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99 2.5RS Coupe 74f P1 Blue
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Discussion Starter #1
So last night i bought a 99 rs wrb, i began to look arount at it and at first i thought i was looking at a ej251 but then i realised that it has a maf sensor. however it seems to have the 251 intake manifold anyone know anything about this?
 

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99 22B replica
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Look on the drivers side strut tower. It should have an ID badge riveted onto it. look for a section that says "engine code" it should say EJ253, thats what 99RSs have. and yes they are MAF
 

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99 2.5RS Coupe 74f P1 Blue
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Discussion Starter #6
its was first in the 99 2.5rs then they went back to the ej251 starting my00 and reintroduced again in 05 i believe.
thats what i thought, do you guys know if i cant by chance swap a 251 ecu in to run the car purely map based since the 251 and 253 are so similar? i really hate maf sensors
 

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99RS 207 V9 AW
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251/253 is consider long block, very similar except 253 has a little more meat at 3/9 o'clock open deck. You're pretty much stuck with MAF unless you change ECU, I/M, and MAP. In fact, I have a 253 in my 2000 to replace a older 251/185K miles, just reuse my I/M then it's good to go.

Go find a 00/01 RS ECU, harness, and I/M, swap them in then you're good to go as MAP. It can use either 251 or 253 long block.
 

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99 2.5RS Coupe 74f P1 Blue
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Discussion Starter #8
Thanks that helps a ton and this May sound ignorant but what is I/M
 

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99 22B replica
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Intake Manifold.

there's no gain from swapping all that gear just cause you don't like MAF sensors. There's no extra power to be found. Easier to find a different car.
 

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99 2.5RS Coupe 74f P1 Blue
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Discussion Starter #10
its not about gain its simply something i hate , and i currently have a long runner 2.5i mani from another 253 sitting in my garage i imagine with some slight modification i could probably run that.
 

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99RS 207 V9 AW
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Just not worth the pain to convert from MAF to MAP, especially wiring harness/ECU/IM all must be MAP. MAF sensor locates on the air box tube, MAP sensor sits on top of I/M (has a hole) while MAF I/M has no holes.

MAF has its advantages, real time voltages from thermistor provides more accurate info to ECU for A/F compensation while MAP has a fixed value programmed in ECU but easy for tuner to hack to change A/F values.

Easier just buy a MAP 00/01 GC.
 

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It wouldn't be hard at all to convert to 00/01 MAP from '99. I'd have to dig into it deeper, but you would have to find a specific ecu to make it plug and play. Certain cars in that range used different 02 sensors, IAC and IAT were also different at times. It's just pointless, there's nothing wrong with MAF and you would gain nothing. I have NO clue where all the MAF hates comes from on RS25.
 

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99 2.5RS Coupe 74f P1 Blue
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Discussion Starter #14
I have no Issues running maf at all. I have had issue with cars in the past with intakes having dirty mafs and what not. The biggest fear i have is being a 15 year old car and parts out of production, say the maf gets damaged some how then I have to search craigslist, junk yards, and ebay hoping to simply find one that isnt damaged. The easier solution in that situation would be to map swap i was simply curious to what it would take. After more in depth research i have found that this particular generation of ej253 is identical to the ej251 except ecu, I/M, and engine loom. Thats the simplest solution to the situation unless i can find a properly working maf sensor.
 
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