98 Civic HX in the HEAT

[BLAZING56k]

Hey guys,

Happy Friday, and Happy Heat Championship!
I'm a proud new owner of a VSM Civic HX with a auto to manual (5speed) swap. Bought it off a friend who said the car gets great gas mileage. So far so good, about 36mpg. I have done some research thanx largely to the this forum, not to exclude its smarty pants users. I need to fix my 02 sensor, go from 4 wire to 5 wire. Previous owner didn't know what he was doing or something. Anywho, I'm here to milk the cow. SHOW ME THE WAY MPG GURUS!

I plan on getting fabbingup some underbody panels and maybe a WAI. kind of counter intuitive, IMO. oh yeah, and the almighty scanguageII.

See you around.

[Gasoline Fumes]

Welcome to EcoModder! WAI in Miami? Isn't all of your air warm?

[brucepick]

Not quite sure what you mean about smarty pants users. Apparently you're a user now, and I never thought of my pants having any smarts. Kinda confused on that one.

Primary oxy sensor is on the front side of the exhaust manifold/cat converter combination.

Mine is originally a 5-spd, has a 5-wire sensor. I've read that autos and/or California HX's had 4-wire sensors, and no lean burn. So don't necessarily blame the previous owner. If the computer isn't set up for lean burn you won't get LB, regardless of your oxy sensor. Sorry I can't provide more specifics because I don't know them.

If you put in a proper HX 5-spd it has taller gearing than other Civics, though possibly the DX and CX have the same tall gearing. So you do have some benefit there even if you don't have lean burn.

[Ryland]

How fast is your engine spinning when going 65 in 5th gear? with the low mileage you are getting something seems wrong, so I wonder if you might not have an HX transmission, or maybe they swapped heavy wide ricer wheels on to the car.
What does VSM mean?

[EricRyan]

You should be getting 40+MPG without breaking a sweat.

[BLAZING56k]

hey guys, thanx for the input.

VSM: Vogue Silver Metallic is the paint color. The cars basically stock, 14 inch HX wheels, 5spd Ex transmission, 5spd Intake manifold, IACV & EGR.

which computer would have lean burn? (code please) The guy i bought it off told me he did the transmission swap (not HX, but EX) with the correct computer (for 5spd HX). But it never dawned on me there was a such thing as a d16y5 without lean burn. Jeez. what a bummer. Hope im not one of them.

anywho, quick question: Do you know if i install an AEM wideband 02 Sensor, is there a way to use this to link into my lean burn mode? A friend has one for sale for 100 bucks. I think a 5 wire from the parts store was like 200-300. I'm under the impression that i have yet to feel the lean burn working. I am staying under 2,500 rpm @ 65mph but have not noticed any jump in mileage to where it should be (40+).

oh yeah, and has anyone else started a Turbo HX tuned for gas mileage? I have some spare turbo parts minus a header, and would like to push this to the maximum efficiency limit.

[brucepick]

Hmmm.

For mpg purposes, the benefit of a turbo is that you can get more power from a physically smaller engine. It weighs less, and depending on how the computer is programmed, you could potentially be light enough on the gas pedal so it will consume little fuel when you don't need the turbo's added power.
So instead of selling you a car with a 1.8 liter engine who's best mpg will be limited by that (higher) displacement, they can sell you a 1.4 liter with turbo. It can burn less fuel than the 1.8 at low output, and when you want to move, 1.4 + turbo is at least as powerful as 1.8 without, if not peppier. Like the Chevy Cruze and Sonic.


Whether it's worth it to spend the time and money in an effort to gain mpg, is very doubtful. Because you're not going to reduce the displacement of your engine if you just add a turbo. You would be adding turbo power to it, along with the turbo's capability of jamming more air and thus more fuel into the same engine. Good for speed, likely not good for mpg.

Your other concerns - oy vay, if you don't mind a couple words of Yiddish. The EX tranny is geared low, for higher rpms. Not your friend if you want more mpg. And yes the computer runs the lean burn capability. If you want HX performance I say you'll need an HX tranny, computer AND wire harness, plus the correct wideband oxy sensor.

You could sell the HX to someone who wants to finish ricing it.

One thrifty approach is just to drive what you have, with the best technique you can put into it. Reduce moving losses with thinner oils, higher tire pressure, LRR tires when it's time for new ones, aerodynamic projects so you're fighting less wind resistance. A fuel cut switch so you can engine-off-coast easier than by turning the key. Killing the engine at any rolling speed reduces rpms really really well, which is why we do it. Only with a standard of course, an autotragic just won't take it.

If you want a serious project, look into things like Megasquirt that might let you map your own lean fuel mixtures and modify the ignition advance, etc.

[turbovr41991]

Originally Posted by brucepick

If you put in a proper HX 5-spd it has taller gearing than other Civics, though possibly the DX and CX have the same tall gearing.

I have owned several Civics from this generation. CX, DX, LX and HX (all manuals. The DX, LX and HX all have shared the same transmissions. The CX has the taller gears and is similar if not the same as the trans they put in the 92-95 VX.

[oey192]

Originally Posted by brucepick

Not quite sure what you mean about smarty pants users. Apparently you're a user now, and I never thought of my pants having any smarts. Kinda confused on that one.

I think this is what he meant by smarty pants users…

[vt_eg]

i could be wrong, but the only gas saving turbo engines i know of are diesel ones. for petrol motors, once the turbo starts to spool, it pushes more air into the engine while the injector duty cycle increases to compensates. so it wouldn't really make sense that it can help save gas

if your boost is below 0psi, it's the same as running a the motor NA. IMO, the turbo would be extra weight that you don't want use if you want to get better mpg

to increase your mpg, i would recommend starting by hooking up a boost/vacuum gauge, and try to keep the vacuum around 10 inHg. after I did that on my civic vx (d15b motor), my FE went from 38 to 42 mpg