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Rb26 V Rb25 V Rb30

quincy777

By quincy777,
in Engines & Forced Induction

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nedb Proficient

nedb

Posted
Posted (edited)

230rwkw is plenty for a street car which is daily driver but if you can get more with the right turbo setup that would be even better. Also, considering it's an auto I prefer nice and early spool over full boost high in the rev range.

Any one got a "recipe" what needs to be done to the 25de to handle the power apart from the valve springs. What can you reuse from the rb20det and the rb25de?

Would you end up with 2.5l capacity or can you also use gtr crank and rods with different pistons and change the capacity?

Edited by nedb
B0oStEr Mentor

B0oStEr

Posted
Posted
230rwkw is plenty for a street car which is daily driver but if you can get more with the right turbo setup that would be even better. Also, considering it's an auto I prefer nice and early spool over full boost high in the rev range.

Any one got a "recipe" what needs to be done to the 25de to handle the power apart from the valve springs. What can you reuse from the rb20det and the rb25de?

Would you end up with 2.5l capacity or can you also use gtr crank and rods with different pistons and change the capacity?

I'm still in the rebuild process.

Rb26 rods with arp rodbolts and head studs are good insurance.

I found a 2nd hand rb26 crank and had the oilpump collar done but the capacity increase (70cc) is minimal for the cost.

The capacity with an rb26 crank will be the same as an rb26 with std bore 2568cc.

You need rb26 pistons as the pin height is different even though the bores are both 86mm

I'm using 87mm rb26 wisecos and the capacity will be 2628cc.

The r32 rb25de is just an rb20de with a longer stroke, bigger bore, bigger valves, inlet ports and runners.

Everything else is interchangeable.

I decided to use an r33 rb25det block so I could keep the piston oil squirters although it's not essential.

B0oStEr Mentor

B0oStEr

Posted
Posted
I'm sure many will agree with me..

220-230rwkw is actually not that fast... 250rwkw+ is whats needed.

The R32 Rb25de will be fine. Be sure to change the valve springs. :D

No doubt new valve springs are a good idea but are the std rb25de valvesprings weaker that rb20det valvesprings?

In the r32 manual they are rated as having the same seat pressure as the rb26 at 24kg at installed height.

Cubes Grand Master

Cubes

Posted
Posted
No doubt new valve springs are a good idea but are the std rb25de valvesprings weaker that rb20det valvesprings?

In the r32 manual they are rated as having the same seat pressure as the rb26 at 24kg at installed height.

Seat pressure is only one measurement. There's also open pressure.

The RB20det valve springs are the same as the r32 rb25de, the big factor here is the rb25de runs larger valves so more difficult for the valve springs to control, in n/a they are fine, push a bit of boost and exh. back pressure in to the equation that places pressure on the back of the valve to hold it open and this is where you begin to run in to trouble.

Read around half way down of the following doc. http://www.cranecams.com/?show=faq&id=5

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