Losing Boost

[vw_john 10]

Charger rebuilt 6 months ago stage 4, put a boost gauge in about 2 months ago achieving a max boost of .8bar done a max boost reading again today of .6bar. I mean .8 bar is low on a stage 4 with a 68mm pulley but .6 is stock! i cant see any boost leaks in the usual places, but the fact that its degenerating seems to me like the hole is getting bigger? i have replaced a leaking isv aswell and the boost is still dropping. WTF!

Rant over, i just feel sad that my mates polo gt is only a little slower and its a 1.3 N/A.

[owen g60 10]

There is a thread in the wiki done by Darren from gwerks on how to check for boost leaks.

Use this and you will be surprised where you find leaks

[vw_john 10]

I did read it but didn't really fully understand it. =/. I'm worried my charger might be about to grenade. I'm getting a noise like a child screaming on full throttle. Also at idle my boost gauge neede bounces violently above and below -.5bar

[owen g60 10]

which part of the guide are you not sure of?? ill try to help if i can

 

sounds to me like a boost leak.

 

I had a similar issue after fitting my refurbed charger.

 

It boosted pretty well for a few days then i couldnt get above 4 psi.

 

I followed the guide and found a fair few leaks that hadnt noticed before .

 

 

On a side note do you get a high pitched whistle as part throttle??

[vw_john 10]

yeah I get the whistle, thought that was a normal thing with the boost return delete....

well I get the blocking off of the boost return? via using the disconnected linkage. but using soap and alike i get lost,

and how would you check for leaks after the TB? like at the injectors?

Cheers for your help mate!

[owen g60 10]

the soap is just a really thick mix of washing up liquid and a tiny bit of water.

 

use a paint brush and put it wherever there is a join in the pipes. when you close the throttle body if there is a leak the mis will bubble. you will know when you find a leak.

 

if you find one tighten the jubilee clip and repeat.

 

even use it where the 2 parts of the throttle body join together.

 

if your injectors were leaking then you would smell/see the fuel coming out of them.

once you have confirmed there are no leaks then i would look at the charger.

[vw_john 10]

Alright, cheers mate, I'll have a blast at that tomorrow. How would I get to the intercooler? and would I really see that much gain from just tiny leaks?

[owen g60 10]

To do the inter cooler you will need 2 people.

 

Jack the passenger side up and get someone to put the mix on the joins/watch as you close the return

[vw_john 10]

Nice, cheers. I'll report back tomorrow running a nice 1.2bar!

[Supercharged 2]

Also check you are hitting full throttle, ie the WOT switch is activated with the throttle to the floor...

 

Should be making at least a Barr on a stage 4.

 

Best was to check for leaks is to pressurize the system in some way with the engine off - I used an airline attached to the boost return blanking plate to do this.

[vw_john 10]

well when i manually turn it i hit the switch and hear it clicking, what would it do if that was not pressed in?

I haven't got access to an airline, and surely the butterflys in the TB cant be airtight? or would you block the end off before the TB?

[owen g60 10]

Good point.

Also get someone to stand on the throttle pedal whilst you check the boost return flap is closing all the way

[vw_john 10]

just done the flap check, it is closing all the way but if i push it back up. the flap opens while the throttle is down? is that right? it doesnt seem right haha

[owen g60 10]

With the throttle fully depressed the flap should be shut

[vw_john 10]

the flap shuts completely, but when i stick my finger in to feel it, if i lightly push against it, the flap opens up so i suppose on full throttle as the flap is angled this could push the flap open?

[owen g60 10]

hmmmm... if i remember correctly there is a nut on the linkage for the flap that can be adjusted to stop this happening

[vw_john 10]

Im going to take the tb off today have a look. could someone with a g60 tell me when the boost return flap fully closes? is it on full throttle or just before? i seem to remember on a spare one that it closed before full throttle cheers guys

[owen g60 10]

I believe it should be before full throttle.

 

I don't have my spare to hand to measure.

 

If I remember I'll get some pics later

[JMC 0]

vw_john, do you still have the black plastic box on the right hand side of the charger? If so this is high up on the candiate list for being the problem - they are prone to leaking through the seal round the middle, and it makes a really high pitched squeal.

[vw_john 10]

I got rid of the silencer box a while ago now.

I'm stumped, I had the TB off earlier, and it appears that the boost return is designed so that it lets a small amount of air through on WOT. on both of my throttle bodies the butterfly can be relatively easily pushed open on WOT. put the heavier of the two springs in, and im still getting poor boost, going out with the soap in a sec...

[Album56 0]

CO pot sealing ring?