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Hi all-

I've been honing my FE skills over the last several months and seem to have reached a plateau in the 37-39 mpg range (95-100% suburban regular commute). I've had a couple tanks fall below this due to construction and AC use. My record segment is 45.4mpg on a 25-30 mile rural trip - I was hoping for 50mpg- but I just couldn't get there. My best highway run is about 44.5mpg on a 35 mile segment.

Although my car (an 08 MT) is 14mths old, it only has around 6500 miles on it right now so I'm sure (hope) it will continue to loosen up with time.

Thus far I've really just been timing lights, coasting as much a possible in gear, keeping speeds and rpms down (under 2k most times). I'm running two SG2's so I've got the tools to do better - but thus far I've really just been using the instant FE and trip avg FE.

I'd love to know how I can use LOD, IGN, TPS etc to take my FE to the next level.

Tips would be much appreciated.

I'm driving an 07 AT, and employing the same techniques. Just curious, have you been following your LP? I noticed I'm getting 9999 (instant) MPG when I coast in gear in certain situations, but LP reads as OPEN, which to me is counterintuitive.

That's expected. In an overrun situation (engine braking), there's no need for fuel in the engine, so the injectors turn off. Now, there's no need to monitor the exhaust O2 mix, since it's not needed to adjust the injectors. Open Loop means it's not reading the O2 sensor.

You'll get better trip mileage by coasting in neutral. The instant will only be in the 100-200 range, but the longer coasting distance makes the difference.

As for LOD and throttle, read this AutoSpeed Article about BSFC (http://www.autospeed.com/cms/A_110216/article.html).

Thanks! Now it makes sense.

What you can do if you find yourself in a situation where you do need to use engine breaking you can keep shifting down through the gears. Just keep the RPMs above about 12-1300 and you should be able to hold it. Most cars will cancel fuel cut when you hit the brakes, so keep that in mind. My car doesn't handle going all the way down to 1st all that well (it is an AT) so when I get down to 2nd and the RPMs get to that 1300 mark I just go to N.

Let me put in a plug for the GPH display on the SG2 when going uphill.
It surprised me when I figured out that at 35 MPH going up a gentle grade I could maintain speed at rates as low as 0.6 GPH. When I'm not trying to control GPH on the same stretch of road it's real easy to run at 1.1 GPH and feel like I'm doing the best I can.

I have the AT version of your car. A couple tricks I've found very effective are driving without brakes (DWB) and driving with load (DWL). The first is pretty self explanatory. Don't take it literally, but do try to plan ahead. If you're braking, it means you accelerated faster than necessary in the first place, which wastes gas. Driving with load means you try to maintain a constant value on the LOD gauge. Ideally, you should be able to manage light traffic and elevation changes without changing LOD. The Civic is set up so that i-VTEC will remain active in most DWL scenarios. Although the exact target LOD value changes with speed and gear, I typically aim for around 50.

Personally, I haven't found IGN and TPS very helpful. I feel I can get more useful information by following LOD. When accelerating, I aim for a value of about 80. When cruising, I aim for around 50.

About how fast did you drive on that rural segment at 44.5 mpg? My AT will have lower rpms at highway speeds, but I can stay in the low 50s mpg at 55 mph in the summer.

Have you read about P&G? It's a more advanced technique, but yields good benefits.

The Civic is set up so that i-VTEC will remain active in most DWL scenarios.
I've found that as well. It does seem that I have to coax it, though. Go a certain speed, then lift off ever so slightly, and it kicks in. But the "ever so slightly" is subjective.
Although the exact target LOD value changes with speed and gear, I typically aim for around 50.I'll try that out. I still don't understand LOD too well. But I'd assume that would mainly equate with a speed? Like, say, 45mph or so? That's useful for some trips, but not necessarily on an interstate!
About how fast did you drive on that rural segment at 44.5 mpg? My AT will have lower rpms at highway speeds, but I can stay in the low 50s mpg at 55 mph in the summer.
I'll mainly get something like that in the high 40 to mid 50 mph range. Depends if I can coax the i-VTEC or not, too. I've gotten 62mpg going in the low 40mph range, and was actually able to maintain that for a short while. Must have had a real steady foot.

Speaking of which.....

One thing I've found is it's hard to maintain a 18TPS. At speeds close to 50mph that seems to be good to maintain DWL. Despite how steady I keep my foot, it seems to jump pretty quickly. And I see the results in the GPH, even though it doesn't look like my speed changes much (it does, but slightly). Any tips on how to keep that TPS steady?
(I really wish cruise control would work on TPS and not speed)
Even if not 18TPS, basically anything! That pedal seems a little sensitive.

-Mike

Well, after being a little more observant over the past few days, I've been able to coax my Civic into iVTEC more often. Pretty easy to do at 45mpg or so. I seem to get in the high 50mpg and sometimes low 60'smpg. If I keep a REAL STEADY foot, that is. TPS is somewhere between 17 and 18. LOD hovers around 37-39. Does this number make sense?

The trick is a REAL STEADY foot. That 17-18TPS is hard to do...as I said above, my throttle seems to jump between 17-19 and likes to skip 18.

It also seems the engine is pretty sensitive to the throttle fluctuations. I wish there was a way around that.

The proof is in the numbers, though. My morning commute to work today yielded a 38.2mpg FE. Usually I'm in the low 30's, maybe 35-36.

-Mike

Hi Mike:

___Swap out TPS to IGN and if your Civic is like most Honda's, LOD below 50 and IGN between 30 and 37 brings about that 60 + you will want to use and maintain. This is SHM and what you should maintain on the highway.

___Good Luck

___Wayne

Swap out TPS to IGN and if your Civic is like most Honda's, LOD below 50 and IGN between 30 and 37 brings about that 60 + you will want to use and maintain. This is SHM and what you should maintain on the highway.

Ok, can you give a short "how that helps"?
I read this (so at least you can see I tried to find out on my own!):
IGN is ignition advance. This is the position of the crankshaft before top dead center (TDC) when the spark plug fires. The numbers represent degrees of rotation of the crankshaft. IGN depends on engine load and rpm. Higher numbers generally correspond to lighter engine load and higher instantaneous fuel economy. Light on the throttle may get you ~40 IGN while a heavy foot could give numbers around 10 or so. These numbers will vary between different cars.

Essentially, how does that help me, as compared to using TPS? I'm still trying to learn!

Thanks
-Mike

Hi Mike:

___I suspect your Civic is like most of the late gen Honda's. Take LOD to just below 50% and you will see IGN float between 30 and 37. Now look at your iFCD and you can tell me what you see. I can bet it will be a big number ;)

___Good Luck

___Wayne

I'll try that when I go to a dr. appointment this afternoon. Hopefully I'll remember.

A LOD of ~37 will generally give me the best FE, assuming I'm in 5th gear. Usually, at, say, 45mph, a TPS of 17-18 will give me that, assuming the car is warmed up. It doesn't always happen that way, though. Perhaps the car isn't warmed up all the way in that case?

But I'm seeing all around (from experts such as you) that TPS isn't the best gauge to use. It helps ME, but if other gauges help even more, I'm all for it...I'm just trying to learn.

It looks like IGN shows almost the same thing as LOD?
(I'm not much of a car person)

Thanks
-Mike