phill 147

fitted a boost gauge to day when boosting in third goes past 1bar poss 1.2bar and hesitates at that boost what would cause overboost is there a restrictor in pipes on uk model

STI_Baly

iTrader: (23)

When you say it hesitates? what exactly do you mean? i mean is the car juddering, mis-firing, seems like it hit a brick wall then comes back on boost??

Have you checked all your vacum hoses i.e. everything involving turbo, wastegate, and boost solenoid for blockages?

Does the car actually feel different or is it now only evident because you fitted the gauge?

B

STI_Baly

iTrader: (23)

Oh and i forgot to say yes there will be a restrictor pill if its a standard turbo with standard boost solenoid setup. It should be a 2 port boost solenoid on your motor and the restrictor pill will be as in this pic>>



MY00 (Euro) ... 1.2mm restrictor pill
MY00 (JDM) ... 0.9mm restrictor pill

phill 147

car seems to hold back and feels like a big pause then boosts again does'nt slam you into windscreen though seems worse on full throttle

scooby1doo1

iTrader: (7)

Have you done oat els or just fit the boost gauge, is this all the time.

phill 147

seems to happen all the time thats why i decided to fit boost gauge

Scooby715

Had that on my 00 an all. My mate works at subaru and said it was the factory boost controller backing off the boost and it always seems to happen when you go over 1 bar. What i did was i bought a manual boost controller and piped it up to replace the standard one then you can adjust the boost yourself to where you want it. You have to leave the factory one plugged in otherwise it throws up an engine management light. Mine boosts fine now and holds at 1 bar perfectly, i'd recommend the turbosmart MBC, expensive but worth it as the adjustment is really fine and precise.
Hope this gets you running again!!

JDM_Stig

iTrader: (3)

Harvey sells a nice Boost controller for the classics

Splitpin

Boost cut on your ECU is 1.22 bar. If you exceed this the car will hesitate very sharply and roughly.

If it isn't that sharp, it's most likely, as Scooby715 says, a milder overshoot which the ECU is trying to cure by reducing the solenoid duty cycle to bring it back under control. The further over it goes, the bigger the drop in DC.

If as a result of that first correction the boost then goes significantly below the target, the ECU will add extra DC to bring it back up, so you get into a situation where it constantly pogoes up and down.

The correct fix for this, without remapping or external boost controllers, or anything much else, is firstly to make sure you've got the right size restrictor fitted, that it isn't gummed full of oil, and, if necessary, to drill it out a little bigger.

Incidentally, do you have a decat or any other significant mods Phill?

phill 147

the only mods i have is a 6x4 oval rear box and a forge dump valve fitted
also lamdba reading is slightly high should run at 1.000 but mine stays around 1.020

phill 147

is it best to get electric or dawes type of boost controller

Splitpin

Neither, at the moment at least. If you are getting overboost, it's more sensible to find the cause and fix it before mucking around with aftermarket bits and bobs. Otherwise you run the risk of compounding one problem with another.

Have you checked to see whether you have the standard (green label) ECU or the PPP (pink) one btw?

When you say the lambda is reading "a bit high", where are you getting this reading from?

phill 147

lambda is from a proper emissions machine from a garage checked exhaust out can't hear or find any leaks have replaced lambda sensor what would cause high boost

phill 147

have still got restictor in pipe looks all good dump valve works ok so wastegate should be opening what would happen if boost solenoid is not working
also what are the other 2 devices that have vacuum pipes on them right next to solenoid i think one is a map sensor any other thing that could cause overboosting

Splitpin

Not sure what that means. Just because the dumpvalve opens, that doesn't directly imply anything about the wastegate.

If it was stuck in its de-energised position, you would get actuator pressure - so around half a bar boost (and probably a CEL). If it is sticking "shut" then you could get subtle overboost. Have you tried cleaning the boost control pipework - inc restrictor and solenoid - through with brake cleaner with the test mode connectors on?

They shouldn't directly cause overboost no. The one at the top is, as you suspect, the pressure sensor. The brown thing underneath is the pressure sources change solenoid. As the name suggests it switches the pressure source feeding the sensor from the atmosphere under the bonnet (via the little black filter) to the manifold.

The ECU calculates boost pressure by subtracting the atmospheric from the MAP. The only circumstance in which they can directly cause boost control problems is if one or the other is either buggered, of if the pipes feeding them are oiled up.

phill 147

if the dump valve releases pressure to atmosphere would'nt that mean the wastegate would open the flap on turbo

scoobynutta555

I'm glad there seem to be some sensible solutions to the above problem as I had the exact same thing after my old MY00 was rebuilt by API, they had outsourced the remap to the guy who runs Zen now. Basically after spending several thousand on this work (320 bhp conversion) I was told 'the car is several years old so it's probably electrical. I then had to pay for a bleed valve and turn down boost to cure this problem.

APIDavid

iTrader: (4)

The boost almost certainly wasn't turned down, it would probably have been set at target boost - let's say 1.35 bar . What it does is act as a safety valve and bleeds off all boost registered above 1.35 bar. A simple and effective cure [ and cheap ] for overboost.

Sometimes it can be very time consuming to go looking for an obscure reason why it overboosts and given that each hour that is worked on a car attracts a labour cost, it is often a way out for the customer that doesn't cost heaps.

However, using a bleed valve as your sole means of boost control is a VERY BAD IDEA and I do not advise that at all.

David APi

Splitpin

No, not sure where you got that idea. The dumpvalve and wastegate are completely independent of each other, and controlled by different sources.

Wastegate is opened by positive boost pressure from the compressor bleed nipple being directed (or not) to the actuator, while the dumpvalve is opened by vacuum in the inlet manifold (or, more accurately, a pressure differential between the two sides of the throttle plate).

scoobynutta555

you advised me to do this and you fitted it.

phill 147

ok have sprayed solenoid with brake cleaner and checked all pipes checked solenoid clicks when given 12v ,checked actuator for turbo by applying pressure and it opens and holds there ok
how do i check power to solenoid when pluged in or just check for 12v at plug with ignition on?
car is still hitting 1bar before i release and really hesitates also in fourth holding it about .7-.8bar it starts to hunt but that could be ecu adjusting itself
also how would i find out if im getting pressure at actuator ?
is ecu in passanger footwell as i will check number
anyother checks i can do before i take it toa specialist
anyone know a good place to go around hemel hempstead ,aylesbury,wycombe areas

cushti

iTrader: (7)

Check all the exhaust gaskets are ok from heads to turbo. I had a hesitation for several seconds on boost at around 4krpm (ok before & ok after). Checked all usual suspects such as hose leaks, swapping over sensors, swapped ecus e.t.c. & in the end the answer was just a small leak from one of the exhaust header gaskets.

I couldn't hear anything, just lucky & felt it as I ran my hands around testing the up-pipe & headers for any cracks.

ByByR1

My 2000 turbo wagon hits about 3500rpm then throughs me itno the windscreen like it blown up then just comes back on song again in 4th and 5th gear. i had this before on an older scooby and the dealer cleaned out what I think was an over boost valve near the laft hand side strut top. Can anyone point me in the right direction or am I not even close.

TonyBurns

iTrader: (3)

You mean the boost solenoid?

Tony

a5h

iTrader: (3)

I had the same problem with my uk 2000 but fiestaboy gave me a hint to check the boost solenoid by putting the car in test mode to see if it clicks as this tests all the electrics.
Also by cleaning it and the pipes through with brake cleaner while the car is in test mode to clean it out.

ByByR1

Thanks tony, how do I engage the test mode, I have done it before but forgotten as it was so long ago. Thanks

Splitpin

Connect the green plugs under the dash (and only the green ones) and turn the ignition on.

ByByR1

I will wait for day light as I will prob mix them up. Thanks

a5h

iTrader: (3)

I still had the problem on mine after clearing it through with brake cleaner. By some crazy stroke of luck or bad fortune when i was trying to clean it through with brake cleaner the pipe going to the actuator snapped so i had to replace it and has not over boosted since.
Could just be worth clearing the pipes through.

Good luck