Jump to content
SAU Community

Recommended Posts

So what's the general feeling with the RB25Turbo on the RB20DET? Little laggier, doesnt come onto boost until 5,000RPM but is stronger up top? That's 2,000RPM later then the RB20Turbo - hardly seems worth it for more top end surge. 2,000RPM later seems alot for a slightly larger compressor. I would of expected it to come onto boost at about the 3,500-4,000 RPM mark at the latest?

  • Replies 47
  • Created
  • Last Reply

Top Posters In This Topic

i have 1 forsale.... look in sig, never been boosted over 10psi.....and this sounds like a good upgrade for a rb20... :)

if mine doesnt sell i will just keep it because there is nothing wrong with it...and i might be getting a 32 as a dori car... i will get pics of turbo asap....it is a s1 33.

So what's the general feeling with the RB25Turbo on the RB20DET? Little laggier, doesnt come onto boost until 5,000RPM but is stronger up top? That's 2,000RPM later then the RB20Turbo - hardly seems worth it for more top end surge. 2,000RPM later seems alot for a slightly larger compressor. I would of expected it to come onto boost at about the 3,500-4,000 RPM mark at the latest?

It is'nt that late,there is a little lag and it's hard to say when 12psi is made coz the tacko don't work!Think of it this way,it does'nt drop off boost at all and the 500rpm or so that it does come on song I reckon is worth the $350 or so dollars for a RB25 turbs.

Going from old RB20 turbs to RB25NEO turbs:

- lag increased by around 800rpm so it feels a far bit slower around town

- 5500-7500rpm much less breathless then before

- extra airflow & psi = messed up AFR's from 4000-5000.

Most say a new fuel pump & chipped ECU would make it a lot nicer to drive...

Thanks for the reply guys. I didnt think the boost would come on so late and would be a harder kick in the back then the RB20 Compressor. So now the big question - where is the best place to source an RB25 Compressor in decent conidition? :D

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • Harness is for a s1 Rb25det, and it is engine and lower harness.  the old harness had broken off plugs and was in very rough condition/exposed wires and splices etc. it is not able to be put back on the car, I could visually inspect to see if they had rewired any pins on the ecu plug. The fuel pump definitly isn’t turning off it’s an external pump and very loud you can hear it. Will look at the other harness tonight, am also going to pull the fuel rail and watch the injectors spray, will update here with what I find. Pretty sure at this point it has to be something to do with injectors because car will fire up on starting fluid and cas is clicking the Injectors. Fuel pressure is steady 43psi 
    • Check the injectors flow evenly, and are actually flowing what you and the ECU think they should be flowing. If it's starting up on starter fluid, you have a fuel issue. Is it possible under cranking your fuel pump is turning off?   The harness you replaced, is that the whole engine harness? Do yourself a test, and drop the old harness on and plug it into the Z32 ECU. It's possible they've wired things different. From memory S1 to S2 is different in RB25 and you may have a wrong loom
    • I haven’t pulled the injectors to watch them spray yet but they are clicking from the cas and all of the spark plugs are wet with fuel. I’ve thought the cylinders were being flooded from the beginning and was hoping fuel pressure would fix it. Tonight I am going to pull the rail and watch the injectors spray. Don’t know how to test/diagnose if the plugs are firing in correct sequence but that should be a timing thing and as far as timing goes my car still has the half moon for the cas can only install it 1 way. And my mechanical timing is 100% correct I posted photos above. Confirmed with the balancer on and off. 
    • I checked spark on all cylinders and they all visually have spark with the plug pulled and grounded, but plug 1 is the only one that fouled. This was a running swap that blew up and was rebuilt by a machine shop, put a new wiring specialties harness and did all gaskets, studs, and bolts while it was out.  compression is 135-150 across all cylinders. Aside from that from my understanding with the z32 ecu and maf the car should start regardless. The wiring for TPS and the dual 02 sensor/ dual knock sensor stuff shouldn’t actually stop the car from starting or even running well, (just slightly rich)  they just give fault codes. Car supposedly is supposed to start as long as you have z32 afm and ecu with the nistune base map and that’s info coming from a well known and trusted tuner who does a lot with SR/RB (Rsenthalpy). After more trouble shooting today where I’m at right now is that the cas is sending signal to the injectors they click while spinning the rotor, Fuel pressure is now set at 43psi, all cylinders have good compression and all of the plugs looked great (just wet with fuel) except for cylinder 1 which was very black (cylinder 1 has 150psi compression). all of the coils generate spark if pulled out and grounded out on the head. On the fuel pump car just pops into the exhaust. On starting fluid car will fire off. Hard to tell if all cylinders are firing off but definitley a couple. sounds like all of them but it’s only for 3-5 seconds hard to tell. 
×
×
  • Create New...