my FE thread
 

so, for the entire winter i averaged about 31mpg in my integra GSR. 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

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

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?

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

i managed another 38.2mpg tank this week.

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.

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. :)

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.

Grill blocks are a balancing act.
 

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...

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.