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Old November 27th, 2019, 07:23
Mishimoto Mishimoto is offline
NAXJA Forum User
Join Date: Jun 2014
Location: DE
Posts: 26
Mishimoto R&D: XJ Performance Fan Shroud

Hey everybody,

My name is Steve and I work for Mishimoto Automotive. If you're not familiar with us, we make cooling products for a huge variety of vehicles, including a radiator, and now a fan shroud, for the XJ.

We wanted to share our R&D behind our new fan shroud and hear what you all think! Also, if anybody can get us in touch with whomever sets up sponsorships for the forums, we'd like to pay for our membership, but haven't gotten a response to our PMs or emails.

Check out the R&D below and let us know what you think.


Constant Stride Ė Fan Shroud R&D, Part 1: Production

Driving off the beaten path is a constant stride. Every throttle input and steering angle change is carefully calculated to overcome the obstacles in front of you. All it takes to break that stride is one misstep. A coolant temp gauge climbing into the red or a wisp of steam from under the hood is enough to take your focus off those obstacles and lock it on your dash. Suddenly, the challenge becomes cooling down your vehicle instead of making it to the end of the trail.

Overheating is an all-too-common occurrence for many Jeep XJ Cherokee owners. Off-roading is also an exercise in low-speed driving and for the XJís outdated engine fan, itís an exercise in futility. When the XJís 4.0L engine is churning at a pace just above idle, the archaic engine fan is barely moving air through the radiator. Low fan and road speeds, coupled with the extremely high load of crawling up a steep grade leads to rising coolant temps. The only way to move more air through the radiator with the stock fan is to increase the engine speed or road speedóboth could be disastrous in an off-road situation.

One solution is to ditch the mechanical engine fan and substitute electric fans that spin at a constant rate regardless of engine speed. An even better solution would be to enclose those electric fans in a shroud that tightly hugs the back of the radiator. A well-designed shroud ensures that air is only pulled through the radiator and not from the hot engine bay. But thereís a challenge specific to the XJ that makes building a fan shroud like this problematic: space.

The XJís 4.0L inline-six engine is nearly three feet long from the bellhousing to the front of the crank, and itís longitudinally mounted (front-to-back). That leaves little room in the engine bay to mount fans. Less than four inches exists from the shroud mounting points to the front of the engine, to be exact. With our 10-inch fans measuring 2.36 inches deep, we had just under two inches to work with.

To make the most of the scarce space, we decided to keep our fan shroud in the spirit of the XJ, simple but effective. Two electric fans will take the place of the mechanical fan, while a third acts as the A/C fan. The shroud itself will be made up of a flat sheet of aluminum that attaches to the stock shroudís mounting points. A small lip at the bottom of the shroud will close off the gap between the shroud and the radiator to improve efficiency.

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