Jump to content
SAU Community

Recommended Posts

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

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • In the context of cam 'upgrader' I mean generally people who upgrade headers/cams - not my specific change. I mean it makes sense that if I had a bigger cam, I may get more false lean readings. So if I went smaller, I'd get less false lean readings. To a point where perhaps stock.. I'd have no false lean readings, according to the ECU. But I'm way richer than stock. My bigger than normal cam in the past also was giving false rich leanings. It's rather odd and doesn't add up or pass the pub test. Realistically what I want is the narrowbands to effectively work as closed loop fuel control and keep my AFR around 14.7 on light sections of the map. Which is of course the purpose of narrowband CL fuel control. So if I can change the switch points so the NB's target 14.7 (as read by my WB) then this should be fine. Haven't actually tested to see what the changed switchpoints actually result in - car needs to be in a position it can idle for awhile to do that. I suspect it will be a troublesome 15 min drive home with lots of stalling and way too rich/lean transient nightmare bucking away for that first drive at 2am or whevener it ends up being. Hopefully it's all tune-able. Realistically it should be. This is a very mild cam.
    • Messing with narrowband switchovers is a terrible bandaid. I don't want to think about it. You are a cam "upgrader" only in concept. As you said, your new cam is actually smaller, so it's technically a downgrade. OK, likely a very small downgrade, but nevertheless. But the big thing that will be the most likely suspect is the change of the advance angle. That change could be equivalent to a substantial decrease in cam lobe duration. I haven't gone to the effort of trying to think about what your change would actually cause. But until someone (you, me (unlikely), Matt, someone else) does so and comes to a conclusion about the effect, it remains a possibility that that is the change that is causing what you're seeing.
    • The previous switchover point was 501mv. The stock value is like ~360. They now were idling at about ~880. The thing is, most people get a false lean condition. I am getting false rich conditions. This isn't a quirk of terminology, most cam upgraders get awful fuel economy because the O2's read false lean and add fuel - Mine are attempting to aggressively subtract fuel.
    • So... the whole idea was to upgrade the power of the motor from stock. The motor I bought with the gearbox had 'some' stuff done to it in the past, but it wasn't as well thought out/what I had wanted to do. The stock heads typically are a big restriction on LS's and need porting to unlock quite a lot of power. You can then go a bit silly with aftermarket castings to get more, aftermarket intake manifolds for a little more, and then porting those for more. <- We are here. Nobody in Australia really goes down this path (for some reason). It might* make 3kw or something more than doing things the tried and true path for 10X the cost. So that's probably why - I wouldn't even recommend it to people, the money was and is likely better spent on just CNC'ing the stock heads and putting a 6.3L stroker kit in. I didn't want to go down the 'normal' path and then think: But if I'd just done a bit more - I could have had a slightly better result. I assumed the heads were running out of flow and it always annoyed me - Turns out the previous installer advanced the cam 6 degrees so this is likely why it was coming on earlier and running out of puff earlier than advertised. The body panels were just lack of planning/no information on this anywhere on the internet and the fact they came out different was annoying. From test fitting the guard it appears I could have gotten away with GTR guards only, but I got the bonnet and raisers and everything else as well for a pretty decent package deal.
×
×
  • Create New...