Need Advice

[VLRB25DET]

Hello, Names daniel. first time on these forums.. not very knowledgeable on the whole turbo stuff but im not stupid.

ok ive got a VL Calais.. with an RB25DET conversion. 5 speed manual..4:11 diff, all stock atm the turbo has a wastegate rattle. so ive been told.and i want to upgrade the turbo. the exhaust ive got. custom 3inch turbo back, will bolt onto a GT30. but ive been told a GT30 will lagg because it doesnt boost untill like 3500rpm. so a gt28 would be better for me. the only thing i dont know about is the cooling lines. now as i can see theres 3 cooling lines.. correct me if im wrong.. Would i have to block or remove some cooling lines? or would it better to keep the oil and water lines? i dont know. or will it bolt straight on. or will i have to modify the cooling lines to siut the net turbo.. i plan on doing all this myself.. with help from mates obviously.

so has anyone got any ideas? number i can ring to talk to someone about this?

Thanks..

heres wat it looks like

[nizmonut]

dude most big turbo's lag till around 3500, the 28 will only really reduce this issue slightly compared to your current turbo(for example 28's are a replacement turbo for 300zx's) 1.5 litres per turbo...going backwards really.

if your after more response maybe look at a forward facing plenum chamber, similar to what you see on gtr's,

also to improve the turbo response from what you have invest in a stainless steel exhaust mainfold, this will help with exhaust gas flow and will reduce lag

also a aftermarket ecu would greatly improve the power curve.

the cooler you can keep your engine and its associated bolt ons the better, and the longer your turbo will last.

so a oil cooler wouldn't go amiss either.

cams and cam gears are another good one, this can increase the torque down low for more engine generated power rather than turbo induced power.

the combination of free flowing manifolds cam's and ecu will most likley be of more benefit to your responsiveness then just a turbo by itself.

it's up to you ofcourse, its your car and your money but from expierence(owner of nine vl commies including a walky and a HDT brocky) the idea's ive listed above will be of more benefit in the long run as these will allow for big power figures later when you do want to change turbo's.

oh and a foot note, read up on the rb30/25det engine conversion threads...this will greatly improve response and take your vl calias back up to its 3 litre capacity, Shouldn't have any issues mot wise.

my gts4 is running a rb30/26det conversion and is producing 210hp at all four wheels just as the turbo is coming on boost, once in the sweet spot its 401 at all four @8 psi....engine work first 747 boeing later.

good luck

Edited June 12, 2008 by nizmonut

[DECIM8]

Lag until 3500? Id want full boost or close by then..

[VLRB25DET]

thanks for the advice.. but i need to do the turbo before anything. i had a make look at the rattle and he said its the internal wastegate. and its sticking open or closed. depends.. and he said im lucky i havnt blown the engine from over boosting it. so thats the frist on my list.. im not after extreme amount of power. just an upgrade of turbo. ecu, injectors. just to make it decent. not really powerfull. so i dunno wat to put on., changing the manifold wasnt really on my plan. but i have to, to put the turbo best for me on. then i have to..

[skylinekid]

thanks for the advice.. but i need to do the turbo before anything. i had a make look at the rattle and he said its the internal wastegate. and its sticking open or closed. depends.. and he said im lucky i havnt blown the engine from over boosting it. so thats the frist on my list.. im not after extreme amount of power. just an upgrade of turbo. ecu, injectors. just to make it decent. not really powerfull. so i dunno wat to put on., changing the manifold wasnt really on my plan. but i have to, to put the turbo best for me on. then i have to..

well for one if u want good power ur gonna have to sacrifice abit of repsonse to make it...... its how the cookie crumbles

[nizmonut]

oh...start by taking the ac out..theres 15 kw right there.

[VLRB25DET]

oh...start by taking the ac out..theres 15 kw right there.

theres no AC in it.. the compressor is there cuz the guy who did the conversion left it there for some reason. but its off now i took it off last weekend..

[-_-StRyDeR-_-]

15kw taking AC out?? hmm ok.

dont worry about the Forward facing plenum until you get close to 300kw. stock flows great up until then.

a good option would be a highflow 25 turbo, uses same exhuast, lines, manifold, everything.

then get a piggyback ecu (or a stand alone if you want) and get it all tuned. see if your happy with how it feels and go from there.

CJ

o and if the wastegate isnt closeing properly, try slightly bending the arm, its not a FIX its just a bandaid. or just stay off full boost

Edited June 12, 2008 by -_-StRyDeR-_-

[Al]

Another option is a HKS GTRS. I found this to be the best "all rounder" on an rb25. Nice and responsive, yet capable of making 250-280rwkw, depending on other supportive mods.

Or do what i did: Build a strong rb30 bottom end, bolt on the 25 head, add cams, manifold, plenum, etc and attach the smallest recommended turbo; a GT30R. Full boost (currently 15psi) by 2800rpm and will make 300+rwkw. My setup is still in run-in tune, so time will tell how aggressive it gets with 5psi more boost, more timing, better tune and adjusting the cam gears.

Not sure why people swap to smaller capacity engines, sure it's twin cam but cubes count for a lot too. The difference between my current rb30 setup and my previous rb25 setup is HUGE and the engine is still in run-in tune.

[VLRB25DET]

Not sure why people swap to smaller capacity engines, sure it's twin cam but cubes count for a lot too. The difference between my current rb30 setup and my previous rb25 setup is HUGE and the engine is still in run-in tune.

ive got my RB30 turbo engine sitting in my garage.i(f anyones keen on buying it.? got computer turbo and engine. some oil leaks but still in good condition. no loom tho.) but doing the conversion was the cheaper option for me at the time.