my FE thread

[EH3]

so, for the entire winter i averaged about 31mpg in my integra GSR (http://www.gassavers.org/garage/view/450). i installed a partial front grill-block in march and my mileage immediately jumped 1-2mpg, even with cold temps and driving fast. for the past 2 months i have kept it at 32-33mpg.

this week i decided to slow down and change my driving technique slightly. i kept the speed at a constant 60mph on 55mph "back roads" (versus 70-75 typically... i know, i know), coasted to stops and did everything i could to avoid completely stopping for lights.

from those changes alone, my last tank was 38.03mpg average. ~5mpg increase from an already high 32-33mpg average. this tank was about half highway cruising at 75mph. my gearing is so short that i'm revving at 4200rpm at that speed, just before VTEC engagement.

i'll be very interested to see what next week's tank looks like

here's my gas log (http://www.gassavers.org/garage/viewgaslog/450?)

note: mileage all adjusted 3.3% because i have civic sized tires installed - 195/50-15 vs 195/55-15 for integra

[civic lover]

I had the exact same experience. My 89 lx civic got about 38 on a good warm day. two tanks ago I switched my driving habits to how you explained and I jumped up to 42.3 and the next tank was 41... Driving technique definetly makes a differences. Ever think about swapping out the tranny?

[EH3]

no, the difference in acceleration is great. i do track the car a couple times a year, so performance is important to me.

[EH3]

i managed another 38.2mpg tank this week.

[Danronian]

You might want to try reinstalling the factory intake if you still have it around.

With mine reinstalled onto my VX I gained at least 3 MPG. Well worth a free or near free mod if you have to buy one. Throttle response also was better due to the properly sized intake tubing for the throttle body wheras the short-ram intake would give it more power in the top-end but made it feel terrible in the low-rpm range and with throttle response.

[EH3]

i've considered it if nothing else than for the OE/stock look and reduced noise.

[Danronian]

i've considered it if nothing else than for the OE/stock look and reduced noise.

Very true!

After installing one on my 95 LS integra I was quite amazed by how quiet the car got! On the VX it was even more of a difference to install the factory intake for the noise reduction. :thumbup:

I would try to trade someone on Honda-tech, someone will probably ship you the entire thing for your short-ram in exchange. :)

[EH3]

ok, so i decided to remove the front grill block to see how much it's actually helping... well, i found the opposite to be true.

over the 104.6 miles i drove today i filled up with 2.40gals.... 43.6mpg w/o the gill block! WTF? that's a HUGE difference from the 38.2mpg tank previously. could it really be hurting my aero that bad by having it on?

i'm leaving it off for tomorrow for another ~104miles to see if it was just a fluke.

[DracoFelis]

over the 104.6 miles i drove today i filled up with 2.40gals.... 43.6mpg w/o the gill block! WTF? that's a HUGE difference from the 38.2mpg tank previously. could it really be hurting my aero that bad by having it on?
Grill blocking is clearly a balancing act. If you do too much grill blocking FE does go down. But that lower FE is not due to aero (the best aerodynamics really are with a full block), but rather the heat (which increases, the more grill blocking you do).

If the engine gets hot enough, the cooling fan(s) come on (to cool down the engine, and keep it from overheating), vs you lucking out and getting the cooling by the air going through the grill. And those fans use a LOT of power, and therefore have a surprisingly high drag on the engine (often much higher drag, than the drag savings from doing the grill block in the first place). And worse yet, if/when the engine gets "too hot", the ECU might sense something wrong, and convert to "limp home" (fuel wasting) mode, to try to get you home safely. And both of these things can cause your FE to go back down...

BTW: On my CRX an aprox 2/3 grill block (the left and right sides blocked, but the center left open) seems to be about where the sweet spot (best FE) lies. No doubt the sweet spot will be different on other cars, so YMMV (and you might have to experiment). But the point is, some grill block can often improve FE, but "too much" can actually cause you to lose FE...

[EH3]

right, i get what you're saying. the engine temp needle never moved a bit even with some of the hotter days we've had this year. it's not going into limp mode, plus it requires a lot of heat to do that. i know, i use to be a honda ECU tuner.

it's not a complete block, either. i left openings around my driving/fog lights on the bumper. plus, it's in front of the grill so there's about 6-8" of opening in front of the radiator.

i guess i'll just first make sure it's not a fluke and go from there. i did get an OEM intake for it tonight, so i expect that may even push me closer to 45.

[gearheadcheapskate]

Aha! I've been waiting for a GSR owner to chime in. I've got a '94 w/109k; bought it brand-new 14 years ago. Up until fuel economy mode really kicked in a few months ago, it's had an odd combination of really easy life and all-out beatings. Literally thousands of excursions to the 8300 rpm fuel cut-off, 6+ seasons of SCCA autocross, a few times at the drag track,etc, etc, etc.

Anyway. I've got a lifetime average of about 32.0. In '01-'03 it saw a lot of highway use and turned in 33.5, 33.7, and 33.3, respectively. Since '04, I've lived 1.9 miles from work and it's been hard to keep mileage up.

I've put 4 tanks in it so far this year and it's obvious when the hypermiling started. 31.7, 35.7, 38.6 and 39.3. I'm headed for the big 4-OH on the next tank!

It's stock except for adjustable koni yellow's, hawk HP's, and sway-bar bushings, and ign timing.

Some integra tips:
1-advance the ignition timing. Most people won't do this, but I've had mine as far as the distributor would go (about 23 degrees BTDC at idle) for about 80k miles now. OBDI GSR's have a knock sensor, so it will retard the timing if it needs to, but the knock sensor only works below 5500rpm or so. I always use 93 so I'm not worried. Your off-idle tip in and below 1500 rpm torque will increase nicely with the timing here.

2- I've just disconnected the power steering pressure switch. This switch is down by the rack and idles up the engine speed during high steering load times. Since I've begun engine-on coasting, I didn't want the idle speed any higher than it should be. I haven't missed this feature in the least.

3-decel fuel cut-off is closed throttle above 1050 rpm. I'm in neutral unless I *must* stop, then I'll engine speed match a low gear and drag it down to 1050 for fuel cut-off.

4-neutral alignment: many racing folks will toe out the wheels for better turn-in. It works for that, but causes too much drag.


I'm trying to figure out what it likes best for acceleration- low rpm lugging or a higher-engine-speed with very little throttle opening. Any ideas?

Other ideas: break the power steering pump open and reduce the stand-by pressure somehow, chip the ecm and lean-out the low-load-small-cam ranges and further tweak timing (investigating this next).

Any others?

[EH3]

1-advance the ignition timing. Most people won't do this, but I've had mine as far as the distributor would go (about 23 degrees BTDC at idle) for about 80k miles now. OBDI GSR's have a knock sensor, so it will retard the timing if it needs to


as a former honda tuner, this is not sound advice. there is no reason at ALL to advance the base ignition timing beyond OEM specifications.

obd1 honda's knock detection hardware is nothing short of worthless. frankly, it serves no purpose whatsoever. it's so absurdly over-sensitive that VTEC engagement and gear changes register as "knock" readings.

thankfully, knock feedback is altogether ignored on OBD1 ecus. honda only began to use knock feedback for timing management with obd2 systems. the d16y8 uses realtime knock feedback to alter ignition timing, which is a very different architecture from the OBD0/1 "maps".

i don't recommend what you've suggested, even if it's been fine for 80k+ miles.


as for acceleration:
i have a b16 tranny, so i get to take advantage of shorter gearing to accelerate faster with less throttle input.


also, i'm working on another 40+ mpg tank this week. i may even best my former record fill-up of 43mpg

[theholycow]

I'm trying to figure out what it likes best for acceleration- low rpm lugging or a higher-engine-speed with very little throttle opening. Any ideas?

Lugging is bad, but what you're describing is probably not lugging.

http://www.standardshift.com/forum/viewtopic.php?p=91271#p91271
I'm pretty sure that most people who think they have been lugging their engine really have not been lugging it at all. I'm not even sure that modern ECUs and knock sensors would let the engine lug. My experience with the Jetta so far has been that it either runs or stalls. I have not heared it lug (even when I accidentally took a corner in 4th instead of 2nd).

Putting a load on an engine at low RPM will make it growl, but growling is not lugging. Lugging is irregular. If it growls and goes it is not lugging (at least in my understanding of the matter).

http://www.standardshift.com/forum/viewtopic.php?p=172612&sid=3631fdaa15b91888da82eec298ed7710#p172612
It isn't lugging. You'll never forget the sound of lugging once you do it. Sounds like a bunch of metal sh*t exploding under your hood. Or like a jackhammer.

Based on what I've read there, growling is acceptable, but lugging is very terrible.

So, that all said, it's been my experience that wider throttle + lower RPMs = better FE. My observations are explained by reduced pumping losses -- it's awful difficult to suck air through a closed throttle, but if RPM is low and throttle is open, it can suck easier while still not getting a lot of volume and therefore not using a lot of fuel.