Will Lowering My Boost Help?

[dan.1337]

I have a really n00b question.

If i drive 80% of the time off boost (<3000rpm), will lowering my boost help with fuel economy?

imo, i say no. but then again, i'm not actually sure.

Can anyone enlighten me on it?

Thanks!

Edited June 25, 2007 by dan.1337

[HackerX]

more air + more fuel = worse economy.

Long answer - Probably not much, and there are lots of factors involved

Short answer - yes.

[RBwhatever]

Not by much. Depends if you even hit full boost anyway.

[dan.1337]

I'm just thinking that when I'm off boost, it drives like a normal 2L engine (rb20) and when on boost, that's when the air + fuel etc come in.

Is that true? Or when I'm running below 3000rpm the turbo is still spinning and pushing air into my engine?

If anything, when I'm giving it stick it's between 4000-6000rpm but i'm not sure if I'm on full boost during that time as I'm too busy watching where I'm going and not my boost guage.

I was told that my dropping my boost pressure below 10psi, I'll get better fuel economy. Right now, i'm running 16pounds.

If it helps, here are my mods:

rb20det

HKS 2535

550cc injectors

Link ECU

Bosch 040

cooler, pod, 3" full exhaust.

i'm currently getting exactly 300km to the tank.

Edited June 25, 2007 by dan.1337

[RBwhatever]

I'm just thinking that when I'm off boost, it drives like a normal 2L engine (rb20) and when on boost, that's when the air + fuel etc come in.

Is that true? Or when I'm running below 3000rpm the turbo is still spinning and pushing air into my engine?

What? No. If your not boosting then the turbo is not pushing air into your motor. It depends how you treat the throttle whether you get good or bad economy.

[dan.1337]

Thats what I thought. If I'm not really pushing air into my motor (<0 on boost guage), then lowering my boost will not help. Almost all my shifts are below 3000rpm unless I need to overtake those new trams. Damn they're fast.

hmmmmmmmmm

What? No. If your not boosting then the turbo is not pushing air into your motor. It depends how you treat the throttle whether you get good or bad economy.

[R31Nismoid]

If your getting 300, its one of two things

1. Crap tune

2. Your right foot is too heavy.

If you mash the pedal, or near enough to 3000rpm and back off, its going to use fuel. Nothing you can do about it

[dan.1337]

I forgot to add, if it matters, about 50% of my driving is in peak hour traffic.

[barney2010]

you want better economy but you have a bigger fuel pump, bigger injectors and a after market computer, all of which help get more fuel through, then u ask if u wind the boost down will you get better economy even tho your not boosting. sorry to say but u don't buy a skyline to get fuel ecenomy of a excel

[sinistaGTR]

hey i get really good economy outta 700cc inj bout 400-500km and thats rb25 gt3040, q45afm etc.

its just a crap tune get it retuned. also what injectors are they cause if there rx7 ones then they uise heaps of fuel. Also turnin down the boost wont help if you drive off boost as its not like your driving on full boost all the time.

[dan.1337]

i'm not looking for the economy of a prius or excel. definitely didn't buy the car to save the world. just thought that 300km to a tank is a bit low, i'd even be happy with between 350-400 which isn't all that far away from what i'm getting now. just unsure why i can't sqeeze out that extra 50-100km esp when i'm driving off boost a lot of the time.

my injectors are Denso 550cc. direct drop in for the engine so i don't think they're from an rx7 (unless i'm wrong).

my car was tuned recently. it used to run extremely rich (almost on the verge of flooding the engine) and everything on the inside has been blacked out with carbon deposits. i was told by my tuner that over time the crap will be spat out of the system and economy should improve again. i don't think he's a crap tuner as one of my friends who has had his tuned by the same guy with almost the same mods gets 400 to the tank each time.

i might go thru a couple more tanks of petrol first and see if things get better. each time i drive little black spots of carbon which have been softened by the exhaust condensation is spat out (quite a lot of it) - so i know that something is heading in the right direction.

will be holding off on the ebc for a little while.

thanks for the all the insight tho!

[paulr33]

boost doesnt use fuel, the driver and the tune do

[tridentt150v]

If your getting black crap out the exhaust and you say it could be coming from the engine, I wonder what your cat is doing = coughing up fur balls??? Could be wheezing??

[xRHETTx]

Maybe get a new oxygen sensor, and if that doesn't help get the ecu retuned. Get the workshop to spend a decent amount of time on the lower load points etc to improve your economy.

[sinistaGTR]

maybe get a new cat or bash your old one out might help too free the engine up a bit

[paulr33]

i suspect the link doesnt do closed loop so an oxygen sensor wont do squat

you should confirm with your tuner if it supports closed loop 02 feedback or not

if it doesnt get it tuned for light cruise / low load or change ecu's

if it does, then get the 02 sensor checked/changed and or get the afrs for light cruise trimmed

also drive normally, dont back on/off throttle constantly to raise boost and make boost nosies

another idea is your get your gf or mum / dad to drive your car, see what economy they get in it - i bet its much better than what you get