Cutting back on radiator drag

[basjoos]

One characteristic of hypermiling is that you aren't asking your engine to produce large amounts of power. This being the case, my engine isn't putting out large amounts of heat and I shouldn't require the total area of my radiator, which would be sized for a worst case situation, to keep my engine cooled. Since the radiator is responsible for 5% to 9% of the car's total drag, I wanted to see how much of my car's radiator air intake I could block off without causing the cooling water's temps to increase under my normal driving conditions. Cutting down on the air flow through the grill would have two beneficial effects on reducing drag. It reduces the drag caused by the air flow through the radiator and engine compartment, and it reduces the turbulance under the car where the radiator air is exhausted. I currently have the grill blocked down to a 4" X 1" opening in the upper center of the grill, and the cooling gauge hasn't budged, even during a 35MPH, 800 foot climb in third gear up the mountain into North Carolina and while sitting in traffic. I'll continue to closely monitor the cooling temp as we move into summer to see if I'll need to open up the grill more as the outside temperatures rise. The result of this modification on my car, combined with some some other minor drag reduction mods and changes in driving style, has caused my MPG to rise from the usual low 50's I normally get at this time of year into the upper 60's (last tank was 69MPG). It'll be interesting to see where the mileage will go as we ease into summer.

On another subject, I haven't been able to log into the www.cleanMPG website, even though it says I am registered as a member. When I try to login, it says "Thank you for logging in" and then sends me back to a login page. On the home page there is a line that reads "If you have any problems with the registration process or your account login, please contact contact support", but clicking on this line takes me to another page where they ask me to login.

[krousdb]

I have had my radiator blocked entirely since January and have seen no ill effects. I expect to keep it blocked into the summer to see if there are any problems.

Congrats on the awesome tank! I'm jealous.

Also, I will relay your message to the cleanmpg admins. We will get you fixed up.

[krousdb]

Basjoos,
Here is what I got from tom at cleanmpg....


ask him if he is going to cleanmpg.com or www.cleanmpg.com

I've heard using cleanmpg.com doesn't work and you need to use www.cleanmpg.com Also, you will need javascript and cookies enabled I believe.

Hope that helps!

[SVOboy]

I have that problem with college websites, pain in the ***. Good thing they all have rejected me so I don't need to worry about it.

[Matt Timion]

It would be nice if someone could test the before and after MPG data of radiator blocking.

Is anyone up for the challenge?

I'm actually thinking of switching to a smaller radiator so that I can have a slightly warmer engine and block of the unused area.

[MetroMPG]

Originally Posted by Matt Timion

It would be nice if someone could test the before and after MPG data of radiator blocking.

do you mean radiator blocking or grille blocking?

i tested grille blocking on my car last fall, and it netted a 2.9% avg FE improvement.

http://www.metrompg.com/posts/grille-blocking-part-2.htm

[zpiloto]

I had the same results as MetroMPG with grille bocking. I contribute this to the higher engine temps and not areo benifits.

[MetroMPG]

grille blocking benefits are probably a combination of both aero and higher engine/transaxle temps.

when testing last fall, FE increased *immediately* after installing the block on my car, which i would not expect to see if it were strictly a result of temperature (since temps don't increase immediately, and take some time to stabilize at a new higher level).

of course if all your driving is low-speed, then the only benefits you'll see are temp-related.

cooling system drag accounts for a significant amount of a vehicle's total drag. i've seen figures as high as 33% of total drag for a turbocharged volvo (with multiple radiators/intercoolers), but it's normally lower on regular cars - 5% to 9% as basjoos quoted in the first post in the thread.

[philmcneal]

if you engine kill a lot then you don't have to worry about engine over heating right? But wouldn't that prevent the cooling system from circulating in the engine? How about that Oil?

basjoos and krousdb can you post pics of your block? I wonder if it distracts from the car's image?

[basjoos]

Since engine idle-stop is SOP with hybrid cars and many of them have gone well over 100,000 miles with no engine problems, there must not be any adverse cooling or lubrication problems associated with stopping the engine for short periods of time. I have 200,000 miles on my current engine with no oil consumption problems.

I currently have clear tape over the openings in the grill, so you have to really close close to see that anything is different.

krousdb, I have been going to the www.cleanmpg.com site and haven't had any problems with accessing other boards. I'll keep working on the problem and see what I can work out.

[basjoos]

Sorry about the repeat portings, I am having some slow connection problems with my dial-up service this evening and thought the posting hadn't gone through.

[Matt Timion]

Originally Posted by basjoos

Sorry about the repeat portings, I am having some slow connection problems with my dial-up service this evening and thought the posting hadn't gone through.

I think it's not just you. THe server is slowly getting more sluggish. I'm officially taking my quest to find a better server seriously starting tomorrow.

[krousdb]

Originally Posted by basjoos

krousdb, I have been going to the www.cleanmpg.com site and haven't had any problems with accessing other boards. I'll keep working on the problem and see what I can work out.

Basjoos, are you still having problems accessing cleanMPG?

[krousdb]

Originally Posted by philmcneal

if you engine kill a lot then you don't have to worry about engine over heating right? But wouldn't that prevent the cooling system from circulating in the engine? How about that Oil?

basjoos and krousdb can you post pics of your block? I wonder if it distracts from the car's image?

My Prius has had a bazillion starts and stops. At 63K miles, it has never been back to the dealership since the day it left. I do my own oil changes. No problems so far.

YOu can see my grille block in one of the pics in the Airspeed Indicator thread. Currently, it is made from a spare roof shingle. Soon it will be made from coroplast.

[basjoos]

I still can't log on. My username and password are apparently registered on the board, because if I enter a different username and/or password or use a different combination of lower/upper case letters, it gives me a "invalid username or password" page. When I use the correct usename and password, I first get a "Thank you for logging in" page, then it goes to the "You are not logged in or you do not have permission to access this page" page. Maybe my account never got activated? E-mails have been known to vanish in the aether.

[MetroMPG]

Originally Posted by philmcneal

if you engine kill a lot then you don't have to worry about engine over heating right?

i have noticed that doing more engine-off coasting has resulted in my cooling fan coming on more frequently. but i think this has less to do with the grille block, and more to do with shutting off the engine after a high-load event:

if i go a couple of blocks between 2 stops, i'll accelerate approximately halfway, then kill the engine and coast to the next stop. in other words, the engine is killed just after a relatively high load (and i mean relatively - accelerating at a gentle pace), when it's generating more heat.

that heat isn't immediately dissipated because the water pump stops pumping when the engine stops (unlike the prius, which has an electric pump, and which may continue pumping after the motor is shut off).

what this means is FAS *may* subject a normal motor to higher temperature peaks and hot soaks than normal driving. also, since the stationary coolant in the radiator cools more rapidly with the engine off while coasting, the engine is subjected to wider coolant temperature fluctuations when restarted than an engine driven constantly.

it reminds me of a bit of advice a knowledgeable old timer gave me once, which is you shouldn't shut an engine off immediately after exiting the highway (high load) because the cooling system won't have had the chance to dissipate the built up heat.

whether it stresses engine components (head, head gasket?) to the point of affecting longevity, i can't answer.

something to think about.

[krousdb]

Originally Posted by basjoos

I still can't log on. My username and password are apparently registered on the board, because if I enter a different username and/or password or use a different combination of lower/upper case letters, it gives me a "invalid username or password" page. When I use the correct usename and password, I first get a "Thank you for logging in" page, then it goes to the "You are not logged in or you do not have permission to access this page" page. Maybe my account never got activated? E-mails have been known to vanish in the aether.

I sent Tom another message. I will get back to you with what he says.

[krousdb]

Originally Posted by krousdb

I sent Tom another message. I will get back to you with what he says.

Basjoos,
Please check your private messages. I will send you something.