The Jeep Geek

The Jeep Geek's Blog
Aug 2010

Getting a Lift

You have seen them heading down the road...maybe you’ve seen them out on the trails...Jeeps with oversized tires. So how do they fit on a Wrangler? Simple, you add a lift to the Jeep to make room for the Tires. Other mods may be needed as well depending on tire size.

This article is the first in a series on lift kits and considerations that you should think about before lifting your Jeep. The Jeep Geek has helped many people find the perfect lift for their Jeep and will contribute his expertise here.

The Jeep Geek is often approached by customers who see a Jeep ,like the one in the picture above, that has been lifted with a 4 1/2” long arm lift. They tell him that they want one like that. The Jeep Geek then begins asking a number of questions and in the end saves them a lot of money and they end up with one that will serve their needs a lot better.

The Jeep Geek would like to comment at this point that he loves the Mopar 4 1/2” kit shown above...but this lift may not be the right solution for everyone. He has at least one customer who purchased this lift and had to modify their garage door to accommodate the added height of the vehicle. A little prior discussion may have yielded a more harmonious solution for the home.

So here’s how The Jeep Geek makes the determination as to the type of lift to recommend. First, are you going to off-road with this Jeep? Some folks buy the lift to put larger tires and just are interested in the appearance. Nothing wrong with this, its all about personal preference. In this case The Jeep Geek determines budget. A 4 1/2” lift kit costs about $7500 installed, the 2” Mopar lift kit is about $2500 installed.

If the answer is that the owner wants to lift it for off-road use, then The Jeep Geek wants to know where and what type of obstacle they intend to try to conquer. If their intention is extreme rock crawling, the Mopar 4 1/2” long arm lift kit will probably hold up better than a short arm 2” kit.

But the bottom line is what size tires does the driver want to put on. On the JK Wranglers the 2” lift kit will support 35” tires. The 4 1/2” lift kit will support 37” tires. Now we are just discussing clearance issues with the body and frame. Another consideration is the model Wrangler the customer owns (or is intent on purchasing). For example the Rubicon has Dana 44 differentials on both front and back axles. The Sahara and Sport have in Dana 44s on the rear axle but have Dana 30s on the front axle. The Dana 30 will support 35” tires, but the Dana 44s will support 37” tires. So if they don’t have a Rubicon, The Jeep Geek recommends a 2” lift.

The point of a lift is to improve off-road ground clearance. A 2” lift will provide 2 inches of clearance for the frame, but the Differentials will remain at the same ground clearance. The larger tires is what gives more ground clearance for the differentials. So if the Jeep has 32” tires standard and we add a 2” lift and put 35” tires on, the ground clearance at the differentials will have improved by 1.5” (half of the tire increase in size). However in this example the overall height of the vehicle will have increased by 3 1/2”...2 inches for the lift and 1.5” for the tires.

Now there is more to a lift than just size. In the next article The Jeep Geek will discuss some other considerations i
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Fording...a Primer

Safe fording is about technique and a little common sense. In the previous articles we have talked about equipment and the picture above illustrates the drawback of a cold air intake...if this Rubicon had a cold air intake system it would be sucking water into the engine. However the OEM air box draws air from the top of the engine compartment near the front right hood latch. Obviously a snorkel mounted above the hood would make this particular crossing even safer...so would a change in technique.

No river or stream should be forded until you walk through your intended path. You are going to get wet...get over it. There are a couple of reasons for walking the path. First and most importantly is that you want to verify the depth and speed of the water. If the water is moving so fast that you can’t walk it...your jeep will be swept downstream. If the water gets too deep, then you will destroy your engine. Since water depth and speed can’t be judged from a distance, you have to get wet to make sure that your line is going to work.

Secondly, the safest way to cross a stream or narrow river is to winch your jeep across. Yup, walk across the stream out-hauling your winch line and secure it to a large tree or rock. Then wade back, put your transfer case in neutral, turn off the engine, and release the break. Winch across and there is almost no chance of damaging your Jeep. This approach won’t work if the stream or river is wide, current is rapid, or there is nothing to put your tree strap on. However where possible this is the way to go.

So at what angle should you cross a stream? For years we where told that we should cross at about a 45 degree angle, more or less in line with the current...the rationale was to present less sail area for the current. All this is well and good, now the tread lightly folks are telling us to cross at a 90 degree angle...the rationale being that this more acute angle is easier on the stream habitats.

Here’s the thing. The Jeep Geek feels you should cross at an angle that is determined by the trail. So if the trail is a 90 degree crossing, cross at 90 degrees, if the crossing is at 45 degrees, then cross at 45 degrees. This approach will prove the least impactful to the environment. The Jeep Geek is a fan of Stay the Trail Colorado and recommends that off-roaders stay on existing jeep trails whenever possible.

A final word...The Jeep Geek has watched the new 2011 Jeep Grand Cherokee ads with a great deal of interest and pride. This vehicle is going to be a real game changer for Jeep. However, one of the commercials scares the cr@p out of The Jeep Geek. It is the one that shows the Grand Cherokee blasting through the stream, throwing water over the hood. If you do this with your Jeep, you will find yourself facing a very high repair bill when water is sucked down the intake, into an engine cylinder. The cylinder will explode making a very loud bang and blowing the head off that side of the engine, breaking the crank shaft and sending fragments of the cylinder walls into other parts of the engine.

Any river or stream ford should be done slowly...just like the one pictured above. If you are splashing water up, then you are in danger of a many thousand dollar repair bill.
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Snorkels may be the Solution

In previous articles The Jeep Geek observed that a drawback of a supercharger or cold air intake is that it reduces the ability of the Jeep to ford rivers. So how can a Jeeper who loves to ford still get the power increase that they want?

The Jeep Geek has carefully researched this vexing question and has come up with two solutions. One solution is a technique discussion that will comprise the next article, but for this article we will look at an equipment solution.

The solution to having the air intake too low is to raise it. Yes, The Jeep Geek knows that this is obvious. Here is how to do it.

Use a snorkel. Here is the catch...sigh...there is always a catch. Most snorkels on the market are not cold air intakes...in other words they use the OEM air box and just connect a longer pipe to the intake port on the top of the air box. This approach won’t allow for the performance gains we have been talking about since it will continue to restrict the input side air flow.

However, Volant has created a combination cold air intake and snorkel that replaces the OEM air box and opens the input side nicely. The Jeep Geek has included a picture of a Jeep that has been modified with the Volant Snorkel.

While this approach should provide both the performance gains that come with a cold air intake or supercharger, it will also provide protection while fording by lifting the intake to a position at the top of the Jeep...say 72 inches above the ground (or more if you have lifted your Jeep).

So will the maximum depth that you can ford suddenly become 72 inches just by adding this snorkel?
No. There are other limitations such as the electrical system and...of course the ability of the driver to breath under water. What the Snorkel will do is prevent the dramatic engine damage when water is sucked into the intake system. If the electrical system gets flooded, it is just a matter of drying the system out and you are on the road again...a cheap fix. The Jeep drive line, electrical system, and passenger compartment are somewhat water resistant...but your Jeep is not a submarine.

So are there any drawbacks to the snorkel...is this the perfect solution? Sorry, no, not perfect. Adding the snorkel will require more cutting on the hood of your Jeep. If you have added the Avenger supercharger as we discussed in a previous article, then you are getting to the point where there is not a lot of the original hood left. Aside from the modifications to the hood, the Volant snorkel has a flexible section in the snorkel pipe to allow the Jeep hood to be opened, however it will require a bit more work and will not open as widely as an un-modified hood. This is more of an issue for the friendly technician who works on your Wrangler as they usually lean the hood on the windshield to get it out of the way. They won’t be doing that with this setup.
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Superchargers are Super

Superchargers are super...or are they? In this series of articles The Jeep Geek has attempted to show that there is more than one way to get more power from a 3.8L V6 powered Wrangler. In case you have missed any of the previous articles, there is a stage one upgrade that opens the breathing of the engine, a stage two that involves adding a supercharger, and possibly a stage 3 that involves replacing the 3.8L V6 with a Hemi engine. This is pretty extreme, but will result in maximum horsepower and torque.

So back to superchargers. The Jeep Geek likes this solution for several reasons. First, the Supercharger is not an extreme solution like a Hemi conversion (that involves replacing engine, transmission, possible transfer case, drive shafts, upgrading differentials, etc.). Second, the supercharger allows for the increase in power to result throughout the RPM curve...in other words, you get boost at the low end where you want more power. This is especially true for off-road use. Compared to a turbo-charger which provides the increase in power at higher RPMs, the super charger gives a flat (good) response throughout the range of engine speed.

So what makes a supercharger work? The Jeep Geek is glad you asked. Remember from yesterday’s article that adding cooler denser air enables a better burn in the cylinder...what what the supercharger does is pump air into the intake of the engine. Depending on the demand (pedal on the right...yup, gas pedal) it provides between 0 and 8 PSI of additional air pressure. It is dense and loaded with oxygen. It is also cooled by the inter-cooler which uses an additional radiator that is mounted in front of the main engine radiator. The pump runs on a belt that is driven by pulleys on the front of the engine...this means at idle it is driving air pressure and makes the boost available at low RPMs as discussed above.

A turbo-charger also provides additional air pressure, but runs by a turbine fan that is driven by exhaust gas on the output of the engine...this is generally not available at lower engine RPMs.

So why wouldn’t a person put a supercharger in their Wrangler? Well, the same issue exists with a supercharger as a cold air intake system, the intake is lower and this will impact river fording.

Also, there are some minor issues, first, it is still unclear if the addition of a supercharger will impact factory warranty. The Jeep Geek knows if the supercharger is not setup correctly and provides too much boost the engine will “lean out” and this will burn up the pistons. This repair is expensive and will not be covered by Chrysler. There is also a local issue which we may be able to resolve soon. Every two years here in Boulder County we have to have our vehicles’ emissions inspected. Part of that process has the technician (at the inspection station) open the hood and see if there are modifications to the engine. Modifications are OK if there is a sticker under the hood indicating that the manufacturer of the modifications has passed a certification for emissions. If there is no such sticker, hang it up...it will not pass and you will not be able to license it to drive it on the road. Many localities have similar inspections and they could be problematic.

The Jeep Geek would also like to point out that the installation of most supercharger kits (including his favorite...the Avenger) requires that a large hole be cut in the hood. This can be covered up with a hood scoop, but it won’t appeal to everyone and will require some body work (and associated expense) to make this look good.
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A Little More About Power

In yesterday’s article The Jeep Geek mentioned a stage one performance kit adds 20 Hp and 30 ft-lbs of torque. Subsequently he read in some forums comments that some folks have posted that indicated that they were less than satisfied at the performance gain they received by just bolting a cold air intake on. If this is all they did, The Jeep Geek is not surprised. Let me explain.

When you look at performance increases you have to take a systematic view of the problem you are trying to solve. By only adding one component you may not see anywhere near the performance gain that a manufacturer advertises for that component.

So are the manufacturers lying about their performance improvement numbers? Not specifically. What a manufacturer typically does is tests a population of their products (say around 10) on a number of Jeeps. They then either average the performance gains...or pick the best result and advertise that. If they bolt the product on a unit that is in need of a tune-up they will not get much gain...if they bolt it on a unit where the exhaust system is upgraded, or otherwise opened up a bit, then they get a better result.

So back to the issue of cold air intakes. They work pretty well, but only show gain if they are paired with other components. Think for a minute about the engine as an air pump. If you open the intake, but don’t open the output side, then you only move the tight spot from the front (intake) to the back (output). Any improvement in efficiency is limited by the restriction from other components.

No (or little) gain will come from just putting on a cold air intake system by itself. However when paired with a throttle body spacer and cat-back performance exhaust the improvements are noticeable.

So how does a cold air intake system actually work? There are a few effects that happen when they are added. First, the filters have more surface area and therefore provide less restriction to the air flow. Second the pipe leading from the filter to the throttle is smoother and provides less air turbulence to the air...turbulence slows the air flow. Third, it pulls the air from lower in the engine compartment where the air is a bit cooler. Cooler air is more dense and therefore has more oxygen so there is better combustion in the cylinder.
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The Hummer Recovery Vehicle

If you live in or near Boulder Colorado you may have actually seen The Jeep Geek roaring by you in the “Hummer Recovery Vehicle” (probably on his way to a Starbucks). Yes, roaring by...in a 2008 White Rubicon with the 3.8L V6 mini-van engine...a concession to the old school Jeepers out there.

So this will likely raise an eyebrow or two...this engine has more horsepower and more torque than the old 4.0L I6 engine. The Jeep Geek actually dyno tested this and can prove it. Sitting high on his office wall is a torque curve, measured at the rear wheel proving this audacious claim. So why does this vintage of Wrangler feel so sluggish? The Jeep Geek thinks it may be because the JKs are a thousand pounds heavier than the older TJs. acceleration is a function of power to weight ratio and the point in the torque curve where max power is developed.

What can be done to boost the torque and horsepower of the JK models? The Jeep Geek is glad you asked. There are a few things that can show a noticeable difference...short of a Hemi conversion...

Stage one is replacing the OEM air box with a cold air intake, adding a throttle body spacer and replacing the exhaust with a higher performance cat-back system. This is only worth doing on a manual transmission version of the JK as the automatic transmission computer tends to de-tune the engine controller thereby reducing the output. However on the manual transmission JKs we are seeing an increase of 30 ft-lbs and 20 Hp. These improvements were measured by The Jeep Geek at the rear wheel and can definitely be felt by even the most dull drivers.

Stage two is bolting on a super-charger. There are a number of kits out there, but caution is needed. Boost over 8lbs can cause damage to the engine...so only kits that have boost limiters should be considered. The Jeep Geek is aware of a kit that was developed here in Colorado (at altitude). The avenger supercharger kit includes an intercooled supercharger, larger injectors, and a complete engine software map. This kit will provide a greater than 50% increase in torque and horsepower making it a dramatic improvement in Jeep acceleration. You will have to cut a hole in the hood to make room for some of the components that are bolted high on the engine. Avenger makes a hood scoop to hide this hole, otherwise a good body shop should be able to fashion something that will look better.

The stage one upgrade will not impact the Jeep’s warranty, The Jeep Geek is still trying to get clarification from Chrysler on the stage two modification.

Costs for these mods:

Stage one is about $1750 installed with Mopar parts

Stage two is going to be around $5000 with some budget for a body shop to help make the hood scoop look good.

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