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Difference between RB25DE and RB25DET

HKS34R

By HKS34R,
in Engines & Forced Induction

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Gaebril Newbie

Gaebril

Posted
Posted

perhaps experienced people who has access to these things (sydneykid?) could clear these questions up for us?

a head would be a much easier and cheaper thing to replace than pistons and rods for me.. plus i could probably replace the cams at the same time...... hmm....

maybe I would take a trip down to the traders and ask their sales to let me take a peek at their catalogue? any chance of that happening?

666DAN Grand Master

666DAN

Posted
Posted

Viscount: I'm running about 7-8psi...no boost gauge at the moment...just going by the standard pressure allowed by the factory solenoid. Compression is 10:1.

I wouldn't go replacing the head...as the NEO one is the decent, better designed flowing head...unless you buy a NEO turbo head that is. If you're worried about compression just get aftermarket forgies and bring it down to 9:1 if you like....personally I'm happy with my car spooling up at low RPM though :(

Simonster Proficient

Simonster

Posted
Posted

Hi guys,

I can shed a little light on this subject....

I bought a RB25DE and have turbo charged it.

Yes the standard valve springs of the DE motor are not as strong as the DET- i replaced mine with Tomei items.

Internally, only the pistons and rods are different- i replaced with forged items. I wouldn't want to run much boost with the standard set up, it doesn't inspire confidence after you've seen it.

Crank is the same.

There are different 2 inlet/exhaust port designs. Seen some DET models with both- quite a difference between the two in size- mine has the larger ports, which I've lightly ported as well.

I must also add that I've done quite a bit of work mine, built to support 550hp all day.

Hope that helps

Cubes Grand Master

Cubes

Posted
Posted

Pics would be nice? :)

The only difference size in ports i've seen is the inletports for the R33 RB25 head appears to be slightly larger than the inlet ports of the R32 RB25 head.

The exhaust ports I've seen are all the same.

With regards to the DE valve springs being softer did you find out the hard way via valve bounce around 5500-6500rpm with higher boost (15+psi)?

666DAN Grand Master

666DAN

Posted
Posted

That may be the problem though finding a DET head for 1K......forgies won't cost 3-4K either.

At the moment though I have seen an RB25DET Neo cdown the coast for 4K...that's very cheap for one!!! And a few weeks ago on the NZ forums someone sold a complete engine g/box, computer intercooler for 3K NZD....I was spewing I didn't get to see that!!!

Simonster Proficient

Simonster

Posted
Posted
Pics would be nice? :rant:

 

The only difference size in ports i've seen is the inletports for the R33 RB25 head appears to be slightly larger than the inlet ports of the R32 RB25 head.

 

The exhaust ports I've seen are all the same.

 

With regards to the DE valve springs being softer did you find out the hard way via valve bounce around 5500-6500rpm with higher boost (15+psi)?

Joel,

No, an engine builder I know gave me the heads up, so I changed them during a full rebuild. Complete engine cost me $1200

Will get you some pictures of the ports tonight. How do I post them?

I used Arias forged which I machined down to for a compressionh of 8.5:1. Also there are 2 different sets of rods in the RB25. One set has a little lump onm one side close to the crank- these are the weeker set, and another that look a lot stronger in build- similar to GTR rods. I shotpeend linshed and balanced them. Alomost as good as i beams but cheaper and just as good for the hp and 1.5 bar boost

Simonster Proficient

Simonster

Posted
Posted
Simonster, could you please tell me how much those Arias forgies set you back by?

I paid $1200. I had them machined to achieve 8.5:1 as I'm running 1.5 bar.

IMO they are virtually identical to JE and just as good a quality. Again, my friend that builds a lot of tough engines was very happy with the build quality and they are a little cheaper than JE.

Simonster Proficient

Simonster

Posted
Posted
as far as rods go....

What are people's opinions on billet rods? Are they worth the 1400... or would it make more sense to use GTR rods.. (rb25det bulid up)

I'm deceided on using arias pistons.... just moving onto the next decision !

thanks !

matt

Matt,

Depends on what your are trying to achieve with the car/engine. If you have decided on forged pistons, then really you are running more boost than stock and have decided to give yourself some more headroom with detonation. If that's not the case, why are you buying them? Forged pistons will add nothing to the performance of the engine by themselves. IMO at the very least I"d find a good set of RB25 rods- shotpeen linish and balance them( as I have), or just go for a set of ibeams. The latter is more expensive obviously.

GTRgeoff Grand Master

GTRgeoff

Posted
Posted

Just to add to the debate (Hi there Si, Hows life at ambs going) I recently rebuilt with Arias forged ($1300 delivered o/nite from Rocket industries) and GTR rods ($300 2nd hand) and had the lot machined balanced o ringed etc etc for $1200.

The standard R33 RB25DET pistons are an absolute piece of crap and will crack at the first sign of bad fuel on a hot day with inaudible detonation. I would hope Neo's are better but don't bet on it.

The GTR rods have added an element of smoothness that was not apparent before. They weigh more but I had other areas lightened to compensate. I have been assessing the structural capabilities and feel justified that you would be exceeding 350rwkw and 8500 rpm before needing to even linish or shotpeen, let alone upgrade to I beams or anything exotic. I also get no slappiness when cold from the Arias forgies which can happen with other brands. They are also a lot lighter than the standard pistons which helps with higher rpm (I have built for a possible 8500 but limit to 8000 on track and 7500 on road).

With the number of GTR rods available on the forum, and $300 being a good price to pay, don't waste effort on the RB25's rod at all. the cost of peening etc is too much.

Joel. What is the other rod? It can't be RB25DET as they are the same length as RB26DETT. Is it from an NA engine? Also the big end construction is not RB25DET as they are very similar to RB26DETT but less beefy and same shape machining on the sides where the index mark is.

Last note, Clevite and ACL (heat treated race) bearings for RB30 main and SR20 big end are an ideal fit when getting the machining done.

Simonster Proficient

Simonster

Posted
Posted
Just to add to the debate (Hi there Si, Hows life at ambs going) I recently rebuilt with Arias forged ($1300 delivered o/nite from Rocket industries) and GTR rods ($300 2nd hand) and had the lot machined balanced o ringed etc etc for $1200.

 

The standard R33 RB25DET pistons are an absolute piece of crap and will crack at the first sign of bad fuel on a hot day with inaudible detonation. I would hope Neo's are better but don't bet on it.

 

The GTR rods have added an element of smoothness that was not apparent before. They weigh more but I had other areas lightened to compensate. I have been assessing the structural capabilities and feel justified that you would be exceeding 350rwkw and 8500 rpm before needing to even linish or shotpeen, let alone upgrade to I beams or anything exotic. I also get no slappiness when cold from the Arias forgies which can happen with other brands. They are also a lot lighter than the standard pistons which helps with higher rpm (I have built for a possible 8500 but limit to 8000 on track and 7500 on road).

 

With the number of GTR rods available on the forum, and $300 being a good price to pay, don't waste effort on the RB25's rod at all. the cost of peening etc is too much.

 

Joel. What is the other rod? It can't be RB25DET as they are the same length as RB26DETT. Is it from an NA engine? Also the big end construction is not RB25DET as they are very similar to RB26DETT but less beefy and same shape machining on the sides where the index mark is.

 

Last note, Clevite and ACL (heat treated race) bearings for RB30 main and SR20 big end are an ideal fit when getting the machining done.

Hi Skylinegeoff!

Living in Perth now for 3 weeks. New engine should have it's first tune hopefully in around 2 weeks. Been drama's with the Autronic. Will send you as pm with a few photo's. Car still in Brisbane

I used rods that were identicle to GTR rods which i shotpeen and linished and balanced. Did that cause they cost me nothing, also wanted to make absolutely sure that I wouldn't have an internal failure. ( of course that also comes down to tuning) I used SR20 ARP rod bolts as they are a straight fit. I also sued Japanese racing bearings throughout- forgotten brand name

A mate who has a tuning shop on bris northside is entering it in horsepower shootout at Brisbane Autosalon in August. Not expecting anything huge but should come in at a little over 400rwhp. Will just have to make sure that I can get the thing run-in before its final tune before Autosalon. Bit difficult to drive it when I'm in Perth! How's your car??

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