I am aware that I've covered some of this already, but just so I keep it all in one place......
And to fend off accusations of wasting money on a slow car when I should have bought a faster one instead, I should point out that I have gone back to my early small car modifying roots, having become disillusioned with fast cars on our increasingly crumbling and camera-monitored British roads. I am in the fortunate position to have an RS6 and Renaultsport Spider in the garage, but the Audi rarely moves these days, as the Panda is just so much more fun and far better suited to the Surrey highways than the stiff, yet monsterously fast RS6. The Spider is not really a car - it's a Spider, so that doesn't count and remains the perfect summer partner to the all-weather Panda. However, I have spent shed loads of money on the Panda but I don;t regret any of it....
In my view the Rotrex is perfectly suited to fitment on a small, standard engine as it makes it's power further up the rev range, as centrifugal chargers produce linear boost, unlike the displacement Roots types that can make lots of bottom-end busting torque that would require reductions in CR and beefier transmissions just to cope. Same issues experienced with Turbo conversions on standard engines. Although I invested in an uprated CG Motorsports clutch, it remains on the shelf in the garage for now.
My Rotrex is the smallest going - the C15/16 - and is normally fitted to motorcycle engines. It is geared to produce 11psi at 6500rpm and that makes 110bhp at 6300rpm and 100ftlbs at 4000rpm or thereabouts. But best of all, it makes 92ftlbs from about 2500-6500 rpm. It really is a fabulously flexible motor now.
It sits in the place that an A/C compressor would go, were my car to have had one. This really is the only realistic place to fit it. A 1.4 FIRE engine could probably take the C15/30, which has a bigger compressor housing and was the one I tried first, but the boost was simply too high for my 8v 1.2 and I had to restrict it too much to keep power/torque down to acceptable levels. In the end the restrictor was too restrictive for the unit and it popped a seal, so I went smaller still but without restrictor. Less drag, same power, perhaps slightly less torque, but safer and more efficient all over in general. The correct choice.
My car went from 60-110bhp without any currently obvious issues (2500 miles in and counting). My BIG issue was the Magnetti Marelli ECU that stays permanently on CLOSED LOOP, meaning that it would always keep the AFR's at a perfect 14.7:1. Whilst this is fine for a normally aspirated engine, a forced induction wants about 12.5:1 under full power and the effort required to crack the ECU was significant. In the end I went with a Dastek UNI-Q ECU with their iDriver module to fly the injectors. This has produced a nicely mapped motor that still makes 35mpg in day-to-day driving. It was only averaging 38mpg beforehand - a 90% increase in power for only an 8% penalty in fuel. Those Rotrex units really are very efficient.
Injectors went up from 145cc/min to 215cc/min and my engine used the small Weber Pico units, unlike the 100HP and Fiat 500 1.4's on the larger Bosch jobs. It is relatively easy to get hold of bigger sizes though (Competition Systems near Reading - thank you chaps). I needed to move to a Saab 2bar MAP sensor, as mine was a 1bar only unit that threw a spazzy fit whenever it saw more than atmospheric.
Exhaust is a Punto 4-2-1 manifold (suitably modified to miss the transfer box bit of the transmission) hooked up to a custom Longlife system and 200CPSI CAT courtesy of Matt at the FastFit Service Centre in Basingstoke. This was important as the std exhaust would never have had the flow rate required for 100+bhp...
The installation of the compressor was by TTS at Silverstone and they were excellent. The quality of their work is faultless and I have a fully CNC machined billet mounting bracket that looks 100% factory, matched to a billet machined pair of crank and s/c pulleys, running perfectly true, with the crank pulley machined for a perfect fit with the OEM crank pulley. It really is very professionally done.
Mapping and setup was by the hugely talented Paul Shepherd at Circuit Motors next to Castle Combe - one of the most knowledgeable ECU experts you'll ever meet.
Hmmm, costs - not good. Rotrex install was a one-off and therefore expensive, mapping and hardware a further chunk on top. Most of this mapping cost was of course time, due to the huge effort to work out how to crack that MM std ECU, so another would be much much cheaper I guess.
In hindsight, I am of course open to criticism with regard to the cost, which was nearly more than I paid for the car in the first place, but cost was not really a concern, as having run a horrendously expensive Audi RS6 for years, everything on the Panda appears to be almost free! If I did another project Panda 4x4, I would indeed look at splicing the 1.4 100HP engine onto a 4x4 drivetrain, as I believe that the gearboxes for all the FIRE petrol engines are the same. The 100HP is not a torque-monster either, so I sure the transmission would be just fine. Not too sure what wiring changes you'd need, but provided the engine came with the ECU and loom, you should be OK. Lewey would be able to confirm, as he's done all sorts of engine transplants in the past.
This would make a good combo I think, as with an induction kit and exhaust it should make the same power and torque as mine, but without the cost and complication of the s/c of course. Won't make quite the same noise that only a Rotrex on a small engine can make though....
Nuff for now.
Phil
