Interesting. Im only going off my car, which is a MY05 Forester XT. It maxes out, according to the data logs, at around 18psi.

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Doing it for all the wagons out there

Bram - It's probably your stock boost solenoid that can't read any higher... replace with grimmspeed 3port and the likes...should have been one of the initial mods on the car along with a tune/fuel pump.

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06 STi: 337hp @23psi on E85...
06 STi: 309hp @22psi on 98ron...

Done that about 4 years ago.

Car is tuned to run 22-23 psi. And its been doing that for a while now.

The ECU doesnt really need to see higher MAP. The cars are MAF based. y
You only realy want it for finer closed loop boost control, or a speed density hack.

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Doing it for all the wagons out there

The OEM Subaru MAP sensor is good for 2-3bar depending on model/year. By the way who tuned your car?

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06 STi: 337hp @23psi on E85...
06 STi: 309hp @22psi on 98ron...

Well. Maybe the MAP sensor may be able to handle higher. But the ECU will only see up to 18psi on mine. When i plug the readers/loggers in to the OBD port, it never shows more than around 18psi.

Also. A 2bar MAP sensor can only actualy see 1bar of positive pressure. Remember, atmospheric pressure is already at 1bar. ECUs talk in absolute. We commonly talk relative. When we say 1 bar of boost, we are tecnically saying 2 bar absolute. (Give or take for minor variations in atmospheric pressure)

ASG / Sean tuned the engine.

Anyways. This is getting well away from the OPs original problem.

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Doing it for all the wagons out there

Boost solenoids don't read anything they are a solenoid, not a pressure sensor.

They're simply an electro magnet, a return spring & a steel rod with a rubber valve seat on one end:



Subaru factory MAP sensors have varied a lot over the years.

The reason you want one that reads above the boost you currently run is for safety. The factory ecu is blind to boost it cannot see - be it a deliberate boost increase or a system failure.

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[CENTER][SIGPIC][/SIGPIC][/CENTER]
[CENTER][COLOR=#ff0000]Built Ej207: Semi-closed RA Cases - Wiseco Forgies - Manley rods - BC 272 cams - GDA Heads - billet f/whl - Vi-pec - WbO2 - 800cc Yellow tops - TD05-20G - 409Hp ath @ 1.75bar on E85[/COLOR][/CENTER]

So what does the ecu do with boost levels when they go above levels it can see?

Usually it will either throw the check engine light on & cut the fuel (boost cut) or go into limp mode on the later cars & run waste gate pressure (5-7psi).

With some open source tunes (Rom's) there's code that disables the factory over boost safety features - not great for reliability in the long run. Most tuners cap the upper boost limit well below the MAP sensor's limit or they change to a GM 3bar sensor.

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[CENTER][SIGPIC][/SIGPIC][/CENTER]
[CENTER][COLOR=#ff0000]Built Ej207: Semi-closed RA Cases - Wiseco Forgies - Manley rods - BC 272 cams - GDA Heads - billet f/whl - Vi-pec - WbO2 - 800cc Yellow tops - TD05-20G - 409Hp ath @ 1.75bar on E85[/COLOR][/CENTER]

Sean told me the same thing about my defi boost gauge. Mine reads 1.5 but car is tuned to 1.4bar which is shown on my dyno graph. If you doubt him they can supply a dyno plot showing manifold pressure.

I have been meaning to try different size t-pieces etc to see if its a line restriction issue but havn't got around to it yet.

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The one perkent...

Now, Im going to struggle to remember if it was here, or wrx.com.au or Rexnet (RIP), but someone had 2 gauges installed side by side on the same car - a DEFI and a cheap shit SAAS, and took pictures to compare the differences.

You'll never guess which one was more accurate - the cheap shit SAAS. The DEFI was consistently out.