E85, BUDGET RACE FUEL BUT NOT FOR BUDGET ENGINES by The last 25 years have seen some huge increases in engine output, but the biggest change is what can be achieved by the average street car. Modern engine management, efficient engine designs and affordable high-octane fuel has brought high power to average punters. When our Calibration Engineer Joel started tuning 25 years ago, he was using a water brake dyno, no electronics, mechanical dials, and a switch to double the scale from 200 to 400 rear wheel HP, and in those days, you didn’t often have to flick the switch. Everybody had a 400 engine HP small block something, though truly not many were. As time went on and EFI took over from carburettors, engines became more efficient and turbos became commonplace, a bigger dyno was required to accommodate the increasing outputs. One of the biggest limitations to making HP is fuel quality, in the past race fuels like C16 were not just too expensive for daily but at $20 a litre, it was even too costly to race with. Having said that, those that could afford it knew the difficulties that came with keeping an engine together, high octane fuel allows an engine to run optimal ignition timing and this is where the power is. Lower octane rating fuel will knock or ping at optimal timing so lesser ignition timing must be run preventing optimal power and torque. Come 2007-2010 and the introduction of E85 at the pump, affordable high-octane fuel, prior to E85 pump fuels were not capable of supporting
high compressions or high boost HP due to the octane rating. In a nutshell, to make power we need to push the piston down as hard and for as long as we can, this creates the maximum torque and torque makes power but also the harder we push the piston down the harder we try to force the cylinder head off and the harder we try to push the cylinder walls out. Newton said for every action there is an equal and opposite reaction, this has never been truer than in the combustion chamber of an engine. The potential of any high-octane fuel is realised as the engine is able to achieve MBT (maximum brake torque) due to being able to run optimal ignition timing without knock, the more retarded the timing is from MBT due to knock the lower the engine output will be as is the case with lower octane fuel. The higher the cylinder pressure due to high compression or high boost the further away from MBT timing low octane fuels will be due to having to run retarded ignition timing to prevent the occurrence of knock so it goes to follow the greater the gain from high octane fuel when timing is advanced closest to where MBT is achieved. Therefore, the reverse is true, a low compression engine with low cylinder pressure that can achieve MBT on low octane or regular pump fuels is likely to show little or no improvement on high octane fuel. In some instances, small gains are achieved with E85 due to reduced inlet charge temperatures All Action, All The Time from MotorWerks Magazine
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