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rb25DE NEO with DET NEO pistons? Conversion build.


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I am in the process of turbo charging my r34 with a DE neo engine and i was going to order forged cp DET Turbo NEO pistons.... my question is, is the DE neo and DET neo head the same? i dont want to make an expensive mistake if the clearances for the valves will touch the top of the pistons because the NA pistons have grooves in them for the valves not to touch and i wasnt sure if it was specifically designed for the DE/NA neo head. Thanks!

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Why do you want forged pistons? The de neo head ports  are going to limit power as they are tiny, forged pistons don’t make sense in this case

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Well its because i do not want to run the standard DE naturally aspirated high compression pistons with boost... i have been told that its a "hand grenade" and as such you will have to be between 7-8 psi to stop things from going *boom*. i am just trying to make a reliable build to last me with moderate power, nothing to crazy.

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1 hour ago, Dil-Dog said:

i am just trying to make a reliable build to last me with moderate power, nothing to crazy.

With a good ECU and good tuning you are going to make exactly that. Moderate power, nothing too crazy. With the high comp pistons. It's not as if they are HIGH COMP. The compression ratio is still sensible enough for decent boost.

I wouldn't change the pistons for this build.

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Yeah i definitely agree with you bro and also... thanks for the reply i really appreciate this community thus far helping a noob out like me. however i feel that it is an investment that is worth it for peace of mind and reliability but really my question is, is it compatible with NEO det pistons? 

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23 minutes ago, Dil-Dog said:

Yeah i definitely agree with you bro and also... thanks for the reply i really appreciate this community thus far helping a noob out like me. however i feel that it is an investment that is worth it for peace of mind and reliability but really my question is, is it compatible with NEO det pistons? 

Well, if you're going to go down that path - given that the cam profiles are barely different between turbo and NA, and given that the turbo pistons give more combustion chamber, there should be more clearance. And if there is not, a trial fit up will tell you whether you need to mill a couple of spots on the pistons.

I would bet $500 that there will be no issues.

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haha! okay bro i am gunna hold you to that bet! ?i feel like i am planning to do somthing that hasnt been done before. but yes i BELIEVE it shouldnt have clearance issues.

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56 minutes ago, zoidbergmerc said:

Yeah they'll fit...
 

You'd be better off getting a turbo motor though, cylinder heads are much better.

Or if you want to cheap out, just run a NA neo on ethanol and run all the boost!

Hey bro, thanks for the confirmation. the real story is... i bought a "neo DET" to replace my NEO de naturally aspirated but i basically got scammed once the engine was delivered to me because it wasnt actually NEO but rather a late series 2 possibly a series 3 that has the plastic hitachi CAS sensor and basically now i am swapping over all the parts. kind of a frankenstien build really. 

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Oh, I just realised something.......the Neo DET used RB26 rods. There is therefore a difference in the height from the pin up to the piston crown on the Neo DET pistons compared to other 25s. Not the same as vanilla RB25. I have no specific knowledge of the Neo NA....but I would not expect that they used the 26 rods in it. So, if your plan is to put pistons that you order to suit a Neo turbo onto rods from either the vanilla 25 or Neo NA....I would expect them to not work.

More research required, and potentially you will be better off ordering pistons and rods, or some other piston.

 

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4 hours ago, Dil-Dog said:

Hey bro, thanks for the confirmation. the real story is... i bought a "neo DET" to replace my NEO de naturally aspirated but i basically got scammed once the engine was delivered to me because it wasnt actually NEO but rather a late series 2 possibly a series 3 that has the plastic hitachi CAS sensor and basically now i am swapping over all the parts. kind of a frankenstien build really. 

If you have an RB25DET just use that. It will be better than a boosted Neo DE.

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@GTSBoy wow bro thanks for that insight, i didnt even think of that! what i will do now is pull the pistons form th de neo and the series 2, take pictures and measurements of them side by side and post them here soon.

@KiwiRS4T i was actually planning to do that after i realized i was scammed how ever the engine's wiring harness and ecu harness will not match the R34's due to the fact that the r34 is only compatible with NEO's

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@GTSBoy okay so i been doing research on RB connecting rods and from i have been hearing people say in the forums is that they are the same with the overall height of 121.5mm  AND  from what you can buy online, all the aftermarket brands of connecting rods mention that they are both compatible for 25 and rb26. so that would mean that the difference in Compression and Valve clearance between neo's series 2's and rb26's  must not be from the Rod height but rather the smaller NEO head's dome cc and Pistons. .... what do you think bro?

Edited by Dil-Dog
spelling mistakes and missing words
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Oh, the compression difference is wholey and soley because of the different (flatter) combustion chamber shape in the Neo (and therefore different crown shape to keep approx the same compression ratio).

But I may have just painted myself as an idiot. I still actually thought that the rod length was different, not that the 2mm stroke difference was in the pin height in the pistons.

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Ive just assembled a grenade so to speak, rb25de neo.

From what i could see,

De neo oil pump has shorter relief valve springs by about 10mm but rest of the pump looks the same as det neo.

De neo rods look to be the same as hydro 25.

De neo pistons have a slightly longer skirt and a little extra volume in the dome but pin height is the same as det neo.

De neo block has no oil squirters, oil feed and return has to be drilled.

De neo cylinder head uses same size valves and lifters as det neo, exhaust ports look to be same size, inlet can be ported out to det size  behind the valves and up the divider however where the intake manifold bolts on will get fairly thin in places and wont match 100% without welding and grinding, but does still fit nice enough for a low buck build.

I used det oil pump springs, gtr rods, arp head studs, supertech valve springs, tomei type b poncams, standard rings measured .014" top .018" second so back in they went.

Probably limit boost to 2 bar and see how she goes

 

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On 01.08.2019 at 03:02, Dil-Dog said:

Я нахожусь в процессе турбонаддува моего r34 с двигателем DE neo, и я собирался заказать кованые поршни cp DET Turbo NEO .... мой вопрос, одинаковые ли головки DE neo и DET neo? я не хочу совершать дорогостоящую ошибку, если зазоры для клапанов будут касаться верхней части поршней, потому что поршни NA имеют углубления в них, чтобы клапаны не касались, и я не был уверен, было ли это специально разработано для DE / NA neo голова. Спасибо!

buddy, why are you doing this, from an atmospheric engine to a turbo, if the Japanese have long come up with everything for you and you can immediately put a turbo engine
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12 hours ago, NEO25T said:

Ive just assembled a grenade so to speak, rb25de neo.

From what i could see,

De neo oil pump has shorter relief valve springs by about 10mm but rest of the pump looks the same as det neo.

De neo rods look to be the same as hydro 25.

De neo pistons have a slightly longer skirt and a little extra volume in the dome but pin height is the same as det neo.

De neo block has no oil squirters, oil feed and return has to be drilled.

De neo cylinder head uses same size valves and lifters as det neo, exhaust ports look to be same size, inlet can be ported out to det size  behind the valves and up the divider however where the intake manifold bolts on will get fairly thin in places and wont match 100% without welding and grinding, but does still fit nice enough for a low buck build.

I used det oil pump springs, gtr rods, arp head studs, supertech valve springs, tomei type b poncams, standard rings measured .014" top .018" second so back in they went.

Probably limit boost to 2 bar and see how she goes

 

 @NEO25T Hey bro thanks for the reply, its nice to see someone else has gone through the same journey i am doing right now,

so .... what you are saying is that the DE neo pistons are larger/taller than the DET neo pistons and that is what makes up the difference is compression ratios between DET and DE neo's? I am still very keen on using CP forged DET NEO pistons, but before i order i must be 100% certain that i wouldnt run into any valve clearance issues with the DE neo Head. but from what i am hearing and reading, they are the same dome size only the intake ports are smaller and shouldnt have issues hopefully.

Lastly, for your build, what intake plenum did you use? a series 2 r33 det, or r34 det neo, or the DE neo "y" intake that it came with? Thanks alot 

Edited by Dil-Dog
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