Regear for lower cruising RPM
Introduction
Lower engine RPM at a set speed means reduced friction losses and increased engine load to maintain a given power output. Higher engine load increases engine efficiency.
Note: This modification is much easier on manual transmissions compared to automatics. There are no reports of automatics being regeared at ecomodder.
A very easy way to improve efficiency with a change in ratio of engine RPM to speed is to install tires with a larger radius.
Contents
Instructions for mod
Information required: How do people perform this modification, pictures, problems, what to look out for
Information required: A listing for different ways to do this if its different on different types of cars
User experiences
Please enter your user name and any relevant data in the table
| User Name | Car Make, Model, Year | Cost of Mod | Time to Perform Mod | MPG Before Mod | MPG After Mod | MPG improvement guess | Instruction Link |
|---|---|---|---|---|---|---|---|
| MetroMPG | Ponteac Firefly 1997 | 65kph-72.9 75kph-64.95 85kph-57.9 |
65kph-79.9 75kph-70.3 85kph-62.85 |
65kph-9.6% 75kph-8.2% 85kph-8.5% Ave-8.8% |
Metro taller transmission swap thread: +5% efficiency gain (taller final drive) | ||
| Big Dave | 00 F-350 XLT | Mod= regear | 20 MPG | 23 MPG | 15% (3MPG) data is tank to tank before/after mod | [[1]] | |
| Big Dave | 00 F-350 XLT | $4000 installed | Mod= add 7th gear (overdrive) | 26.7 MPG | 28.2 MPG | 7% (1.5MPG) ABA testing | [Seventh Gear!] |
| cfg83 | 99 SW2 Wagon | $240 ($140 parts, $100 labor) | 41 MPG steady state |
49 MPG steady state |
20% (at steady speed highway) 21% theoretical gain (steady state highway) from gear ratio change. | [Saturn S-Series 5th Gear Swap] |
Problems / Consequences of mod
- Higher RPM required at speed before shifting into new higher gear and therefore lower efficiency at some speeds.
References
Forum thread links
Taller top gear makes a real difference (10%)
Metro taller tranny swap thread: +5% efficiency gain
