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Instead of starting a new topic i thought ill post the question in here.... how is everyones fuel economy with the rb26/30 and 25/30 setups? mine is using alot of fuel and cruise ratios are spot on 14.7 and even when babying it around im lucky to get 300km to a tank which is shocking. Im yet to get the cam timing spot on until it goes on the dyno but hoping this is the issue and it will get alot better. I am running 4.3 diff ratio which means its on 2700rpm on the freeway at 100kmh and with the 3076r on it, its just a touch of throttle from being on boost, im thinking maybe the turbo is abit small as well which doesnt help?

So how many km's are you guys getting from a tank and what turbo are you running?

it could be done with internal gates, but an engine thats going to support 2x GT30's reliably isnt going to be cheap to begin with. why skimp on the turbo setup?

only reason is the stealth factor and engine bay room. however am worried bout boost issues...

you wont be able to hide twin GT30's. it just takes up too much space.

stealth comment was refering to the noise when the externals open up...

and gt30's taking up too much room....well no shit, so my original question still stands...can i fit in externals lol ?

  • 4 weeks later...

soooo my motor sounds like a bearing has gone for a little vacation...

was going to throw a wrecker motor in there, but i figure that for around the same price i could do a 3.0 with new cast pistons.

planning to use the 25 oil pump and throwing in some restrictors and a baffled sump.

with a 25/30 you tend to lose vct yes?

car was making 285rwkw on pulp with 20 psi by 3400 with an HKS 2835 pro s

would i be right in assuming that i would acheive full boost by 3000 or even a little less with the 3.0?

also would i be able to get close to the same power on less boost? say 1 bar?

xxx

soooo my motor sounds like a bearing has gone for a little vacation...

was going to throw a wrecker motor in there, but i figure that for around the same price i could do a 3.0 with new cast pistons.

planning to use the 25 oil pump and throwing in some restrictors and a baffled sump.

with a 25/30 you tend to lose vct yes?

car was making 285rwkw on pulp with 20 psi by 3400 with an HKS 2835 pro s

would i be right in assuming that i would acheive full boost by 3000 or even a little less with the 3.0?

also would i be able to get close to the same power on less boost? say 1 bar?

xxx

lose VCT? no you do not have to, you can run an external oil feed or do the internal mod (there is a thread in this section dedicated to it)

GT3076 turbos come on hard around 2500-3000rpm expect similar though you may find its slightly on the small side for a 30

less boost and same power? possibly hard to say how different it will be untill its been done. i haven't seen a 2835 powered 30 before but take a look at AL's setup taking the advantage he has with manifolds/head work the response should be similar.

vct is easy, no way you should lose it.

http://www.skylinesaustralia.com/forums/topic/251669-rb2530-rb30det-vvt-internal-oil-control/

with this setup and 25 pump i used 2x1.6mm feeds, worked out to ~20-30% (cant remember exactly) less flow then the standard 25 setup with the vct feed.

standard 25/30 comes out at around 8.3:1, compared to 9:1 for rb25, so you'll lose a little compression but this is obviously outweighed by the extra cubes. 3000rpm sounds about right tho

should be able to make the same power with less boost, but how much less is anyones guess. probs still need more than 1 bar tho

just thinking that with the more cubes that the turbo might be a little prone to creep... spose i'll have to wait till it's built and see ;)

i need to do this on the cheap side unfortunately otherwise i'd just go fully forged.....

at the moment my only option is rebuild my current 25 as stock, drop in a kinder surprise or go a cast build...

i figure that a cast built bottom end will be the strongest of the options ad while doing that it might as well be a 30

are you getting trent to do it? he should be familiar with what needs to be done. dont forget about costs to modify exhaust + intercooler piping etc. there are hidden costs to the 30 that you just dont think of until you run into them

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