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Whats The Diffrence

R TUNE

By R TUNE,
in Engines & Forced Induction

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R TUNE Mentor

R TUNE

Posted
Posted

hey im looking at doing a twin cam convertion to my RB30e

i just wona know besides ecu whats the diffrence between a RB25DE and RB25DET (minus the VVT)

cause one of my friends has a 33 with a 25DET and is going to put in a RB26DETT so i was gona see i can get the eng of him and put it on mine. i know the comp will be lower and ill be getting forgys any way when i do the build.

im stick to na this is why im asking about the DET head

chears brentt

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unarmed_skyline Experienced

unarmed_skyline

Posted
Posted

the head set-ups are different, they have different pistons, valve springs, cams, injectors fuel regulators, other than that not much, pretty much if you are going to up-grade the head in any way it wouldnt matter if you went with a turbo or na head but people always go with the na head cause i ends up with a higher compression ratio i think mainly cause of the pistons, and you wouldnt need forgies if you were building up a stock rb30de you could just use the 25de pistons and get 10.5-11ish:1 comp ratio, biggest prob is high comp forged na pistons are hard to find

skyla Community Regular

skyla

Posted
Posted

I'm going to disagree with the above post, there isn't any difference in the R33 RB25DE/T head it's self, they are the same has the same cams, lifters and valve springs (according to the R33 engine manual), how ever the above post is correct in saying the injectors and pistons are different.

Using The RB25DE pistons in a RB30DE will give you a compression ratio of 10.4:1 - 10.5:1

If using a R33 head you don't have to keep it vct, all you need to do is remove the R33 VCT cam and replace it with the intake cam and cam wheel from a R32 RB20DET, the cam specs for the RB20DET are 240 duration with 7.8mm lift. Simple bolt in job and no more vct.

Eug Grand Master

Eug

Posted
Posted

correct, the injectors and pistons are different.

and it would be difficult to get 11:1 ration without some block/head decking and thin gasket.

high comp forged na pistons shouldnt be too hard, i have read somewhere that the VG30(?) pistons should fit - look into bore, stroke and other specs of other available nissans. you'd be surprised.

R TUNE Mentor

R TUNE

Posted
  • Author
Posted

thanks guys, witht the build i was going to use a motec m800 ecu (when i get the money) and also potenterly put nos in to the build that was my reason for the forged pistons.

it is becomeing very hard to find a full rb25de head with loom and comp. thats why i was concidering the rb25det head and now i know i can get rid on vct i might use it.

thanks agan

brentt

  • 2 weeks later...
BADR33 Collaborator

BADR33

Posted
Posted

r33 head plus rb25de pistons =10.43:1 compression ratio.. if you deck the block 0.75mm you will get 12:1 compression.

if my engine needs a rebuild i will be going for 12:1 this time. just need to find out if i warped the crank or just broke the flywheel/clutch...

vvt is great. helps keep it nice and torquy.

25det injectors are a bouns. i have 25de and there running at about 80% duty cycle.

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