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Old 03-14-2011, 11:03 AM   #1
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Default Open vac pipe - solenoid

First off, alert..

I have been doing a bit of a spring clean in the engine bay when I came across this open vac pipe, see the picture.

IMG_8697copy.jpg

Iíve read on here that this is "some sort of selonoid that's most likely controlled by the ECU"

On idle a vacuum is drawn through the open upright black pipe on the solenoid, and being un-filtered that cant be good. If I cover it up with my finger the engine will idle rough and lumpyÖ And in my mind, that vacuum must turn into a boost leak when err.. in boost, right?

So I tried hooking those hoses up to delete the solenoid, and again the idle is rough, and the throttle response is delayed. But it boost stronger (with no knock detected)

vachoseplumbing.jpg

So Iím thinking the mapping must have been done around this vac leak, and adjusted to suit. And to get the throttle response back I need to adjust the map, or something with the ECU. If thatís right, what do I adjust?

So before I head off into re-mapping (another land Iím unfamiliar with) I ask the all knowing miataturbo groupies if Iím on the right track

Car spec, UK í90 1.8, FM Spec internals, FM2 turbo, Link ECU and a dyno sheet with 280hp on it. Bought as is.
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Old 03-14-2011, 11:11 AM   #2
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its a boost solenoid; it's not hooked up so it's closed, no biggie. I'd personally would not want it on any line that the MAP shares, once hooked up. It bleeds off boost before the wastegate so it increases boost greater, so I'd connect the MAP sensor to the FPR line, the the solenoid to it's own line on the IM...it would go back to the wastegate.

Right now, I'd just remove the Tee behind it, and plug the MAP directly into the IM.
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Old 03-14-2011, 11:17 AM   #3
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It is hooked up, not in the photo mind... One detail I forgot to add (ooops!) It is connected to the wiring harness as per OEM at the moment. What shall I do with it?
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Old 03-14-2011, 11:18 AM   #4
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hows it connected as per OEM if it's not an oem part?
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Old 03-14-2011, 11:26 AM   #5
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Isnt it? I dont know, it looked to be with the wiring harness and connector looking soo much like OEM. Granted I looked over another 1.8 car at the weekend and his didnt have this solenoid, but loads of other things were different too..

So is IM to solenoid, then an open end correct? Just without the connection to MAP inline?
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Old 03-14-2011, 11:31 AM   #6
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Actually, there are three ports. The third port has a filter at the end, covered in that black cylinder.

It should go IM, solenoid, wastegate. Then your LINK would be controlling it, once wired up. The idea is that when the solenoid dumps out boost from the bleeder port, the wastegate stays closed, thus raising boost.
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Old 03-14-2011, 11:59 AM   #7
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I have this Boost Control Solenoid as per the pic below too (image shamelessly stolen from the Link ECU Instalation manual)

[IMG][/IMG]

Does that change anything mentioned in your post above?

And with that installed, I wont have a port on the wastegate for the solenoid pictured in the first post will I? Cant check at the min through being at work, and the car isnt..
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Old 03-14-2011, 12:04 PM   #8
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If you have that, then remove the one pictured.
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Old 03-14-2011, 12:08 PM   #9
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Actually that looks a lot like the FPR solenoid we use on the FWD BP's in OEM form.
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Old 03-14-2011, 12:10 PM   #10
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So remove the solenoid pictured in the first post, and plumb up as per the 'should be' diagram?

Which leads me to the idle being lumpy and a delayed throttle response, how do I overcome that?
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Old 03-14-2011, 12:13 PM   #11
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I mean I don't see it doing anything. As is, with the port opened like that, it should be as if it's not there. Unless whatever you are plugging it in to it activating it, then you'll be creating a vacuum leak.

IMHO, removing it should have zero effect on idle or throttle quality.
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Old 03-14-2011, 12:39 PM   #12
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PDG, is your car a UK model?

Cos my dads car has one of those fitted and his is a UK car, it also looks 'OEM' with the connector and wiring etc. I really don't think it's an EBC as Brain is suggesting - though I don't actually know what it is for...
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Old 03-14-2011, 12:41 PM   #13
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now that I think of it, I remember seeing one like that on the FPR vacuum line on a +01 head.
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Old 03-14-2011, 01:18 PM   #14
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Its a UK wiring loom yes

From another source:
"the valve in question with a vac line to atmosphere is the Pressure Regulator Control (PRC) valve.

"This device monitors manifold vacuum and controls the operation of the pressure regulator so that fuel pressure is kept within desireable confines for the operation conditions prevailing. To prevent the percolation of fuel when a hot engine is restarted in a hot climate and allowed to idle, the PCM operates the PRC solinoid valve for 150 seconds. during this time, manifold vacuum (applied via the pressure regulator) is shut off, allowing fuel pressure to rise to 41psi"

Perhaps the vac line should go IM to solenoid to FPR, with a T off for the MAP? Pretty sure I have tried this and got the same idle/throttle issue
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