Re: Repeatedly Running On A Low Tank?

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

On Mon, 09 Jun 2008 14:20:09 -0400, C. E. White wrote: > > >>> Now, this was on a Tercel with a whopping 1.5L, 108 HP engine. >>> >>> What I noticed was a better throttle response off the line (it >>> certainly didn't turn it into a fire-breating monster! But you >>> could >>> feel the difference) and the increase in gas mileage. >> >> Better throttle response, or more noise? I sometimes think the two >> are >> related. It is possible throttle response was improved but it seems >> unlikely. To be honest, I am not even sure what improved throttle >> response means. >> >> Ed > > Here's the intake I installed on the car: > >
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> Here's an OEM style: > >
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BA-0421515-1.jpg > > You can see the outside diameter of the Pilot 'performance' air > filter > pretty much covers the area of the entire OEM style filter. > > Then you have the cone section, which adds about another 1/3. > > Now, for example, let's say the OEM allows 8 CFM airflow. The > performance > filter is ~1/3 larger, so should allow ~11 CFM. (These numbers are > arbitrary.) > > For any given throttle plate opening, there will be more air trying > to > get to the combustion chambers with the high-flow filter than with > the > stock filter. More air entering the chamber should provide better > performance, that's why most people looking for performance try to > get > more air into the intake plenum. > > With a higher airflow at any given throttle plate opening, more air > is > going to pass through with a less restrictive filter. Also, the tube > is > smooth rather than fluted like the stock intake, since noise really > isn't > an issue, so airflow is straight through and not interrupted by the > fluting used to damp the sound. > > Also the tube was designed to place the opening in the end of the > new > filter at the hole in the fender where outside air is drawn into the > stock airbox, and had a heat shield to try to block engine heat. It > was > also well away from the exhaust manifold and plumbing, so the engine > was > being allowed to intake cooler air faster. > > Also, while doing all this I pulled the fuse to the ECM, for about > 20+ > minutes, so when the car was started the parameters were reset to > take > into account the increased air flow. > > Flashing the prom would have taken even more advantage of the > increased > airflow, but I wasn't trying to turn a 1.5 liter engine into a Boy > Racer, > I was just looking for a little better performance than stock.

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.