Jump to content
SAU Community

Recommended Posts

  • Replies 48
  • Created
  • Last Reply

Top Posters In This Topic

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?

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 :(

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

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)?

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!!!

  Joel- said:
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

  Gaebril said:
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.

  White-R33 said:
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.

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.

  skylinegeoff said:
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??

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • I know why it happened and I’m embarrassed to say but I was testing the polarity of one of the led bulb to see which side was positive with a 12v battery and that’s when it decided to fry hoping I didn’t damage anything else
    • I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
×
×
  • Create New...