So I've been digesting all of this stuff about LSPI, although I will not anytime soon buy a TGDI engine. So... here's my questions/thoughts.
LSPI is a relatively recent phenomenon, brought on by the introduction of TGDI engines. It has almost exclusively affected engines in North America.
The quick and dirty culprit is supposedly the calcium content of oil, as low calcium oils have supposedly passed all the LSPI tests with flying colors.
But what if we go deeper? Even past the obvious TCU programming that upshifts as soon as possible to maximize mileage (that most European cars avoid and also don't have LSPI issues either).
Let's go on the engineering side. One of the detractors of fuel mileage is weight, especially so when in the rotating assembly of the engine. So, as manufacturers have been cutting ounces and grams from the pistons, rods, rings, and valvetrain, they have pushed the rings higher and higher and pushed piston material choices to almost exclusively hypereutectic alloys.
Anyone who has been around performance engine building knows there are several issues with using hyper pistons. Not only are the eutectic alloys capable of lower thermal expansion and running tighter clearances (good), they are extremely brittle to forces like detonation (bad
). You would also know that because they have moved the rings up extremely high and shrunk the skirts to the minimum possible, there is very little thermal mass to the piston to help absorb and disperse some of the heat. This likely leads to an extremely high piston top temperature, which then only exacerbates the LSPI (detonation by any other name). 4032 and 2618 alloys are much more durable under high boost and resistant to the shockwave of detonation.
So, here's my theory: I'm willing to bet that if you were to take an engine type that is most LSPI prone based on manufacturer failures and take two brand new engines. Tear one down and replace the pistons with a set of 4032 or 2618 pistons, and move the rings down to "normal" locations, and increase the weight similar to what is used in similar non-TGDI engines of the same size, and rebalance the whole thing. Then, use the same exact PCM and TCU programming, and stick a high-calcium oil in the engine you changed pistons in, and an SN+ oil in the placebo engine.
Then, run the LSPI tests and purposely do the engine speeds and loads most likely shown to cause LSPI in the parent engine. I'm willing to bet these changes would show it's not so much the oil as it is the extreme chasing of minimizing rotating weight and friction, and the bean counters wanting to cut costs by insisting on hypereutectics instead of forgings.
What thinks the board?
LSPI is a relatively recent phenomenon, brought on by the introduction of TGDI engines. It has almost exclusively affected engines in North America.
The quick and dirty culprit is supposedly the calcium content of oil, as low calcium oils have supposedly passed all the LSPI tests with flying colors.
But what if we go deeper? Even past the obvious TCU programming that upshifts as soon as possible to maximize mileage (that most European cars avoid and also don't have LSPI issues either).
Let's go on the engineering side. One of the detractors of fuel mileage is weight, especially so when in the rotating assembly of the engine. So, as manufacturers have been cutting ounces and grams from the pistons, rods, rings, and valvetrain, they have pushed the rings higher and higher and pushed piston material choices to almost exclusively hypereutectic alloys.
Anyone who has been around performance engine building knows there are several issues with using hyper pistons. Not only are the eutectic alloys capable of lower thermal expansion and running tighter clearances (good), they are extremely brittle to forces like detonation (bad
So, here's my theory: I'm willing to bet that if you were to take an engine type that is most LSPI prone based on manufacturer failures and take two brand new engines. Tear one down and replace the pistons with a set of 4032 or 2618 pistons, and move the rings down to "normal" locations, and increase the weight similar to what is used in similar non-TGDI engines of the same size, and rebalance the whole thing. Then, use the same exact PCM and TCU programming, and stick a high-calcium oil in the engine you changed pistons in, and an SN+ oil in the placebo engine.
Then, run the LSPI tests and purposely do the engine speeds and loads most likely shown to cause LSPI in the parent engine. I'm willing to bet these changes would show it's not so much the oil as it is the extreme chasing of minimizing rotating weight and friction, and the bean counters wanting to cut costs by insisting on hypereutectics instead of forgings.
What thinks the board?
