General RUBBISH Fuel consumption, 8th Generation i-dtec auto tourer

Discussion in '8th Generation (2008-2015) [Acura TSX]' started by pauljdh, Thursday 4th Jun, 2015.

  1. pauljdh Club Member ★ ☆ ☆ ☆ ☆

    United Kingdom pauljdh Belper
    Until 2 weeks back I had a 2.2 I-CDTI manual tourer which was returning 52-56mpg (indicated) without even trying.
    I changed it for a 2012 2.2i-dtec AUTO tourer and in the two tankfuls I've got through Im very disappointed at the fuel economy.
    To make it a reasoned statement:
    I buy the same fuel from the same garage
    My journeys are identical in all respects (length, traffic, duration, time of day etc)
    Both cars have immaculate 100% Honda SH.
    So the indicated (car computer) figures are 54mpg (I-CDTI manual) vs 36mpg (I-DTEC auto).
    Known differences
    1. manual vs auto
    2. DPF vs non-DPF
    3. i-cdti vs i-dtec
    4. i-cdti had a stage 1 tune from premier tuning. I claimed an extra 3-4 mpg after the map over
    Allowing for the automatic gearbox loss, even allowing 8mpg, which would be excessive, the later generation car is significantly poorer in fuel burn - surely not something Honda intended?
    So Im thinking,
    • FAHADS tune was more powerful in terms of economy than I allowed
    • The DPF is a big restriction and does nothing for fuel consumption (On Tues HH confirmed that my software is up to date and the filter is holding only 5g of soot)
    • The auto gearbox is poor
    • The 8th Generation is a much heavier car
    • The computer on an i-cdti is optimistic or the i-dtec is pessimistic
    but - the 7th Generation used to outperform Honda's and .govs official figures easily whilst the 8th Generation massively underperforms both.
    I know I need to do a tank to tank calc but everything indicates things are much worse. Tyres are good etc, brakes not binding and nothing reportable on the car
    As soon as Im settled with the car I want another economy tune and a DPF off (currently its been fine) which may help.
    If it doesn't match the official figures from Honda Ill be taking it back for a look see, although it was serviced 3K ago.
    Anyone agree / disagree, any comments or ideas? Those from auto I-DTEC owners especially welcomed!
    Really didn't expect to be going backwards with a next gen car (even allowing for an auto).
    So, apples and apples - 54mpg-8mpg (auto)-4mpg (stage 1) = 42mpg for my I-CDTI and Im lucky to get 36 on an advanced design. Somethings amiss.
    tomwillie likes this.
  2. FirstHonda Moderator Staff Team

    United Kingdom Ed Wiltshire
    Fuel economy does seem to be quite variable on the Accord I-DTEC. You may find this thread interesting...

    Fuel Efficiency - Full Tank: 919 Miles | Page 3

    I had my 8th Generation I-DTEC automatic for 3 years and 45k miles (ish) and never re-set the computer. When I sold it, it was showing an overall economy of 44.1mpg.

    On a long run I got close to 50mpg on a couple of occasions. I found driving very smoothly and gently was the answer - gradual acceleration and use of cruise control on the motorway - but I've been driving only automatic for 25 years, so am very used to them.

    IMHO the auto gearbox was one of the best features of the car - ratios very well matched to the engine, not so many speeds that it was constantly hunting for the right gear, with a 5th gear high enough to give a relaxed drive while still having enough grunt if you needed it without dropping down to 4th.

    I can't comment on a comparison with the I-CTDI as I've never had one. What I would say is that my new 2.0 litre petrol/auto CR-V (much bigger and heavier) is returning 40-42mpg on a run, which has surprised me.

    I'm sure @John Dickson may have some input here, as he has an I-DTEC 8th Generation and has seen some variable economy.
  3. Zebster Guest

    My first thoughts are that you were never actually getting an average of 54MPG from your 7th Generation I-CTDI. In the 7 years that I've had mine the best I've ever had was 51MPG, but my more typical average figure is 44MPG and I know my engine is in tiptop running order (and the rear brakes aren't binding)!

    The on-board computer always reads too high (as you acknowledge) but it is well established (not so much on the TypeAccord forum, but certainly on the Civinfo forum) that both Celtic and Premier remaps result in the on-board computer becoming even more optimistic about the MPG. Most remap customers who calculate the MPG manually (as I have to, as a Sport model owner) fail to find any increase whatsoever in economy (why on earth would they... you don't get something like increased performance for free!). I recall one Civinfo member with a bespoke Celtic remap showed his average MPG to have become 71MPG!!!
    tomwillie likes this.
  4. mikey77 Club Member ★ ☆ ☆ ☆ ☆

    Here's a tip for this website - why not just join forces with the other Accord site? People these days just seem to put the same questions on both at once...
  5. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
    Thanks for the suggestion, it has been considered in the past but both have differing philosophies so it wouldn't work.

    Also from competition, thrives progress so nothing wrong with having 2 sites.
    Zebster likes this.
  6. DeviateDefiant Co-Founder Staff Team

    United Kingdom Leo Northants
    My personal take is that it's all down to the automatic gearbox, the I-DTEC autos aren't known for great fuel economy, but certainly a few MPG higher than you're experiencing on average - I've seen lower than @FirstHonda's figures but that would be way more inline with what to expect. The DPF will only make a 2-3MPG difference (though of course every little helps).

    I can't say that I've heard what @Zebster mentions about Celtic's maps reporting way higher, but very interesting to note and I'll have to read those threads for myself - I do know that a member here not long back had his car remapped by Celtic and could find no difference (and asked for a refund), but an exception doesn't prove the rule.

    I've always so far made the point to never publicly bash TypeAccord, but I will make an exception here because of relevance and point out that @Ichiban left TypeAccord and founded the AOC originally because of Fahad manipulating information on the site regarding Premier Tuning. The dishonesty was what led to the break apart of the UK Accord scene. The other point I will note is that Fahad was (at least at the time) just reselling maps made by actual tuners under the guise of creating them himself. The last point is that I do personally know people who have suffered from white smoke and other issues as a result of the maps he sells. Does he actually tune now? I don't know. Are his maps better? I don't know. Has he stopped manipulating reviews of his business? I don't know either - so please take what I say as a reflection of the past.

    I don't know the guy, I have no gripe with him personally, but I've heard so much over a long period from so many different sources that I can't help but feel many people are having the wool pulled over their eyes. I would welcome being proved otherwise.

    I've reached out in the past, I had a good chat with Alan and made a bid to let the past be the past and merge under one banner. He was accomodating, I was trying, @Ichiban was uncomfortable with the idea but let me proceed, the decision was left to Fahad and that's where it appeared to die. There is a huge history here and I've only just brushed the surface, I don't blame either CJ or Fahad for not wanting to work with one another - but it is a shame.

    Honestly, I'd love to unite us all, almost all of their regular members are active here anyway, but instead we're growing individually. We're a lot more active than they are these days, it's just a shame we can't unite properly and pool together two great resources, but I do understand the many reasons it hasn't happened.
    bijomaru and AndyB1976 like this.
  7. Ichiban Founder Staff Team

    England CJ Leeds
    That is an accurate assessment of the situation it's not the ideal situation but that was the past,and the past is set in stone, I can't see it changing. HK is growing on our own esteem and we cater to all things Honda. The Accord as much as I love it is dying and will die until a suitable successor or a 10th Generation arrives.

    So one model centric car forums will suffer that's why we started HK.
  8. Zebster Guest

    I would just like to make it clear that I was NOT suggesting that remappers DELIBERATELY cause the displayed MPG figures to become exaggerated! I'd like to make the less accusatory suggestion that - following the remap - a greater amount of fuel is dispensed by the fuel injector during each injection sequence (perhaps from an increased fuel rail pressure) BUT the MPG calculation remains based upon the original injector operating time-to-volume ratio, hence the amount of fuel consumed is now greater than the on-board computer assumes.
    Last edited by a moderator: Friday 5th Jun, 2015
  9. DeviateDefiant Co-Founder Staff Team

    United Kingdom Leo Northants
    Seb, I misread what you were saying completely then. The MPG calculation must take into account the fuelling precisely, there isn't a static amount of fuel dispensed, it varies based on many different factors on even a stock car - it wouldn't a useful metric otherwise. I don't think your theory is correct, but you could be right that's it's a by-product of something else. My MPG for example is out on the 7th Generation at the moment as I haven't corrected for the VSS being out from changing the 3rd gear ratio.
    Zebster likes this.
  10. Zebster Guest

    Hi Leo. I do understand there are different metrics that determine the amount of fuel injected, I was just struggling to suggest a plausible explanation. Your wording - 'it's a by-product of something else' would have been better!

    I merely wanted to avoid it looking as though I was accusing remappers of cheating and lying. I honestly don't believe they need to, as most customers are solely looking for the significant power upgrades readily available. Surely none of them also expect greater economy, LOL? But perhaps remapping companies should make this clearer.
  11. DeviateDefiant Co-Founder Staff Team

    United Kingdom Leo Northants
    No I understand completely mate, like the above where I was careful to point out what I knew to be true in the past to be potentially different to the reality today :Smile:

    Most remappers actually advertise better economy as one of the features of their maps (Celtic certainly do), and it's plausible too considering all Hondas run rich from the factory (protect the engine), leaning them out makes more power and requires less fuel :Smile:
    - - - Updated - - -
    Just going to tag @littlebo for his input, as his tuning knowledge is far better than any of ours :Laughing:
  12. Zebster Guest

    Diesels don't run lean or rich... combustion is always 'air plentiful'. Injected diesel mass is (directly?) proportional to torque produced.

    Yes, inhibiting EGR will make a small improvement to economy, even more so if you remove the DPF. I'm uncertain of the legality of the former, but the latter is surely illegal?

    Isn't littlebo is a tuner of petrol engines?
  13. DeviateDefiant Co-Founder Staff Team

    United Kingdom Leo Northants
    Diesels really aren't my thing, but from my understanding AFR is still an important metric, right? I often see smoking and heat problems being related to an overly rich mixture. In effect you're saying the more diesel shoved in the better regardless of the amount of oxygen? I'm probably reading this wrong, I'm barely up-to-speed on the basics of petrol tuning :Laughing:

    @littlebo is a petrol tuner but he's generally very knowledgeable.
  14. John Hamer Senior Member ★ ★ ☆ ☆ ☆

    United Kingdom John Waltham Abbey
    Wonderful!! here we are pontificating about the good and bad points of a wonderful car, I bought my 7th Generation on the strength of reliability surveys from all quarters, and that meant body work as well as mechanicals, just lately I was "obliged" to go Auto, and as the 7th auto does not exist I got an 8th I-DTEC, first impressions were blimey this is big, and the steering felt strange, never entered my mind to worry about fuel consumption nor does it now, you pays your money and takes your choice, I still reckon Honda are making a BIG BIG mistake in letting the Accord die. As for those NEW concepts if I want a van I;ll get a tranny.
    AndyB1976 and Nels like this.
  15. Zebster Guest

    On diesels, AFR is an 'outcome', rather than the absolute requirement it needs to be to create the necessary explosive mixture essential to a petrol engine.

    In theory (and best practice), diesel burn always occurs in an oxygen-rich environment, so all injected diesel is burnt and there will still be oxygen present in the exhaust. But obviously on a naturally-aspirated engine a limit will eventually be reached where there will be insufficient oxygen present for the amount of diesel injected, hence turbo-charging of diesel engines being a common feature to then allow sufficient diesel to be consumed to make engines of a much higher BHP/litre.

    Smoking will often occur:-
    On remapped cars (i.e. the original turbo is incapable of producing enough air for the artificially increased fuel conditions,

    If the available boost has become insufficient due to intercooler/pipework leakage,

    Or, (most commonly) under full-throttle conditions the injected droplet size has become so large that there is insufficient combustion time for these droplets to be completely burnt (even though there is theoretically enough air).

    Smoking is not the terrible sign of a problem it is with a petrol engine... diesel tuners often say "no smoke, no poke"!
    DeviateDefiant likes this.
  16. DeviateDefiant Co-Founder Staff Team

    United Kingdom Leo Northants
    That was very well explained, and very informative :Hey:
  17. Zebster Guest

    There are also these 'rolling coal' lunatics...
  18. DeviateDefiant Co-Founder Staff Team

    United Kingdom Leo Northants
    I don't get it man, doesn't look any different to a normal diesel? :lol: (I'm sorry)

    Seriously though, since when has that been a thing?
    John Dickson likes this.
  19. John Dickson Club Veteran ★ ★ ★ ★ ★

    I find the I-DTEC fuel economy very variable to say the least. Motorway miles will give high 40s MPG in winter and mid 50s MPG in the summer without much bother.

    However round the doors they can drink a bit. All told in all types of driving they are around 10MPG max better than 2.0iVTEC.

    I'm not sure about the detrimental effect of the Auto box; some modern schools of thought say autos are more economical than manuals due to the fact the ECU can control the optimum gear shift time more. I'm no Auto expert and I've never really driven autos but perhaps this school of thought could apply more to CVT rather than geared autos? I'm not sure.

    I have done a couple of full to empty tank MPG calcs and I found that the MID computer actually reads approx. 5MPG less than what the car is actually delivering.

    As far as remaps and DPF removal are concerned all I will say is do not do either.

    A remap is invariably storing up easily avoidable problems for the future (cracked exhaust manifold, shortened clutch life as seen on iCTDis are the common effects of remapping)

    The DPF is there for a reasons - to improve air quality and therefore its removal is illegal and this will help give weight to the argument to get diesels either eventually banned or face massive hikes in excise rates. The focus is turning heavily on diesel emission related air quality and I can see heavier and heavier focus being placed on diesel emissions and DPF tests in the MOT in the future.
  20. Zebster Guest


    I guess that 'rolling coal' idiocy has been around since in-bred rednecks decided that blasting an attractive woman with black toxic exhaust smoke was a reasonable pulling technique. She did actually seem amused!
    DeviateDefiant likes this.