Welcome back to Project GT-R! I’ve had so many people ask me about the car that I thought it was about time for an update… With work and life in general getting in the way, I haven’t been out in my BNR34 nearly as much as I would like, but that said, I’ve actually driven it more than last year, which is great I guess. The Skyline is currently running on its old 19-inch RAYS Volk Racing CE28Ns that I’ve had for over a decade now; they’re a set I like to refer to as my ‘street’ wheels. I fitted them late last year in an attempt to finish off the old Bridgestone RE-11s, which although date back to 2008 still have plenty of life left in them and remain ridiculously sticky. A few spirited touge drives have done nothing to wear them down, so I think I’ll have to just kill them off on a track day or something.
But aside from that, the car has been maintained in tip-top condition. The mountain of boxes for the much-awaited next round of mods has grown since the last time you saw the Nissan; the most exciting addition being an HKS V CAM kit which will be fitted once the turbos get replaced. Haltech will be sending me its new Elite engine management system and once that arrives I should be ready to go. I say ‘should’ because I’ve decided to control the HKS V CAM through the Haltech and therefore need to make sure that an additional cam sensor is thrown into the mix so that the ECU can take care of everything without the need for auxiliary modules. This is what all the delay has been about in case you were wondering. But don’t worry – with Ito-san at Do-Luck helping out and a solid technical backing from Haltech, I’m sure I’ll get there in the end.
In the meantime, I’ve been doing a lot of chatting with the guys over at Turbosmart, specifically about my overall goal with Project GT-R. That is, to create a very driveable car with a strong, torquey mid-range and minimal lag. Inevitably, we ended up on the subject of aftermarket blow-off valves (BOVs), an upgrade I’ve been pretty skeptical of, primarily because I couldn’t see any benefit in running them except for an increase in whooshing noises. If that’s the sort of thing you are after, great, but sensing there was no real performance benefit I dismissed it as something not for me. But then they told me about their new Turbosmart Smart Port BOVs and things began to get interesting. By design, these would actually allow the turbos to pressurize the intake tract quicker and therefore increase response. My interest was immediately piqued…
It seemed like there was a problem though – that being Smart Port BOVs are currently available only for the R35 GT-R’s VR38DETT. But once I expressed an interest, Turbosmart was happy to build a custom pair for the R34 by combining R35 valve portions mated to RB26-specific flanges. The prototypes were shipped to me from Australia in a couple of days, and once they arrived I took the car straight down to Do-Luck in Yokohama to have them fitted.
You can get to the stock blow-off valves without having to remove the front bumper, but due to the front diffuser there are still a ton of bolts to undo.
Once the main diffuser section and second cover behind it under the oil pan is removed, you’ve got access to the bolts that attach the inner fender liner. Then it’s just a matter of removing the right-front wheel to reveal the two factory recirculating blow-off valves that are fixed in position at the corner of the bumper.
Of course, having a lift (note the recess in the ceiling at the Do-Luck shop to ensure cars can be lifted sufficiently) is always a bonus, as is having an experienced mechanic do the work for your while you just stand around and shoot every step of the process.
This also gave me a chance to take a little gander under the car. This is always slightly depressing, and I noticed more stuff that has rusted and will eventually require some TLC.
In The Pursuit Of Response
But back to the job at hand… The two BOVs are bolted onto a cast section of aluminium piping which is secured in place via two brackets that ensure the whole ensemble doesn’t shake around. The recirculated air – which has been metered and therefore fuelled for – gets channeled back to the turbo side right after the AFMs. This is also the reason why, that when fitting an atmosphere-venting BOV to a GT-R the engine tends to stall, as it runs rich for a second.
Either that or you shoot big flames out of the exhaust! The Turbosmart Smart Port gets around this issue by design, but I’ll get to that shortly.
The first step was to undo all hose clamps and the bolts holding everything in place.
Voilà, the stock setup removed. As Turbosmart explains it, “Factory BOVs are very responsive to throttle changes as they do not require a high amount of vacuum/boost to open. Small throttle changes are enough to create a pressure differential between the top of the valve (vacuum) and the bottom of the valve (boost) to overcome the spring force and open the valve. Turbocharger response however is slightly diminished. This is due to the fact that the turbocharger is not able to pressurize the intake system because the valve is open. Air is travelling from the compressor, through the valve and back to the intake of the compressor. Boost can only be built when the valve closes. This causes a slight delay when the driver reopens the throttle as the valve needs to close to allow pressure to increase.”
Here’s what the setup sounded and responded like when I still had the stock BOVs in place. You can hear that the actual dump sound is very muted, and is actually flutter coming from the turbo side of the engine rather than where the valves are located.
On to the Turbosmart BOVs…
Each valve comes in its own box and is supplied with a gasket and a silicone vacuum hose as well as a CD-ROM with fitting instructions.
Of course, the quality is top-notch and there’s full aluminium construction for both the body as well as the flange section. The Smart Port has an aluminium piston which makes it lighter and therefore more responsive to pressure/vacuum changes. It’s also hard anodized for lower friction and increased hardness.
But what sets this BOV apart is that it’s both atmosphere venting as well as recirculating. Turbosmart initially developed it for drive-by-wire applications where even the smallest of pressure or vacuum differences would send the ECU into panic mode, therefore making vent-to-atmosphere setups impossible to use. Basically speaking, this twin-port design combines the benefits of both systems, recirculating some pressure back into the intake and dumping the excess through the secondary valve in the vent-to-atmosphere port. The tighter and quicker close then allows the intake tract to be pressurized quicker, resulting in better boost pick up between gears.
The Swap
In theory it sounds like a no brainer, but I was keen to get it all fitted and tested.
Here’s a look at the underside of the piston. Pushing it up by hand, the Smart Port has a firmer and tighter action.
Of course, its action is adjustable by simply turning the top (black) portion, hardening or softening up the spring. Check out the corrosion I found on one of the stock BOVs!
There was a bit of oily blow-by residue inside the piping, so that was quickly flushed out with the use of some brake cleaner.
The Smart Ports were shipped out with the R35 29mm flange for the recirculation side, so Turbosmart included the larger reverse-taper 38mm items to fit the R34. Incidentally, if you want to use the Smart Port as a purely atmosphere-venting BOV you can seal off the recirculating port completely with the included plate. Talk about getting the best of both worlds!
With the 38mm flange in place, it was ready to get everything plumbed back in position.
I was surprised how well the two silicone hoses of the stock setup had held up considering they’re 16 years old.
Better Boost Pick Up
And there you have it – all fitted in position and ready to go!
After clamping everything in place it was over to the vacuum side.
Since Turbosmart provided the small vacuum hoses, we got rid of the stock items which looked a little worse for wear after years of heat cycling.
After everything was fitted we spent some time adjusting the BOVs, first making sure they weren’t too soft at idle and then tightening them up further to ensure they stayed nice and tight until higher boost filled the intake tract. As you can hear through the clip above, the BOV sound is pretty evident now. It’s definitely something I’ll have to get used to, but the thing that surprised me the most was the perceptible difference in boost response during fast gear changes.
I’ve also noted a decrease in audible flutter, which you could previously hear when backing off the throttle slowly during in-gear acceleration. All in all, this turned out being an upgrade that added a noticeable improvement to the car’s performance and character, plus my son seems to really like the loud ‘whooshes’ the BOVs throw out when I back off the throttle. Smiles all round then!
Dino Dalle Carbonare
Instagram: speedhunters_dino
dino@speedhunters.com