Prologue: Once upon a time there was a turbocharged engine…

Turbocharged M10 engine in 2003

Actually my ambition for engines started a way before the engine in the picture was built. Back in 1996, the first engine was a naturally aspirated BMW M10 2,0 engine with hotter cams, 4-2-1 headers and Solex four barrel carburetors. So it was a pretty standard tune, around 150-160hp. Afterwards, it was a good school to understand the basics of engine building. And a good reminder, how demanding it is to increase power in a naturally aspirated engine for a daily driver.

In 2000, I built my first turbocharged BMW E30 with M10 engine. Initial version was a 1,8 litre M10 without intercooler, just a basic built with a better clutch. Back in the days, there was a lack for both modern and budget friendly engine management systems, thus I ended up using a modified Turbo Saab K-jetronic injection.

Second evolution turbo engine was 1,8 litre M10 with intercooler and water/methanol injection, and a turbo from 4WD Sierra Cosworth. K-jetronic got also a companion from Haltech piggyback. After wasting one cylinder head with knocking, I decided to improve the engine management system with a knock detection system. It was also from Saab, a system called APC, Automatic Power Control. Well, it was the analog system back in the days, but I was able to find one from a scrapyard, with little to no cost. I just upgraded the box (with soldering and changing resistors) with Turbo Saab’s track settings, making it a very budget friendly purchase. It was able to read knock signal from the M10 block and adjust the boost pressure according to knock level, and a potentiometer in a dasboard. Pretty cool system back in 2001.

The Third and the final evolution of the turbocharged engine, in the picture, was stroked M10 engine with 2054cc displacement, better headers, ported head, increased compression ratio and a hotter cam. The cylinder head I ended up using was from the naturally aspirated engine in 1996-1999. At the time, it had the most modern turbocharger (at least the price was very high, remember it being around 1200 euros), custom built hybrid Garrett TB03/04. What started as a modest, low budget engine ended up having the engine with a really nice torque and power band. For some reason, I have been always very allergic for any turbo lag, the phenomena I always wanted to get rid of. This engine version developed 0,2 bar boost on 2000 rpm, had 1 bar of boost in 3000 rpm, while maximum boost being 1,2 bar. The engine revved up happily to 6600rpm redline. It was very drivable engine for twisty roads with no turbolag, a fast enough in a car weighing only 1030 kilograms.

Take Home points:

  • Use knock detection and automatic boost control for gasoline engines,
  • Use wideband lambda for AFR measurement,
  • Use exhaust gas temperature, EGT measuring for optimal power,
  • Don’t forget Intake Air Temperature, IAT measuring,
  • Avoid too low compression ratio,
  • Aim for bast burning characteristics,
  • Use proper oil cooling solutions for both engine and differential,
  • Remember the importance of Engine Management Systems: Aim for easy tuning and data logging.

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