How to fix low compression in a rotary engine

How to fix low compression in a rotary engine

Low compression is an increasingly common problem on the RX-8, as these vehicles are now very old and their average mileage is quite high. This is one of the main causes of hot start problems and can be very frustrating.

There are a number of reasons why your RX-8 may be experiencing low compression issues. The most important cause is wear on the internal components of the engine.

In theory, the RX-8 Renesis engine should be able to go over 250,000 miles and in some cases around the world it has." . Unfortunately, the engine does not respond well to the type of driving the car is exposed to in the UK. This means that idling, especially when driving short distances every day, can cause particular wear on various engine components such as gearbox bearings, apex seals and rotor housings.

A faulty ignition coil doesn't help either, as unburned fuel remaining after an incomplete ignition causes a condition known as "hole washing." The oil doesn't stick to the fuel; instead, the unburned fuel literally washes away the layer of oil that should lubricate your RX-8's seals. The resulting lack of lubrication leads to vibration, which in turn causes excessive wear on the seals and other internal components.

Apex gasket wear is one of the main causes of low engine compression.

Due to the way Apex gaskets lubricate, the center portion of the gasket planes tends to wear faster than their outer edges. Over time, gas escapes from the gasket, as the resulting "rounded" edge no longer adheres properly to the flat part of the rotor housing. This wear can also cause severe damage to the rotor housing.

When the center of the seal is worn, the edges of the seal may bulge slightly. These raised edges exert more pressure (and on a smaller casing surface), causing the casing to "chip" and scrape. The wear often means that they cannot be reused when the motor is replaced.

In some cases, seals wear naturally and vertical wear exceeds the point where the apex seal spring can no longer absorb the clearance, resulting in increased gas leakage and thus reduced compression. This type of wear usually only occurs after 100,000 miles and, if it does occur, it is usually preceded by another type of failure.

 

Each of the causes of low compression produces the same symptoms, the most common of which is the inability to restart the vehicle at operating temperature (the vehicle does not restart within 3-5 minutes of being switched off and must cool down for at least 15 minutes before restarting). Other symptoms can be low power levels and erratic idling. Over time, this can lead to the engine stalling at idle and then refusing to start.

Unfortunately, the only effective solution to the low compression ratio problem is to disassemble the engine and either rebuild it or replace it completely. For more information, please contact us or request our online engine overhaul service.