Repeatedly Running On A Low Tank?

Bill Putney wrote in news: snipped-for-privacy@mid.individual.net:

Of course you know plastics are made from the garbage that remains once all the useful stuff has been distilled from a barrel of crude... This garbage was priorly dumped as useless before scientists learned how to play with the molecules.

I haven't tried possum yet, but I'm game (so to speak)!

I am pretty sure but not positive that there is a separate sensor for the low fuel warning light.

Well it looks like we are both right...at least in a way.

For older Camrys there is a low fuel switch, but it is part of the fuel level sender unit (not separately replaceable). For the newer RAV4s, there is not a separate switch at all (just two wires feed the computer).

Ed

So why did changing the recommendation alter the behavior of people? If you are going to ignore a 7500/5000 recommendation, aren't you just as likely to ignore a 5k recommendation? I suppose the maintenance required light might help, but I know more than a few people who are comfortable ignoring those as well.

In Europe Toyotas have 10K mile oil change recommendations (see page

12 of ). I wonder why in the US, they specify 5K oil changes. My SO keeps telling me that her old Toyota (a mid-80s Camry) only required 10K oil changes - I think it actually required 7500 mile oil changes, but who am I to argue with her. Either way, it was not the engine that gave her the most trouble, it was the transmission. Ed

To each his own. There is no way I would buy any new equipment with an oil bath filter. I am certain they are not as effective as modern paper filters.

Ed

I don't suppose you have ever tried to use an oil bath filter in a truly dusty enviroment. In my case, the worst case enviroment is picking peanuts. We've had to stop and clean out the stupid oil bath filters multiple times a day and still dirt gets through. The intake between the filter and carb are coated.with oil residue and dust. With modern paper filters, no problems. I can't imagine anyone who would want to go back to oil bath filters. Even when properly maintained, they are inferior to modern paper filters, and if not properly maintained they are a disaster. They may have been state of the art 65 years ago, but their time has past.

Ed

So that people who did heed the recommendation would tighten up a little bit, and those who didn't were SOL...?

"Hachiroku ????" wrote in message news:8PA3k.451$n9.0@trndny01...

You only got increased air flow at WOT. Must of the time the air flow was limited by the throttle opening, not the air filter. I doubt if the difference in overall restricition was more than a few tenths of a psi even at wide opoen throtttle.

Assuming the new filter really did flow better than the stock, the difference in pressure drop through the intake is going to be on the order of hundredth of psi except at wide open throttle. It is true that with a lower pressure drop in the intake system before the throttle plate, you would have increased air flow for a particualr throttle opening. However, increased air flow also implies more power. So to maintian the same speed as before you installed the less restrictive intake, you would just open the throttle a tiny amount less, resulting in the same overall flow through the system, for a particualr speed. I am confident you would not be able to tell the difference in throttle openning to acheive the same power level just becasue you changed the air intake. As far as the engine and the fuel injection system is concerned, until you are wide open throttle, the air filter is largely irrelevant as long as it is in reasonable condition. Feedback fuel injection systems are designed to compensate for changes far more significant that minor changes in the intake tract pressure drop. Just going from Denver to LA would present a much greater change in the pressure seen at the face of the throttle plate than a simple air filter change. In closed loop mode, the PCM adjusts the amount of fuel injected to achieve a certain air/fuel ratio. Unless you change the response of the system to the O2 sensor readings, the desired A/F ratio is not going to change. During closed loop mode the PCM "learns" parameters it uses to correct other inputs when running in open loop mode, so that as sensors drift over time, the system can compensate. Changing the air filter to a less restricitive design might change the reading of the throttle position sensor for a given power level, but this would be compensated for by the PCM after a few minutes of closed loop operation. At any rate, the TPS is not used directly to determine the amount of fuel injected. Its function is to indicate gross changes in the throttle positions. This allows the PCM to anticipate changing conditions. It functions more like an accelerator pump or dashpot than a direct fuel control.

The only time the potential increase in air flow trough the replacement air filter should have made a difference was at wide open throttle. Otherwise it was doing nothing except slightly altering where the overall air flow into the engine was limited.

The fact that you reset the PCM is significant. To bad you no longer have the car. It would be interesting to reinstall the OEM air filter system.

Ed

----- Original Message ----- From: "Bill Putney" Newsgroups: alt.autos.ford,alt.autos.honda,alt.autos.nissan,alt.autos.toyota,alt.trucks.chevy Sent: Tuesday, June 10, 2008 5:42 PM Subject: Re: Repeatedly Running On A Low Tank?

Your car was running in open loop mode during the test. If the car is not in closed loop mode, the PCM is running the engine on a stored lookup table (the amount of fuel injected is determined by the engine rpm, TPS reading, MAF reading). Older systems did not do a particularly good job of "learning" parameters at idle. Still, the air filter, unless really dirty, should not have kept the car from passing. At idle the air flow through the filter is relatively low, meaning the pressure drop across the filter was also low. I suppose the combination of the lower atmospheric pressure at high altitude and a dirty filter could have resulted in an air flow vs. sensor relationship that was not addressed in the PCM's look-up table, resulting in too much fuel for the air flow, causing you to fail the test. Still, if the car was warmed up, the converter should have been able to mask any excess fuel condition. Did it fail because of high hydrocarbons, or high carbon monoxide readings? Was the car originally sold with a high altitude calibration (back then cars sold in high altitude areas often got a different set of parameters loaded to the PCM).

Ed

There is a limit to how much the PCM can adjust the timing. In response to "bad" gas or other factors, the PCM will retard the timing (and in some cases adjust other parameters) to try to eliminate the pre-ignition. But it the gas to really bad, or the other factors are excessive, you can still get pre-ignition. I've had it happen myself.

Ed

And at 45 MPG, right now it really *IS* too bad I still don't have the car!!!

Yeah, me too. That's why I avoid the 'bargain' gas stations.

I did know to make sure it was good an warmed up before I got there. IIRC, they rev'ed the engine to something like 2000 or 2500 rpm for several seconds and held it while the testing computer sampled the exhaust. I believe also that a second part of the test was at idle. You're saying that at idle, it would have been open loop regardless?

I could not tell you what parameter caused it to fail.

I do not believe there was any high altitude issues with taht car, i.e., that there was any sort of kit or flash available for it. It certainly ran well, even in 16k feet mountains near Denver. I do recall, it being turbocharged and fuel injected, the amazing difference between how it and the carbureted Chevy Citation V-6 I had at the same time ran at the

10k plus heights.

There is one other possibility that I can think of: I bought eh Sube with 140k miles on it, and though I sold it years later with over 275k miles on it with the original turbo unit and engine running as well or better than it did when new, I suspect that the turbo shaft seals leaked a little. Perhaps, with the intake fan of the turbo unit between the air filter and the throttle body, the extra vacuum on that from a partially restricted filter would have pulled oil thru that seal and that that is what made it fail the test. If that were the case, I would guess that high hydrocarbons would have been the problem.

One other factor: Coincidentally, the particular inspection station that I used was like 3 blocks down the street from Burt Subaru - the largest volume Subaru dealer in the U.S. at the time (turbocharged and 4-wheel drive Subarus were very popular in Denver because they did well going up into the mountains near Denver). Perhaps the special knowledge that the tech had about replacing the filter to pass the test was specific to turbocharged vehicles, or turbo-charged Subarus in particular (perhaps they all leaked a little oil from the shaft seals at higher mileage). But that also is pure speculation on my part.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Ed - Be carefull of your terminology. Pre-Ignition and Detonation are two very different (although also closely connected) problems. Spark timing has no effect on pre-ignition other than the fact that if you advance the timing far enough, the "pre-ignition" will be after the spark. Pretty hard to do that and still have the engine run reasonably well though. By definition, pre-ignition occurs BEFORE the spark.

Pre-ignition CAN cause detonation, and detonation CAN contribute to pre-ignition, but both CAN occur separately from each other.

The PCM can NOT correct for pre-ignition - only detonation.

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Ah- Turbocharged!! No high altitude calibration(because it "turbo-normalizes"-and quite possible it WOULD run open loop at idle.

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