Found a Civic VX; Great Mileage Starts Now! - Page 5 - Fuel Economy, Hypermiling, EcoModding News and Forum

Clev · 02-03-2009, 12:44 AM

Quote:

Originally Posted by NachtRitter

Ya, that's a good point too. I do have a "Crank Position Sensor", but have no idea how interrupting it would affect the engine... I may have to experiment with that ...

I don't know how it affects a running engine, but on my '99 Metro, trying to crank the car for more than 30 seconds with the crank sensor disconnected turns on the Check Engine light.

NachtRitter · 02-07-2009, 03:08 AM

Well, I'll see if I can play with it this weekend... It's looking to be a bit wet, and I don't have a way to get the car into the garage... so we'll see...

Refilled today and looks like I got 45.3mpg on the last tank... not too surprising that it was lower... I had to smog it, and since the smog place is less than 2 miles from my house, I drove around a bit prior to my appt to make sure I warmed up everything sufficiently... wasn't really thinking FE during the drive... and then they let the Maus idle for another half hour at least as they fiddled with the smog machine

NachtRitter · 02-08-2009, 07:24 PM

Swapped over to the Fed version of the ECU & the 5-wire O2 sensor this weekend, following the instructions provided at Civic VX Lean Burn Questions - GasSavers.org - Helping You Save at the Pump. I'd scavenged some connectors from the local Pick-n-Pull so that I have a reversible setup (in case there was a problem next time I have to smog it). Aside from the work involved with soldering all the wires (and then discovering some mistakes and having to un-solder and then re-solder) out in the friggin cold garage, it was a fairly easy swap.

Since I just started this tank, I'll should be able to see how much of an impact this will have fairly soon.

Dang, I suppose this means I'll have to adjust my combined EPA numbers...

NachtRitter · 02-09-2009, 12:35 AM

Ordered the MPGuino today as well. But probably will not install it until I have figured out a good way to get into the wiring without damaging the original harness. So will be looking for a reasonably priced OBD1 to OBD1 harness that I can hack up rather than touching the stock harness.

MetroMPG · 02-09-2009, 10:17 AM

The game changes when you get that MPGuino.

NachtRitter · 02-10-2009, 12:30 AM

First day driving the Maus with the Fed version of the ECU... Different! I am fairly certain I can feel it going into and coming out of lean burn mode... seems like a fairly sudden transition... almost feels like the car surges when it comes out and hesitates when it goes in.

Also noticing an erratic idle, bouncing between ~900 and 1200 rpm while coasting in idle and a steady ~1100 while stopped (whereas it *should* be around 600)... sounds exactly like what was discussed here: Civic VX - Leaking EGR Valve problem - GasSavers.org - Helping You Save at the Pump. The solution seemed to be replacing the 'O'-ring for the MAP sensor and cleaning out some carbon, so will try doing the same thing to fix mine. With over 305,000 miles, I wouldn't be too surprised if that's the issue.

With the CA ECU, I never did see that problem, but then James did say the (Fed) VX's were finicky...

Clev · 02-10-2009, 12:36 AM

Quote:

Originally Posted by NachtRitter

First day driving the Maus with the Fed version of the ECU... Different! I am fairly certain I can feel it going into and coming out of lean burn mode... seems like a fairly sudden transition... almost feels like the car surges when it comes out and hesitates when it goes in.

Lean burn happens when the engine switches to a leaner profile cam via VTEC, right? Does that mean that you could rig a light to illuminate when the car is running on the lean burn profile? I wonder if lean burn is vacuum-specific, i.e. a vacuum gauge could point out exactly what throttle position brings it in and out of lean burn.

NachtRitter · 02-10-2009, 01:05 AM

As I understand it, the lean burn capability is pure electronics; nothing to do with the cam profile. The computer figures out the right conditions (which I am sure are related to vacuum (via MAP sensor), engine speed, vehicle speed, etc) and cuts the fuel and then monitors the lean burn via wide range O2 sensor (aka Lean Air Fuel (LAF) sensor).

There is a way to monitor that, according to a thread that TomO put together at GasSavers.org: Civic VX Lean Burn monitor - GasSavers.org - Helping You Save at the Pump.

The SOHC VTEC-E (as it's called on the VX) works kind of the opposite direction as a typical VTEC... (again, explaining this as I understand it so apologies if I explain it poorly) The VTEC-E minimally opens the 2nd intake valve at low engine speeds to better help mix the air & fuel (and therefore allow leaner burning at those speeds) and then gradually goes to normal 4-valve operation at higher engine speeds (the ECU definitely can still allow lean burn even at the higher engine speeds). On the other hand, the standard (SOHC) VTEC opened the intake valves normally at low engine speeds and then opened them even more at higher engine speeds.

Apparently, there is also a 3-stage VTEC which combines both the economy of the VTEC-E as well as the performance of a SOHC VTEC... but that one was never made available in the US market.

NachtRitter · 02-12-2009, 12:46 AM

Had a cold storm come through today... Well OK, "cold" is relative... the temp didn't go below 32F (yet), but it was cold compared to what we're used to in this part of Cali!! Had some really wet snow on my commute home & everybody just freaked out... 45mph on the freeway even though the snow didn't stick at all... you'd think we were in the middle of a blizzard...

Received the prebuilt MPGuino today... Pretty cool little device! Want to get an enclosure on it and want to find a good way to tap into the wiring (probably via a home built OBD1 to OBD1 jumper cable) before I install it... hopefully within a month or so.

NachtRitter · 02-18-2009, 02:10 AM

Hmmm... well, a surprisingly poor tank this last time... only 44.0mpg. I expected I'd get better than that after switching over to the Fed ECU on the VX. Not sure what caused the drop; there are a couple of possibilities:

The installation of the Fed ECU either caused or exposed a problem which results in a very high idle cold and a higher than normal idle at warm temps.
The weather absolutely sucked this last tank, with rain, snow, and very cold temps nearly every day I drove.

I will probably look at swapping the Cali ECU back in this coming weekend (without swapping the LAF sensor) to see if I can narrow down the high idle problem. This should be OK to do as I had read that some (all?) of the '92 Cali Civic VXs already had the 5-wire wide band L1H1 O2 sensor along with the Cali ECU... In theory, the '94 with 5-wire sensor and Cali ECU should work the same as a '92 with 5-wire sensor and Cali ECU.

Haven't had a chance to get the parts needed for the OBD1 to OBD1 jumper cable yet... Possibly might do that this weekend too.