Letters to the Editor
Aycharaych
Published Letters: 2087 Editor's Choice: 3
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1969L46
[Read the article: How to get better gas mileage]
[Read more letters about this article: Here]I vaguely remember the L46, was it similar to an L88?
Regarding your point about turbos and torque, we haven't really seen many, if any, otto cycle turbo engines that weren't designed for max horsepower. The reason turbos on diesels work so well at the low rpms that diesels turn is that they are designed that way.
I had a friend that built a turboed 350 Chevy back in about 1974, the turbo was too small for the application for max hp, but the thing had gobs of torque at lower rpm, the turbo just ran out of pumping capacity at about five thousand..
Superchargers are great for producing great heaping loads of torque at low rpm, but since they are driven from the crank they actually hurt efficiency. As I pointed out, the turbo helps efficiency when properly matched to the engine since it reclaims some of the heat energy in the exhaust gases.
Back in 1980 I built a 400 small block Chevy for maximum performance combined with efficiency.. Believe it or not, variable valve timing was available back then for the small block at a very reasonable price.. The system is a specially made set of hydraulic lifters designed to have a leakdown which cuts valve timing at low rpm but acts like regular lifter at higher rpms.. The lifters are still sold and are called Rhodes lifters.
http://tinyurl.com/39cspg
The 400 I built was amazing, it had a moderate performance cam that would normally be kind of lumpy but idled like a stocker and had enough torque to melt the tires on a 73 Vette with a turbo 400 tranny with the stock torque converter. The really great part was that it could get over 23 mpg and still produce considerable horsepower at higher (for a 400) rpm.
The cars today are amazing but they are built for high rpm horsepower and not low rpm torque.. End the horsepower race and manufacturers could build low rpm torque monsters that would really be quicker in about 98% of everyday driving situations for 98% of drivers and would be more efficient to boot.
A properly designed water injection system combined with higher compression ratio and knock sensors would allow more efficiency and still run regular gas.. I know water/alcohol injection has been around since at least WWII and if it was good enough for a V12 Allison aircraft engine back then it should work far better today with modern computer control and combustion chamber design.
Put all the technology together and otto cycle engines could be made to work considerably more efficiently today. Small displacement engine, turbo, cam, intake and exhaust ports designed for low rpm boost with a variable wastegate to keep it from overboosting at high rpm, proper combustion chamber design, water injection to keep detonation under control and still use low octane gas.
I suspect that water injection would help nitrous oxide emissions too since that is a function of high temperatures and the water injection would help keep the combustion temps to a reasonable level at large throttle openings.
There is still room for further development in intermittent combustion engines (turbine guys joke) but marketing forces are keeping efficiency from being addressed as well as it might be. The horsepower wars are very deceiving to the public since most people rarely or never use the full horsepower available in the modern car. High torque at low rpm makes a much more enjoyable driving experience for most drivers and helps overall fuel efficiency.
I guess I should mention that I have a 93 Suzuki Swift GT 1.3 (car) that has a naturally aspirated 1300cc DOHC engine.. The thing is a pocket rocket and an autocrosser's dream since it has incredible acceleration in first gear and basically handles like a racing go kart. Point the front wheels where you want to go and punch it and there it goes, quickly.
I literally can't get it under 30 mpg even with my depleted uranium toenails (like chasing a pack of crotch rockets at 100 plus). If I try to drive efficiently I can get about 40 mpg at 65-70.
The really cool part.. I paid $400 for it and have basically done nothing to it since..
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Ooops..
[Read the article: How to get better gas mileage]
[Read more letters about this article: Here]That was supposed to be nitRIC oxides, not nitrous..
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Trainman
[Read the article: How to get better gas mileage]
[Read more letters about this article: Here]Smart freeway signals can alert drivers on freeways as to traffic conditions up ahead. This will help to prevent traffic "surging" where cars constantly accelerate and brake, wasting fuel and increasing brake wear.
I read somewhere a few years back that the "surging" phenomenon you describe is mathematically very complex and is not really all that well understood.
If you watch, sometimes you will see that some 18 wheelers try to even the surging out by not immediately accelerating in those conditions. The problem with that is that immediately a bunch of cars will dart in front of him and cut him off, thus making his efforts fruitless.
The traffic surging phenomenon is one of the most likely to lead to accidents on the freeway. As I mentioned already, path control is easier than speed control and the surging conditions are a matter of very difficult speed control conditions.