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Old 01-20-2013, 04:03 PM   #1
turbo01gc8
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Default Map sensor ?'s

I have a 01 impreza with the 2.2L with an aftermarket Garrett t25 turbo. I have a stock map sensor and a black box to trick my ecu into not seeing boost. I think it's making my car run a little rough at times like during cruise and when I stomp on the gas it seems to studder then smooth out. I am currently using an Aem fic to tune with but it's hard to try and do myself. My question is should I get a new map sensor that reads boost in the factory location? If so what kind and has anyone ever used an fic before?
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Old 01-20-2013, 04:18 PM   #2
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Will a stock wrx map sensor bolt up to the theottle body and work since they are good for like about 20 psi? Don't plan on making more boost than that..,
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Old 01-23-2013, 03:26 PM   #3
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Do wrx's even have map sensors since they are MAF? How much boost are you currently running?

What about getting a GM 2 bar map sensor and tuning with that? While leaving the stock map sensor in place.
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Old 01-23-2013, 05:15 PM   #4
turbo01gc8
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After reading what I wrote I realized the wrx's do run a maf sensor. I'm only running like 6 psi at the moment until I get my 251 sohc built. If I get a gm 2 bar map sensor how do I go about hooking it up while leaving the stock one in place?
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Old 01-23-2013, 05:35 PM   #5
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Hmm yea i'm not sure. I was thinking you had a piggyback system (such as emanage ultimate) that would allow you to wire in the extra map sensor for tuning purposes.

What makes you think its the map sensor causing you problems? What is the black box you speak of? I'm guessing its a form of voltage clamp?

Honestly, you should post your questions over on rs25.com as they have a much larger community regarding turbo'd NA subarus.
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Old 01-23-2013, 05:47 PM   #6
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I do have a Aem fic and the map sensor is stock ro not read pressure I assume. I'm guessing the black box is some sort of clamp to trick the stock ecu to not see boost. I am assuming there is an issue with the map sensor bc at part throttle at cruise the AFR is all over the place so I figured I'd start with the map sensor. Also when I jamb on the throttle is takes a few seconds to smooth out. Almost like a hiccup
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Old 01-23-2013, 06:04 PM   #7
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Well, if anything it would be the black box causing you problems, not the map sensor. Atleast under boost. Because if it is a voltage clamp, then it clamps the voltage of the stock map sensor so that it doesn't see boost, like you said. If your ecu did see boost, then it would throw the car into limp mode...or atleast that is what I have read.

What are you using for fueling? larger injectors or rrfpr?
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Old 01-23-2013, 06:32 PM   #8
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Yeah I agree with you on the black box causing the issue bc I don't know exactly what it is. I was using a no name rrfpr for a while but wasn't sure if it was also causing problems so i removed it. So if I remove the clamp from the map sensor I should go with the gm 2 bar map sensor? It throws a CEL when I disconnect it. I think I read something about scaling the map sensor?

For now I have stock injectors with a walbro 255 in tank pump. I need to find some wrx 440's but I think the 251 I'm gonna install has the air injection issue with the injectors. It is out of an 02 legacy. I have to pull the injectors tomorrow to see for sure. If that's the case then I have to find a different intake manifold for the 251 to accept the 440's unless the intake on my 2.2 will fit....
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Old 01-23-2013, 08:39 PM   #9
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Wait a second, you removed the rrfpr? So basically you are boosting without increasing fuel? If you use stock injectors, you need the rrfpr to raise the fuel pressure relative to boost. with larger injectors you dont need an rrfpr but you need a way to control the injectors. I think you need to do ALOT of reading over on rs25.com

And no, a GM map sensor is for tuning purposes only. You still need the factory sensor hooked up and clamped.
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Old 01-23-2013, 08:58 PM   #10
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So if I get a rrfpr I should be able to control the injectors with the Aem fuel and ignition controller?
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Old 01-23-2013, 09:22 PM   #11
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I don't want to sound mean, but do you know what's needed for a turbo system?

With a turbo, you need a way to add more fuel. One way, and its not the recommended way, is with a rrfpr. This raises the fuel pressure and allows your stock injectors to dump more fuel than they would at stock fuel pressures. This should only be used for low boost applications as eventually you completely max out the injectors.

The other way is to buy bigger injectors. But you need a piggyback, standalone, etc. to be able to control the larger injectors and tune the car properly.

Both of these require a larger fuel pump to be keep up with the extra demand. Which you already have, which is good.

However, from what you have said, all you have right now is a larger fuel pump and nothing else for fueling. So I'm not surprised at all that you have problems.
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Old 01-23-2013, 09:41 PM   #12
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Ok I will try to find larger injectors and use my aem piggyback to see if I can work things out. For now ill hook the rrfpr back up to see where it gets me without messing with the map sensor. I understand fuel and timing need to be adjusted to compensate for boost especially on an na engine. Thank you for all your input I appreciate it.
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Old 01-23-2013, 09:50 PM   #13
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No problem. Definitely hook up the rrfpr until you get larger injectors.

And regarding the 440 injectors working with your ej251 manifold, it can be done. You can call Rallitek and ask for their o-ring kit. It is designed specifically for what you're trying to do. It is also what I'm gonna do soon, as I'm still piecing together my turbo kit.
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