Replacing the GTR's turbos and the importance of an air intake

As I found out in my first visit to Nismo Performance Centre Tokyo (NPC). The past history of my car having been tracked with collapsed catalytic converters, Koyama-san from NPC advised that I change replace the turbos as they may or may not blow.

He gave me a quote on parts and labor which equaled around $6000 USD. Definitely not cheap and one I would need to save up a bit for, so I told them I would bring the car in during the summer of 2018 just inline with my mid-year oil change as a turbo change comes part and parcel with an oil change.

So what turbos did I spec to replace the worn ones? Exactly the same standard specified to the Nismo S1 RB26, which is the BNR34 GTR's standard ball bearing turbos. Having a complete Nismo engine, naturally i wanted to keep the car true to it's origins over chasing more power which an aftermarket turbo solution would offer. In my opinion power is no longer a challenge nor achievement. Cars these days are about the feel and feedback, the character of the engine and how the power is delivered rather than numbers on a dyno sheet.

The BNR34 Garrett turbos are still in production but in most cases are built to order so it will take a couple of weeks for them to order these parts in. The turbos used in the BNR34 are a pair of Garrett GT2860R. They are listed as Turbocharger Assy BNR34, Nissan part number: 14411AA300 (this only includes 1 turbo so yo will need to order 2 of this part number).

So this process involved changing out the turbos and replacing all related assembly and also the O2 sensors (Nissan part number: 2269024U03 and 2269024U02 respectively) which are something you should also do when replacing turbos, would take around 2 weeks. In addition to this I thought I would use this opportunity to address an issue which had been nagging me since I bought the car.

As is can been seen it is not possible to fit the standard OE airbox duct. This makeshift one is about as much of the factory duct that will fit due to the over sized aftermarket radiator.

After much consultation with Yamazaki-san of NPC it seemed only a stock OE radiator would allow the fitment of a duct without modification to the duct so I ordered a standard radiator. Yamazaki-san said many of their customers actually track their cars with the standard radiator (part number: PL020442R33M This is a part produced by Pitwork, a Nissan OEM) without any issues. So given my car also has a separate oil cooler it would be OK to ditch the large radiator. An added bonus would be reduced front overhang weight by reverting back to a smaller and lighter unit which Nissan during the development of the R33 a light weight radiator was a core part of their design for the car. 

Lastly the radiator shroud was cracked on one of the mounting points and was missing the top cover which fits on top so I also ordered a new piece (Nissan part number: 21475-81T00). According to Yamazaki-san having the plastic cover which fits on top of the radiator itself makes a huge difference to the effectiveness of the radiator itself.

2 Weeks passed and it was time for me to go pick up my car. Another fun fact NPC has a underground car storage basement where they keep customer cars so another piece of mind that your car will be kept warm and dry while it is there.

Upon arrival in the morning I was greeted by this customers GTS25t Series 1. Not only are these are rare sight over here in Japan now since most have gone abroad namely Australia and more recently North America, but also to see such a well kept example. The Japanese are known for taking good care of their cars in general but even then this particular owner was exceptionally anal. Everything on the car was newly replaced, even down to the lower grill mesh. The interior was clean as well with no gauges and even the factory seats in mint condition. The only modification was a vintage HKS exhaust and Volk Racing rims. Very tasteful spec indeed.

NPC's office/reception sits next door to their first lift So every visit you get a view of a different customer car. This particular one was a BNR34 Mspec Nur in for some basic maintenance. I was drooling over those R35 brakes, a future upgrade for my car for sure. P.S. You can see the roof of my car just peeking up below the BNR34 waiting to be taken home.

So here is the car back to a stock radiator. And yes the initial part i decided to try out is the Nismo R-Tune BNR34 airbox duct (part number: 16554-RSR46). In order for it to clear the bonnet/hood's underside reinforcement the NPC guys had to cut out some parts. The reason why I went for this solution was I intend to get the Nismo Turbo Inlet piping in the future so I was trying to get one that would clear the turbo piping without modification.

After a few weeks
 of use it turned out even with the modifications to the R-Tune duct it still was hitting the underside of the bonnet and eventually the duct itself started developing cracks where the bonnet was making contact with it.

So due to the shape of the R33's bonnet there are very few duct options available which also explains why so many people switch to exposed pod filters. This was a solution I did consider when faced with the fact my Greddy radiator was too big to fit a duct however  the lack of access to cold outside air pods would have.

So fast forward a few days with overnight parts from Amazon, I ordered a OE Genuine BNCR33 Nissan Air duct assembly (part number: 16554-24U00). Yes this will need slight reshaping when I fit the Nismo turbo inlet piping but after hearing that even the Reimax duct has some bonnet clearance issues I was not prepared to invest further money until I meet someone who runs one on their BCNR33. Furthermore Yamazaki-san of NPC told me also that a lot of their customers also use the standard duct so I'll go with this one for now.

 Here is a comparisson with the R-Tune duct. the key area to the top left of the "A" shaped part of the duct. That recess is designed to allow the reinforcement on the underside of the bonnet to clear the duct.

As can be seen in this picture. the black foam pads were placed there by NPC in an effort to prevent the bonnet underside from damaging the R-Tune duct. So yes the BCNR33 under bonnet real estate is quite tight as can been seen.

So here it is complete with the stock radiator and shroud as well as the airbox duct. I must say I am very pleased with the clean look this gives my car. Some eagle eyed readers may also have notice the change in strut brace to a BNR34 GTR strut brace. I fitted this as it is a affordable way to improve on the front rigidity as the BNR34 brace is thicker and more substantial than the BCNR33 brace.

Driving impressions:
As expected with fresh turbos the motor's pick up was smoother and also thanks to the new O2 sensors I noticed a previous minor niggle where the idle would be slightly rough at times was also smoothed out after they were replaced.
Also just when cruising on the expressway there was noticeably more torque on partial throttle thanks to the increase in cooler air coming from the duct.
For cornering and multi-story car park there ramps there was also a slight increase in solidity in the front end from the BNR34 strut brace as well.

So all in all a good refresh. Now that the engine is refreshed my attention does turn to the bushings and suspension link bushings which haven't been touched since new and an often overlooked area by many. This is a area I will need to address in the near future as well..