AW11ERIC's Forum Comments

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Performance mods for economy

To add to what rem83 posted about parasitic drivetrain loss;

When I replaced the clutch in my MR2, I decided to go with a lightweight flywheel as well. The stock flywheel weighed in at 16lbs, and I put in a 9lb one with the new clutch. This is considered a performance modification, as it lets the engine revv up faster and gives you better response, etc. However, it also has the added benefit of better fuel economy, as the engine works LESS to give you the same amount of power. I guess the physics term would be rotating mass, and the general idea is you want less of it.

This is also true for rotating mass such as wheels and tires, or even your brakes rotors. Those parts also fall under the term "un-sprung" weight, as they are a part of your car that is not supported by the shocks/springs of the car. Less un-sprung weight is considered ideal in the performance world, and a lot of tuners try to get very light components to go faster. Once again, these mods will also increase fuel economy on a street car, as the engine is going to work less to give you the same amount of power.

If you care to modify your car even more, you could consider lightweight body panels, and lightweight interior components. Realize, however, that these mods often interfere with road safety laws. Your average car seat fitted with all of today's modern technology and luxury weighs a ton. Swapping yours out for a "tuner" style seat can save you a good amount of weight, which computes to better fuel economy.

In my MR2 I removed all of the trunk's carpeting and paneling, as well as the factory spoiler. I then removed the front trunk's (frunk's) carpeting and paneling, as well as the spare tire, brackets, jack and tools, etc. I drive my car in town only, so having a flat is no problem my cell phone can't handle lol. All of the removed hardware turned out to weight over 100lbs combined. And when your car weighs 2400lbs like mine, a 100lb weight reduction is pretty significant. And a note on the MKI MR2 factory spoiler; as far as aerodynamics go, it's a brick wall. It provides virtually no downforce at speed, Toyota really didn't put any R&D into the functionality unfortunately.
posted by AW11ERIC December 3, 2008 at 7:20 PM

Warm Up or No?

It really depends on the car, as others have said. Newer cars seem to require less time to heat up, and the cold-idle RPM is hardly offset from the warm-idle RPM.
With my MR2, I let it sit at least 5 minutes in the morning to warm up a little. My reasoning is it has 190,000 miles on the original engine and transmission, and it uses 20-25 year old technology as far as engineering goes. The seals and gaskets within the engine are more prone to failure, especially if they are exposed to high oil pressure before they are lubricated and expanded from the internal heat of the engine. The cold-idle RPM is also much higher than the warm-idle RPM, this may be due in part to the cold-start 5th injector that operates until the car has reached operating temperature.
I tend to use more gas driving to work without warming up the car, as I live RIGHT off the highway and I HAVE to go 60MPH+ as soon as I leave the parking lot of my apartments. By the time the engine is warmed up I'm nearly to work, and I have to shut if off again. The whole time I'm dumping extra gas during the cold-idle process, and probably causing internal damage to the engine going that fast as soon as I start up the car on a cold morning.
If you are able to drive slowly for a few minutes before you hit the highway, you're probably OK. And if your car does not idle exceedingly high while it is cold, then it is probably more fuel efficient than older cars that idled very high until they reach operating temperatures. Hope my posts makes sense. :)
posted by AW11ERIC December 3, 2008 at 6:56 PM