Originally Posted by Flat6 Innovations

The cold is just one of the variables that play into this. Actual running clearances vary from engine to engine, and the quality of the localism cylinders, and the protective piston skirt coating does, too. The adhesion of this coating to the pistons is a key player in the cylinder failure, as it often occurs first, before the cylinder fails.
No single thing is going to help this scenario. I have tested a block heater kit that we made up, but no one would buy it, and on top of that, when you truly understand the dynamics behind this failure, you realize that engines that are going to die from this are already injured as we talk about this as they have already had the perfect storm set up, and it just has to play out.
This is a failure where luck is the major variable.

The biggest mistake people make is firing the car up in winter and allowing it to warm the cabin before they get in, or allowing too much engine warm up time at idle. This keeps the cold start, and just started enrichment higher and for a longer amount of time. All the while the injectors are dumping excess fuel to help light the catalytic converters off, with help of secondary air injection. This fuel is pure solvent, washing down the oil thats the lifeblood of the cylinders and pistons.

Load= Heat. Get in, strap in, fire up and drive away lightly and the engine will not see nearly as much over- enrichment.

Originally Posted by bazhart

When we first became involved in Gen 2 seizures we measured the cylinders and detected a slow creep inwards at the lower area in the unseized cylinders and measured the same trend above the seized area. We then obtained some engines from crashed cars that had not seized and measured the cylinders and found the same trend.

The cylinder at one end of the blocks was OK, the middle on was smaller and the other end cylinder was smallest - in each set - and where the seizures were.

Ironically the much maligned "open deck" design of the M96/7 engines avoids this type of creep dimension change - but if the wall thickness is too thin doesn't prevent stretching the bores oval in the thrust direction. Was good up to and including the 3.2 versions but after than the cylinders were made thinner and hence allowed repeated strain to allow them to change shape.

The Gen 2 (9A1) engines are proper closed deck designs and that stabilises the cylinder bores but because they are now connected to the external cylinder block casting that can have a downside if the rest of the block distorts with time and alters the bore dimensions.

When any engine alloy material is manufactured there is usually temperature involved (high in castings, less in extrusions etc). Upon cooling the outside always cools first while the inside is hotter and has not yet contracted - so as the outside sets the inside continues to contract and leaves a thermal stress inside all parts of the material.

So when you machine castings, extrusions or rolled materials, anything that allows those stresses to be relieved minutely distorts the shape. In some production, materials are "stress relieved" after roughing out before final machining to eliminate the problem.

After the industrial revolution, large machine castings were left outside for a few years to "weather" - basically to allow heat changes to let the material settle down to a final shape before machining.

Since then no one has the time or resources to produce goods that way and as a result - sometimes and unexpected problem emerges.

The Gen 2 block has large thick cast areas below the cylinder bore (but a homogeneous part of it) where the crankshaft shells locate.

Differences in the way the original casting was produced and its cooling rate in different areas will leave stresses inside those areas.

These stresses are small and molecular but every time there is a temperature change cold to hot to cold - the most minute adjustment may take place in the original machined shape.

To reproduce this under test a manufacturer would have to drive several cars for a few hours them leave to cool right down naturally before repeating the process. Then after several months of this - strip and measure everything.

To reproduce a problem that only emerges after say 9 years of daily heat cycles - would take several years and then if a problem was found - it would have to be modified and the whole process repeated before release to the public. It's not going to happen any more as model changes needed to maintain sales demands product changes too fast for such lengthy testing (that may prove unnecessary anyway).

Instead manufacturers have to keep their fingers crossed and it seems that in the case of this engine a minute change has taken place in some engines.

Each time we were involved in this failure mode it had been driven on a cold day without lengthy warm up times before fast driving.

I would say you need to get the oil temperature up to normal running temperature and then drive for another 10 to 20 minutes, gradually increasing throttle opening before giving the car full aggressive throttle.

We do not know if this problem was found early and something done to eliminate it in newer production, or if it only affected some castings or production runs.

Some manufacturers do carry out freezing and heating cycles on some critical parts to speed up the stress relieving process before final machining - so it might be that those owners living in colder climates (if only in winter) who also drive aggressively in short journeys from cold - may promote more shrinkage sooner than say an owner in warmer (or a more stable annual climate) that warms the car up (or drives less aggressively).

All we can do to date is measure the engines that either fail or we get in for rebuild for some other reason and base our findings on those (which have all been identical).

So this may be a problem that goes away or it may remain rare or escalate with time - only time will tell.

Meanwhile, when we release our 4 litre upgrade - we expect to receive a number of engines that we can measure and update our fact file and analysis from there.

So far it seems a rare problem - insufficient to worry about too much but enough to just be patient before flooring the throttle (as really you should do anyway with any sports car).

Baz