fixing clanks' holes/jeep tj help

[TheEnemy]

A word of caution about blocking too much air to the 4.0, the Jeep inlines tend to get pretty hot. Particularly when they are loaded down.

If you ballance blocking air going into the engine compartment with better exit flow you might be able to improve cooling and aero. On my CJ I cut a large vent out of the hood and it dropped temperatures by about 10F. Its not pretty but it is effective.

The aero on these are so messed up that a boat tail would likely have no effect. I experimented on a windy day with a stick and plastic streamer seeing where the air flows (bikini top only), and about half way down the sides the air was pretty turbulant.

Personally I would go with a smooth sloped skid plate to divert the air below the steering lingages and front axle. They also make "tummy tucker" center skid plates that should help and give you mounting points for lighter cloroplast. I would suggest a rounded air diverter on the front of the center skid to block air between the skid and body. Leave the area between the front axle, engine and body open for exit flow from the engine compartment. Behind the center skid install another to divert the air down below the rear axle. Some cloroplast from the bottom outboard of the frame to the bottom lip of the body to cover up the body mounts.

[TheEnemy]

Also make sure that what air you are letting into the engine compartment goes through the radiator so that at least its doing something constructive.

[baldlobo]

Yes, i know the 4.0l runs warm; the engine fan came on yesterday and it normally never does at 23c. Considering behind the grill is a "big" space before the rad, was thinking of coroplast diverters(forcing air into the rad rather then what it's currently doing behind the grill block)

[skyking]

That's a good idea. I plan on forcing all air that comes in the front through the radiator and intercooler.

[baldlobo]

well got through my first tank, not so good probably 15mpg.

but i did finally get my bluetooth obd adapter to work with the jeep; the torque app is currently reading 17.5-18mpg not too bad for what little i've done.

i will say two(considering one doesn't answer questions) of the posters in this thread, have made me question where either are coming from:

1. 14 inch air dam(total ground clearance from bottom of bumper is 19"), to me that sounds like cd disaster. 8-9 inch drop for a skid plate sounds more areo too me. along with that going 10km or faster, with no wind; i'd be over my trouble spots in seconds, along with the air having it's velocity changed by the skid plate forcing the air down it(part of bernoulli's principle)



2. covering in from the factory skid to the gas tank; to put this into perspective all the mounting parts for the rear are inboard(spring perches, shocks, track bar, anti-roll bar, 4 control arms, and a nice drive shaft.), that piece of coroplast would look like swiss cheese, and probably be more of a detriment.

[TheEnemy]

Originally Posted by baldlobo

well got through my first tank, not so good probably 15mpg.

2. covering in from the factory skid to the gas tank; to put this into perspective all the mounting parts for the rear are inboard(spring perches, shocks, track bar, anti-roll bar, 4 control arms, and a nice drive shaft.), that piece of coroplast would look like swiss cheese, and probably be more of a detriment.

The rear will be the hardest to fix up, I don't know the specifics on your year Wrangler and what differences from when my CJ was built but there is no way to make either perfect, just better than it was.

I almost forgot, Synthetics in the gearboxes, we loose about 25% of our power before it even reaches the tires.

[baldlobo]

not mine, but it's raining out; so surfing is the next best thing.

02tj755431

vs and 85

http://www.collinsbrosjeep.com/image...85cj139848.htm

[baldlobo]

haven't really done anything on the jeep lately, but here's a video

found an interesting video of a toy jeep tj(it's a little dark)

Model Jeep in Wind Tunnel - YouTube

[baldlobo]

finally got the front skid plate installed, noticed some stuff;

1. doesn't suck back gas nearly as fast(330km over 34l or 10.3l/100km(combined city/hwy(90/10)

2. intake air temp drops(4-5 degrees C) from a dead stop, when speeding up(and the mechanical fan doesn't turn on)

3. was driving in the rain doing around 80kph, water from the road was hitting the floor(i'm thinking either suction, or the first angle of the skid plate is launching water off the ground via air pressure) meaning possible revision may get better results

[Sven7]

Originally Posted by baldlobo

sven7; are you familiar with Bernoulli's principle?, my jeeps underside isn't flat like a car's is.

the abridged version is longer distance around lowers static pressure and increases dynamic pressure, there's a higher pressure in the bubble under the jeep, the air going down the skid would accelerate, creating a boundary layer. lift, i think suction would be more likely; that's if you take away the side wakes, and gusts of wind.

High pressure under the car means lift. It's like a stationary fan blade pushing air down. Better than bare axles, etc. but not as good as an aero undercarriage. Anyway, glad to hear the smooth surface is working out.