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Rb25det excessive blow by from track use


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Hey guys,

 

Have recently had problems with excessive blow by at the track. I have an at performance catch can with 2.3l capacity and fill it up after 5 or so laps. Have been told this is normal for Rb's but seems pretty excessive. I have seen peoples setups to drain from the head back to the sump but a healthy motor shouldn't need that? Im only running 250hp with a standard high flowed turbo. Thinking i need a rebuild but want to here peoples thoughts.
Do freshly rebuilt rb25det's still push oil out at the track?

TIA

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Agree, not normal. I hardly get any after a whole day of thrashing (40+ laps)

The only time ive had a fair bit was when i had overfilled the sump too much, i now only run 300 ml extra oil above the h mark and only get a few drops worth by the end of a track day. No oil mods at all.

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7 minutes ago, admS15 said:

Agree, not normal. I hardly get any after a whole day of thrashing (40+ laps)

The only time ive had a fair bit was when i had overfilled the sump too much, i now only run 300 ml extra oil above the h mark and only get a few drops worth by the end of a track day. No oil mods at all.

built motor or unopened? what sort of breather setup are you running?

 

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built motor or unopened? what sort of breather setup are you running?

 

Unopened motor, no breather. Catch can is baffled and attached from passenger side rocker cover and then plumbed back in to intake. Car makes over 300rwkw on e85 and high flow turbo and has done over 20 track days like this without issue.

 

Edit, factory pcv setup is also still present and functional.

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35 minutes ago, admS15 said:

Unopened motor, no breather. Catch can is baffled and attached from passenger side rocker cover and then plumbed back in to intake. Car makes over 300rwkw on e85 and high flow turbo and has done over 20 track days like this without issue.

 

Edit, factory pcv setup is also still present and functional.

Nice mate, sounds like a strong motor. Do you think the pcv helps with blow by? Any pics of your catch can setup?

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No pics of catch can atm. Its just a home made job using steel wool and some wire mesh plate as baffles. Ill try to get a pic for you tomorrow.

The pcv does help when used in a factory or plumbed back system. I believe you are meant to remove the pcv when venting to atmosphere.

Have you done some basic checks on your engine, like a compression test just to get some idea of condition. That should show if there is something drastically wrong.

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Do a compression test to see if you have the dreaded broken ring lands (or just some broken rings. If compressions are fine have a read of this thread (start about 2/3 way through):

 

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10 minutes ago, KiwiRS4T said:

Do a compression test to see if you have the dreaded broken ring lands 

This was the issue when mine was filling the catch can after a few hot laps.

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31 minutes ago, KiwiRS4T said:

Do a compression test to see if you have the dreaded broken ring lands (or just some broken rings. If compressions are fine have a read of this thread (start about 2/3 way through):

 

Thanks man, yeah some good ideas there, I'm definately up for a rebuild, will be doing these before re assembling.

 

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