poor fuel economy. j-spac vr4, 3" tbe, bov only mods

[mannynz]

It a bit unfair to compare a VR4 fuel economy to a skyline.
VR4 engine drives the 4 wheels all the time every time.

Also check your engine condition like its mileage, cylinders compression, wheel aligments, ....

 

[milkandoj]

I haven't read the thread to check but the answer to this is simple.

A J-spec (prefacelift) vr4 running 11psi of boost with very minor mods should return around 460km/tank with average amount of leadfoot. You can drop it to as low as 260 if you are HEAVY on the pedal.

Your O2 sensor is probably shot = rich all the time = fail on fuel economy. Get a mate to drive behind you and see how much black shit is shot out on boost. Should only be a puff as you HIT boost, not constant. O2 sensors are always the culprits.


My jspec prefacelift used to return consistent 10.2L/100km city, 7.1L/100km country with exhaust and 11psi boost. No other mods. Anyone who's seen me drive or been in a car with me knows I don't drive like a grandma.
________________

Well i just went for a drive behind while the old boy drove her;
it blows smoke through the whole gear not when just comming on boost, isnt billowing out the back however, ive seen worse on some dodgy looking 180s ect.
Its like a constant hazy smoke (doesnt look white, looks dark tho hard to see with the sun).
And it smells to, doesnt smell like oil or reak of raw fuel but it smells.

Still prob the O2 sensor?

This tank looks lik im gonna get closer to 380km to 400km from 60L (15-16L / 100km). only boosting off the odd set of lights or corner tho, mostly cruising right off boost.

Bit better than the first tanks 320kms (18.8L/100km)

 

[CLuTZ]

Get a datalogger and see if your 02 sensor is spitting out the correct voltage

 

[Entaran]

Sounds like a shot O2 sensor to me. Dataloggers are your friend, try one of those first

 

[milkandoj]

Cheers, where and how much. Wasnt it somehitng like a palm pilot?

ivr read about them but cant remember wherer, im up to the 15th page o this forum lol... does it have a serch feature i cvaant see it? i know its a stupid Q'ion lol

 

[ozyvr4]

Fuel economy is all about tunning. I have a DSMLink ecu upgrade. I run 20psi all day, with 660cc injectors, AFPR, big 16g, evo 3 manifold, 3' exhaust, walbro pump, and a few more mods. I get 450klm around town & 600klm on the open road. I still think I can tune a little more out of it. A performance car can still be economical. Obiviously if you drive flat out all day that you will be able watch the guage go down.

A simple equation- horsepower = air & fuel. The more the better.

 

[JAP63]

Well i just went for a drive behind while the old boy drove her;
it blows smoke through the whole gear not when just comming on boost,
Its like a constant hazy smoke

Normal...
exactly what mine did..its o.k,your expected to run rich,the ecu wants to,its programmed to,and for safety reasons it should.

That smoke you described is exactly what my car did,i half think it was a bit of mixed blowby as well..but dont forget the '63 is a dirty motor,standard they have black smoke and unburnt fuel pouring out of them,just look at any e3 with a full exhaust and a bit of boost...anyway...

Youd be suprised whats acheivable, driving the car soft,i did a full tank like a grandma and i got over 550k..normally i seen around 380 k,and that was with an s16G and 15 pound driven like a maniac at most times,which i feel was reasonable economy..

An aftermarket computer tuned to the n'th degree may save you some fuel,but if your car is standard...why bother...its an exercise which wil cost thousand,that nets you a weekly saving of only dollars.

 

[milkandoj]

Normal...
exactly what mine did..its o.k,your expected to run rich,the ecu wants to,its programmed to,and for safety reasons it should.

That smoke you described is exactly what my car did,i half think it was a bit of mixed blowby as well..but dont forget the '63 is a dirty motor,standard they have black smoke and unburnt fuel pouring out of them,just look at any e3 with a full exhaust and a bit of boost...anyway...

fair enough

Youd be suprised whats acheivable, driving the car soft,i did a full tank like a grandma and i got over 550k..normally i seen around 380 k,and that was with an s16G and 15 pound driven like a maniac at most times,which i feel was reasonable economy..

An aftermarket computer tuned to the n'th degree may save you some fuel,but if your car is standard...why bother...its an exercise which wil cost thousand,that nets you a weekly saving of only dollars.

again fair enough reason im not liking it is,
* im running the stock smaller turbo than what you were.
* as far as i know it should be running stock boost (i just bought a boost gauge on ebay).
*not driving like a maniac all the timeand im only gonna get 18l/100km from this last tank same as last one (330kms from 60L, last tank was 320kms) again and this tank i drove like a granny keeping below 2000rpm say a third of the time.

So whys mine so bad lol

Where do i start? shall i start by trying data logging on a palm pilot to see if my O2 sensor is bunged if im getting weird readings from it and replacing that might help me correct?

 

[matress]

I think your biggest problem with fuel economy has got to do with the "VR4" bit! :lol:

I think I drive pretty sedately and I get 250km out of a tank. I get about 350km on the freeway.

My car is a bit more modified with yours, but I've found that my modifications have never really increased the fuel consumption of the car. It's always been around 250-280km per tank.

 

[milkandoj]

ive got an '87 model pre face lift jap spec, from reading some threads i gather its a dual board ecu thats not data loggable.

so where does that leave me, shal i just buy a new O2 sensor and hope for the best, that it tidys up the fuel?


And if you fuel consumption has never increaced over your old set up, does that mean somehitng is still different compared to people that get 460kms form a lighly modified car?

 

[milkandoj]

ive got an '87 model pre face lift jap spec, from reading some threads i gather its a dual board ecu thats not data loggable.

so where does that leave me, shal i just buy a new O2 sensor and hope for the best, that it tidys up the fuel?

I think your biggest problem with fuel economy has got to do with the "VR4" bit!

I think I drive pretty sedately and I get 250km out of a tank. I get about 350km on the freeway.

My car is a bit more modified with yours, but I've found that my modifications have never really increased the fuel consumption of the car. It's always been around 250-280km per tank.

And if you fuel consumption has never increaced over your old set up, does that mean something is still different (not working properly) compared to people that get 460kms form a lighly modified car?

im trying to figure why some ppl get good k's per tank while other get bad, reading posts ppl seem to gfet good and bad fuel on slighly moddified cars while other dont.
it must come down to tuing or dodgy sensors as some have said, so where to next....

 

[ozyvr4]

Matress-- aren't you worried about that milage. You have gone from a car that in standard trim 550klms per tank to a modified version that at most getts 350klms. If your only driving sedately the car should make close to the same milage. The car will only use more fuel when you are on boost that exceeds the standard specs. I have mates with low 12 second V8's that get better milage than that. Have you had that thing tunned lately?

I would pissed off with that sort of milage.

 

[milkandoj]

Ok some of my posts are over the place so ill bring it back a bit..
Considering these replys (thanx ppl) and what ive reads from searching the forum;

A stock to mildly modified vr4 (exhaust, 16G, chip, walbro, 15+psi) should get close to 10 litres per 100 km when highway cruising.
I can easily get over 400 km per tank when doing Touring Road events (which is mainly "spirited driving" and full noise during the performance tests).

If you are getting less, and it bothers you, then you have to start looking at the possible reasons why the ecu is dumping fuel in.

A J-spec (prefacelift) vr4 running 11psi of boost with very minor mods should return around 460km/tank with average amount of leadfoot. You can drop it to as low as 260 if you are HEAVY on the pedal.

Your O2 sensor is probably shot = rich all the time = fail on fuel economy. Get a mate to drive behind you and see how much black shit is shot out on boost. Should only be a puff as you HIT boost, not constant. O2 sensors are always the culprits.
---

My jspec prefacelift used to return consistent 10.2L/100km city, 7.1L/100km country with exhaust and 11psi boost. No other mods. Anyone who's seen me drive or been in a car with me knows I don't drive like a grandma

A couple typical culprits for bad fuel economy:
A dud O2 sensor,
A dud water temp sensor.
Bad economy when "on boost" is usually due to intake leaks (and slightly due to the overly rich fuel mixtures programmed in the ecu).

Ok so now i have a few things to check, how do i start, i know a bit on the theory side of things, but not much of the practical i.e how to diagnose problems, this i have to learn.

-So how do i figure out if my O2 is stuffed (i got an 87 i presume- with duel board ecu and cant data logg). Is it worth spening the cash on a single board ecu or is there a better way?

-How do i know if my water temp gauge is stuffed and how will this affect the ecu? It does idle on 1500rpm when starting up cold and takes longer than say the family magna to heat up and drop the revs. I assumed this to be normal or is it the indication of a fault?

-how do i check for intake leaks? i know water and soap checks for leaks but whats the mothod of blocking off the piping and pressurising it ppl have used?

Im the mean time ill keep searching and reading :lol:

Cheers Gerard

 

[rob323]

No you won't be able to datalog on your car .

To check the o2 sensor, you can either replace it with a new one, or one known to be working, or buy a little mixture meter kit from jaycar. That will tell you if the o2 sensor is oscillating correctly (and with enough voltage swing) and whether the ecu is going into the correct mode (either "open loop" or "closed loop" - can't remember which is which) when cruising. Or, buy or borrow a afr meter gauge and tap that into the o2 wire. It will tell you the same info as the Jaycar kit.

With regards to the water temp sensor, the manual does tell you how to test it in hot water using a multi meter. If the manual isn't available on this site, it is on the www.galantvr4.org.au site. Or, replace it with one that is know to be working.

For pressurising the intake, look in the "intake" section of www.vfaq.com for intake tester.

You might spend alot of time chasing down intake leaks, these will not really affect economy when cruising, only when under boost which is usually not alot of the time.

Another cause for crap "Cruising" fuel ecomony might be dirty or clogged injectors. If the above things don't help much, then it certainly won't hurt to pull the injectors out and have them cleaned and flowed.

Also, check that the catalytic converter isn't clogged up.

If your car takes a surprising amount of time for the temp gauge to show it has warmed up, it might be time for a new thermostat. This could also be causing the ecu to run a bit richer than normal as it thinks the motor is not up to normal running temp.

There are a stack of things which could be causing your fuel consumption and it will take time to work through them all and eliminate the possibilities before you find the culprit.

When you are working out your litres/100 km ratio, are you using the number of litres that you actually put in the car when you fill it up, or just running it til the fuel light comes on and assuming that is 60 litres?

 

[milkandoj]

cheers rob 323.
I got some stuff to work with there.
Im regards to ya question about how i work out my fuel i work it out based on the kms for that tank on trip metre and how many litres i put in it. im not assuming its 60litres just because fuel light comes on.

Totally unrelated
IM waiting on my boost gauge lol prob come after the w.e coz i wanna take out the Boost Control Solenoid restrictor, to raise the boost, but ill wait till i can see my boost first. waiting waiting waiting

 

[JAP63]

I remember someone on here a while ago had either a faulty plug/sensor,or the plug/sensor that was on the radiator was disconnected or broken,somewhere along them lines...and they got really bad economy..i think it was LETSGO..i cant even remeber if it was T4G or ClubVR4..it was years ago

You guys are saying water temp sensor,this might be the sensor im reffering to,it was a standard car,and getting around 200 k from a tank from memory.

i remeber as the car thought it was not up to temp,and ran cold start injector pulse widths (rich) all the time,or something like that

jamie.

 

[Entaran]

All the answers you need are in robs post including how to check them.

Time to go off and start ticking them off, report back when you're done

No point talking any further about it.