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Discussion Starter · #1 · (Edited)
As many of you know I permanently shelved the lower engine shroud nearly a year ago. Its presence adds significantly to engine bay temperatures and contributes to engine heat soak. As does the upper cowl, which is only on my ride when she goes to see the dealer, if then.

Be aware that you'll need to anchor the leading edge of the front fender well liners to something stout in behind the bumper at the time you remove the lower engine cowl, which acts as a stiffener for the liners. Otherwise aerodynamic forces at or just south of the speed limiter are enough to push said liners back into the tires.

To do so, run a long, stout, nylon zip tie through a hole at the bottom of the forward edge of your fender well liner. Find something sturdy at the rear of your bumper and route the zip tie (may take two to reach) through it then hook it back into itself, making an elongated loop.

Failure to do so will result in the leading edge of the fender well liner getting chewed up by the tire(s) while the vehicle is at warp speed due to aerodynamic pressures pushing the liner into the tire.

A rather spectacular phenomenon: 'Creates the visual impression that the Red Baron may have just gotten off a lucky shot or two on you when you check your mirrors and see that you're trailing smoke.

While at warp speed no less.

So when you do ditch the lower shroud, anchor those puppies up before yours get a bit ragged looking like those belonging to somebody else we all know. :)

Background information:

The lower shroud is intended to improve the car's aerodynamics. Airflow management engineers worked long & hard to get the coefficient of drag (Cd) of these very squared off LXes down to a respectable Cd of between 0.33 and 0.35.

All of this was considered before removing my lower engine shroud. But extreme engine compartment heat takes such a much larger toll on performance and fuel efficiency than does a 0.0014 increase in drag that it was a no-brainer to remove the lower engine shroud. For anyone bemoaning the slight Cd increase: Always driving a freshly waxed car vice a dirty one would likely offset this miniscule Cd increase. It's all about perspective - the big picture.

The damaging effects of extreme underhood temps on all components residing there should not be overlooked. Prior to removing my lower shroud and the front vent blocking plates I would be literally be rocked back on my heels by the rush of super-heated air escaping when I'd open the hood to check oil, etc., at a fueling stop in desert summer. It was exactly like opening an oven which has been set to a very high temperature - unbearable. Removing the shields has easily reduced peak summer under-hood temps by 75 degrees or more.

If someone truly wants to improve their Cd, pull your flashy mesh grill guards and replace them with the stock blocking plates. Open front vents (adjacent to your fogs) increases Cd by 5 points, vs. the 1.4 points that the lower engine shroud increases it. But at the expense of brake cooling and, for many of us, cool ram air to our air filters.

It's all about perspective.

Which brings us to the topic of winter slush & slop. Those of you living in Northern Tier states and beyond don't experience the extreme summer heat that southern tier states offer. You also have the issue of winter slush & slop. The lower engine shroud no doubt helps keep much of that slop out of the lower portions of the engine bay. So use your own best judgement as to whether this mod is for you or not. If you frequent the track I'd suggest you at least consider removing the shroud for the racing season.
 

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Excellent write-up, Jim. I agree totally with your reasoning. I recently had a wiring harness melt due to excess engine bay heat while running laps.

You mentioned the lower vents by the fogs. Opening these up actually give cooling to the front brakes.

In April, when I swiitch back to summer tires, I may try turning my lower shroud into "swiss cheese" with a number of 2" holes rather than remove it - just to give some barrier from the winter crud. Cutting holes may set up some interesting wind noises and whistles - so it may not work. I will report back with results when the mod is done.

Again, thanks for the write-up.
 

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Discussion Starter · #3 ·
Northern Rider said:
...You mentioned the lower vents by the fogs. Opening these up actually give cooling to the front brakes...
Certainly, Pat. And a perfect source of ram air to the air filter for many of us.

The comment was placed there to show some members, in another thread, who appeared to be placing minor coefficient of drag increases ahead of practical reasons for removing the lower engine cowl that they were perhaps not looking at the big picture.
 

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Well I never imagined that they would put vents there, then put a blocking plate over them. I'll look tomorrow.

I imagine the SRT8 lower plate isn't much better. It's metal so it will conduct heat better, but it still stops convection, and with all the air movement under a moving car, convection would be very important.
 

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Discussion Starter · #6 ·
artichoke said:
Well I never imagined that they would put vents there, then put a blocking plate over them. I'll look tomorrow.

I imagine the SRT8 lower plate isn't much better. It's metal so it will conduct heat better, but it still stops convection, and with all the air movement under a moving car, convection would be very important.
The vents aren't blocked on your ride, Arti'. The SRT8 design team was not one to let a minor drag coefficient increase stand in the way of improved cooling and performance. They made sure the vents were properly utilized.

grinner said:
great write up, man. I always like what you have to share.
The sentiment is totally mutual, grinner. Thanks.
 

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So, how much did this little lesson cost you? Red Baron...LOL!
 

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Ok... so I know this is a 6 year old post ... However, I recently had a run-in with a large rodent-like creature with a hairless tail (either opossum or nutria - ask what a nutria is and I'll tell you it's a giant rat-like rodent native to Louisiana) ... anyhow... it tore the lower engine shroud off of it's bolts ... poor fella ... (the engine shroud... not the giant rat). So, I got to thinking ... well, do I need it? After reading this post, and after dealer cost and labor quote to replace it (about $300 including tax) ... I, at first, said, "No, I could use that $300 on a carbon fiber CAI or something else to mod my ride". Then, I thought, "wait, what if the hairy beast has a brother or cousin that meets me late at night on a two lane road with no shoulder and I DON'T have that lower engine shroud ... what would the damage be then?". Well, I ask the question to you guys... other than the obvious answer: Don't hit anything again... Is there a point where risk outweighs a bit of a performance improvement. For me, and i can only speak for myself and the knowledge of the likeliness of another critter crossing my path... I think the $300 is going to have to go to a replacement shroud. Any thoughts?
 

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Sounds like its more for a low drag coeficiancy and to keep the engine clean,If you don't plan on going 180mph every day ,i say it is not needed and i know it gets hot down there, heres some thing else to help keep your engine cool.as far as critters, well they made cars with out this and they have done just fine. just my.02c
 

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I think you need it to assist cooling, as well.

I know Jim (Meister) took his off, and I did the same with mine, when I spent some time with him in arizona back in '07.

However, I think this was one of the rare times when Meister's superior tech savvy has proven to be wrong. The SRT guys said that we "need it there", when talking about heat soak issues in the engine bay. Something to do with positive and negative airflow and getting max airflow through the radiator . . .

So mine is back on now. Seems to run cooler - and keeps the nutrias out of the engine bay!
 
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