5. Porsche Cayman + Metzger 4.0-litre

4. Fiat 500 + 999cc TwinAir

3. Ford Fiesta XR2 + 999cc EcoBoost

2. Mazda RX-8 + 2.0-litre VTEC

1. Lotus Exige + 1200bhp V8...?

1. BMW M1 + M135i straight six

Ever driven a car and wondered 'how good would this engine be in a ()? Or on the flipside, what great modern cars are spoiled by anaemic engines, and need an old-school kick up arse? Here's my top five. We do love a good Porsche Cayman at CT . Luckily, there's no such thing as a bad one. The Cayman R is the best of the bunch, even if it's tricky to drift...But with that perfectly balanced chassis and handy size , all we've ever wanted to know is what would a Cayman be like with the full Porsche RS treatment. We're talking fully stripped cabin, roll cage, Alcanatra everything and most importantly of all, a 911 GT3 RS motor. And what could beat the ultimate RS engine: the 493bhp 4.0-litre flat six from the last 997? Louder and harsher than the new direct-injection 991 engines, it'sFiat's Panda TwinAir is cute, fun and sounds brilliant, but the new 500 is a bit porky to really get anywhere near those huge 80mpg claimed scores.On the other hand, an orinal 500 is tiny, lightweight and even cuter, but has to tool around with just 13bhp. You can see what happens next. Why not stick the TwinAir turbo in the boot for proper old-school rear-drive cool?If you've not tried Ford's magic new 1.0-litre EcoBoost , do it soon. The engine block fits on an A4 sheet of paper. Its turbo spins at. And it produces the same 123bhp and 120lb ft as my 1.7-litre Puma . It'd be fun to stick one in the baby Ford coupe, but it's a shame to bin the brilliant old Yamaha motor. So instead let's plumb one into a Fiesta XR2 in place of the wheezy 96bhp 1.6. Pepperpot wheels, front foglights, and and Mazda's RX-8 coupe has loads going for it . It'll seat four, gets loads of kit, and it's a blinder to drive. So why are they going for £1500 used? Because the 228bhp rotary engine is a liability. It uses oil faster than a tanaholic chip shop owner. It does 11mpg when pushed. And if you stall it while the engine's still cold it'll land you a bill for draining a flooded rotor housing. What we need is a revvy, 230bhp-ish naturally-aspirated petrol engine that doesn't have the reliability record of a Lib Dem MP. Hear that? It's a Honda S2000's VTEC bulletproofing the RX-8's Achilles' heel.Oh no, wait. Someone already did that. Awkward. Ahh, the BMW M1.. Spawns the world's greatest range of fast saloon and yet you almost never hear about it.. Well, since BMW can't make their mind up about an R8-fighting successor or not, let's play devil's advocate. I'm sticking with a straight-six, but lobbing a turbocharger into the mix: the M135i hot hatch's 316bhp motor to be exact. Finished up, the M1+35i dishes out 43bhp more than the hatch......but weighs 175kg less! Time to make that wedgy Giugiaro body actually move as fast as it looks!