legacycentral bbs

Hello guys!

I have a doubt/curiosity

Does one of you remember to have heard a subaru engine knocking?
i wanted to know if it is a casuallity or if effectively they are less suceptible to knocking.
I even did a small test, i filled couple of subaru's with VERY BAD quality fuel and i heavily loaded the vehicle and drove it in some highways and inclined road with reasonable hard accelerations and i didn't heard any knocking..

I mean, this is a situation where almost ANY car would have been knocking at least during acelerations, i mean, very popular and famous cars such as camry's, corolla's and accords.

Due this, i had a discusion with a friend, and this(who doesnt know too much about subarus, i really think he doesnt like them at all) told me that it's just casuality....

In my house have been about 6 subarus and about 20 in the family, and i sincerely dont remember to have heard any of them knocking, i thought it could be a casuallity, BUT in my house there also have been some no subaru branded car, and i DO remember then to have heard the knocking at least a little and one time, one of them a 2009 camry that can even smell bad gasoline becasue otherwise would be knowcking as a box full of tools being shaked.

I've never experienced a knocking Subaru from gas, I've head plenty of cold start-up piston slap, rod knock from bad bearings, and valve noise from low oil, but never from bad gas

neither knocking (preignitions nor detonations) due overheatings?

My old non turbo 2.2 overheated pretty bad when I lost a heater hose on the freeway. It sounded like it was knocking afterwards, but after an oil change things quieted right down. I was fortunate I didn't blow a head gasket.

My Touring Wagon will knock terribly if you make the misjudgement of filling it with 89 octane. It was bad enough that I siphoned the gas into one of our other cars and re-filled with 93. Naturally though, a turbo is gonna care much more than any N/A about fuel.

It also overheated on me pretty bad after my turbo swap and didn't knock at all then, just lower power. I was impressed, though for sure I was going to eat a head gasket that day.

A lot really depends on the amount of engine control there is and how robust the engine is. All modern cars have computers that control them. If the tuning parameters are not wide enough to control the engine properly and an "upset condition" occurs it can cause the engine to run improperly, i.e. knock under poor fuel quality. With proper and "wide" enough control the ECU will retard timing so the engine does not knock. Additionally, if you have a very robust engine design, it may be able to absorb variations in fuel quality, ambient temperature, etc without the engine going into an abnormal running condition.

Engine control and robustness are somewhat linked and are contributing factors of the overall design parameters/conditions. For example, Subaru may have a safety factor in their design conditions of 2, where Toyota may only have a 1.5, which means the Subaru engine/control design will typically be more robust under upset or abnormal conditions.