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RB26DETT turbo setup on RB25DET

mambastu

By mambastu,
in Engines & Forced Induction

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mambastu Collaborator

mambastu

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Hi all,

I've already done a search for this but couldn't find that much on the subject.

How feasible is it to adapt the RB26DETT turbo setup onto the RB25DET and how much power will the standard twin turbo setup allow ?

I'm aiming for around 450bhp at the flywheel and I've been offered a complete GTR twin setup for a reasonable price, about a 1/3 the price of the manifold I'd need for a GT30 setup so its quite tempting.

What difficulties need to be overcome to get them to fit ? I've read that the exhaust manifolds have a different stud pattern which I think I can overcome either by re-welding the flanges or by getting a spacer plate fabricated but are the exhaust ports the same shape on the RB26 and the RB25 ?

Does anyone know if the block feeds are in the same place for the water and oil lines ?

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https://www.sau.com.au/forums/topic/25123-rb26dett-turbo-setup-on-rb25det/
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Guest RedLineGTR

Guest RedLineGTR

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Would like to know if that would work to. even a stock DETT setup would it bolt on to a DET block and what would u have to change i would guess oil lines water exhaust...andything else. Sorry to hijack the thread but on similar topic. Cheers Rob

Sydneykid Grand Master

Sydneykid

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Hi Guys, how do you propose to run 2 AFM's? The wiring harness only has capacity for one. Ditto the ECU. The RB26 oil pump has additional flow for the extra turbo, ditto the water pump. You can't use the standard RB26 turbo outlet piping as the exhaust cam cover fouls it. How do you propose to run 2 lambda sensors? The wiring harness only has capacity for one. Ditto the ECU.

I don't recommend cutting and welding the cast manifolds, the exhaust heat will most likely cause cracking. You could make an adaptor for the exhaust manifold, but I don't know how you would be able to do up the lower bolts on #3, # 4 & #5.

If it was easy there would be heaps around, I've never seen one, how about anyone else?

mambastu Collaborator

mambastu

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Originally posted by Sydneykid

Hi Guys, how do you propose to run 2 AFM's?  The wiring harness only has capacity for one.  Ditto the ECU.   The RB26 oil pump has additional flow for the extra turbo, ditto the water pump.  You can't use the standard RB26 turbo outlet piping as the exhaust cam cover fouls it.  How do you propose to run 2 lambda sensors? The wiring harness only has capacity for one.  Ditto the ECU.

I don't recommend cutting and welding the cast manifolds, the exhaust heat will most likely cause cracking.  You could make an adaptor for the exhaust manifold, but I don't know how you would be able to do up the lower bolts on #3, # 4 & #5.

If it was easy there would be heaps around, I've never seen one, how about anyone else?

Hi,

Good questions, quite a lot I hadn't even thought about :(

First of all the engines actually going to go into my UK spec 200SX S13. I already have a GReddy E-manage running a Z32 AFM on the current CA18DET so the plan is to use the Z32 AFM with the E-manage on the RB. I will have to construct a Y piece to join the turbo inlets to the back of the AFM. The turbo outlet pipes will be fabricated to clear the Cam covers.

I wasn't really anticipating the oil pump and water pump flow to be a problem to be honest. I've seen SR20's and CA18's with twin turbo setups that used the standard pumps and I presumed the RB25 standard items would be able to cope. Could be a problem.

Lambda sensors - I was only planning to use one but I haven''t decided whether to use one of the original sensors behind one of the turbos as per the GTR setup or place the lambda sensor further down after the two downpipes have joined together. I will need to fabricate new downpipes anyway.

The main problem, as you say Sydneykid, is going to be the manifold stud pattern. I've heard (and this could be a load of crap) that the reason the exhaust flanges are different on the RB26 is due to the manifold pipe layout for the twin turbo setup.

I was originally thinking of cutting and welding the relevant manifold flanges but from my own experiences with a T3 adapted CA18DET manifold the heat generally does cause cracking as you suggested so I think I'll need to have a steel spacer plate fabricated. I'll use longer studs and captive studs where necessary.

I can foresee a further problem here, the spacer plate will have to be made fairly thick to prevent warping etc. The RB's going in an S13 not a Skyline so I may have clearance problems on the suspension turret when I use the spacer plate. It may actually be easier to fabricate two 3 branch tubular manifold than adapt the RB26 setup.

I know there is an S13 in Australia with an RB25DETT but I haven't been able to find out much about it.

The main reason I'm contemplating it is down to cost. It will cost me around £2500 to £3000 to get a GT30, wastegate and manifold sent from Oz to the UK......I can get a low mileage GTR twin turbo setup for around £350. Even allowing for fabrication costs it should work out a lot cheaper.

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