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Increased fuel consumption compared to earlier EP3

mike.h

mike.h

Messages
1,797
Hi all,

I'm on my second EP and this one's fuel economy is really quite poor compared to my '51 model. I used to get ~320 Mi out of a tank, the current one (premier edition w/air-con) I'm getting 260-280. This feels like a HUGE difference.

I have a few tools at my disposal and have checked a few things out but since I don't know what the values for several of the sensors _should_ be it's hard to tell.

The car is in negative fuel trim (running rich), combined short and long term taking it to about -12 to -14%.

Engine temps seem to be well managed, air temp sensor seems to work fine.

MAP reads 14.5psi when the engine isn't running (which seems right for my altitude), and this drops when it is, so it's not stuck on some fixed value, it could be out but I'm not sure what it should be (and it looks to be a relatively expensive part to replace, unless you have something like a k100 and can use a non-standard part).

What values should the O2 sensors be at? I've read conflicting values about their range (one of mine seems to be between 0 and 1.28v, the other between 0 and 1v). How close should their values be together?

What else should I be looking at, what other information can I provide to help people?

Thanks all, looking forward to a solution!
 
I always average between 250-280 miles in mine and think that generally is the average for a Ep3.
I once managed 350 on a motorway journey, and 160 on a spirited drive.
Are your journeys any different to affect the average your getting now?


Sent from my iPhone using Tapatalk
 
The only difference is the car. sadly. I know it's running rich though, which would explain the increase, I don't know why.

That must have been one hell of a "spirited drive" :D
 
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Normally things that affect mpg are dirty intake filter, old oil, binding brakes, poor tracking, stepped tyres, incorrect tyre pressures, dodgy O2 sensors (no idea on usual voltages), driving style, weight in the car.
 
Hi Loxy, thanks for the ideas.

Sadly the first two can be ruled out as it was serviced quite recently. The front calipers have been replaced along with front and rear discs and pads (one of the rear calipers isn't great, but if that were the cause then I'd expect the disc to be a glowing mess at the end of even short drives). The tyres are all in good condition and are running, if anything, slightly higher pressure. Tracking could be out but the tyres aren't worn and it doesn't pull or scrub.

My driving style hasn't changed from my last EP3, the weight may be a little higher due to the air-con, but I wouldn't expect that to increase fuel usage by almost 14%.

Some ideas I've had are:
  1. O2 sensors (as you suggest), but I have no idea how to tell?
  2. MAP sensor (once again though, how would I know?)
  3. Fuel injector delivering too much, injector leak
  4. Overpressure on fuel system (can they get into that state without a third-party fuel pump?) or a leaking fuel pressure system diaphragm
  5. Exhaust leak before the cat (I don't _hear_ anything, how small a leak would have an effect?
  6. Cylinder blow-by (compression failure). I'm not seeing any smoke and it still seems to pull well though... plus the oil's clean so it'd have to be _tiny_ :/
  7. This list is beginning to look like hypochondriacs-are-us :(

I have a lot of data from my logger, if anyone knows how to read that kind of thing for diagnosis then I'd be happy to share. Engine RPM, O2, MAP, engine load, LTFT, STFT etc.
 
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Hi Chris,

The tyres are the standard 205 17's, nothing exciting, some Sportcontact 3's on the front and some unknown Wanli or something on the rear. I'll be replacing them with something a little nicer next time around, this is just what it came with when I bought it. Pressures are running around 34psi or so.

Both front calipers have only just been replaced (standard Honda assembly, fresh out the factory, not a rebuild). The right rear isn't in great shape but it's not binding (no noise, still turns by hand without issue when jacked up, just harder to wind back), I'll be replacing that in short order too.
 
Four even and decent brands all round should make a difference. Also I believe pressures should be 32 psi or so?
 
Agreed, running 34 is a bit over pressure but if anything should reduce rolling resistance a little (with the possibility of increased stopping distance due to a slightly lower contact patch). I think the standard for the EP3 is 32/30 front/rear (https://type-r-owners.co.uk/forums/showthread.php?58294-EP3-Tyre-Pressure :D ). I'll happily adjust that, the only reason I tried higher was _after_ I'd noticed the increase consumption to see if would help at all.

As for decent brands, any recommendations for something that won't break the bank? I used to run quite cheap Proxes CF2's (slightly over-wide 225's, nice that it also protected the rims a little) on the earlier civic without issue but am happy to try something else.
 
Thanks, I'll add that to my list.

Any other thoughts about the possible causes beyond tyres/brakes? I can't imagine it's just that (if it is, awesome, but I'm running out of braking components to replace :) )
 
To be honest mate, I have a 2005 ep3 and even when not hitting vtec hardly at all I get on average between 230 - 250 per tank but then again I didn't buy an ep3 type r for fuel economy. I wouldn't spend to much money changing things just for the sake of it because you will not make that money back.;)
 
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I think you mean 230 to 250 miles per tank. 230 to 250 miles per gallon is slightly ambitious even without using vtec! :D
 
Ricki1985 said:
To be honest mate, I have a 2005 ep3 and even when not hitting vtec hardly at all I get on average between 230 - 250 mpg but then again I didn't buy an ep3 type r for fuel economy. I wouldn't spend to much money changing things just for the sake of it because you will not make that money back.;)
Click to expand...

I might feel the same if I hadn't had another EP3 just before this one whose fuel economy was significantly better. So, sure, if it was just a thirsty model then I'd roll with it, my previous EP3 Type R though was not, this means either something was wrong with the previous one (still seemed to pull nicely, still hit VTEC in the right spot, so I'm not convinced of that) or there's something wrong with this one (and as the fuel trim tells me it's running rich, it seems the best place to start).

So, I'm not really changing things for the sake of it, I'm wanting to change things because I think something's wrong.
 
Chris. said:
Pilot Sport 4 for a road car.
Click to expand...

After looking at it in more detail, the tyres would get me an improvement. I used a tyre economy calculator. Moving from an F-rated tyre (like the SportContact 3's) to a C-rated tyre (like your suggestion or even something as cheap as the Toyo CF2's, would move fuel economy from 7.4L/100km to 7L/100km, around a 5.5% saving if I'm doing my maths right. Not bad. :)
 
One thing I forgot to mention. When driving back from Wales I was on some mountain pass road, popped the hood, disconnected, checked and reconnected the wire for the MAP sensor, used a cable tie to secure the little rubber pipe running from the air box to the head cover, and reset the ECU. For a tank or so of gas the economy was awesome again :/
 
Also was your last car mapped? I can easily get 350 miles in my DC5.
 
Chris. said:
Also was your last car mapped? I can easily get 350 miles in my DC5.
Click to expand...

If it was, it wasn't done by me. Would there have been a way to tell?

320/tank works out at about the 32mpg that the model was sold as though (assuming UK gallons, 310Mi / 40L * 4.55L/gal == 31.85mpg) which is also kinda what I've been basing this on. If it's US gallons then I guess it's a different matter entirely :)
 
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