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| The Ultimate SUV? | Short Cuts | ||||
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By: Martin Ahlers - 9/2000
Beginning the Install / The Grunt Work
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| Fresh 4.7l V-8
Photo by: Martin Ahlers |
What you start out with is a brand-new engine from Jeep that is, in my opinion, one of the best inexpensive American V8’s ever designed and mass produced. It’s exceptionally well engineered, and uses some technology and manufacturing tolerances that are in the race-ready category. The cylinder heads, for example, are high-precision aluminum alloy overhead cam units that utilize very trick combustion chambers. The pistons, rods, bottom end, and overall structure of the block are all hefty enough to handle way more power than the Kenne Bell unit will add to the package. From what I hear, DC plans to bore and stroke this engine in the future, and therefore over-designed the first generation 4.7 V8 so it will easily handle the extra power being planned on the drawing board. This is very good for those of us that want to add massive performance and maintain reasonable gas mileage. The 4.7 V8 is just the right size to deliver adequate mileage and performance and, when you really get into boost with a supercharged version of this great engine, performance is on par with the biggest of big blocks (and gas mileage adjusts proportionately). With a supercharger, during most of the car’s duty, you’ll be getting very reasonable gas mileage. When you need that extra 100 or so horsepower, it’s right there and ready to go. In my opinion, this is the best of both worlds.
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| Air box and air cleaner removed, exposing the throttle
body.
photo by: Martin Ahlers |
The first step in the transformation process is to get rid of the stock airbox and aircleaner. Once you do this, you’ll see another of DC’s excellent design features – the composite intake manifold. It is almost a shame to have to toss this in order to install the supercharger – it provides excellent airflow, light weight, and best of all, consistent thermal properties. With cast iron or aluminum manifolds, heat is conducted from the cylinder heads into the manifold which, in turn, heats the intake air and causes it to expand quite a bit.So, when the air expands, you get less oxygen per unit volume of air and your performance drops significantly.To counter this, one of the tricks we used to use during my drag racing days was to get dry ice and pack the carburetor and intake manifold between runs. This cooled things down enough to drop a few tenths off my times. With a composite manifold like the one used on the 4.7, this isn’t necessary because very little heat is conducted through the system and the intake charge stays nice and cool. Add to that the fact that the composite manifold weighs about 20 lbs less than an equivalently sized cast unit, and you’ve got a real winner.
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| Composite intake manifold removed.
photo by: Martin Ahlers |
Here you see the engine minus the throttle body, intake manifold, coils, injectors, and fuel rail. Removing this stuff is a complete no-brainer, except you’ve got to make sure you clean everything REALLY well. It is all too easy to have gunk fall into the engine once you’ve removed things. I found the injectors to be especially prone to allowing chunks of undesirable nasties to fall directly into the intake ports. The injector ports are very tight, and it is hard to get all the junk out of them while the injectors and rail are still in place. Take my advice – definitely use plenty of compressed air and patience and blast all the garbage away before you remove these components.It will save you lots of grief later on. Also, be sure to stuff all the injector holes with clean cloth and tape over the intake ports once everything is removed!!
Here’s a really interesting thing that I found when I removed the throttle body from the intake manifold: the joining surface between the back of the throttle body and the intake manifold wasn’t properly seated and sealed from the factory. In fact, the seal was so bad that I could see a well-defined path of dirt and grime going straight into the intake manifold. This was rather worrisome because I figure my car wasn’t the only one to have this problem. Left unchecked, the life of an engine that ingests a constant flow of dirt and grime like this will be guaranteed to be sub-50,000. Again, take my advice – have it checked. In the case of mine, I think the surface on the intake manifold where the throttle body attaches was warped and/or the throttle body was not correctly torqued down.
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| Underside of supercharger.
photo by: Martin Ahlers |
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| Polished supercharger and parts.
photo by: Martin Ahlers |
Here are some pictures of the supercharger from top and bottom. It really is a sweet unit – very well put together and finished. I opted to go to polished route (which adds about $500 to the price) at the last minute. The standard black satin finish looks great, but I had an opportunity to pick up a system on the spot and I couldn’t pass it up. Had I waited for another system to be built, I’d probably still be waiting because Kenne Bell is back ordered due to some supplier delays.
Note the extra two fuel injectors on the back of the unit – that’s one of the ways Kenne Bell deals with the increased need for fuel delivery during maximum boost. They also include a “Boost a Pump” unit that, from what I understand, cranks up the voltage going to your stock fuel pump during high-load conditions. This, in turn, increases the pressure coming from the pump and thereby allows a higher volume of fuel to be delivered. Fortunately, the “Boost a Pump” only kicks in during high-load conditions, so you won’t have to burn out your fuel pump unnecessarily early. Also note the trick bypass system that Kenne Bell engineered on these units. You can see the blue silicone hose and polished valves on the bottom area of the supercharger photo. Since the supercharger is generating full boost (about 7 psi) at 2000 RPM, it is necessary to bleed off this boost until it is needed. I’ve found the system works great – I can be running light on the throttle at 2000 RPM with about 15 in. Hg of vacuum, stomp on the gas, and have an immediate 7psi of boost. It really is a kick.
On the photo that shows the bottom of the supercharger, note that the stock blue silicone intake manifold gaskets are re-used. If you’ve ever wrestled with getting your intake manifold gasket to line up right, you’ll love the way these work. You just press them in and they stay right where you want them to go.
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| The stock fuel rail moved to the rear of the engine.
photo by: Martin Ahlers |
Since the supercharger drive will now take up the front part of the top of the engine, some re-routing of the fuel-rail is necessary. The stock configuration has the cross-over pipe going over the front of the intake manifold. Now, it needs to be in the back of the supercharger and, thank God, the stock fuel-rail is easily reversed without any need to modify anything. Just rotate it around, pop the injectors in, and you’re set.
You might not be able to easily see this, but take a look at the bolt sticking up immediately behind the right rearmost intake port. In the photo, it is partially obscured by the black wiring harness conduit. Kenne Bell says to leave 0.9875” clearance between the cylinder head and the bolt head. Make sure you’ve got that one right!! Once you install the supercharger, it is an absolute nightmare to tighten this bolt down. Unless you’ve got the spacing right, expect to spend at least an hour or so scraping your knuckles and cramping every joint in your hand trying to tighten the bolt with a small box wrench. I found the only thing that would get in there was the shortest available 10 mm ratcheting box-end wrench available. I still don’t think I got the bolt torqued down correctly, so I’m constantly expecting it to work its way out and cause a big vacuum leak.
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| Auxilliary injectors and brass fitting.
photo by: Martin Ahlers |
One thing I learned really quick was that it is impossible to tighten the auxiliary fuel supply line once the supercharger is in place. In this photo, note that there is a fuel supply line that connects to the auxiliary injectors on the back of the supercharger. It is necessary to slide the supercharger forward, and carefully tighten the fuel supply line without breaking the brass fitting. This is a careful tradeoff between tightening it enough and breaking something! Since you’ll have to remove the supercharger if there are any leaks, you want to make sure the fitting is on REAL GOOD. But, as many out there have experienced in the past, brass fittings can break easily – so be careful. It would have been nice to be able to pressure test the connection at this point, but it’s impossible because of the other things that are disconnected and/or not installed yet. This one will cause the installer plenty of worry – but if it’s done right it will turn out OK. Also, on this note, make sure the injector power leads are completely on, too. It won’t do much good to have the injectors going without power (and it might just cause your engine to grenade because of the lean condition experienced during boost).
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| Supercharger unit ready for final placement.
photo by: Martin Ahlers |
Here’s a picture of the supercharger sitting on the intake manifold, but pushed forward about four inches to allow access to the auxiliary fuel supply. The unit is resting on the fan shroud, and you can see a glimpse of the excellent Kenne Bell installation manual wedged between the supercharger and the shroud. Also, you can see the electrical leads to the auxiliary fuel injectors – it was pretty important to not let these things get lost down the back of the engine compartment while setting the supercharger in place.
Introduction The
Grunt Work After the Grunt Work
Conclusion & Impressions
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