Why go RB26 (under 500hp) opposed to rb25

[Wedge]

Boozt3d , how is the response on that setup laggy or highly responsive ? I guess its laggy but im still asking .

[madmatt48]

RB26DETT is a great engine in many aspects except for one thing. The timing belt and tensioner assembly. Of the many cars, I had owned two R32 Skyline GT-Rs when I lived in Japan from 1989 to 2005. Unfortunately when I left Japan, Motorex had issues with importing 1989 GT-R's for some reason so I had to sell mine to someone in another country.

[triple B]

Please explain how.

 

 

well careless makes an excellent poin tplus there is the fact it is a twin turbo engine.

 

granted upgrades for the RB26 can be a bit pricy when you start doing turbo upgrades.

 

with my RB25 i have invested in forged internals at about $1200 as well as a new intake manifold (greddy/ trust) for $700 a big turbo at $1300. and the list goes one

 

granted to make big number you have to build for it and with the RB26 you do nto have to build as much compared to the RB25

[eh?]

simple. most importantly, the head designs are different enough to make it easier or more reliable to pack more air into the cylinders on RB26 than on the RB25. anyone and everyone knows that developing horsepower means developing an efficient engine head.

 

add the stronger internals, a big single turbo, put some ARP rod bolts and head studs + metal headgasket, and you have what Boozt3d had.

 

680whp on a stock shortblock (no rod bolt upgrades)

 

Keep in mind we are talking about 500whp. I agree the RB26 is the superior motor for big power.

True the RB26 head flows better with the higher valve lift,duration and diameter. However we know the RB25 can make 500whp on stock cams so that point *imo* is moot.

Both the RB25 and RB26 have cast pistons, both do break we all know. either one I'd be looking at forged internals for longevity. RB26 rods are thicker but have you ever heard of RB25 rods breaking? Rod bolt upgrade needed on both. There is a RB25 on FA that supposedly makes 697whp on the stock bottom end. But for how long?

RB26 Stock twins aren't going to make 500whp, neither are the maf's, and injectors. RB26 has the advantage of a chipable ecu, but who really uses one rather than a pfc?

The RB26 best advantage (in the later RB26's) is the longer crank collar. But then it has the disadvantage of requiring the sump mod and requiring the RB25 tranny. (unless you wan that extra work of modding the 4wd xfer case)

My point is at that level one really isn't going to be that much easier than the other. But the RB26 will prevail at higher levels.

[RB26powered74zcar]

RB26DETT is a great engine in many aspects except for one thing. The timing belt and tensioner assembly.

 

 

Thats the first time I've heard that one.... can you explain what's wrong with the timing belt and tensioner assembly?

[Careless]

Keep in mind we are talking about 500whp. I agree the RB26 is the superior motor for big power.

True the RB26 head flows better with the higher valve lift,duration and diameter. However we know the RB25 can make 500whp on stock cams so that point *imo* is moot.

Both the RB25 and RB26 have cast pistons, both do break we all know. either one I'd be looking at forged internals for longevity. RB26 rods are thicker but have you ever heard of RB25 rods breaking? Rod bolt upgrade needed on both. There is a RB25 on FA that supposedly makes 697whp on the stock bottom end. But for how long?

RB26 Stock twins aren't going to make 500whp, neither are the maf's, and injectors. RB26 has the advantage of a chipable ecu, but who really uses one rather than a pfc?

The RB26 best advantage (in the later RB26's) is the longer crank collar. But then it has the disadvantage of requiring the sump mod and requiring the RB25 tranny. (unless you wan that extra work of modding the 4wd xfer case)

My point is at that level one really isn't going to be that much easier than the other. But the RB26 will prevail at higher levels.

 

But one would need to upgrade to a large single to make 500 on a RB25 if you say an RB26 twin turbo setup surely cannot make that sort of power as well.

 

fentin_fury is running modified standard equipment R34 twin turbos (right?) and makes 470 whp or so. that's pretty close to 500. I can't see an RB25 reaching 500 any quicker than an RB26 would.

 

The only thing is the extra 2000 it would cost to start with the RB26.

 

I'd say its a toss up. with the RB26 just having initial cost on the plus side.

 

the rest is really up to the direction the builder wants to take... RB25 transmission + RB20 pan.

 

For cost savings, i'd go RB25 due to initial cost and headache of procuring a transmission or bellhousing for a reasonable price.

[mannyvig]

The belt and tensioner issue is the same with ass rubber belt Nissans and most imports in general. They don't jump or break if yopu change them when you are supposed to. We all know the reason they go bad is age, heat, or oil. If you are in Phoenix, belts need to be changed on the money. And if you have leaky front seal or cam seals it will fubar the belt also. It is definately not an RB26 issue its a "rubber belt" issue. Essentially its the exact same problem with the 25 aas the 26. It needs to be addressed on both motors. Remember when you get an RB2X it may have low mileage but its still old. Rubber "ages" in time not miles.

Others might have different experiences but this is what I have found in my experience.

[fentin_fury]

 

fentin_fury is running modified standard equipment R34 twin turbos (right?) and makes 470 whp or so. that's pretty close to 500. I can't see an RB25 reaching 500 any quicker than an RB26 would.

 

I was getting 432 whp at 18lbs boost. I could (and did) run upto 20lbs. The turbos were modified bnr32 units with GTR turbines, ported, larger flapper, etc. About 30% more flow (based on turbine size). Upon tear down we did not find any issues on internals at all. Head gasket was going. That was it.

 

I found the parts (except for the oil pump ) quite reasonable compared to an L28 high performance build. Obviously some extra peices - cam, turbos... but as far as internals went RB26 parts are priced quite aggressively.

 

Q

[Careless]

Keep in mind we are talking about 500whp. I agree the RB26 is the superior motor for big power.

True the RB26 head flows better with the higher valve lift,duration and diameter. However we know the RB25 can make 500whp on stock cams so that point *imo* is moot.

Both the RB25 and RB26 have cast pistons, both do break we all know. either one I'd be looking at forged internals for longevity. RB26 rods are thicker but have you ever heard of RB25 rods breaking? Rod bolt upgrade needed on both. There is a RB25 on FA that supposedly makes 697whp on the stock bottom end. But for how long?

RB26 Stock twins aren't going to make 500whp, neither are the maf's, and injectors. RB26 has the advantage of a chipable ecu, but who really uses one rather than a pfc?

The RB26 best advantage (in the later RB26's) is the longer crank collar. But then it has the disadvantage of requiring the sump mod and requiring the RB25 tranny. (unless you wan that extra work of modding the 4wd xfer case)

My point is at that level one really isn't going to be that much easier than the other. But the RB26 will prevail at higher levels.

 

But one would need to upgrade to a large single to make 500 on a RB25 if you say an RB26 twin turbo setup surely cannot make that sort of power as well.

 

fentin_fury is running modified standard equipment R34 twin turbos (right?) and makes 470 whp or so. that's pretty close to 500. I can't see an RB25 reaching 500 any quicker than an RB26 would.

 

The only thing is the extra 2000 it would cost to start with the RB26.

 

I'd say its a toss up. with the RB26 just having initial cost on the plus side.

 

the rest is really up to the direction the builder wants to take... RB25 transmission + RB20 pan.

 

For cost savings, i'd go RB25 due to initial cost and headache of procuring a transmission or bellhousing for a reasonable price.

[madmatt48]

Outstanding post Mannyvig, I like your description on the belt. I was referring to the bolts that hold the belt tensioners secure are prone to break, which loosen the timing belt and smash/bend every valve that happened to be open at the time the belt stopped driving the cams. One specific time was when the engine was at idle(800 rpm) while waiting for a traffic light, the engine abruptly stopped with no other abnormal indications on the instrumentation. Engine would not re-start and sounded like all the spark plugs were pulled (no compression) while attempting to re-start. Engine dissassembly revealed the left timing belt tensioner bolt had sheared in half, the tensioner had released the belt and even at idle, the valves were bent to the point where no compression was available for engine operation. Unfortunately upon talking to other GT-R enthusiests when I lived in Japan, other occurances similar to mine have occurred. Something to be aware about when assembling the RB26. Ensure all the bolts that hold the tensioners are inspected for any defects, cracks, integrity or completely replace with new ones every time the belt is changed. Your timing belt is only as good as the tensioners holding it in place. Other than that and some other stock parts that most people change, The RB26 is quite the engine to have in a skyline or any Z-car.

[RB26powered74zcar]

I have heard of that happening on occasion. I thought you maybe knew of another issue ...

 

It would be wise then to go ahead and source ARP replacements then.

[Careless]

It's a good thing I haven't bought my tensioners or tensioner studs yet.

 

do you know which ARP number I'm looking for when matching this tensioner stud? Or can i bring it to Brafasco and have them match me a set of studs that are as strong as ARP's?

[getoffmyinternet]

Stony's '26 made 400rwhp with the stock turbos. He was limited to 14-15psi with the stock turbo's. If he could have run 23-25 psi(steel or inconel turbo wheels) it would have made 500 rwhp.

 

Really? I was under the impression that over .8 the stock ceramic turbine turns into a dandelion. Or is this not the case as yours still had the benefit of being ball bearing?

[stony]

1 bar or 14-15 PSI is the area where they come apart.

[Cal Poly Zmanaustin]

Cliff,

I didn't realize you were in the 9's now...wow!

[stony]

[stony]

Oh yea and it's clint not cliff:wink:

 

 

Sorry for the threadjack

[Cal Poly Zmanaustin]

Oh yea and it's clint not cliff:wink:

 

Clint,

I actually knew that; just typed too fast. My son has been watching the movie Cars from Pixar a lot. At the end of the movie they show several other Pixar films where the former 'Cheers' actor that played Cliff does voiceover. I had that stuck in my head. Funny!

[stony]

I was just joking BTW

[Canadianz]

After reading this entire thread one thing I would like to point out is that the RB26 does have a bit of an edge in the aftermarket as far as manifolds, cams etc. Based on personal experience building the RB series engines is getting cheaper than it used to be, however it still hurts if you look at the price on a set of tomei cams for the RB25 at around 1k compared to the prices Ive seen for cams on other engines.

 

As far as the engine physically, both engines run ceramic turbines which don't like too much boost over 13psi or so, that being said I have seen an RB26 that with ceramic turbos that lasted at 22 psi before the owner blew all the ring lands off as he was running only a boost controller. The knock against the RB26 for me was that to upgrade the turbines and get them balanced I would pay about the same as a brand new turbo for the RB25.

 

The head design of the RB25 vs RB26 came up also and the 26 does have a better flowing head, with a stronger valve train. These engines like to rev and make most power up top so it is nice to know that you can wring out a 26 a bit longer before you have to shift.

 

Both engines are a ton of fun, if your looking for giant numbers it might be smarter to buy an engine that is produced in North America, that way you don't spend quite as much on parts at least. It is also nice to be able to hit up the parts store without spending a couple minutes cross referencing all your part #'s before you start.

 

Both swaps are awesome and both will cost a fair bit to reach 500 horsepower if you want it to last. Ask any of the guys on here running 400 horsepower and up how much they have spent on their engine bay. Its not cheap by any means.