V36 Terrible Economy - Would Tranmission Firmware Or Fuel Tuning Help?

[Haxorz]

Hey guys,

The economy on my 2007 V36 SP Coupe is pretty terrible. I get between 13.3L / 100kms (mostly hwy, some city) to 17.4L / 100kms (inner city driving). I think the best ever (100% hwy) was around 12L / 100kms. I'm a mature driver too, I don't really fang it around.

Always run 98RON, 90% of the time BP, sometimes Shell. Other than economy car goes well.

Has anyone had any experience in doing some fuel tuning to increase economy? (i.e. like one would with a Power FC or Super AFC back my in my turbo days).

Anything else I could investigate?

David.

[Haxorz]

Been thread reading and seems a popular option is the Uprev, either ordered from eBay and DIY or through RevZone in Ringwood.

Can anyone comment on what one can reasonably expect from a stock V36 (with K&N drop in filters)?

Mainly I'm after fuel economy gains (and the switchable map mode sounds great - but I don't have Cruise buttons, could it would with other buttons?)

[Jeremy1607]

My best fuel consumption so far was 570km to the tank (about 70L) with mixed driving, city and freeway, so that's around 12.2L/100km.

I have short ram intakes, hi-flow cats, cat-back exhaust, grounding kit, new spark plugs, splitfire coilpacks and UpRev tuned.

[sonicii]

Would be better to get any problems fixed before you think about a tune. Those figures seem quite high.. I am not sure what is normal for the V36, but they are far higher than what I get in my V35.

[Haxorz]

Does anyone know the best way to go about sorting this out?

I do service the car at a very reputable mechanic (TruTrack North Melbourne) and it's recently had brand new spark plugs and air filters cleaned. Tyres are near new too and I regularly check the pressure.

[colin.ssc]

When I was working in the city, my usage was about 13-14l/ 100kms...peak hour traffic + city...you wont get good economy out of these engines considering they are pretty high revving. But your consumption does seem to be on the higher side of things. Not too sure how bad the traffic and city driving is like in Melbourne though. 100% hwy (assuming 100-110km/hr and going into the country) should get low 11s or even high 10s.

[Haxorz]

OK. So I just called around two performance workshops here in Melbourne.

They both mentioned the O2 sensor is the most likely culprit, especially in a 2007 car. The ECU doesn't get accurate readings so it overcompensates by dumping fuel. Hooking it up to a scan tool would easily ID if this is the problem ($80). Strangely, one of them recommended a Dyno to check A:F ratios and the other said it would be a waste of effort (as they want to check the car at 'cruise', not at full throttle).

Could this also explain some weird idling / low speed 'lurching' I've been experiencing? What are the common symptoms of a dodgy O2 sensor?

Edited November 10, 2014 by Haxorz

[Haxorz]

I've done a bit of Googling and yes, a dodgy O2 sensor will cause the car to 'surges, hesitates, skips and bucks.'

I reckon this is it. Will report back in the hope to help others

[colin.ssc]

Which O2 sensor though? Think theres 2 sets on these cars....(I think)

[sonicii]

I had a failed AFR sensor (wide band O2 sensor) on my V35, but it only caused a CEL and poor economy, no other symptoms.

I would assume the HR engines also use AFR sensors?

[Haxorz]

@ sonicii - Yes, wide band sensors I believe.

OK, so I just got off the phone with Scotty from this forum (Scotts Customs). He was extremely helpful, knowledgeable and good to talk with - highly recommended for anyone needing any work done.

He reckons it's most likely a oil/dirt build up in my AFM. He says a dirty AFM will give poor economy and rough idling and it's also the only part of the car I've modified (drop in K&N oil based panel filters). He reckons it's a common issue with oil based filters (the wires end up getting covered in a combination of oil and dirty) and recommends I switch to cottom based filters. It could still be an O2 sensor (which a scan should pick up on) or manifold leak as well, but this is the cheapest thing to check/fix first.

Anyway, I'm off to buy myself a can of CRC AFM cleaner and give him a visit

[nickcorr]

My V36 does 8-9 /l/100km on a run and Scotty does know what he is on about, fingers crossed cleaning up both of the AFM's fixes it up.

[KeyGT]

Ditto on the oil filters see if you have any dirt build up etc.

My 2012 V36 gets average 10-11L/100km 60/40 (City/Hwy) and drops down to approx 9/100km on long haul country (110km/hr) trips... But that's just the 7 speed working its magic. Good luck!

[niZmO_Man]

That's great fuel economy (for this type of car). Makes me want to get one even more .

[colin.ssc]

Man the 7spd gearbox does wonders on fuel economy huh....*sigh*

[KeyGT]

Yeh can't complain it is almost exactly the same as my old Lib GT (2.5L turbo) but I spose they were both putting down similar kWs....

[Haxorz]

Alright... an update.

Visited Scotty last night, cleaned out the MAF sensors and checked for error codes with Consult. The sensors didn't look particuilary dirty but given their tinyness and sensitivity it's still worth doing. Turns out it's an extremely easy job on the V36 once you know how (and should be done after air filter re-oil, or better yet, avoid oil based filters).

Consult showed the O2 sensors working well. There were a whole bunch of logged error codes back 32 starts ago when my battery and alternator died and was replaced. These were all cleared to start afresh.

I won't really know if it's help until another 2 weeks or so of driving but I can tell already the car is much smoother on the HWY, like back when I first got it 4 years ago. I thought it might be a placebo effect but my GF noticed the same. I'll monitor fuel consumption and post the results.

For anyone looking for mechanical work in the Melb SE suburbs, I'd like to say Scotty is a great guy, very knowledgeable on the V series and highly recommended!

[scotty nm35]

Thanks.

Hopefully it's all sorted for you, I have never seen that many error codes at once. lol.

[Haxorz]

Thanks.

Hopefully it's all sorted for you, I have never seen that many error codes at once. lol.

Hahaha yeah, I think I got the high score on your Consult!

[Haxorz]

Some good news. I did a big trip up to country Victoria and managed to get just under 700kms to a tank. Calculated fuel economy was 10.1L per 100kms, which is the best it's ever been by a good 100kms at least.

My 'bucking' issue on transmission downshift is still present though.

If you have used oil based filters and have economy issues I HIGHLY recommend you use some MAF cleaner.