blitz

The only thing that comes to mind is possibly cooling fan(s)?

Manufacturers ARE beginning to include cold-air intakes that draw from the fender well. All too often it's the aftermarket big thinkers that do a lot of the developmental footwork with interesting innovations, then the manufacturers just take it. The three stages that truth passes through: 1. First it is ridiculed. 2. Then it is violently opposed. 3. Finally it is accepted as self-evident. Oh well.

Here's a cut & paste of one of the papers I gleaned from: 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 (normally represented by “n”) 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 (smaller value of “n”) will occur by installing a shorter rod or by increasing the stroke. A reduced angle (larger value of “n”) 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.

I'm honestly not sure about bike rod/ stroke ratios. As far a I've been able to learn on this subject, a short rod can rev high as long as the ports have the ability to build the neccesary maximum velocity, and modern crotch-rocket motors do have those short, straight, carefully worked-out port-shapes that are light-years ahead most of production car engines (deficiencies in port-design are more obvious with a shorter rod). I would think that a dedicated high-rpm design would ideally favor a short stroke in combination with slightly longer rod if space permitted. I'm not an authority on any of this stuff, but there's a lot of white-papers available at the touch of a search button. That's how I pulled up the info to conclude that Subaru trades a bit of fuel efficiency in exchange for overall engine width.

Lycoming 0-320-B Bore: 5.125 Stroke: 4.125 Displacement:320 ci (5.25 liters) Compression Ratio: 8.5:1 Power: 160 hp Rated Speed: 2700 rpm I couldn't find anything on the connecting rod length. I know that the Lycomings are high torque, low rpm motors (I'm assuming that the "rated speed" of 2700 is the redline). No torque figure was given, but I'll take a stab at 300 ft. lbs. When a Subaru motor is converted for av duty, it's routed through a 2:1 gear reduction. I'd imagine that the overall engine width is a constraint in a small aircraft as well as it is in an auto.

Cookie, you're right; 1930's. GM by far had the best, most well-funded R&D department in the 50's through the 70's, and during that period added a lot of authentication to a lot of the previously accepted design theory (e.g. using the see-through quartz cylinder & high-speed movie photography to document abnormal combustion events, etc.). Here's some links on which I base my "stick/ slip", and optimal viscosity commentary: http://www.lubedev.com/articles/friction.htm http://www.lubedev.com/articles/slipstick.htm All said, the boxer 4 layout has a likeable personality. Like you say, it has a good inherent balance, and what small amount of harmonic that is created it is a very pleasing one. It's got a nice snarl at both the intake and exhaust, sits nice and low in the chassis, etc. IMHO, the best configuration for an 8 cylinder is the V8, the best configuration for a 6 cylinder is an inline 6, and the best configuration for a four cylinder is the boxer 4, all open to debate I 'spose. I've wondered how an uneven number of cylinders would function in boxer form; like an H-5, or H-7? But I'm not sure how the crank throws would be arranged.

Thanks Cookie. Actually the first three points that I made are fairly well documented priciples of internal combustion engine design that had all been worked out by 1950 or thereabouts. One can only go so far in either direction with regards to undersquare or oversquare bore geometry and selection of connecting rod length before "falling off the curve" so to speak. The tradeoffs in either direction are fairly linear up to a point beyond which certain penalties rapidly become disproportionately large and Subaru is hugging the edge of that curve. The last point that I made regarding the "stick/ slip" friction is, less well understood (due to insufficent research), and therefore open to rebuttal. Essentially it implies that the rings glide freely through the stroke on a hydrodynamic oil film (thin lubes yielding lower friction losses), but get stuck as they come to a stop, and need to be yanked free (thicker lubes yielding less stick /slip losses). This whole analysis came from an article on choosing the proper oil viscosity for minimum friction, and implied that a given viscosity would show the lowest total friction loss (best economy). Going thicker than optimal was met with a linear increase in (fluid) friction losses, while going thinner was met with a rapid rise in (stick/ slip) friction losses. The feisty, punchy, midrange character of the Sube motor is attributable to the combination of the oversquare bore geomety and short rod/ stroke ratio (and the intake manifold). The short stroke combined with lots of valve area makes for poor cylinder filling at low revs, while the short rods tend to make the power fall off rapidy at the top. A couple things I've noticed about getting efficient operation out of a Sube motor are counterintuitive in that it seems happier and more efficient with a slightly thicker oil (12-15 cst.), and that it likewise seems happier and more efficient at 3000-4000 rpm. 12-15 cst. is p*ss-water to most Ozzies.

OK, here's my thesis: The lower fuel economy is due to mechanical and thermal inefficiencies regarding the engine. Not the boxer layout in itself, but rather the specific implementation. The width constraints that Subaru must contend with in stuffing the boxer into a front-engined topography, forces the use of a big-bore, short stroke (oversquare) cylinder dimension as well as short connecting rods which results in a somewhat low rod/ stroke ratio of 1.65. The thermal losses are accrued two ways: 1. The large bore creates much aluminum surface area for thermal energy to be lost through; a. the combustion chamber roof into the cooling system and; b. through the piston crown into the oil. 2. The low rod/ stroke ratio results in comparatively less dwell time of the piston near TDC during the early part of the power stroke. Since the piston is moved away from TDC quicker, the combustion event has less time to impinge upon the piston, causing less transfer of force to the piston, which slightly deteriorates the engine's thermal efficiency. The mechanical losses are friction related and are likewise accrued in two ways: 1. The low rod/ stroke ratio (short rods) results in proportionately higher angularity of the connecting rods during certain parts of the stroke, yielding greater side loads between the piston and cylinder wall, causing friction. 2. Piston ring frictional losses in general tend to be greatest at TDC and BDC by way of a phenomenon known a "stick-slip". The oversquare bore/ stroke dimension means a large ring with a large stick-slip friction area. The oversquare bore/ stroke dimension means reduced piston speeds at all points in the stroke including the stick-slip zones in the vicinity of TDC & BDC. The increased dwell time in the stick-slip zones gives rise to much stick-slip losses. I believe I'm correct, but I know there's folks on this board that know a lot more about engines than I do, so I'm open to rebuttal and whatnot (mostly the whatnot).

Here in the Detroit metro area I see a lot of folks driving what appears to be (to me anyway) other manufacturers interpretations of the Subaru, only bigger and heavier. Apparently the AWD sportwagon with ground clearance is suddenly hip to everyone.

I just looked again at the Volvo stats and the mileage figures I listed of 24 city, 31 highway are manufacturers PROJECTED ESTIMATE. Doh! Looks like a red herring, sorry 'bout that. OK, even so... plugging-in the less optimistic Edmunds figures given by Dude, the same dilemma exists; the heavier vehicle with the bigger engine and more cylinders, is making more power and still using less fuel. Now the highway figures I can understand on account of the Volvo having less aero drag and a taller top gear. It's the city figures that are more difficult to explain away with the torque converter wasting energy as heat and a heavier vehicle to move away from stoplights, and most of all... this fuel economy thing is a pattern. So I'm not starting a gripe thread, I'm just trying to figure out the one thing that is consistently unique about the Subaru which would account for the tendency to consistently use more fuel, all else being equal. I have my own theory (which I've partially mentioned before), but I'll hold off until everyone's had a chance to chime in. I'll try to come up with a few more comparos. I seem to recall recall some AWD mini - utes using a normally aspirated V6 in the displacement range of 2.7-3.0 liters, weighing 500 lbs. more, equalling or bettering fuel economy of my 2.5 OBS.

I pulled the figures for both vehicles from Car & Driver magazine. The Forester; August '03, and the Volvo; September '04. I've seen C&D's figures to be innacurate from time to time, so I hope that's not the case. As far as where the power delivery is, the Volvo's peak torque is @ 1500rpm with zero turbo lag, the Subaru's is @ 3600rpm.

I've kinda been watchin' for a suitable candidate model from another company to compare against a Subaru for fuel economy. Let's try this: Volvo V50 T5 AWD / Forester 2.5XT AWD ------------------------------------------------------------------------- Weight: 3552 lbs. / 3289 lbs. Displacement: 2521 cc / 2457 cc Type: Turbocharged I-5 / Turbocharged H-4 Horsepower: 218 hp / 210 hp Torque: 236 ft. lbs. / 235 ft. lbs. Transmission: 5 auto / 5 manual EPA City: 24 mpg / 18 mpg EPA Highway: 31 mpg / 23 mpg The Volvo weighs 263 lbs. more, has 64 cc greater displacement, has an extra cylinder, makes more horsepower and torque, is saddled with an automatic trans, yet still manages to get 35% better fuel economy. Why?

How about a car seat material that's more resistant to the chocolate coating that falls off the protein bar that you eat on the way home from the health food store? Could be part of an optional "active lifestyle" package or something.

Auto-Rx Visit: http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=forum;f=5 Use the board's search engine to pull up posts on the product Auto-Rx. It's amazing the number of people who thought they had worn rings be surprized to find out they had basically had a stuck, coked-up ring pack. At least 10 gazillion (or thereabouts) people have had their compression come back and their oil consumption come down. I'll second 99obw's suggestion to use a 15W-40 HDEO fleet-oil like Pennzoil LL. Use it during the Auto-Rx treatment, then continue using afterwards to keep things clean.

What Ranger said! If you live in an area with really bad roads (MICHIGAN) the nice, light, crisp steering afforded by higher pressures can unfortunately be offset by the tendency to patter, skitter, & annoyingly false-trigger the ABS in corners, so if that's the case, you gotta compromise and drop the pressure a bit to keep the contact patch planted a little better. So many variables.

Josh, agreed. The hotter stat temps are tied to emmissions regs, primarily hydrocarbons. IMHO, the problem with NABISCO is the poor S/N ratio. There's a few really knowlegable people that get drown out by a plethora of yuks that hash & re-hash false internet-tech.

Here's a quote from Jim Bell (founder of Kenne-Bell Superchargers). "• 130 degree hotter air charge from exposed underhood filters can result in 14% (1% for every 10 degrees) decrease in horsepower."

We've both removed the coolant hoses from the throttle bodies on our engines because we both know that adding heat (by any means) to the intake airstream costs power. I've discovered a paint-on, chemical-resistant, thermal-barrier which I intend to apply to the inside of my manifold and intake ports to keep the intake air cool (as soon as I locate a spare manifold). After I do that, I may swap back to the 192* thermostat. But until then, the 180* is the best I can do to reduce intake manifold and port temperatures.

I used the calculation and driving impressions. Before you begin howling, allow me to explain. I make a living on my ability to make subjective judgements (audio) and I've gotten good at getting past the mental gymnastics that go along with it. A couple summers back I fabricated a set of 1/2" thick intake manifold thermal spacers in an attempt to reduce the intake manifold heat-soak power losses. It was painstaking work to trace out and router the parts by hand (I used a really hard & dense paper-based phenolic). I secured the necessary extra manifold gaskets and longer intake manifold bolts, and after installing the spacers and driving around for a day, I pulled 'em back out. Why? Simply, they made my car slower. Granted, it was only a little tiny bit slower, and given the amount of time and work that went into the project it would've been tempting to convince myself that the car was actually a little faster, but I don't play that game. The mistake was that I used the gaskets (rather than the ports themselves) as a template to cut the spacers, causing turbulance in the ports. I've said it before, I got suckered into buying an e-ram electric supercharger. After installing the unit, I routed the activation switch temporarily into the cockpit so I could control activation manually, then took a drive, came back and pulled the e-ram out. No bones about it, it made the car slower. It might've been only a 2 ft. lb. loss in torque, but I could feel it. I wanted very badly to feel more power with the e-ram installed but it wasn't there. Bottom line is that I'm just being honest about what's worked for me and what hasn't. I've got no reason to BS.

Exactly. The stat I've installed doesn't contribute to holding the vehicle in the fuel-wasting, open-loop mode any longer than the stock stat does. Reason: the stat I've installed remains fully closed until the transition to closed-loop's been made. I make no mention of "earlier" anywhere, somehow you managed to interject that. If a person were to install a stat that opened at a temperature below the ECU's switchover to closed-loop mode, it would have the effect of holding the vehicle in open-loop longer or possibly indefinitely (depending on ambient temps and how cold the stat is). That's not a good thing. When I come to a stoplight and there's no airflow, the coolant temp rises to the fan's on-temp. When the vehicle is back in motion, the coolant temp drops back to the point dictated by the stat, PROVIDED: that the cooling system's capacity has not been exceeded. Matt, c'mon now. The torque loss to heat buildup in the aluminum intake is painfully obvious. It's an accepted fact that a 10* F reduction in air temp is equivalent to a 1% increase in air density. I'm not discovering magical gains with what I'm doing here, I'm just struggling to prevent losses, in small increments. You yourself have done the TB bypass in seach of a 3 degree reduction in intake air temp. Why? Me thinks you just trying to pick a fight at this point, but if you're engaging in playful banter, OK I'll play along. Mmm..., I just went back and re-read my earlier post (the one in question here), and I had the term "open-loop" & "closed-loop" erroneously switched at one point. Apoologies if that causedconffusion.

The analog voltage from the temp sensor tells the ECU when to change from open loop to closed loop operation. I don't know exactly what the threshold figure is, but I'd always heard it was right around 160* F. The genuine Fujji stat I installed lists it's opening temp as 160* F which would explain why I'm not experiencing any adverse effects on fuel mileage (It's not forcing my motor to stay in closed-loop any longer than the stock stat does). I spend virtually no time idling or sitting in traffic jams, and have adequate airflow through my radiator. True, that when the vehicle is not in motion, the coolant temp will climb towards the "on" temp of the fans, except that now I have a 12 degree head start, which means that my fans aren't forced to come on very often. This saves the fans and it saves the energy to power the fans. My combustion chambers operate a little cooler, the intake ports are a little cooler, and the power-robbing heat-soaked aluminum intake manifold runs a little cooler. I have a cooler air-charge entering my cylinders. Net result: 2 free Ft. Lbs. of torque and one point lower octane requirement (which I take advantage of by advancing the timing a little to obtain even more torque). So here in the middle of failure stories, you have a success story. When it's time to replace this stat, I'll probably use the same part again (if it's still available).

The weakest link on modern cars (especially with accumlated mileage) is easily the integrity of the wiring harness and connectors. Just have a look at the diagnostic section in the rear of the Subaru manual. 9 out of 10 proceedures for tracing down possible causes for the indicated codes end up being for checking continuity between two points. Before you get into a parts-swapping fit, get a multi-meter and a Sube manual and do some harness checking.

Vivid Racing is where I got mine, but I've seen it elsewhere. It's pricey. http://vividracing.securesites.net/catalog/product_info.php?cPath=1_5_9_98&products_id=203&osCsid=b6442b8f55cb0f44a4f3ab2279dd9269 It says "for WRX", but I'm using it in my '02 2.5.

I'm running a cooler stat. The stock one says: 78* C (172* F), the replacement says: 71* C (160* F). I believe these are cracking temps not fully-open temps. The reason I went to a cooler stat was to reduce spark knock and to provide a hedge against head gaskets. I've seen numerous cautions not to use anything but a genuine Fuji stat on a Subaru, so I was careful to get the Zero/Sports which is a Fuji. I'll post a link.

Thanks 99, I learned something new.