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1999 Forester S Turbo 5MT
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Discussion Starter #1
I have a Harvey Smith EBC fitted but I left the electric cable for the OEM boost solenoid connected but the pipes are open at the other end. I am having issues with hesitancy under load at speed and one of the threads in the Europe forum suggests the solenoid could be gunked up. Does anyone have any info on this as to whether I should have disconnected the OEM BCS or should I leave it as is and clean it?
 

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Don, King of the parts diagram
MY11 WRX STi Sedan 6MT
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Registered
1999 Forester S Turbo 5MT
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1,960 Posts
Discussion Starter #3
I did read Mikes very comprehensive article, it was what sold the Harvey Smith for me but I was concerned that as the OEM BCS is still plugged into the ECU, it might be giving false/inaccurate info to the ECU. I have been having some growing boost/flat spot/heisitency issues and wondered if leaving the OEM BCS connected, and if the it had got gunked up too, might affect the way the engine is running. I have genuine Subaru MAF and TPS en-route, hoping they will help. Thanks Don.
 

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Don, King of the parts diagram
MY11 WRX STi Sedan 6MT
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5,868 Posts
If you have fitted/plumbed in the HDI 3 port solenoid in place of the OEM, then the OEM one is not doing anything. "It" receives its signal from the ECU not the other way around. All it is is a 2 way valve. If you disconnect it electrically the ECU will probably think there is a fault with it and throw a CEL.
 

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1999 Forester S Turbo 5MT
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Discussion Starter #5
That answers the question Don - the direction of the signal, that's what I needed to know. I thought maybe it was the other way and the BCS was telling the ECU "something is wrong". Thanks.
 

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99 UK S-turbo
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If I disconnect the BCS on my 99 it goes straight into limp home, msifires under any boost at all.

As Don says the ECU drives the BCS, it recieves no info back (other than that its connected as presumably it monitors the current draw).

Simon
 

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1999 Forester S Turbo 5MT
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Discussion Starter #7
Never mind the BCS, my new genuine Subaru MAF arrived and I fitted it this morning. I bought a pattern part about six weeks ago for £45 on fleabay and there was no difference between it and the old one. Lesson learned! With the new MAF and 200 miles up today, it's a different car, I can't believe (it's not butter) changing one sensor could rectify so much trouble. Jerkiness on the over run, especially around town, flat spots, hesitation, erratic/uneven idle and rough power delivery, all gone. I filled the tank this morning and at this time I reckon the needle at 200miles today is in the same position as about 160/170 normally - my usual average is 28mpg mixed driving. I get some of my Parts from these guys Japanese Import Car Parts. The MAF on this site was £89 and I have seen this particular model of Subaru MAF (00 on is different and more expensive) elsewhere for twice that. Most of the items they sell are Genuine Subaru and overall their prices and stock are pretty good I think. I also have a genuine TPS en route, lets see what that does. Thanks Don and Simon for the input.
 
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