Fuel Economy ,with Big Turbo

[GtstCoupe]

just wondering how dome of you guys with big turbos like gtrs's and 2835's go with fuel does it guzzle or all depend on how you drive it, as i am looking for aturbo upgrade but i dont want it to suck 22ltr/per 100kms :lol: .

thanking you

[Tommyk]

It really depends on how you drive it.

While i have a gtr, i do have upgraded turbos. and i can say effectively, that if i proceed to rev it out, such that i am at full boost @ 4500+ rpm in 4th, then it chews petrol like anything. however if i stay on minimal boost at lower revs, it probably chews less than it did standard

[Amaru]

Before I pulled my car off the road, it was running 2530's with about 18psi boost, cams, power fc etc. If I flogged the guts out of it, fuel consumption would be terrible (I think my best effort was 180kms off a fullish tank, about 65 litres).

If I babied it I got pretty good fuel consumption... thats why it became a weekend warrior

Going the big single now, so I expect fuel consumption to go out the window even worse when im giving it a hard time.

[GtstCoupe]

oh this is all very interesting less fuel consuption that standard, i guess because it doesnt have to rev or work as hard to make power or make you move

[Tommyk]

Depends how you drive really

For example, with stock turbos i had full boost around the 3000 or so rpm mark.

So the engine would chew through more fuel because i would be making more power at 3000rpm than with my current setup. Therefore, better fuel economy.

However, At the moment, I am at about 85-90% capacity of my 700cc sard injectors at full throttle/boost, over 6000 or so rpm, so fuel economy goes through the roof

[Freeman]

Yeah i would have thought you would get better fuel economy everyday normal driving as a bigger turbo would be a bit laggier and not making boost until later compared to the stock turbos. Therefore less boost = less fuel used.

A GT-RS isn't a big turbo i don't think...

[Morgs]

I've got a T04Z on a RB26, and its fairly heavy on the fuel. 16-18L/100km at best estimate.... would definately suck a tank of fuel very quickly if you're heavy on the foot. You're looking at significantly less power with a GT2835R/GT-RS so you've got nothing to worry about

Fuel makes power

[gtst25]

All depends on your right foot. I have gone past 400 kays with my new 2835 and economy is normal - that being around the 500k mark / tank no problems.

Driving with my lambda sensor has also made me aware that even out of closed loop I still am getting 14.7 - 15:1 AFR's at these light load load points.From what I've seen the PFC maps seem to deliver great fuel economy

If you boost it up and make it go into higher load points your economy will allways suck.

[Cubes]

With the RB20DET I was able to rev the crap out of it on 1bar of boost all the time and still manage a decent 470km's per tank.

Since the RB30DET has been dropped it it boosts much much earlier, even just driving around on boost with the odd wot every so often the best I manage is 430km's per tank.

This tank i've only managed 370.

I have been stuck in to it quite a bit though.

[R31Nismoid]

ive had 400+ with a GT30.

just stay off boost entirely and light loads, shift before 3000rpm

[sky30]

A larger turbo with bigger exhaust wheel and housing should improve off-boost/cruise fuel consumption.

[paulr33]

fairly moderate driving with stock turbo and i get average around 340k's to a full tank in an r33

[GtstCoupe]

yeah see atm i am geting say 500 or so per tank using ultimate ,and jsut basic mods 10psi, cooler, exhaust, clutch etc.

[krzysiu]

Driving like a grandpa i can manage over 400km to a tank with a larger turbo.

[RB30-POWER]

Unless your driving around on full boost. (Which will be quite difficult to do on the street legally)

You shouldn't really have any fuel cosumption increase.

I mean i don't know about RB26, but on my RB30 i can drive around all day everyday off boost if i want.

[discopotato03]

I think its how your engine makes its torque that has a lot to do with fuel consumption . Others on this site have said power from aditional airflow is the go rather than extra boost .

My idea is to have a reasonably healthy compression ratio (~8.8/9.0) , a head and valve train that breaths well without long duration wide overlap cams . A turbo with efficient wheels and a very good balance of turbine to compressor .

I believe the road to good power and fuel consumption is a state of tune that gives good part throttle torque particularly off boost - in other words you don't need to go chasing revs and boost to get it to go .

I think we can safely say that engine management/cams/turbos and pump fuel has reached the stage where you can have a decent compromise for the road .

In my book things that hurt reasonable consumption are :

1) Gutless low CR ie under 8.0

2) Long period cams with lots of overlap - lack of cylinder trapping efficiency and

reversion .

3) I'll start a fire here , cams as above with single throttle plenum manifolds

promote pressure fluctuation in the plenum enhancing reversion .

4) Turbos that allow much higher exhaust manifold pressure compared to inlet

manifold pressure under boost . It takes crank energy to force exhaust out

through restrictions . Fuel energy generated crank power that could have

been used to drive us down the road . Exhaust reversal back to the chambers

because of restrictions , polutes preheats and drops the fuels effective octane

rating meaning less ignition advance can be used - hurts consumption .

5) Tuning - the method of load sensing and the flexibility of the computer itself is

very important . I'll be going with hotwire AFM's because they have the best

handle on air temperature vs density , I think MAP's a bit crude . So that leaves

me with either std retuned ECU or Apexi PFC , PFC all the way .

Lack of experience of the person tuning it - this hurts at the pump big time .

My opinions only , feel free to change them .

Cheers A .

[gtst25]

Just came back from a 425 k cruise with a lot of spirited driving and a few big squirts - still had just under a quarter of a tank.

[GtstCoupe]

that sounds like good ks i like that

[shanef]

Just came back from a 425 k cruise with a lot of spirited driving and a few big squirts - still had just under a quarter of a tank.

bloody hell, im running a stock r33 s2 with just 4" exhaust (from 3"cat) 10psi boost and power fc and i can only get 360 k's out of it max even driving like a ganny most the time

you guys reckon the big exhaust has somehtnig to do with this or not?

[Cubes]

360kays sounds like you either really get stuck up it ever single acceleration OR the light load cruise etc is totally out of wack, being influenced by the O2 sensor etc..

My 3ltr DET running 12psi and stock rb25det base map (untuned) gets better than yours. :S

Edited November 28, 2005 by Cubes