RB20det fuel economy.

[Skym]

higher lph fuel pump = higher fuel rail pressure = more fuel through injectors. Adjusting adjustable FPR helps to drop or raise fuel rail pressure.

Look at this dyno graph on RB20DET with bigger 300lph Bosch Motorsport 044? fuelpump, bigger turbo (stock R34 turbo), podfilter, full 3 inch exhaust from back of turbo, bigger intercooler with 14.4psi and stock FPR -

http://i701.photobucket.com/albums/ww20/waz-72/chip.jpg

It actually peaked at around 16psi (lower rpm's), then dropped off. I think stock BOV was leaking.

Note the engine runs richer at higher rpm's (set to speed on that dynograph) on first dyno plot (blue). After retune (red plot) engine is running a leaner A/F ratio at higher rpm's.

Without fuelpump upgrade (stock 135lph fuelpump, stock 259cc injectors, stock FPR), 12.1:1A/F ratio at peak hp with 14.1psi of boost -

http://i701.photobucket.com/albums/ww20/waz-72/dyno168.jpg

Here's a dyno graph with stock turbo, stock intercooler, stock ECU tune, with podfilter, exhaust at 18psi -

http://i701.photobucket.com/albums/ww20/waz-72/graphskyline.jpg

Use this formula to get rwhp -

rwkw x 1.341 = rwhp

I don't know how much boost you'll be running, but it runs richer with bigger lph fuelpump and stock FPR (300lph), even with 14.4psi of boost.

Bosch 044 Motorsport fuel pump -

http://www.rx7store.net/product_p/bosch044.htm

[speed]

so i guess i should be changing the o2 censor on my R33 then since ive been getting a bad fuel mileage on mine, on a 3 quarter tank i tested it out and i just barely got 200k, would it be cause of bad spark plugs or o2 censors????

[love_boost]

could be a mixture of both, also the maf should be cleaned and resoldered. it has a small deal to do with fuel metering.

also if the CTS is bad it will make the computer think its still in warm up mode (open loop) which will make it run richer since the o2 sensor is not used to fine tune the AFR's

[sullivanracing06]

you drive in third every were you go???

[DreadedFist]

you drive in third every were you go???

I never get above 4th gear in town, and that's running up to 90-95kmh on the lougheed hwy and what not. If I'm under 65k's, I'm in third gear, just because the engine feels so much more understressed and happy to be alive than driving around lugging it to death..

[Brando13]

I've drained my GTR tank in a little under 5 hours..... Damn girls in an intrepid thought they could lose me. Anyway I'm installing larger injecters since all 6 of mine leak from the body of the injector. So I would need a larger fuel pump and adjustable fpr to run 750cc injectors right?

[Skym]

Speed, if you have bad fuel economy, o2 sensor is usually the cause. 02 sensor voltage slowly fluctuates when it's clogged (stuffed), so needs to be replaced. There's a test for this, where you hold engine at 2000rpm or so and see how quick o2 sensor voltage fluctuates between lean, rich. Slower than certain amount of seconds (I forget how many seconds) = o2 sensor needs to be replaced and is usually checked / changed every 40,000-60,000km or less km if you do lots of short trips.

Stock ECU has lean, rich triggers (in milivolts) and if o2 sensor voltage goes rich (engine goes rich) and voltage that's sent by o2 sensor hits set lean trigger voltage on ECU, the ECU makes engine go lean and vice versa if engine goes lean with rich trigger. When o2 sensor is stuffed, it tends to fluctuate slowly voltage wise or doesn't fluctuate if it gets really bad and ECU runs engine richer, so uses more gas.

Spark plugs can be small part of fuel economy problems and should be changed every 100,000km (street use) if they are platinum spark plugs (stock are platinum i.e PFR6A with 1.1mm gap for RB25DET). With intake, exhaust, PFR7A (colder sparkplug) with 0.8mm gap. Or if you race your car, you'll probably change sparkplugs alot earlier.

Brando, stock FPR is ok. But when stock FPR gets old it plays up and engine can go lean, so sometimes it's best to replace the FPR (if stock FPR has done high km) with bolt on adjustable Nismo FPR for piece of mind when upgrading injectors, fuelpump.

Checking stock FPR is simple, as you plumb a fuelpressure gauge on fuel hose between fuelfilter and fuel rail. Then see if fuel pressure is at 35.5psi or so for RB26, RB20 at idle with FPR vacuum hose connected. Disconnect FPR vacuum hose and see if fuel pressure rises roughly 7.1?psi or so. With vacuum hose disconnected on FPR, it should be the same fuel pressure as before starting engine (0 vacuum reaching FPR before starting engine and when fuelpump is primed).

[speed]

SKYM- thanks for the advice ill be changing those, the o2 sensor is the one on the engine bay on the passenger side (btw its a rb25det) would that be the same problem? sensors is the same as 300zx tt

[floger70]

i drive my gts-t everyday in the summer and i drive usually 2 hours a day on the highway at least to school and back in the fall and spring and i can get about 460kms to a tank of supreme fuel. driving it reasonably. few pulls and maybe limiter once but for the most part normal driving.

[speed]

Was ur car detune/tune ? Thatt ur getting 400 over km a tank?

[Chewy]

if you're doing about 360+ I'd say you're in the good.

I run about 400/tank on an rb20, stock injectors, r33gtr fuel pump, rb25 turbine @ 1bar, driving about 80-120 km/h on average for that mileage.

all city I'd say more like 370 ish.

A wideband won't help unless you have some way to tune as well.

[M13]

with a slight vac/boost leak, I am now doing 250km/ 30L, or near 500km/tank.

Mind you this is with occasional boosting at 16PSI, 60% city driving and 40% hwy.

I can't wait to fix my leak this summer, push up the boost and see how the mpg goes.

I've improved my MPG from winter (a lot of cold-start and cold-enrichment map due to engine being so damn over-cooled)

I am happy now haha.

[Godzooky]

I average between 375-450 on a tank - only mods are intake/exhaust/intercooler/walbro 255 fuel pump.

Also, what's the max volume of our tanks? I thought it was 12/13 gallons but I managed to put 14.5 in today which I think is too much and maybe the gas station ripped me off!

[M13]

I average between 375-450 on a tank - only mods are intake/exhaust/intercooler/walbro 255 fuel pump.

Also, what's the max volume of our tanks? I thought it was 12/13 gallons but I managed to put 14.5 in today which I think is too much and maybe the gas station ripped me off!

60L is on GTS metal tanks.


Which is roughly 15.7 Gallons when converted at 1G = 3.8L (I dunno which one is american gallon, it's prolly larger)

Anyways, I never fill 60L at once. Too much fuel and sometimes slosshing around up the filler neck, etc. I do bursts of 20L or 30L's.

[actionbstard]

well actually a good way to save fuel is increasing spark.has really good effects on fuel economy.