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Rb20 To 25 Conversion Q's , Not The Usual Ones

toffy

By toffy,
in Engines & Forced Induction

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toffy Veteran

toffy

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ok so i've decided to keep my laurel and use it for a streeter for a while , atm it's running a rb20 with a hks 2530, gtr injectors , z32 , pfc and all the other supporting mods , not being happy with the off boost characteristics i decided to buy a rb25 to slap in the lil 20's place (being a daily driven car , on the street lag can get effing annoying) . Now, before i start pulling it apart, i want to get the complete setup organised so it gets put back together as quickly as possible, so heres a few questions i'd like y'all to give me some input on:

1.) is it possible to use the gtr injectors? , if not , high flowed std injectors?

2.) would the hks 2530 be too small for an rb25 , if so , do you have any other suggestions (keep in mind i'm not after any power figure , just good response/torque)

3.) is the ap engineering pfc adaptable to rb25? (i do have a z32 ecu laying about ready for a nistune board if not)

4.) would a forward facing plenum be worth the cost for this type of setup?

5.) exhaust manifolds , is there any advantage to aftermarket types for lower powered rb25?

6.) is it worth looking for a larger size throttle body?

if there's anything you think i may have missed , feel free to post up . thanks :) (please note: the reason i'm not aiming for big power is because i have a track car to do that with , which is why i'm kinda trying to convert this one as cheap as possible)

toffy Veteran

toffy

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ok so i've decided to keep my laurel and use it for a streeter for a while , atm it's running a rb20 with a hks 2530, gtr injectors , z32 , pfc and all the other supporting mods , not being happy with the off boost characteristics i decided to buy a rb25 to slap in the lil 20's place (being a daily driven car , on the street lag can get effing annoying) . Now, before i start pulling it apart, i want to get the complete setup organised so it gets put back together as quickly as possible, so heres a few questions i'd like y'all to give me some input on:

1.) is it possible to use the gtr injectors? , if not , high flowed std injectors?

2.) would the hks 2530 be too small for an rb25 , if so , do you have any other suggestions (keep in mind i'm not after any power figure , just good response/torque)

3.) is the ap engineering pfc adaptable to rb25? (i do have a z32 ecu laying about ready for a nistune board if not)

4.) would a forward facing plenum be worth the cost for this type of setup?

5.) exhaust manifolds , is there any advantage to aftermarket types for lower powered rb25?

6.) is it worth looking for a larger size throttle body?

if there's anything you think i may have missed , feel free to post up . thanks ;) (please note: the reason i'm not aiming for big power is because i have a track car to do that with , which is why i'm kinda trying to convert this one as cheap as possible)

ok , i spoke with my tuner today and got the answers i needed , incase someone searches for this i'll put up the answers:

1.) no , tightarse, sell them and buy s15(?) 480cc injectors

2.) .64 rear housing (i think it would be) = too small really , i'd be wheezy up top

3.) in short , yes

4.) not if your a tightarse

5.) not with the 2530

6.) i forgot to ask this question :D

DR 32R Rising Star

DR 32R

Posted
Posted

It seems if your going to the trouble of RB20 to RB 25, show a bit more "mongrel". After swapping a whole engine go for a better turbo and supporting systems, otherwise just hop up the RB20.

toffy Veteran

toffy

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i probably will , the only reason i origionally didn't want to is because i'm building another car with a rb25 t67 and supporting mods , my aim for this car was basically to make it a fun streeter so minimal lag is important :D , i can't think of a better turbo to use for that exact purpose, i'm open to suggestions!

JonnoHR31 Grand Master

JonnoHR31

Posted
Posted

put the 2530 on it and see how it goes. it will give great responce which is what your after. yer sure it'll have f**k all top end and wont make huge power but thats not what your after by the sounds of it. if you dont like it then you can easily remove it and upgrade to something bigger.

as for 6, leave the standard t/b on there with the standard plenum etc

toffy Veteran

toffy

Posted
  • Author
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Gt 30/71 or Gt30/76 a little madder and GT 35, or leave in the RB20

gt30 or 35 wouldn't give me the response i'm looking for :D , great turbo's but

put the 2530 on it and see how it goes. it will give great responce which is what your after. yer sure it'll have f**k all top end and wont make huge power but thats not what your after by the sounds of it. if you dont like it then you can easily remove it and upgrade to something bigger.

as for 6, leave the standard t/b on there with the standard plenum etc

yeah that seems like the go , i've searched round these forums a bit but haven't found the answers i'm looking for in reg to turbo sizing , i spend most of my time between 2500rpm and 5000rpm , the problem with the lil rb20 isn't the amount of power it makes but how long it takes to come on full boost (arond 4000rpm i think , pretty similar to my other car when it had a kkr430 strapped to its rb20) . It's my daily atm and i keep catching myself off boost when i really don't want to be, my last daily was a ba xr8 ute so i'm kinds used to large displacement engines too, i don't want/need any more than 200rwk really as i'd only get myself into trouble and a std 25 turbo is smaller afaik , what i'm hoping for is stock like response with a little more mid range :P

as for the tb , yeah , probably too much effort for little - if any gain :)

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