Civic HX Manual trans 1996-2000 Lean burn information
 

Since there seems to be a lack of solid information about the 6th gen HX's lean burn functionality I figured I would start a thread with my experience.

My ecu is from a 97 HX, manual transmission ECU is 37820-P2N-A22 federal version.

**I am running a DX geared transmission.**

I would like to keep this related to the 6th gen Civic *96-00* only.

There already seems to be plenty of information regarding the VX's out there.

In general here's the requirements for me to get into LB.

1. Engine must be running ~3 minutes.

2. TPS must read > 11% and <21.9%

3. Minimum mph ~28

4. Gear must be 3rd, 4th or 5th.

5. > 1800 and <3099 rpms. It seems to really like 2700 rpms to engage.

6. Engine load, I haven't nailed this down yet but definitely must not be >80 so far.

7. IAT's do seem to play a roll. What roll TBD.



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

So far I have been able to get into LB generally anywhere above 2100 rpms.

Tonight my IAT's were ~70 degrees and I was NOT able to get LB anywhere below 2400 rpm's. When I would dip below 2400 it would disengage repeatedly. This was tested during a 60 mile drive.

I will pay more attention to what my IAT's are when the car's being nice and letting me get LB at lower rpm's.

I did a tiny amount of data logging. Here's proof of exactly what the ECU is commanding for AFR's. This is directly from the ECU.

http://i80.photobucket.com/albums/j1...pspb7ubckd.jpg



https://www.youtube.com/watch?v=vz8RKaXNPv8

I wonder to myself, is it better for economy to intentionally keep the rpm's in range to use LB or is it better to shift if you're not in the highest gear and be out of LB rpm range.

Some will say that the vacuum gauge is the best way to tell if you're getting the best MPG possible but I am not completely sold on this.

A scenario is cruising along in 5th gear, flat ground. Let's say my vacuum gauge is sitting right at 15. Now LB kicks in and I now have to give more throttle to maintain my speed. The vacuum gauge will now read 7..... You can see where I am going with that.

I can say that when I am in LB in 3rd or 4th gear the shift up light will be illuminated the entire time and if I shift up a gear I will be out of the RPM window for LB. This would be even worse with HX gearing in the transmission.

Once I get my MPGuino in the mail I should be able to figure this out easily.

I guess I could watch the injector duty cycle and figure it out, but it's kind of hard to get a real good picture watching the scan tool.

I have to think, that in the most simplest terms, the lower your injector duty cycle at any given time the better your economy will be.

Seems like ultimately that's what really matters.

I have figured out with the help of MPGuino that LB is hardly what I thought it would be.

I am certain that a VX ratio transmission would return far greater MPG than LB does.

I do now know that I'm much better off selecting the next gear to lower rpm's vs staying in a lower gear to keep in LB.

Some people on here really like lean burn and some people do very well without it. Bruce Pick told me that he burned the same exhaust valve twice and he believed that was from maximizing his time in lean burn. He recommended that I focused on EoC or pulse-and-glide, saying he thought that would actually net better mileage.

Then there are the expensive oxygen sensors.

I'm pretty sure it's been tested and proving that in LB the cylinder / exhaust temps are actually lower then when running at stoich afr's.

I can see his point though on EoC and P&G being more of a benefit than LB is.

In my case I am really starting to see the benefit to taller gearing *which I do not have yet*

On this 18 mile trip I basically accelerated WOT upto posted speed limit then immediately dove into 5th gear. I must say the D16y5 is quite a torquey little guy at very low RPM's vs the y7 and y8.

I didn't try to get LB at all, just let it happen when it was ready. Once in LB I maintained it unless speeds were dropping such as climbing a hill then I would downshift a couple gears and WOT to a touch above the speed limit then back to 5th.

I did lots of EOC as there's a long downhill stretch BUT I also had to climb up this same hill on the same trip.

I will say my fuel injector cut button works great now that I have put the IAC on a different 12v source. No CEL and the LB timer does NOT reset as if you turned the key off and on to kill the engine.

I can tell right now that the MPGuino is going to pay off large for me. I really had no idea how to drive the HX + LB properly.

I have the MPH dialed in perfectly and used the spreadsheet to calculate the values for the injectors. I think it's close as when I was driving normal it was reporting around 38 MPG which is what I had been averaging.

I will fine tune the flow rates as I get a few tanks through it!

Personal best for me.

Lean burn seems to be hit and miss as far as fuel economy, but I think my tire pressure has affected my current tank.


96 civic hx manual transmission factory shift light, s40 LSD trans. Markings on my chassis indicate my car was one of the first m/t hx's produced in 1996. There are grease pen markings on the underside of my hood for the inspector number and qc checks passed 76/76

Lean burn at 55 mph @ 2300 rpms. Lean burn disengages at 78mph. I find that the up shift light is more of an economy light to keep the car in the correct throttle and power settings

1998 civic hx manual trans no shift light stock trans

Best tank was 38 mpg, car was very sluggish and mediocre at fuel economy. Lean burn was intermittent most of the time the car would not engage lean burn until fully warmed up after 10+ minutes. I can remember the car bogging when shifting at 2100 rpms with the hx trans, really really slow when trying to accelerate onto the freeway from a stop light. I mean really slow, having to floor it to keep up with soccer moms and even big rigs

Best observed economy was 51 mpg highway with my 96 on 86 non ethanol gas. Best tank 44mpg, average tank is 38mpg summer 36 mpg winter

I am well on track to hit my first goal of a 45Mpg tank.

My fuel gauge is ~1/4 with 330 miles on it. Normally I am down around the empty mark and any time now my low fuel light would start to flicker.

Today's commute home, didn't have engage LB a single time.

I'm at 275 sitting on the top side of half of a tank of gas. The needle tends to fall very quickly after half tank and I fill up at a quarter tank. I'm sure I would gain the most economy the less fuel I carry on board however I do not like the added stress and heat on the fuel pump. Im sure if I took out my two 12 inch subwoofers it would make a difference too lol.

I'm also running 10w30 synthetic, again I should switch to a lighter weight once summer hits full swing

Next tank I will try some marvel mystery oil. See if that snake oil does anything

Yeah my fuel gauge is far from linear also.

The top half of the tank is around 7 gallons and the bottom half is somewhere around 4-4.5, that's why.

Fuel gauges are discussed here: 8 Gadgets That Lie to You Every Day | Cracked.com

In the last fifteen years, I believe that is the second comment I have read about only partially filling the tank in order to save gas. One gallon of gas weighs 6.073 pounds (Gasoline - Wikipedia, the free encyclopedia), so if I only half-filled my 11.9-gallon tank, I would shed 36.134 pounds. My Civic weighs 2,519 pounds, so I would reduce the weight by 1.43%. The general rule of thumb is that for every 2% of weight you lose, you increase fuel economy 1%, so that would be ≈ 0.715%, and a 50 MPG tank would become 50.36.

Of course, we do plenty of modifications with smaller results.

This is all true.

I prefer to just fill it all the way up. I really hate stopping for fuel!

Once I know I have this gauge dialed in, if I see regular 45 mpg or more I am going to be very happy.

I am going to keep my eyes peeled for either a HX or VX transaxle.

Maybe I'll end up with both lol. I have EX and DX now already.

I use to own a mustang that would have squeaky shocks if the tank was less than half full.

At this time in our economy convenience>consumption so gas always full tank for me

I often have gas discounts, so I wait as long as I can to fill up. If I filled up twice as often, I would receive half the discount.

It is just a dollar here and there, but still.

MuleVX who has the best MPG on here always fills up every 3-4 days so about 1/2 tank. I'm going to try that method for a while because I just got 2 50mpg tanks in a row, but on a 1/2 tank fill I got 53. I'm thinking the extra weight is going to benefit my coasting, which is where I'm grossing the most gains. Plus I think Mule is on to something.

Some people have different priorities in life.

For me stopping for fuel is a very low priority and one I really try to stay away from.

To me it's just not worth saving ~50 lbs to possibly get a couple extra MPG's.

EDIT: It would be ~36 lbs in my Civic.

If you really really want effecienCy you should map your route to expire at the gas station at the end of your commute lol

One of my goals in life is to fill up as infrequently as possible.

just got myself an HX and this thread helped me with some questions thank you much!
http://img.photobucket.com/albums/v6...pswt0jhluh.jpg

Right on, good choice!

Wahoo! Personal best for city driving!!!

This tank was on 91 octane non ethanol but it is still the best all city tank I've ever gotten. I changed my driving style since my last measly 36 mpg tank and I'm shifting at 3k. Bogging the car and adding throttle seemed to hurt my last tank

40.7 all city :)


http://i758.photobucket.com/albums/x...pslrt5doxz.jpg

Very nice.

I had one highway trip for about 45 miles which was for the tank of gas out in bfe. I know it added to my efficiency but it was about an hour and a half round trip so not very convenient, probably won't be going out there again

I added some MMO to this tank (6 ounces). Only 15 miles on it so far but the car seems to have better throttle response but that all could just be in my head, only the tank will tell the tale.

Some of my best tanks were with MMO in warmer weather. Tough to pin it down, though. If there's a magic juice out there, I haven't seen it (yet). I've dumped in Techtron and Gumout as well.

Testing 87 Octane Ethanol Free now. Not sure that it's worth the added cost. It's 50 cents more per gallon than regular in PA and $1.00 more per gallon than regular here in NJ (where ethanol-free can't be found). I have to drive three hours round trip to get it. Kinda stupid, but hey, I've done things that are way more stupid that that … :roll eyes:

I've tried Lucas, rxp, techron, but the MMO seems to have kicked my little civic in the butt. Even Vtec seemed to hit harder lol, but my fuel filter probably needs to be changed anyways so I'm sure it's just clearing out restriction.

Yeah my drive was about an hour and a half round trip and even then it was tedious, I don't have much free time but felt like splurging. 3 hours is commitment lol

Any updates to this?

Printed AFRs
 

Firehawk, How did you capture those AFR's - by what means ? Rob

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?

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.

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!

O-2 Sensor add-on in HX
 

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 ?

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

More Lean Burn 2000 HX
 

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).

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.

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

Welcome back. :thumbup:

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?