why the early 90s civic VX was able to achieve high mileage

by vanbccomment - 11/20/10 12:41 PM

In Reply to: re:interested in honest debate. by dsq111

guys, hello

i'm just joining Cnet now, in order to post a response. I read car&driver for years, cover to cover, and the VX motor was profiled in spring92 when it was introduced. I still have the issue in my parents' crawl space.

As for all of you guys who claim to know why the VX is able to achieve its rated fuel economy, ALL of you are wrong

as for all of you guys who have completely hijacked this thread, to spout off your view of why this conspiracy theory or why that big-oil whatever, shame on you for cluttering up a perfectly good question.

the answer to the original poster's query should be found in the may 1992 issue of car&driver (plus or minus a month). It should be located in anyone's local main branch of their public library in the 1992 bound edition.

here it is:

ask any mechanic, can you adjust a motor to run rich or lean. the answer is, not any more. with O2 sensors, and fuel injection, all motors are programmed to run stoichiometric, which is adding just enough fuel to burn all the oxygen. previously carburetors were set to run slightly rich, which resulted in smog, and hydrocarbons, and accusations of global warming. running lean, actually saves gas, but the engine runs very hot, and the NOx produced is a direct contributor to smog generation.

emissions controls ramp up, and get tightenend on an annual basis. I spoke to a kid in san fran last summer, he put a turbo on his early-90s miata, he said he did so because when OBD-II came in (I think in 1996), emissions tightened further and it would simply make his miata more difficult to pass smog.

the key here is NOx standards.

running lean (22.0:1 instead of 14.3:1) allows a motor to get 50% better mileage by simple arithmetic. however, it only works if the motor is small enough to pass the NOx standard, which is on a per gram generated per mile basis. this means a 3Litre motor has no hope of passing the early 90s NOx standard, but the 1.5L of the VX (and the 1.0L three of the Honda insight) is able to squeeze through the NOx standard.

other trick were used.

honda designed an elegant VTEC-E version of their VTEC system purely to go lean burn. lean burn only occurred under 2200rpm to keep heat and NOx low. tires were low rolling resistance. wheels were made of FORGED alloy to keep weight low (this is expensive to make, man), the car was a rolling laboratory. the gearbox was a WIDE ratio 5 speed to keep rpm on the highway under 2200rpm for as long as possible, well over the speed limit to extend lean-burn operation.

the car had a tachometer, which base model civics did NOT have back then.
car and driver themselves wrote that gearing was so tall that once they were on the highway in 3rd gear, and didn't notice.


the poster who said it ran on 3 cylinders is wrong. 3 of the 4 valves were used in low rpm operation, one intake valve closed to increase combustion chamber turbulence to effect complete combustion, only opening beyond a certain rpm. (VTEC is usually utilized to create more power at high rpm, here it was used to maximize efficiency down low). all four cylinders are always in use.

all frills were removed from the car. excess airbags weren't included or federally mandated at the time. side impact protection beams had just been mandated and were included. cars like this (and my 1991 miata) simply aren't this light any longer.

bottom line:
the technology NOW exists to run all motors LEAN using direct injection and compterized monitoring. HOWEVER, for car makers to build it, the government will have to RELAX the strict NOx standards, accept a little more NOx, and people will have to, pretty well overnight, accept smaller motors.

Kudos to those manufacturers bringing in high-output four cylinders (think of the nissan juke's 1.6L turbo cranking out 180hp) with wide-ratio transmissions and speccing a VERY tall 6th gear overdrive ratio to push highway fuel economy up.

this past summer I drove twice from vancouver bc to san fran, all my highway passing was done in 5th gear. this makes NO sense. what is the point of a 5th gear, if it is so short that one doesn't need to downshift to pass? think of all the fuel wasted in 5th gear, during the entire time that i'm cruising and not passing. the same goes for my miata. sure, i'm getting 30-35mpg on the highway, but what is the point of the little motor wailing away at 4000rpm at 70-75 mph, when it could be turning 2500rpm and i could be getting 40-45 mph.

for reference, the new juke with automatic turns 2400rpm at 70mph cruising.

cars are designed for the era in which they were sold.
back in the 90s and early 2000s, fuel economy was NOT a priority because gas was cheap. this is why the VX and original insight never sold, why SUVs came to dominate, and why wide-ratio transmissions were never specced.

now that the landscape has shifted................the opposite is occurring.

if anyone has anything to say about big brother conspiracy theories, and how the big business lobby group affects government policy for their own benefit, look into how the CAFE fuel economy standards were frozen for over 25 years (the big domestic 3 lobbied against any increases, because their cars were more inefficient), and the US government let the CAFE standard sit in the mid-20s for over 2 decades (BOTH parties by the way, i'm canadian), now, when fuel prices are going up (as they did in the 70s) the standard is getting ramped up almost impossibly. (see Corporate Average Fuel Economy in wikipedia or google it).

this is the best example of the knee-jerk nature of government, not responding until it is too late.