FSRBIKER Posted July 1, 2008 Share Posted July 1, 2008 So for this last tank of gas I changed one habit in my driving and it returned a +3 MPG difference, in fact I don't ever recall getting over 25 MPG in my Outback. I have a 26 mile commute each way and there alot of lights plus there are plenty of downhill portions to work. All I did was to push the clutch in or take it out of gear and coast down hills, I will also pay attention to upcoming lights and do the same thing. I can tell when I should do it if I pay attention to the exhaust sound, I can hear the engine braking/slowing me down when the exhaust has a resonating sound. I still accelerate the same, which is I get on it for first and second and into third gear so my driving habits haven't really changed I just pay attention to the road conditions/exhaust sound. I also don't hold up traffic(I do drive fast most of the time) and only coast when I can. I find myself catching up to the cars in front of me now all the time so I now know how much the engine has been slowing my car down. Now for some new plugs and wires with hopefully even better results. Link to comment Share on other sites More sharing options...
frag Posted July 1, 2008 Share Posted July 1, 2008 So for this last tank of gas I changed one habit in my driving and it returned a +3 MPG difference, in fact I don't ever recall getting over 25 MPG in my Outback. I have a 26 mile commute each way and there alot of lights plus there are plenty of downhill portions to work. All I did was to push the clutch in or take it out of gear and coast down hills, I will also pay attention to upcoming lights and do the same thing. I can tell when I should do it if I pay attention to the exhaust sound, I can hear the engine braking/slowing me down when the exhaust has a resonating sound. I still accelerate the same, which is I get on it for first and second and into third gear so my driving habits haven't really changed I just pay attention to the road conditions/exhaust sound. I also don't hold up traffic(I do drive fast most of the time) and only coast when I can. I find myself catching up to the cars in front of me now all the time so I now know how much the engine has been slowing my car down. Now for some new plugs and wires with hopefully even better results. I do pretty much the same thing when it's possible. Next step is a sail. Link to comment Share on other sites More sharing options...
FSRBIKER Posted July 1, 2008 Author Share Posted July 1, 2008 I forgot I am also going to remove the cross bars too see if that helps any. Link to comment Share on other sites More sharing options...
nickb21 Posted July 1, 2008 Share Posted July 1, 2008 I could be mistaken, but I could have sworn I read before (maybe on this board) that when "coasting" in gear, the fuel injectors either cut or reduce fuel consumption (since the moving of the car keeps things rotating). Hopefully someone can chime in with the right knowledge. Cheers. Link to comment Share on other sites More sharing options...
SubPar Posted July 1, 2008 Share Posted July 1, 2008 "I also don't hold up traffic(I do drive fast most of the time) and only coast when I can." THANK YOU! I'm tired of getting stuck behind hypermilin' fools that take 10 city blocks to accelerate to 25 mph. Makes me want a push bar... Link to comment Share on other sites More sharing options...
FSRBIKER Posted July 1, 2008 Author Share Posted July 1, 2008 I accelerate like normal which is definitely anti-hypermiling. If the fuel injectors reduce fuel when coasting it certainly isn't anywhere close to the improvements i had. Link to comment Share on other sites More sharing options...
OB99W Posted July 1, 2008 Share Posted July 1, 2008 For any of you who care about it, keep in mind that out-of-gear coasting isn't legal in lots of places. http://www.cleanmpg.com/forums/showthread.php?p=115724 Link to comment Share on other sites More sharing options...
FSRBIKER Posted July 1, 2008 Author Share Posted July 1, 2008 That would be a real tough one for a police officer to prove, I certainly wouldn't shut my engine off while driving though...that's dangerous. I am going to experiment with my tire pressure as well, first up to the max listed on the sidewall and see how the car handles/drives in different situations including rain. Link to comment Share on other sites More sharing options...
EVOthis Posted July 2, 2008 Share Posted July 2, 2008 i was just reading something about this today on http://www.comcast.net i just started coasting today alot also.....its amazing how your speed picks up too...... Link to comment Share on other sites More sharing options...
njdrsubaru Posted July 2, 2008 Share Posted July 2, 2008 could it (coasting) cause any damage to the 4EAT? neutral to drive and vice-versa constantly Link to comment Share on other sites More sharing options...
aircraft engineer Posted July 2, 2008 Share Posted July 2, 2008 no - unless there's something "different" about Sub ATs - the issue is that without the engine running, the pump isn't "pumping". It used to be that there were a front pump and a rear pump - it was why you could "push start" an car with an auto (like the old Chev powerslide). No more rear pump - so no lube if the trans is turning in gear OR IN NEUTRAL (which is how a lot of ATs get fried - flat towing in NEUTRAL). With the engine running, it doesn't "care" - oil flows thru the system just fine. Can't hurt it coasting in neutral with the engine running Link to comment Share on other sites More sharing options...
subaruplatt Posted July 3, 2008 Share Posted July 3, 2008 Did a 7.5 liters per 100 km or 31.4 mpg U.S run a week ago. Highway cruise at 119 kph or 74 mph. Test run of 152 Km used 11.4 liters. Cold tire pressure 34 lbs back 37 lbs front. 2/3 of the time with AC on full. 5/30 mobil synthetic, which I think is helping. Ambient temp ranged between 21˚ and 26˚ C. Would be neat if the torque converter could glide on demand a little better. Surely Subaru could make a remap of the auto software expressly for this with no engine breaking. Would feel like a ford custom probably:lol: Then again I love engine breaking! Still is the only car I know of that lets me shift the auto with cruise control on! Automatic hill down shifting cruise control would be a plus and so easy to add. But then again I am probably there to do something! Lately I'm switching to synthetic oil and increasing factory tire pressures within reasonable limits, and employing better cruising habits. Greater efficiency also would be seen if tire pressures could be regularly above 40 psi. But in some instances wheel hop would be prohibitive. Nitrogen shocks would better deal with the even harder tires. By my logic better weight balance would also be a factor limiting wheel hop and could indirectly contribute to better fuel economy. Link to comment Share on other sites More sharing options...
idosubaru Posted July 3, 2008 Share Posted July 3, 2008 Still is the only car I know of that lets me shift the auto with cruise control on! really? i just assumed all cars could do that. even the first 4EAT subaru used in the late 1980's does that. that's in my XT6's and they allow shifting while retaining cruise speeds as well. Link to comment Share on other sites More sharing options...
FSRBIKER Posted July 3, 2008 Author Share Posted July 3, 2008 The tires are now inflated to 44psi(max sidewall rating) and the cross bars are off for this tank. On shifting an auto to neutral and back is there a safety to prevent from going into reverse? I don't know what a Subaru auto shifter gate looks like if it's a straight up/down pattern or if you have to push a button on the handle to go into reverse. Now on my wifes Toyota Sequoia if I just take my foot off the gas and cruise the instant MPG readout will go to 99mpg in about 2 seconds, I doubt putting it in neutral would help any since the tach also reads around 800 RPM's. Do the newer Subie's with the computer MPG readout give an instant or just avg MPG? Link to comment Share on other sites More sharing options...
hooziewhatsit Posted July 3, 2008 Share Posted July 3, 2008 I could be mistaken, but I could have sworn I read before (maybe on this board) that when "coasting" in gear, the fuel injectors either cut or reduce fuel consumption (since the moving of the car keeps things rotating). Hopefully someone can chime in with the right knowledge. Cheers. Yes, that should be correct. While coasting in neutral, the engine needs gas to idle. When coasting in gear, the throttle plate is closed, so it doesn't need any gas at all. I look ahead and coast in gear as much as realistic. -Dave Link to comment Share on other sites More sharing options...
OB99W Posted July 4, 2008 Share Posted July 4, 2008 This thread is getting more interesting. I'm going to play "devil's advocate", and pose some hopefully thought-provoking (and not flame-war-starting) questions. What is engine braking? If an auto trans with no rear pump can't back-drive the engine, can there be engine braking on a car so equipped? Is torque converter operation a factor in this? If coasting downhill with an auto trans in "neutral" resulted in considerable speed, how (if at all) would a 4EAT or 5EAT be affected if shifted back into "drive"? How does engine braking convert energy to heat? If it does so by compressing air, where does that air come from? If the throttle is closed, how does air to be compressed get to the cylinders? (Is the "closed" throttle really closed?) Are the "on" portions of fuel injector cycles the same when coasting as at idle? If lessened, by about what degree with a manual versus with an auto trans? Link to comment Share on other sites More sharing options...
frag Posted July 4, 2008 Share Posted July 4, 2008 This thread is getting more interesting. I'm going to play "devil's advocate", and pose some hopefully thought-provoking (and not flame-war-starting) questions. What is engine braking? If an auto trans with no rear pump can't back-drive the engine, can there be engine braking on a car so equipped? Is torque converter operation a factor in this? If coasting downhill with an auto trans in "neutral" resulted in considerable speed, how (if at all) would a 4EAT or 5EAT be affected if shifted back into "drive"? How does engine braking convert energy to heat? If it does so by compressing air, where does that air come from? If the throttle is closed, how does air to be compressed get to the cylinders? (Is the "closed" throttle really closed?) Are the "on" portions of fuel injector cycles the same when coasting as at idle? If lessened, by about what degree with a manual versus with an auto trans? There was a long discussion in january (in which I was a participant) around a similar problem. Here are two links: http://www.ultimatesubaru.org/forum/showthread.php?t=82266&highlight=compression+braking and http://www.ultimatesubaru.org/forum/showthread.php?t=83815&highlight=compression+braking Link to comment Share on other sites More sharing options...
SOOBOUTLAW Posted July 4, 2008 Share Posted July 4, 2008 I believe normal engine vacuum at idle would be 18-22" HG. 28" HG is a full vacuum. Link to comment Share on other sites More sharing options...
OB99W Posted July 4, 2008 Share Posted July 4, 2008 There was a long discussion in january (in which I was a participant) around a similar problem. Here are two links:http://www.ultimatesubaru.org/forum/showthread.php?t=82266&highlight=compression+braking and http://www.ultimatesubaru.org/forum/showthread.php?t=83815&highlight=compression+braking Thanks for the links. I think they help make the point that engine management significantly closes down the injectors during coasting. So (for example), upon seeing a light turn red, as long as taking your foot off the throttle allowed you to reach the light (hopefully without slowing too much and annoying the drivers following you), you'd in theory use less gas than if you shifted to neutral. Link to comment Share on other sites More sharing options...
subaruplatt Posted July 4, 2008 Share Posted July 4, 2008 The tires are now inflated to 44psi(max sidewall rating) and the cross bars are off for this tank. Be careful or you might be tending towards over-inflation. I wouldn't go any closer than 4 lbs from the maximum to allow for highway/hot weather expansion. Link to comment Share on other sites More sharing options...
frag Posted July 4, 2008 Share Posted July 4, 2008 Its funny how quickly you can retrain your right foot at 4.00 plus a gallon gas to do that nipper Imagine what 5.60 a gallon can do... (price of fuel here in Montreal) Link to comment Share on other sites More sharing options...
OB99W Posted July 4, 2008 Share Posted July 4, 2008 I brought up the topic of back-drive/engine-braking because I've noticed that those on the forum claiming better average gas mileage than I can get with my own '99 are often driving earlier '90s models. I began to wonder if there was a design difference that would explain it, and there might be. Back-drive is primarily determined by the existence/engagement (or lack thereof) of one way clutches (OWC). According to Subaru literature, engine braking operation is different with Phase-1 and Phase-2 4EAT transmissions -- the Phase-2 design eliminated OWC 3-4. I developed the following engine braking (during coasting) info based on: http://endwrench.com/images/pdfs/4EAT.pdf http://www.endwrench.com/pdf/drivetrain/02Winter4EATTransOp.pdf Transmission ranges below are in the form (Selector Position) / (Engaged Gear). Examples: "D/3" = Selector in Drive position, transmission actually in 3rd gear "3/2" = Selector in 3rd position, transmission actually in 2nd gear Phase-1 4EAT (pre-1999) operation: D/4--------------- Engine braking D/3 or 3/3-------- No engine braking D/2, 3/2 or 2/2---- No engine braking D/1 or 3/1-------- No engine braking 2/1 or 1/1--------- Engine braking Phase-2 4EAT (1999 and later) operation: D/4--------------- Engine braking D/3 or 3/3-------- Engine braking D/2, 3/2 or 2/2---- Engine braking D/1 or 3/1-------- No engine braking 1/1---------------- Engine braking (Note that if you want engine braking in 1st, select "2" or "1" on a Phase-1, or "1" on a Phase-2 -- is that confusing enough? ) So, it could be that gas mileage variation from model year to model year on cars with automatics has something to do with the trans design. The Phase-1 4EAT might coast more freely in most gears. Link to comment Share on other sites More sharing options...
hankosolder2 Posted July 4, 2008 Share Posted July 4, 2008 I don't know the specifics of the Subaru engine management software, but Hondas used to incorporate a full fuel cut when coasting in gear untill the engine RPM dropped to 2500 rpm or below. The best strategy would be to learn the fuel cut rpm threshold, by observing injector pulse width on a scan gauge (or looking the decel fuel cut RPM up). Coast in gear until you reach the threshold, then shift to neutral or declutch. (You'll be able to coast further without add'l engine braking, and the injectors will be on below the RPM threshold anyway.) Nathan Link to comment Share on other sites More sharing options...
subaruplatt Posted July 5, 2008 Share Posted July 5, 2008 Just curious? Does it save gas to go into neutral when stopped at a red light or is it better to just ride the brake? I am assuming neutral is more efficient. Legality aside. Link to comment Share on other sites More sharing options...
nipper Posted July 5, 2008 Share Posted July 5, 2008 Just curious? Does it save gas to go into neutral when stopped at a red light or is it better to just ride the brake?I am assuming neutral is more efficient. Legality aside. Actually neutral does better on paper, but its such a small amount, you would probably wear out the shifter cable before you saw any real gain. nipper Link to comment Share on other sites More sharing options...
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