R34 Fuel Economy - A Different Take On It

[SS8_Gohan]

OK, let's get into a bit more detail here regarding our cars fuel economy. There are A LOT of factors that are at play when it comes to economy obviously, the right foot, traffic, speed limits, urban, extra urban, country, mods, etc...

So it's very hard to compare, but i figure if we break this down a bit, we can see how our cars are going...

For this, i say we measure ONLY how we go for the first HALF of our tank. So fill up when the tank gets to half way, as far as she'll go, see how many litres it takes.

Answers will be in Litres / 100km's and we take note of how many k's we've done when we get to halfway. More accurate than low fuel lights or people's idea of what a "tank" is...

So, a few categories relative to roads travelled and traffic

Category 1:

- Just urban driving

- Mainly 60km/hr driving, a bit of 80km/hr roads

- Not peak periods of traffic

Category 2:

- Just urban driving

- Mainly 60 - 80km/hr roads

- Includes peak driving, "9-5pm" type journeying.

Category 3:

- Just urban driving

- Includes freeway 100km/hr driving

- Includes peak time driving

Category 4:

- Category 3, but freeway travel mainly not peak times

Category 5:

- Combo of urban driving and...

- extended periods of time highway/freeway driving (so 100km+)

- mainly 100km/hr driving

If you think there needs to be more or less, or changed, post away.

Please also briefly note mods as well, so people can compare a bit more accurately again...

I've yet to start the half tank fills, but last tank was 435km's from 48-49 litres, so choose a category, mention briefly mods, and car year, transmission, and your L/100

mine from last tank (from low fuel light to low fuel light, filled up within 1-2 km's from see the low fuel light)

---------------------------------

Category 1

98 R34 GT-T, Coupe, Manual

Full turbo back exhaust, boost controller to about 10psi

Tyres @ 40psi at all four corners

11.3L/100km's.

BP Ultimate

---------------------------------

[Chang]

Me:

Category 2

1999 R34 Gt 2.0, Sedan, Auto, Standard

Tyres at 32 PSI

Alot of start stop, 1/2 urban, 1/2 highway driving.

400-450km's full tank.

12L/100km's

Sometimes am able to get 550+ out of a tank if doing highway driving all the time.

Edited May 16, 2008 by Chang

[SS8_Gohan]

dude, pump those tyres up

oh and add the fuel you use as well, i'm a BP Ultimate user

[Chang]

Local firestone people fitted my new tyres and said 32-34 is a good psi. I'm not carrying any full load either nor travelling at 160 k's +

I'm using BP 95 octane.

[SS8_Gohan]

too bad they don't know anything.

what size rims you got? if they're around 16" rims, put at least 38psi in there. There are only pluses for running higher psi..

-less tyre wear

-less emissions

-less fuel

-better handling (less sidewall flex)

-tyres won't heat up as quick during spirited driving

-better water dispersion

-better braking performance

-all round safer

ask any who REALLY drives cars, gotta go high psi - the old 32psi type philosophy is based around "comfort" not safety or tyre wear.

[Chang]

Not trying to start an arguement or anything but,

FACT,

just because the tyre's sidewall says you can inflat your tyre to a max psi of 40psi doesn't mean you should.

FACT,

factory recommends you inflat 205/55/r16 tyres to 2.2kg/cm(2) which equilates to 30 odd psi. In my case 32 psi is a healthy dose.

FACT,

my car is a daily cruiser, I'm in the current phase where I prefer comfort over performance.

FACT,

considering the guy who works at Firestone has a GT-t Skyline himself, shows he at least is not a complete idiot

[SS8_Gohan]

my tyres can take a lot more than 40psi

factory specs from days gone by are set to "comfort" mode

you would be hard pressed to notice a difference between 32 and 38, but the advantages would be noticed over time

just because he owns a GT-T doesn't mean he knows what the tyres should be at.

do with this info what you will, but tyre placards until only the last few years, are set around comfort, not safety and tyre wear.

[(OO)SKYLINE(OO)]

my tyres can take a lot more than 40psi

factory specs from days gone by are set to "comfort" mode

you would be hard pressed to notice a difference between 32 and 38, but the advantages would be noticed over time

just because he owns a GT-T doesn't mean he knows what the tyres should be at.

do with this info what you will, but tyre placards until only the last few years, are set around comfort, not safety and tyre wear.

I pump my tyres at 34 psi all round. Also the tyres do heat up after driven so the pressure will go up about 2 psi...

[SS8_Gohan]

tyre pressures should be taken when cold, assuming a few extra psi will appear, is not the way to guage how much pressure your tyres have

[kralster]

you must be nuts if you think the higher the tyre pressure the better the car will be.

[SS8_Gohan]

nope, i don't think it's an absolute answer. Of course, it's about finding the right level, which is the optimal contact patch on the road. That's what you're chasing with tyre pressure

My tyres are 265/35/R18's, the lower the profile, the higher the psi. 38-40psi for street, and i run 42 for track.

I didn't know any of this myself, but i've done 2 advanced driving courses and 1 track day with instructors on hand for anytime that you're out. Every single one of them has stressed the tyre pressure point, and no, not just specifically for track.

I'm going to listen to what these guys say over what the 1st year apprentice at the local tyre shop has to say, that's for sure.

Anyways, this is an R34 fuel economy thread, but post up if you have any other car i guess. If you choose a category, we can still compare.

[Chang]

you must be nuts if you think the higher the tyre pressure the better the car will be.

I'm glad someone said it.

I'm going to take this thread further off topic.

For starters you say you inflate your tyres to 42psi on the track. You do know that lowering the tyre pressure will get you more grip by running a larger surface area of the tyre. Try it on your next track day. 42PSI + an extra 2 odd PSI due to heat leads to crappy track times

The so called "Optimal tyre pressure" is normally recommended by the company itself and most on average should be around the 28-32 PSI range or in some cases just above the factory recomendations.

Edited May 17, 2008 by Chang

[some_cs_student]

The so called "Optimal tyre pressure" is normally recommended by the company itself and most on average should be around the 28-32 PSI range or in some cases just above the factory recomendations.

That goes strongly against what people are saying who have *20* years experience in advanced driving courses.

And I know who's opinion I would trust.

32PSI is waaay too low, I wouldn't even run that in my R31 on the street!

Do the advanced driving course and find out, I did high pressures 38 or 40PSI on a wet track for the advanced driving course like everyone else, my stopping times were excellent and absolutely no problems with grip on street tyres in the R33.

The theory remains that unless you inflate it hard (38-40PSI cold) then your not getting full contact from the tyre to the road, if you overinflate then you will wear the middle but thats pretty hard to do, where under inflation is a lot easier.

** This is for the street and I have run them in 17inch 45 profile tyres...

The track / drag strip will be different so I'm interested in people's opinions on it, especially the track

[(OO)SKYLINE(OO)]

tyre pressures should be taken when cold, assuming a few extra psi will appear, is not the way to guage how much pressure your tyres have

Yes, I check my tyre pressure when its cold in the morning and pump it up to 34 all round.

The Front are 235/45/17R

The Rears are 245/45/17R

I find that pumping up the tyres anything above 36psi is a bit to hard of a ride because as I was trying to say before, the psi in the tyre will go up a few psi due to the tyres heating up...

As for fuel economy I have yet to test as I just filled up on Friday and pump my tyres back up to 34 psi (Before it was 32 psi). I believe there will be little difference in how much milage I get in the full tank, as I don't drive my R32 everyday.

But anyway I'll keep a close look on the gauge within the next few weeks.

Edited May 18, 2008 by (00)SKYLINE(00)

[r32line]

Wouldnt it be easier (if you think your car is using a bit too much petrol) to just dyno it and check a/f ratio's?

[Skyline34]

Category 3

12-14L per 100km

SHell VPower 100

Standard Wheels, Front 37PSI, rear 35PSI

Turbo: 9PSI

[philta]

ahhaahh, the high pressure makes a big difference guys, ive got neg cambers 1.5 deg fronts and 2 deg rears. helps abit with the camber wear when inflated around the 38 psi.

on track days i have my rears at 40 and fronts on 36-38. depending on conditions. its a bitch to drive on rough roads though.

Category 3:

fronts 34psi

rear 38 psi (havent check these for 3 months now, lost my lincense )

shit ass nangkangs z2 rears and sumitomo htrz3 fronts (quite like these tyres compared to my bridgestone z3)

F235/45/17 R255/40/17

12.1L/100km

standard turbo running 9 psi.

[colossus]

I've done a few advanced driving courses and they always stress that higher tyre pressures are safer (better braking and handling, less rolling resistence) than the manufacturers recommendation - not to mention more fuel efficient (which is what this threads about). Low pressures are good for comfort and drag racing thats about it.

Only one real way to measure fuel economy - fill up till the nozzle clicks. Reset odo. Drive around as much as you want, dosnt matter if your tanks half empty or fuel light on. When you fill up next, fill up all the way till nozzle clicks. Then divide the number of litres you just put in (its on your docket ) by the kilometres showing on your odo. Crazy that people just go off the inaccuarte fuel light...

My car would be Catagory 2 (full city driving) - R34 GTT auto - 12psi, cat-back zorst, hi flow cat, FMIC, normally get 14L/100kms before the mods. Though after fitting the high flow cat it dropped to 13.3L/100km then with the FMIC dropped to 12.4L/100kms on the last tank. These just may be co-incidences though havn't decided yet.

Edited May 18, 2008 by colossus

[R34GTFOUR]

my car is a daily cruiser, I'm in the current phase where I prefer comfort over performance.

obviously, an rb20de auto in a r34 chasis would be ummm well, lets say leisurely

for the record i run 38psi on the street, 40psi at track meets and low 20psi if at the drags

Edited May 21, 2008 by R34GTFOUR

[gersfan]

I don't really know a lot about this but I have my dads car tyres 16" at 36 PSI and I think higher would be better. After re-filling them I always feel as though I have better handling and grip on the road.

Anyway sorry for going off topic, although most this thread is.