I'LL GIVE £100 to anyone who can sort me ongoing boost problem..

[Slim]

ok... done the soapy water test today.... no leaks in the main boost circuit... im 100%sure no leaks (from turbo to carb top + actuator to carb base)

the one im thinking that may be affecting it (hoping its it).. is the vacuum pipe going to the oe boost gauge... ive taken it off now n blocked it... wanted to do another test run but the belt keeps slipping/breaking off!! the pulley has a ridge on it!! so no more testing til i get another pulley (which ive ordered today from renault) .. i js hope it is this pipe that was causing the issue cos this is the ONLY one ive not touched before.... il do a test run soon again.

il keep you guys updated (and yes i also strongly think it must be a leak somewhere ... obvoiously) but this ones not an easy one...as ive had many people look at it.. including k-tec! and many other people who know these cars inside out.... n im not so bad myself (not tryin to big myself up) ..... no ones ever found it.... so im js baffed!

OH 1 More thing...

Can someone pls re-assure me.. it cant be anything to do wiv any valve's or engine component or exhaust blow or somthing... cos as far as im aware doesnt even matter if u have no exhuast....

[Slim]

oh and did the sight go down or is that just me??

[Slim]

oh... and erm... sory to bother you again... but on my actuator.. i only can find a long number wiv a -30 (looks like) on it.... :P

does that make sense to anyone...

[Slim]

IVE DONE IT!!!!!!!!!!!!!!!!

ok.. so after years of having this stupid problem... it ended up being the only thing i ddnt change....

i js blocked off the pipe from the carb going to the standard oe boost gauge.. and voila!!! STABLE BOOST AT LAST!!! and she feels so much better!!!

thanks for the help guys..

[markey b]

well done for sortin it, plus you've saved a ton

[Shane P]

May be worth getting the little anti-belt jumping metal piece, that attaches to the water pump, to go with your replacement bottom pulley

[r5 rich]

now i think you should donate the £100 to rtoc for help on this topic

[Slim]

May be worth getting the little anti-belt jumping metal piece, that attaches to the water pump, to go with your replacement bottom pulley

OH YE!!! thats wat i need too!!! thanksss...... im gna look for a spare before i buy it this time..

Anyone got one spare??? lol

[Slim]

SCRAP THAT COMMENT ABOUT ME FIXING THE BOOST PROBLEM...!! ITS STILL THERE

OFFER STILL STANDS TO ANYONE WHO CAN FIX IT.....

[Slim]

The only thing i can think of next is either the inlet manifold (which looks and sounds fine)... or the engine!!!! wat crap!!

[Slim]

i thought it was ok before.. cos i disconected the std oe gauge... but also ran the actuator straight to the carb... I thought it was ok but it still had a 2 psi spike at 12psi,,, but the spike was lower becos i ran less boost. Now ive put the incar boost back... wen runing higher boost ie 16... it drops 4-5 psi....

the hight ther boost i run the more of the boost drop....

PLEASE HELP ME SOMEONE... im really thinkin of buyin another 5 just cos of this.. but i dont want to cos ive done so much...i know it must be somthin someone can fix!!!!!

[Scoff]

It will be one of three things:

1) Boost leak
2) Poor actuator
3) Throttle adjustment

1) How did you check the boost circuit ? The best way is to block off the air filter and put an air line into one of the carb ports, it should not leak away fast.

2) Have you tried a better actuator ? If its the standard twin-port, have you tried re-connecting the front port ?

3) Have you checked that you are getting full throttle ? Have someone press the pedal to the floor while you check that it is moving the linkage on the carb ALL of the way, not just 1/2 or 3/4 etc

[Slim]

It will be one of three things:

1) Boost leak
2) Poor actuator
3) Throttle adjustment

1) How did you check the boost circuit ? The best way is to block off the air filter and put an air line into one of the carb ports, it should not leak away fast.

2) Have you tried a better actuator ? If its the standard twin-port, have you tried re-connecting the front port ?

3) Have you checked that you are getting full throttle ? Have someone press the pedal to the floor while you check that it is moving the linkage on the carb ALL of the way, not just 1/2 or 3/4 etc

1) i have changed most of my boost pipes to new ones... only old one is the turbo2charge cooler pipe.. which i took off many times to double chek.. il tripple check it... boost circuit goes from turbo to charge cooler,, to intercooler - hard pipe (changed) to carb)

2) yes a while ago... but this is yet another new actuator.. i js got the turbo rebuilt and this actuator has -30 on it :S yet im sure i saw -31 on it before i got it back from turbo company (they sprayed it)

3) yep checked that


---------------

could it be like a valve or anything to do with the head?? or inlet manifold?? im gna try changing the inlet manifold next....

if i do wat u say in 1) ... which i want to do... would i leave all the vacuum pipes intact?

[Slim]

Im just getin sick of this and very upset cos its been like a 2 year ongoing problem.. ive really had enuf of trying.. thats why i js wna give it to someone to sort!!! but il have to keep tryin if no one wants to try.... if i cant.. il end up buying another 5 wich i really dont wna do

used to have a ktr350 rollerbearing and sold it cos i thought it was that... then moved to various turbos.. now on another t28.. and still

[Scoff]

1) then you need to check the whole boost circuit, by pressurising it like I describe. Can you be sure that your charge cooler or intercooler don't have leaks ?

2) So a possibility then. Would be worth trying something different, one that you know works. What is the pre-load set to ? About 4mm is normal.

3) Fair enough, rule that one out then.

[Slim]

would it really matter the preload?? i dont really understand preload in mm... all i know is that i set it to like 10psi.....then i stick the incar boost controll on...

could it be anything on the head?
am i correct in saying even if i had a big hole in the exhaust it shouldnt matter??

[Scoff]

An easier (but less effective) test for boost leaks is this:

1/ Remove and blank off D/V if present.

2/ Remove air filter. Find a sheet of metal or something sturdy that you can use to press against the air filter pipe to block the inlet to the turbo.

3/ Leave air filter pipe open to begin with.

4/ Start engine

5/ Hold revs at 2000rpm

6/ Place metal sheet/whatever over air filter pipe to block the engine's air supply.

7/ If the system is air tight then the boost pipes will suck themselves in flat and the engine will stall quickly.

8/ If the engine continues to run, or you can hear air being sucked in somewhere, you need to investigate further.

[Scoff]

Preload is the amount you have to pull the actuator to hook onto the waste gate. Un-hook the arm, make sure the gate is closed and look at the distance between the 2.

[Slim]

preload..oh right.. ok.. ye its about 4mm

i js went for a run... wivout the intercooler and chargecooler...

from turbo straight to carb.....

Still same problem.. SO ITS 100 % defo not those 2

[Slim]

il try that scoff ... but wat if i cant hear any leaks and it still runs?? cos its quite loud n all... thanks for tryin to help tho..

could it be a valve not sealing or somthing like that? (i dont know much about valves n heads) but the engine was rebuilt recently tho.. but ive had the prob even before that..

[Jimmy_GTT]

Do you have now a bleed valve fitted?
Disconect it.

I don't think that a valve problem can cause such problem but youu can try a compression test.

Are you running on cup mod?
Check all the pipes from carb to turbo, carb to fuel pressure regulator. Maybe there is only a little crack on one of the pipes. Disconnect them one by one and pressure test them with a foot pump...
Have you changed the fuel filter recently? Changing the fuel pressure regulator?

[Slim]

"carb to fuel pressure regulator".... this is where i dnt know how..

[Slim]

p.s i need a bleed valve to run any more than 14psi.. else i cant get the actuator on... rod is kinda hard to pull

[Slim]

there a 2 pipes that i am not familiar with (and i cant see the other end)

1) from the carb top -- the black pipe shared wiv the oe boost gauge
2) from the back of the inlet there are 2 pipes. one is blocked off.. but the other i cant see where it goes...

could it be any of them?? anyoe knw where they go???

[Slim]

can anyone tell me how to test the fuel pressure regulator?? do i js blow the pipe that goes to it?? which one is this?

[Jimmy_GTT]

can anyone tell me how to test the fuel pressure regulator?? do i js blow the pipe that goes to it?? which one is this?

I think you can pull of the pipe from the carb top which goes to the fuel pressure regulaator, and pressure test it. If you are running around 17psi @ manifold, than it have to keep a 20-21psi without a problem.

I'd really take the bleed valve out. They used to have a ball with a spring in it to work as a one way valve but I'm sure it can cause the problem.
I suggest to take it out and simply put a T piece in its place. It should be in the tube which goes from the carb to the actuator. And the 3rd connection should be open. But you have to take care not to overboost. Put some restrictor to this open pipe.

The 2 pipes on the back of the inlet:
- one goes to the brake servo
- 2nd is breather system (I think this is blocked)
But they are connected to one way valves in the inlet.

[Scoff]

Jimmy has a good point, it might just be your in-car adjuster causing the problem (long/thin pipes too and from the in-car adjuster cause spiking)

Do as he says and remove it. Use a normal under bonnet bleed valve instead (jimmy, only the PRV types have a ball and spring, the normal under bonnet valve will work the same as your T-piece idea)

[stu21t]

you will nearly always have a boost spike anyway.
have you been in another car with a similar setup and not had one?
im just wondering if your trying to cure something thats not there?
i have a much bigger spike than 4psi in my car. its nothing to worry about if youve tested for faults and can find any.
only way to run without a spike is with a proper boost controller or air injectors(obviously not on a 5)

all a boost spike is, is when the actuator opens it opens a little too far to begine with then settles to what its set at.
also what gear are you testing the car in?
my car only makes stable full boost in 4/5th gear, its the only time the turbo/engine have enough load to make full boost.

[stu21t]

i use fuel hose for all my vacuum/boost pipes
its a much thicker rubber with a weave running through it and braid over the top.
if you use silicone pipes they can expand and loose the pressure/give a false reading.

[Scoff]

Stu, its not normal to spike 4-5 psi at only 16psi of boost, that is a problem.

Boost spiking (if not a leak, etc) is not the actuator opening too far but rarter it not opening far enough (read above, delayed signal from long/thin in-car pipe work).

[stu21t]

lol i spose im thining mine spikes more but then im running 2bar so more than double what his is.
tend to forget the details like that. lol
and doh, yep actuator holding back not too far.

[Scoff]

Have you tried an external gate stu ? I run similar boost to you, the internal gate was getting sloppy at 26psi or more. External tial does not spike even 1psi !

[Slim]

Ive been in about 20 different 5's.... most wiv incar boost....

i know this is defo not normall... im not a novice..

for the incar boost... i have one bleed valve under the bonnet (which connects to carb base, actuator... and other is going to incar boost control) this is correct right?

can i take the one under the bonnet out? will it still work??

[Slim]

i mean will the incar boost still work.. by replacing the under bonnet bleed valve wiv a t-peice

[Scoff]

Slim m8, you're not listening

Use only the under-bonnet valve. Disconnect the in-car. Set the under-bonnet to your desired boost, with the middle port open to atmosphere. See how that goes.

[Slim]

Slim m8, you're not listening

Use only the under-bonnet valve. Disconnect the in-car. Set the under-bonnet to your desired boost, with the middle port open to atmosphere. See how that goes.

k.. il give that a try..... but i should be able to use incar boost if i wanted to...

[Scoff]

Yeah you should, but you have to atleast know which part of your system is causing the problem before you can rectify it.

[stu21t]

Have you tried an external gate stu ? I run similar boost to you, the internal gate was getting sloppy at 26psi or more. External tial does not spike even 1psi !

no m8, but i have decided ive come to the end of the road with the 5 now.
not spending any more money on it.
im going to tidy up and improve on what ive got but im not going to spend any more money changing parts on it.
time to start the next project now.

[Slim]

true.... il have a go in a couple of hours... n report back.... n il make sure preload is 4mm ...

[Jimmy_GTT]

Slim m8, you're not listening

Use only the under-bonnet valve. Disconnect the in-car. Set the under-bonnet to your desired boost, with the middle port open to atmosphere. See how that goes.

What I had in car adjustable had that little spring and ball in the T piece of the controller. So I really sugest to change it to a simple T and give it a try.

[Jimmy_GTT]

i mean will the incar boost still work.. by replacing the under bonnet bleed valve wiv a t-peice

For me it has worked fine.

[Slim]

For me it has worked fine.

hmmm can you just use a t-piece under bonnet instead of bleed valve..?? (wiv incar booost) is that wat u mean?

k.. i tried wiv just a bleed valve.... its better ..slightly. it now just spikes 3psi ish... still think it can be better.. (boosts to 17..then drops to 14)

[Brigsy]

Check your actuator bracket is securely fixed to the turbo & doesnt flex. I had a similar problem years ago & found the bolts were loose/missing.

[Slim]

Check your actuator bracket is securely fixed to the turbo & doesnt flex. I had a similar problem years ago & found the bolts were loose/missing.

thanks mate... thats checked and secure... very lol

[Slim]

ive tried all sorts of pipe configurations u wouldnt believe lol....

im js tryin to keep it as basic as possible at the moment... but ive just taken vaccuum pipe from carb base and put it in the carb top instead... n loop from carb top to carb base..

also... on the other side of the carb (driver side).. there is another similar pipe going from top.. to base... i can remove that right??

[Jimmy_GTT]

hmmm can you just use a t-piece under bonnet instead of bleed valve..?? (wiv incar booost) is that wat u mean?

k.. i tried wiv just a bleed valve.... its better ..slightly. it now just spikes 3psi ish... still think it can be better.. (boosts to 17..then drops to 14)

Yes. It has worked fine.
Because for the bleed valve I had it was documented that it can cause such problem.
It was some cheap stuff from ebay.
Now I only have a single T instead of it.
The bleed valve should have a one way valve solution not to suck air from the open tube.

[Jimmy_GTT]

ive tried all sorts of pipe configurations u wouldnt believe lol....

im js tryin to keep it as basic as possible at the moment... but ive just taken vaccuum pipe from carb base and put it in the carb top instead... n loop from carb top to carb base..

also... on the other side of the carb (driver side).. there is another similar pipe going from top.. to base... i can remove that right??

Loop from carb top to carb base???
That's sounds crazy. Under pressure you are leaning the mixture!!!

Just have the cup mod and keep all the pipes in their std. place!

And maybe drop some pics from your engine bay.

[Slim]

Loop from carb top to carb base???
That's sounds crazy. Under pressure you are leaning the mixture!!!

Just have the cup mod and keep all the pipes in their std. place!

And maybe drop some pics from your engine bay.

hmm not sure u know wat i mean... look at the pic of my engine bay (thats a bit old tho things hav changed)

basically... on the carb top.. (the red pipe going into the carb top). .... instead.. im gna try puting one to the actuator... and the other where the actuator goes to know (carb base???) get me..?

[Slim]

and can you see next to my 2 yellow water hoses.... the carb top has one port blocked off... and the other has black pipes coming off.. one of those black pipes normall goes back to the carb??? can i take that off???

[Jimmy_GTT]

hmm not sure u know wat i mean... look at the pic of my engine bay (thats a bit old tho things hav changed)

basically... on the carb top.. (the red pipe going into the carb top). .... instead.. im gna try puting one to the actuator... and the other where the actuator goes to know (carb base???) get me..?

That is what I'm talking about. You are planning to connect the carb top and the carb base with a pipe. And with that I think you will lean out the mixture.
In the other hand if you are connecting the actuator to the carb top you will get less pressure.

But I'm pretty sure that the your T piece (bleed valve) has a one way valve in it.
Try to replace it with a normal T.