Why the plastic cover over the bottom of engine?

RCZ · 07-17-2009, 08:16 PM

Modern cars makers try to keep the bottom of their cars as flat as possible to minimize drag and maximize downforce. In the case of the drag, obviously a smooth surface will create less drag than an irregular one (such as the bottom of your car). For downforce, its used like an upside down airplane wing. Airplane wings create lift through their shape because the shape of the wing causes air to move faster above it than below it. That creates low pressure and essentially sucks the plane's wing upwards. Same thing applies to undercar surfaces and rear diffussers, except instead of creating lift ABOVE the car, you create the low pressure underneath the car, so that it sucks the car towards the ground.

A rear diffuser creates the same effect underneath the rear of the car. It creates negative lift and cleans up the air underneath the rear, effectively adding stability and downforce.

Here's s pic of modern day supercars to give you a better idea...

Enzo:

GT-R

In the 70's they tried installing big fans that would suck the air out from underneath the car, effectively vacuuming it to the track. That got outlawed quick... heres a quote:

"Lotus, in 1978, developed a fully shaped underbody to its Formula 1 car that, along with sliding side skirts, created a low pressure area under the car allowing cornering speeds to soar. The side skirts would wear and often break and the sudden loss of vacuum would result in catastrophic accidents. This technique of ground effects was also banned."

"

Makes for a fun read.

http://jimsgarage.wordpress.com/2007...round-effects/

CBRich · 07-18-2009, 12:05 PM

I'm waiting for a used Enzo in the 20K price range. What a beautiful car.

And just adding a ditto on the aero effect to prevent lift.

OMGWTFBBQ · 07-18-2009, 01:02 PM

You have no idea what a hard oil change is until you check out the new Civic Si (2006+). Well, I wouldn't say "hard" I guess. It was just more troublesome than it should have been.

bboypuertoroc · 07-18-2009, 03:17 PM

I had a plastic cover under mine... removed it. I haven't noticed a difference. At least the one on an Evo has separate pieces so you can get to various places (like there's a removable piece under the oil filter for that purpose).

Alexus · 07-18-2009, 03:29 PM

Ditto on the aero effect, but what some people fail to remember is that the cover is commonly called a "splash guard." Not only will it improve the aerodynamics of the car, it will also prevent unwanted debri or pests from entering the engine bay (if conceived correctly).

I do have to agree, however, that Nissan went into overkill mode with the 16 bolts and 3 clips (which will probably be broken by most after the first oil change). It's a pain.

bboypuertoroc · 07-18-2009, 10:22 PM

Quote:

Originally Posted by Alexus

Ditto on the aero effect, but what some people fail to remember is that the cover is commonly called a "splash guard." Not only will it improve the aerodynamics of the car, it will also prevent unwanted debri or pests from entering the engine bay (if conceived correctly).

I do have to agree, however, that Nissan went into overkill mode with the 16 bolts and 3 clips (which will probably be broken by most after the first oil change). It's a pain.

At least the Z uses bolts. Evos got a shitload of those crappy plastic screw clips that either don't unscrew or break.

Modshack · 07-18-2009, 03:35 PM

Quote:

Originally Posted by bboypuertoroc

I had a plastic cover under mine... removed it. I haven't noticed a difference. .

Yeah, What the heck. Those engineers probably didn't know what they were doing anyway. Pull off the spoiler and the aero flaps in front of the wheels too..

Alexus · 07-18-2009, 07:28 PM

Quote:

Originally Posted by Modshack

Yeah, What the heck. Those engineers probably didn't know what they were doing anyway. Pull off the spoiler and the aero flaps in front of the wheels too..

He'll notice a difference when that flimsy-looking oil pan is shot or a piece of debri blows a hole through the filter, or knocks it off entirely.

bboypuertoroc · 07-18-2009, 10:24 PM

Quote:

Originally Posted by Modshack

Yeah, What the heck. Those engineers probably didn't know what they were doing anyway. Pull off the spoiler and the aero flaps in front of the wheels too..

Aero flaps?

The spoiler makes a HUGE difference. I've driven Evos with and without, and it's VERY noticeable.

Anyways, on an Evo, it's called a splash guard. Doesn't do too much IMO since it never gets dirty under there.

mattjk · 07-18-2009, 11:33 PM

it started out as drip pan, so you would not get oil drips on your driveway. (older cars)

then it evolved into a shield to direct more air through the radiator, past the engine and through the transmission tunnel to cool the transmission. the trays got longer and longer.

then it turned into an aerodynamic aid.

RCZ · 07-19-2009, 08:50 PM

Quote:

Originally Posted by mattjk

it started out as drip pan, so you would not get oil drips on your driveway. (older cars)

then it evolved into a shield to direct more air through the radiator, past the engine and through the transmission tunnel to cool the transmission. the trays got longer and longer.

then it turned into an aerodynamic aid.

is this a fact?

07-17-2009, 08:16 PM	#1 (permalink)
RCZ A True Z Fanatic Join Date: Nov 2008 Location: Miami Posts: 6,403 Drives: '09 370Z Rep Power: 1119	Modern cars makers try to keep the bottom of their cars as flat as possible to minimize drag and maximize downforce. In the case of the drag, obviously a smooth surface will create less drag than an irregular one (such as the bottom of your car). For downforce, its used like an upside down airplane wing. Airplane wings create lift through their shape because the shape of the wing causes air to move faster above it than below it. That creates low pressure and essentially sucks the plane's wing upwards. Same thing applies to undercar surfaces and rear diffussers, except instead of creating lift ABOVE the car, you create the low pressure underneath the car, so that it sucks the car towards the ground. A rear diffuser creates the same effect underneath the rear of the car. It creates negative lift and cleans up the air underneath the rear, effectively adding stability and downforce. Here's s pic of modern day supercars to give you a better idea... Enzo: GT-R In the 70's they tried installing big fans that would suck the air out from underneath the car, effectively vacuuming it to the track. That got outlawed quick... heres a quote: "Lotus, in 1978, developed a fully shaped underbody to its Formula 1 car that, along with sliding side skirts, created a low pressure area under the car allowing cornering speeds to soar. The side skirts would wear and often break and the sudden loss of vacuum would result in catastrophic accidents. This technique of ground effects was also banned." " Makes for a fun read. http://jimsgarage.wordpress.com/2007...round-effects/ Last edited by RCZ; 07-17-2009 at 08:26 PM.

07-18-2009, 01:02 PM	#3 (permalink)
OMGWTFBBQ A True Z Fanatic Join Date: Jan 2009 Location: the OC Posts: 1,886 Drives: 08 SGM IS350 Rep Power: 4550	You have no idea what a hard oil change is until you check out the new Civic Si (2006+). Well, I wouldn't say "hard" I guess. It was just more troublesome than it should have been. __________________ Zele Performance \| Varis \| Powerhouse Amuse \| Craftsquare \| Tommy Kaira \| Top Secret \| HKS \| Defi \| Volk Racing \| Cusco \| SPL \| Never ending build thread.. PM me if you have rare JDM parts for sale!

07-18-2009, 03:17 PM	#4 (permalink)
bboypuertoroc Enthusiast Member Join Date: Dec 2008 Location: Get out my way pimpin, HI Posts: 419 Drives: '06 Evo IX GSR Rep Power: 389	I had a plastic cover under mine... removed it. I haven't noticed a difference. At least the one on an Evo has separate pieces so you can get to various places (like there's a removable piece under the oil filter for that purpose). __________________ Evo IX GSR - FPBlack, 30psi... 10's on pump? Let's find out...

07-18-2009, 03:29 PM	#5 (permalink)
Alexus Base Member Join Date: Dec 2008 Location: Montreal, QC Posts: 178 Drives: The Beast Rep Power: 17	Ditto on the aero effect, but what some people fail to remember is that the cover is commonly called a "splash guard." Not only will it improve the aerodynamics of the car, it will also prevent unwanted debri or pests from entering the engine bay (if conceived correctly). I do have to agree, however, that Nissan went into overkill mode with the 16 bolts and 3 clips (which will probably be broken by most after the first oil change). It's a pain. __________________ "The object of war is not to die for your country but to make the other bastard die for his." -General George S. Patton Jr., 1885-1945

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07-18-2009, 12:05 PM	#2 (permalink)
CBRich A True Z Fanatic Join Date: Apr 2009 Location: SC Posts: 2,464 Drives: 370Z Rep Power: 545	I'm waiting for a used Enzo in the 20K price range. What a beautiful car. And just adding a ditto on the aero effect to prevent lift.

07-18-2009, 11:33 PM	#10 (permalink)
mattjk Enthusiast Member Join Date: Jul 2009 Location: Azusa Posts: 331 Drives: 09 370z K51 09 Elise Rep Power: 267	it started out as drip pan, so you would not get oil drips on your driveway. (older cars) then it evolved into a shield to direct more air through the radiator, past the engine and through the transmission tunnel to cool the transmission. the trays got longer and longer. then it turned into an aerodynamic aid.