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RB25 NEO not holding compression

The_RB25_Noob
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The_RB25_Noob Newbie

The_RB25_Noob

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Posted

Hi everyone, just bought a r33 gtst with an rb25 NEO swap off marketplace with about 60k miles. My main issue is that the all cylinders are 5-10psi below spec. Highest is 150, lowest is 138.

Didn't get any service records from the previous owner. Any ideas as to what might be the issue?

The car idles and runs pretty rough and I've never pushed it past 4 psi, if that helps.

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https://www.sau.com.au/forums/topic/483403-rb25-neo-not-holding-compression/
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Duncan Grand Master

Duncan

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Posted

Most likely the only issue it has is how the test was done, those results are fine. You need plugs out, wide open throttle and well charged battery probably with a booster pack when you do every cylinder. Even then 9.2% variance is not an issue

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GTSBoy Grand Master

GTSBoy

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Posted

Yes. Agreed. Apart from one good data point I have (my Neo, tests on a trustworthy comp tester at ~170 psi on all 6) which shows that a healthy Neo can generate substantial cold comp pressure, there's nothing wrong with 140-150 psi.

As Duncan said, it could be a little worn, could be technique, could be a slightly low reading gauge, etc etc. 9% variation does suggest that some of it is wear, because clearly some have worn more than others.

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Piggaz Grand Master

Piggaz

Posted
Posted
On 4/3/2022 at 12:49 PM, Dose Pipe Sutututu said:

Sounds fine to me, just send it with more boost to make up for the slightly below spec compression

What if the turbo is tapped out and it has nothing left to give? No point running a snail at half it’s capacity. It’s too big then. 🤷‍♂️

GTSBoy Grand Master

GTSBoy

Posted
Posted
On 3/4/2022 at 3:32 PM, Piggaz said:

What if the turbo is tapped out and it has nothing left to give? No point running a snail at half it’s capacity. It’s too big then. 🤷‍♂️

I think Johnny's next reply would be something about a 3.2 upgrade and Samsonas.

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Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

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Posted
On 04/03/2022 at 7:09 PM, GTSBoy said:

I think Johnny's next reply would be something about a 3.2 upgrade and Samsonas.

I feel this car needs a BMW GS7D36SG DCT and yes a 3.2L.

Should go well with a street Garrett G40-900 in full twin scroll form.

 

 

  • Haha 1

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