Tuesday, June 18, 2013

BNR34 Rear Diffuser Project, Intro

So I’m not sure why this mod is not more popular overseas, I've seen a couple on R33s at the SSCT gatherings, and even on the Minkara car blog here in Japan, there are several examples of people who have installed the R34 V-spec rear diffuser onto their R33s.

In my study of the R33 GT-R vs. the R34 GT-R, one obvious engineering difference, if not THE difference, was the aerodynamics that the R34 had. And, the most obvious piece was the rear diffuser. Thus, I’ve been wanting to do this mod for quite some time now.  So I did some research, learned that it basically bolts on, but first I wanted to confirm this so and then found and bought a used BNR34 diffuser on Yahoo Auctions.  This was over two years ago! (so yes, it sat there collecting dust all that time...)

It turns out however the tricky part was, despite its “bolt-on” nature, figuring out exactly how the diffuser would be attached to an R33.  Luckily, all that is really needed is to either weld on the necessary nuts onto the existing “triple cross bar” or to replace the R33’s triple cross bar with the R34 V-spec’s triple cross bar, which happens to be identical except for having the necessary brackets already welded on.  The triple cross bar is three pieces of pipe in the rear that extends from side to side in a rough “U” shape - here is what a standard R33 “triple cross bar” set looks like (bottom piece is towards rear, top is in front of the rear wheels) :

Courtesy http://minkara.carview.co.jp/en/userid/886880/car/866742/3781685/parts.aspx
And here is the R34 one, with the differences (that is, where the diffuser is bolted onto towards the front), highlighted:
Courtesy: http://minkara.carview.co.jp/en/userid/301215/car/194604/415795/note.aspx 
So I first had to find a used 34 V-spec triple cross bar. This I did by contacting a dismantler.  Then, it turns out that the used diffuser wasn't in the best condition, either missing some brackets, or the existing ones were extremely rusted and bent out of shape, so I had to find a tuner that could supply me with replacement brackets.  
Yeah, this isn't going to work...maybe stainless steel is a good idea, given the location?
I searched for a while in Japan and found one place that was prohibitively expensive – however Allen at Tomei Powered introduced me to RB Motorsports in the UK, who had a bracket kit of stainless steel brackets, bolts and rivets, just for this purpose!  

Unfortunately, as I found out later, this solution was not a complete one.

So after collecting the diffuser, the triple cross bar, and a set of bolts and brackets, it looked like I was good to go. I now had everything I needed to do the install. So this project was essentially broken down into the following steps: 1) restoring the carbon diffuser and then 2) ensuring the diffuser could be attached to the R33, 3) temporarily attaching the diffuser to get it to my tuners shop and then finally 4) full installation, including getting custom brackets made in order to make it work for the R33.  In order to make this easy reading, I’ve broken up the posts into 4 sections. 

Meanwhile, here are some links to Minkara posts showing other R33s with the BNR34 diffuser mod:

A nice LeMans

Black V-Spec

Silver Tommy Kaira tuned

White Race Spec

Midnight Purple Autech 4 Door GT-R

R33 GTS25T Type M

Midnight Purple 2.8L (with decent photo instructions)

Stay tuned for Part 1, next!

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