restricted air intake
 

HERE IS A VX ENGINE(94)https://www.fuelly.com/attachments/fo...89f277e989.jpg

50mpg(EPA)

AND HERE IS A DX ENGINE(94)
https://i.ebayimg.com/24/!!fm,q8QBmE~...,4MK0Q~~_4.JPG
FROM:
https://cgi.ebay.com/ebaymotors/Honda...fCarsQ5fTrucks
41MPG(EPA)

THE BOTH HAVE THE SAME STROKE AND BORE SIZE AND BOTH 1.5, BUT AS YOU CAN SEE NOT SO CLEARLY THE AIR INTAKE TUBE ON THE VX IS SMALLER...

I'M NOT CLAIMING THIS TO BE A 9MPG IMPROVEMENT, BUT I'VE PUT A SIMILAR SIZE TUBE ON MY SATURN AND HAD REALLY GOOD EFFECTS AS FAR AS MPG ARE CONCERNED

Wheelbase 101.3" 101.3" 101.3" 101.3"
Overall Length 160.2" 160.2" 160.2" 160.2"
Vehicle Height 50.7" 50.7" 50.7" 50.7"
Vehicle Width 66.9" 66.9" 66.9" 66.9"
Curb Weight 2,390 lbs. 2,178 lbs. 2,094 lbs. 2,108 lbs.
Brakes 4 Wheel Disc 2 Wheel Disc 2 Wheel Disc 2 Wheel Disc
Engine 1.6L 4 Cyl. 1.5L 4 Cyl. 1.5L 4 Cyl. 1.5L 4 Cyl.
Stroke 3.54" 3.33" 3.33" 3.33"
Bore 2.95" 2.95" 2.95" 2.95"
Horsepower 125 @ 6600 102 @ 5900 92 @ 5500 70 @ 5000
Torque 106 @ 5200 98 @ 5000 97 @ 4500 91 @ 2000
Fuel Capacity 11.9 gal. 11.9 gal. 10.0 gal. 10.0 gal.



im begining to think

the VX has lean burn which jumps the a/f ratio to 17:1 during certain conditions. this is specific to the VX and even more, the california version of the VX doesn't have it and the mileage numbers suffers for it.

I think there are also differences in the shape of the head to better swirl the fuel so that you don't get detonation.

there are probably honda guys that can explain it a lot better than me. the VX has a lot of stuff going for it. the original insight also has lean burn which allows it to go to an anstonishing 25:1 a/f ratio (or so I have heard).

great, but anyone have thoughts on restricted air intakes?

maybe a better comparison in the mileage would be the california version VX vs the DX version. the cali version is the same exact motor but with lean burn disabled (because of emissions) so that would be a better comparison as far as what you are concerned with.

EPA of a cali VX vs. EPA of a DX

The VX A/F ratio can go as lean as 24:1. This isn't so astonishing considering that carbureted vehicles can typically go as lean as 18:1 (or even leaner, depending on state of tune) during light throttle applications.

I didn't know the VX went that lean but that is interesting.

I personally am not a honda guy. I know very little about lean burn other than what I have read about on here.

I know very little about carbed motors. maybe that shows my age or perhaps my lack of interest in cars early on in my driving years.

(side note: really like the SI, wish honda would come back out with a civic hatch)

IMO, it's just like the idea of just not stepping on the gas pedal as far. Is there a difference if the restriction as at the throttle plate vs. at the intake pipe?

I have to agree with the other folks here, the differences are far more than just an intake pipe, and I don't think switching the intake pipe would help.

COST-EFFECTIVENESS OF FUEL ECONOMY IMPROVEMENTS IN
1992 HONDA CIVIC HATCHBACKS
University of California
Energy and Environment Division
May 1993

(Compared to the 1991 DX) "...the 1992 VX has 56% higher efficiency. 2"

"2 The latter estimate is for the "49-State" VX sold in all states but California. The stricter emissions requirements in that state made Honda abandon the lean burn technology for VXs sold there, though the California VX still uses the basic VTEC-E engine and the other efficiency technologies found in the 49 state VX. This compromise reduced the efficiency improvement of the California VX to about 51% relative to the 1991 DX, or to 46.9 mpg composite."
COST-EFFECTIVENESS OF FUEL ECONOMY IMPROVEMENTS IN 1992 HONDA CIVIC HATCHBACKS
Energy and Environment Division
University of California
May 1993

The VX also had the VTEC-E motor, which heavily increased combustion chamber swirl in low rpm ranges, by only opening one valve of the two. If you notice, the heads are completely different even visually (VX plugs are in the front, DX plugs in the back).

Far more than intake, the head and the lean burn are where the fuel milage gains are. The narrower intake isn't the reason for the FE, it's just a small part of a large package.