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What Exactly Are The Differences Between R33/r34 Rb25T Inlet Manifolds ?

discopotato03
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discopotato03 Grand Master

discopotato03

Posted
Posted

This gets talked about often so obviously people are interested to know if the complete RB25 inlet manifolds can be substituted from R33 25DET to R34 Neo Turbo and vice versa .

There are good reasons to attempt this ie R33 engine in R34 or the other way around . Obviously the injectors and throttlebodies/TPSs are different but if the whole assembly can be exchanged in some circumstances it could make life easier .

Anyway its been said that the Neo RB25DET has slightly smaller inlet ports and runners at the manifold flange . Most people think the Neos make better power than the R33s do even in modified form maybe the ports and manifold sizes were changed for good reasons . The way to check if the manifolds are interchangeable is to compare inlet manifold gaskets I suppose because that confirms stud holes water jackets and ports line up - or not .

I'm not sure of the wiring situation as in if the injector loom plugs are the same , I hear that the coil loom plugs are the same .

I believe the throttlebody mount on the plenums are the same so you can go either way .

The things I'm not sure about is air plumbing and the idle and cold start valves , wiring would be different here .

Anyway first things first will they bolt up to their opposite numbers head ?

A .

3Katz Collaborator

3Katz

Posted
Posted

I have wondered this my self and found very little solid information. I have a R33 Greddy plenum here and have some inlet and exhaust manifold gaskets on order from Nissan to suit a NEO, so as long as the Greddy manifolds are matched to the R33 head correcly we should get an answer. I'll post up results once the gaskets arrive.

WMDC35 Experienced

WMDC35

Posted
Posted

manifolds swap over, the electrics seem to work much the same, have run 25neo de with all its elecs off an r32 25de ecu(changing cas & coil wiring, & a few plugs), ran mint-not saying this is the preferable way but shows elecs can work together, with both motors in good condition power result for same mods should be very similar, i've got a neo to replace a s1 when it dies which i'll use the same setup (300+kw) for back to back

3Katz Collaborator

3Katz

Posted
Posted

Inlet manifold gaskets are the same part number 14035-75T01-.

Well that would have to solve the question as to whether the ports will match up. Didn't even think to check that way, nice one.

  • 2 years later...
AngryRB Grand Master

AngryRB

Posted
Posted (edited)

I was comparing R33 S2 and R34 neo today, is it normal for the Neo intake runners to be smaller diameter than the ports in the Neo head???, so therefore giving it a step/ slight mismatch?

The one with the blue on it is the R33 intake, looks like the area around the injector is different too, the R33 one is wider and more open..

post-70965-0-65386000-1433234176_thumb.jpg

post-70965-0-59763300-1433234213_thumb.jpg

post-70965-0-76680400-1433234248_thumb.jpg

Edited by AngryRB
JustinP Mentor

JustinP

Posted
Posted

The Neo intake manifold is narrower around the top / injector area, however on the head it is the full width of the gasket.

I was comparing R33 S2 and R34 neo today, is it normal for the Neo intake runners to be smaller diameter than the ports in the Neo head???, so therefore giving it a step/ slight mismatch?

The one with the blue on it is the R33 intake, looks like the area around the injector is different too, the R33 one is wider and more open..

  • 2 years later...
discopotato03 Grand Master

discopotato03

Posted
  • Author
Posted

I managed to get my hands on an almost bare and a complete Neo turbo inlet manifold to play with because I think its a better setup . I don't have an R33 to compare atm but I know someone that does . I want to measure the difference at the ports and where the plenum mounts on the lower section .

As we know the TBs and bolts interchange , one thing is the 33s TB gasket is steel where the 34s is paper . The 33 has a rubber gasket between the upper and lower section where the R34s is steel shim .

Something I need to find out is the ID of the coolant hose rising up from that fitting on the block behind the water pump , it connects to the Neos front bleeder section .

At a glance I think the R33 is ~ 8mm where the Neo could be 10mm . Its that hose which heads down next to the front rubber fuel hoses .

A .

AngryRB Grand Master

AngryRB

Posted
Posted (edited)

The r33 throttle body has to be modified as it is different as there a small vacuum channel/hole on the r33 that a neo throttle does not have.  The area where the injector sits is larger in the r33.

Edited by AngryRB
discopotato03 Grand Master

discopotato03

Posted
  • Author
Posted

Ah , I was going to ask the differences but thought I'd better search first . I'll have a look at my R33 soon to see what that vacuum hose goes to , I suspect the charcoal canister .

Yes I knew about the top of the manifold ports being different , the head ports are supposed to be the same in this area R33/R34 .

Cheers A .

lcxu105 Proficient

lcxu105

Posted
Posted

From memory when you split the manifold the location of the runners are in a different positions to the 33 manifold.  Thats why the plazmaman manifoldd are different from  33 non neo to 34 neo. 

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