle rather than the other way round. You would need some sort of pressure regulator downstream of the charger to vent off excess pressure build up. A turbo on a R5 or Metro has the turbo bypass mechanism that limits the maximum pressure and a turbo doesn't do much unless the engine is at full throttle. 

Unlike a turbo the G40 charger flows roughly the same (per revolution) at all engine revs. Its the inability of the engine to take in the air at the top end of the rev range that gives the peak boost levels. When the throttle is not wide open the G40 throttle body has a mechanical bypass valve that effectively makes it normally aspirated to prevent unwanted pressure build up. A stock G40 on standard 75mm pulley flows enough air for something like a 1.8 litre engine. If you attached a G40 to a 1.8 engine you would see no boost pressure. On a 2 litre engine it would be slower than normally aspirated. As you have a 1.5 you will see less than the normal boost in a 1.3 Polo. That's not a problem; I would expect a maximum of 4 or 5 PSI under full throttle which will give a significant performance boost and won't melt the engine.   

One option is to enclose your existing carb in an airtight box (you could hide the whole thing under the existing air filter housing). You then pressurise the box with the G40 and a pressure regulator (flap acting against a spring). The complete carb would see the pressurised air so you just need to up the jet rather than use a special turbo carb. I think the early Lotus Esprit had this sort of set up.

Alternatively get a G40 bypass valve and link it up mechanically to the carb throttle cable. You then run normally aspirated until full throttle. 

[GR40]

He was just asking if he should blank the second inlet port on the charger! The G40 engine has a return that picks oil fumes and since he cant have that with the carburetor he was asking of what to do to keep the charger oiled.

[Pepe]

Ok you've raised some interesting points there. Just an idea I'm gonna throw your way as you seem to know your stuff.

would I be able to have a pipe going from charger to carb and then where it connects to the carb have a return back to the charger with a butterfly with a spring on it? I'm thinking that it will take the path of least resistance when the throttle is shut and then when it's open it's creating a vacuum anyway so will pull the butterfly shut and then  be pulled through the carb

[G40supercharged]

The bypass on a G40 only goes back to the charger to limit the noise (like a recirculating dump valve). You can just vent any excess pressure to atmosphere. If you look at your G40 charger you will see the main and bypass inlets are exactly the same and connect into the same bit of the charger. (On the original G40 versions there was only one inlet and the bypass join was part of the rubber pipe.) The oil breather connection in the G40 bypass hose is mainly there for emissions reasons; it burns off the oil vapours rather than just venting them to atmosphere. A secondary effect is lubricating the charger a bit but I'm not convinced that's why VW did it. If you wanted you could attach your oil breather system to a blanking plate on the second G40 inlet. (It will currently connect to your airbox somewhere.) Probably better off just venting the breather to atmosphere and using a blanking plate on the second inlet. Then apply small amount of spray grease occasionally (others can advise on how much/how often).

I would go for a mechanical bypass valve linked to your carb cable and dump excess boost direct to atmosphere. This should be more reliable and will allow zero pressure off boost. The turbo carb is more likely to work OK like that. I think that a turbo carb needle is specially shaped to match the boost/flow characteristics of the car it was designed for.

In terms of making it work easily a BMW mini Eaton charger in suck through is less trouble (apart from the belts); also no oil feed to worry about.

[Pepe]

the r5gtt carb has been used a few time in supercharger builds and seems to work well,, im going to stick with the glader now as i have bought nearly everything i need charger wise, just need to modify the bracket to fit to the 1.5 engine, play around with pulleys (going to try use the same belt length as the g40 for ease and availablilty but if not longer ones wont be too hard to source), the oil feed return isnt a problem as ive bought an oil filter housing with an outlet so my t-piece will go in there with my oil pressure sensor and vdo twin pole sender and the feed for the charger will go directly in the side of the head. the return is as simple as taking the sump off marking it with an X and handing that and a fitting to my mate. i might just do that with the oil breather or i might plumb it into the carb as it is now see whats going to work best

that just leads me onto the fueling ive just contacted a guy (kris hughes) about his 1.0 eaton'd mk2 polo which uses the r5gtt carb and asked him what hes done to combat the high idle/carb pressurisation thing you mentioned and i am waiting to see what he says but i am thinking of taking the boost pipes over the drivers side so i can fab up something using the throttle cam and a butterfly 90 degrees to the carb butterfly so when the carb is full open the bypass is fully closed and vice versa