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Old 12-26-2011, 11:10 PM   #26
Scooby207
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Quote:
Originally Posted by yeos

Oh geez. Turn it on, move it into the garage and turn it off. What do you plan on full throttling it into the garage?
Don't get your panties in a bunch... It's just a question
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Old 12-26-2011, 11:46 PM   #27
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I let it idle for a bit then drive off but keep it under 3k. If I have the patience Ill wait a while for it to warm, or at least til the gauge gets off the iceberg cold indicator
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Old 12-27-2011, 12:02 AM   #28
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Quote:
Originally Posted by blame
Does nobody here have an oil pressure gauge? Lots of people here don't seem to understand how oil viscosity, oil pumps, and fluid pressure work

Very basically: yes you engine will have oil circulation immediately when you start it. You don't wait for 'the oil to start flowing' or 'to build enough oil pressure'

Quite the opposite actually, you entire oiling system is very highly pressurized on a cold start, can be around 120+ psi. Compare that to a hot idle around 25-30 psi and a wide-open-throttle reading of around 80psi (when at normal operating temp). For the thickness (viscosity) of the oil to change and therefore lower the pressure, it needs to absorb heat. If you drive it right away on a cold start, you're just adding more unnecessary pressure to the system, possibly hitting upwards of 140-150psi. This is what causes a lot of random engine leaks.

A block heater can really significantly reduce the time needed for oil pressure to drop, especially in conditions that get well blow freezing (I don't usually plug my block heater in until a good 10-12 degrees below freezing).

My personal 'standard' is 95psi, when the oil pressure has dropped to that, my stock temp gauge has usually moved to at least the lower line of the gauge, and idle has dropped to 1200 or just under. I then drive quite moderately until operating temp, then normally after.

I'm not gonna say that you're an idiot for doing things differently than I do, or that you have to follow my instructions to the letter to avoid blowing up your car. Hey it's your car, do what you want. I just noticed a lot of misinformation and misconceptions about cold starting coming from people that don't seem to have to deal with it that often. I live in northern BC, Canada and I have to deal with it quite a lot. I've lived in places where -40 (same temp in celsius and fahrenheit btw) and below were very common winter temperatures, and still gotten 500,000+km from the car.

Have fun, don't freeze, and remember cold oil is thick-thick oil makes for very high pressure.

-sean
Great write up.
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Old 03-11-2012, 01:56 AM   #29
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Quote:
Originally Posted by blame View Post
Does nobody here have an oil pressure gauge? Lots of people here don't seem to understand how oil viscosity, oil pumps, and fluid pressure work

Very basically: yes you engine will have oil circulation immediately when you start it. You don't wait for 'the oil to start flowing' or 'to build enough oil pressure'

Quite the opposite actually, you entire oiling system is very highly pressurized on a cold start, can be around 120+ psi. Compare that to a hot idle around 25-30 psi and a wide-open-throttle reading of around 80psi (when at normal operating temp). For the thickness (viscosity) of the oil to change and therefore lower the pressure, it needs to absorb heat. If you drive it right away on a cold start, you're just adding more unnecessary pressure to the system, possibly hitting upwards of 140-150psi. This is what causes a lot of random engine leaks.

A block heater can really significantly reduce the time needed for oil pressure to drop, especially in conditions that get well blow freezing (I don't usually plug my block heater in until a good 10-12 degrees below freezing).

My personal 'standard' is 95psi, when the oil pressure has dropped to that, my stock temp gauge has usually moved to at least the lower line of the gauge, and idle has dropped to 1200 or just under. I then drive quite moderately until operating temp, then normally after.

I'm not gonna say that you're an idiot for doing things differently than I do, or that you have to follow my instructions to the letter to avoid blowing up your car. Hey it's your car, do what you want. I just noticed a lot of misinformation and misconceptions about cold starting coming from people that don't seem to have to deal with it that often. I live in northern BC, Canada and I have to deal with it quite a lot. I've lived in places where -40 (same temp in celsius and fahrenheit btw) and below were very common winter temperatures, and still gotten 500,000+km from the car.

Have fun, don't freeze, and remember cold oil is thick-thick oil makes for very high pressure.

-sean
Sorry to bump an old thread, I've been searching around the forums regarding this issue. The new 2012 Impreza no longer has a temperature gauge, instead I get a blue thermometer led light on my dash that turns off when the engine is at normal operating temperature. So waiting 30 seconds or so before driving off should be fine?
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Old 03-11-2012, 01:59 AM   #30
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My '12 impreza wrx has temp gauge
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Old 03-19-2012, 11:06 PM   #31
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I'm just curious how it looks, got a picture?
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Old 03-20-2012, 12:10 AM   #32
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You guys are weird. Wide open throttle all day every day everywhere cold or hot.
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Old 03-20-2012, 12:22 AM   #33
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Oil circulates in a matter if seconds, if you had to wait a minute for oil to circulate in your motor, your bearings would be scored and spun. Start it, drive it easy, once it's warm, give it some love and drive it how it was meant to be driven
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Old 03-20-2012, 04:00 AM   #34
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Quote:
Originally Posted by Tylenol Jones
You guys are weird. Wide open throttle all day every day everywhere cold or hot.
Are you mental?
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Old 03-20-2012, 09:17 AM   #35
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Quote:
Originally Posted by yeos View Post
Oh geez. Turn it on, move it into the garage and turn it off. What do you plan on full throttling it into the garage?
Didn't you know its the new thing to do a burn out pulling into the garage

To be on topic. I let my car warm until my oil temp starts to rise / oil pressure (lower). Reason being is cuz the higher the oil pressure the faster its moving by parts which causes less lubrication.
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Old 03-20-2012, 10:28 AM   #36
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The only idleing my car does when i start my car in the mornings is enough time to set up my ipod, put seatbelt, make myself comfortable and close the garage door. So basically around 20-30 seconds.
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Old 03-20-2012, 12:42 PM   #37
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Quote:
Originally Posted by Garrek11 View Post
Didn't you know its the new thing to do a burn out pulling into the garage

To be on topic. I let my car warm until my oil temp starts to rise / oil pressure (lower). Reason being is cuz the higher the oil pressure the faster its moving by parts which causes less lubrication.
If it is at the same temperature yes. Cold oil is thicker, so to pump at the same speed as warm oil you need huge amount of pressure, more than the oil pump can do consistently. (IIRC oil pump pressure relief is 80PSI) Therefore cold oil is flowing slower than warm oil.

Letting the oil warm up a bit means that the oil pump doesn't need to work as hard to push the oil required for lubrication. I am not quite sure on this, but I also think that if the oil is moving faster, it is not causing less lubrication.
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Old 03-20-2012, 04:17 PM   #38
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If it was flowing slower our gauges would read opposite. So what your saying is that 90psi is not actually 90psi at cold idle. If what you say is true then why not start the car up and give it WOT.
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Old 03-21-2012, 12:24 PM   #39
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Quote:
Originally Posted by Garrek11 View Post
If it was flowing slower our gauges would read opposite. So what your saying is that 90psi is not actually 90psi at cold idle. If what you say is true then why not start the car up and give it WOT.
I think you misunderstood me. I was just saying the highlighted part was wrong because since the oil is so thick on start up it requires more pressure to get it to flow. So you are correct when saying to not rev it to high because you will exceed the oil pump pressure specification and there will be very little oil flow when the oil pump is in pressure relief.

Also see this article on Bob Is the Oil Guy, 5th paragraph. http://www.bobistheoilguy.com/motor-oil-105/ More oil flow is better for lubrication.
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Old 03-21-2012, 01:09 PM   #40
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Basic fluid dynamics seem to be being left behind by some of the people who aren't picking up the concept of cold, thick, high pressure oil.

Go get a squeeze bottle of chocolate syrup.
Squeeze some out with a good amount of force.
Now put the bottle in the freezer for an hour.
Take it out and squeeze it with the same amount of force.
Note the incredible change in resulting pressure and flow characteristics even though the same size opening and force were used.

Your oil is the same type of substance that changes viscosity depending on temperature. The size of the passages it has to pass through in your engine does not change, nor does the amount of pumping force acted upon it by your oil pump.

-sean
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Old 03-21-2012, 01:49 PM   #41
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Well said Sean,

That's what I was trying to say.
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Old 03-21-2012, 01:52 PM   #42
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Originally Posted by i_c_the_light View Post
Are you mental?
no, tokyo drift all day
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Old 03-21-2012, 02:08 PM   #43
the suicidal eggroll
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Quote:
Originally Posted by Garrek11 View Post
If it was flowing slower our gauges would read opposite. So what your saying is that 90psi is not actually 90psi at cold idle. If what you say is true then why not start the car up and give it WOT.
Oil pumps are positive displacement, and at a given engine RPM flow the same amount of oil (same volumetric flow rate, same velocity) regardless of what the oil viscosity is.

The pressure you read is the resulting pressure created by the oil pump trying to force X liters of oil through the orifices in the engine every Y seconds. The thicker the oil, the more force it takes to push this oil through the block, and the higher the pressure will be. The thinner the oil, the less force it takes, and the lower the pressure will be. This is why hot Mobil 1 5w30 that has a few miles on it will idle at 10 psi or less, because that oil is SO thin it just flows through the engine like water.

If the pressure spikes too high (>80 psi), a relief valve opens in the oil pump, allowing the remaining oil to bypass the engine and circulate straight from the oil pump exit straight back to the inlet. As soon as this relief valve opens, the volume and speed of the oil through the engine block is reduced, because a fraction of this fixed amount of oil skips the engine and just circulates through the pump over and over again.

When the oil is cold, it is WAY too thick to be pushed through the engine at the normal flow rate. In fact, it's even too thick to keep the pressure <80 psi with the relief valve wide open. This is why the idle oil pressure spikes to 120+ psi when the engine is cold, it also means you're getting significantly less oil passing through the engine (both volume and speed) than when the oil warms up, pressure drops, and more of the oil (or all of the oil) is actually able to pass through the engine without spiking the pressure too high.



Just like with boost pressure, the engine's VE and boost pressure are inversely proportional for a given flow rate. Raise VE, and your boost pressure goes down and vice versa.

Last edited by the suicidal eggroll; 03-21-2012 at 02:15 PM.
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Old 03-21-2012, 08:09 PM   #44
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Ok then so why would you wanna start driving your car right away without warming it up? If your getting less oil flow with colder oil wouldnt you want to wait tell the oil starts to warm to get more flow?
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Old 03-21-2012, 08:25 PM   #45
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The sooner you start driving it, the sooner the engine and oil will warm up, so the sooner you'll start getting reasonable flow and better protection.

However, you need to make sure you do NOT drive the car hard during this time, or you'll be putting unnecessary stress on the bearings when there isn't enough of an oil film to protect them properly.

I usually start driving my car within 20 seconds of starting it (more like 45-60 seconds if it's <0 F outside). I keep it under 3k RPM until the oil temp reaches 120 F, then under 4k RPM until the oil temp reaches 160 F, then I do whatever I want with it. Keep in mind that the oil takes roughly twice as long to warm up as the coolant. So if it takes you 5 minutes for the coolant temp to hit norm, you should wait at least an additional 5 minutes for the oil temp to hit norm before driving the car hard.
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Old 03-21-2012, 08:40 PM   #46
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See I wait until my oil temp gauges starts moving then I start driving. Maybe its just me being paranoid since I have a built engine.
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Old 03-21-2012, 09:57 PM   #47
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Quote:
Originally Posted by Garrek11 View Post
See I wait until my oil temp gauges starts moving then I start driving. Maybe its just me being paranoid since I have a built engine.
If anything, you should be cold idling a built motor less than a stock motor, piston slap will beat the crap out of your cylinder walls.

I have a built motor too, FWIW
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Old 03-21-2012, 10:52 PM   #48
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Threads like this REALLY make me MAD, Why? Because a cold start at a certain temperature (80*F) is NOT the SAME, as a cold start at an other temperature (32*F and colder)... Rule of thumb that I use having cold started a wide variety of vehicle's/engines at 80*F+ to -45*F

80*F+... You get in the car start, and check mirrors, put it in gear and start driving easy 1 to 2 minutes...
55*F..... You get in the car start, and check mirrors, put it in gear and start driving easy 3 to 5 minutes...
30*F..... You get in the car start, scrape windows, check mirrors, put it in gear and start driving easy for 1 to 2 minutes...
-20*F.... You get in the car start, scrape windows, check mirrors, hum a tune 1 minute, and start driving easy for 3 to 5 minutes...
-40*F.... You pray the car starts, scrape windows, check mirrors, hum a tune for 2 minutes and start to drive easy for 3 to 5 minutes...


That is my sum TOTAL advice for starting a COLD engine...
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Old 03-21-2012, 11:17 PM   #49
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It's really nothing even remotely as complicated as people are trying to make it out to be. These are passenger car engines, not F1 engines. This is one of the reasons why passenger cars run multi-grade oil.

If you want to play it safe, drive easy until your heater blows heat and then you're good to go.
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Old 03-22-2012, 11:06 AM   #50
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Originally Posted by meebs View Post
It's really nothing even remotely as complicated as people are trying to make it out to be. These are passenger car engines, not F1 engines. This is one of the reasons why passenger cars run multi-grade oil.

If you want to play it safe, drive easy until your heater blows heat and then you're good to go.
They aren't big wheels either

Our cars come stock with 75 ft-lb of torque per cylinder, that's 75 ft-lb of torque per rod bearing. A lot of our members are putting out well over 100 ft-lb of torque per rod bearing. F1 cars have on the order of 20-25 ft-lb of torque per rod bearing. That's 1/5 to 1/4 of the stress that we have at full throttle.

The stroke on an F1 engine is only about 1.6 inches, compared to 3.1 inches on our car. This keeps the piston speed low even at ridiculous RPM compared to our engines, which keeps the bearing stress low.

F1 cars also burn through 5+ engines per season, we have one engine that has to last for years.

So tell me again why F1 cars need to run through a proper startup procedure and we don't? What about our engines makes them immune to abuse (and yes, driving the car hard when the engine is still cold is very abusive). When the heater starts to blow heat, your oil is still very cold...

I don't understand how somebody can be a member here for 12 years, see the ridiculous number of spun bearings caused by things as small as some high load detonation, starving the oil pickup for a fraction of a second, or even running the wrong 5w30 oil, and then turn around and say that startup procedure doesn't matter because it's a "passenger car".
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