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Old 03-12-2008, 04:46 PM   #26
GeneralTJI
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swear I read somewhere that BOV's make the car run rich. Running rich means more fuel is being used. I'm really not too sure on this one though and don't have the time to look it up.

Rayme I think the block heaters are only like $25 or something? Really not too expensive at all, and seems like it would extend the life of the engine since cold starts are what kills engines
They run rich briefly when they open... but on an auto car, they only open when you let of, not during each shift- I'm sure you knew that already... and under easy driving, they should be adjusted to not open much at all (this will also make sure it doesn't open under vacuum as well)... when a BOV is set up correctly, it isn't going to have much effect on gas mileage on an Auto car when driven easily....

Block heater is another good idea, I've been toying with the idea of throwing one on my car.. although it's starting to get warmer.. maybe for next winter...
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Old 03-12-2008, 05:17 PM   #27
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I'm glad to see all the discussion this thread has started - thanks for all the input from everyone, it's very informative.

With respect to AFR, I agree with brettm's points. I think the ratio itself isn't changing much, but the car is gulping more gas due to the higher density (and therefore total amount) of cold air coming in so that AFR can be maintained. But it seems the car doesn't fully burn this gas - you can really smell it in the exhaust until the car reaches operating temp, so this is why I was saying it is running rich. The AFR may not change, but the car is dumping more unburnt gas to exhaust.

Up here a block heater is pretty much a requirement - once it gets below about -30C you're pretty lucky if your car starts if it isn't plugged in. This winter we had several nights below -40C. CAA (Canadian version of AAA) gets hundreds of calls each time the mercury drops below -30C overnight due to all the no-starts the next day - they just run around giving boosts. My block heater cost $36 at the local dealer, and I paid another shop about $100 to install it (last job I feel like doing on my own when it's -30C out is to drain cold coolant while lying in the snow under the car, remove the block plug, wrestle in the block heater, burp the system, check for leaks etc).

From some of the other replies, it looks like I may just have to grin and bear the poor mileage when the temp drops. Glad to see it's not just me with the lousy mileage (i.e. not a specific problem with my car). Even my 01 Forester gets 22 MPG in the winter! Never thought of it as fuel efficient before...

Next winter I'll try removing the air intake to force warmer under-hood air to be aspirated, see if that helps. And I may block the grill as well. As one of the other posts mentioned, part of the problem is that it takes a while to warm the engine up to optimal operating temp (in my case, about 10 minutes of actual on-road driving (as opposed to simply idling)). So these approaches may help to get up to optimal temp faster. The car that this WRX is replacing is a 2000 Echo - that car really suffers from efficiency drop in the cold, since the motor is so small and the engine takes forever to get to operating temp (30 MPG city in summer, only about 22 MPG winter).

I'll also give the Cobb economy MAP a go, see if that helps. I'm leaning toward the idea that the BOV is not a major mileage killer for me - with my normal city driving, I never hear it, and I don't think it passively vents - only when the boost is high and the throttle drops, which seldom happens in stop-start driving. But I could be wrong. If it turns out that there is some constant venting going on, then going back to the CBV may help (see above comments about a lot of unburnt gas going to exhaust when the car is below operating temp - with the CBV some of this would be redirected back to the engine to be burned instead of being lost to atmosphere, although I would think that this would not be very much). Another possibility is a thermostat with a higher opening temp (lots of people try that trick up here). The idea is that you keep hot coolant in the block longer before it is warm enough to open the stat and go to the radiator, thus warming up the engine faster. The downside is risk of cooking your engine in warmer weather, but since we seldom get above +33C here, that may not be a major issue. If I find some magic combo that helps, I'll be sure to post a thread here.

bomber991: LOL, I used to live in Texas - 3 years in Irving just outside Dallas. This winter, I _really_ missed the weather down there. Of course, the flipside is that you cook your alternator and battery in the summer.
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Old 03-13-2008, 01:28 AM   #28
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In brutally cold weather you can also help the engine warm up by partially blocking off the front of the radiator with a piece of cardboard (ever notice that the truckers have covers over their radiators in the winter time? ) . I also would stuff a towel in the hood scoop to keep from flooding the engine compartment with very cold air. It would also keep the engine warmer much longer when parked.

Don't sit and idle to warm up the car when you start up. Fire the car up, let it run for no more than 30 seconds for the idle to stabilize and oil pressure to come up and then drive off at light load. The engine will warm up faster and have less wear doing this than if you let it set and warm up before you drive, not to mention you will greatly reduce fuel burned at cold idle.

I also run top quality synthetic lubricants in the tranny and rear diff to cut losses due to cold stiff gear lube.

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Old 03-13-2008, 11:19 AM   #29
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Don't sit and idle to warm up the car when you start up. Fire the car up, let it run for no more than 30 seconds for the idle to stabilize and oil pressure to come up and then drive off at light load. The engine will warm up faster and have less wear doing this than if you let it set and warm up before you drive, not to mention you will greatly reduce fuel burned at cold idle.
How exactly do you cause less wear by driving and putting a load on bone cold engine?? of course driving it easy helps, but there is nothing wrong with letting your engine idle for longer than 30 seconds when it's cold outside... your not going to cause any extra wear by letting it idle for a few minutes...
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Old 03-13-2008, 08:14 PM   #30
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How exactly do you cause less wear by driving and putting a load on bone cold engine?? of course driving it easy helps, but there is nothing wrong with letting your engine idle for longer than 30 seconds when it's cold outside... your not going to cause any extra wear by letting it idle for a few minutes...
Because you have much better oil flow and lubrication at normal driving conditions light load than you do at cold idle, and the engine warms up much faster and is not getting all the oil washed off the cylinder walls by a super rich fuel air mixture as it does in cold idle.

It may not sound right to you but it is absolutely true you are causing excessive wear by letting the car sit at cold idle for extended periods of time (you are also killing your fuel mileage). The vast majority of engine wear occurs under cold start and cold idle conditions. Get the engine up to 2000-3000 rpm where it is designed to operate and it gets much better lubrication, and it gets the engine up to normal operating temperature much faster. On my car, It takes only about 1 mile of easy driving for it to show engine temp on the gauge and 2-2.5 miles gets it to normal temp. At 40-50 mph that is less than 3 min run time to get to full operational temp on the gauge. On my car if I let it idle in cold weather, it won't even be showing heat on the gauge for the first 5 minutes of idle.

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Old 03-13-2008, 08:36 PM   #31
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vast majority of engine wear occurs under cold start and cold idle conditions. Get the engine up to 2000-3000 rpm where it is designed to operate and it gets much better lubrication
Better lubrication? My car builds PLENTY of oil pressure at idle when its cold... because the oil doesn't want to flow as well yet.. I realize you understand this. But it's lubricating about as well as cold oil can at that point.. and with next to no load against it. (I do run Redline Synthetic to try and minimize this issue)
But it is somewhat of a tradeoff, the bottom end DOES IN FACT like you better if you let it sit and idle for a few minutes before driving.. The flip side- as you pointed out is the cylinder walls being washed out with fuel, this is true, thats why I don't let my car sit for 20 min idling on a cold day- although, the other thing to think about is- even though it runs rich during cold idle, there is next to no load causing the pistons to wear against the cylinder walls (idling and cold pistons arn't going to build much friction against the cylinder walls- not like getting on it while running extra rich does).. so this washing out and causing wear isn't as bad as it could be.... But I guarantee the bearings in your motor will last longer letting it warm up with very little load against them until the oil has come up at least closer to temp therefore flowing through the bottom end properly.

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and 2-2.5 miles gets it to normal temp
Water temp sure, but your oil isn't up to operating temp in 2 miles...
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Old 03-14-2008, 06:58 AM   #32
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Better lubrication? My car builds PLENTY of oil pressure at idle when its cold... because the oil doesn't want to flow as well yet.. I realize you understand this. But it's lubricating about as well as cold oil can at that point.. and with next to no load against it.
It has oil pressure but not volume flow which is what allows the oil to lubricate. Your engine gets best lubrication at about 1500-2500 rpm, that is why if you don't bring up a new engine rebuild to 2000 rpm and hold it there for 30 minutes some cam shaft manufactures will void the cam warranty.

I am not talking about buzzing the engine up to 6000 rpm, just driving easily at 2000-3000 rpm range. David Vizard and several other very well respected engineers all agree on this as the best way to warm up a cold engine to minimize wear and fuel waste when cold, and I have been doing this for about 41 years now with good success without ever having any bearing problems or oil burning problems. Some of these engines had so little wear on engine rebuild they could have been re-ringed with stock rings, and I could have put the original valves back in as valve stem wear was still within manufactures specs.

You need enough volume flow to allow a proper hydrodynamic wedge to form and cold oil due to its increased viscosity drastically cuts flow rate.

You are correct oil temp lags behind water temp, but that just reinforces the need to get engine temp up quickly so your bearing clearances on the bottom end open up to normal operating clearances.

Larry
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Old 03-14-2008, 11:23 AM   #33
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I have read a David Vizard book myself, and now that you bring him up- that guy is pretty damn amazing. Definitely learned some things there... (pocket porting the exhaust valves on SBC heads, picking up 40HP from something that simple... can't hardly put a price on tips like that!!)

Well, we may take a slightly different approach to warming our motors... but I too can tell you I have had no issues doing things the way I do... for example, I have a turbo 4Runner (factory turbo), I drove that thing very hard, built 19 PSI of hot detonating boost until I finally melted the edges of the pistons off.. it had about 200,000 miles on it when I pulled the motor apart... still had what looked like as much cross hatching as it came with from the factory, no lip, and I checked the bores and they were pretty much perfectly round... bearings looked brand new in the bottom. Of course I bored it for the CP pistons I had, new crank, h beams etc. I've had quite a few vehicles in the 200,000 miles + range and (thank God) not had any issues with bearings or excessive wear / loss of compression etc.

I guess we could nit pick about different methods of warm up, but at least our engines are going through some kind of a warm up procedure every day.. I can't tell you how much it bothers me to see someone fire something up on a cold day and just blast it down the road for all it's got...
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Old 03-14-2008, 04:01 PM   #34
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I was wondering about actual "engine wear" in extremely cold weather, if it was indeed harder than say, a cold start during summer.

When its -20 below zero, the whole parts in the engine would shrink a little, meaning more space between the crank and journals, etc..(and cold metal is actually stronger than warm if I recall correctly) and the oil is thicker..wouldnt that act as some kind of balance..?? I mean wear can't occur unless theres actually friction. I would think an engine reving at 7000 RPM at operating temp would suffer more wear.

Maybe I'm completely wrong.
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Old 03-14-2008, 04:45 PM   #35
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Originally Posted by Rayme View Post
I was wondering about actual "engine wear" in extremely cold weather, if it was indeed harder than say, a cold start during summer.

When its -20 below zero, the whole parts in the engine would shrink a little, meaning more space between the crank and journals, etc..(and cold metal is actually stronger than warm if I recall correctly) and the oil is thicker..wouldnt that act as some kind of balance..?? I mean wear can't occur unless theres actually friction. I would think an engine reving at 7000 RPM at operating temp would suffer more wear.

Maybe I'm completely wrong.
I think oil temp is the biggest issue here.
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Old 03-14-2008, 06:25 PM   #36
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Rayme - one problem with extreme cold is that the metal actually gets brittle. Up in the far north (Yukon, etc where they frequently his the -40s and -50s), the large metal blades on road graders (used to clear snow) have been known to snap off in very cold temps. I've heard of connecting rods snapping when very cold and the car's block heater hasn't been plugged in (although I haven't encountered this myself).

On a previous car I had an oil pressure display - on really cold days it sometimes took several seconds after starting before it actually started to move, since the oil was basically sludge at that point and no real flow (and thus pressure) developed. Scary to think what that is doing to the motor.

You can always tell the really cold days as soon as you get into the car - LCD displays (e.g. clock, radio) are slow to change or light up, seat is often hard as a rock, brakes don't want to work at first, car doesn't want to turn over. Even the steering wheel feels a bit like it's binding. Man I hope winter is over...
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Old 03-14-2008, 07:17 PM   #37
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Oil temp and viscosity is the major issue.

Your bearing clearances will close up when it is cold. The aluminum block shrinks considerably more than the iron crankshaft, so bearings get tighter when the block is cold. Same goes for cam bearings.

In the high mountains and places like Montana, they also have problems with railroad equipment at temps below about -30, couplers break when they try to make up trains and sometimes they get broken rails.

The aluminum block is considerably stronger when cold, but that does not help the basic problem of adequate oil flow. In temps near -30 if you try to pour conventional oil out of a can it is like honey at room temperature. Only the synthetics have reasonable cold flow behavior. In very cold temps folks sometimes leave the engines running around the clock for days or months at a time as they will be unable to restart them if the are shut off and allowed to cold soak.

I know a diesel trucker that shut off his rig in a blizzard in Wyoming and it took a week to get it restarted. They had to tow it into a heated garage and let it warm up before they could get the engine to start. Seriously cold weather is a whole different ball game and sometimes extreme measures are required. Back in the early 1960's we had a brutally cold winter here in Denver that got down to -30 and below in the suburbs. I remember my dad going out to run the car every 3-4 hours during the night. Our car was one of the only cars in the area that would start during that cold snap. A friend of mine had standard single weight Valvoline in his Chevy, and at -25 we could not get it to crank with a 24 volt jump start to a 12 volt battery. We had to warm the oil pan for several hours before we could even get the engine to turn over. It took us almost an entire day to get the car running.

Larry
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Old 03-14-2008, 09:54 PM   #38
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in regards to the OP's post, if I read right, you are only driving 10 minutes each way to work, so I am guessing 1, maybe 2 miles? So as has been said, that is a very likely cause of your poor mileage because your car never really warms up, and you are still running very rich. You might want to fill up your tank, and take a drive of about 60 miles or so on the highway, and see if things improve.

If not, it wouldn't be a bad idea to check your spark plugs, and maybe the front O2 sensor (the ECU uses this to calculate fueling).

Also, as has been mentioned, synthetic oil in the transmission and RR diff wouldn't be a bad idea. Synthetics are inherently thinner, and especially so when it is cold out. This should reduce the amount of energy wasted just getting things turning.

Have you switched to a thinner motor oil? Going to a zero weight motor oil might help, and should give you better protecton at start up. Just make sure that you get an oil that gives you enough protection when things get warmed up too though

Good luck and stay warm.

J. Cooley
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Old 11-23-2012, 10:13 AM   #39
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Found this thread after searching for some winter gas milage threads.

I put got 17.3 MPG (same station, same pump) with mostly city in 30-40 degree temps and a 9 mile commute each way... sitting in a decent amount of traffic.

In the summer, I can get 24MPG highway no problem.

I'm going to get all my driveline fluids replaced ASAP as they're overdue anyways. I bought the car in July with no service history besides having the turbo replaced under warranty. The 4EAT fluid isn't even red anymore.

Glad to see 17.3 isn't totally horrible. Sucks about gas mileage though... all my old EJ22's would get 20MPG even in the winter no problem.. 4EAT too.
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