The shop car: a smoking 2009 Cobalt SS, built properly

Most of what gets written here is about other people's cars. This one is ours. Jeffrey Alexander spends his working life explaining performance and power gain, and the obvious next step was to do it on a car of his own, from a tired engine to a measured result.

The list of faults was not short. It was blowing smoke out of the tailpipe. It had no radio and no air conditioning. And cylinder 1 had no compression at all.

Either symptom on its own could have several causes. Together they point inside the engine. A compression test measures how well each cylinder seals: the piston rings against the bore, and the valves against their seats. A reading of nothing on one cylinder means one of those seals has failed outright, and oil getting past failed rings is a common source of smoke.

With the engine out and apart, the cause was plain. The ring lands on cylinders 1 and 3 were cracked.

A ring land is the narrow shelf of piston material between the ring grooves. It holds each ring in place, square to the bore, so the ring can seal. When a land cracks, the ring loses its support and the seal goes: combustion pressure escapes down past the piston, and oil finds its way up into the chamber. That is consistent with both the smoke and the dead cylinder.

His view is that it was probably a bad tune. Cracked ring lands are a typical detonation failure. When the mixture ignites uncontrolled, the pressure spike hammers the top of the piston, and the ring lands are among the thinnest, most exposed parts of it. On a turbocharged engine, too much ignition timing or too little fuel for the boost being run is the usual way to get there. Nobody can now prove what the previous calibration was doing, so it stays a probable cause rather than a finding.

The whole engine was blueprinted. Blueprinting means measuring every critical dimension against a specification and correcting whatever falls outside it: bore size and shape, bearing clearances, piston to wall clearance, ring gaps. A production engine is built to tolerances wide enough for an assembly line. A blueprinted one is built to the numbers the builder chose, cylinder by cylinder.

The block was bored .020 over. Each cylinder is machined 0.020 inches, about half a millimetre, larger in diameter, which takes the bore walls back to clean metal and leaves a true, round surface for new rings to seal against. It also means the original pistons cannot go back in: an oversize bore needs oversize pistons.

Everything that went into it, as he listed it.

The bottom end is ZZP connecting rods and Wiseco pistons. On an engine that has already shown it can crack a ring land, forged pistons are the usual choice, because they tolerate heat and detonation better than a typical cast piston. Stronger rods follow from the same arithmetic: more boost means more cylinder pressure on every power stroke, and the rods carry all of it.

The head has ZZP Z2 camshafts and 82 lb valve springs. An aftermarket camshaft changes how far and for how long the valves open, and the springs are what keep each valve following its cam lobe at high engine speed. Stiffer springs are there so the valve does not float.

The turbocharger is an S257SXE, with an intercooler and a TiAL external wastegate. Compressing air heats it, and the intercooler takes that heat back out before the charge reaches the cylinders, which keeps it dense and keeps the engine further from detonation. The wastegate controls boost by sending exhaust gas around the turbine instead of through it. Mounted separately from the turbo, it can be sized for the flow the engine actually makes, which is why an external gate is the usual choice on a high boost build.

Fuel is the part that catches people out on this engine. The LNF is direct injected: fuel goes straight into the cylinder at high pressure, supplied by a high pressure pump driven by the engine. Every bit of extra air needs fuel to match, and on a direct injected engine there are two limits to run into, the injectors and the pump that feeds them. The Opel injectors and the ZZP upgraded high pressure fuel pump address both. Running short of fuel under boost is how an engine goes lean, and lean under boost is one of the quickest ways to crack a ring land.

Boost itself is managed by an AEM electronic boost controller. It uses a solenoid to control the pressure the wastegate sees, so boost is held to a set target rather than to whatever the wastegate spring alone allows.

It got the same treatment as any car that comes through here: a baseline run first, so there was something to compare against, and then pulls as built.

This one is published as the graph rather than a full run table with conditions. On a phone, tap the graph to open it full screen, where the small print can be zoomed. If you have not read a graph like this before, the published E55 session explains what the two traces are and why they cross where they do, and how to read a dyno sheet goes through the rest of the page line by line.

Because it is the argument this shop makes, made on its own car. An engine probably killed by a bad calibration, taken apart to find out exactly what failed, rebuilt with parts that answer each failure, and measured before anybody said a word about power. If you are planning something along the same lines, the engine builds page is where that conversation starts.