High altitude - what about boosting input pressure?

Oh...just loosen your shoes a little. You'll be more comfortable.

What you are talking about in essence is a "poor man's" supercharger / turbocharger. You will be boosting the ambient air pressure. This plan will eventually take it's toll on engine components that are not designed for any boost and substantially reduce your engine's life. Do you have a plan for any controls for the system to control the boost pressure? A better plan for you is to take the car to the dealer and have them re jet the carburetor to your driving environment. This is a normal problem and they are usually quite well versed in this adjustment and probably do it very accurately. If the 93 Corolla has fuel injection, you obviously have a problem with it as you mentioned the exhaust pipe is black. Many people have move from one local to the other, experienced this condition, and have had to have this adjustment performed on carbureted vehicles. Your engine will thank you, and you will be rewarded with fuel savings, and better performance.

How are they not designed for sea level. That's all I'm talking about.

I wasn't sure if there were kits that would just regulate it to sea level pressure.

EFI, no carb.

Yes, 12% less oxygen seems to be the problem.

That's pretty funny. But your engine should run perfectly regardless of the altitude or temperature.

If not then chances are maintenance and/or repairs were not done properly.

If you have the EFI system, it will automatically compensate for any altitude and or barometric pressure changes, and adjust the fuel to maintain a perfect air to fuel ratio (14.7 : 1). You need to take your car in for service.

So instead of 30 mpg you're looking at 27. Is that really worth worrying about?

If you car has fuel-injection, then it probably won't get much worse mileage than it would at sea level. If it has a carb, take Ph@Boy's advise and have your dealer install smaller jets. He'll know what to do.

But saving 3 mpg will take a looooong time to pay off the cost of the work.

As Ph@Boy mentioned, you are basically describing a supercharger, which has a tendency to shorten the life of an engine that is not designed to be supercharged.

A fuel injected vehicle will compensate for higher altitudes automatically. What kind of fuel economy are you getting? Check to make sure the air flow sensor is not gummed up, make sure the air filter is clean, and use OEM (Denso or NGK) spark plugs, rotor, cap, and wires. Having a car properly maintained, with tires inflated to 5 PSI over the automaker's recommended tire pressure, will do more to improve fuel economy than adding a blower.

understand

standard

But I'm getting 25-30 MPG. It's done the black tailpipe thing since we had 45k miles on it when we bought it. It now has 152k.

Supercharger (belt-driven blower) or Turbocharger (exhaust turbine driven blower) are your two options. Anything else would be an unreliable bodge and doomed to failure.

TRD has Superchargers listed for 2003 and later Corolla - doesn't mean it can't be done on a 93, just that the difficulty rating went up. When you add boost you need to add more fuel, and control the boost pressure so as to not overload the engine.

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If you have had black deposits in the exhaust system for that long, the catalytic converter may be ruined, the O2 sensor(s) are probably coated (coked up) with carbon and your engine is not performing as it should. My advice to you IMHO, would be to take the car in to a reputable Toyota dealer and have them troubleshoot the problem. You definitely have something wrong with the engine. It is not normal to observe black carbon deposits on the inside of the exhaust system, which usually indicate a rich (too much fuel) condition. With the EFI system, it should run flawlessly at any terrestrial ambient condition. If you have this problem repaired your MPG should improve even from what you get now.

Moon Goddess wrote in news:WtadnUne_96SJFDbnZ2dnUVZ snipped-for-privacy@forethought.net:

It isn't. Tailpipes get black as a matter of course from naturally- occurring soot.

Your car's emission control system automatically adjusts the fuel for the available oxygen, and does a very good job of it too.

Likely not.

Consider: You probably get on the order of 28mpg overall. Assume gas costs about $2.80/gal. This means it costs you $2.80 to go 28 miles, or about a dime per mile.

If you were to increase your mileage by 12%, you'd drive a mile for 8.8 cents instead of ten cents. You'd save 1.2 cents per mile.

Driving 50,000 miles under such a scenario would thus save you $600 in gas. I'll bet a supercharger would cost far more to install than $600.

Plus, if you're like most people, it would take you four years to achieve that $600 saving, which would amount to $2.88 per week. It's chump change that only looks big if you extrapolate it over a long enough span of time. Cut out one Starbucks latte per week and there's your savings right there.

There is an alternative that just MAY be possible: nitrous oxide.

Nitrous is used by some racers because it contains lots of oxygen. You could have a "hidden" system installed that only injects the additional oxygen needed to bring the car up to sea-level.

Still, would nitrous be worth the cost? Don't think so.

Finally, keep in mind that few people live exactly at sea level. Most live much higher than that. For example, my area (Great Lakes region) is about 1,000 ft above sea level, which means a 3% drop in oxygen. Compared to me, you're only down 9%, not 12.

Well... Let's modify that 'shorten the life of an engine not designed for it' part with the proviso that the kit has to be properly engineered to match the car and not turned up to extreme levels of HP boost. If done in a conservative manner, you might shorten the Time Before Overhaul life of the engine by a few percent, but not notably.

Turn the boost up to max, overdrive the blower pulley, bolt the wastegate down so the boost is in the "Insane" territory, run Trick

104+ Octane racing gas to cure the detonation issues - sorta, then add a big squirt of Laughing Gas and even more fuel, and yeah, the engines tend to come apart real fast.

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If all their suggestion fails then, you have to get all that gunk out of your engine and exhaust system, use the "Acetone" method, and after that remove your air cleaner and replace it with the Tornado=AE. =3D)

True, although I doubt that there many off-the shelf systems that are cost effective in achieving the OP's desired fuel economy gain.

Not necessarily, this is high altitude, maybe it just runs rich the whole life of the car.

It still exceeds by double, the emissions standards, sometimes by triple.

Yeah, high altitude dude.

Like at 12000 feet? Come on.

Or I could waste a lot of money for nothing.

It still gets the same 25-30 mpg at 152000 miles as when we got it at 45000 miles. It still passes emissions tests by at least 2-3x the limits.

I have driven across Trail Ridge Rd in Rocky Mountain National Park many times without any noticeable problem. The altitude is 12000 feet. Once I drove a car up to the top of Mount Evens at 14000 ft, although I was traveling a pretty slow speed, so I don't know if that is fair test.

I have a 1993 Corolla (1.77 liter 7A-FE engine, 4-speed o/d automatic). For business purposes I record all gas purchases (call me reluctant...). Annual average consumption (miles per gallon) data are:

2000 36.8 2001 38.2 2002 36.5 2003 29.4 2004 34.4 2005 38.9 2006 36.8 2007 34.3 so far.

This 3500-pound automatic fuel-injected car often gets 45 or even 50 mpg on the highway. The averages above include mixed highway/city driving, utility trailer hauling, and (16' canoe) roof loads. I notice that the vehicle does not underperform at high altitudes as older, carb-and-distributor cars would.

Good luck to you up in the high country. - Jack.

What I'm saying is that the less oxygen there is, the more of that black tailpipe you'll see.

But is yours the wagon? This is the 1.8 liter wagon, which I imagine is heavier?