There are couple of points I’d like to mention for Rb25det skylines modifiers.
1. Factory intake pipe must be replaced. It is too small for any thing above 240rwkws, We’ve done a back to back test regarding to it, and result is here. Some thing of a hard metal pipe around 4 inches is recommended.
2. We did couple of tests using our ATR43G3 .82 rear housing on factory exhaust manifold and found its restrictive and not very useful for any thing above 280rwkws internally gated on 98 fuel. To a proper made steam pipe manifold, there is 2~3 degrees differences in top range timing with 25kws of power. How ever 280rwkws is still respectable for a standard engine. Welding an external waste gate on factory exhaust manifold can also increase power output substantially.
3. If you own a R33 GTST with a standard Rb25det in it, then it is a good idea to not run any boost above 20psi, the factory valve springs and hydraulic lifters are not strong enough for it. It is noticed from a strange power curve like in this sheet here, and ultimately wears out valves and valve sets.
4.A good tuner is extremely important for the final outcome. I’ve seen many bad tunes, not only making less power with poorer drivability, some of them a potentially dangerous that leads to engine failure. Examples Power curve, Boost curve, AFR. Unfortunately we don’t tune cars, how ever I’m happy to introduce a good tuner to you if you are in Australia.
5. I’ve seen many people use return flow intercoolers for convenience of installations. We’ve tested few and found most of them carry a massive pressure drop in between the cores. Here is a comparison using a Jap branded return flow cooler kit that resulted 8psi pressure drop at 18psi, pressure graph before and after cooler is here. I personally recommend proper front mount intercoolers with core size of 600x300x75mm.
6. Exhaust plays a critical roll in a high performance system. The engine only makes more power if greater volume of air can be shifted through the engine system. Restrictive exhaust can cause an rise in EGT that increase knock levels as well as the inability in boost control. 3.5 inches straight pipe will be ideal for RBs if it not going to be used on road. I always recommend of doing dynos run with exhaust dropped before the finalise of a tune. An example of exhaust restriction: With exhaust, Without Exhaust (dropped from cat).
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