warm up the engine
01-20-11, 04:57 PM
#16
^^I think there seems to be a bit of confusion going on. By "guessing", I mean that the car doesn't know what the output is. I completely agree that maximum power is met during open loop mode just as in the case when the car goes into open loop mode when you step hard on the throttle. Fuel Feedback in this case is ineffective.
What I was arguing was that it is not necessarily true that the added power you feel during a cold start is "because of the tighter tolerances". Shrink fits work in the complete opposite way. They are loose when cold and get extremely tight when warm. The rate of expansion is based primarily on the type of metal.
Also, since the ecu is in open loop, there is no output "check" (no 02 sensor feedback loop). Then the ecu runs a map that has a slightly richer air to fuel ratio and this is the added power you "feel".
Most ecu's strive for a 14.7 afr and slightly higher afr's give you more power....up to a point
So I think the confusion was that I was thinking about stock cars, and you were probably thinking drag racing
Also the cold I was referring to was internals, not air temperature.
What I was arguing was that it is not necessarily true that the added power you feel during a cold start is "because of the tighter tolerances". Shrink fits work in the complete opposite way. They are loose when cold and get extremely tight when warm. The rate of expansion is based primarily on the type of metal.
Also, since the ecu is in open loop, there is no output "check" (no 02 sensor feedback loop). Then the ecu runs a map that has a slightly richer air to fuel ratio and this is the added power you "feel".
Most ecu's strive for a 14.7 afr and slightly higher afr's give you more power....up to a point
So I think the confusion was that I was thinking about stock cars, and you were probably thinking drag racing
Also the cold I was referring to was internals, not air temperature.as far as pistons and types of metal - forged pistons expand when hot so the tolerances actually tighten up the more they run, forged pistons with high amounts of silicon and cast pistons not so much... they actually stay very close in size to where they started, but the engines bore will actually expand a small amount as well when at operating temperature... this is one of the reasons there can be more wear on an engines bore when the engine is cold...
just as an example, when trying to remove something that is press fit, it can help to heat the whole assembly to cause it to loosen... typically the outer piece will expand more so than the inner piece causing it to loosen up...
stock cars, even completely stock cars, are tuned from the factory to achieve somewhere between 11:1 and 13:1 AFR when under heavy loads and/or full throttle... the additional fuel cools the cylinder to prevent detonation... this is done in open loop mode.
never does an ECU even think to look at the O2 sensor data when in open loop, heavy throttle mode... I never said the extra power you could feel... these gains are typically less than 5 hp... but when you are trying to eek out that extra .05 in the 1/4, every bit helps... the reason most cars feel more peppy when they are cold is because you haven't been in it for a while - its 90%+ psychological anyways...
01-20-11, 05:47 PM
#17
I still do it. Soon as I walk downstairs to the door I remote start my car. For the time it takes me to throw my coat on, put the shoes on, grab the cell phones & bag, it is enough time for me to put it in gear and drive off. That boils down to about 2-3 minutes on average. I tend to let the car idle longer on really cold mornings so that I'm stepping into a warm vehicle with the heat being on.
01-20-11, 06:26 PM
#18
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You're saying somewhat of what I'm trying to get across.
So when you first cold start a car, the engine is in open loop mode. While in open loop mode, the oxygen sensors do not provide a feedback loop to the ecu and therefore runs a rich map. It does this to stay within a safe tolerance to not cause any type of damage. Typically, you see an Air to Fuel Ratio of around 10~14AFR during this cold start. The actual fuel [compared to air] that gets dispensed into the engine depends on many factors such as your Revolutions per Minute, your coolant temperature, your throttle position, your pressure, your altitude, your intake air temperature, your miles per hour, your oil pressure...and so on.
This is what I've meant as "guessing". No matter how well a car manufacturer may try to tune a car to run a certain way under open-loop, the truth of the matter is that there is no real way to know the output and THEREFORE they run a bit richer to prevent pinging/knocking/detonation...
As you can see, a slightly richer mixture will yield more power and less efficiency. Once you pass about 12.6 AFR there are no more gains. Here is where I disagree with you, it cannot be a psychological effect since all the evidence is stated and presented.
Granted, cold start operation is getting much better, there is still regardless no way to know the condition of how the engine is running while in open loop.
This is part of a system called Controls. This type of control does not work well during high/heavy throttle and therefore not used. (Hence open-loop during heavy throttle)
Once in closed loop, the oxygen sensors provide feedback to the ecu with regards to its position to stoichiometry (14.7 AFR) and adjusts accordingly. This is where great efficiency can be achieved.
Given all this information above, that is why I ALWAYS let my car warm up for at least 30 seconds before I drive off. And after I do I keep the throttle light until 60% of normal running temperature.
On a side note, press fits/shrink fits work because of expansion rates. These rates depend on the properties of a material, such as: density, coefficients of thermal expansion, modulus of elasticity, modulus of rigidity, and Poisson's ratio.
So when you first cold start a car, the engine is in open loop mode. While in open loop mode, the oxygen sensors do not provide a feedback loop to the ecu and therefore runs a rich map. It does this to stay within a safe tolerance to not cause any type of damage. Typically, you see an Air to Fuel Ratio of around 10~14AFR during this cold start. The actual fuel [compared to air] that gets dispensed into the engine depends on many factors such as your Revolutions per Minute, your coolant temperature, your throttle position, your pressure, your altitude, your intake air temperature, your miles per hour, your oil pressure...and so on.
This is what I've meant as "guessing". No matter how well a car manufacturer may try to tune a car to run a certain way under open-loop, the truth of the matter is that there is no real way to know the output and THEREFORE they run a bit richer to prevent pinging/knocking/detonation...
As you can see, a slightly richer mixture will yield more power and less efficiency. Once you pass about 12.6 AFR there are no more gains. Here is where I disagree with you, it cannot be a psychological effect since all the evidence is stated and presented.
Granted, cold start operation is getting much better, there is still regardless no way to know the condition of how the engine is running while in open loop.
This is part of a system called Controls. This type of control does not work well during high/heavy throttle and therefore not used. (Hence open-loop during heavy throttle)
Once in closed loop, the oxygen sensors provide feedback to the ecu with regards to its position to stoichiometry (14.7 AFR) and adjusts accordingly. This is where great efficiency can be achieved.
Given all this information above, that is why I ALWAYS let my car warm up for at least 30 seconds before I drive off. And after I do I keep the throttle light until 60% of normal running temperature.
On a side note, press fits/shrink fits work because of expansion rates. These rates depend on the properties of a material, such as: density, coefficients of thermal expansion, modulus of elasticity, modulus of rigidity, and Poisson's ratio.
01-20-11, 07:00 PM
#19
You're saying somewhat of what I'm trying to get across.
So when you first cold start a car, the engine is in open loop mode. While in open loop mode, the oxygen sensors do not provide a feedback loop to the ecu and therefore runs a rich map. It does this to stay within a safe tolerance to not cause any type of damage. Typically, you see an Air to Fuel Ratio of around 10~14AFR during this cold start. The actual fuel [compared to air] that gets dispensed into the engine depends on many factors such as your Revolutions per Minute, your coolant temperature, your throttle position, your pressure, your altitude, your intake air temperature, your miles per hour, your oil pressure...and so on.
This is what I've meant as "guessing". No matter how well a car manufacturer may try to tune a car to run a certain way under open-loop, the truth of the matter is that there is no real way to know the output and THEREFORE they run a bit richer to prevent pinging/knocking/detonation...
As you can see, a slightly richer mixture will yield more power and less efficiency. Once you pass about 12.6 AFR there are no more gains. Here is where I disagree with you, it cannot be a psychological effect since all the evidence is stated and presented.
Granted, cold start operation is getting much better, there is still regardless no way to know the condition of how the engine is running while in open loop.
This is part of a system called Controls. This type of control does not work well during high/heavy throttle and therefore not used. (Hence open-loop during heavy throttle)
Once in closed loop, the oxygen sensors provide feedback to the ecu with regards to its position to stoichiometry (14.7 AFR) and adjusts accordingly. This is where great efficiency can be achieved.
Given all this information above, that is why I ALWAYS let my car warm up for at least 30 seconds before I drive off. And after I do I keep the throttle light until 60% of normal running temperature.
On a side note, press fits/shrink fits work because of expansion rates. These rates depend on the properties of a material, such as: density, coefficients of thermal expansion, modulus of elasticity, modulus of rigidity, and Poisson's ratio.
So when you first cold start a car, the engine is in open loop mode. While in open loop mode, the oxygen sensors do not provide a feedback loop to the ecu and therefore runs a rich map. It does this to stay within a safe tolerance to not cause any type of damage. Typically, you see an Air to Fuel Ratio of around 10~14AFR during this cold start. The actual fuel [compared to air] that gets dispensed into the engine depends on many factors such as your Revolutions per Minute, your coolant temperature, your throttle position, your pressure, your altitude, your intake air temperature, your miles per hour, your oil pressure...and so on.
This is what I've meant as "guessing". No matter how well a car manufacturer may try to tune a car to run a certain way under open-loop, the truth of the matter is that there is no real way to know the output and THEREFORE they run a bit richer to prevent pinging/knocking/detonation...
As you can see, a slightly richer mixture will yield more power and less efficiency. Once you pass about 12.6 AFR there are no more gains. Here is where I disagree with you, it cannot be a psychological effect since all the evidence is stated and presented.
Granted, cold start operation is getting much better, there is still regardless no way to know the condition of how the engine is running while in open loop.
This is part of a system called Controls. This type of control does not work well during high/heavy throttle and therefore not used. (Hence open-loop during heavy throttle)
Once in closed loop, the oxygen sensors provide feedback to the ecu with regards to its position to stoichiometry (14.7 AFR) and adjusts accordingly. This is where great efficiency can be achieved.
Given all this information above, that is why I ALWAYS let my car warm up for at least 30 seconds before I drive off. And after I do I keep the throttle light until 60% of normal running temperature.
On a side note, press fits/shrink fits work because of expansion rates. These rates depend on the properties of a material, such as: density, coefficients of thermal expansion, modulus of elasticity, modulus of rigidity, and Poisson's ratio.
So, are you trying to tell me there is a power difference between open loop full throttle when cold versus open loop full throttle when warm? The point you are trying to argue, it seems, is that why a car feels faster when you first get into it when cold is because it is in open loop mode, correct? Well, it is also in open loop mode anytime you floor it, so, by your reasoning, there should not be any difference due to the car being cold.
Psychological, yes, most definitely. Its the same old claim of "I changed to brand X oil and I can really feel a difference." when sure, there are dyno tests to prove a 2-4 hp difference in power... NO ONE can feel that much difference in power, therefore it is completely psychological... I would venture a guess that at minimum a 10-15 hp difference (on a low powered 150-200 hp car) would be required to truly feel the difference, and on higher powered cars, in the 400 and up range, at least 25-30 hp difference to actually "feel it." I have been in over 100 quite fast cars and watched them (or even been the "driver") when doing their dyno runs. I've seen mods that people swore made 15+ hp actually LOSE hp on the dyno. I've seen dyno runs made back to back with over 5% differences run to run, with no changes in between, aside from heat. One of the great examples was my buddies T/A... made 345 hp with full exhaust amongst a few other goodies... he swore it was faster with the cutout open, so, he'd remove it every time he went racing... he left it on one time and actually beat a friend, so, he went to the dyno to check the difference... 330 hp with the cutout open... Borla knows what they are doing on that particular car with his particular mods, for sure...
I also think that you don't understand that the ONLY time a car runs in closed loop mode is when you are putting around town under partial throttle. Any other time (full or heavy throttle), the car is "guessing" and gives not one ounce of care as to the O2 sensors, because they are simply not accurate at anything other than 14.7:1 - they are only there for fuel economy and emissions...
Seriously man, you are on the right track, but go get some time logging data on an AEM standalone, then tune one. Then play around with open / closed loop, then add in a wideband and tune using it... It is actually possible with a wideband to run closed loop all the time - the AEM supports this and its just a matter of letting it do the tuning for you.
Unfortunately, its not all about what AFR makes the most power though... we tried to tune for 11.5:1 or 11:1 with street gas (91 octane), yet when running high octane race fuel, we tuned for 12.5:1 Then, once we had the AFR tuned where we wanted it, we adjusted timing to compensate and prevent detonation... Why such a lower AFR on street gas? Simple - to add a cooling effect to the cylinder thus making detonation less likely. When running race fuel, this cooling effect was not necessary, as the fuel itself was much more detonation resistant.
When my good friend first purchased an EVO, years ago, we put a wideband on it with zero other mods. It ran somewhere between 10.5:1 and 11:1 from the factory. This was done to prevent detonation when running the stock boost even.
Back to the original argument at hand, a factory car will run faster when everything is cold, not because it in open loop mode, but because everything is going for it - tighter tolerances, cooler air, cooler coolant temps, etc. It will not be enough to make a noticeable difference, its all in your head. It will be in open loop mode whilst doing this, but it would also be in open loop mode while running full throttle down the freeway, so the only difference is that it is cold vs. hot.
01-20-11, 08:50 PM
#20
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So, are you trying to tell me there is a power difference between open loop full throttle when cold versus open loop full throttle when warm? The point you are trying to argue, it seems, is that why a car feels faster when you first get into it when cold is because it is in open loop mode, correct? Well, it is also in open loop mode anytime you floor it, so, by your reasoning, there should not be any difference due to the car being cold.
Psychological, yes, most definitely. Its the same old claim of "I changed to brand X oil and I can really feel a difference." when sure, there are dyno tests to prove a 2-4 hp difference in power... NO ONE can feel that much difference in power, therefore it is completely psychological... I would venture a guess that at minimum a 10-15 hp difference (on a low powered 150-200 hp car) would be required to truly feel the difference, and on higher powered cars, in the 400 and up range, at least 25-30 hp difference to actually "feel it." I have been in over 100 quite fast cars and watched them (or even been the "driver") when doing their dyno runs. I've seen mods that people swore made 15+ hp actually LOSE hp on the dyno. I've seen dyno runs made back to back with over 5% differences run to run, with no changes in between, aside from heat. One of the great examples was my buddies T/A... made 345 hp with full exhaust amongst a few other goodies... he swore it was faster with the cutout open, so, he'd remove it every time he went racing... he left it on one time and actually beat a friend, so, he went to the dyno to check the difference... 330 hp with the cutout open... Borla knows what they are doing on that particular car with his particular mods, for sure...
Once again, I am not speaking peak horsepower at X_maximum rpm at 100% throttle.
I also think that you don't understand that the ONLY time a car runs in closed loop mode is when you are putting around town under partial throttle. Any other time (full or heavy throttle), the car is "guessing" and gives not one ounce of care as to the O2 sensors, because they are simply not accurate at anything other than 14.7:1 - they are only there for fuel economy and emissions...
Seriously man, you are on the right track, but go get some time logging data on an AEM standalone, then tune one. Then play around with open / closed loop, then add in a wideband and tune using it... It is actually possible with a wideband to run closed loop all the time - the AEM supports this and its just a matter of letting it do the tuning for you.
Unfortunately, its not all about what AFR makes the most power though... we tried to tune for 11.5:1 or 11:1 with street gas (91 octane), yet when running high octane race fuel, we tuned for 12.5:1 Then, once we had the AFR tuned where we wanted it, we adjusted timing to compensate and prevent detonation... Why such a lower AFR on street gas? Simple - to add a cooling effect to the cylinder thus making detonation less likely. When running race fuel, this cooling effect was not necessary, as the fuel itself was much more detonation resistant.
But once again, I thought we were talking about factory cars running on 87 89 or 91 octane.
When my good friend first purchased an EVO, years ago, we put a wideband on it with zero other mods. It ran somewhere between 10.5:1 and 11:1 from the factory. This was done to prevent detonation when running the stock boost even.
Back to the original argument at hand, a factory car will run faster when everything is cold, not because it in open loop mode, but because everything is going for it - tighter tolerances, cooler air, cooler coolant temps, etc. It will not be enough to make a noticeable difference, its all in your head. It will be in open loop mode whilst doing this, but it would also be in open loop mode while running full throttle down the freeway, so the only difference is that it is cold vs. hot.
==> Do you see where you are sounding confusing?
For the final time, I am not arguing full throttle. I am arguing partial throttle. As in, NORMAL driving. We don't all floor it at every stop sign when we get up in the morning and drive to work.
01-20-11, 10:39 PM
#21
"a factory car will run faster when everything is cold".....[but]....."It will not be enough to make a noticeable difference, its all in your head."
==> Do you see where you are sounding confusing?
For the final time, I am not arguing full throttle. I am arguing partial throttle. As in, NORMAL driving. We don't all floor it at every stop sign when we get up in the morning and drive to work.
partial throttle is always a hard sell - if you want to go faster, give it more throttle...
your argument reminds me of a gimmick back in the late 90's that promised 15% more power... it gave you 15% more power across most of the throttle band, but not a single more hp at full throttle... it made a car feel peppier, when all you had to do to start was give it more throttle...
comparing partial throttle is a retarded thing to do and I would never ever do it, as, well, its useless, as, if you want more power, you give more throttle...
I think you are arguing just to argue...
01-21-11, 01:51 AM
#22
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On the contrary, you keep assuming I'm talking about some kind of racing and you keep giving examples accordingly. So what about conservative driving and arguments with reference to engine warm up for the casual driver.
I get really annoyed when people don't take the time to understand what someone is writing and infer something else. That's what most of those other posts were about...some sort of misunderstanding and then it gets a bit off topic.
Even up till your latest post, you're putting meaning into things I haven't said. So if you want to continue a conversation, I'll be more than happy to continue through PM. Otherwise, I hope the OP could get some insightful information through all this.
I get really annoyed when people don't take the time to understand what someone is writing and infer something else. That's what most of those other posts were about...some sort of misunderstanding and then it gets a bit off topic.
Even up till your latest post, you're putting meaning into things I haven't said. So if you want to continue a conversation, I'll be more than happy to continue through PM. Otherwise, I hope the OP could get some insightful information through all this.
01-21-11, 03:18 AM
#23
the whole thing about more power started when I said "all of this being said, you want the most power out of most engines, you want to literally start the car, let oil pressure come up, and then full throttle right away - because of the tighter tolerances cold and air temperatures as well, you will get more power from the engine..."
then you claimed I was wrong and it was not because of the tolerances, but instead because of open loop mode vs. closed loop.
WHY IN THE WORLD WOULD SOMEONE CARE ABOUT HOW MUCH POWER A CAR MAKES AT PARTIAL THROTTLE? in my statement, I even said full throttle... never a single mention about partial throttle!
You are arguing for the sake of arguing - something that you understand a small amount about, but don't completely grasp the entire concept most likely because you have read about it, but never actually done anything in depth with it.
I am sorry this may sound like an attack or an attempt to degrade you, it isn't. But, your attempt to prove me wrong was based on something you misread or just didn't know about... I have years of experience of doing these things, and even though I'm a beach bum right now, I still get lots of practice - built a custom ECU for an old blazer, just built a 375 hp 10.4 liter diesel engine for our boat from the ground up...
01-22-11, 12:40 AM
#27
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This is something you will have to eventually decide for yourself. Here is a link that might help you make a decision. I don't let my car idle very long at all. Unless it is really cold and the car was parked outside covered with snow/ice.
http://finance.yahoo.com/insurance/a...s-and-Mistakes
"Myth: Wait, it's still warming up
Some people insist that your car will last longer if you let it idle until the engine reaches normal operating temperature.
It's true that running cold is harder on an engine than running warm. The oil is thicker, and it takes a little time - very little, really - for it to flow to all the parts of the engine that need it.
But letting the car sit while the engine is running doesn't help anything. It just wastes gas and pumps out needless fumes. You might as well get on your way.
All you need to do is drive your car gently until the engine is warmed up. No smoky burn-outs first thing in the morning. Just go easy and keep those engine RPMs down until everything's toasty, and you'll be just fine.
Five to ten minutes of easy driving is about all it takes before most cars are ready to rev, says Sinclair.
Driving gently for a few minutes helps your brakes, too, says Sinclair. They also need a chance to warm up.
"Brakes go to from zero to 200 degrees or so in an instant with a hard stop," he says.
That kind of sudden temperature change promotes warping of brake rotors, he says. Better to make a few slow stops at first so the brakes can heat up gradually."
http://finance.yahoo.com/insurance/a...s-and-Mistakes
"Myth: Wait, it's still warming up
Some people insist that your car will last longer if you let it idle until the engine reaches normal operating temperature.
It's true that running cold is harder on an engine than running warm. The oil is thicker, and it takes a little time - very little, really - for it to flow to all the parts of the engine that need it.
But letting the car sit while the engine is running doesn't help anything. It just wastes gas and pumps out needless fumes. You might as well get on your way.
All you need to do is drive your car gently until the engine is warmed up. No smoky burn-outs first thing in the morning. Just go easy and keep those engine RPMs down until everything's toasty, and you'll be just fine.
Five to ten minutes of easy driving is about all it takes before most cars are ready to rev, says Sinclair.
Driving gently for a few minutes helps your brakes, too, says Sinclair. They also need a chance to warm up.
"Brakes go to from zero to 200 degrees or so in an instant with a hard stop," he says.
That kind of sudden temperature change promotes warping of brake rotors, he says. Better to make a few slow stops at first so the brakes can heat up gradually."
01-24-11, 06:03 PM
#28
Yes in 32 degree weather and especially in zero degree weather if you want your engine and it's associated parts (e.g. manifolds) gaskets and seals to last a long time. You should idle the engine a few minutes then drive gently for 3-4 miles. Above about 40 degrees no idling is necessary, but you should still drive gently for 3-4 miles. Even in the summer.
In the 1960's and 70's all Toyota and Datsun owners manuals recommended idling a few minutes because the engineers know it's better for the car. Some of these manuals even recommended idling until the coolant temp reached 120 degrees. Engines have not changed since then so this advice still holds. The only thing that has changes is the emission systems and for minimum emissions, the engine should NOT be idled. So car makers nowadays don't recommend idling for eco-dogooder public relations reasons; i.e. minimum emission and fuel consumption reasons.
In the 1960's and 70's all Toyota and Datsun owners manuals recommended idling a few minutes because the engineers know it's better for the car. Some of these manuals even recommended idling until the coolant temp reached 120 degrees. Engines have not changed since then so this advice still holds. The only thing that has changes is the emission systems and for minimum emissions, the engine should NOT be idled. So car makers nowadays don't recommend idling for eco-dogooder public relations reasons; i.e. minimum emission and fuel consumption reasons.
01-24-11, 07:01 PM
#29
Yes in 32 degree weather and especially in zero degree weather if you want your engine and it's associated parts (e.g. manifolds) gaskets and seals to last a long time. You should idle the engine a few minutes then drive gently for 3-4 miles. Above about 40 degrees no idling is necessary, but you should still drive gently for 3-4 miles. Even in the summer.
In the 1960's and 70's all Toyota and Datsun owners manuals recommended idling a few minutes because the engineers know it's better for the car. Some of these manuals even recommended idling until the coolant temp reached 120 degrees. Engines have not changed since then so this advice still holds. The only thing that has changes is the emission systems and for minimum emissions, the engine should NOT be idled. So car makers nowadays don't recommend idling for eco-dogooder public relations reasons; i.e. minimum emission and fuel consumption reasons.
In the 1960's and 70's all Toyota and Datsun owners manuals recommended idling a few minutes because the engineers know it's better for the car. Some of these manuals even recommended idling until the coolant temp reached 120 degrees. Engines have not changed since then so this advice still holds. The only thing that has changes is the emission systems and for minimum emissions, the engine should NOT be idled. So car makers nowadays don't recommend idling for eco-dogooder public relations reasons; i.e. minimum emission and fuel consumption reasons.
what makes you think so?
are you sure the engineers didn't learn something within the past 50 years that made them change their minds that way?
I would also like to thoroughly disagree that "engines have not changed." In the past 50 years, we have gone from carbureted to throttle body injected to injectors in the intake runners and now we are using direct injection. Not only that, we are using a lot more plastics, a lot less metal, and many of the metals we are using are alloyed better for their purposes... We've also went from pushrods to overhead cams, and from points and condensers to distrubutors with coil packs, to one coil per cylinder, and, in some vehicles, one coil per cylinder with two spark plugs per cylinder. Not to mention everything is manufactured to much better tolerances anymore. Engineers have also done a fine job of fixing faults over the years, improving their designs as they went, so, I figure they have taken cold start operation into account...
01-24-11, 07:33 PM
#30
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Im pretty sure an engine starts out "loose " at cold temp and when it warms up things expand more than the block and the tolerances tighten up. You ran your drag car cold due to temps, not tolerances.
