Club G40 Forum

hi all,
can anyone give me info or diagrams on how to do the boost return mod on my polo g40.
i had it done on my old g40 and liked the boosting noise at high revs!
i know you need to keep them lubed up but not sure on wht to remover or if anything needs to be added?
please pm me if you can help

thanks dave

Quote from: cheys03 on July 01, 2010, 05:39:53 PM
I have this document on my PC. Unfortunately there are no pictures. From memory I saved it from a now unmaintained Polo website that looked to be someone's personal site. I am not the author. All credit goes to the author, whomever he/she may be.

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Boost return removal modification for Polo G40
What you will need to carry out this mod:-

1 metre of hose 1" in diameter.  B&Q sell pond hose in this size.
A bottle of your choice – 1 litre Coke bottle will do.
Some spare bolts to block up the vacuum lines.
Some metal sheeting if you don't want twin induction kits.
Blue Hylomar sealant or equivalent.
If you want twin induction kits then you need an inlet collar, a 2nd induction kit and 3" hosing.
Spray grease to lubricate the charger periodically – PSD sell this.


Step 1: Removing Charcoal Canister and Purge Valve (aka 'flying saucer').
Firstly, remove the airbox from the car (obviously, if you have an induction kit instead, just remove that or move it out of the way as necessary) After unclipping the top, remove the filter and remove the 3 nuts holding it in place.  Slacken off the jubilee clip on the charger intake hose connected to the airbox lid and slide it off.  Remove the airbox from the engine bay – remember to block up the pipe going to the supercharger to stop anything getting into it – I used some kitchen roll.  You will now see 2 pipes which are connected to the charcoal canister.  (The charcoal canister is located in the hole at the bottom of the pic below – I removed it before I took this pic however!)  Remove the charcoal canister by removing the 2 bolts holding it in place, then slide the 2 pipes off.


Below is the charcoal canister after removal:-

The next step is to remove the purge valve (some people refer to this as the 'flying saucer').  This can be seen in the picture below:-

The small vacuum pipe to the top of the valve goes to the throttle body, simply bung it up with a small screw or bolt as close to the throttle body as possible.  The pipe from the bottom of the valve goes to the inlet manifold, bung that up with a screw/bolt as well.  Smear both screws with a little silicone before screwing them into the pipes to ensure that both are airtight.  The other pipe used to go to the charcoal canister so that can be discarded along with the purge valve.     

The only pipe to leave unblocked is the clear plastic pipe that comes from under the car that used to connect to the charcoal canister. This is the fuel tank breather and needs to breathe.


Step 2: Removing the Boost Return hose and one-way breather valve.
Remove the boost return hose from the throttle body and rocker cover, then remove the black plastic mushroom shaped one-way breather valve at the other end of the hose.  This valve is located under the inlet manifold at the back of the engine block.  It just clips onto the metal breather pod which is pushed into the back of the block. 

Removing the boost return hose from the throttle body to the rocker cover:-

One way valve located below the inlet manifold:-

One way valve removed from the outlet pipe.  Note the clip on the right hand side that clips it onto the pipe:-

Once you've removed this valve you'll be left with an outlet sticking up from the breather pod:-

Fit the end of the 1" hose you've bought over this breather dome's outlet pipe and route it to where your catch tank will be:-



Step 3:  Fitting the catch tank.
Drill/pierce several holes in the neck of the bottle – these holes will allow the vapours to vent from the catch tank.

Decide where you want to keep the bottle in the engine bay (the bottle will be your catch tank) and secure it to ensure it won't foul any other engine parts.

Making sure the hose doesn't kink, route the hose to your catch tank and shorten the hose to the required length.  Slide the hose into the top of the bottle and secure it using Duct tape or cable ties etc.



Step 4:  Fitting the Supercharger blanking plate.
Remove the boost return hose that runs between the rocker cover and the supercharger.  The hole that is left in the rocker cover does not need to be blocked up as it is simply a straight-through bypass tunnel.

The final step is to cut the metal sheet to the required size to cover the inlet on the supercharger, then mark out and drill holes for the bolts.  You should be left with something like this:-


Smear some of the Blue Hylomar sealant onto the plate and bolt it in place.  Obviously, if you opt for twin induction kits you would fit the second kit onto the supercharger instead of making a blanking plate.

Blanking plate secured in place on 2nd supercharger inlet:-

All you need to do now is refit the airbox/induction kit and you're ready to go!



Step 5: Maintenance.
Periodically, you will need to lubricate the supercharger to ensure smooth running and avoid killing it!  Pitstop Developments sell spray grease that is perfect for this task.  Some people have stated they do this every 500 miles, and others every 1000 miles.  I don't do much mileage so will probably just do this once every month instead.

To lubricate the charger, take off your blanking plate then start the car, hold the revs at around 2k and spray the grease into the charger for 10 seconds.  Refit the blanking plate, resealing with gasket sealant if necessary.

see the merchandise link and PM hayesey or peteg40 for the correct PTFE grease, the club sell it

great repl thanks mate

Dont spray for 10 secs though. Maybe 2 secs.

i was at jabbasport last friday getting my charger serviced and i asked them about the boost return and they advised me never to do it as even if you do keep the inside of charger lubed it gets gunked up and can destroy the charger alot quicker...not so sure if thats true just what the guy who rebuilds chargers at jabba sport told me :)

I've also herd the same.

well every one has their own opinion, personally I'd much rather my charger is lubricated by PTFE grease than the horrible oil & water shit that comes out of the oil breather.  Where people go wrong is by using the wrong grade of PTFE grease (the stuff you can buy in B&Q is only fit for lubricating gate hinges with) or putting miles too much of it in.

Quote from: alan gorst on January 24, 2011, 11:12:08 PM
i was at jabbasport last friday getting my charger serviced and i asked them about the boost return and they advised me never to do it as even if you do keep the inside of charger lubed it gets gunked up and can destroy the charger alot quicker...not so sure if thats true just what the guy who rebuilds chargers at jabba sport told me :)

Well Brian Ok'd it on the boaksey's race car and that was sponsored by Jabbsport!

alan is right, my charger died and inside was like a big dirty earwax party.

I would not advise it, but like haysey said if you put too much in it can gunk it up

id personally leave it as it is, tried and tested and all that

well im guessing he has changed his mind on it lol as he told me if i wanted to gunk charger up and destroy it to just leave the way it is....seemingly not worth it for the sake of a change in noise

Quotealan is right, my charger died and inside was like a big dirty earwax party.

well that's because someone had put miles too much ptfe in rather than because of the boost return being removed. 

hmm well it still adds to the discussion, i personally do not think i put too much in at all, but it is worth baring in mind

then how did it get in there? ;)

Earwax fairies.

been running my g40 with no boost return never had a problem!

ive just done this mod and my engine is running like poop, got the gt inlet and dewedged tb, r1 charger but cant get it running nice, put the boost return back on, minus the breather to stop crap in the charger (blocked the breather hoses) but no change, no map yet but jus wondered if there was a technique to home tuning till i have run the charger in and rr tuned

did you do the boost return at the same time as the dewedged TB?  Specifically how is it running like 'poop'?  Just different feel to driving or an actual engine problem?

Quote from: Jezza-7 on January 24, 2011, 10:56:49 PM
Dont spray for 10 secs though. Maybe 2 secs.

Indeed!  Spraying for 10 seconds is really bad advice, it's this reason that people find all this excessive build up of PTFE gunge in chargers.  Like Jez say, 2 seconds is about right.  I used to give mine a few short (maybe 1/2 second) bursts.

engine not running right is something wrong, not the boost return mod or needing a remap.  Is the ignition timing right?  Although like hardchargin says, need more info really.

ignition is spot on, i believe its the wank chip prev owner put in thats mashing up the air waves, runs great till you put ur foot to the floor then it runs outa puff, little bit of boost but its not sending me up the road like a roket, evan with a blown charger b4 i sent it away it was faster, its defo over fueling tho, i can smell it, and my poket can feel it lol,, wat dya recon, im nearly at the required milleage to give it a proper blast past 4000rpm then goin to see san speed to get a diagnosis and a tune hopefully,cheers guys

also its not chugging or anything, the delivery is still smooth but without the g smiles or head stuck in the seat values

ISV pipe disconnected from boost hose - boost leak.   Have you got a boost gauge?  Probably boosting 0.4bar if thats disconnected or leaking.

That or an overfuel, could be chip if did it before aswell - you haven't changed your injectors have you?  Running greens for instance without the corresponding map would overfuel it causing chuff all torque and power and be very thirsty without having running problems.

i had a gt injector rail on it, so i put the g one back on still with yellows on it and i have the g smiles again, i think its defo time for a map, boosting well now, wat do people think of san speed in bexleyheath, no boostleaks it was jus fueling wrong but now its gravey again, is a custom map th route to go or just generic

i never need any  oil spray in my glader, i have ccv bypass a lot time and milles, never have a problem!