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rb25det intake side same as rb20det intake side?

carl h

By carl h,
in Engines & Forced Induction

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Cubes Grand Master

Cubes

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No they are very much different.

The R32 RB25DE N/A Head has the same designed/shape ports as the RB20DE/T but they are a decent amount larger.

The R33 RB25DE/T ports are slightly bigger than the R32 RB25DE BUT they appear to have slightly smaller valves (34mm on the inlet & 29mm on the exhaust vs the RB26DETT & R32 RB25DE's 35mm on the inlet and 29.5mm on the exhaust)

(RB20DET valves are 30mm inlet & 27mm exhaust, which explains the reason for needing so much more boost over the rb25 to make power)

This is by my measurements, not that valve size is relevant to your question but I find it interesting. :)

You could do a bit of chopping and welding of a R33 RB25DET Greedy plenum/inlet manifold with a rb20det inlet manifold but that would be the last resort. :D

carl h Proficient

carl h

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hrmmmm.

doesnt make much sense to buy a greddy manifold and then tear it apart and spend who knows how much more money to make it work.

i think i will stick to the original plan and buy a r.i.p.s. manifold, they look the part and apparently peform very well.

hrm..... as for the valve bit guess i will (when i do) put oversized valves into the rb20 head as well as other bits.

carl h Proficient

carl h

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Yep spend all the $$ you can on the inlet side of the RB20det to reduce that airflow/boost ratio.

kind of confuzzled on this, what exactly do you mean?

like less boost for more airflow? or more airflow for less boost?

Cubes Grand Master

Cubes

Posted
Posted
kind of confuzzled on this, what exactly do you mean?

like less boost for more airflow? or more airflow for less boost?

With a better easier breathing head it doesn't require as much boost to achieve the same airflow in to the pots. Hence less boost is required to make the same or more power.

Boost is a measurement of restriction.

Look at how much boost the SOHC RB30 guys run.

Cubes Grand Master

Cubes

Posted
Posted

Scratches head.. So if you had an RB25DE head will the rb20det inlet manifold fit on.

Yes it will BUT the ports of the RB20det inlet manifold are quite a bit smaller than the rb25de ports.

Best bet is to use the rb25de inletmanifold on the rb25de head with a rb20det plenum as it has all the fittings for the turbo requirements.

BlueRB240 Collaborator

BlueRB240

Posted
Posted
BlueRB24, great looking plenum...did you crunch any numbers with respect to runner lengths?

Nope thats not my car. But I have a manifold just like that. Getting parts like a intake manifold gasket is like finding gold. Takes a while to get those parts in. :D

HYBRID VL Community Regular

HYBRID VL

Posted
Posted

i was just asking i dont need to use the intake plenum i wanted to use the inlet manifold and fuel rail so i can easliy adapt GTR injectors as the Rb25 is Side feed RB20 is top feed thought it would be alot easier and less stuffing around if i i just changed intakes.

hmmm but if the Rb20 is smaller then i would lose performance so i guess its not worth it then.

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