Wont Hold Boost Pressure In 5th And 6th

TheDon · November 23, 2004

over the past couple of days the charger has been feeling like *******!

Now when im accelerating in 5th and 6th (less noticeable in lower gears) teh supercharger looses pressure at around 4500 revs and drops from 0.35 bar to 0.15-0.2 bar. with a distinct whine/squeel associated with the drop.

I have tried tightening the belt on my own but cant get enough pressure on the pully wheel (i think im not anyway) to tighten it any more than standard. will try and get help though.

I have a full toolkit with me here at work (im in hatfeild peveral - junction 20 of the A12, Essex).

But realy am worried as i have to drive back to junction 3 of the M25 - about 40 miles of motorway.

Is there something seriously wrong here? am i endangering the engine?

TonyGoose · November 23, 2004

Hose leak between blower and throttle body somewhere ?

TheDon · November 23, 2004

thats certainly possible. bet its somewhere that i cant get to.

My only problem is that it is dark when i leave the office!! no fun. may try n see if i can pop out there n have anotehr look. only problem is that as it is only in top gears i will have trouble replicating (while not moving) the pressures.

any suggestions on how to test it?

Monster-Mat · November 23, 2004

id check the hose connectors and clamps, especially those going into and out off the intercooler.........i had this problem

also check the by-pass valve is free to move

TheDon · November 23, 2004

so far have checked (and oiled) the bypass assembly and is fully free flowing. i will have to wait till tonight before trying to check the fron hoses.

Will changing my hoses to the TDi silicone ones help lessen the chance of future slippage?

Will also try re-tightening the pully belt to make sure its not that. althought the noise does seem to be predomenantly on the left hand side when driving. will focus my attention there.

Are there any kind of sealant/lubes that will help seal better when putting the sleves back on?

dark_is200 · November 23, 2004

Adjusting the belts is a two person job I think, last time I had them adjusted was at TDi - haven't slipped for 9 months. TDi used a special tool they have to get the adjuster as tight as possible (think its called a crowbar but mark can confirm that!). Also, make sure you've got the belt on the right part of the pulley, I don't know if its just me but the S/C pulley on my car has more grooves than the belt with the belt on the wrong set of grooves it was pulling down too much on the S/C and causing lots of slippage.

Monster-Mat · November 23, 2004

the belt SHOULD be changed every 10,000 miles!!

do not over tighten the belt, it puts undue stress on the cradle and the compressor bearings.

also at every belt change the pulley tensioner needs inspecting for "rim rock" (play in the bearings)

the belt should only be tightened till there is 5-10mm play in its movement on the longest run(longest free lenth of belt)

as for hoses, i ordered new silicone hose from Demon tweeks, and cut my own new pipe connectors, adding 20mm each side

TheDon · November 23, 2004

cheers for that, will definately get another person involved!!! i have a nice big special crowbar that i should be able to lay my hands on! lol

my belt has all the groves covered on the outside leaving some open on the inside? is that correct?

TheDon · November 23, 2004

what diameter hoses did you order, is it 51mm diameter (internal?)

petejenkin · November 23, 2004

so far have checked (and oiled) the bypass assembly and is fully free flowing. i will have to wait till tonight before trying to check the fron hoses.
Will changing my hoses to the TDi silicone ones help lessen the chance of future slippage?

Will also try re-tightening the pully belt to make sure its not that. althought the noise does seem to be predomenantly on the left hand side when driving. will focus my attention there.

Are there any kind of sealant/lubes that will help seal better when putting the sleves back on?

←

I think you would suffer pressure loss in any gear if you were loosing pressure through a hose. Im not an expert by a long chalk, but as the s/c is driven directly by the crank, the demand for air is governed by the throttle, but the supply of air is governed by the crank speed. Looking at it, I think it could be more likely your belt that has stretched. If your belt is slipping this would cause the noises you hear. The reason why it doesnt happen in the bottom gears could be because in 5th and 6th the crank is rotating slightly slower so when the engine is running high the belt grabs a bit better. - Just a theory - tell me to shut up if Im waffling :P

RoadRash · November 23, 2004

Maybe the engine sucks so much air at 5th and 6th gear and 100% throttle opening and over 5000rpm, that the SC can't support that much air.

6 Cylinders suck much air, maybe more than the SC can give at high rpm.

;)

That could be a reason for boost loss.

Monster-Mat · November 23, 2004

dont use a crow bar to set the belt tension.

as pete has pointed out.............and i was hinting at in my previous post, your belt needs looking at .

the rest needs checking aswell.......................

Monster-Mat · November 23, 2004

as for hose size.dinny remember..i just used some Vernier Calipers to measure my std hose.i will dig around, but i think i still have some of the wide bore stuff for the inlet pipe

Gord · November 23, 2004

aido had this problem it was the hoses that needed nipping up that all (air leek) ps dont put to much tention on the belt, as the s/c is free moving with no resistance at all.

TheDon · November 23, 2004

but who to check ????

I will post up some detailed pics later on of my set up as it is.

Will also check the belt tension properly and adjust accordingly (without a crow bar!)

I do a lot of motorway miles and also have a drive that i sometimes knock with my bumper so maybe it could be the front pipes and the rubbers.

will just take it easy till then i think.

am gonna do my best to work on the car tonight. might have to take it to bluewater tho because i dont have a covered (or lit) driveway.

Gord · November 23, 2004

hoses are 3 diff sizes.

aido · November 23, 2004

Chris, I had both problems, the slipping type noise, the belt was tightened first but was still getting an unusual noise - like Gord says a couple of the pipes needed tightening and that fixed the problem completely.

The car felt ***** as boost was lost at high revs due to the leakage and then the car was as slow as a normal IS while building boost back up only to lose it again!

TheDon · November 24, 2004

gord, ya were on the ball with the pipes.

AS it was a little wet i took the car up to bluewaters lovely dry indoor carpark, very well lit!!! lol and proceeded to tighten the belt so that it had 5mm of slack, it was running with 12-15mm slack!!!

Every one of the clamps needed tightening. some of them gar too much, lol.

Car has never felt this powerful since it left the garage for the first time!

Its boosting quicker and feels soo much more taut in the power delivery.

Cant wait to get my silicone set now!

Thank you so much everyone, your the best!!!!!

Gord · November 24, 2004

nice one chris, you have to keep your eye on them clips mate.

Monster-Mat · November 24, 2004

id check the hose connectors and clamps, especially those going into and out off the intercooler.........i had this problem
also check the by-pass valve is free to move

CoughCough.who mentioned thos clips :D

TheDon · November 24, 2004

i think you should all share the thanks, lol.

BIG THANK YOU TO YOU ALL!!!

Am off to TDi now to pick up some of the blue silicone ones.

Hoping that they wont move as much as the black rubber ones.

Plus they will look nicer

TheDon · November 26, 2004

well i have just finished fitting all the silicone replacement tubes! and bloody hell! its even better than before!!!!

Definately recoment this to anyone who has the supercharger. and all for £40.

The car feels like its got its balls back now and just pulls and pulls. will be keeping an eye on the jubalee clips tho!

PhoneDrome · April 16, 2005

I also have the supercharger belt squeeking. Everytime I shift in high revs (above 5500 1/min) it slips and squeeks.

The belt tensioner looks like it is not possible to tightned it any further. Seems that it is at the end of the slotted hole.

However.. how do I tighten the belt. Just loosing the tensioner bolt and press it (if that is possible)?

BESTY · April 16, 2005

I also have the supercharger belt squeeking. Everytime I shift in high revs (above 5500 1/min) it slips and squeeks.
The belt tensioner looks like it is not possible to tightned it any further. Seems that it is at the end of the slotted hole.

However.. how do I tighten the belt. Just loosing the tensioner bolt and press it (if that is possible)?

←

use a 790 mm belt,i did,better ajustment.