Banjo Bolt - ebay (Mamba) vs...

Whilst doing research on the downpipe I'm going to install (catless) I ran across a video where the person mentioned that a catless downpipe requires the installation of a replacement turbo banjo bolt. Whether it's required or not I guess is up for debate. However, to prevent smoking and such things I popped on one. It was a bit of a knee-jerk decision as I just followed the link to the one he bought. It was off ebay (Mamba brand, K028-0025) which I didn't really think about at the time, but now I'm wondering if I should invest in a different one. I'm not certain what the perfect restriction is for a catless downpipe for that bolt but the hole in the bottom of this one is so much smaller than, say, Damond's (and JBR for that matter).

The package says "M12x1.5 with 1.8mm restrictor for Mazda 2.3T K04 turbo". I can't find a comparison on either JBR or Damond.

Bottom line: I'm not a bit weary of an ebay purchase but can't tell if I'm sweatin it for nothing. Appreciate any thoughts.

 

Damond of JBR. Why? They make stuff for obsolete dead platforms like us Mazdaspeeds. Sad but true. This was actually the bnoon bolt back in the day.

 

bnoon, as in Brad Noon? is that 'bnoon' bolt sub-par?

 

That would depend on what kind of turbo you have. A turbo with a journal bearing needs tons of oil flow. A ball bearing turbo needs less.


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Stock turbo here


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Bnoon is legit original guy

 

So this is the exact same bnoon guy? Read about him on the other forum, I will he ordering one now. Just installed my downpipe today.

 

Which one u ordering?


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Whoops, I thought the one you bought was the original bnoon guy. Looks like I got confused.

There is one bolt on Ebay with a few reviews, one which has a lot of info. May go with that seller...

 

I did. I actually also bought the Damond one. I got nervous lol. So now I have 2. Oops


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I couldn’t really tell if the eBay one was ‘good’ or not. That’s why I got the Damond one. Prolly fine but as I said....got nervous.


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Damond parts are always a good decision.

 

You chose wisely. eBay historically has had incorrect holes drilled in it. Too big, too small.

 

Unless your turbo is smoking, you don’t need to do anything. Turbo oil flow issues are only caused by one one of two things:

1. Too much oil pressure. This is easily checked with an in-line oil pressure gauge. If you’re seeing over 70psi, you need a restrictor. This is unlikely, as even with a fully built motor that red lines around 8k RPM my oil pressure only hovers around 60-70 psi.

2. Positive crankcase pressure pushing the oil back up the oil return line. This is a heavily documented issue on Mazdaspeeds and, in my opinion, probably the cause of 95% of all smoky turbo issues on our platform. Invest in a better PCV solution if you plan on modifying at all. Starving a turbo of oil with a oil restrictor bolt while you have a crankcase pressure issue will only accelerate premature turbo failure.

I know this after MUCH research because I used a restrictor bolt with a brand new BNR S4 (journal bearing) and had to have my turbo serviced after only 4,000 miles. I solved the PCV issues, switched back to the stock bolt, and have not had a single issue since.


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I don’t have any smoking issues that I’m aware of. I read and noticed a trend of needing to add this bolt when switching to a catless dp, which I will be doing.

What’s a better pcv valve solution? I’ve seen Damond’s plate but that just appears to let you have a multi-occ setup which I doubt I’ll do. Also helps make the valve easier to change if needed I guess.

I did think about just replacing the pcv while I have the mani off as a just-in-case.


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Replacing PCV valves is never easy, even with a Damond plate. It’s held in by a retainer clip, so you still need to take off the manifold to get access to it unless you have extremely tiny hands and surgeon like precision. It’s a $14 (last I checked) plastic part, so I would just replace it anytime you’re in there just because it’s a pain in the ass to get to otherwise.

You don’t necessarily need a catch can, but it’s a good idea. There are several options for ventilation. The more heavily modded you are and the more boost you run, the bigger the pressure problems get.

Ideally, a crank case would always be under negative pressure. This is why dry sump systems use pumps to suck oil (and excess air) out of the block. Air will go the path of least resistance if there isn’t suction present telling it which way to go, which is up your oil return line at times. The PCV system is designed to create that suction via your intake manifold, but that only works while it’s under vacuum, which is most of the time if you’re not a race car driving living under boost 90% of the time. Catch can systems are designed to also create suction under boost and catch the oil particles in the process so they do not go back into your intake manifold. If you’re a race car driver, like most of us, a catch can setup that is well designed sometimes doesn’t even give enough suction. It can be tricky. That’s why professionally built race cars use dry sumps in nearly all cases.

But anyway, the point of all that is don’t do things you don’t need to do. If you’re driving in boost more often than not, you probably should invest in catch cans first (or at least better than stock PCV option), and I wouldn’t even mess with restrictor bolts unless you have a specific need for it.


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Good info and first I heard of this. I haven't done much research into this as most say just get the bolt when getting a catless downpipe.

My far uses minimal oil and doesn't smoke at all. I will hold off on the bolt and see if it starts. I have a occ to install next.

 

Interesting points. I have an OCC and have since 450 miles on the car. The valves are still filthy but that’s expected.

I’ll keep the bolt on reserve and see if I need it. If I do it’s a pretty easy thing to swap since it’s on top. I’m surprised that it’s somewhat accessible as most things that need changin are tucked away in small-spaces-land.


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Sounds good, I would do the same if I were you. I think the smoking would start right away if the downpipe was gonna cause it by itself. You shouldn't have a problem selling the banjo bolt if you don't need it.

 

Catless downpipes remove back pressure and allow the turbo to spin more freely, which generates more heat. More heat requires MORE lubrication to cool it down. More specifically, FRESH lubrication. If the hot oil isn’t evacuating the turbo properly via the drain line, it stays in the journal and gets even hotter and loses its viscosity, burns up and cokes up the turbo. Also, because the oil isn’t getting out, it pushes past the seals and burns off in the exhaust, causing the “smoky turbo” problem. Adding restrictor bolts to this problem may solve the symptom by reducing or even stopping the smoke because less oil is pushing past the seals, but it makes the problem of heat and poor lubrication coking up the turbo even worse, as you now have too little fresh oil entering, which will just cause it to fail even faster.


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