What to know about BNR twins for buying used
 

Hey guys -

So, one of the guys here (Nick) bought a set of BNR twins used to go on his engine I just rebuilt. Got the car running for the first time Saturday, running great, looking forward to setting up the twins once it's all broken in.

This was my first time seeing BNR's in person, they are REALLY nice and well done, and a killer upgrade for keeping the sequential system but getting more flow and more power. Now that more of them are out there, you may see them pop up used more often, so I just wanted to document a few things about the BNR's to make it easier to install a used set.

The big change on the BNR turbos is the center cartridge of the turbos themselves. It's an upgraded bearing section, and the compressor and turbine wheels are different and larger for more flow and efficiency. In doing that, the turbos are SLIGHTLY longer than the stock turbos, and that's where some of the changes and modifications come in.

OIL SYSTEM
- Oil feed line has to be slightly bent outwards. I put an end of the line in the vice then bent a little, test-fit, then bent some more. I tried to do each end of the line equally. You don't want to over-bend the line and you want to go SLOW. Stock, looking at the line from straight down, the fittings on the line where it bolts to the turbos are at a straight 90 degrees out from the top line. Once done, each end will be kicked out about 5-10 degrees. The stock banjo bolts and crush washers bolt it right up. The feed line that goes to the block remains the same, bolts right up to it. You may have to loosen the banjo bolt where it goes to the block to clock that line slightly.
- Oil return lines are the stock lines and stock metal gaskets. It will be slightly trickier to bolt them up as they aren't dead lined up like they would have been stock. The stock 10mm bolts holding them on have little "nubs" at the end of the bolt, that helps pilot the bolt in and get it going. This was crucial for the front return line bolting to the front cover extension. You want to get the bolts in place first, maybe a thread or two in, then tighten. Make sure you are putting the bolts in straight, they can want to pull to the side and get cross threaded.

COOLANT SYSTEM
- The coolant feed and return lines that bolt to the sides of the turbos is the same deal as the oil line - they need to be bent a little bit outwards to fit. But, you use the stock banjo bolts and crush washers. To note - the N3C1 turbos and N3G1 turbos have a thicker casting for the turbine housings, and the engine side coolant pipe is shaped slightly differently to fit. This can be tricky to track down if you don't have the right line as the visual difference between the two is VERY minor.
- Rubber coolant hoses are just the stock hoses, no problems there. Use the OEM Mazda hoses and hose clamps for best fit and life.

Y-PIPE
- The back half of the Y-pipe with the charge control valve (butterfly valve) is identical.
- The front half is lengthened by BNR. They cut the O-ring flange at the back of the Y-pipe off and weld in a short piece of aluminum tubing. If you want to change from a 93-95 Y-pipe to a '96+ y-pipe with the 2-bolt flange instead of the rubber coupler, you would have to have that front part of the Y-pipe modified by BNR or a local welding/fab shop.

TURBINE HOUSINGS
- The hot side of each turbo (the turbine housing, the cast iron part) is bored out and machined by BNR to fit the larger center sections. If you need to swap one out, they can do the machine work on a spare or you can buy one from them.
- The used turbos Nick got were permanently set up for non-sequential with the precontrol flapper removed and welded shut. We sent a spare secondary turbine housing to BNR and they did the machine work so we would have a sequential turbine housing.

EXHAUST
- Downpipe, manifold, and gaskets are all stock.

INTAKE
- The compressor housings are modified by BNR for the larger compressor wheel. They also engrave the BNR logo on both compressor housings. Again, if you needed to replace one, get with BNR for the machine work.
- The opening on the intake side is a good bit larger. It could be worth opening up the stock gasket and turbo inlet pipes to match the larger diameter. Not necessary, but could make for more performance.


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Hope that sheds some light. I wanted to document all this while it was fresh in my mind.

Dale

As usual, nicely documented. Thanks Dale.

This is great. Thanks!

very good info!

Be interested to know what ceramic coating Bryan uses, seems to be very long lasting.

BNR Stage 3s are a great upgrade for those who want more reliable power, but aren't ready to step up to a single, or even those who want to replace a failing set of stock twins. I've made a solid 420 wheel hp with these. They can do more when pushed. I've achieved a bar of boost under 2000 rpm.

They use custom spec GT28 cartridges. The stock compressor covers and turbine housings are precisely machined out to accommodate the larger wheels.

The y pipe is lengthened and included in the price.

The oil and coolant lines are slightly re-clocked. They should come already done but I have seen cases where they are a bit off, most likely due to bumping in shipping. The twin turbos are difficult to package no matter how carefully you pack them.

They have none of the problems of rebuilt twins.

I have new sets on sale for $1800 right now. They normally retail for $2100.

I'm still waiting for my from group buy. Can you find out for me when it will be shipped to me.thanks

Bryan is an awesome guy. I see him from time to time up at his shop, and he puts alot of hard work and detail into every set. Always helpful, very knowledgeable, and has a quite a few crazy builds of his own. Can't believe its been over 10 years that these twins have been doing work!