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the gears can always let you unlock the best of what you have got, shifting the powerband just enough to make it what you were after.

you wont need to change the belt when you change the gears though. Just put the motor to TDC on 1 and draw a mark on the belt where the mating marks sit on the gears. the new gears will have the mating mark in the same spot.

I think just line everything up at TDC and reference the std markings in the block and timing backing plate etc. Belts can skip a tooth and flop around the crank pulley and when you tensio it back up be a way off where the old markings were. Best go on the block markings and not care about the belt

that's the right way to do it, yet I detected OP did not want to pull lower timing case off as its the majority of the task in changing the belt (done 10ks ago).

in which case you can be dodgey and do it the other way.

myself id do it properly. just sayin'

Ok, So have wasted time and money thinking about the RB25 and 20G setup and leaning on it for all its worth. I want to be sure that walking away from what has been a champion turbo is the right thing to do. Also will give a good baseline for other setups being trialled

So by the end of the day will be interesting to compare:

RB20 RB25

TD06-20G. 8cm 12cm

Cams Std 256/8.5 Tomei

Fuel E85 E85

Both engines run the same inlet and exhaust manifolds. As it is an R32 RB25 it does not have NVCS will be interesting if the better breathing hot side, bigger cams and bigger engine will result in more power then I was making on the RB20

Figured I'd do an update on my setup.

old-return-flow-intercooler-kit-RB25.jpg

I made 235kw on 18psi, RB25 TD06 20G 10cm.

All you cool cats worked out my intercooler was shit house, you were all right!

I've stuck to return flow as I want it the engine bay as factory looking as possible, but a much better setup.


HKS-type-S-intercooler-kit-installed.jpg


Ended up taking it for a drive on Monday, left the boost controller on low just to be safe. Low boost was set at 14psi previously, and with the new intercooler it's pumping out 20psi! Crazy how much restriction the old cooler setup made. Pulls like a freight train now too which is great. Also feels less laggy too, win win win!

So thank you for all your input lads :D

Edited by Run-It-Hard

I will need to get it on a dyno soon, needs rego first though (ran out lol).


I ended up finding a HKS type S intercooler kit in Japan and got it sent over. Neat bit of kit, managed to get the return up nice and high too with a bit of moding so I'm all smiles :D

by the end of the day will be interesting to compare:

RB20 RB25

TD06-20G. 8cm 12cm

Cams Std 256/8.5 Tomei

Fuel E85 E85

Both engines run the same inlet and exhaust manifolds. As it is an R32 RB25 it does not have NVCS will be interesting if the better breathing hot side, bigger cams and bigger engine will result in more power then I was making on the RB20

I'll take a punt and say that the 25 won't wake up down low with the bigger housing, but should shade the 20 between 4-7000. Will be an interesting comparison.

8cm and you reckon it was lazy down low?!

Do you think that's because the turbine was choking at the lower shaft speeds (in that tiny housing) or a different reason?


A 20G shouldnt be lazy down low, especially with an 8cm hey..

I had a 12cm on mine for a month, was so bad lol.


TD06-12cm-tune-RB25-dyno-sheet.jpg

Although it could have had better response with my new cooler setup. Cams might help it out too, dunno. Trent's set it plenty of times that he loved his, he had cams too.

▲ id have to agree! mine had an 8cm rear on rb25 and was way lazy down low..12cm i think will make it more doughy and i dont think up top with that much of an advantage

LOL...really? Something very different between our setups then. I was hitting 18psi at 3,200rpm or something stupid and show was over with the thing losing its pull over 6,500rpm. It was mega grunty with the 8cm housing. And that was with cams at 0 and only a 2/3 tune.

I like the way the 12cm drives but on a very rough tune with no ignition the 12cm housing has generally added 800-1,000rpm to response. Would be far easier and nicer to drive with the way it delivers its power.

Will see if we get any of theloss in response back with the changes we made today....the car got pulled off the dyno due to another car needing some urgent work.

Will keep looking for a 10cm housing but think the T67 will go on before a find the right sized housing for the 20G. That will be the real test as I am pretty sure we have maxed out the compressor on the 20G so the question is will the billet wheel flow more with the TD06-12cm vs the T67-25G 10cm . That will be the real interesting test. Smaller, lower flowing turbine with a 78mm cast compressor wheel VS a larger higher flowing turbine with a lighter, smaller billet 73mm compressor with the larger 12cm housing.

I would go straight for the proven 10cm if I had one so ...no other choice then to waste tuners dyno time with my games :)

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