Last post on Jan 07, 2011 at 9:33 AM
You are in the Subaru Forester
What is this discussion about?
Subaru Forester, Wagon
#26 of 35 Re: Oil filter? [aatherton]
Dec 14, 2010 (2:23 pm)
The filter is a mess to remove, and the header shields must then be cleaned of oil, as well as the ground and your hands.
I agree, Allan, though I doubt I feel as strongly about it. In addition to this, the exhaust piping is likely simplified as it does not need to route around the filter location underneath the car.
The older generations (pre-2005, I think, for Outback - not sure about Forester) routed the exhaust differently (behind the engine rather than in front of it), so there was more room for the filter (and it had a larger casing as a result), but the exhaust also extended further toward the ground, which resulted in less ground clearance and a greater likelihood of damage to the pipes if the car bottomed out.
So, in the 2005+, we ended up with better clearance, but more difficult/messy oil changes.
#27 of 35 Re: Oil filter? [ateixeira]
Dec 14, 2010 (5:52 pm)
"Isn't it 7500 miles with synthetics for 2011+ models?"
For the 2011+ models, synthetic is required.
For the X it is 7500 miles except 3750 miles for severe duty, which consists of stop and go cold weather driving that most people are doing now.
For the XT it is 3750 miles, as the turbo engines are considered to always operate under severe duty.
#28 of 35 Re: 2011 Forester Engine [aatherton]
Jan 01, 2011 (8:52 am)
Concerning item 3, I just read in another forum that:
"The cylinder liners appear to be completely un-attached from the block walls (IE totally wet, no semi-closed anything)..."
#29 of 35 Re: 2011 Forester Engine [aatherton]
Jan 01, 2011 (10:54 am)
Aatherton, what is the implication of that design for the headgasket reliability issue?
#30 of 35 Re: 2011 Forester Engine [daniell]
Jan 01, 2011 (1:46 pm)
There is another quote that may provide the answer:"Cooling has been optimized by using separate engine cooling circuitry for the block and the head, resulting in improvements in fuel efficiency and output characteristics."
Separate cooling circuitry could suggest that there are no water passages sealed by the head gasket which certainly could solve the problem. Similarly, cooling circuit separation distinguishes the 3.6l from the 3.0l engines.
#31 of 35 Re: 2011 Forester Engine [saedave]
Jan 02, 2011 (6:21 am)
That's interesting. Any images of the new heads/gaskets?
#32 of 35 Re: 2011 Forester Engine [ateixeira]
Jan 02, 2011 (7:32 am)
Any images of the new heads/gaskets?
There was a block cutaway on one of the web sites; can't remember which. There were other descriptions that seemed to suggest one or two large block-to-head water connections at the end of the heads and that the heads were not identical on the two sides.
#33 of 35 Re: 2011 Forester Engine [daniell]
Jan 02, 2011 (6:55 pm)
"... what is the implication of that design for the headgasket reliability issue?"
If that poster (in another forum) was indeed looking at an open cylinder block deck, it implies that Subaru has been able to make the cylinders rigid enough not to need semi-closed bracing at the top.
The semi-closed decks of the turbo and diesel engines must be sand cast, which is expensive. Each mold must be made of sand, then destroyed, and the sand cleaned out.
The open deck of the plain old engines was likely chosen for the new FB25 naturally aspirated engine, because it is cast with reusable clean steel die molds. This engine will soon be the basis for the turbo and diesel, too:
"...this new-generation boxer engine... will be positioned as a main engine and the starting point of (Fuji Heavy Industry's) future power unit strategy. Starting with the Forester, the new engine will be deployed in other Subaru products in the future."
#34 of 35 Re: 2011 Forester Engine [saedave]
Jan 03, 2011 (6:42 am)
"Separate cooling circuitry could suggest that there are no water passages sealed by the head gasket..."
The head gasket must still seal across the top of the cylinder block. No matter what the design of the block -- even in the closed deck block -- the water passages around the cylinders must have openings across the deck to allow casting. The head gasket still seals those openings.
But I think you are right in that separate cooling of the heads does allow a much better head gasket, which solves the historic leak problem.
Separate cooling of the FB25 head must mean that those water passage openings in the deck do not go into the head. In the illustration of the new head here, it is a cast pan with a solid flat bottom surface that goes against the top surface of the head gasket. The head gasket bridges over the water passage openings in the top of the deck, and is penetrated only by the tops of the cylinders. This would give the head gasket much more strength and contact area.
#35 of 35 Filter on Top
Jan 07, 2011 (9:33 am)
There is another distinct advantage to having the filter on top which I'm not sure has been touched on here.
Back in 2004-2005ish they switched to a smaller filter due to the older larger filters being too close to the exhaust headers and caused overheating of the oil.
By moving it up to the top of the engine it's much futher from the very hot exhaust so this alone is a great advantage. The filters are also larger giving them greater filtering capacity.
I'm suprised they haven't moved to having a larger sump, this is very common on a lot of new cars these days.