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Is the inner fender necessary?

18K views 15 replies 10 participants last post by  spyder6 
#1 ·
I attached a couple blurry pics but I installed the xrc steel fender flares over the weekend. The inner fenders are not reuseable bc I ruined them. The install instructions implied that they were not necessary but the more I look at the exposed
areas I'm questioning it. I know metal cloak has an answer to this problem but was curious if anyone has ran like this for a little while.
 

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#2 ·
On and off road the inner liners protect the engine bay components from water/dirt/mud/debris.

They may not be needed in a rock crawling situation.

On the road, they help with engine cooling, as they prevent most of the air pushed into the wheel wells from entering the engine bay, thereby allowing more air to pass through the radiator fins. You may not see a problem until you are approaching the limits of the cooling system's capacity to remove heat from the water.
 
#3 ·
ditto, if all you do is trailer your vehicle for rock crawling...probably not, but in an every day situation or off road general, yes, they protect the engine bay from nasty stuff and keep water out of places it should not be.
 
#7 ·
Thank you for all the responses. My plan is to have the rear line x'ed. I can't believe all the protecting the front liners did from what you all are describing. The jeep is my second vehicle that sees a fair share of on road time and some off road time but no mud. I was just basically curious if I could get by like it is on the front for a while until I find something to put back on there.
 
#10 ·
^^ This.

Completely unnecessary.

Don't believe me? Go through a mud puddle or look at the engine after a hard rain and driving through it. It's going to be wet. The electrical components are already pretty well protected.

What they're good for:

A little sound deadening.
Protection against gravel being thrown up and pinging the sheet metal in the rear.
Keeps the engine a bit cleaner. Not totally. Just some.
Good for being in the way when you're wanting to reroute something lower in the engine bay.
Great for trapping salt and chemicals and introducing rust areas.

Used rubberized undecoating or bedliner on the exposed sheet metal and you won't have problems.
 
#11 ·
If you need a new set of inners, just check a junkyard. Or, I just removed my flares and inners to replace with metalcloak stuff, so I have a full set too.

While I agree with inners not really being "necessary", I bought the MC inners with my fenders for 2 reasons - to dress it up a little and to help with air flow - inside the engine compartment and aerodynamics. They help from those standpoints, but not for keeping the engine clean.
 
#13 ·
I meant aerodynamics from a handling/noise perspective. I felt that on the highway without the inners it was a lot more flighty in crosswinds/turbulence. Definitely seemed windier by noise.

As far as cooling, yeah, high speed isn't an issue. I was thinking more at low speed cooling
 
#15 ·
Even the best fan can't force air into a pressure that's already higher than the pressure created by the fan. Case in point - we had a 69 Camaro super stocker running round tracks - both dirt and asphalt. Since the dirt required turning RIGHT (cross steering during left turn corner slide) we had to cut the tire well back 7". That raised the underhood pressure and we saw a 10 degree increase in temp (from 225 to 235) - as well as less nose weight at speed - so had to run two fenders - one for dirt and one for asphalt (of course that said it WAS a engine driven fan and we ran about 900 RPM difference at the two tracks). One thing to note though - as air resistance increases - so does the amperage draw of the fan motor - adding more air under the hood through the fenders will raise the pressure and thus draw - and of course that shortens the life of the fan!

Side flow does not really come into ground effect equations noticeably until around 60ish - under that only frontal changes makes big differences.

The JK is arguably not that extreme - so the liner would not be a horribly bad thing to ditch. But as the temp gauge on the dash does NOT display actual temp - only a computer display of whether current temp is in "expected" normal range - based on the operating and computer parameters - so you would have no way of knowing you are running warmer unless you have installed a separate non oem gauge (or a live display on a handheld code scanner). I Have used an infra red and seen temps (at the radiator inlet tank header) of 195-205 always with the dash gauge straight up on the normal line.

I would have no worries running without them - but when I do start modding there I will use something - I don't like road water (or more precisely the fine grit that comes with it and thus gets in all the wiring harness, connectors etc.) getting under the hood! The factory pieces ARE repairable with a fiberglass repair kit - just rough the surface, lay the mat and one coat of resin (do the bond work where it won't show as much - engine side for example) along any tears cuts or breaks.
 
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