detonation issues standard RB25DET

[Kinkstaah]

Neo bottom end is what I'd be doing. Would save you having to reconvert the car back to a R33 setup by putting stock R33.
 

Finding a working neo bottom end though could be tricky.
I would be putting a neo in over a R33 RB25. It's a better engine and it's already setup and working in the car.

3L Bottom end can be done cheap. And usually everyone would recommend a "dirty 3L cheap" bottom end but if your goal is 250kw or less, well, it'd be really right up your alley.

[GTSBoy]

The only concern I would have with using his existing Neo head is whether it has suffered from detonation and will cost $ to get ready again.

[Kinkstaah]

Definitely a valid concern, though I'd still want to put a full Neo back in in that case.

It's minor, but may as well do that as the 'conversion' has already taken place, and its considered a better motor, if only slightly.

[mikel]

32 minutes ago, Kinkstaah said:

Neo bottom end is what I'd be doing. Would save you having to reconvert the car back to a R33 setup by putting stock R33.
 

 

what conversion would have been done to get the Neo head on in the first place that needs converting back?

It all looks like an R33 RB25, including the CAS

[WMDC35]

The NEO cam doesn't have the right drive for the early alloy type R33 CAS? If it's got the alloy CAS it's not a NEO head or someone has put a 26 EX cam in it which would be unlikely.

If it's a late S2 plastic type forget the top line.

They would've just swapped the intake for everything else.

[GTSBoy]

Yuh, Neo head swap into later R33 would have been very easy.  And even if the CAS is not compatible, repinning the CAS plug is 5 minutes of work.

[mikel]

a 2nd hand NEO motor is not much more expensive than an R33 RB25, so I could go with either....but does that complicate the changeover significantly?

Will my Apexi Power FC  work? are the wiring looms different? I don't want to complicate things too much

Mike

 

 

[Kinkstaah]

The thing is, all the injectors, afm, wiring, tune, etc will be setup for the neo head. (or at least they should be). The bottom end is "dumb" in that aspect.

Which is why I was saying keep the neo as it'd be simpler. I am not entirely sure what exactly is required, or what exactly was done, considering your actual swap was uh, done badly by someone in the past. May not be possible to know what is right and what is wrong!

Assuming the only issue is the comp ratio, and eveyrthing "Neo" was setup and running fine I would put a Neo in.
GTSBoy has a Neo in his R32, he knows things.

[GTSBoy]

My thoughts are that;

• The Neo head could have been put onto the engine using everything R33 that mattered, being intake manifold & injectors.  That would permit the existing injectors and injector loom to be used.  The coils are different between Neo and vanilla.....but I'm sure that it wouldn't take too much effort for someone to bodge a coil loom to work.  The CAS is either the same, or at worst only requires re-pinning (for an older vanilla 25).  All else should not present a problem.
• Hence, putting a complete Neo into the R33 may actually entail changes that may need to be done.  New manifold and injectors would require loom changing.....well, at worst, you could keep the old vanilla manifold again.  Not as nice as Neo, but still works.  All the other ancillaries (alternator, AC compressor, etc) that have wiring differences on Neo to older RBs can be kept over from the R33 engine, so not a problem.
• A proper Neo has a boost sensor (for the ECU) at the back of the head.  Not required and easily ignored by the PowerFC.
• Um...charcoal canister/vacuum switching stuff is likely a bit different between them.  But I'm not sure.

I installed the Neo in place of an R32's RB20.  So not same-same as this work.  Differences between R32 and R34 are far wider than S2 R33 and R34.  So I used the R34 engine bay loom and changed the wiring out on the ends of it where it touched the car (other than the engine).  Like PS reservoir switch, fans, that sort of thing.  And hence use R34 ECU (with Nistune to get around a few incompatibilities, like ABS/TCS absence).  Air con enabling was a major pain in the arse for Neo into R32.

If it were me, I would not fear putting a complete Neo into the R33.  There will be a couple of challenges, but they're not going to stump anyone for too long.  And taking the easy way out with the inlet manifold swap would make half of those go away!

 

[Dose Pipe Sutututu]

swap entire plenum from R33 onto the NEO.. then swap pins on the CAS

In terms of coils, you could use the R33 harness on the NEO head but the wiring will be messy using the NEO coils.. however if you use the NEO coil packs and NEO coil pack harness it plugs straight intot eh R33 loom

NEO coils and NEO harness are essentially and schematically the same shit.. just the mounting tabs are different and the NEO are all aligned in 1x direction where as the R33 RB25 is all over the shop like a hooker on meth, thus the coil pack harness/loom (whatever you call it) have different length leads.

[Scott Black]

I don't think its going to be really worthwhile to do a leakdown test, especially if its a couple of hundred to do it. Multiple cylinder variations after a fair amount of det suggests bottom end issues, expecially with rb25 ring lands as sensitive as they are.If you get a local motor then you want comp/leakdown test. Pull oil cap off/ and see if it looks sludgy in it or any signs of rust on the can u can see. 

Things I'd change personally, timing belt, water pump,thermostat, cam seals. Front main seal. Rear main seal, rocker covers,  and reseal the sump. Its a fair bit to do, yet gives you or your mechanic a good chance to really inspect everything and you have then sealed everything that can leak on it.

[discopotato03]

I agree Neo 25T far better engine and using as much of it as possible is way to go .

My understanding is that the only significant bottom end difference R33 to R34 RB25DET is the pistons and rods . Pistons crowns are lower to keep the same 9:1 static compression ratio and the gudgeon pin size is the larger 26 spec to suit 26 rods . If you decide to rebuild then Neo rods and pistons = Neo bottom end . 

Recently I've been looking at 33 and Neo inlet manifolds mainly concerning plumbing differences .

Idle air control and "auxiliary air control" (cold start bypass valve) are completely different with the Neo , simpler because it has hot water plumbed into it rather than the clumsy R33 air valve plumbed underneath . Also the IAC assembly has an air bleeder on it and the manifolds cast in water log has a riser pipe up to it . I'd loose the Neo throttle body and keep the 33s one and its TPS . Neo's appear to have another air bleeder in front of the cast water log with another riser hose up from the thermostat areas pressed in block fitting .

Long short Neo inlet manifold has better IAC system and takes better top feed injectors . Manifold runners are supposed to be slightly smaller bore and it looks like the plenum volume may be slightly less than R33 . With the same external mods Neo's always seem to make a bit more power than 33 spec 25DETs .  

I could be wrong but I'm pretty sure I ordered a Neo coil harness new from Nissan or Kudos and it plugged strait into my R33 .

A .

Edited August 25, 2017 by discopotato03

[mikel]

thanks @Kinkstaah, @GTSBoy, @Dose Pipe Sutututu, @Scott Black, @discopotato03, for your detailed responses...

clearly there's been some level of modifications done (by tuner #1 that put the head on) just to get the bloody NEO head working in the first place, so I'm in a bit of "unknown" place as to what they did - injectors and coil packs weren't changed that I'm aware of.

On 8/24/2017 at 4:40 PM, GTSBoy said:

My thoughts are that;

• The Neo head could have been put onto the engine using everything R33 that mattered, being intake manifold & injectors.  That would permit the existing injectors and injector loom to be used.  The coils are different between Neo and vanilla.....but I'm sure that it wouldn't take too much effort for someone to bodge a coil loom to work.  The CAS is either the same, or at worst only requires re-pinning (for an older vanilla 25).  All else should not present a problem.

 

I just went and checked, the CAS is a NEO CAS - apologies for previous incorrect information.

Tuner #2 (my ex current tuner) mentioned that the intake manifold was different on a NEO compared to an R33 RB25, so on a 2nd hand R33 RB25 they would use the "bottom half" (ie intake manifold below the crossover pipe) from the 2nd hand engine if installing an R33 RB25 - so the current intake manifold "may" be NEO, but it sounds like that would have required injector changes?

On 8/24/2017 at 4:40 PM, GTSBoy said:

The coils are different between Neo and vanilla.....but I'm sure that it wouldn't take too much effort for someone to bodge a coil loom to work.  

So who knows where I am on the "in between R33 RB25 and NEO" situation??

I really appreciate your input guys - I just wish I'd sought it when tuner #1 recommended a NEO head !!

Given where I'm at it sounds like the best option is:

• find a tuner/mechanic that has the ability to deal with the "in betweenness" of a NEO onto a R33
• source a 2nd hand NEO engine and do a compression test/leakdown test prior to purchase (I'm not sure how feasible this is?)
• on the 2nd hand NEO, replace water pump, cam belt and other items @GTSBoy and @Scott Black suggested
• have the tuner/mechanic manage issues with looms, but use a NEO Coil Pack and Harness which should plug straight into the R33 loom

When I look on the interweb for a locally available NEO motor such as this:

https://www.asianautospares.com.au/collections/new-used-nissan-engines-japanese-imported-engines/products/nissan-rb25det-engine-neo-japanese-imported-engines

Are there other "bits" I should be sourcing/ensure comes with the motor to make it easy to put a NEO 2nd hand engine into my R33? (eg coil packs/harness, inlet manifold, injectors)?

Are there specific variants of a NEO motor I should seek or avoid - eg R34GTT vs Stagea etc?

cheers

Mike

[GTSBoy]

You can take out a coil, get the part number off it and we will be able to tell you if it's vanilla or Neo.  Likewise the inlet manifold and the injectors.

Any Neo gets you the goodness you really need, which is the head and pistons/rods.  There are apparently some halfway house Neos from Stageas that are part R33 era and part Neo.  They have a weird mix of stuff on them.  Probably best avoided.  But otherwise, even a 4WD Neo from a Stagea is useful.  You can do swappsies with sumps and stuff with what you already have.  Stageas do NOT have traction control, so you actually get a better TB with them

By far, the best thing you can do if you're doing a Neo swap is get the ECU with it and get it Nistuned.  That will of course add some $$, but you will end up with a half-n-half mongrel if you re-use the PowerFC.  And besides which, you can sell off the PFC to offset the expense.

[mikel]

8 minutes ago, GTSBoy said:

You can take out a coil, get the part number off it and we will be able to tell you if it's vanilla or Neo.  Likewise the inlet manifold and the injectors.

Thanks GTSBoy,

Are any of those possible without taking too many bits off?

Happy to do it - just never done it - the last car I mucked with the engine had spark plug leads, a dizzy and a holly carby...

1 hour ago, GTSBoy said:

By far, the best thing you can do if you're doing a Neo swap is get the ECU with it and get it Nistuned.  That will of course add some $$, but you will end up with a half-n-half mongrel if you re-use the PowerFC.  And besides which, you can sell off the PFC to offset the expense.

We're entering a new area here - my car came with the Apexi PFC from Japan, so I've no idea what a Nistune is, but I assume it's a mod on the factory ECU??

I'll need to do some research as to where/who can do the mod - but in your opinion that's better than staying with the Apexi PFC?

...part of me thinks going back to a 2nd hand R33 RB25 is a good idea - except I'm currently "in between" and there is likely an additional cost in going back to an R33 RB25 if I source a 2nd hand R33 RB25, so I may as well go forward to a NEO, if the costs are "close" fully installed.

If I'm seeking a NEO with ECU, I'm clearly sourcing something different from a NEO motor - when I ring engine providers, what am I asking for? A NEO with wiring harness and ECU?

cheers

Mike

[GTSBoy]

Coils out is easy.  Just remove the intake crossover pipe, coil cover and unbolt a coil from the bracket.  You'll see.

You could use the PowerFC.  It is broadly equivalent to the Nissan ECU.  It's just that the Neo is a more modern engine than the vanilla 25 and has a couple of tricks, most of which are in the ECU.  You will have no trouble finding someone in Brisbane who can fit the board to the ECU and set it up.  You won't even need to tune it, because the base map is the correct map for a stock Neo anyway.  Although as you will have a tuneable ECU you should take advantage of the free power and fuel economy available from pissing off the stock on-boost richness and massive ignition retard.  Plus wind the boost up to 12 psi of course.

The other thing about Nistune, especially nowadays, is that there has been a lot of dev work put in and the feature pack added to it allows flex fuel and various other goodies, which you can't do with PFC.

So, yes. To buy an engine with ECU and loom is just a case of asking for ECU & loom.  And if you have a manual car, it doesn't matter if you get an auto or manual ECU.

[Ben C34]

Take a photo of the exhaust side of the head, near the front.

The neo head doesn't have an oil drain that exists on pre neo heads

[Scott Black]

Basically you can use a neo head in an r33 by reusing the r33 manifolds and blocking an oil drain on the side. Then you need to Change a pin on the vct solinoid and Repin the CAs. It will all work with the stock Nissan ecu except for the problems with the higher comp, so if you got a neo long motor provided your already using the neo cas( if its a neo head then it needs to use the neo CAs) then just swap all your bolt on assesories to the neo and done. 

[mikel]

On 8/26/2017 at 9:30 AM, Ben C34 said:

Take a photo of the exhaust side of the head, near the front.

The neo head doesn't have an oil drain that exists on pre neo heads

Thanks Ben,

I'm now confident it's a NEO head since checking the CAS (I have a NEO CAS) - now I just need to check coil packs and injectors to see what's still R33 vs NEO to determine the "in betweenness" between R33 and NEO

23 hours ago, Scott Black said:

Basically you can use a neo head in an r33 by reusing the r33 manifolds and blocking an oil drain on the side. Then you need to Change a pin on the vct solinoid and Repin the CAs. It will all work with the stock Nissan ecu except for the problems with the higher comp, so if you got a neo long motor provided your already using the neo cas( if its a neo head then it needs to use the neo CAs) then just swap all your bolt on assesories to the neo and done. 

Thanks Scott,

...at the point now deciding whether to put a 2nd hand R33 RB25 or 2nd hand NEO in.

A NEO long motor (if I could source one) with my current NEO head is a risk as I have no idea how good my NEO head is (give the detonation issues), or the condition of any NEO long motor I sourced.

My preferred option is to install a 2nd hand motor, either R33 RB25 or NEO. 

Guidance from SAU is to install a 2nd hand NEO rather than an R33 RB25 - stronger motor, and I'm halfway there already with my current NEO head...

I still have decisions whether I keep the Apexi PFC or go to a Nistune - Nistune sounds like the go - I just need to source the NEO plus ECU/harness, and find an installer that understands the intricacies of a NEO into an R33 - gotchas like the air con control difference.

cheers

Mike

 

 

[Dose Pipe Sutututu]

Alternatively if you're on a budget and your bores are still good, your crank is still in good shape I just find a used set of NEO pistons/rods/bearings.

I have a set of 6x NEO Pistons/Rods/Bearings from a 120xxx automatic Stagea up for sale if you're interested? This will compliment your NEO head and budget.