Can a 26 turbine kit be bolted to a 25?
Can a 26 turbine kit be bolted to a 25?
I'm thinking of doing a 25 swap...I want a HUGE HKS BB turbo...A T51RKIA to be exact.... My question is this...Will a mani made for a 26 bolt to the head of a 25? Intake mani as well as exhaust....
No, I wish they did.
The Intake manifold on the RB26 is exactly backwards of the bolt pattern on the RB25 engine, plus, it is missing it's water passage holes.
The Exhaust manifold will not fit due to a few of the bolt patterns being flipsided....if it was going to be that easy, I would have done it a long time ago lol.
The Intake manifold on the RB26 is exactly backwards of the bolt pattern on the RB25 engine, plus, it is missing it's water passage holes.
The Exhaust manifold will not fit due to a few of the bolt patterns being flipsided....if it was going to be that easy, I would have done it a long time ago lol.
The 25 head flows better than the 26. The hydraulic head on the 25 is also idea vs the mechanical head on the 26. The 26 has forged pistons, but you can do forged on the 25 or a full stroker kit to make it a RB28....would turn out much better. Plus, on the 26 you would probably do a single turbo conversion....RB25 already has the single turbo.
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Nismo_Freak
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Explain to me how the hydraulic lifters (which collapse quite often) are "better" than the mechanical lifters on the RB26. I'd also like to hear some supporting evidence on how the RB25's head flows more than the RB26s. Especially when the RB26's valvetrain is rated to about 8500 rpm in stock form, I wouldn't dare take an RB25 stock head that high.
BTW, I'd suggest you get the RB25, as there are intake manifolds as well as RB25 specific exhaust manifolds available w/ T3 or T4 flanges which will fit the larger HKS turbines. If you want a really powerful RB25 and some response to go with it I'd look into the GT3037 class turbocharger, but it sounds like your after peak hp.
BTW, I'd suggest you get the RB25, as there are intake manifolds as well as RB25 specific exhaust manifolds available w/ T3 or T4 flanges which will fit the larger HKS turbines. If you want a really powerful RB25 and some response to go with it I'd look into the GT3037 class turbocharger, but it sounds like your after peak hp.
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Imissmyturbo
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I don't think the RB25 is by any means better then an RB26. The RB26 has a stronger bottom end with a lover CR. The RB26 has a better flowing intake manifold too. The down side the the RB26 is the cost. Other then that the RB26 would be the best engine. But that doesn't mean the RB25 isn't a good choice for a swap. The high compression ratio (for a factory turbo engine) means that when running more boost your timming and fuel have to be dead on. I do beleave the solid lifter design on the RB26 is idea for higher reving. The best part about the RB25 head is the RB30 block that can be bolted up to it. I am willing to bet for the $$ you could have an RB30 setup Vs an RB26. I can't comment of the RB25 vs RB26 head flow. Oh and an RB26 Turbo is a T28 and I don't think it would bolt up to an RB25 manifold plus the RB25 single turbo has more potenial then one of the twins.
Actually, the hydraulic lifters on the 25 head are ideal with most people that tune these engines in Japan and Australia. The VVTC is also a nice feature of the RB25 head.
The RB25 head has the capacity to flow more air based on the runner size of the manifold. If you have ever taken the two engines apart side by side, you would know this. The RB25 has a heart shaped open runner and opening on the head, the RB26 has a smaller, round port on the manifold and the head. The larger a hole, the more air you can get through it.
The RB25 head has the capacity to flow more air based on the runner size of the manifold. If you have ever taken the two engines apart side by side, you would know this. The RB25 has a heart shaped open runner and opening on the head, the RB26 has a smaller, round port on the manifold and the head. The larger a hole, the more air you can get through it.
Nismo_Freak wrote:Explain to me how the hydraulic lifters (which collapse quite often) are "better" than the mechanical lifters on the RB26. I'd also like to hear some supporting evidence on how the RB25's head flows more than the RB26s. Especially when the RB26's valvetrain is rated to about 8500 rpm in stock form, I wouldn't dare take an RB25 stock head that high.
The RB26 does have a stronger bottom end because it has forged pistons and it also has 444CC injectors making it able to handle more boost stock than the RB25 with its 370CC injectors.
The RB26 has a better flowing manifold - true due to size, but the airflow to the last 2 cylinders is more limited due to the shape of the manifold. The airflow into the head is also limited because of the size of the independant throttle bodies (which are smaller than the opening on the RB25 head by far) which has the same size runner and same airflow going to each cylinder. The only true downfall of the RB25 intake manifold is the throttle body size.
The RB26 has a better flowing manifold - true due to size, but the airflow to the last 2 cylinders is more limited due to the shape of the manifold. The airflow into the head is also limited because of the size of the independant throttle bodies (which are smaller than the opening on the RB25 head by far) which has the same size runner and same airflow going to each cylinder. The only true downfall of the RB25 intake manifold is the throttle body size.
Imissmyturbo wrote:I don't think the RB25 is by any means better then an RB26. The RB26 has a stronger bottom end with a lover CR. The RB26 has a better flowing intake manifold too. The down side the the RB26 is the cost. Other then that the RB26 would be the best engine. But that doesn't mean the RB25 isn't a good choice for a swap. The high compression ratio (for a factory turbo engine) means that when running more boost your timming and fuel have to be dead on. I do beleave the solid lifter design on the RB26 is idea for higher reving. The best part about the RB25 head is the RB30 block that can be bolted up to it. I am willing to bet for the $$ you could have an RB30 setup Vs an RB26. I can't comment of the RB25 vs RB26 head flow. Oh and an RB26 Turbo is a T28 and I don't think it would bolt up to an RB25 manifold plus the RB25 single turbo has more potenial then one of the twins.
Imissmyturbo wrote:I don't think the RB25 is by any means better then an RB26. The RB26 has a stronger bottom end with a lover CR. The RB26 has a better flowing intake manifold too. The down side the the RB26 is the cost. Other then that the RB26 would be the best engine. But that doesn't mean the RB25 isn't a good choice for a swap. The high compression ratio (for a factory turbo engine) means that when running more boost your timming and fuel have to be dead on. I do beleave the solid lifter design on the RB26 is idea for higher reving. The best part about the RB25 head is the RB30 block that can be bolted up to it. I am willing to bet for the $$ you could have an RB30 setup Vs an RB26. I can't comment of the RB25 vs RB26 head flow. Oh and an RB26 Turbo is a T28 and I don't think it would bolt up to an RB25 manifold plus the RB25 single turbo has more potenial then one of the twins.
You can put a RB26 head on a RB30 bottom end, all that needs to be done is to tap the block that it
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Nismo_Freak
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The lifter is the almost exactly like the SR20 hydraulic lifter, which has proven time after time to die. It's the same for the VG30. If the hydraulic lifters were superior to the mechanical ones then why do they offer a mechanical conversion kit.DCIracer wrote:Actually, the hydraulic lifters on the 25 head are ideal with most people that tune these engines in Japan and Australia. The VVTC is also a nice feature of the RB25 head.
The RB25 head has the capacity to flow more air based on the runner size of the manifold. If you have ever taken the two engines apart side by side, you would know this. The RB25 has a heart shaped open runner and opening on the head, the RB26 has a smaller, round port on the manifold and the head. The larger a hole, the more air you can get through it.
If your basing headflow solely on the manifold and the size of the intake port opening then you are making a mistake. Headflow is determined by the amount of air that can flow THROUGH the head, not into it. I could make a head with a 4" opening but with .2" valves that would flow asbsolutely nothing compaired to an engine with a 2" opening and valves twice the size. Flow is not based on size nor is it based on the look of the head (IE. Polished everything). The RB26 head may feature a smaller intake port opening but this helps to maintain velocity in the head. The only true way to determine head flow is to flow bench the two at the same vacuum.
The manifold on the RB25 is an equal length runner design. This is ideal for providing equal dispersion of intake air to the cylinders, but it also becomes a restriction in it's own right due to it's longer curved intake runners. The runner design is there to produce midrange intake air velocity into the cylinders to improve bottom end filling of the cylinder. This is why the RB25 has better low end and midrange response than the RB26. The RB26 on the other hand has a typical blow through manifold design with 3 dual throttle body setups and short runners. The manifold was designed to do one thing, flow at high rpms.
If it were true that the hydraulic lifters and RB25 head did flow better and operated better don't you think we would see the widespread modification of the RB26 head to accomodate this? Instead we see the opposite.
Talk to Mario at Ex Vi Termini, try to tell him to keep the hydraulics in an SR20 or RB25 head.
Or, you can call JUN and ask why they are using RB26 lifters in their 2JZGTE builds.
Tomei has a solid lifter conversion on their higher stage pre-built motors.
There are 3 very very reputable engine builders from down under and mainland Japan that found the need to change over.
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Nismo_Freak
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NightXCZ77 wrote:Nismo Freak - Have you ever had a RB26 head paired up side to side with a RB25 head?
Yes, and the RB25 head does look better.. Getting a head that flows 1500 cfm when you have a turbo that flows 500 cfm will make less power than a head that flows 1000 cfm.
I'm more or less thinking of reality. Take for instance 400hp. After that you have to really consider your drivetrain status. The RB20 head will obviously need re-working. The RB25 head obviously will be up to the task. However the RB26 head should be right were it's needed.
It's the same as using a huge dominator intake on a small block with a stock cam. If you can't take advantage of the added airflow of the manifold your just hurting performance because of the drop in airflow velocity.
Moral of this story ... match you components.