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This article was first published in 2005.
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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.
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?
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.
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!
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
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