The Brodie Report

News Letter Spring 2005 - Page1 - Page2

Cooper S beware of BS! - A short note on Forced Induction tuning.
These low compression engines rely on the air being forced into the engine (boost pressure), hence turbo/supercharging. Both are extremely effective ways of achieving extra power over normally aspirated engines of the same capacity, without resorting to technically complicated engineering, high revs and loss of good idling and low end power.

So guys, if your looking for pure drivable 'grunt' turbo/supercharging is the way to go! Both systems are different in power delivery, but boy are they effective! At BBR we have been advocating forced induction for over twenty years.

Now guys, there is a whole load of BS being put out regarding the tuning of the Cooper S engine and its all aimed at confusing you! So here are a few very basic facts on the Cooper S supercharged motor:

1) The only way to hike the power of an originally equipped forced induction engine is to raise the boost pressure to increase the mass air flow through the engine, its as simple as that!

2) The air temperature in the inlet manifold is vitally important, when air is compressed its temperature increases dramatically! Basically the lower the inlet temp. the higher the power and reliability of the motor. An average temperature of 30 degrees C is ideal.

3) The efficient discharge of exhaust gases is essential.

4) As forced induction engines are prone to detonation (pinking) at high boost levels, it is vital to have an efficient supply of good quality fuel (97/98 octane fuel) delivered to the injectors.

5) Air/Fuel ratio and ignition timing is also critical.

Summary

In a nutshell, forced induction is all about controlling boost/fuelling, ignition timing and temperatures. 

The Cooper S engine and its restrictions? on raised boost applications

The truth is there are very few restrictions and the base motor is very robust. We know, as we have done our best to murder the engine on our dyno whilst developing the BBR 220-275BHP conversions.

If you had seen the savaging the Top Gear BBC tv presenters gave our 275 BHP and other modified Cooper S's, at a recent TV shoot at the top gear circuit you would understand. It was a sight to see, those guys don't mess around! But all the Cooper S's survived!

So guys we're in luck. We are starting with a strong motor, and bearing in mind the engine looks like it's from a get the kids to school/shopping Chrysler? It has few limitations for road tuning purposes, even the original cylinder head gasket is of excellent quality, but one limitation is definitely valve size! the inlets are 30mm; not too big but what the hell, it's forced induction. Turning to exhaust valve size its a different story! They are tiny by any standard at only 23mm and way to small for a high boost forced induction motor! But unexpectedly the exhaust manifold is fine, even when we open out the  ports and exhaust valve size the original manifold is up to the job! And guess what? The catalytic converters (cats) are too! Now there's a surprise!

So what a little gem the engine is, for our purposes (well chosen Rover!). Up to BBR level 5 the only internal component that needs attention is the cylinder head ports (inlet and exhaust) and exhaust valve size! The only external engine component we don't trust at sustained high revs is the original idler pulley, that's easy to rectify, we install a well (race) proven Cosworth idler that we modify to fit the Cooper S.

And a word of of warning, stay off power testing on rolling roads! No fan (other than a wind tunnel fan) has the ability to cool the air through the intercooler "put your hand out of a car window at 100MPH see if you can find a fan that has the same effect?" We have been advising our customers since the mid 80's (Cosworth days) to stay off power testing on rolling roads. They do more damage than you can believe, since it's impossible to keep the inlet charge temperature at a safe level! We have seen countless damaged engines all down to reckless power testing on the rolling roads! You have been warned!

So guy's and girls (we know of one racy Cooper S chick near Dundee!) there you have it, remember its our philosophy at BBR"if its OK, don't change it" look between all the BS guys, its your hard earned!

Note for Cooper S pre 2005 model owners with supercharger pulley reductions:
We have noticed without exception due to the extreme heat induced on so called "power runs" on rolling roads, Cooper S owners are over heating the coat applied to the rotors within their earlier type Eaton supercharger unit. This causes delaminating and flaking away of the Eaton rotor coating, a loss of efficiency within the supercharger (loss of seal) therefore reducing boost pressure and airflow! This will cause a loss in power, but more importantly the delaminated coating has nowhere to go other than into your intercooler (further restricting air flow!) or even worse with smaller parts straight through into your engine!

BBR do not recommend these rolling road "power runs" on forced induction engines (see Brodie Report), but we would like to warn and prevent our customers, and all other Cooper S owners from unnecessary damage to their supercharger units and potential long term damage to their engines! "You have been warned."