Right chaps this isn't really a guide as such, its a complete spec list of what I've found works well on a clio. I've had tons of PM's over the last couple of years regarding Turbo clios but have always kept my true spec quite quiet, anyway here goes.
I took my completely standard Trophy lump and did little more than fit a set of CatCam rods, a set of Wossner pistons and a set of megane R26 OE spark plugs
It's well documented on here that after destroying my OE box I swapped to a JC5-128 DCi box. I found it a great set up for a genuine 300+bhp clio on both road and track, AndyRG tried one when his clio was around 270bhp and hated it. Based on this I'd stick with an OE box sub 300 bhp.
I stuck with the OE fly wheel but ran a Helix paddle clutch. I'm not going to lie it was horrible, there was very little pedal travel from fully disengaged to fully engaged which resulted in everyone who ever drove it stalling it repeatedly. I would also say the longetivity of them wasn't overly impressive so it's something to bare in mind. It does work though and I didn't experience any slip or issues on either road or track
I used a Forge type 7 200 series universal intercooler it was the largest unit I could squeeze under the front cross member but I did have to remove the small plastic undertray that runs from the front bumper to the subframe.
Pipework wise was a bit of a ball ache, there wasn't anything available off the shelf at the time and I wanted 2.5" pipework, so I bought a stainless universal kit off ebay and set about painstakingly cutting each bit to the correct length before ordering the suitable silicone hose. Since then Ktec have a kit off the shelf and personally I'd save yourself the headache and just buy that or pay for a custom hand made set up.
Ktec turbo down pipe, turbo link pipe running into an ultra performance single box de-cat'd exhaust. It was basically 2.5" from the turbo back with only the single back box causing and restriction. Again it worked really well and was suprisinglt quiet. Other options would be to get a custom turbo back exhaust with a flexi joint.
This is the area which gives the biigest problem but has the benefit of shaping both the overall power and also the characteristics of your power band. It's pretty straight forward, the bigger the turbo you choose the more power you'll make for a given boost pressure, the trade off is it'll spool later and you'll lose out in the lower rev range. Because of this you need to be honest about what sort of power your aiming for, it's no good fitting a 600bhp monster turbo but the rest of your set up only capable of flowing/supporting 350bhp.
I ran 3 turbos during my tinkering.
First off was Ktecs own GT28 I found it extremely restrictive (I had a 2.25" exhaust and the stock cat which won't of helped) and it gave a very aggressive spool up due to running high boost (22psi) to try and make good power. The result was 267bhp. One thing which was a problem was the ECU but I'll cover that later.
The second turbo I used was a GT2860R it was basically a GT28RS but with a more compact GT28 compressor housing (two bolt inlet and three bolt outlet shown at the bottom of the link) this is by far the best turbo I used. I ran 341bhp @ 1bar (14.7psi) of boost. It gave a really responsive but smooth power delivery and best of all when running only actuator pressure (7 psi) it made 280bhp. It also allowed the use of the larger T3 style actuator which in it's self helped to eleiminate some of the boost problems I experienced with the T2 actuator found on ktecs turbo.
The third turbo I used was a GT2871R again I chose the compact GT28 housing. This was a bit of a disappointment. I'd heard so many good reports from them being fitted to 200sx's so assumed it would blow me away. The reality was it spooled later and slower due to the larger compressor wheel and made the power delivery more aggressive than the GT2860R with 1.2bar of boost it made 374bhp.
The truth is your limited to a T25 flanged turbo, also the amount of space means that you need to sacrifice a larger free flowing compressor housing for a smaller more compact GT28 housing or you can cut a big hole in the bulk head.
Manifold wise you can get them from ED or Ktec there both the same so the choice is yours lol
Initially I tried using the OE ECU and a boost controller but it was obvious from the outset that it wasn't suitable so I swapped it out to the EC1 supplied by RStuning. This is probably the key to making a real usable FWD turbo car, whilst using the OE ECU and a boost controller no matter what throttle was being applied the boost controller was always aiming for full boost. This meant that steady throttle or small throttle openings were met with quite a jerky response. By using an aftermarket ECU and giving it full control of the boost, it was possible to have a Boost Vs TPS map. This meant that whilst on 50% throttle I only got 50% boost. It provided exceptional throttle response and almost eliminated traction issues.
When doing it I wouldn't scrimp on sensors, I had a chinese copy of a MAP sensor start giving false readings to my ECU causing the car to run stupidly lean, luckily I have a data logging and monitoring system so spotted the high EGT and AFR's, be warned!
Uprated engine mounts
Uprated Coolant Hoses - they have a convienient join near the heater matrix where you can run a water feed through the turbo to aid cooliing
Data logger/monitor - allows you to keep an eye on essentials whilst enjoying yourself EGT's, Boost, AFR's, AT etc.....
Brakes - I run a JamSport set of Willwoods with DS2500 pads and HC discs. Great bit of kit and fit under 15" wheels
70mm Jenvey throttle Body
Heat protection - the turbo sits very close to the brake lines and the dwn pipe is close to the PAS so it's vital to have some high quality heat protection on the bulk head and rack. I used nimbus sheets and also had my turbo manifold, turbo and downpipes ceramic coated.
PROBLEMS I ENCOUNTERED AND ADVICE
Gearbox problems - if you build a 370bhp clio turbo your gearbox will break if you use it with intent. I destroyed my OE box (literally destroyed), my DCi box spat the circlip out at 341bhp and with a new one welded in it was spot on. However when I moved to 374bhp and the more aggressive power delivery it wasn't long before 4th gear stripped I'd suggest a reconditioned box to aid longetivity probably with some strengthening mods.
Clutch - as above if your horsing it about your clutch will last less than 10k miles, if you use it on the drag strip expect signifuicantly less
Mapping costs - mapping costs a bomb, try and get it right first time rather than making small changes and needing multiple maps
Consumables - Oil's, gaskets etc.... soon amount up to a pretty penny so take your time and nail your engine build from the off theres nothing worse than having to drop £70's worth of good oil because one of you gaskets is weeping and you need to strip the engine down. Some people would reuse it but remeber that oil runs through you turbo so any crap in there could cost you your turbo.
That pretty much covers it, all the above is what I've actually used to make a genuine 300bhp+ obviously it's not the be all and end all of it. I'm sure there are better products out there (its been nearly two years since I built the above) but the above works. All figures are based on a F4R lump that was still running PAS and AC so simply deleting either would give an increase in power.
Hope the above helps people who are genuinely considering building a Turbo Clio