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Tuesday, March 24, 2020

Big Bird 2 Updates : Gathering Parts : Doing the Multi Car Shuffle : Twin Turbos for RB engines


The world is a weird place right now, however there is still work to do, cars to build. We will reach the other side, by getting there.

Since we have been working on the Nissan Skyline GT-R for 20 years, we have gathered a lot of parts over the years.  We have been importing 25 year old cars since 2014, and that has also allowed us access to a ton of cars and parts.  Here are some of the parts that are going to go on Big Bird 2. The general idea is RB30, twin undermanifold turbos, nitrous, OS88 transmission. It should make good power off the bottle, and much more on it.

Throttle refresh set from Reimax
Reimax is/was Reinik, the guys responsible for the Group A R32 GT-R engines. They have some very unique engine parts.  The throttle refresh set was something we bought many years ago, seems like a good thing to add to a car, we are going to turn some boost onto.

To Bosch 044 fuel pumps, hard lines and a surge tank. Plus nitrous collector

The fuel system in any modified car has to be up to the task. I will always stress fuel system, because it is not a single component, it is the system of components. That is fuel pump, lines, injectors, rail, filters. For now, we are going to use this twin Bosch 044 setup.  This is a proven motorsports fuel pump that while a little loud, works.  The OEM pump will be used as a lifter pump to the surge tank. I am no huge fan of lifter pumps, but in this case, I will use what I have. This is a done setup, sitting on a shelf doing nothing. So it is going to get used.  On gasoline this setup will support about 1000 hp.  On E85 about 700 hp or so.  Although the 044 will pump at pretty crazy base pressures.  More information about fuel systems for Nissan Skyline GT-R. 

Also in this picture is the collector with nitrous installed.  The plan is actually to try and plumb this undermanifold, into the Nismo collector that the car already has.  The Nismo collector has bosses on the underside. Although the original style looks cool, we think that undermanifold will be cooler. As we said in the last post, we aren't building an exact replica, but rather what 20 years has taught us.
Nismo collector, this isn't a plenum as it is pre throttle body.  
Some ARP headstuds. Hopefully they fit
The RB30 blocks used a 10 mm head bolt.  The RB26 uses a 12 mm head bolt.  Normally when R26 heads are bolted to RB30 blocks, the block holes are upgraded to 12 mm.  A stud holds a head on better than a bolt, as the twisting action of the bolt vs a nearly vertical pull of a stud.    We have a few sets of ARP 2000 headstuds that we want to use on the 30. Along with the studs, we have a Tomei metal headgasket. If we were really serious, we might get some L19 headstuds, and o-ring the block. However, not really that serious right now.

HKS ATI damper setup with alternator
The engine we bought for Nismo #500, N1 block, full counter crank, 270 cams, had a HKS ATI Super Damper setup on it.  That setup came from an R33, so its going back on one.  The HKS setup includes pulleys and a different alternator setup. 

Nismo #500 and the Automotiveforums.com R34 race car
Right now the R33 is out at Wakitas getting the engine and transmission removed. It will then be headed to paint. Yellow is coming soon.     Next is Nismo #500 is headed to get a transmission swap. The OS88 sequential transmission, and Tilton triple plate carbon clutch is coming out, and that will go in Big Bird 2.  The stock trans will go in Nismo #500.   Then at some point I need to finish installing all the parts I have for Nismo #500. It starts, runs, and drives, but have a ton of upgrades for it.


Going to try the JGTC inconel exhaust manifolds on Big Bird 2.  We want to stay undermanifold, and have had these for several years.  These manifolds put the turbos out and at a different angle than stock.  Since the car is getting an RB30 anyway, not too big a deal. We were going to have to redo inlet and turbo outlet piping. Hopefully it all clears.  Now onto turbos.  Not sure what we want to run on it. In the end, we will be limited by the size of the exhaust housing.  On paper there are a few turbos that can make a ton of power, but in real life we are yet to see them make anywhere near claimed output. #staytwin

Rear turbo has the JGTC manifold on it. These are Nismo turbos

To make the kind of power we want, the minimum sized turbo we would be looking at is something like the HKS GT-RS or the 2871-R.  AKA a 2871-10  707160-10.  We have done over 600 wheel horsepower on a 2.8 with these turbos. Response was good, when cam timing was tuned correctly.  These are bolt on RB26 turbos.  53 mm inducer, 71 mm exducer on the compressor side, 54 mm inducer and 47 mm on the turbine side. 76 trim, with a 0.64 A/R. In the meat of the efficiency they flow about 35 lb/min airflow at 2.5 pressure ratio on the compressor. Exhaust side with the 0.64 trim maxes out at about 17 lb/min at 2.5 pressure ratio.  These are older turbos, but they work, are proven, and easy.

GTX2971R turbocharger from Garrett and ATP

Garrett GTX2971R dual ball bearing turbo for the Nissan Skyline RB26DETT platform. Direct drop-in upgrade turbo for the stock Nissan Skyline RB26DETT twin turbochargers.
The GTX2971R features an ultra high flow compressor wheel and Garrett 11-Blade technology. 560HP potential flow.
These are pretty huge. 54.1 mm inducer. 71.4 exducer on the compressor side.  56.5 mm inducer and 53.6 mm exducer on the turbine side. In the meat of the efficiency they flow about 40 lb/min airflow at 2.5 pressure ratio on the compressor. Exhaust side with the 0.64 trim maxes out at about 19 lb/min at 2.5 pressure ratio. In theory these should do about 100 horsepower over the GT-RS at the same boost levels.  But wait, there is more.  The next step up in the GTX bolt on RB26 lineup.

GTX2976R turbocharger from Garrett and ATP
Garrett GTX2976R dual ball bearing turbo for the Nissan Skyline RB26DETT platform. Direct drop-in upgrade turbo for the stock Nissan Skyline RB26DETT twin turbochargers.The GTX2976R features an ultra high flow compressor wheel and Garrett 11-Blade technology. +600HP potential flow.

If the last ones were big, well these are more bigger. 58 mm inducer, 76.6 mm exducer. However the exhaust side is the same.  We have run into issues in the past when, even stepping up the compressor side, we saw no more power as the turbine was just tapped out.  We think this could be a possibility here with this turbo. In the meat of the efficiency they flow about 45 lb/min airflow at 2.5 pressure ratio on the compressor. Exhaust side with the 0.64 trim maxes out at about 19 lb/min at 2.5 pressure ratio. Again in theory another 100 horsepower over the GTX2971, 200 horsepower over the GT-RS turbos.

Gen II GX 2876R bolt on RB26dett turbos


One other potential option is the Gen II GTX 2867R

Garrett GEN2 GTX2867R dual ball bearing Twin Turbochargers for the Nissan Skyline GT-R RB26DETT. Supports 1,000HP+ in twin turbo configuration.

50mm inducer, 67 mm exducer on the compressor side. 54 mm inducer and 47 mm exducer on the turbine side. Right around 35 lbs/min on the compressor, and about 17 lbs/min on the exhaust side.  Even if the compressor side is better, if the exhaust won't let the flow, it will not make any more horsepower.  They say the new GenII wheel can produce up to 20% more than the previous version.

Where theories and realities meet are on the dyno. When working on another vehicle, we did several hotswaps of a single turbo setup with different turbocharger setups. The exhaust housing stayed the same, and even with three different turbos, we saw almost the same amount of power. Until we swapped exhaust housings did we see more power. Everything shifted right about 300 rpm, but we gained the power we were expecting.  We were not logging exhaust backpressure pre turbo, but it is something you should think of logging if you are serious.



Then there are some other options now, that this car has the JGTC manifolds. Those include the new G series turbos.  Those will not be exact bolt on, and they won't work for most, so using them may not really gather much real data.  The G25-550 - 48 mm inducer, 60 mm exducer compressor side, 54 mm inducer 49 mm exducer on the turbine side. Compressor flows about 32 lbs/min at 2.5 pressure ratio. The T25 flanged exhaust side is a 0.49 trim, and flows about 15 lbs/min at 2.5 pressure ratio.

G25-660.  54 mm inducer 67 mm exducer on the compressor side. 54 mm inducer and 49 mm exducer on the turbine side. That turbine side, could be an issue with making power on a T25 footprint.  Compressor flows about 42 lbs/min at 2.5 pressure ratio, the exhaust is still about 15 lbs/min at 2.5 pressure ratio.

The extra displacement of the RB30 will move all the power to the left, the bigger turbos shift it to the right. So in theory the big turbos should respond similar to stock, but may be able to make double or triple the stock horsepower....off the bottle.

Stay tuned to some more build information, pictures, thoughts, and what parts we pick, and why soon.


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