Not getting as much boost as I was...??

[Wally Dog]

Hi peeps, I'm a bit confused. I'll try and be as short as I can whilst including as much info as possible.

Until Tuesday, when I put my foot on the gas, standard boost guage needle would go straight up to two thirds up the white band, pulling like a train in third gear.

On Sunday, I was advised to change the vac hoses as mine were original and looking very fragile. Changed the top one on Monday, the one from the top of the 3 on the BCS to the actuator. Didn't instantly notice any change but didn't thrash it home, so wouldn't have noticed anyway.

Tuesday evening, I noticed that the boost was well off, not even getting quarter of the way up the white band on the guage (???) so I called Steve (thanks Steve) and got some hose yesterday to do all three hoses to the BCS. He also advised that it could be a problem with a leak in the hose that feeds the throttle body, which has an arm off it to the Idle control valve, so got those two off my scrapper last night.

Today, I cleaned out the idle control doodah as advised with carb cleaner (worked a treat and understand what was said about a rattle can sound), changed that, associated rubber pipes and changed all 3 vac hoses.

Now, when accellerating from 30mph in 2nd gear, the boost jumps to one third up the white and slowly rises to just under half way up before gear changing is required. Also, the Idle control valve was being a bit funny to start, revs drop to 1300 and hang there for 5 seconds before dropping, but was improving after 15 miles of test drive - i presume the computer just getting used to it.

So - the big question for me is: was my car over-boosting before due to a leak on that top vac hose or such like or is my car now running down on power? I know it's lost some serious grunt but don't know the in's and out's of how turbo's work. It all seemed to change when I first did that one vac hose - is this coincidence or what? Could it have been the actuator?

Sorry for the essay and thanks for any opinion/advice in advance.

:wallbash:

[Dangerous Dave]

If the top and bottom pipes to the BCS get mixed up then that can cause a boost problem, I got them the wrong way round (dodgy volvo diagram) and it wouldn't boost right, so I swapped them over and happy days :)

http://i150.photobucket.com/albums/s101/bomb192uk/mbcinstallation.jpg

[Wally Dog]

If the top and bottom pipes to the BCS get mixed up then that can cause a boost problem, I got them the wrong way round (dodgy volvo diagram) and it wouldn't boost right, so I swapped them over and happy days :)

http://i150.photobucket.com/albums/s101/bomb192uk/mbcinstallation.jpg

Nice diagram, useful stuff. I got mu old BCS from the car to check and can confirm that this is how it is routed - the BCS is actually mounted in my car the other way up from the diagram, as per the yellow, blue and red dots on the BCS - red dot is the same as the green hose on the diagram but the other two are same colour. I was very careful to change only one hose at a time (same as plug leads!) so as not to confuse where they went.

[Dangerous Dave]

Yeah, this diagram is the dodgy volvo one which has the top and bottom hose the wrong way.

Sounds like it could be something else then. Have you tried another bcs?

[glock19]

Your original hose to the actuator could be leaking and thus the force to push the wastegate was reduced, giving you more boost. Sort of like an MBC. When you renewed the hose, every bit of pressure from the BCS went directly to open your wastegate.

[Wally Dog]

Your original hose to the actuator could be leaking and thus the force to push the wastegate was reduced, giving you more boost. Sort of like an MBC. When you renewed the hose, every bit of pressure from the BCS went directly to open your wastegate.

Aah, brilliant - so that pipe does control something in the actuator then. So if I were going to fit an MBC, it would be in line in this pipe?

[Wally Dog]

Yeah, this diagram is the dodgy volvo one which has the top and bottom hose the wrong way.

Sounds like it could be something else then. Have you tried another bcs?

I swapped the BCS over for the one off my scrapper for the moment - my car has done 231000 miles and the scrapper only 148000, so i was working on the principle that the lower mileage item should be better for the mo, keep an eye out for a cheap new one!!!

[glock19]

Aah, brilliant - so that pipe does control something in the actuator then. So if I were going to fit an MBC, it would be in line in this pipe?

If you are going the MBC route, you can bypass the BCS as the BCS would be redundant. Put the MBC in between the compressor nipple-through the MBC-to the wastegate actuator diapharm.

[M-R-P]

Just to add some more to this,
Twas I that advised the vac hose change as all the hoses around the BCS had turned to putty and I very much doubt they were holding vacuum or pressure. Wally mate, it sounds like your car's been overboosting for some time and you've just got used to it like that.
Correct me if I'm wrong, but the boost gauge on the speedo is supposed to only make it about half way round on an unmapped car with no MBC?
At least you know what it'll go like with an MBC on there, and think of all the fuel you'll save lol.

[oblark]

Yeah a standard One will only go half way up into the white. I've got a remapped ecu you can try if you want :)

[Wally Dog]

Thanks all - I think Martin's right, it has been over-boosting for some time and is now back to standard. Oh, how I miss the boost... need more power!

Car is running very well now - no obvious problems with the over-running or the idle level. Seems to be quite happy.

Thanks Rob, I'll probably take you up on that one when I see you next - just to check, of course!!

[V70 Graham]

.....need more power!



Once you've had a taste it's hard not to want more, and more, and more lol