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M35 Banjo Bolt Drilling For Highflows

scotty nm35
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scotty nm35 Grand Master

scotty nm35

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I have always suggested to drill out the banjo bolt in the block (that supplies the turbo with oil) to around 2.5mm once a highflow bush core turbo is installed. After the recent failure of a highflow due to oil starvation I did a flow test of the line at idle and found there wasn't enough oil flowing, even with the line/banjo disconnected. Suspecting a blockage in the block feed I checked another car and surprisingly found the same thing, the oil was only dribbling out. I checked on my spare engine and found in the sump another oil feed line, with two more 1mm restricted banjo bolts that feed oil to the external line. So it seems there are actually 3 x 1mm restricted banjo bolts as stock. Nissan definitely thought the oil pressure was way too high for the standard ball bearing turbo...

It also explains why the oil feed is so commonly blocked. On this car I have opened up the two sump banjo bolts to 2.5mm and approximately tripled the oil flow to the turbo, hopefully enough to supply the bush core with surplus. It was a bit wet today to take pictures but I will organise some next week, it's not a difficult job other than taking the pan off.

I am not suggesting everyone should rush out and drill these two extra banjo bolts out as I have, but Hypergear and I have agreed I should do this mod to all further turbo installs, to make sure not only the holes aren't blocked, and won't easily block again, but that there is sufficient oil flow to his turbos. I am also thinking about running braided lines and a filter inside the sump to replace the hard line, as it's easier to get to than the block mounted line, and would make sure no further blockages would occur. Not sure if it's warranted yet.

scotty nm35 Grand Master

scotty nm35

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Yep, Stao ships his turbo's out with a new banjo to suit the smaller thread in the CHRA. No idea why he doesn't simply tap it out, surely it's easier than cutting a banjo on the lathe... Anyway, what you did is fine Chris, just pointless if there are still two more restrictors. I would definitely suggest drilling them next service. ;)

scotty nm35 Grand Master

scotty nm35

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No worries guys.

I have had a few questions on this, one being can there be drawbacks. I personally don't think it will affect oil pressure to the engine, as only a small amount still flows to the turbos, even after drilling the banjos. I would definitely like to check the difference in oil pressure between my engine and this one but I have no gauge at the moment, and it is quite hard to read pressure without the adapter plate under the oil filter. I will check it at a later date.

Another question was, why aren't other turbo's blowing up. I believe there is JUST enough oil flow to keep the turbo's spinning, any partial blockage may be enough to do damage imo. Drilling the banjos out will give the turbo some leeway with oil requirements.

Here is the oil line we are discussing...

post-63525-0-89135900-1375444037_thumb.jpg

post-63525-0-28664500-1375444051_thumb.jpg

gleeson Community Regular

gleeson

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Posted (edited)

No worries guys.

I have had a few questions on this, one being can there be drawbacks. I personally don't think it will affect oil pressure to the engine, as only a small amount still flows to the turbos, even after drilling the banjos. I would definitely like to check the difference in oil pressure between my engine and this one but I have no gauge at the moment, and it is quite hard to read pressure without the adapter plate under the oil filter. I will check it at a later date.

Another question was, why aren't other turbo's blowing up. I believe there is JUST enough oil flow to keep the turbo's spinning, any partial blockage may be enough to do damage imo. Drilling the banjos out will give the turbo some leeway with oil requirements.

Here is the oil line we are discussing...

Edited by gleeson

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