blitz

Exactly. The textbook definition of "overloaded differential" is wheelspin at one end (not to be confused with overloaded limited slip clutch, which is described as damage caused by overheat and overpressure causing the silicone contents blowing out past the seals).

Yeah, just a good ol' fashioned diff like on an axle. One input and two outputs. Then a limited slip tied across the outputs. Interesting thing I learned from the description is that the plates in the viscous unit actually come in contact with each other when activated. Previously I'd thought that the action was strictly a thickening of the silicone fluid. to wit: "As differential action continues, internal pressure will abruptly increase so that inner and outer plates (alternately arranged) come into contact."

Those detailed views did the trick. Thanks Josh.

Thanks Josh, I've studied the drawing. Do I correctly arrive at the conclusions: 1. The front is "hard-coupled" with no slippage? 2. The rear is subject to the amount of slippage that the viscous unit will allow?

There's a question that came up on alt.autos.subaru that can't seem to get resolved. I've always wondered this myself, but never asked: In regards to the Sube's with the manual-trans AWD like the late 90's Outbacks & OBS, etc. (not WRX): Does the engine drive both the front and rear axle mechanically through a center differential gearset which is paralleled with a viscous clutch, OR: Does the engine drive the front axle directly and drive the rear shaft through a viscous clutch? Read it again.

Here's the actual text of the document. Note that it specifies EXTERNAL COOLANT LEAK. To date, Subaru hasn't even admitted to the existance of an internal leak problem. -------------------------- "WWP-99 Service Campaign - Cooling System Conditioner " "Subaru has determined that certain 1999 through 2002 model year 2.5L equipped Subaru vehicles may experience an external coolant leak from the cylinder head gaskets. This is the result of normal relative thermal expansion and contraction variations of engine parts. As a precautionary measure, SOA is recommending that a special conditioner be added to the engine cooling system to prevent leaks from occurring or to correct existing leaks." "Only early Phase II 2.5 liter engines are affected by this campaign. Phase I 2.5 liter engines (some 1999 model year and prior years) are not affected. Countermeasures applied to the manufacturing process for those 2002 and later VINS not affected by this campaign have eliminated the need for this campaign to be performed on those vehicles." "In the future, it will be necessary to add Genuine Subaru Cooling System Conditioner to the SUBARU vehicle cooling system whenever the engine coolant is replaced. The updated recommended service procedure as well as intervals for coolant replacement will be added to all applicable service manuals. As a reminder, we will include an update page in the owner notification letters that should be added to the Owner’s Manual and Warranty and Maintenance Booklet. We ask you to keep in mind that replacement of fluids (including Subaru Cooling System Conditioner) during inspection and maintenance services are not covered under warranty." "If the vehicle owner has this Service Program repair performed promptly, Subaru will extend coverage under the Subaru Limited Warranty on the vehicle for cylinder head gasket external coolant leaks to a period of 8 years or 100,000 miles, whichever occurs first. Warranty coverage begins on the date the vehicle was delivered to the first retail purchaser. If the vehicle was used as a demonstrator or company vehicle before being sold at retail, warranty coverage begins on the date the vehicle was first placed in such service. As a further condition for this extended warranty coverage to apply, the vehicle owner must have Genuine Subaru Cooling System Conditioner added to the vehicle at any subsequent cooling system services at the interval specified in the Warranty and Maintenance Booklet under the heading 'Schedule of Inspection and Maintenance Services'." "Dealers will automatically be sent an initial quantity of Genuine Subaru Cooling System Conditioner. Dealer bulletins and affected VIN lists will be mailed to dealers in early February 2004. Owner notification letters are scheduled for mailing in stages."

Damn, I'm almost speechless. I'll assume that Subaru will be issuing a TSB regarding 5th (or 6th?) "version of head gasket" any time now.

Scottbaru, I've explained it best I can. I'll suggest that you do some actual research on the subject of Rod/Stroke ratio before claiming it has no effect on piston movement or engine performance. Here's something to get you started. Be careful not to let any of the facts get in your way. -------------------------------------- The ratio between the connecting rod length and the stroke length of a motor greatly affects the way it performs, and how long it lasts. This ratio can be calculated as follows: Ratio “n” = Rod Length ÷ Stroke The rod’s length is measured (for this purpose) from the center of the piston-pin opening to the center of the big-end bore, not overall. There is a small range of ratios for most conventional piston engines: the rod is between roughly 1.4 and 2.2 times the stroke length. It’s not possible for the rod to be the same length as the stroke, and rods much longer than twice the stroke make the motor very tall, and are not practical for most purposes (although used for racing). The rod angle must not encourage excessive friction at the cylinder wall and piston skirt. A greater angle will occur by installing a shorter rod or by increasing the stroke. A reduced angle will occur with a longer rod or a shorter stroke. If the rod length is decreased, or the stroke is increased, the “n” ratio value becomes smaller. This has several effects. The most obvious is the mechanical effect. Motors with low values of “n” (proportionately short rods or long strokes) typically exhibit the following characteristics (compared to high “n” motors): » physically shorter top-to-bottom & left-to-right » lower block weight » higher level of vibration » shorter pistons, measured from the pin center to the bottom of the skirt » greater wear on piston skirts and cylinder walls » slightly higher operating temperature & oil temperature due to friction --------------------------------------------------- There are also differences in how the motor breathes: ---- intake vacuum rises sooner ATDC, allowing bigger carburetors or intake port runner & plenum volumes to be used without loss of response » on the negative side, a small or badly designed port will “run out of breath” sooner » piston motion away from BDC is slower, trapping a higher percentage of cylinder volume, making the motor less sensitive to late intake valve closing (hot cams) ---------------------------------------- Spark advance is also affected: ---- earlier timing (more advance) is required, as the chamber volume is larger (piston is farther from TDC) at the same point of rotation » the motor may also be less knock-sensitive, as the chamber volume increases more rapidly ATDC, lowering combustion pressure (this is useful for nitrous & supercharged motors) ----------------------------------- Effects of Long Rods ---- Pro: » Provides longer piston dwell time at & near TDC, which maintains a longer state of compression by keeping the chamber volume small. This has obvious benefits: better combustion, higher cylinder pressure after the first few degrees of rotation past TDC, and higher temperatures within the combustion chamber. This type of rod will produce very good mid to upper RPM torque. » The longer rod will reduce friction within the engine, due to the reduced angle which will place less stress at the thrust surface of the piston during combustion. These rods work well with numerically high gear ratios and lighter vehicles. » For the same total deck height, a longer rod will use a shorter (and therefore lighter) piston, and generally have a safer maximum RPM. ---- Con: » They do not promote good cylinder filling (volumetric efficiency) at low to moderate engine speeds due to reduced air flow velocity. After the first few degrees beyond TDC piston speed will increase in proportion to crank rotation, but will be biased by the connecting rod length. The piston will descend at a reduced rate and gain its maximum speed at a later point in the crankshaft’s rotation. » Longer rods have greater interference with the cylinder bottom & water jacket area, pan rails, pan, and camshaft - some combinations of stroke length & rod choice are not practical. To take advantage of the energy that occurs within the movement of a column of air, it is important to select manifold and port dimensions that will promote high velocity within both the intake and exhaust passages. Long runners and reduced inside diameter air passages work well with long rods. Camshaft selection must be carefully considered. Long duration cams will reduce the cylinder pressure dramatically during the closing period of the intake cycle. ------------------------------ Effects of Short Rods ---- Pro: » Provides very good intake and exhaust velocities at low to moderate engine speeds causing the engine to produce good low end torque, mostly due to the higher vacuum at the beginning of the intake cycle. The faster piston movement away from TDC of the intake stroke provides more displacement under the valve at every point of crank rotation, increasing vacuum. High intake velocities also create a more homogenous (uniform) air/fuel mixture within the combustion chamber. This will produce greater power output due to this effect. » The increase in piston speed away from TDC on the power stroke causes the chamber volume to increase more rapidly than in a long-rod motor - this delays the point of maximum cylinder pressure for best effect with supercharger or turbo boost and/or nitrous oxide. » Cam timing (especially intake valve closing) can be more radical than in a long-rod motor. ---- Con: » Causes an increase in piston speed away from TDC which, at very high RPM, will out-run the flame front, causing a decrease in total cylinder pressure (Brake Mean Effective Pressure) at the end of the combustion cycle. » Due to the reduced dwell time of the piston at TDC the piston will descend at a faster rate with a reduction in cylinder pressure and temperature as compared to a long-rod motor. This will reduce total combustion. --------------------------------- Rod Ratio vs. Intake Efficiency An “n” value of 1.75 is considered “ideal” by some respected engine builders, if the breathing is optimized for the design. Except for purpose-built racing engines, most other projects are compromises where 1.75 may not produce the best results. There will be instances where the choice of stroke or rod has not been made, but the intake pieces (carburetor, manifold, and head) have been selected. Some discretion exists here for making the rod and/or stroke choice compatible with the existing intake. The “n” value can be used to compensate for less-than-perfect match of intake parts to motor size & speed. The reverse is also possible: the lower end is done, but there are still choices for the top end. Again, the “n” value can be used as a correction factor to better “match” the intake to the lower end. The comments in the following table are not fixed rules, but general tendencies, and may be helpful in limiting the range of choices to those more likely to produce acceptable results. Rather than specify which variable will be changed in the lower end, “n” values will be used. Low “n” numbers (1.45 - 1.75) are produced by short rods in relation to the stroke. High “n” numbers (1.75 - 2.1) are produced by long rods in relation to the stroke.

Jeez, I don't even know where your going with all that, you can research it if you'd really like to know. My simple point being made is: diesel combustion IS slower than gas combustion (flame-travel). It wouldn't be impossible to build an ultra short-stroke/short-rod diesel that started and ran, it's just that the associated geometry needs to be accomodating if the high efficiency of the diesel is to be maintained. That quote you attributed to me isn't my quote. It's someone elses. It works like this: Starting at TDC, the piston is standing still, but by the time it's halfway down the bore it's at it's maximum speed. The effect of rod length to stroke ratio is manifested in the rate of acceleration of the piston from it's standing start at TDC towards it's top speed halfway down the bore. With a shorted rod, the piston makes more sudden movements away from TDC during the critical first part of the stroke, which gives the piston a greater tendency to outrun the flame-front as RPM's climb. This is especially problematic with a slow combustion process like a diesel. If you were to chart the piston movement as a graph, you'd end up with a sinusiodal shape. The specific shapes of of the sinusiods will change as the rod/stroke ratio is changed. Also that second quote wasn't mine either.

Here's a cut & paste from a diesel engine form that makes the point more elequently than I: ------------------------------ "Lets look at one place where an I6 has an advantage: stroke and rod length." "It is a well known fact that diesel fuel is a relatively slow burning fuel, thus the need to use fancy high pressure injection systems and high compression ratio engines to get it to burn properly." "Engines with longer rod to stroke ratios make the burning of diesel easier to do because the piston stays near TDC for a longer period of time, holding the combustion process in a smaller space and keeping it under more pressure. This improves combustion and efficiency." "It also turns out that having a bore to stroke ratio of less than one (PSD is roughly one, Duramax about 1.2, Cat 3056 is 0.8 ...) really helps efficiency because it keeps the combustion chamber small during combustion and it makes more torque for a given cylinder pressure. It also scavenges better." "Usually, this is ofset by a slower engine RPM, but to date the diesel V8s are not running higher redline RPMS than the I6s. I think that the short rods and short strokes of the PSD/Duramax cause the combustion efficiency to go to hell when the RPMS climb. (I'm speculating here.)" "Thus, the long rod/long stroke arrangement of an I6 is considered beneficial by some diesel manufacturers." "Unfortunately, it is quite difficult to build long stroke, long rod V8 diesel engines because the engine gets WIDE really quick. Consider this: the Cat 3056 is about 23 inches from crankshaft center to valve cover. (It has a 5 inch stroke.) If two such cylinder banks (3054) were joined to make a 90 degree V8, (8 litres) the engine would be about 32 inches wide ! (Actually wider, due to exhaust manifolds, etc.)" "It is my guess that the Duramax is the configuration it is (short stroke, V8) so that it would fit into the engine compartment on the GM trucks without changing the bodywork."

While researching my reply above, I hit on some info that might be valuable to some on this board. For anyone that wants to cut, paste, & save, here it is: (it's Bore/Stroke/Displacement first in inches, then in metric.) -------------------------------- Four-Cylinder Subaru Engines -------------------------------- {2.835 / 2.362 / 59.6} / {72 / 60 / 977} These are EA-52 engines used in 1966-1970 Subaru automobiles. {2.992 / 2.362 / 66.4} / {76 / 60 / 1089} These are EA-61 engines used in 1969-1971 Subaru automobiles. {3.346 / 2.362 / 83.1} / {85 / 60 / 1362} These are EA-63 engines used in 1978-1980 Brats and 1977-1989 sedans. {3.622 / 2.362 / 97.4} / {92 / 60 / 1595}. These are EA-71 engines used in 1975-1976 sedans. {3.622 / 2.638 / 108.7} / {92 / 67 / 1782}. These are EA-81 and/or EA-82 engines used in 1980-1989 Brats, 1985-1991 XT coupes, and 1980-1999 sedans. They have the same bore and stroke as the six-cylinder ER-27. {3.461 / 2.953 / 111.1} / {87.9 / 75 / 1820}. These are EJ-18 engines used in 1989-1996 Impreza models. {3.622 / 2.953 / 121.7} / {92 / 75 / 1994}. These are EJ-20WRX engines are used in 2002-present WRX sedans. {3.815 / 2.953 / 135.0} / {96.9 / 75 / 2212} These are EJ-22 engines used in 1990-1994 Legacy models and the 1999-2001 Impreza. They have the same bore and stroke as the six-cylinder EG-33. {3.917 / 3.110 / 149.9} / {99.5 / 79 / 2457} These are EJ-25 engines used in 1999-present Forester, Impreza RS, Legacy, and Outback models; 2001-present SUS models; and 2003-present Baja models. --------------------------------------- Six-Cylinder Subaru Engines --------------------------------------- {3.622 / 2.638 / 163.1} / {92 / 67 / 2672} These are ER-27 engines used in 1988-1991 XT sports coupe. They have the same bore and stroke as the four-cylinder EA-81 and EA-82. {3.512 / 3.150 / 183.1} / {89.2 / 80 / 3000} These are the EZ-30 engines used in 2001-present Legacy and Outback models; also known as the H6-30 engine. {3.815 / 2.953 / 202.5} / {96.9 / 75 / 3319} These are the EG-33 engines used in 1991-1997 SVX sports coupe. They have the same bore and stroke as the four-cylinder EJ-22

Let' be sure that it's understood that BORE/STROKE ratio was my original point (although for expediancy I didn't specify). Subaru EA-81 Bore - 3.62 Stroke - 2.64 Ratio - 1.37 VW TDI 1.8 Bore - 3.19 Stroke - 3.76 Ratio - .85 In order to minimize package width, Subaru boxers are ideally OVERSQUARE. In order to reduce flame-travel distance (diesel combustion speed is naturally slow compared to gasoline), diesels are ideally UNDERSQUARE. Same goes for ROD/STROKE ratio. In order to minimize overall package width, Subaru boxers ideally have short rods relative to their stroke. In order to slow down the piston speed away from TDC(to accomodate the slow combustion speed), diesels ideally have long rods relative to their stroke. Therefore I re-iterate the thrust of my point which is that the ideals for good diesel engine design are at odds with the packaging requirements for an automotive boxer configuration. In fact the packaging requirements force Subaru to build an engine which pushes the envelope for what might be considered "ideal" for even a gas engine.

Glad you're OK. Drivers pulling out into traffic without looking is the reason you won't catch me on a motorcycle ...anymore. WAY too many close calls. I'm not experirenced with body work either, but you might be able to find some halfway decent salvage parts you could bolt-on yourself. The color will probably be different tho, but it beats driving around with crumpled panels. My advice would be to make your decision purely a financial one (factor in the good mechanical condition), but leave the emotions out. Do a little more research on what it'll cost to half-azz fix-it yourself v.s. what you'll get selling it. No need to rush the decision either.

Brian, soak the front of the bolt with penetrating oil for a few days, then secure the engine by sticking a screwdriver through the opening at the rear of the bellhousing and use a 6-point impact socket & a 1/2" breaker bar w/cheater pipe to undo the bolt.

I think they used to be spec'd at 80 ft./lbs. My '02 manual specs it at 130 ft./lbs., that's a substantial difference. Also use blue Loctite on nice clean threads (inside and out).

If the speakers in question are physically bottoming-out at high volume, then "capping 'em off" will remedy the problem. Use the largest value that does the job, unless your deliberately trying to tune out some boxy-sounding low-mids (200-300 Hz), then go smaller. In a lower power system where the amp doesn't have the ability to bottom out the suspension, then there's no advantage to adding caps.

Yeah, the diesel has the high torque/low RPM characteristic perfectly suited to a direct-drive prop arrangement. EJ-25 Subie motor is 28.5" wide at the valve covers, that motor is 36.3". Looking at the power vs altitude graph, it appears to be based on turbo sizing. To keep (thermal) efficiency as high as possible the turbo is sized no larger than necessary.

The TSB on the Impreza rear ball bearings is to replace them with the Legacy roller bearings at the next umm... "interval". That should make it the last time you'll have to deal with it.

It would be kinda neat if Subaru somehow did a diesel. It would put back the cool quirkiness that used to set Subaru drivers aprart from the herd.

IMO the long stroke & long connecting rod requirements of a diesel design run contrary to the width constraints that currently force Subaru to use the shortest stroke and shortest rods possible in their gasser engines.

Found this as part of an "ALL-DATA" regurgitation: (take it for what it's worth.) "FUEL GUAGES ON "E" (10/96)" "Which would you rather have happen. Finding out that your car has more gas in the tank than you thought or getting stranded, out of gas, on the side of the road? Hopefully you're among the thinking people and chose the first alternative. This is Subaru's perspective also. That's why you will find that Subaru has provided a generous "E" on their fuel guages giving the customer an extra margin for error in their driving should they overlook monitoring their fuel supply for too long a time period. This prompts drivers to obtain fuel before they are in danger of running out and getting stranded." ... "Our Owner's Manuals state that the low fuel warning lights come on when there are about 2.3 US gallons left in the tank. Those are 2.3 usable gallons when the light is on steady . There is always some fuel (approx 1 US gallon) intentionally left unusable at the bottom of fuel tanks to help prevent contaminants received during fueling (water, sand, etc) from being drawn into the injection system. This means that between the usable 2.3 gallons left and the unusable 1 gallon left, that there are at least 3.3 gallons left in the tank when the guage reads "E" and the low fuel light is not on steady yet." "On a Legacy with a 15.9 gallon tank, this means that if you fuel your car when the guage reads "E" and the low fuel light is not on steady yet, you will be putting in approximately 12 gallons. This is normal. It also means that if you fuel your vehicle this way you will never get yourself stranded by finding yourself unexpectedly out of gas."

Mmm... let's see, I think I'm getting it ironed out. QUOTE FROM NABISCO FORUM: "Actually most of the DOHC heads produced by Subaru use Shim-bucket style of valve adjustment. This is the same method used by almost all Japanese motorcycle engines and early VW Rabbits and Volvos. It is the most diffilcult system to adjust as you will have to buy a shim kit and special tools to depress the valve while you remove the shim. The SOHC Phase II engines use conventional screw-type roller rockers and is the easiest to adjust." OK, HERE"S THE HYDRAULIC PART: "Subaru did produce a quad-cam 2.5 for one year with hydraulic lifters in 1996 or 97. I spoke to Don Heck (Subaru Master Tech at Irvine Subaru) and he stated that Subaru tried hydraulic lifters in the 2.5 DOHC but for some reason did not continue production." "Shim-bucket valve arrangements are quite compact and have less mass than rocker arm styles and so lend themselves quite nicely to high performance situations. Low mass means higher RPM but at the sacrifice of friction. Thus the reason for the roller rockers on the Phase II engine. Lower max RPM but less friction equals same power and better fuel economy." OK, I was a little bit wrong.

The simplest way to explain it is: if the vehicle in question is the main family vehicle, DON'T mess with it. However, if the vehicle in question is a second "toy", then use Cobb's system. Their HP figures are not exaggerated, but what is assumed is that you (as a gearhead) will gladly accept any "anomalies" associated with building and maintaining a hotrod. It's always been that way. Why? Well, maybe it gets you out of the house ...who knows?

You've got it reversed. Phase I DOHC = Hydraulic. Phase II SOHC = Mechanical. What, ...too much Jim Beam? Yeah, there's really two reasons why a resistor will unsolder itself. Either it'll come loose from heat or from vibration/flexation.

But the original poster was asking about an '01 which has mechanical lifters. The phase II did away with the hydraulics. I think there was one year for the phase I 2.5 Impreza that had mechanical lifters. I have seen posts on that issue, was that you? I think I read that a larger wattage (1/2 watt) resistor should be substituted in?