Is supercharging an NA worth it? Road and track experience

What owners liked

• One owner described stage 2 as the same linear pickup and throttle response as the NA, just more of it, plus a useful amount of torque for trickling about. Another said the extra power is much better on the road than it is on track.
• You can pass on straights instead of sitting behind a quick car with a poor driver. Several owners said keeping up with, or passing, much more expensive cars was reward in itself.
• A simple stage 2 can be reliable. One owner said his did 40,000 miles and over 70 track days after being converted, and advised not messing with it. Another had done 1,500 miles since his upgrade without trouble.
• One owner said that if you source parts sensibly, the car's value rises by roughly the cost of the conversion, so the money isn't lost the way most modifications are. That is one opinion.
• An owner with a 2013 stage 2 car said it is as reliable as a standard 2.2 if you stay under about 260 bhp and top up the oil more often.

What owners warned about

• Cost keeps growing. Everything costs more, and it is harder to drive the car quickly, which normally means spending more to cope. One owner who went from NA to Harrop said it took two years before the car stopped letting him down. See the parts and costs guide.
• More stress on everything: brakes get used more, tyre wear rises, and suspension bushes and tyres wear sooner.
• Lazier driving. Two owners said the car was easier and less engaging on track; one pointed out you can feel like you are playing the same game on an easier setting. Another said he sweats just as much. A third said a good driver in an NA will beat a poor driver in a faster car once corners and braking zones come into it.
• A compromised middle. One owner who had fitted stiff suspension and a loud exhaust said it was too compromised for the road and too noisy and too good for track days, so it sat in the garage. He planned to go back to stage 2 with standard bushes and a milder set-up.
• Heat on track. An owner who wouldn't go back to NA said the charge cooler radiator blocks the main radiator, and that on hot summer track days in 30 minute sessions it gets hot. His suggested fixes, not tested: an extra water radiator, a front clam cut-out, water injection, or smaller twin charge cooler radiators behind cut-outs under the headlights.
• Fuel surge on left-handed circuits can be managed by using a higher gear between long left-handers. He thought a Pro Alloy upgrade would be better still (he wrote "rad", which may mean the fuel tank; see Fitting a Pro Alloy fuel tank). The cause, he said, is the tank design.
• Pick your track days. On a quiet day the car is quicker than most of the field and you may be held up.

Stage 2 or beyond

• One owner who ran a big-power supercharged car said stage 3 at about 300 bhp was great but needs engine work, such as rods and pistons; once that is done, a larger blower and a few extras take you into the higher-power cars. Another said one of those cars was hard to drive fast.
• Owners in 2013 said they thought the con rods were the limit above about 260 bhp, and one said he intended to keep stage 2 as long as he could resist, because forged internals cost a lot.
• One owner with a supercharged car said that in hindsight he would not go past stage 2.
• One perfect-track-car answer was an NA with 220 to 250 bhp, but he said the engine build would cost many times more than dealing with the supercharger's heat.

Against an E46 M3

The original poster asked how a supercharged car compares with an E46 M3, which is a fair question because owners kept using it as the yardstick.

• One owner who has owned both said straight-line speed is about a draw: the VX is a little ahead off the line and an M3 pulls away once you are into licence-losing speed, mostly due to gearing. On corners and brakes the M3 is a barge, he said.
• Another said a stripped, caged M3 on coilovers and big brakes had done 1:37 round Cadwell and a VX won't match it.
• An owner said Snetterton has long straights where a BMW is in its element, and one said modern M3s are quick in a straight line.
• The original poster said an M3 with only brakes, coilovers and semi slicks had done 2:12 at Snetterton. An owner whose supercharged car runs 2:14 there thought 2:12 was possible with less understeer, and said single-lap times are not a good measure of a track car because an M3 will eat tyres, pads and bushes.
• These are lap-time anecdotes from different cars and drivers, not a comparison.

Advice owners gave

• Get a passenger ride from a local owner first, so you feel the difference rather than imagine it.
• Fit the suspension, tyres and gearbox you want first and see how you get on.
• Do the simple stage 2 and enjoy it.
• If you can't do the job yourself, owners in 2014 said the conversion labour was good value, but learning it yourself teaches you what to look for if something goes wrong. See UK specialists and parts suppliers.
• Wheels and brakes: one owner suggested forged wheels and a carbon brake kit as a way of saving about 35 kg unsprung instead of adding power. That is an expensive idea from one post.