Toyota MR2 Supercharger

Engine History

Before:

The car in question is a 1987 Toyota MR2 Supercharger imported into the UK from Japan. It was purchased by me in 2001 for 2000, it was known to be a bit rough around the edges but generally sound, it was however known to be clocked. Most likely this was done in Japan before purchase by the previous owner who imported it. Estimated mileage was over 100,000 miles

The engine was known to be good although it did burn a bit of oil on start-up. Other than that it was good and reliable.

Two weeks preceding the track day i had fitted a Blitz Pulley and was generating around 12psi for the most part.

On track:

I had the first session out on track for 20mins, engine felt good and expected no problems. In fact i was just starting to enjoy the car for the first time since i'd purchased it as i'd been working on improving the car considerably as a lot of parts needed replacing (brakes, springs, bushings, steering rack, ball joints etc.)

During this session i heard detonation and i also remember hearing what i'm sure was the sound of the pistons tapping on the head. Although the sounds where worrying there was nothing during the session to suggest there was anything wrong.

Aftermath:

As i warmed the engine up for the next session i noticed large quantities of smoke from the exhaust, it was at this point we knew something was wrong. At first we thought that the head gasket had was failing, but also considered rings and maybe valve stem oil seals.

Due to some very annoying circumstances we had to drive the car back from Elvington to Macclesfield (about 100 miles). Still thinking the head gasket was the most likely cause (the sounds of the detonation wouldn't really ring home until i watched the video back the next day) we decided to drive back after buying 8 litres of oil from a local garage so we could keep topping her up. Strangely as the engine warmed up the clouds of smoke almost disappeared, adding more to the confusion. Oil consumption was still bad, using a few litres on the drive back alone.

The problems didn't appear to be getting any worse as we drove so we continued at a steady speed limiting it to 3000 rpm. We arrived home late Saturday night.

The next day we went out to inspect the engine in detail to decide if we should think head gasket, in which case we would have left the engine in place and just removed the head, or to consider a complete tear-down.

Compression test where confusing, which where very very high (over 200psi). We knew this was from the oil, so surmised that this could only be from three things; 1, head gasket failing. 2, ring damage of some sorts or 3, valve oil seals. The head gasket was discounted as there was no gasses present in the oil and no contamination of the water. Valve oil seals where discounted because the high compression and oil was present on all four cylinders.

So it was decided the damage was to the pistons/rings or cylinder bore. As this meant accessing the bottom end of the engine it meant engine removal was the only option.

A few weeks later and the sun was out on a gorgeous Saturday , with help from a friend the engine was extracted. On Sunday the engine was stripped and we found the problems.

Diagnosis:

It was clear from what we where looking at that we'd suffered from detonation across all four cylinders, most likely from a fuel shortage or failure of the Knock Sensor.

The pistons where black with sooty oily deposits on the crown with a small area burned clean, the outer edge of the piston had warped upwards on the intake side, raising the piston above the deck to make contact with the head. There was extensive pitting around the top edge of the piston and ring lands. Because the piston was warped the rings when when cold would be jammed into the land (this is what caused the oil consumption that cleared when the engine warmed).

Next Steps:

Ok, we knew the block, pistons & rings where screwed. The decision to rebuild the engine was not complicated. The fact that i could use a 2nd hand 4A-GZE engine for around 500 was appealing, it also had its downside. It was an unknown quantity, i would have no idea of the engine condition and could quite likely have problems in the future with it.

Given i had not built an engine before and i like the idea of making a 'as new' engine that should be as reliable as the day it left Toyota i budgeted 1500 to rebuild the damaged one.

 

1997-2011 Mark Nias