How warm before VTEC okay?
#11
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Originally Posted by xviper,Jun 6 2005, 03:07 PM
It doesn't have to be. Honda has made sure you don't hurt the engine by putting in that cold temp limiter. Honda has done the thinking for you.
I'm beginning to sound like a broken record but I'll say it again ..................
If the ECU will let you VTEC, then you CAN VTEC. This occurs when the coolant temp is at about 140 degrees (or 3 bars on the temp gauge for pre-'04 cars).
You don't have to warm it up a little longer to be safe. THE OIL TEMP DOES NOT HAVE TO BE AT 140 DEGREES. Honda has determined that when the coolant temp is at 140 degrees, the corresponding oil temp (whatever that may be - and it DOESN'T matter whether or not you know what that number is) will put the oil viscosity and flow characteristics in a place where it will function in the desired task asked of it.
Those of you who like to wait a bit longer to "warm" up the oil some more, go ahead if it'll help you sleep at night, BUT YOU DON'T HAVE TO. Why second guess the people who designed and built this car? If Honda didn't think it was safe to VTEC when the coolant temp is at 140, don't you think they would have put the limiter to something higher? They can do that, you know. They have the technology.
BTW, if you use a non-recommended oil viscosity, all bets are off.
I'm beginning to sound like a broken record but I'll say it again ..................
If the ECU will let you VTEC, then you CAN VTEC. This occurs when the coolant temp is at about 140 degrees (or 3 bars on the temp gauge for pre-'04 cars).
You don't have to warm it up a little longer to be safe. THE OIL TEMP DOES NOT HAVE TO BE AT 140 DEGREES. Honda has determined that when the coolant temp is at 140 degrees, the corresponding oil temp (whatever that may be - and it DOESN'T matter whether or not you know what that number is) will put the oil viscosity and flow characteristics in a place where it will function in the desired task asked of it.
Those of you who like to wait a bit longer to "warm" up the oil some more, go ahead if it'll help you sleep at night, BUT YOU DON'T HAVE TO. Why second guess the people who designed and built this car? If Honda didn't think it was safe to VTEC when the coolant temp is at 140, don't you think they would have put the limiter to something higher? They can do that, you know. They have the technology.
BTW, if you use a non-recommended oil viscosity, all bets are off.
#12
Originally Posted by mxt_77,Jun 6 2005, 10:58 AM
Question: Does our car have an oil temp sensor in it, or just coolant? If we don't have an oil temp sensor in our car, then I would disagree with your statement. Sure, Honda may have determined that the risk of damage to the engine is low enough that they can rely on the coolant temperature to determine when to disable the cold rev-limiter... but that doesn't necessarily mean that it's "safe" to rev just because the ECU will let you.
I believe that Honda was just too cheap to put in an oil temp sensor and make use of it to determine when to disable the cold rev-limiter, figuring that it wouldn't be used frequently enough to make it worthwhile. But, that doesn't necessarily mean that they did any calculations to determine that the oil will be up to operating temp at the same time that the coolant is at 140 degrees.
Just because the ECU lets you do something doesn't mean that you should do it.
I believe that Honda was just too cheap to put in an oil temp sensor and make use of it to determine when to disable the cold rev-limiter, figuring that it wouldn't be used frequently enough to make it worthwhile. But, that doesn't necessarily mean that they did any calculations to determine that the oil will be up to operating temp at the same time that the coolant is at 140 degrees.
Just because the ECU lets you do something doesn't mean that you should do it.
If Honda went to the trouble of putting in a cold rev limiter, why did they decide on 140 degrees of coolant if they didn't think the corresponding oil temp was adequate? Why not set the limit for when the coolant temp is 160 degrees? 170 degrees? It would have been simple enough.
Worst case scenario: Let's say that oil temp lagged behind quite a bit (and I doubt it lags more than 20 degrees behind) and at 140* coolant temp, the oil temp is only 100*. That's just over body temp. I think oil of the recommended viscosity for this car at body temp will flow and protect quite well. But nevermind. Forget about my "goofy" logic as depicted in this paragraph. Just consider the logic of my first two paragraphs.
As for the tranny and diff fluid, assuming you're not just sitting there idling, these too, will increase in temp. I can tell you that in a warmish day, the diff temp will climb about 10*C in the first 10 to 15 minutes. Since the diff fluid is not pumped and the tranny fluid is pumped at very low pressure, these don't have to be very warm to work properly.
ps. I've never had to think so much and type so much over something that is so trivial and uncomplicated.
#13
Originally Posted by RazorV3,Jun 6 2005, 12:49 PM
you have to factor in the condition of the whole drivetrain as well (from the transmission to the diff and everything in between).
BTW, IMO, transmissions and rear diffs, by virtue of the fact that oil is either not pumped or pumped at very low pressures, they can operate quite comfortable at temperatures extremes both cold and hot. Really, all you need is for the "bathed" parts to grab onto the fluid and move it around for the fluid to begin lubricating and protecting. Crankcase oil has a temperature limiting factor by virtue of some of the immense pressures attained during highly viscous pumping. As high as 95 to 100 psi on cold start on a -25*C day. This pressure comes down fairly quickly after about 10 minutes running - about the same time that we get 3 bars.
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