Fitting a Supercharger, Part 1

This article was first published in 2005.

With cheap superchargers available from Japanese-importing wreckers, there’s now a viable option to turbos. And the advantages of a supercharger over a turbo? Well, there’s no need for a new exhaust manifold, you don’t have to adapt the exhaust system to the turbine outlet, and in most cases there’s no requirement to tap into the engine’s coolant or oil galleries. Sounds easy, huh? Just bolt up a few brackets, attach the belt and some intake plumbing, and away you go. Blower power!

Well, not quite.

In reality, installing a blower as a one-off exercise is still plenty of work – but it’s also the sort of thing you can do with just normal home workshop tools, sending-out just a few jobs like welding or plate cutting. We know, cos we just did it.

So what exactly is involved?

Blower Type

Superchargers – either centrifugal or positive displacement – come in two basic physical packages. There are those that have inlet and outlet plumbing that’s designed to attach to hoses, and those that have an outlet designed to flow straight into an intake manifold. The latter usually have a long, narrow outlet.

Second-hand examples of the ‘plumbed-in’ types include the very popular Toyota blowers from the 4A-GZE four cylinder and the 1G-GTE six cylinder engines, and the superchargers from the Subaru Vivio and the Nissan MA09 (the latter an engine that is both supercharged and turbocharged!). Most aftermarket centrifugal blowers – eg Vortech - are also of the plumbed-in type.

Examples of the superchargers that are designed to bolt straight to an intake manifold (or plenum) include the Eaton and Whipple blowers. These are used in both aftermarket and OE applications.

So the first decision about mounting needs to take into account the type of blower you’re working with. If the supercharger mounts directly on the intake manifold, the manifold itself usually supports it – just as an exhaust manifold supports a turbo. But if it’s a ‘plumbed-in’ blower you’re dealing with, the story becomes more complex. In this series we’ll concentrate on the plumbed-in design, which is much more popular at wreckers.

Blower Mount Planning

Nothing is surer than death and taxes than the shrinking that occurs of your engine bay in the time between spotting the blower at the wreckers and taking it home to install it. Even if you’ve measured everything first, the space you thought you had seems to lose inches everywhere. It’s therefore wise when buying a secondhand blower to suggest to the seller that you may want to return the blower (in as-bought condition, of course) if you get it home and it proves impossible to fit.

So, you have the blower clutched in your hands and you’re pondering just where under the bonnet to put it. It’s very, very important that you don’t just look for physical room for the blower body but also consider the following points.

• Drive

If the blower is to be driven from an existing accessory belt (a common approach with smaller blowers), can it be placed so that its drive pulley lines up exactly with the main crankshaft drive pulley? If the answer is ‘yes’, is there free space for the belt to reach the blower pulley – and then return to the drive system? Will the belt still have adequate clearances if you need to fit a larger or smaller supercharger pulley? Is there a belt available which is the right length?

• Orientation

Most superchargers have an ‘up’ direction. This can be indicated by the presence of a dipstick (which may be in the form of a graduated bolt), filler hole (again it may be plugged with a bolt), or other obvious mark. As much as possible, you should keep the blower orientation matching this direction.

• Plumbing

Is there room to get the intake air to the blower and boosted air away from the blower? Note that in many cases, the existing supercharger plumbing connections can be unbolted and new ones made to better suit the geography of the new engine bay. When considering the plumbing clearances, also start thinking through various blower mounting schemes – after supporting brackets are installed, all your plumbing space can soon disappear!

• Brackets

We’ll devote a whole section to the topic of brackets but at this initial planning stage it’s important to start looking for existing super heavy duty bolts to which you‘ll be able to attach the blower mounts. We’re talking engine mount bolts, alternator mounting bolts, power steering pump bolts – big bolts that disappear into heavy duty parts of the engine like the block and the head. They also need to be near and accessible.

Designing Brackets

So you’ve found a spot where there’s room for the blower and its input and output plumbing, the blower is near-vertical and the drive pulley lines up with the existing accessory drive. Great! Now comes the fun bit – making brackets to hold the blower in place.

A supercharger needs to be mounted rigidly. This is the case primarily because of the loads placed on it by the belt drive. First up, there’s the power that the belt is transmitting, which is trying to twist the blower off its mounts. Then there’s the belt tension, which is trying to draw the blower closer to the drive pulley. Finally, there are the usual loads caused by anything heavy being bounced around in the engine bay as the car passes over bumps.

Most OE belt-driven accessories - like the alternator and power steering pump - are mounted very close to the engine on short brackets. This gives a more compact engine package but just as more importantly, it also allows the use of rigid brackets. When you’re trying to install a blower in an engine bay, it’s likely that all these up-close-and-tight positions near to the engine have already been taken. As a result, you’ll probably find that the blower has to be mounted quite a long way from the block or head, necessitating much longer brackets than used for any of the other belt-driven items. Making matters worse, it’s likely that the power being absorbed by the blower is higher than for any other belt-driven devices already present, so requiring lots of belt tension. Which tries to bend brackets even more...

Another important aspect to keep in mind when thinking through mounts is there needs to be a way of adjusting belt tension. It may be that the existing belt tension adjustment system can be retained when the blower is fitted. For example, perhaps there’s an idler pulley on the ‘slack’ side of the belt that is moved laterally to increase or decrease belt tension. Or perhaps there’s a sprung tensioner pulley. However, sometimes this adjustment mechanism needs to be removed to make way for the blower. If that’s the case, the blower mounts will need to incorporate a means of setting belt tension, for example by the use of a slotted bracket like that used on alternators.

As you can see, the mounting of a blower is a little more difficult than it first appears...

Checklist

When considering the installation of a blower, here are some key questions to answer:

• Is there physical space in the engine bay for the blower?
• Can the blower be positioned so that its pulley lines up with existing belt drives?
• How will belt tension be adjusted?
• Is there room for inlet and outlet plumbing connections to the blower?
• Are there existing heavy duty bolts that can be used to hold the blower mounts in position?

Think through the answers to those questions and you’ll be much better placed to make a good decision.

Next week: mounting a supercharger