# Why is there a giant piece of black rubber under the front bumper?



## snowwy66 (Nov 5, 2017)

I don't know why it's there. Personally I think it's a nuisance and would probably save us a buck on purchase price if it wasn't there. 

It does hold up rather well though. I"m surprised mine is still intact. If it DOES tear off. I hope it don't take the bumper with.


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## Ma v e n (Oct 8, 2018)

It's to create proper airflow through the heat exchangers and under the car.

Removing it will statistically affect cooling and HVac performance and fuel economy. You're not likely to notice unless you very carefully log temps and fuel economy though.


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## snowwy66 (Nov 5, 2017)

I don't see how it would effect cooling and hvac. The front is certainly opened up enough for sufficient airflow. 

Only thing I could see it doing is blocking air underneath in winter for oil to heat up faster. 

Seems like it's more of a NON aerodynamic air resistance thingy to me.


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## Ma v e n (Oct 8, 2018)

snowwy66 said:


> I don't see how it would effect cooling and hvac. The front is certainly opened up enough for sufficient airflow.
> 
> Only thing I could see it doing is blocking air underneath in winter for oil to heat up faster.
> 
> Seems like it's more of a NON aerodynamic air resistance thingy to me.


Let's just think about it for a minute...Why would it's only purpose be to create drag? That makes little sense. 

It limits the amount of air that can go under the car, helping fuel efficiency, it also creates a low pressure zone behind it, making it easier for air passing through the heat exchangers to flow through, down and under car. If the zone near where there air from the grille wants to exit has higher pressure than the air trying to exit it can't flow properly, affecting cooling.


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## TDCruze (Sep 26, 2014)

It is for fuel economy. It reduces air flow and therefore drag under the vehicle and thus increases MPG.

You can bet GM would not put it there if there was not a value in it being there. They will cut out a 2 cent plastic clip if they can.

They are very close to the ground on the Gen 2 Cruze so it does scrape easily.


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## snowwy66 (Nov 5, 2017)

They need to angle the plastic inwards. Instead of slamming wind resistance head on. 

Take lessons from what semi's are doing. Which are designed to move air around. Instead of slamming head on. 

Learn how wind is effected in aviation.


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## TDCruze (Sep 26, 2014)

snowwy66 said:


> They need to angle the plastic inwards. Instead of slamming wind resistance head on.
> 
> Take lessons from what semi's are doing. Which are designed to move air around. Instead of slamming head on.
> 
> Learn how wind is effected in aviation.


As soft as it is on the Gen 2, I would bet that at highway speed it does angle back some.


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## Robby (Mar 1, 2013)

It has two functions and is called a 'Airdam'.

At speed, it directs air around the car as opposed to having air tumble and get whipped up within the suspension bits and all the various bolts/brackets under the car. On a gen 1 eco version Chevrolet continued the smoothing under the car by installing panels the length of the entire floor boards. 

Secondly, it creates a low pressure area behind it so that airflow for cooling will be drawn into the engine compartment, through the radiator/intercooler/condenser and then out the bottom of the engine compartment.

As stated above, no manufacturer has ever installed a component that was unnecessary, and, in the case of the Cruze, everything installed was determined needed during wind tunnel testing to squeeze maximum mileage out of the design.
My favorite thing that can be seen is the 'bumps' on the headlamp outer housings. These direct air away from the outside mirror backs. These are found on the GenI......I have never studied a GenII but I am confident there are little air management bits all over the body work.

A benefit, it makes you stay back from parking curbs. Many drivers (not just the Cruze) have learned the hard (expensive) way what happens when the facia hooks on a parking curb and then reverses away from it........the facia will be torn off the car and stays at the curb..........bad ju ju.

Rob


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## Ma v e n (Oct 8, 2018)

snowwy66 said:


> They need to angle the plastic inwards. Instead of slamming wind resistance head on.
> 
> Take lessons from what semi's are doing. Which are designed to move air around. Instead of slamming head on.
> 
> Learn how wind is effected in aviation.


Cascadia, Evolution, W990, W900, T680, 579, 389, Lonestar, WS 5700....Which one of these modern trucks has features that you're mentioning and doesn't look like they do it very similarly to the way cars do it?

Which one of these trucks couldn't you argue is taking aerodynamic lessons learned from light duty work and applying to a class 8 rig? None of them. The tech transfers is going the opposite way of what you say needs to happen. Cars have been using far more aerodynamic "tricks" than big trucks, and for far longer.

Nearly every class 8 truck maker still offers trucks with non aero front ends and headlights, (save for Freightliner, and arguably Volvo, but their VAH and VHD are still pretty traditional). Many trucks on the road don't have aero lights or grilles, and are still very traditional, relying largely on sleeper aero, trailer skirts/tails and engine advancements for fuel economy increases. Trailer skirts and tails alone have been shown to change fuel economy as much as 15% almost irrespective of the truck towing it. And these trailer techs are all add-ons, they aren't permanent features of most trailers, and many of them still have a very Homebrew look

The things trucking companies are trying to get out of single digit fuel economies mirror the things the light duty side has been doing for years....Low rolling resistance tires, aeodymanic mirrors, low viscocity lubricants, automatic transmissions, overdrives, idle time reduction, driver education and monitoring.


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## Ma v e n (Oct 8, 2018)

snowwy66 said:


> They need to angle the plastic inwards. Instead of slamming wind resistance head on.
> 
> Take lessons from what semi's are doing. Which are designed to move air around. Instead of slamming head on.
> 
> Learn how wind is effected in aviation.


As soft as it is on the Gen 2, I would bet that at highway speed it does angle back some.[/QUOTE]

If you draw a line from the lower edge of the fascia to the lower edge of the dam you'll see it is an angle. This is as much for aero as it is for aesthetics.

If you think the engineers at GM aren't well versed in aerodynamics, and aren't cognizant of the solution big trucks use, or in the ways air is managed in aviation, you seriously deluded.


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## snowwy66 (Nov 5, 2017)

ma v e n said:


> snowwy66 said:
> 
> 
> > they need to angle the plastic inwards. Instead of slamming wind resistance head on.
> ...


smh


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## Ma v e n (Oct 8, 2018)

snowwy66 said:


> ma v e n said:
> 
> 
> > snowwy66 said:
> ...


Perhaps you'd care to share your issues with my points and observations? Am I egregiously wrong somewhere? Do you not understand what I've posted? Or have you just realized that big trucks are so far behind in the tech utilized for aero and fuel economy improvements that all they are doing is catch up....

They are YEARS behind in widespread comprehensive aero solutions, low rolling resistance tires, low 
friction drivetrains, transmission tech, idle reduction, variable valve timing, cylinder deactivation, weight reduction, electrification and hybridization, etc....

They only just recently started pioneering some really interesting thermal energy recovery tech, but by and large the industry isn't making large technological moves forward.

And this is why fuel economy on big trucks isn't in the double digits yet.
Nationally (USA) fuel economy is only 6.5mpg or so, with many fleets and O/O still getting below 5mpg, and only the most dedicated and invested getting over 8. I don't know of any non experimental OTR fleet that averages 10mpg.

If there were 500, or 5000 trucks out there hauling heavy weight getting 10mpg, and using unique tech or novel solution s that light duty wasn't, I'd be inclined to say sure, maybe GM should look at what those guys are doing....But it's not happening. There's nearly infinitely more trucks living in the 5mpg range (like they have for 20+ years) than there are in the 10, or even 9mpg range.

11 or 12mpg might be the technological cap to a fossil fuel powered 40 ton rig...But they aren't even close to that, they can't even get basic relatively inexpensive aero on the trailer fleet yet

I sit next to more cars with autostop in one day than I see trailers with skirts and tails in one month.


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## nightfallgrey2018 (Nov 15, 2017)

snowwy66 said:


> smh


What is it that you don't understand? 1+1=2!


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## Jondaytona (Apr 26, 2018)

I've noticed everybody in this thread is a "dam" specialist! :th_SmlyROFL:


(sorry, couldn't resist)


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## snowwy66 (Nov 5, 2017)

nightfallgrey2018 said:


> snowwy66 said:
> 
> 
> > smh
> ...


roflmao


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## Iamantman (Sep 24, 2018)

yeah its an airdam but im surprised no one has mentioned that its a pretty great bumper guard as well. personally, id rather scrape that a little instead of an expensive front end clip. or worse, an engine component.


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## Ma v e n (Oct 8, 2018)

Iamantman said:


> yeah its an airdam but im surprised no one has mentioned that its a pretty great bumper guard as well. personally, id rather scrape that a little instead of an expensive front end clip. or worse, an engine component.


Because on many of these cars, my 18 Redline HB included, if something is high enough to damage front fascia, you're hitting the fascia before the airdam. It doesn't work as a feeler for curbs.


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## Iamantman (Sep 24, 2018)

Hmm we might be talking about a different part then. The thing i'm referring to is a piece of plastic that extends down from the underside of the car about 2 inches and has a slight curve that follows the curve of the front end and has a couple of tiny little "fins" on each side that I assume disrupt the airflow. 

I have for sure scraped that on things on multiple occasions. At least I think. Now that you say that though I'm going to look under closer and see if the front fascia is scraped. But pretty sure that thing is taking the hit each time though.

Here you go. Quick screen grab from google. This thing right?


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## Ma v e n (Oct 8, 2018)

Iamantman said:


> Hmm we might be talking about a different part then. The thing i'm referring to is a piece of plastic that extends down from the underside of the car about 2 inches and has a slight curve that follows the curve of the front end and has a couple of tiny little "fins" on each side that I assume disrupt the airflow.
> 
> I have for sure scraped that on things on multiple occasions. At least I think. Now that you say that though I'm going to look under closer and see if the front fascia is scraped. But pretty sure that thing is taking the hit each time though.
> 
> ...


Yeah, but if you hit that, you either weren't gonna hit the fascia/lower black lip of the actual front clip OR you hit the front end first, because that flexible, easily and cheaply replaceable airdam is farther back the than the front lower edge of the bumper...Meaning you hit the bumper before you ever scrape the airdam.


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## Iamantman (Sep 24, 2018)

Well, you're right and wrong. It's very flexible so it's not offering the protection I thought it was but I just looked at mine on my lunch break and it is clearly scuffed and rashed whereas my front fascia is in perfect condition underneath. So I've definitely been touching it and hearing it from inside the car. I think it's more of an audio cue that it was a close call more than anything else though. Its also right up front so I think you might have a different mental image of where it's at. 

But I derailed a bit so sorry. We already answered what it was here


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## HBCRUZE2017 (Jan 25, 2018)

lol wait till your lowered i scrape on pretty much every driveway thought about removing it but meh


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## Iamantman (Sep 24, 2018)

Haha dude, that's exactly why I'm scared to lower it. I've thought about the GM kit because I like the idea of a half inch drop with improved spring rates and how it will look and handle with bigger wheels, but a 1.5" drop or more scares the **** out of me. I live in downtown Philly and I would just be begging to destroy my front end.


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