How easy is it to tune the NUR spec R34 compared to the standard car? do you still need to change the head gasget and the ECU etc to get 550/600bhp, information is much appreciated! and are you expecting any more?
Sorry for late.
I have just found this thread.
NUR engine is based on N1 engine block, so the strength is definitly better than the standard engine.
More than a half of standard RB26DETT blocks have been broken when we tested the 500ps engine based on standard RB26DETT engine on the engine bench.
N1 engine has thicker rib than standard one, so it is much stronger than the standard block.
If you'd like to go for more than 440ps, at least you should change air flow meters, injectors and fuel pumps.
The factory air flow meters and injecotrs are applicable up to around 440ps, and when you change the injecotrs, you need big capacity fuel pump as well.
Further, when you use more than 1.2 bar boost pressure, you should change head gasket.
The difference between standard RB26DETT and N1 RB26DETT is thicker ribs, pistons, piston rings, con-rods, smoother exhaust manifold, etc.
And the difference between N1 engine and NUR engine is basically the same, but the big difference is the weight balance of piston and con-rods.
Nissan uses the +-1g balanced pistons and con-rods for NUR engine, so NUR engine is much smoother than the standard N1 engine.
By the way, the initial RB26DETT for GTR32 used to use N1 block, but because of the cost, the engine block got thinner.
Finally, there are generally three type of engines.
I have seen and heard of numerous GTR's running 1.4-1.5 bar putting out approx 600ps, and these were running standard airflow meters and some with standard head gaskets without a problem. I have also seen dyno tuning results for some of these cars & A/F ratios were around the 11:1 - 12:1. I agree injectors and fuel pump must be changed.
The thing that concerns me though is that you mentioned that more than half the standard RB26DETT engines you tested broke on the test bench. Was there are common area on the block they were breaking at ? Are the conrod bolts too weak in the standard engine?
What sort of tests were you carrying out on these motors, like were these destructive tests to see durability or were they run at a maximum and consistent 8500rpm rev limit ?
At first, this is totally my personal opinion, and I have to apologies about my bad explain in English.
It is up to you whether you agree our experience or not, but actually, more than half the engines broken at 500ps endurance bench test.
I'm not talking about the sprint use because owners usually do not maintain their cars often.
In the case of demonstration cars of tuning garages, they open their engine very often and keep their condition best. And in fact, almost all the reliable tuning garage in Japan uses N1 block instead of standard one.
You cannot manage the condition such as tuning garage's demonstration cars.
Demonstration cars are for demonstration. The purpose is usually totally different from the customers cars.
By the way, Super Taikyu Series(Gr.N endurance race) cars use N1 engines because of the strength.
Their engine produce still around 450ps, but they run 6 hours constantly.
Nismo's test tested 450ps with standard engine. When they done around 1,000km of on the track test, the engine cracked. And on the bench, 3 of 5 engines cracked.
Of course it depends on the driving situation and chassis specification etc, for our quality control, I recommend N1 block for our customers who want more than 450ps.
And anyway, many owners don't use 500ps+ fully all the time, and "Max power 500ps" is one thing and "Using max power constantly" is totally another thing.
Your decision is between "Thick and short life" and "Thin and long life", and when you chose high power and short life, it is a quality of life for you. But you can save your life with taking proper way and management.
The crack is usually appeared around engine on the bracket exhaust side.
I usually recommend around 400ps and I'm always thinking about reliability instead of sprint performance.
It is not block fail.
Nissan do not have to consider about aftermarket modification.
They have to consider about durability such as 6 years or 100,000km with 280ps.
The reason why they have N1 engine is that they cannot garantee the durability with the std engine for the race field.
Of course the GTR's you drive are homologation model for race, but they are sport cars and not racing cars.
Understanding that the main requirement for a road car is durability, the reason I ask about the crack, is to determine if it would be detectable before failure.
Some types of crack grow within a very short time, others slowly become detectable and then propagate rapidly to failure, others will become detectable rapidly then take a long time to reach a concernable size.
Most cracks fall into the 2nd or 3rd categories above, and it would be a benefit to know the area of the cracks initiation, so when the tuners are putting together or re-building high power engines a simple NDT check could detect it and save an expensive build from ending in premature block failure.