From supercharged A-series to Honda power
Mighty Car Mods' little green Mini has been one of their longest-running and best-loved projects. It first ran a 1275cc A-series, the Siamese-port engine these cars are known for, with a belt-driven supercharger bolted on for extra shove.
A couple of years on, the team went a different direction and dropped in a Honda B16. It's a tried-and-tested engine most people know from the Civic, and it brings two things the old A-series never had: double overhead cams and VTEC.
Squeezing a B16 into a Mini
A classic Mini engine bay was never designed for a DOHC four-cylinder, so the fit was tight. Most of the Honda's factory parts stayed, but a few had to move to make everything clear. The most notable was the alternator, which came off the front of the engine and was relocated into a small gap behind the manifold.
That kind of packaging problem is typical of engine swaps, and it's a big reason people choose a standalone ECU. With factory Honda electronics you're tied to the factory sensors, wiring and layout. With a programmable ECU, you can wire only what the car needs and route it however the engine bay allows.
What VTEC actually does
VTEC is Honda's name for Variable Valve Timing and Lift Electronic Control. The idea is simple: one camshaft profile can't be ideal for both a relaxed commute and an 8,000 rpm pull, so give the engine two.
- The mild profile has less lift and shorter duration. It gives smooth idle, good low-speed torque and decent economy.
- The aggressive profile has more lift and longer duration. It lets the engine breathe at high rpm, where the power is.
On the B16, each cylinder has rocker arms for both profiles on both the intake and exhaust cams. At low rpm, the valves follow the mild lobes. When the ECU decides it's time, it energizes a VTEC solenoid, which sends oil pressure to a pin inside the rocker assembly. That pin slides across and locks the rockers together, so the valves now follow the high-lift lobe. The change is instant, and so is the difference in how the engine sounds and pulls. It's where the famous line about VTEC "kicking in" comes from.
How the Elite 1500 decides when to switch
In the Mini, a Haltech Elite 1500 runs the engine and controls the VTEC changeover. It doesn't just switch at a fixed rpm. It looks at several inputs before it allows the high cam:
| Input | Why it matters |
|---|---|
| Engine rpm | The main switch point, set where the high cam starts making more torque than the low cam |
| Oil pressure | The locking pin is moved by oil. Without enough pressure it can engage partway, which is hard on the rockers |
| Engine temperature | Keeps the high cam out of the picture until the engine is warm |
| Vehicle speed | Stops VTEC engaging while parked, for example during a free rev |
| Throttle position | Lets the tuner keep the mild cam at light throttle and only switch when the driver wants power |
The tuner chooses the switch point and the conditions that must be met. In our experience, the best rpm point is found on the dyno by overlaying low-cam and high-cam pulls and switching where the curves cross. That gives a seamless surge instead of a dip. The same thinking applies to any switched cam or runner system; our switched cam control article covers the Elite settings.
Why it works so well in a Mini
The B16 isn't a big engine, but the Mini is tiny. At roughly 1,540 lb (about 700 kg), there isn't much car for the Honda to push, so the moment the high cam engages the car simply takes off. It's an old-school car with an engine that loves to rev, and the combination suits it perfectly.
The interior is as small as ever. It's fine if you're under about 5 ft 11 in (1.8 m), but Scott, at about 7 ft 2 in (2.2 m), managed to drive it all weekend, which is impressive in its own right.
Planning your own VTEC swap?
If you're putting a B-series into something it was never meant for, a standalone ECU gives you full control of fuel, timing and the VTEC changeover. Read up on the Honda B-series engine, compare the Elite 1500 and Elite 2500, or check our guide to choosing an ECU. If the car still has its factory Honda loom, the Elite 1500 OBD-I B-series plug-in kit is the easiest path. Want help choosing? Book a free consultation.
FAQ
Can a Haltech ECU control VTEC?
Yes. VTEC is an on/off solenoid output, and the ECU can switch it on rpm, oil pressure, temperature, speed and throttle conditions set by the tuner.
Where should VTEC engage?
Wherever the high-cam torque curve crosses the low-cam curve on your engine. That changes with cams, intake and exhaust, so it's worth finding on a dyno rather than copying someone else's number.
