Boost Problems

[allstaruk]

Hi ya guys,

As some of you may have seen I have been having some problems with my car of late see this thread http://www.mazdarotaryclub.com/forums/showthread.php?t=31646 and a lot of you guys have been really helpfull. I have spent some time today in the engine bay and dealing with my suspension and have got some issues resolved I\'ve started to cure the boost leak.

I did have a leak now I\'ve fixed that things are better but not right the symptoms are now.

On WOT the first turbo makes 0.8, then at 4.5 the second turbo comes in and the boost fades away down to .2. So it would seem the problem lies witht the seconds turbo now, I\'m thinking maybe a fault with the charge relief system?

Anyone got any ideas.

Once again thanks to anyone who has contibuted.

Cheers

ALan

[nikp]

Possibly this:

Vacuum Chamber

This is a black plastic tank that is buried between the alternator and power steering pump. Kind of difficult to see, removing the Pressure Chamber helps to see it, has one hose connection, and should have a hose attached, (Engine View Picture). This hose comes from the rats nest of metal tubes, and there is a one-way check valve between the rats nest of tubes and the Intake, (the only check valve located between Throttle Body and the Firewall). This one-way check valve can start to leak after a while, causing loss of vacuum to various controls when under boost for a while. A way to troubleshoot this one-way valve leaking is to note a gradual loss of boost and then drop the throttle long enough for your boost gauge to indicate at least 20 inHg of vacuum then slam the throttle back down again. If boost is back up to what it should be then replace this one-way check valve. Basically what this does is "recharge" the vacuum chamber when you let off the gas, allowing actuators to operate properly while the vacuum is still present.

[allstaruk]

Quite possible its got dark ouside now so I\'ll look in the morning, I\'ve got some loverly new viton check valves sitting in the kitchen to go on, the thing is though the boost drops to below .5 bar which i thought meant there was a leak as the wastgate spring it set for .5 bar?

A

[gmogle]

Sounds like you are starting to make some progress mate, good luck, stick with it.

When you fix it and try the boost for the first time its incredible !!!!

[allstaruk]

It better be, i\'ve spent so much time working on this car its unbelivable, luckily i\'m going to buy another car next week so the rex will be my toy:D

[nikp]

Remove all electrical connections to the wastegate solenoid. Then re-check. If it won\'t hold 7psi (As you said, the wastegate spring), then you have a boost leak, exhaust leak, or a problem with the Wastegate or Turbo Pre-Control actuators

[allstaruk]

Cool, its getting dark and cold at the moment so I\'m just gonna put my tools away and give up for tonight, I have tomorrow off though so hopefully I can get this sorted.

Al

[allstaruk]

Right, I\'m conmencing work again, I\'ve disconected the wastgate solenoid and here are the results, now I feel I\'m getting somwhere.

1st turbo gives me 0.5bar as it should from the wastgate as soon as the sencond turbo comes online boost drops to 0.2/0.3 below what it shoud be, now with the wastgate turbo disconected I should be seeing 0.5 i belive as that is what the spring is set to. Now with the wasgate plugged in in supports 0.8bar on the 1st turbo so it would seem that this is working.

So if i\'ve got my logic correct then its either a boost leak, exhust leak or turbo pre control actuator, I can\'t see why I\'d have an exhust leak plus I\'m sure I\'d here it so its prob one of the other two.

Before I go outside and start fiddleing anyone shed any light on this or am a missing somthign obvious?

Alan

[nikp]

I don\'t think that logic is quite correct as the first turbo boost is not actively controlled by the wastegate.

[allstaruk]

I don\'t think that logic is quite correct as the first turbo boost is not actively controlled by the wastegate.

Er ok, this i am going to need enlightening, to me it seems that the problem occours when the 2nd turbo is involved am I thinking on the right lines here?

[nikp]

Yes, I agree that second turbo sounds problematic. The boost regulation of the first turbo is instead of using the wastegate, the exhaust gasses are directed to the second turbo. I think it\'s turbo pre-control.

[nikp]

Ok, you may have the turbo pre-control and wastegate solenoids muddled up. Read this:

If you are getting a solid 6 psi from 4,500 RPM up, Check the electrical connections to these two solenoids, as they can get mixed up while working on the engine. From the front of the car, the right hand solenoid and the electrical connector of the engine electrical harness have a painted white dot, these two go together. Note that over time these painted white dots tend to dissapear.

(0.5 bar is very close to 6psi - reading errors may make it look like 0.5bar rather than your actual 6psi. So, check these solenoids - try swapping the plugs over)

[allstaruk]

Ok, you may have the turbo pre-control and wastegate solenoids muddled up. Read this:



(0.5 bar is very close to 6psi - reading errors may make it look like 0.5bar rather than your actual 6psi. So, check these solenoids - try swapping the plugs over)

I\'m not thought I\'m getting a solid 0.5 below 4.5k above it i\'m gettting 0.2 bar mate.

[nikp]

Sorry - that doesn\'t make a lot of sense.

Are you saying you\'re not getting solid 0.5 below 4500rpm?

[allstaruk]

Sorry

I am getting a solid 0.5 up to 4500 rpm from 4500rpm to the readline I\'m getting 0.2bar.

Make more sense now mate.

Alan