Mini Cooper S
, JCW and Works GP all use the same 1,598cc petrol engine with four valves per cylinder and an Eaton M45 supercharger. Each is also attached to a six-speed Getrag manual gearbox, though this was only offered with a limited-slip differential as an option on the S from 2005 onwards. The GP has a limited slip diff as standard equipment.
JCW's revised pulley created more boost
To upgrade from S to JCW spec, John Cooper's garage came up with a revised pulley for the supercharger to make it spin more quickly and create more boost. As well as this main change, the JCW kit also included a gas-flowed and ported head to optimise engine breathing, uprated spark plugs, a new freer flowing exhaust system and remapped ECU to take full advantage of the uprated set-up. Together, this lot increased power to 200hp at 6,000rpm compared to the standard early model's 163hp, which was later 170hp from the 2004 facelift of the R53.
In 2005, the JCW kit was further finessed to offer 210hp thanks to improved 380cc fuel injectors, better intake system and air filter, and another remap to suit the revisions. The 380cc injectors of this model are a popular retro modification to standard S models that have had new supercharger pulleys fitted in the search for more power. Any car for sale with a modified pulley, injectors, remap and exhaust should just about match a JCW for power and performance if there are not other changes.
Early cars had 163hp, later 170
limited edition Works GP
, again the supercharger pulley was the focus of attention to get more blow from the 'charger. There are also further revisions to the engine's air intake system, injectors, remapped ECU and a better intercooler to cope with increased engine power and temperatures. This results in 218hp at a heady 7,100rpm, 184lb ft of torque at 4,600rpm, 0-62mph in 6.5 seconds and 149mph top speed.
The six-speed manual gearbox from Getrag used in all of these variations is strong and reliable, though don't be surprised if reverse gear is a little awkward to select. This is a trait of this gearbox and not something to worry about.
There are far more concerns with the engine, which can suffer from cracked cylinder heads if it's allowed to overheat. As there's no temperature gauge on the dash, this can happen more easily than you might think if the main cooling fan's thermostat fails and stops the fan from cutting in. A reconditioned head will cost from around £250, rising to £450 for a JCW item.
Private plate not mandatory!
All of these engines tend to use a little oil, so reckon on around 250ml every 1000 miles as normal. If the engine has been allowed to run dry on oil, it can spell the end for the main bearing, so listen out for rumbling at the bottom end of the engine. Look for signs of leaks from the sump and oil filter surround to confirm this and, if there are leaks, walk away as there plenty of other cars for sale.
The hydraulic tappets of the S engine can become noisy and rattly, so keep an ear out for this. This noise could also be the timing chain tensioner, which is solved by tightening the tension.
As for the supercharger, it's a tough unit that doesn't give much trouble, but a rebuild may well be on the cards for any car that has covered 100,000 miles or more. Superchargers that have been fitted with uprated pulleys will be more susceptible to this.
Mini's TLC service packs lasted for five years and 50,000 miles or eight years and 80,000 miles. As 98 per cent of new Mini customers opted for this service deal that included oil, inspection and brake fluid servicing, there's no excuse for an R53 Mini not to have a full service record.
PHer's view:
I loved the Mini, and I still miss it on those warm, dry Sunday mornings when I'm driving down country B-roads. It's a great car to own and miles of fun, but for me it's a weekend toy and not a daily driver.
James Ford