most tuneable sleeper cars

There’s something very satisfying about driving a ‘regular’ car that can leave more exotic machinery for dead. The generic terms are sleeper, Q-car or wolf in sheep’s clothing, but there are actually several different levels of sleeper. From cars that look pretty rubbish, but are very fast, to good looking performance cars that have much more grunt than your average Ferrari driver would expect, they all share one thing in common – lots of potential power!

We’ve put together eight of our favourite sleepers in terms of their tuning potential and how far under the radar they go. As with all sleepers, the main focus is in having fun and not taking life too seriously, something which should be applauded in our book. Also bear in mind these are only guide categories; there’s nothing to say you can’t combine a couple to create your own sleeper. Read on to be inspired…

SLEEPER RANKING

Level 1 – The boggo version
This is the ultimate wolf in sheep’s clothing, a totally standard looking base model car with a big engine. Tricks include fitting lower spec bumpers, painting brake calipers and intercoolers black, and hiding exhausts under the car.

Level 2 – The performance model
The next level is a car that’s obviously a performance model, but you wouldn’t expect it to be as fast as it is. So it still looks cool as standard, but not over the top. For example the Fiat Coupe Turbo – most people will know it’s the quick version, but nobody would expect it to be a 500bhp+ monster.

Level 3 – The unknown
These are the oddballs that most people don’t know anything about. Cars like the Mitsubishi RVR are so far under the radar, even people into cars will struggle to get their head around them. You can do pretty much whatever you want to it, but most people won’t take it seriously – until you leave them for dead that is!

Level 4 – The fake
These are cars deliberately done up to look like they’ve been badly modified, but underneath, they’re actually very well tuned. The thinking here is that drivers of posh cars will look down on them, then get a hell of a shock when they try and out accelerate them. Most fun at track days with lots of exotic machinery to embarrass!

most tuneable sleeper cars

BMW 335d saloon

Standard power & torque 282bhp & 428 lb/ft
Potential power & torque Over 350bhp & 550 lb/ft

The car that changed people’s perceptions of diesel performance, the 335d is a monstrous car straight out the factory thanks to almost 430 lb/ft. But when a simple remap can push it to 350bhp and over 530 lb/ft, giving it M3-beating performance, you can see why it had to feature here.

The reputation of the turbocharged 335 BMWs in both petrol and diesel form is already pretty high, so a 335d coupe with the optional M Sport bodywork is not a sleeper. You need a plain saloon version, maybe even with 320d badges.

Unfortunately as yet there isn’t much off-the shelf tuning available for the 335d, beyond an exhaust system and a remap. But we suspect things like uprated intercoolers and induction setups will be coming soon and give equally huge gains. If diesel tuning takes off as much as it has in the USA, then 335ds sporting massive turbos and serious grunt may soon be seen. Maybe you can be the first?

PROS: Seriously rapid fast with just a remap; has the chassis and suspension to cope with big power increases too.

CONS:
Beyond the remap not much is available, yet! Coupe or M-styled versions are too nice looking to be considered as true sleepers.

most tuneable sleeper cars

Mitsubishi Galant/Legnum VR4

Standard power & torque 276bhp & 271 lb/ft
Potential power & torque Over 600bhp & 500 lb/ft

As Japanese performance cars go, the Galant/ Legnum VR4 is pretty overlooked, despite ticking all the boxes of what many people look for in a performance car; a 2.5ltr twin turbo engine, four wheel drive, and a manual gearbox. Although this lack of popularity means there are relatively few tuning parts available, it does make them a fantastic base for a sleeper, as long as you don’t mind getting custom parts made or sourcing parts from abroad.

The engine is related to the 3ltr V6 seen in the 3000 GT Coupe, and that engine has been pushed to around 1000bhp inJapan. There are reports that 500bhp can be achieved from this 2.5ltr version on standard internals and well over 600bhp with the correct upgrades.

No need to de badge the car either, 99 percent of drivers have no idea what a VR4 is. They certainly wouldn’t expect one to be tuned to such big power, so you are free to create a great looking car that’s still a sleeper.

PROS: Twin turbo V6 and 4WD. Big power potential, even with overt styling it will remain a sleeper due to being so unknown in theUK.

CONS:
  Not many off-the shelf tuning options limit you unless you like putting in the effort. Fairly hard to find for sale in theUK.

most tuneable sleeper cars

Audi A6 2.7T

Standard power & torque 227bhp & 229 lb/ft
Potential power & torque Over 800bhp & 600 lb/ft

B5 Audi S4s have such a fearsome reputation these days that most people are now aware that they’re fast, despite them only being as powerful as many newer hot hatches as standard.

The performance potential of tuned S4s is absolutely massive though, and as the A6 2.7T has the same basic engine and transmission, but in a far less obvious bodyshell you have the same performance potential but in a true sleeper style.

You have two options when it comes to the looks, leave the 2.7T badges on it, which would still make quite a good sleeper due to no S or RS badge. Or, for the full sleeper look, de-badge it or put 1.9 TDI badges on it as 99% of people wouldn’t be able to tell the difference.

Most RS4/RS6 parts simply bolt straight on which means easy big brake conversions for example, and 550bhp of RS6-beating power from this ordinary A6 can be just a few engine and turbo upgrades away.

PROS: A de-tuned Audi S4 in a plain looking body. Parts from S4s and RS4s make for easy bolt-on upgrades. 800bhp+ tuning potential.

CONS: High S4/RS4 tuning and repair costs. Many have done high miles and been used as tow vehicles. Not great round bends either.

most tuneable sleeper cars

Seat Ibiza TDI Sport

Standard power & torque 127bhp & 229 lb/ft
Potential power & torque Over 800bhp & 600 lb/ft

Many people know about the Skoda Fabia VRS being a capable performance diesel, but did you know the Ibiza TDI Sport has basically the same running gear? It also boasts less weight, less cost, and much more of a sleeper appearance.

Even running standard engine internals and injectors it’s possible to get around 450 lb/ft of torque from these cars, which is plenty in a small hatchback! There are some issues with giving these cars such huge levels of torque (mostly related to destroying engine mounts and clutches!).

But it’s a small price to pay to turn what looks like a shopping car into a diesel powered Evo slayer. The common 1.9 TDI PD130 VAG engine means tuning options are wide spread and well proven.

PROS: A Fabia VRS in a lighter body. Hugely tuneable. Cheap to run and insure. Sporty performance combined with subtle looks.

CONS:
Potential reliability issues when highly tuned. Clouds of black exhaust smoke is not for everyone. Relatively basic.

most tuneable sleeper cars

Mitsubishi RVR

Standard power & torque 230bhp & 225 lb/ft
Potential power & torque Over 1000bhp & 700 lb/ft

We expect many of you are thinking “WTF?” right now, but yes, the Mitsubishi RVR, or Spacewagon as it’s often known, is available with what is basically a de-tuned Lancer Evo engine and 4WD system!

The upshot of this is that you can potentially run 9sec quarters in something with seven seats and a sliding door! There are versions from the mid ‘90s to mid 2000s with Evo running gear, but the earlier ones are cheaper, lighter, and even more comedy looking, so we prefer these.

The main downside is it’s far from easy to find one, but if you do, its relatively plain sailing as the fundamental parts are the same as an Evo.

It doesn’t matter how cool you try to make it look either, you could add bodykits, wheels, big brakes, anything you like, and still nobody would expect this obscure people carrier to be fast!

PROS: The most unexpected big power car ever. Evo engine and running gear makes for almost unlimited potential. Good wheelchair access, too.

CONS: Not easy to find a manual turbocharged version as, understandably, most are boring diesels used on the school run.

most tuneable sleeper cars

Fiat Coupe Turbo 16V

Standard power & torque 190bhp & 210 lb/ft Potential power & torque Over 500bhp & 500 lb/ft

Despite looking the most sporty car in this feature, due to the lack of a tuning scene around these cars in the UK, nobody expects a Fiat Coupe to be a supercar slayer. But it can be when tuned. The 20V Turbo may be the top model, but the turbocharged 16V lump is the one to go for in our opinion.

The reason for this is it has the same basic engine used in the awesome Lancia Delta Integrale Evo, so the tuning route is well proven. It also has P8 engine management that was used on the Lancias and Escort Cosworths, which can run at huge power levels and have additions like rally-style anti-lag systems.

Fiat build quality is not fantastic, their placement of items can be a bit odd and the car can be a bit of a pain to work on, but with upgraded brakes, suspension, and LSD you have a fine base for a serious weapon. Not bad for a car that many will write-off as an old, girly looking Fiat…

PROS: Fantastically tuneable engine and management. Integrale engine means well proven tuning paths to achieve very high power levels.

CONS: Fiat build quality is highly suspect. Engine bay can be a pain to work on due to layout. Lancia engine means tuning parts can be pricey.

most tuneable sleeper cars

Skoda Octavia 1.8T 4×4 Estate

Standard power & torque 150bhp & 155 lb/ft
Potential power & torque Over 500bhp & 500 lb/ft

You could argue that the Octavia VRS is a sleeper, but there’s actually a better base for a sleeper in the Skoda range, the obscure 1.8T 4WD estate models. Looking plain and sitting on very high standard suspension, they pack 150bhp as standard and come with the same Haldex 4wWD system as many VAG vehicles.

Combine that with the famously tuneable 1.8T lump and you have a great base for a sleeper. The standard engine and turbo can be pushed to around 250bhp, which in itself is enough to surprise a lot of cars, but once you add a bigger turbo and uprated engine internals 450bhp can be had with ease and reliability.

You can go well over 600bhp if you’re feeling particularly crazy. Being a VAG car, upgraded suspension and brakes are very easy to get hold of too, making it a fairly easy sleeper to build. Best of all, these have usually had a much easier life than the VRS versions, making them a safer base for tuning.

PROS: Would fool most tuned car fans. Likely to have had a much easier life than the VRS model Skodas. Great engine and 4WD system.

CONS: Never sold well so not easy to find. Any exterior upgrades will make people think it is a VRS, instantly making it far less of a sleeper.

most tuneable sleeper cars

Bora V6 4Motion

Standard power & torque before 204bhp & 199 lb/ft Potential power & torque Over 600bhp & 600 lb/ft

Maybe the last VW you’d think of when it comes to tuning, the Bora V6 4Motion is the base for our awesome cover car, and even without the R32 engine swap, this car has enormous potential. Despite looking totally unremarkable, it has the usual VW Golf Mk4 underpinnings, meaning it’s a sound base for upgrades with no major weak points.

The VAG V6 lumps sound great and are torquey, but power-wise they are fairly unremarkable; until you turbo them that is! The V6 in the Bora is the later 24V version of the well known VR6 engine, and can be boosted to huge power levels with ease, arguably cheaper and more reliably than the famous 1.8T lump.

The 4WD system is very strong, staying quite reliable even at over 500bhp, and helps put the power down in all conditions, which is just the icing on the cake really. And as sleepers go, this is potentially one of the best all-round bases you could start with.

PROS: Strong engine and 4WD system. Great engine noise when tuned. No high performance model in its range. 800bhp+ potential.

CONS: Normally aspirated tuning gives small gains, it needs turbocharging to be truly fast. Heavier than its closest relation, the VW Golf.