Turbo upgrade?

Was wondering what turbo would be the best to upgrade on an rb25det motor.. looking for a good street/track use turbo..

A lot would depend on your budget.

Apexi and HKS do great turbo upgrades. As does Trust and a few others.

A guy renting from me just put a GT25 turbo on his S13 and it has the largest exhaust houseing available.

on HKS maybe a single GT3240 or even a GT3037. Then again depends on how much lag and how much power you are looking for.

Give me a price range and a power figure your looking at and I can be a bit more specific.

Well, somewhere that stock rb25det internals could handle.. like 500ish rwhp.. and around a 2-3k budget...

You wont get that reliably with stock internals. And I doubt you will get that on that budget. You may but you would be hard pressed

You are going to need a T41B or a T08 single turbo. the factory compression ratio is too high for big boost so you will need to do the pistons, cams, exhaust manifold, external waste gate, fuel pump, front mount of at least 600 x 300 x 100, 720cc injectors, ecu, and port the head. Not to mention the exhaust and pod filter.

I hate to be the bearer of bad news but the RB25DET just wont reach that on stock internals or with much of the stock bits at all, and the ecu is another restrictor.

So what happened to everything I heard about the rb25 and rb26 stock block being able to handle upwards of 550 hp?

The blocks yes but the factory internals on a steady diet of it not. The RB26 will do it for a while then the ring lands will compress. The factory pistons are not as strong as people think they are, neither are the rod bolts. Remember the RB25DET block is NOT as strong as the RB26DETT block, nor is it going to handle the same power levels.
Also I have no idea what these items cost in the states either.

RB25DET

I did some new figures and here is what will give you what you want on a limited budget. The items with ( * ) are a must. I have put what they cost here in New Zealand but I would suspect you can get them cheaper in the states. Also halve the price for currency converting.

Fuel pump * ( Bosch motorsports $450)
Fuel pressure reg * ( Nismo $300 )
Front mount * ( Second hand 600x300x100 $1,000 )
720cc inject * ( Second hand $850 )
ECU * ( Second hand link $500 )
Pistons * ( JE forged $1,500 )
ARP bolts for the bottom end * ( $900 )
3 1/2" exhaust * ( Custom $900 )
Pod filter ( Apexi "best" $450 )
Turbo a Trust GT35 or equivelant ( New $3,000 )
Electronic boost controller ( New Profec B $800 )
External wastegate * ( Trial $1,100 )

Now if your lucky and paitent you may find good deals on the net in Japan and import the items yourself. Also again I am sure you can get items like JE pistons cheap there as we pay double duty plus mark up on them. Same with the fuel pumps and ARP rod and main bolts.

Originally posted by RazorGTR
The blocks yes but the factory internals on a steady diet of it not. The RB26 will do it for a while then the ring lands will compress. The factory pistons are not as strong as people think they are, neither are the rod bolts. Remember the RB25DET block is NOT as strong as the RB26DETT block, nor is it going to handle the same power levels.
Also I have no idea what these items cost in the states either.


First off, you make me laugh :D !!! Here's the deal....The RB25DET block isn't as strong as the RB26DETT ??? This I find funny because the 25 and 26 use exactly the same block. Even the RB30DET uses that block. The only difference between the 25 and 26 as far as those bottom end internals goes is the displacement. The 26 has a beefier crank and a longer stroke. The only reason the 26 can handle more stock is because it has a lower compression ratio than the 25 due to stroke. The 26 also has stronger valves and springs than the 25 which is why the 26 head is more sought after. Factory pistons will go over 20 psi.... that's pretty strong to me. I've even seen a GT-R hit 28 HP on stock pistons and internals.....

Night

Originally posted by NightXCZ77


First off, you make me laugh :D !!! Here's the deal....The RB25DET block isn't as strong as the RB26DETT ??? This I find funny because the 25 and 26 use exactly the same block. Even the RB30DET uses that block. The only difference between the 25 and 26 as far as those bottom end internals goes is the displacement. The 26 has a beefier crank and a longer stroke. The only reason the 26 can handle more stock is because it has a lower compression ratio than the 25 due to stroke. The 26 also has stronger valves and springs than the 25 which is why the 26 head is more sought after. Factory pistons will go over 20 psi.... that's pretty strong to me. I've even seen a GT-R hit 28 HP on stock pistons and internals.....

Night

Yes, they do use the same block, but the internals arn't as strong. Sure they could handle 20+psi, but for how long? And with what other things? (Fuel pump, fuel pressure reg, larger IC perhaps front mount.) I can't say exactialy what is different between the two, but I would take Razor's word for it. He has had a good deal of experience with GTRs and GTS-Ts, having owned both and been around quite a few quick ones.


(Not trying to flame either, just agreeing w/ Razor)

Originally posted by Gonthrax


Yes, they do use the same block, but the internals arn't as strong. Sure they could handle 20+psi, but for how long? And with what other things? (Fuel pump, fuel pressure reg, larger IC perhaps front mount.) I can't say exactialy what is different between the two, but I would take Razor's word for it. He has had a good deal of experience with GTRs and GTS-Ts, having owned both and been around quite a few quick ones.


(Not trying to flame either, just agreeing w/ Razor)

I'm not trying to flame, but you just agreed with me, not razor. Razor chose to say, and I quote, "Remember the RB25DET block is NOT as strong as the RB26DETT block, nor is it going to handle the same power levels."

You agreed with me, they use the same block which means that the RB25DET block is no weaker than the RB26DETT block, and that both blocks can handle the exact same power levels because they are the same block.....this is not judging by internals.

For 20 psi, you could run all day depending on how you tune your engine. I don't recommend it at all, but I know it's been done. I wouldn't run mine that high for an extended amount of time without building my engine first. Things that you would want to get to run 20 psi for short periods of time (such as drag races or street races) would be larger injectors, FMIC, boost controller, larger turbo, and a fuel pump.

Thanks for agreeing with me. It doesn't take owning cars to know about them, it takes working, dedication, and research on cars with a passion to become an expert. I am not yet an expert, but I am on my way of learning the RB motors forwards and backwards.

Night

First off they are two completely different blocks.

Second the bore is the same yes but as you have just said the stroke between the two is different you got that part right.

The craddles are completely different and not interchangeable. The dimension are different and so is the strength. You can not mount the gearbox out of a GTS4 or a GTR to the block of a GTS25t, while the R33 GTS4 block you can funny that.
so what does that tell you? the blocks are different in not only the back of the block but in the size and strengths of them. The R32 GTS4 block is different that of the R32 GTS-t block. The are heavier and much stronger. You don't get the flex out of them as you do in the 2wd blocks.

Now you mention 20psi on factory internals. Ok for how long? A steady diet of that and you WILL crush the ring lands. How do I know this? Well lets see. (4) R33 GTS25-t's have had that done already, and (3) GTR's already that I know of personally. I know the owners and I know the cars. They were tuned and other bits put on properly yet the same thing happended on all 7 motors.

Now you mention the RB30. Well that was used in the R30 and R31 skylines, and the VL comodore. They were single over head cam motors. The major difference there is the mounting for the trans has the same pattern as the GTR and GTS4. how do Iknow this? A tuning house by the name of Advanced Imports did a 3 litre conversion on an R32 GTS4 some years back. They put an RB25DET head on it. It was a nightmare from hell to do and as I read the article and talked to Peter Hopkins about it he says and I quote " never again. From the begining it posed many problems getting it to work right".

Another notable is the fact once you stroke the RB26 block to 2.7 or 2.8 litres #3 cylinder has a tendancy to crack. Again how would I know this? Well Crodyon Wholesalers R32 GTR has went through 3 count them 3 N1 blocks with the same failure. Reece Megreggor, current holder of the quickes 4wd car in Australasia has had it happen as well and his is not even stroked.

If the R25 block was so strong then why don't the Japanese use them instead of the more expensive or should I say much more expensive RB26 block? In the JGTC all he Skylines are 2wd and up until recently all used the RB26 block. They did not use the RB30 or RB25 blocks, and that was for a very good reason. Reliability and strength.

I am not taking anything away from the RB25 block as yes it can produce some good hp numbers. In fact I have heard of a few in Japan pushing 900hp, but they don't last long even with the right gear in them.

People need to get it out of their heads that all the RB blocks are the same in strength and durability. If they were Nissan would have not made the RB26 block as a seperate casting as they did. The would have merely incorparated the other blocks to fit as needed.

You don't have to beleive me. Contact these following companies and ask them for youself.

Lee Sutton @ Advanced Imports
http://www.advan.co.nz/

Nick Jenkins or Greame McDonnald @ Croydon Wholesalers
http://www.croydons.co.nz/

Sub Zero In Australia
http://www.sub-zero.com.au/

Rob Bryan @ Possum Bourne
http://www.possumbourne.co.nz/index.html

Now I have provided you with the means to get proper information. Please do so as you will learn a lot :)

Night, try to be little more friendly. Not combative.

Razor knows his stuff, plus he doesn't come off arrogant.:D

Razor,

Thanks for enlightening us on the differences in the blocks.

Cheers :)

I hope no one reads more into what I said as an informative post. I was not flaming or trying to put anyone down. Hence my smiley.

While I do not know everything about Skylines as I am still learing. Like 99% of the people visit AF. I do have fortunate position of getting information from extremely reliable and viable sources.

After all I need to know as much as possible having owned my third one in 4 years :)

God I wish they were sold new in the States when I was there.

Well now that I've successfuly stuck my foot in my mouth... :D
Thats what I get for posting at 3AM ;)

Anywho, Vince, you should write technical manuals.

No way. I don't know that much about them. Wish I did cuz I would open my own repair and tuning shop. Most of what I know i got from talking to the right people and going through the experinces as well as mistakes made by others and myself.

In the ever quest for power you have to talk to the right people. You find that many times opinions vary on to what is the best approach but at the end of the day the different combinations all have a central start point. It is getting there that can differ.

I really enjoy passing on that knowledge in hopes that I can prevent someone from making a simular mistake which in the case of tuning and upgrading can be very expensive and heart breaking.

Originally posted by NightXCZ77

Even the RB30DET uses that block.
Night

Didn't realise there was ever an RB30DET made, at least not by Nissan.

RB30 block makes a good upgrade for the 25t when mated to a 25DET head....

This is what I have spent on my car. Some of my parts are used. All in United States Dollars

R32 GTR FMIC = $200.00 used
R32 GTR Fuel Pump = $150.00 used
R32 GTR Fuel Flow Regulator = $100.00 new
Denso 550cc Injectors = $200.00 used
HKS Pod Filter = Came with car when I bought it. new
HKS Header, HKS External Wastegate and T04E kit (T3 exhaust housing bored out to fit the T04E Exhaust blades) = $800.00 used
HKS Super Dragger Exhaust = Came with car when I bought it. new
RS-R Downpipe = $100.00 new
RS-R Test Pipe = $50.00 new
Field Computer = $275.00 used
Z32 Mass Airflow Sensor = $150.00 used
Trust E-Manage with injector, ingnition, and boost sensor wire loom = $305.00 used

And that total is $2330.00 and imagine what that would be all new!

chuck at gt 3540 in it mate

First off they are two completely different blocks.

Second the bore is the same yes but as you have just said the stroke between the two is different you got that part right.

The craddles are completely different and not interchangeable. The dimension are different and so is the strength. You can not mount the gearbox out of a GTS4 or a GTR to the block of a GTS25t, while the R33 GTS4 block you can funny that.
so what does that tell you? the blocks are different in not only the back of the block but in the size and strengths of them. The R32 GTS4 block is different that of the R32 GTS-t block. The are heavier and much stronger. You don't get the flex out of them as you do in the 2wd blocks.

The RB26DETT Crank bolts into the RB25DET engine, as does its internals. You can mount the RB26DETT Transmission to a RB25DET - sorry buddy, you're wrong. The RB20DET, RB25DET, and RB26DETT transmissions all have interchangeable bell housings and can therefore be used on any engine. As far as the difference between the GTS-T and GTS4 Blocks, I know nothing about that...you could be right.

Now you mention 20psi on factory internals. Ok for how long? A steady diet of that and you WILL crush the ring lands. How do I know this? Well lets see. (4) R33 GTS25-t's have had that done already, and (3) GTR's already that I know of personally. I know the owners and I know the cars. They were tuned and other bits put on properly yet the same thing happended on all 7 motors.

I know SR20DET's that run 20+ psi on stock block, I've seen the RB26 run 28 psi on the stock block. The RB25DET can handle 20 psi on stock block providing that whoever built the engine knows what they are doing. Running 20 psi on stock block daily probably isn't the wisest idea...and yes, it will wear the engine to where you will eventually need to replace some parts.

Now you mention the RB30. Well that was used in the R30 and R31 skylines, and the VL comodore. They were single over head cam motors. The major difference there is the mounting for the trans has the same pattern as the GTR and GTS4. how do Iknow this? A tuning house by the name of Advanced Imports did a 3 litre conversion on an R32 GTS4 some years back. They put an RB25DET head on it. It was a nightmare from hell to do and as I read the article and talked to Peter Hopkins about it he says and I quote " never again. From the begining it posed many problems getting it to work right".

The RB30 was used in the VL Commodores in Australia. The R31 Skylines introduced the RB20DET as a product of the CA18DET. I have a R31 RB20DET in a 280ZX that I built. If you really want to learn something about the RB30DET, try visiting www.meggala.com he can point you in the right direction and show you how to build it with pictures.

People need to get it out of their heads that all the RB blocks are the same in strength and durability. If they were Nissan would have not made the RB26 block as a seperate casting as they did. The would have merely incorparated the other blocks to fit as needed.

The N1 block is the only true RB block from Nissan that will handle the high hp applications. Other blocks tend to fail. While all of them may not have the same durability as you may say, they are all strong blocks and can handle quite a bit of psi. I have viewed the blocks side by side and there are no true visible differences that I was able to see, yet, if the RB26 has 1mm more metal on the block than the RB25DET I suppose you can consider them different...

Night

Didn't realise there was ever an RB30DET made, at least not by Nissan.

RB30 block makes a good upgrade for the 25t when mated to a 25DET head....

The RB30E was made by Nissan for use in the VL Commodores (a GM Product) in Australia. The RB30DET is a hybrid engine using a RB25DE head and mounting a turbo.

Night

The RB26DETT Crank bolts into the RB25DET engine, as does its internals. You can mount the RB26DETT Transmission to a RB25DET - sorry buddy, you're wrong. The RB20DET, RB25DET, and RB26DETT transmissions all have interchangeable bell housings and can therefore be used on any engine. As far as the difference between the GTS-T and GTS4 Blocks, I know nothing about that...you could be right.

The bellhousings from 2wd case will NOT fit the body of the 4wd case full stop. The center "main" housings are different. That is why the GTS4 and GTS-t's have different blocks. You can modify the RB25DET housing to fit the RB26 block but not the other way around. I know it sounds silly but I've seen the bell housings and how they mate the blocks.


I know SR20DET's that run 20+ psi on stock block, I've seen the RB26 run 28 psi on the stock block. The RB25DET can handle 20 psi on stock block providing that whoever built the engine knows what they are doing. Running 20 psi on stock block daily probably isn't the wisest idea...and yes, it will wear the engine to where you will eventually need to replace some parts.

Not it isn't wise. As a matter of fact it is down right stupid to run that much boost on cast pistons. The blocks them selves can handle it yes, so can the forged cranks. The RB25 turbo engine is also higher compression so running that sort of boost you are mentioning isn't going to happen even on race fuel. You have to decompress the motor first. Anyone who knows forced induction engines should know that. I've seen what 18psi does to factory RB25 pistons in crushing the top ring land down. As far as running that much boost on an SR again I've seen plenty do it for a while, but for a very short while. If you want to run that much boost you build your engine to do it reliably and not for 1,000ks


The RB30 was used in the VL Commodores in Australia. The R31 Skylines introduced the RB20DET as a product of the CA18DET. I have a R31 RB20DET in a 280ZX that I built. If you really want to learn something about the RB30DET, try visiting www.meggala.com he can point you in the right direction and show you how to build it with pictures.

I know who meggala is. I don't need missinformation from him when I have full access to top tuners and builders of these cars.


The N1 block is the only true RB block from Nissan that will handle the high hp applications. Other blocks tend to fail. While all of them may not have the same durability as you may say, they are all strong blocks and can handle quite a bit of psi. I have viewed the blocks side by side and there are no true visible differences that I was able to see, yet, if the RB26 has 1mm more metal on the block than the RB25DET I suppose you can consider them different...
Night

So who built the other blocks, Honda? Nissan/Nismo made them all. There isn't much difference in the N1 blocks to the factory blocks. They all seem to have the same flaw and that is cylinder crackage issues between the #3 and #4 cylinder. Croydon's have gone away from the N1 block back to the standard block. At the level of hp they are making, over 1,300 there is no difference. Speaking to Mr. Nagata when Top Secret was down here he said the same thing. As a matter of fact they split 3 blocks in the week they were down here. Once you begin to breech the 950hp threshold and beyond, block life is measured in time not milage. You really need to do a bit more research and stop taking gospal from websites of wannabe's. Talk to the professionals that have been doing it RIGHT for years. Much is to be learnt and I am sure there are things you know that I don't and vice versa.

The bellhousings from 2wd case will NOT fit the body of the 4wd case full stop. The center "main" housings are different. That is why the GTS4 and GTS-t's have different blocks. You can modify the RB25DET housing to fit the RB26 block but not the other way around. I know it sounds silly but I've seen the bell housings and how they mate the blocks.

The RB20DET 2WD tranny fits on the RB25DET, the RB25DET tranny fits on the RB26DETT...been done many a time. The RB25DET housing bolts up to the RB26DETT block unless you have completely different engines in Australia than we do in Japan. That is how the majority of people that swap the RB26DETT into their cars in the US convert to RWD to make it a useful application.


Not it isn't wise. As a matter of fact it is down right stupid to run that much boost on cast pistons. The blocks them selves can handle it yes, so can the forged cranks. The RB25 turbo engine is also higher compression so running that sort of boost you are mentioning isn't going to happen even on race fuel. You have to decompress the motor first. Anyone who knows forced induction engines should know that. I've seen what 18psi does to factory RB25 pistons in crushing the top ring land down. As far as running that much boost on an SR again I've seen plenty do it for a while, but for a very short while. If you want to run that much boost you build your engine to do it reliably and not for 1,000ks

I agree with you there...running that much psi isn't at all wise on a daily basis...yet people have done it and continue to do it (many blow up). One person in the US is claiming 539 RWHP on a stock block SR20DET...and says he runs it at that HP level quite regularly...The stock pistons are the weak point of the RB engines...no doubt about it. Boost also depends on the size of the turbo you are running as you well know. Different CFM ratings effect the engines in different ways even though you are pushing the same psi...so 20 psi on a slightly larger turbo than stock is tolerable, 20 psi on a large T04 turbo is not...but I don't need to tell you that, I know you know these things.


So who built the other blocks, Honda? Nissan/Nismo made them all. There isn't much difference in the N1 blocks to the factory blocks. They all seem to have the same flaw and that is cylinder crackage issues between the #3 and #4 cylinder. Croydon's have gone away from the N1 block back to the standard block. At the level of hp they are making, over 1,300 there is no difference. Speaking to Mr. Nagata when Top Secret was down here he said the same thing. As a matter of fact they split 3 blocks in the week they were down here. Once you begin to breech the 950hp threshold and beyond, block life is measured in time not milage. You really need to do a bit more research and stop taking gospal from websites of wannabe's. Talk to the professionals that have been doing it RIGHT for years. Much is to be learnt and I am sure there are things you know that I don't and vice versa.

If Honda built a Nissan block, I'd probably end up going insane. I know that Nissan/Nismo made them all, however, they made the N1 block a little stronger (according to most results and what comes from the mouth of Nissan). While the N1 block may not be much stronger at all, from all of the hype, it is supposed to be. 1300hp is an awesome number...wish I could be there to see it, no doubt, I would love to come to Australia and check out the Skylines running there, but time and money don't permit it right now. I have never heard too much of the cracking issues, but then again, I have not been around 1000hp Skylines or Skyline engines. I trust what you say is correct and value your knowledge...just as you said, you know things that i don't and vice versa I would guess.


Night

Actually I currently reside in New Zealand not Australia. :) Australia is still playing catch up on these cars :iceslolan

As far as the strengths of the N1 block vs the non-N1 there is a bit of a difference but as mentioned no one has yet to fully determine it. They all seem to suffer the same flaw. Too bad as Nissan should have taken a very close look at the 2JZ motor from Toyota. That 3 litre block is damn strong!

I've always hoped someone would develope an alloy RB26 block. We all know that you can make them stronger than a cast block any day of the week. Cast blocks are pourous from the start which why they are and always will be weaker, whereas with alloy blocks getting the right mixture you can make is substantially stronger.

As far as the trans to block thing the RB25DET trans will bolt right up to the RB20(all), RB25, RB26 blocks. Yes the conversions have been done here also quite regularly on R32 GT-ts, a few Silvia's with RB26 transplants, and one GTR.

The 2JZ is a damn strong engine, however it seems to lack in just a few things...it's ability to handle boost and HP is not one of them. How would you compare the RB30 block to the rest of them as far as strength is concerned? I was looking to possibly build one this upcoming year for drag use.

What kind of alloys were you thinking of for the RB26 block? I know a machine here in the US that can do it. If you get a chance to next year, visit SEMA in Las Vegas...there's a lot of awesome stuff. Basically, you blueprint out the RB26 block via this machine...the machine then punches it out in very thing layers of materials and constructs it right in front of you....you then have the material for the mold...create a mold of the engine and then you have the ability to create it in whatever alloy you wish I am assuming...not knowing too much about the whole casting scenario. I know that they had a chevy V6 engine that they had created with this machine there...it was quite a site.

Hopefully Nissan will get away from their Desire to be the NA power plant leaders and go back to making quality Turbo Vehicles...but who knows? I'd love for them to make a product that can even compete stock with the new Dodge SRT-4 here in the US that hits a 13 second 1/4 in stock form...and costs $20,000....the 350Z starts at $27,000 and hits a low 14....

Night

Well I've never been a fan of the RB30 mostly due to is rather skimpy cradle that is used. The block itself doesn't look much beefer than the RB26 other than slightly taller overall. There is a guy here who has put on in an R32 GTS4 with an RB25DET head on it. Supposedly it has a standard bottom end, and they are making some pretty decent grunt out of it with a much bigger turbo GT30 and NOS. Has run a 10.4 so it is pretty formattable.

I would like to get back to the states at some stage for a visit with my family. If I have the time I may stop by their shop.

sorry to interrupt in your discussion but i have question about the skyline used in the jgtc. on some pics the engine is a v6. which engine is the base for this block?

Derby

I would guess the VQ30...?

i'm quite newbie on skyline engineblocks. but i thought the jgtc uses stock cars with some bodywork and higher boost. till i heard the supra used a 4 cilinder 2.2.
then the pic of the v6 skyline. it kept me wondering

Derby

First, I would like to say I joined this board just to repond to this thread and this is my first post. I found this thread in my own search for more information on RB25DET engines versus RB26DETT engines. The primary reason why I am posting is to correct some of the gross inaccuracies that are here and hopefully help this discussion.

I would like to address the RB25DET to RB26DETT transmission issue. An RB26DETT 4WD tranny will bolt up to an RB25DET block and an RB25DET tranny will bolt up to a an RB26DETT block. The only issue between the 2 is that the oil pans are different. To use an RB25DET tranny on an RB26DETT engine, you need to swap the oil pan to an RB25DET pan. The 4wd transmission is larger and requires a different oil pan to fit. This is well documented on the net and has been well proven in swap kits by McKinney Motorsports.

I don't know a lot about RB internals, but I know an awful lot about 2JZ Toyota internals. The 2JZ-GTE(3.0L twin turbo) and 2JZ-GE(3.0L non-turbo) engines in Supras use the exact same closed deck cast iron block, forged steel crank and connecting rods. They do have different pistons for different compression ratios(8.5:1 vs. 10.0:1), but both engines have cast pistons. Yes, that is right: cast pistons. There are people running over 800 RWHP on stock 2JZ-GTE shortblocks with stock cast pistons. SW ran a 9.81 @ 153 with a T72 and a small shot of NOS without the head ever being taken off his engine. We have people running over 700 rwhp on stock 2JZ-GE shortblocks using just a thick head gasket to reduce the compression. Just because a piston is cast, doesn't mean it is weak. Forging gives more uniformity to the piston, but many of todays cast pistons use special alloys to reduce heat or provide smoother expansion. The trick is more in having the right timing and fuel to keep it safe. 2 bars of boost are never run without race gas(100+ octane) and a healthy 11.5:1 or richer A/F. Using leaded race fuel is even safer for the engine since lead as an additive removes heat from the combustion chamber.

Since I don't know much about RB internals, I can't comment much on the RB side. Here is what I do know. I do know that JMS put down almost 600 RWHP on their stock shortblock GTS-T with just a thicker HKS head gasket to reduce the compression a half point(9.0:1 to 8.5:1). While we have a tremendous Supra community, Nissan never sold a car with an RB in the states. If you really want to know how strong the block and internals are, flip the block over and look at it. Both the RB26DETT and RB25DET used closed deck cast iron block. I have the same question as everyone else: how durable are the internals? If the outer webbing is the same, what do the main bearings and girdles look like between the 2? How do the rods compare in thickness? I saw some picks of stock RB25DET rods and they look quite beefy, but they also are fairly short and travel a shorter stroke than 2JZs. A shorter stroke means lower pistons speeds and less stress on the crank and rods, but more on the cylinder walls. Controlling the piston to rod speed is all part of the equasion. Running 2 bars of boost at 6000 rpms is less stressful on the engine than 1.5 bars are 9000 rpms. If you spin it high enough you can break anything.

Alloy blocks are also not necessarily better. Their sole main advantage is weight. Although they weigh less, they have to be far thicker to meet the same strength as a dense iron block. They have more problems with cooling, often requiring open decks(most Hondas) that weaken them even more. Part of the cooling problem is that they need cylinder liners that are more resiliant to heat of combustion than the surrounding alloy. The cylinder liners expand at a different rate than the surrounding block, so controlling the fluid temperature is extremely important to keep expansion similar or the sleeves could separate from the block. Overboreing is rarely possible on alloy blocks. The sleeves normally have to be replaced when installing oversized pistons. With iron blocks and solid decks, you normally have plenty of room to overbore without any negative consequences. What I am curious of is the durability comparison of a stock RB26DETT engine to an RB25DET engine with a thicker head gasket, both putting down 600 RWHP?

G35C6MT,

Cool, engine talk.

You were saying that alloy blocks have a problem with cooling? I have never heard that, but then again I have never been around them. I would think that since there made of aluminum, they would dissipate the heat better, but then again I do not know.

First off they are two completely different blocks.

Second the bore is the same yes but as you have just said the stroke between the two is different you got that part right.

The craddles are completely different and not interchangeable. The dimension are different and so is the strength. You can not mount the gearbox out of a GTS4 or a GTR to the block of a GTS25t, while the R33 GTS4 block you can funny that.
so what does that tell you? the blocks are different in not only the back of the block but in the size and strengths of them. The R32 GTS4 block is different that of the R32 GTS-t block. The are heavier and much stronger. You don't get the flex out of them as you do in the 2wd blocks.

Now you mention 20psi on factory internals. Ok for how long? A steady diet of that and you WILL crush the ring lands. How do I know this? Well lets see. (4) R33 GTS25-t's have had that done already, and (3) GTR's already that I know of personally. I know the owners and I know the cars. They were tuned and other bits put on properly yet the same thing happended on all 7 motors.

Now you mention the RB30. Well that was used in the R30 and R31 skylines, and the VL comodore. They were single over head cam motors. The major difference there is the mounting for the trans has the same pattern as the GTR and GTS4. how do Iknow this? A tuning house by the name of Advanced Imports did a 3 litre conversion on an R32 GTS4 some years back. They put an RB25DET head on it. It was a nightmare from hell to do and as I read the article and talked to Peter Hopkins about it he says and I quote " never again. From the begining it posed many problems getting it to work right".

Another notable is the fact once you stroke the RB26 block to 2.7 or 2.8 litres #3 cylinder has a tendancy to crack. Again how would I know this? Well Crodyon Wholesalers R32 GTR has went through 3 count them 3 N1 blocks with the same failure. Reece Megreggor, current holder of the quickes 4wd car in Australasia has had it happen as well and his is not even stroked.

If the R25 block was so strong then why don't the Japanese use them instead of the more expensive or should I say much more expensive RB26 block? In the JGTC all he Skylines are 2wd and up until recently all used the RB26 block. They did not use the RB30 or RB25 blocks, and that was for a very good reason. Reliability and strength.

I am not taking anything away from the RB25 block as yes it can produce some good hp numbers. In fact I have heard of a few in Japan pushing 900hp, but they don't last long even with the right gear in them.

People need to get it out of their heads that all the RB blocks are the same in strength and durability. If they were Nissan would have not made the RB26 block as a seperate casting as they did. The would have merely incorparated the other blocks to fit as needed.

You don't have to beleive me. Contact these following companies and ask them for youself.

Lee Sutton @ Advanced Imports
http://www.advan.co.nz/

Nick Jenkins or Greame McDonnald @ Croydon Wholesalers
http://www.croydons.co.nz/

Sub Zero In Australia
http://www.sub-zero.com.au/

Rob Bryan @ Possum Bourne
http://www.possumbourne.co.nz/index.html

Now I have provided you with the means to get proper information. Please do so as you will learn a lot :)



Sorry for turning this into my own personal thread.
I have the following modifications done to my r33 gts25t.
act clutch
apexi safc
apexi fuel regulator
manual boost controller.
3in exhaust
front mount intercooler

Im thinking of changing my stock turbo to a t3/t4 turbo capable of providing up to 30psi boost. What would be a safe boost level with this kind of mods that would accomodate my stock internals?