Civic HX Manual trans 1996-2000 Lean burn information

[Joggernot]

It's "winter" down here, so we have the alcohol mix gas. It's been spotty; some well above EPA and some below EPA. Can't explain it; drive the same route most days; but fill up may be higher alcohol or lower alcohol, depending on where I go for cheap gas.

[oneheadlight]

Originally Posted by Xist

Wow. Eight months. I hate to hijack this thread, but I will say a little about my HX. I do not ever remember having my car lose power on the highway or freeway, which everyone says is indicative of lean burn, but I try to maintain 55 MPH, although my GPS says that is only 51 MPH. I had been at or near 50 MPG each tank until I finally started my current job. I have driven 1,400 work-related miles since the end of September and I usually hit traffic. My tanks have been around 40 MPG since. I wondered if it was the colder weather and I realized that my tires were only at or below 30 PSI. Also, someone backed into my car, and I took off my grill block and air dam until I could pop out the dent, but I had 40 MPG tanks in October.

How have you guys done?

well I'm new here, but have a 96 HX, and the best I've gotten is 32mpg right now and it's a manual trans. Seems that around here the new speed on the highway is 80mph+ which of course as I've learned, is way outside of the lean burn mode. around the rural areas, speed is lower which of course would get me higher mpgs.

sorry to hear someone backed into your car!! Hope it's not that bad of damage!

I usually keep my tires around 33psi, haven't been driving this car much (was with other family members) but it's back to me having it. And having to remember all these tweaks to get the mpgs!

[1hondaman]

When my car is in LB the commanded AFR's from the ECU seems to stay ~20.5.
When not in LB the commanded AFR is ~14.6

FIREHAWK618 Where did you plumb in the O-2 Sensor to get your AFR readings ? Did you weld in a "bung" at the upstream side of the cat in the exhaust manifold ? Did you find a crack in your exhaust manifold ?

[Baltothewolf]

Wideband o2 sensors must be welded UPSTREAM of any catalytic converters. Downstream will scew accuracy.

[1hondaman]

Here is an up-date I posted on Honda-Tech that I copied and pasted here.

If you see my earlier post (12/20) I claimed no cracked exhaust manifold. WRONG ! Added to that was the plugged EGR ports which I have cleaned and posted photos on EcoModder. So once again THANK YOU for bringing this to my attention. The crack is small and I am going to attempt to weld it up at the same time I weld in a 0-2 bung for the new AFR gauge I just ordered.
Other news; With the instruction of Brucepick I have programmed the SG to read Lean Burn. This LB can be achieved but not consistently. At times it looks like LOD is the parameter to kick it out and at others it looks like 2500 RPM will throw it out. I suspect I will never run down just what does kick it out as the ECU is busy making calculations by reading a whole array of inputs.
Once the manifold/cat-con is welded up and the AFR gauge is installed I will have more to report.
Those here on the site may say to me "buy a new manifold, at 214K on the clock you are due for one - the honeycomb media is shot by now". Being frugal, this is not my first move but if there is sufficient evidence to do so, let me know. Thanks.

[zeroyon223]

Bumping this thread, what octane fuel are you guys running in these? I'm using 95ron (I think what you guys stateside call 91), anyone used a lesser or greater octane? Was the economy difference negligible? Could running in lean burn afr be dangerous on 91ron?
And on the EGR setup, was it full of carbon at higher milages? Any gain on blocking it off? Does the US car have a single wire o2 sensor?
Mine is the japanese import EK hatch with D15B '3 stage vtec' and 1st gen cvt. It runs at bang on 2500rpm at 100km/h, seems to work best at around 90-95km/h with the gearbox in E mode (buttons on steering wheel).

[MPGomatic]

I run 87 octane (US) E10 Regular primarily and have run some 91 octane E10 Premium tanks. Differences were negligible.

I've run two tanks of 87 octane E0. The slight bump in MPGs wasn't worth the added cost.

I'd like to roll the dice on a couple of tanks of E15 and E30 to see what happens, but I need to do a bit more research first.

My HX lacks cruise control, so highway tests are (more) prone to fluctuation.

Originally Posted by zeroyon223

Bumping this thread, what octane fuel are you guys running in these? I'm using 95ron (I think what you guys stateside call 91), anyone used a lesser or greater octane? Was the economy difference negligible? Could running in lean burn afr be dangerous on 91ron?
And on the EGR setup, was it full of carbon at higher milages? Any gain on blocking it off? Does the US car have a single wire o2 sensor?
Mine is the japanese import EK hatch with D15B '3 stage vtec' and 1st gen cvt. It runs at bang on 2500rpm at 100km/h, seems to work best at around 90-95km/h with the gearbox in E mode (buttons on steering wheel).

[Chrysler kid]

I'm back again, I currently have 2 1997 civic hx's. If you have any questions about lean burn post up.

To get the most out of a civic hx you need to do regular maintenance to the ignition system, primarily spark plugs and wires

It can be hard to determine when the car is in lean burn without any instrumentation. I highly reccomend just a simple vacuum gauge to see when your lean burn engages. The vacuum gauge is also very beneficial for staying in lean burn, and maximizing fuel mileage by showing if you have a steady foot on the pedal

[Daox]

Welcome back.

[California98Civic]

Originally Posted by Chrysler kid

... I highly reccomend just a simple vacuum gauge to see when your lean burn engages. The vacuum gauge is also very beneficial for staying in lean burn, and maximizing fuel mileage by showing if you have a steady foot on the pedal

Welcome back. So does the vacuum gauge help you stay in lean burn in any way besides the steady foot? Does it help you detect the transition to lean burn, for example? And do you have an UltraGauge, Scangauge, or other OBD2 data reading device, such as the torque app?