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02 wrx motor in a 73 porsche boost issue

Boost Control

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Hello all,

the issue i am having is that when you go into boost it will go to 14psi and then drop down to about 5psi and then back up to 14 and then down to 10 then back to 14 and then 12 and just keeps doing this. i have messed with the cycle duty and has not helped. i am at a loss on what to change next.

it is a stock ecu, cold air intake right off turbo inlet pipe. inter cooler and piping since cant run stock one. stock fuel injectors aem 380lph fuel pump. 3in exhaust with high flow cat and muffler. total length of pipe is 4 ft. everything else is stock.

Are you sure your boost control plumbing is correct? What tools do you have to verify correct sensor readings are seen by the ECU? Have you checked for boost leaks?

i have looked over many pics of the way the vacuum lines should be ran on a stock wrx. i have read the reading from the ecu and have a boost gauge on the dash to see what it is reading. i have not seen any boost leaks i have gone over all the connectors and they are tight. i have removed the tube that has the pill in it then replaced it with just a piece of tube and it pulls to 7 psi and holds strong. no drop in pressure or surging that it is doing now.

It would seem to be a delay in feedback between the actual boost pressure and the controller, causing the boost to keep overshooting the base setting. If so, could be a couple of things.

A sticking valve assembly that needs a little more force to move, instead of closely following the pressure.

A restriction in the line(s) that's delaying the manifold pressure variations from reaching the controller* and/or using very flexible hose that's swelling and dampening the response(s).

*From what you said about the "pill", I'd say that's the issue and if you are running a restriction ( why? I'm not a "turbo'" guy, but I don't recall this being used) check it isn't partially blocked.

the pill is required in the wrx. it allows more psi to be pulled out of the turbo otherwise you wont go over 7psi. i am running silicone lines and i could see it expanding a little under boost. i will see if i can find another boost controller and try that to see if it makes a difference.

OK, been doing more checking (it's a common, well known problem) and the "pill" does what I suspected, it's to delay the controller response, probably to give an initial "overboost".

There are numerous different orifice sizes tailored to specific vehicles*, which strongly suggests the sizing is critical and any changes from the OEM configuration may require a different size - removing the exhaust would fall into this, as would the silicone hoses which would further delay responses.

My personal preference would be to remove it but, if you want to keep it, I would suggest swapping out all the pressure regulation lines for a stiffer neoprene type and seeing what difference that makes, then picking up a selection of pills and trying them to see what orifice give the best results.

*One of the better threads on the problem, with the different pill sizes, models they're used on, and part numbers - http://www.subyclub.com/topic/9097-restrictor-pills-read-this/


after reading that article i would agree that the pill matters. when i ordered mine i made sure to get the 02 wrx one. but im not sure that if changing the exhaust would make u have to change the pill to different sizes. i asked a buddy who is going to let me try another EBCS from a 04 wrx. same base car, and see if that makes a change. if it doesn't help i might look into doing a after market boost controller and see if that changes anything.

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