This chapter discusses peripheral modifications that are commonly performed to support them, including fuel system upgrades, spark plug selection and the process known as “pinning” the crankshaft and balancer. For the most part, the factory cooling system on LS-powered vehicles is sufficient to support bolt-on power adders. In fact, at low speeds and part-throttle conditions, the cooling needs of the engine are no greater than normal.
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Body and Chassis Component Removal
Systems that incorporate a charge-cooling system, typically a liquid-to-air or air-to-air system, require the installation of a radiator-style heat exchanger. It is generally mounted at the front of the vehicle to ingest air via the grille/fascia assembly, either straight through the grille or from beneath the fascia. In most cases this requires removal of the fascia, bumper cover, grille, and sometimes even the headlamps.
Although the attachment of the body/chassis components may seem obvious, read the kit instructions carefully and proceed cautiously. The plastic body parts and fasteners that typically comprise the components to be removed aren’t designed for repeated installation and removal; and the fasteners can be especially fragile.
A kit with good instructions points out all of the fasteners that require removal; and even after they’re removed, there will likely be press-kit/snap-fit attachments, particularly with the bumper cover. When it’s clear that all other fasteners are removed, a firm tug on the fascia usually pulls it free from the chassis.
There are inexpensive specialized tools that enable the removal of the factory fasteners quickly and without damaging them. Buying one is a wise investment before starting the installation project. Overpriced replacement clips/fasteners are always available at the dealer in case you damage one.
Before touching the engine or any of the vehicle’s mechanical components, the power must be disconnected by removing the battery cable from the negative terminal. Most intercooled supercharger and turbocharger systems also require the draining of the engine coolant. The coolant can be reused if it is captured in a clean, contaminant-free receptacle.
Study the manufacturer’s assembly manual prior to starting the project. This helps identify special tools or other necessities that need to be addressed—items that would inconveniently interrupt the installation process, because they’re not in your toolbox. One of the more uncommon tools that may be required is a torque wrench with angle measures, as most of the factory fasteners on LS engines are torque-to-yield types that are final-torqued to a specific angle rather than a conventional ft-lbs measure (see page 106 for more information).
The addition of a blower or turbo system most likely comes with higher-capacity fuel injectors, which requires removal of the fuel rail to swap the injectors. Before that can be accomplished, the pressure in the fuel rails must be relieved in order to prevent fuel spraying on the installer and the vehicle when the fuel line is disconnected.
If the vehicle has sat for a long period without starting, such as overnight, the pressure at the fuel rail shouldn’t be great, but the relief procedure should still be followed for maximum safety—and it should be accomplished with eye protection. The procedure is simple. Follow these steps:
- Make sure the engine is off; the ignition key is in the off position or removed; and the negative battery cable is disconnected.
- Remove the black cap from the front end of the driver’s-side fuel rail, exposing the Schrader valve that is also used as a fuel-pressure test port.
- Place a rag under the port to capture and soak up any fuel that may leak or blow out.
- With the tip of a flat-blade screwdriver, gently and quickly press on the valve just to gauge pressure in the fuel rails.
- Hold the screwdriver tip against the valve as necessary (similar to releasing air from a tire valve) until the pressure is eliminated.
- With the pressure relieved, the valve cap can be reinstalled and the fuel rail/injector assembly removed.
Oil Pan/Oil System Modifications
Some superchargers, such as centrifugals and Vortech blowers, have external lubrication systems, being lubricated with oil circulated from the engine. This requires feed and return lines between the compressor and the engine. The feed line is usually routed from an unused port on the cylinder block, but connecting the return line to the engine requires drilling and tapping a hole in the oil pan.
When performed correctly, the oil pan modification is a leak-free, maintenance-free change, but it permanently alters the oil pan (even if the supercharger is removed at a future time). For some enthusiasts, the thought of drilling into the oil pan is enough to dissuade them from a particular system. If that includes you, check with the retailer or blower kit manufacturer about the compressor’s lubrication.
“Pinning” the Crankshaft
The crankshaft damper/pulley on almost all production LS engines is a press-fit type, meaning it is pressed onto the front hub of the crankshaft and does not have the complementing locking feature of a traditional keyway on the hub. A large, 24-mm bolt secures the damper to the crankshaft after it is pressed into place, but there are no fasteners between the rear face of the damper and front edge of the crankshaft.
Although in stock and even mildly modified combinations, this isn’t a problem, but there is a chance the damper could slip or spin on the crankshaft in higher-power engines, particularly supercharged and turbocharged applications that see a quick spin-up of the engine speed. A slipping damper can cause a number of problems, including altered ignition timing.
A relatively simple method of guarding against unwanted slippage is “pinning” the damper to the crankshaft. It involves drilling a small hole through the face of the damper that interfaces with the crankshaft hub and a complementing hole into the end of the crank hub. This is performed carefully after the damper is pressed onto the crankshaft.
After the holes are drilled, one or two dowel-type pins is inserted, providing a slip-free link between the crank and damper. The standard damper bolt is fastened, too. When this modification is performed correctly, the pinned crankshaft and damper are locked together, regardless of the amount of power (or boost) the engine produces.
The pinning procedure is easily accomplished in the vehicle, but depending on the model, it may be necessary to remove the cooling fan assembly and possibly the radiator in order to provide enough room to insert the drill at the proper angle. On C5 and C6 Corvettes, the process requires the removal of the steering rack for maximum clearance and an unobstructed angle (reinstallation of the rack requires suspension alignment after the project is completed).
It may be very difficult to initially break loose the 24-mm bolt, requiring the added leverage of a breaker bar or something similar. When attempting to remove the bolt, it is imperative to prevent the crankshaft from turning. On a manual transmission vehicle, the transmission is placed in fourth gear to prevent movement, while an automatic-equipped vehicle needs a tool to positively hold the flexplate; specialized tools are available for this.
The additional air delivered by the blower or turbo must be accompanied by a corresponding increase of fuel in order to make power. And it’s not just the quantity of the additional fuel that’s important, it’s the sustained pressure at which it’s delivered.
vehicles using a bolt-on power adder kit and no other internal engine modifications, higher-capacity fuel injectors may suffice; and they should be included with most kits. When larger injectors alone aren’t enough, higher-capacity fuel pump(s) and/or a fuel pump amplifier are required.
In most cases, swapping the fuel pump is a simple procedure that involves dropping the fuel tank to remove the stock pump and inserting the new one. While it’s true that it’s better to have more pump capacity than not enough, it’s also possible to have too much. Generally speaking, most supercharged/turbocharged LS engines need a pump rated at a minimum of 190 liters per hour (lph), which is the equivalent of 50 gallons per hour (gph) or 301 pounds per hour (lbs/hr). This suits an engine up to approximately 600 flywheel horsepower.
If the horsepower is expected to be between 600 and about 850, a 255-lph (67-gph/404-lbs/hr) pump should be used. Beyond that, a custom system is likely required that can include an inline “helper” pump. Australia-based turbo kit manufacturer APS offers a dual-fuel pump kit that fits a variety of LS vehicles and is rated for more than 1,000 hp.
The Kenne Bell Boost-A-Pump
For many LS-powered vehicles (mostly 2003 and later), an alternative to replacing the in-tank fuel pump (or complementing a replacement pump) is the addition of a Kenne Bell Boost-A-Pump. It works essentially like an amplifier for the electric in-tank pump, increasing the voltage by up to 17.5 volts when necessary. It also increases the voltage on demand, such as under boost conditions, and allows normal operation in low-speed, zero-boost conditions.
The principle of the Boost-APump is quite simple: Increase the voltage to the fuel pump to increase fuel flow. But along with increased fuel flow is the necessary requirement of sustained fuel pressure to ensure a safe air/fuel ratio. Because the electric, in-tank fuel pump is essentially an electric motor, the amount of voltage it receives determines its speed and output. The Boost-A-Pump’s increased voltage sustains fuel pressure as long as necessary. Generally, it increases voltage to the pump when boost exceeds 4.5 pounds.
The on-demand operation of the Boost-A-Pump has several advantages, such as not overloading the fuel system during low-speed, noboost conditions. The manufacturer claims it supports up to 1,000 hp when used in conjunction with the factory, in-tank fuel pump and can actually enhance the life of the stock pump. The system is adjustable, with a control knob that enables between 1- and 50-percent increase in voltage on demand.
If a supercharger or turbocharger kit does not include a Boost-A-Pump, you should consider adding one if fuel pressure fluctuates significantly at WOT.
Fuel injectors should be tailored to the engine’s general performance parameters. Like the fuel pump, a slightly larger injector is okay, but injectors too large can lead to low-speed drivability problems, as well as tuning problems. Injectors are typically “sized” in pounds-perhour measurements, such as 24 pounds, 36 pounds, etc., based on a general operating fuel-pressure rating of 43.5 psi for the LS-type portinjection system.
Determining the appropriate injector size for a modified engine, with a supercharger or turbocharger system, can be done with the following formula:
Horsepower x brake specific fuel consumption (BSFC) / the number of injectors x the duty cycle
BSFC is the amount of fuel an engine needs to make 1 hp for 1 hour. Generally speaking, that’s between .40- and .60-pound per hour, with forced-induction applications at the high end of the range. A .55 BSFC rate is used for the following calculations. The duty cycle is the approximate load on the engine. Most injector calculations use a duty cycle between 80 and 85 percent; a .85 duty cycle is cited in the following calculations.
Therefore, the equation for an estimated 500-hp (at the flywheel) engine with eight fuel injectors would look like this:
500 x .55 / 8 x .85 = 40.44
Rounding up to the nearest standard injector rating is 42 pounds per hour.
Larger injectors work in the application and if additional engine modifications are expected, installing 60-pound injectors or slightly larger injectors would be fine.
Generally speaking, 60-pound injectors are suitable for engines up to about 700 to 750 hp. After that, 72- to 83-pound injectors work up to about 900 hp. As power approaches 1,000 hp and beyond, even larger capacity injectors are required.
A Word About LS Injectors
From the factory, LS engines have used three injector types:
- LS1 and LS6 engines used tall injectors with a “Minitimer” type of harness connector
- LS2 and some other 6.0-liter engines used tall injectors with the newer-style “USCAR” harness connector
- LS3/LS7/L92 engines used a short injector with the USCAR connector.
The injector types are interchangeable among all engines, but those included with a blower or turbo kit may not match the engine’s wiring harness. If that is the case, adapter kits are available from F.A.S.T. They include jumper harnesses with a Minitimer connector on one end and a USCAR connector on the other.
IMPORTANT! Do not attempt to start an engine with upgraded fuel injectors until the engine-control computer has been flashed with new tuning data that includes the new injectors’ specifications. Doing so almost immediately fouls the spark plugs and could lead to other problems or engine damage. Start the engine only after new injector data has been programmed into the controller.
In almost every supercharger or turbocharger installation, the engine’s spark plugs should be replaced with those of a “colder” range and a tighter electrode gap. In fact, many bolt-on kits include a set of new plugs as part of their standard equipment.
There are two primary reasons for the new plugs: heat range and proper gap. The colder heat range of the plugs helps ward off the preignition and detonation conditions that are crucial to maximum performance and trouble-free drivability. Forced induction generates greater cylinder pressure and therefore more heat, and stock spark plugs that get overheated can glow like the glow plugs of a diesel engine. This promotes pre-ignition since the heat of a glowing plug tip lights off the incoming air/fuel charge before the piston reaches the top of its stroke.
The heat range is a rating of a spark plug’s capability of absorbing/removing heat from the combustion chamber. It is determined by design elements such as the plug’s center electrode material and insulator design, as well as the length of the ceramic center insulator nose. A longer insulator nose exposes more ceramic to the combustion gases to promote heat retention.
It’s important to remember that the heat range has nothing to do with the energy output or voltage transfer of the plug. Heat ranges are indicated on plugs with a numeral, such as 5, 6, or 7; the lower numbers indicate hotter heat ranges. For example, a plug with a heat range of 5 is hotter than one with a heat range of 6.
Most LS production engines use plugs with a heat range of 5 or lower, as heat retention is desired to warm up the engine more quickly. In turn, that helps the catalytic converter heat up quicker, in order to reduce cold-start emissions.
A heat range of at least 6 should be used on supercharged and turbocharged engines.
As for the importance of a tighter-than-stock electrode gap, it’s necessary to ensure a strong, consistent spark that won’t get blown out by the increased cylinder pressure that comes with supercharger/turbocharger boost. Think of it as attempting to light a match outdoors when there’s no wind (natural aspiration) versus when there’s a stiff breeze (supercharged/turbocharged).
The gap of stock plugs may be sufficient for low-boost, bolt-on kits used with few other modifications, but since it’s important to use replacement, colder-range plugs anyway, they should be gapped to suit the supercharger/turbocharger requirements. For most forced-induction applications, a gap of about .030 inch is optimal.
Real-World Project: Camshaft and Valvesprings Swap
Bolt-on supercharger and turbocharger kits can be complemented with a change to a camshaft that’s tailored to the airflow and performance potential of the power adder (see Chapter 9 for camshaft selection details). Because portions of the top and/or front of the engine require removal or disassembly to facilitate the blower/turbo kit installation, swapping the camshaft (and required stiffer, higher-rate valvesprings) is a way of knocking off two birds with the same stone.
The unique details of the LS engine allow the cam and springs to be easily changed without having to remove the cylinder heads. This is because the lifters can be “locked” with a simple full rotation of the camshaft to prevent them from falling into the cylinder block when the cam is removed.
A few unique tools are required for the procedure, mostly to support the valvesprings’ removal and installation. They include a compressed-air hose, with a threaded fitting on the end for the spark-plug holes in the cylinder heads, as well as a valvespring compressor/removal tool.
This project was performed at Detroit-area Stenod Performance on a TrailBlazer SS that was also receiving a Magna Charger Roots-type blower system.
Written by Barry Kluczyk and Posted with Permission of CarTechBooks