Plastic cover underneath the engine fell off

[MikeHTally]

well, if your brick of a truck is fine, then the speed3 should be honkie-dorie.

And it is, the fans don't run on the highway. They windmill, just like the e-fan on the truck.

 

[njaremka]

Think about that a minute. Preventing the evacuation of air while it's pouring in through the grill at 1,000's of cfm will raise the pressure, not lower it.

somwhere, bernoulli is spinning in his grave....

as the air passes past the "splash guard," it sucks air out of the engine bay, HELPING to create a lower pressure zone in the engine bay. removing that panel allows the air to circulate up right behind the raditor allowing the pressure behind the radiator to equalize with the air in front effectively STOPPING the airflow through the radiator.

And it is, the fans don't run on the highway. They windmill, just like the e-fan on the truck.

you know this for a fact? have you sat in your engine bay while cruising down the highway to monitor the fans?

 

[MikeHTally]

somwhere, bernoulli is spinning in his grave....

as the air passes past the "splash guard," it sucks air out of the engine bay, HELPING to create a lower pressure zone in the engine bay. removing that panel allows the air to circulate up right behind the raditor allowing the pressure behind the radiator to equalize with the air in front effectively STOPPING the airflow through the radiator.



you know this for a fact? have you sat in your engine bay while cruising down the highway to monitor the fans?

Jeez, people. This is pretty simple stuff. Manufacturers have for years looked for ways to reduce load on the engine. The mechanical fan takes a LOT of power to turn, so they looked for ways to disconnect it. First, it was the centrifugal clutch on the fan, designed to have the blades turn loose of the water pump at a certain rpm. Then they put thermostats on the fan hub and clutches to accomplish the same purpose. Now it's possible to install a fan that only comes on when needed, further reducing the load on the engine.

No, I don't have to sit in the engine bay to see if the fan is running. I rigged a LED on the dashboard so I can tell when power is going to the fan. It only kicks on in traffic. The 'stat in the Ram opens at 180 degrees. I have the fan controller set to kick on at ~200 degrees. The e-fan on my Ram is capable of 3,300 cfm. The air through the radiator is WAY more than that, except when I'm in traffic. Ask your favorite knowledgeable auto tech if the fan runs when you're on the highway.

As for Bernoulli, I suggest you go look at the belly pan and see which way the air will move when it encounters the NACA ducts.

 

[njaremka]

Jeez, people. This is pretty simple stuff. Manufacturers have for years looked for ways to reduce load on the engine. The mechanical fan takes a LOT of power to turn, so they looked for ways to disconnect it. First, it was the centrifugal clutch on the fan, designed to have the blades turn loose of the water pump at a certain rpm. Then they put thermostats on the fan hub and clutches to accomplish the same purpose. Now it's possible to install a fan that only comes on when needed, further reducing the load on the engine.

No, I don't have to sit in the engine bay to see if the fan is running. I rigged a LED on the dashboard so I can tell when power is going to the fan. It only kicks on in traffic. The 'stat in the Ram opens at 180 degrees. I have the fan controller set to kick on at ~200 degrees. The e-fan on my Ram is capable of 3,300 cfm. The air through the radiator is WAY more than that, except when I'm in traffic. Ask your favorite knowledgeable auto tech if the fan runs when you're on the highway.

As for Bernoulli, I suggest you go look at the belly pan and see which way the air will move when it encounters the NACA ducts.

i'm not going to debate about when the cooling fans operate, since that isnt the thrust of this thread. but i WILL debate the purpose of the "splash pan". those little "NACA" looking scoops will not direct enough air to disrupt the airflow through the radiator. but saying that the only purpose the "splash pan" serves is to prevent water spray or to smooth out air flow under the car is rediculous. it may serve some purpose in smoothing airflow, but its main purpose in life is to help create a low pressure zone behind the raditor.

 

[MikeHTally]

I'd like to see some real facts about the low-pressure zone behind the radiator, since there are so many thousands of cubic feet of air provided by the forward motion of the car. The low-pressure zone could only be produced at speed when it would have only miniscule benefit if any. It would actually produce slightly more drag, which would adversely affect mileage to a tiny degree. With the government regulations on fuel mileage, ANY drag would be a drag.

 

[njaremka]

I'd like to see some real facts about the low-pressure zone behind the radiator, since there are so many thousands of cubic feet of air provided by the forward motion of the car. The low-pressure zone could only be produced at speed when it would have only miniscule benefit if any. It would actually produce slightly more drag, which would adversely affect mileage to a tiny degree. With the government regulations on fuel mileage, ANY drag would be a drag.

oh good gawd....

the movement of the car creates a high pressure zone in front of the radiator - you said that yourself. adding the "splash pan" help create a larger low pressure zone behind the raditor. high in front, low behind creates a pressure differential. air will flow from a high pressure zone to a low pressure zone. thus, air flows THROUGH the radiator. right?

take away the "spalsh pan" and the air will circulate up behind the raditor, causing the pressure behind to be higher than if the "splash pan" were there. if the pressure differential from the front of the radiator to the back of the radiator is less, you will get less airflow. the coo.ing effectiveness of the radiator is related to the airflow across the radiator... thus, less cooling with out the "spalsh pan".

 

[MikeHTally]

Sorry, hoss. It just don't work that way. If it did, splash pans and belly pans would've been around a lot longer. The goal of the pan is to reduce turbulence under the vehicle. In that sense, you're right. The turbulence produces drag. The fact it keeps road grunge out is a nice side benefit. The radiator couldn't care less if there is .1 millibar of reduced pressure behind it with mountains of air in front.

I suspect the purpose of the ducts is to equalize the pressure on the pan, keeping it from trying to act like a wing at 100+. The air through the radiator would very likely try to bow it down

 

[Kain]

innanets.

 

[MikeHTally]

I've been wondering if you were lurking, man. Who is that avatar? You should go back to the Dos Equis character, but include the honeys he's sitting with.

 

[Kain]

Deaf touch.

 

[njaremka]

http://www.arrowheadradiator.com/14...apability_in_high-performance_automobiles.htm

notice what they say under "Cooling Airflow"

 

[njaremka]

a couple more references...

http://www.ipdusa.com/Volvo-940960/Exterior/Belly-Pan/p-136-272-3987/

Volvo also suggests that the pan aids in cooling efficiency by forcing the airflow across the entire engine compartment.

i thought this link had some good comments also...
http://www.audizine.com/forum/showthread.php/285561-Is-the-plastic-shield-under-engine-necessary

the one quote that you might want to notice:

I logged before and after.
All temps went down noticably with pan ON.
There is a reason race cars run them. Air turbulance hurts in many ways. Temps just being one that we'd worry about, since none of us are fast enough on a road track yet to worry about the other effects, lol.

Run without it for all I care. I was going to since my car doesn't get driven in bad stuff. But after logging, no way. It stays on. And it isn't a big deal to take off; I don't see what all the fuss is about for an extra minute or two TOPS. But hey, it ain't my car, so have at it.

i found a bunch more, but it would be just as easy for you to google as it was for me.

 

[MikeHTally]

Well, "Volvo suggests..." is hardly definitive. A post from another forum can be dismissed as it is very likely not in any way scientific. As for the "cooling airflow" item, notice it mentions only the fan shroud and the recirculation shields. "...Increasing airflow by speeding up the fan, by providing an improved fan, by providing or improving the fan shroud, by reducing air restrictions in the grille or engine compartment, or by providing recirculation shields to prevent air from bypassing the core, will all improve heat transfer and cooling."

Obviously we disagree. My position is common sense: if air is roaring through the radiator at any speed above 30 or so, it will overwhelm any "negative pressure" created by a belly pan, if such pressure drop exists, which is doubtful, considering the scoops pulling air into the engine bay by the pan. You mention Bernoulli - his formula talks of static pressure and dynamic pressure. I suspect the dynamic pressure of air through the radiator at 40 mph is WAY more than any pressure drop caused by the pan.

 

[njaremka]

Well, "Volvo suggests..." is hardly definitive. A post from another forum can be dismissed as it is very likely not in any way scientific. As for the "cooling airflow" item, notice it mentions only the fan shroud and the recirculation shields. "...Increasing airflow by speeding up the fan, by providing an improved fan, by providing or improving the fan shroud, by reducing air restrictions in the grille or engine compartment, or by providing recirculation shields to prevent air from bypassing the core, will all improve heat transfer and cooling."

Obviously we disagree. My position is common sense: if air is roaring through the radiator at any speed above 30 or so, it will overwhelm any "negative pressure" created by a belly pan, if such pressure drop exists, which is doubtful, considering the scoops pulling air into the engine bay by the pan. You mention Bernoulli - his formula talks of static pressure and dynamic pressure. I suspect the dynamic pressure of air through the radiator at 40 mph is WAY more than any pressure drop caused by the pan.

i'm not saying that the "splash pan" will cause a pressure drop, but that it will help prevent a pressure rise. anything that can be done behind the radiator to help with the pressure drop across the radiator will aid airflow across the radiator, thus ultimately helping with the cooling efficiency of the radiator. removing that "splash pan" will reduce the pressure drop across the radiator, and ultimately hurt the cooling efficiency of the radiator.

will it be enough to cause the engine to overheat in normal conditions? maybe, maybe not. but remember, the faster you drive, the more heat you are putting into the cooling system, and the more heat you are asking your radiator to shed. without the "splash pan", the "dead zone" behind the radiator will shrink, causing the pressure differential to shrink, causing the flow across the radiator to deminish, which will ultimately limit how much heat your radiator can shed to the flowing air.

 

[ALIEN3T]

I am not saying who is right or Wrong.

BUT back when i drove Ford Escorts, same thing undertray. We took it off 1 time for a week. rock came up and tore up the serpintene belt. But cover back one, NEver ever had an issue like that again.

BUT my MS3 has gone almost 2 years without the undertray on. 1 screws got lost in a shop move. from the shop the built my FMIC kit they are finishing up./ So we have had it off. No heating issues, no belt problems. nothing but the only big problem i have had is the engine bay gets dirtier faster. and the bottom area is dirtier. BUT besides that 2 years of no understay, and no issues.

 

[MSMS3]

My daughter's VW Passat developed a serious oveheating problem. Turns out that her bone-headed husband had done the last oil change at home and concluded that the "splash guard" or under shielding was just getting in the way of his oil change plans for the future, so he removed it and threw it away.

After a trip to the dealer and a cussing out of the husband by the tech and spending about $200 for the new bottom plastic shield, the overheating problem was solved.

So, does this lesson apply to the MS3? I don't know. But I know is sure does on the Passat.

 

[MS3inDC]

whether that story applies or not, there is nothing that keeps air from going under or around the sides of the radiator, even with the spalsh guard in place... so again, don't think it has much to do with cooling for our cars

 

[Speed3Max]

Mines been off for ever.... no over heating... no problems what so ever.

 

[P2K]

I lost a screw on my splash guard on my way to work and I heard it dragging on the ground. I took it off and it's been sitting in storage for almost 3 years. I haven't had an overheating problem or any other issue since I took it off.

 

[ms3brendan]

Join the list for a possible aluminum splash guard! http://www.mazdas247.com/forum/showthread.php?t=123776187&page=2