This sounds like a way to fool the control systems into either a richer or leaner mixture setting.

I suspect the hybrid vehicle ECM would simply adjust the throttle until it had the energy output needed. Meanwhile, the mixiture would be either too rich or too lean and the results would be lower MPG and higher emissions . . . not something I'd recommend.

Personally, I like the electric super-charger approach better. The boost is modest so no intercooler is needed. It can be an 'on demand' case which lets us keep normal MPG. Best of all, the regular engine controls and systems work normally. The vehicle just acts as if the pressure altitude went down a couple of thousand feet. On the high plains, the car should be quite zippy.

Bob Wilson

 

in the old days, messing with the mixture like that would do nasty things like burn exhaust valves... if the hybrid uses exhaust gas O2 sensors, messing around with the mixture might just bring THAT feedback into the loop and counteract it.... i wrote to the eBayer and asked, "i thought the prius' engine control computers limited the rpms to about 4500....
what actual results have been seen with priuses?" if i get an answer (that's printable in a family forum , i'll post it here.)

i LIKE the supercharger idea, though! all other things equal, "fooling the engine" into thinking it's at lower altitude with denser air just means, i'd bet, that it'll put out sea-level levels of power, which might be higher than a mile or two further up.

i also wondered why, or if, the Atkinson-cycle Prius engine couldn't be "educated" to know the altitude, or maybe just by using a preignition knock sensor, to close the intake valves a LOT sooner at high altitude, regaining the peak compression pressures of sea level, just by more vigorously changing the intake valves' timing....

??

 

got an answer already: yep, it fools the air temp sensor....

"If your vehicle has Fuel injection then this will work in your vehicle......

The Progressive Tuner Simply Wires into The Factory harness of the IAT Sensor. (IAT=Intake Air Temperature Sensor) The Module will work with the sensor to provide a new signal to your vehicles computer, or ECU. The ECU then adjusts your air/fuel and timing advance curves to New performance Settings. Our progressive Tuner Eliminates costly parts and installation of ECU components(many ECU mods require you to solder and modify the main board), and still safely and legally provides the same end results. There is NO risk of damage to the engine or electrical system since the modified sensor signal will always remain within the manufacturer's recommended specifications. The module works in conjunction with your vehicles ECU and will not affect engine reliability. Installation is very simple. All instructions are included and install should take about a 1/2 hour. The performance power module can even quickly and easily be removed or re-installed at any time.

Thanks for the email......Let me know......"

 

I agree. The O(2) sensor and exhaust temperature gage should be controlling the mixture. As for timing, I would expect RPM to be the primary determinant.

I noticed he didn't report any Prius direct results. Without at least a scanner and better yet, supporting instrumentation, I wouldn't be terribly interested in testing what is essentially an inaccurate IAT sensor.

With the lower aerodynamic drag from low pressure, the car should scoot.

The intake valves are variable delay. What I don't know is how much it changes the 8:1 compression side ratio. The expansion ratio remains fixed at 13:1. I suspect the difference in compression and expansion ratio is what gives the high specific energy performance (i.e., HP / lb of fuel).

It looks like the "Oil Control Valve" operates the "Valve Timing Controller Assembly." It may be possible to tap or externally control this signal. Before making any active changes, I'd want to monitor it and several other engine parameters to determine how the ECU operates it. I would expect the low-pressure or 'off' position would have the lowest possible compression ratio to make starting easier. Once running, it should move the valves to a higher ratio.

Once the valve control signal is identified, an ordinary compression tester could measure the ranges: starting ratio and operating ratio. As for increasing the compression ratio, it may be possible to use Echo parts. But I'd rather use a supercharger than make those kind of changes.

Living about 700-800 ft. above sea level, more power doesn't help me and would have a negitive impact on MPG. If I lived in the high plains or a mountainous area, I'd be more interested in supercharging and valving changes.

Bob Wilson

 

exactly, Bob... when i first took my Prius to high altitude, (and after i understood the difference between compression ratio and expansion ratio ), i wondered why the TMC engineers didn't make it possible to just close the intake valves 'way earlier when the maximum intake charge was lower density; i.e., at high altitude.

now, i just assume that there's a range where this is feasible for changing the valve timing, and the high altitude rationale just doesn't fit in. if so, so be it.

but, again, an electric supercharger that would pump the intake flow "all the way up to" sea-level pressure certainly couldn't hurt the engine, though it obviously would affect gas mileage.... if you're at high altitude, and there's less air per intake stroke, and the fuel/sir ratio stays within narrow bounds, adding more air would result in more fuel. performance might go up, but mpgs would almost of necessity and physics, drop.

though the tradeoff might be nice...
or how about another dash switch...

 

Back in 1972, I drove another 1500 cc vehicle, a VW MicroBus across the high plains of Wyoming, Colorado, Utah and via Reno to San Francisco. Drafting semi-trailer trucks was not an option, it was manditory to keep at highway speeds.

As for MPG, the impact would be modest and still better than sea level performance. The Prius simulator shows high altitudes give great MPG primarily due to low air drag. Unfortunately, I don't think the simulators report "time to reach passing speed" and maximum speed up an "x% grade" or against a "y MPH head wind." But then I haven't made a through study of the Prius simulators.

Bob Wilson

 

Yes, under normal driving conditions. But in a wide open throttle situation, I would expect that you would drop out of closed loop into an open loop condition. Then wouldn't the fuel and ignition values revert to the preprogrammed base values? If so, the extra fuel delivered due to fooling the sensors would not be counteracted by the O2 sensor? Just hypothysising here.

 

This sounds like a call for an experiment. <grins>

Bob Wilson

 

I could never pass up on an experiment! Unfortunately, since the wife has the Prius now, I'm no longer allowed to experiment with her car. I am working on sometning for the Del Sol, but for better FE, not more power. The target AFR's for the hondas are stioch (14.7:1) only at high vacuums above 18 in hg. Below 18 in hg, the targer afr is 12.46:1. This is probably for good throttle response and relies on the O2 sensor to trim it back. Im planning on changing the target back to 14.7:1 to see if there is an increase in FE. I might also play with the AIT and ECT multipliers to decrease the richness at cold air and coolent temps. Presumably these are done to prevent driveability issues in cold weather but they probably overdo it just to be sure. I am hoping to squeeze out a few more MPG while still meeting the emmissions requirements.

 

Bummer! I have no knowledge of Del Sol systems and am hesitant to offer advice.

GOOD LUCK!

Bob Wilson