Rb25 Neo Into S2 R33 - Am I On The Right Track?

[Akshunhiro]

Hey all, just wondering if I could get some information/confirmation regarding this swap.

So, story goes... Had an RB25 in a 180, binned it, engine was low on compression, part-out.

Came across a mint S2 R33 rolling shell and still had most of my RB gear and since I didn't like S-Chassis' anymore I decided to put something together for the new shell.

Didn't want to stick with a standard 25, knew about the oil starvation/crank collar issue but couldn't afford to build one. Decided to just get an RB25 Neo AFTER doing some research on the swap but seriously, there's not much information out there.

I had PM'd a couple of people (very grateful for their responses!) and it seemed very simple using S2 R33 gear (loom & ECU) but now I am confused about the injectors.

Here's what I think I know, please correct me if I'm wrong.

Coil pack loom plugs straight in to S2 R33 loom

Injector loom plugs straight in to S2 R33 loom

Swap to S2 R33 throttle body and TPS

Rewire CAS, reverse pin order, same plug

Chop VCT solenoid plug off Neo loom to wire into S2 R33 loom since they're different

Chop IACV plug off Neo loom to wire into S2 R33 loom since they're different

Everything seems straight forward but after buying an auto R34 GT-T half-cut, I came across what I think is an injector resistor (P/N: A15-000J06). Here's where I get a headache.

It's my understanding that most modern cars these days run high impedance injectors and my search results have found that both R33 and R34 have high impedance injectors, resistor packs are only for low impedance injectors to ensure the injector is triggered without drawing a butt-load of current and frying the ECU.

I can't find any information regarding a resistor pack for the R33 so wondering if it's just a characteristic of the R34 and it's ECU?

Just to confirm, I'll be using a Z32 ECU which has been NIStuned and modded to suit S2 R33 RB25DET along with the S2 R33 engine loom. I decided this would be easier than trying to adapt the R34 loom and ECU into the S2 R33 body loom.

Also, with the injectors, I've seen conflicting info regarding size. I know S2 R33 are 370cc but are R34 GT-T 350cc or 370cc? I know they're top feed and they're TINY but just wondering if I need to make adjustments to the tune if they are in fact 350cc.

Appreciate any info on this subject, I look forward to getting the engine in and running! Currently waiting on parts to arrive to do the timing belt and water pump then it'll be in!

[BH_SLO32]

I found it easier to put the R33 manifold on the R34 engine. This will enable you to retain factory R33 injectors, throttle body/TPS and intake air piping. The thermostat housing on the R34 is smaller than the R33 so again I found it easier to swap the housing to retain the factory R33 water hoses. You are correct with the following:

Coil pack loom plugs straight in to S2 R33 loom

Chop VCT solenoid plug off Neo loom to wire into S2 R33 loom since they're different

CAS power and earth wires only need to be swapped. Check with the wiring diagrams.

Hope this helps.

Edited August 10, 2012 by BH_SLO32

[WMDC35]

  On 10/08/2012 at 2:36 AM, BH_SLO32 said:

I found it easier to put the R33 manifold on the R34 engine. This will enable you to retain factory R33 injectors, throttle body/TPS and intake air piping. The thermostat housing on the R34 is smaller than the R33 so again I found it easier to swap the housing to retain the factory R33 water hoses. You are correct with the following:

Coil pack loom plugs straight in to S2 R33 loom

Chop VCT solenoid plug off Neo loom to wire into S2 R33 loom since they're different

CAS power and earth wires only need to be swapped. Check with the wiring diagrams.

Hope this helps.

i'd run with this, just reverse cas wiring (mirror image)

[Akshunhiro]

Thanks for the input, Ben!

I too was recommended to run the 33 intake manifold but was reluctant since the ports don't quite match properly (plus I no longer had my 33 intake manifold and injectors). Going to just try the injectors as they are, showing about 12 Ohm's so definitely high impedance. If anything, just need to adjust the k value till it gets a full tune.

I still have the 33 thermostat housing so will run that too.

CAS makes sense since the outer two pins are 0 and 180, just simply swapping the inner two pins saves spinning it 180 degrees before refitting.

[GTSBoy]

R34 injectors are 380cc, 0.71ms latency

[BH_SLO32]

  On 10/08/2012 at 3:00 AM, WMDC35 said:

i'd run with this, just reverse cas wiring (mirror image)

Yes you are right, my bad, I just checked my wiring diagrams. Thanks for the correction

Edited August 10, 2012 by BH_SLO32

[Akshunhiro]

Good news everyone!

The Neo 33 lives.

All running well with Type 2 NISTune Z32 ECU, Z32 MAF, stock injectors, R33 TB & TPS, rewired VTC solenoid and AAC. Needed to tweak injector k value and latency given the different size and aftermarket fuel pump.

Ready for a road tune from Toshi!

[discopotato03]

Yes an interesting combination Neo GTt engine in a 33 GTST . I wished I'd known the 33/34GTt RB25 differences because I may have gone down that road myself . Out of curiosity what was different manifold/head port wise between the two ?

Also was the change to the later CAS a brand thing or are they more accurate ?

A .

[Akshunhiro]

I don't know the exact differences between the heads are far as porting but know that the Neo head flows more. Supposedly it's all on the intake side. Exhaust side is much the same.

Neo CAS had to be used because the keyway on the cams are different.

[WMDC35]

i've got a spare neo engine to replace my 33 one when/if it dies, i should be able to get a comparo pic up soon of intake ports, haven't heard of any more accuracy from the neo cas

[Steez]

I finishing off this conversion but have 1 slight problem. The spark plugs arent sparking and ive checked for power and signal and its all good.
Any suggestions on what the problem may be?

[Dose Pipe Sutututu]

if you take off the CAS and rotate it with your fingers do you hear the injectors fire?

[GTSBoy]

  On 05/09/2012 at 11:57 AM, discopotato03 said:

Yes an interesting combination Neo GTt engine in a 33 GTST . I wished I'd known the 33/34GTt RB25 differences because I may have gone down that road myself . Out of curiosity what was different manifold/head port wise between the two ?

Plenum is smaller. Intake runners are smaller, for higher velocity and hence better charge mixing/turbulence. Combustion chamber is completely different, much flatter shape and about 10cc less chamber volume. (Therefore pistons are different and they use RB26 rods). Cam followers are solid.

[discopotato03]

Intercharging R33 and R34GTt RB25 inlet manifolds needs its own thread

Starting that now , cheers A .

[Dose Pipe Sutututu]

  On 04/03/2013 at 12:01 AM, GTSBoy said:

Plenum is smaller. Intake runners are smaller, for higher velocity and hence better charge mixing/turbulence. Combustion chamber is completely different, much flatter shape and about 10cc less chamber volume. (Therefore pistons are different and they use RB26 rods). Cam followers are solid.

Not to mention good for 350kW without blowing piston ring lands and valve float, I'm contemplating in dropping in a NEO motor into my car before I go a tad silly with a new turbo. At the end of the day it will be cheaper over all dropping in a NEO motor then doing the mods, instead of doing the mods, blowing up the non-neo then rebuilding the non-neo.

Cost wise, doing motor swap upfront seems a good deal, using an older plenum on a newer motor doesn't make too much sense to me.

[gold-3lt]

Can you convert a series 2 r33 head from hydraulic lifter to solid using all the parts from a neo head?

Might be a stupid question but i'm just wondering because I have a neo head off an engine that blew up and it appears to have too much damage in the chamber and galleries to use.

I'm building a 330kw + rb25/30 and have 2 r33 heads that I can use but I would have rathered the neo head with the solid lifters.

If this is not possible what kind of power can i expect reliably from a standard series 2 rb25det head?

Edited March 6, 2013 by gold-3lt

[GTSBoy]

I think the only way to solid lifter an old head is with a kit (Tomei, and whoever else does them). I don't think the Neo stuff suits.

[AngryRB]

Can anyone confirm if the r33 CAS connector will fit the R34 CAS? 

[BundyBear]

  On 10/11/2016 at 6:03 AM, AngryRB said:

Can anyone confirm if the r33 CAS connector will fit the R34 CAS? 

Yes it will. Just did a neo conversion on my mates 33gtst. Plugs str8 in but u need to swap the wires for the neo...ie 1234 becomes 4321

[AngryRB]

Thats odd, cars at the tuners and apparently the r33 connector wont fit the r34 cas, unless there are different connectors but even on ebay and online stores all the connectors are referenced for 33, 34 silvia etc..