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Power steering delete in 03 Corolla
The following will detail my experiment based on a power steering delete for my 2003 Toyota Corolla CE 5spd.
For those who don't want to read the details of my experiment, let me summarize that this modification resulted in a 3.1% improvement in fuel economy (about 1.5mpg for my corolla).
As a car enthusiast turned penny pincher/eco-modder, I have personally benefited from so much of the information provided by the community here. I wanted to give back by sharing one of the relatively successful modifications I have made to my vehicle. I hope this post can help someone else in their quest for saving money/gas/the world!
The modification tested is a power steering delete via re-route of the serpentine belt:
This modification cost me $13.00 in the form of a Goodyear 4060460 belt from Rockauto.com. I have been running this configuration for a little over a year now. I am hesitant to permanently remove any components of the power steering system in the event that I want to sell my car in the future, and a belt re-routing seemed like the simplest way to experiment with this set-up. I love the way the car handles without power steering! The road feel is much more direct and the corolla is a light enough vehicle that low-speed maneuvering in parking lots is very manageable. On a technical note, this re-route pattern results in the grooved side of the belt running on the smooth surface of the tensioner pulley. This has not resulted in any noticeable wear for either the belt or pulley over the last year/ 12k miles.
The experiment was performed over a 7 mile stretch of interstate, data was gathered using an android phone running the “torque pro” app and twelve total runs were recorded with time, outside temp, coolant temp, engine speed in 5th gear and MPG. The initial “A” set was performed without power steering, the “B” set was performed with the stock serpentine belt, power steering enabled. Again for the second “A” set, the belt was changed to disable power steering. I attempted to control as many variables as possible, however, these results of an on-road test are obviously up to interpretation as to their validity. Some of the possible confounders include outside temperatures dropping during the course of the experiment, slight variations in vehicle speed, changes in wind speed, having to use headlights during the last “A” set, etc. The torque pro app gives a more accurate reading for RPM than for speed, therefore RPM in 5th gear was the recorded measurement in place of speed in MPH. The vehicle speed was 60mph +/- .25mph on the dashboard
Avg A runs (no power steering): 48.76mpg
Avg B runs (power steering): 47.30mpg
The average across all runs without power steering shows a 3% increase from stock configuration. I should have started the experiment a little bit earlier to avoid the confounding factors of dropping temperatures and headlight use during the last phase of this experiment, however, I am reasonably confident that these confounders would simply result in a more conservative estimate of any possible gains to be had. The last south run (A South 4) was probably the least reliable run as I had initially set the cruise about 1mph too slow and tried to compensate with the cruise accelerate feature, which resulted in an over-compensation of about 1mph for about a minute of this run.
Although clearly not a scientific measurement, my overall average economy has improved by about 4% over the last year and 12k miles with this modification and relatively consistent driving habits/ environment. While not a good indication on its own, I think it does lend some credibility to my experiment and the idea of better efficiency without power steering losses. My personal feeling is that a 3% gain is a reasonable expectation for modification of a similar vehicle and could especially be applied to other vehicles with the 1zzfe Toyota motor and hydraulic power steering. Based on a 3% improvement and my own personal driving habits of about 12k/yr, I will save about 10 gallons per year with this modification. Every little bit helps!
I hope this experiment is helpful to other eco-modders; of course, please interpret my results with all due skepticism and take any possible safety concerns into consideration before modifying your own vehicle.
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