breathe engine or increase drag???

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imported_04yfz

New member
Hey all...I've been reading some of the posts in Autopia and I must say they have been very insightful...This is my first post and as such I might putting it in the wrong forum...



When driving 60+ mph I sometimes open the cabin vents and tilt the sunroof., a lot of air starts flowing out of the vents, vacuum type of effect On a hot day, will this help cool the engine while driving at light speed, or will this increase the cars drag???... Should I be concerned with engine heat on my car, it's a 2k2 Maxima? I've noticed the radiator fan trips on rather frequently and there's a lot of hot air eminating from the front and side front of the car???....:confused:



Thanks for any input or insight....:xyxthumbs
 
First of all, nice car :xyxthumbs Mine's a '92 and I can tell you it has great temperature control. I wouldn't worry about the car being able to cool itself, and the hot air flowing out around the front is just the radiator fans doing their job.



I'm not quite sure what you mean about cooling the engine vs. drag in your first question. If you're wondering if the air flowing through the vents will cool the engine, it won't because the air doesn't come from under the hood but rather from the base of the windshield. Or if you're wondering if you should use the sunroof vs. using air conditioning instead, I think it just depends what you want, because tilting the sunroof and running the AC both cause drag (just in different ways). I'd be inclined to think the AC would create just a bit more drag though.



Have you been to http://www.maxima.org ? Not quite as ummm.... "orderly" there, heh heh :D but lots of info and help if you know how to get it.
 
Opening the sunroof or windows will have no effect on engine temperature.



Opening the sunroof or windows will increase the cars drag.



Does your car have a over heating problem?
 
some places recommned runiing the heater on an open vent for a few minutes to help lower engine heat, but I don't know, seems like the effect would be minimal.



opening windows/sunroof will increase drag - better to use AC then open windows on the highway to save gas.



I don't think the AC will increase drag. it will lower engine power to the wheel and reduce performance, so it may just feel like that
 
Thanks for the responses guys...



I've tried http:\\maxima.org, but there is very little info on the 2k2 model. I've read most of the info & articles that they have there since the a lot of info for the 2k models.



My car doesn't have an over heating problem, just want to pamper the engine here and there since I drive it so hard (70+ on a daily basis).



I was under the impression that running the A/C reduces perfomance and fuel economy???...



I completely forgot about the air ducts that sit below the wipers and here's where the air come in from....
 
Running the heater on high to help prevent overheating is a simple principle. The coolant normally runs thru the engine, and back to the radiator where it is cooled. By running the heater, you in effect add a second radiator, all be it a small one. With the heater on, some of the coolant takes a detour thru the heater core. The fan blows air over the heater core, removing some of the heat from the coolant, and thereby cooling the engine more than the radiator alone.



It shurdo get mighty hoooottttt inside though :nixweiss
 
NizanDrvn said:


I was under the impression that running the A/C reduces perfomance and fuel economy???...
Click to expand...



Anything that you run while your car is going takes power form the engine and therefore burns more gas since the engine needs to work hards to maintain the same speed.



70+ miles a day is a lot, but not bad if it's highway miles vs. city traffic or frequent cold/warm starts
 
If you want to pamper the engine then drive like an old lady and go slow with no sudden starts and stops.



I would not worry too much about driving with the AC on or other ancillary equipment.
 
all of our cars run cooler with the A/C ON, this is because the Condenser fans turn on to keep the A/C cold inside, and these fans also cool off the engine at the same time. The condenser is usually right infront of the radiator. Driving like an old lady might save your transmission(unless it is a chrysler, then nothing will save your transmission), but it will lead to more carbon build up(from what i have heard) in the motor.
 
In a nutshell, what you are experiencing is normal. Both items do a very good job in cooling the car (especially since mine sees the other side of 70 every day). At 70 mph, the VQ35DE is only running at 2500 rpm which is not hard on the motor at all. Hard is considered consistently running it at over 5000 rpm to redline. Opening the windows and sunroof will not speed engine cooling but will add considerable drag.



The key thing that you should be concerned with is following the maintenance schedule very closely. How many miles do you have on your Max?
 
My pride and joy only has 5600 miles on it....



I do 70+ mph for 40 miles a day....



My nissan master tech told me to drive the car hard, make the engine hit 4000 to 5000 rpm from time to time to avoid carbon build up....He test drove it with me because I was freaking out over the radiator fans tripping on resulting in a mild vibration through the steering column...
 
If you are doing 70mph for 40 miles a day, you would be getting the engine hot enough to clean the engine. Every now and then running at 5000rpm will not do any harm, as long as everthing is fully warmed up. Modern engines are very tough, keep the oil clean and let everthing warm up before driving hard, and you wont have any problems.



Every few months I will drive on the motorway in 3rd gear at about 5000 rpm for a mile or two to clean everthing out, but I do this as my new job requires only a few miles of city centre driving to get to work.



Steven
 
Sounds like this thread has gone through its paces... but I figured I'd get my 2cents in too. WARNING: this is long, read at your own risk...



Don't worry about the car overheating... Nissan has gone to great lengths to test this car in conditions much worse that you will ever likely be driving in (unless you live in/near the Nevada or Arizona deserts). The fans are coming on to do their job. You are probably noticing this on hot days in stop and go traffic or sitting still. I doubt you can hear them coming on at 70mph. If you notice something not seeming right, just mention it to your dealer and take the car in to be evaluated for normal operation. It's a good idea to do this so there is a record of your concern if it ever develops into a real problem.



As for drag... (BTW I was an aerodynamicist for latest huge military fighter program, Lockheed Martin's JSF X-35) yes, opening the windows will add drag, but nothing of concern other than getting the interior dirtier faster. Just cracking the sunroof will NOT add noticeable drag. The reason it makes the vents flow 'faster' is exactly like you mentioned. A vacuum effect. The sunroof is on the top of the car where there is a great deal of low pressure relative to the vent inlet at the base of the windshield. Like water, air will flow from high to low. The A/C will not add drag. It will draw power off of the engine to run the compressor. Both opening the windows and running the A/C will decrease fuel economy and not cause additional engine wear. In essence, do whatever is most comfortable to you. I’m sure you’ll get tired of the car before you’ll ever be able to wear it out if you follow the maintenance schedules (driving hard or easy). Anyone still reading??? Just checking. :D
 
Thanks Hans....



The reason for original post was that I'm am interested in aerodynamics and cars, hence a big fan of F-1, CART and touring racers...



Know any goo places for some casual reading???...
 
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