3. VR38DETT engine exceeded RB26?

VR38DETT engine’s maximum output is 480hp and the maximum torque is 60kgm.
Obviously, VR38DETT has much better performance than RB26DETT.
The rev at the max output is lower than that of RB26 by 400rpm. However, the remarkable fact is the rev at the maximum torque.
The engine produces its maximum torque from 3200 to 5200 revs, which is remarkably wide.
Many technologies evolved for these 5 years have realized such an engine character.

Text: Shunsuke Takeuchi
Photo: GTR-WORLD.net



Adoption of a secondary air system
The secondary air system which has been adopted for the rally cars for years, is the technology for improving the turbine response at re-acceleration.
This secondary air system has been adopted for the new GT-R and the high torque of 40kg is generated in the low load range.
And it has also made a great contribution to better emissions.
To meet today’s environmental standards, it is necessary to make the exhaust gas clean at cold start.
To clear the cold start emissions, it is required to activate cleansing performance by raising the catalyst temperature as soon as the engine started.
As you know, the turbocharger is the device converting the emission thermal energy to power.
It means that as the emission temperature drops by going through the turbocharger, the catalyst cannot be activated enough just after the engine started.
Actually, this is one of the reasons why the turbocharged engines faded and the natural aspirated engines became the mainstream.
Accordingly the secondary air system was invented. This system can activate the catalyst at earlier stage by technically raised exhaust temperature that is made by burning the unburned gas with the secondary air
By adopting this technology, even SUBARU IMPREZA has met the emission gas standards.
Of course, the turbocharged new GT-R meets the 2005 emission standard (U-LEV) with the secondary air system.

Newly-developed cylinder block
The VR engine is seemingly a VQ derivation because its bore pitch and bank angle are the same as those of VQ engine mounted on Fairlady Z Version NISMO 380RS.
However, the VR engine is totally different from the VQ engine.
Firstly, the VR engine cylinder block is made by aluminum, and the cylinder does not have the steel liner.
Steel has lower thermal conductivity than aluminum.
Therefore, combustion chamber can be cooled more efficiently without steel liner than with steel liner.
As result of efficient cooling of combustion chamber, it has enabled higher temperature combustion. And new GT-R can run with ideal air/fuel ratio in ordinary driving.
In addition, the emission has been improved.
Of course, the high-temperature combustion has made the high power possible.
The cylinder block is the type called “dry deck”.
The usual cylinder block has holes like water line, oil line and holes for weight saving.
But, the new GT-R cylinder block has only water line holes and oil line holes.
It means that new GT-R cylinder block has more stiffness than the usual cylinder block.
This technology is also the feedback from the racing field.

Manifold-integrated turbocharger
Well, the interesting turbocharger is integrated with exhaust manifold which may cause the tuning garages some troubles.
As the conventional turbocharger was flanged with exhaust manifold, only turbocharger could be replaced to bigger one to increase horsepower. But, it is not possible for the new GT-R because of its structure.
The reason of adopting manifold-integrated turbocharger is heat capacity reduction and weight reduction.
As mentioned before, the turbocharger is the device converting the heated exhaust gas to power.
Therefore, it is essential to deliver the heated exhaust gas from cylinder block to turbocharger with minimum temperature drop to make the turbocharger work efficiently. .
As for the conventional turbocharger, the thick flange could be the cause to drop the heat. Thus, the flange has been cut off.
Secondly, the turbocharger response is prioritized.
To improve turbocharger response, it is better to place the turbocharger closer to the combustion chamber.
Therefore, the new GT-R turbocharger is placed very close to the combustion chamber.
If the turbocharger was still with the flange joint, the location of the turbocharger must be further from combustion chamber.
Thirdly, we cannot ignore the issue of emission.
As mentioned earlier, the cold start performance is very important for recent emission standard.
This is why the catalytic converter should be placed closer to the engine as much as possible.
On the technical background which materialized this layout, we should mention about the new materials such as heat-resistant cast steel which can resist emission heat of about 1000℃ at the ideal air/fuel ratio.
Well, the boost pressure is 0.75bar.
However, the boost pressure is controlled electronically in order to get the stable output character in spite of the variation in environmental factors such as atmospheric pressure and temperature.

Lubricating system also advanced
On VR engine, the lubricating system has been also greatly advanced.
Many RB engine owners must have got troubles of oil lubrication.
It must have been necessary for especially sport driving to place baffle plate on the oil pan as to prevent the oil from leaning to the one side and also to install air-cooled engine oil cooler.
The new GT-R has already incorporated these measurements for the lubricating system.
The lateral wet and the dry sump lubrication systems have been introduced to enable the stable oil supply at 1.8G.
The engine oil cooler has been also fitted as standard equipment.
Also, as the V-engine turbo is mounted at a lower level, the scavenger pump forces the oil suck out.
For your information, the required oil is 6.5L.
It is reasonable volume of oil for the performance car with the engine oil cooler.