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The heart of the matter

Source: Race Engine Technology

Publication Date: 17th July 2007


Smart Fire

Earlier this year we revealed the ‘Super Turbo’ invention by Woodward, which may well make an impact upon Formula One when new energy recycling systems are permitted. Woodward has already made its mark upon Grand Prix engines with its SmartFire ignition system, invented by Super Turbo co-inventor Ed VanDyne and now distributed by the SuperFlow Technologies Group as the SuperFlow SmartFire system.

As described in Race Engine Technology 012, the SmartFire system provides a high-energy spark and also acts as a combustion sensor, hence its name. It can be used on the track as an alternative to other forms of knock sensing, of which the block-mounted vibration-type is the one most commonly used in racing.

Generally the SmartFire feedback system is used on the dyno to assist the mapping process, enabling the engine to be accurately tuned to the detonation threshold on a cylinder-by-cylinder basis. However it can also be used on track as an input to the engine control system, in which case it is described by VanDyne as "about 70% as effective as cylinder pressure for getting information out of the combustion chamber. For logistical reasons the in-chamber pressure sensor is rarely seen outside of the dyno environment and then generally only for prototype engines".

At least one engine management system supplier has incorporated SmartFire technology into its current Formula One system. In this case it is used primarily as a pre-race engine-tuning tool rather than as part of a closed loop control system for running the race itself.

The Formula One engine has ignition timing as early 60 degrees btdc and a bore size and a bore to stroke ratio that are both high relative to slower running racing engines. Consequently detonation is not the primary concern in the Formula One engine environment. On top of that an engine accelerating from 12,000 to 19,000 rpm in less than one second is operating too fast to properly interpret Ion signals for closed loop control, which is prone to variation at that speed.

In contrast, VanDyne reports that SmartFire has been part of a closed loop control system for a leading sportscar racing engine, one running to less than half the speed of a Formula One engine. In this instance the engine had previously been using a block mounted vibration sensor. But that had been found to react to cornering loads transmitted through the fully stressed engine structure. The upshot had been as much as 12-degrees unnecessary retard across all the cylinders. Switching to SmartFire as the means of detonation sensing saved that wasted engine performance since SmartFire reacts only to knock and only retards the cylinders that are knocking.

Arguably SmartFire is inherently superior to block and spark plug washer knock sensors. In NASCAR, VanDyne reports that a Cup team has successfully exploited SmartFire in track testing (data acquisition is not permitted at race meetings). This has translated into superior race day pace.

NASCAR teams rely heavily upon conventional spark plug readings. But these only provide engine running information just prior to engine shut down, reaction to which can adversely affect overall performance. A lack of fuel might be specific to a certain corner, for example, so richening the mixture across the board will unnecessarily compromise performance elsewhere on the circuit.

In the case in question, on a particular circuit there was a leaning out of the inside bank of cylinders on corner exit due to gforce generated by the banking. Knowing from the SmartFire data precisely where the problem lay enabled the team to use asymmetric acceleration pump settings in the carburettor rather than change the jetting. Thus was the problem solved without any compromise to top end horsepower.

VanDyne notes that for a Cup team the use of SmartFire can reveal the true effect upon the fuelling of g-forces from banking, which cannot be replicated on a conventional dyno. This information can help a team improve its intake manifold design or even implement a different strategy, such as tilting the engine within the chassis. Cup teams sometimes use that technique.

VanDynes explains that on the dyno, a Cup team can use SmartFire to dial in individual cylinder timing: that individual cylinder timing can be transferred to the distributor by bending or filing the trigger wheel inside. The individual cylinder timing within the distributor can be verified on a distributor machine. This technique has been used in the past to retard knock-prone cylinders, but using SmartFire the timing can be customized for each cylinder of each engine.

VanDyne notes that SmartFire has also proven beneficial to a NHRA Pro Stock team. It was already known by the team that its engine could not tolerate as much spark advance in the higher gears as in first gear; combustion chamber temperature increases over time with the increase of engine loading throughout the quarter mile run. The mandatory MSD ignition system enables the timing to be adjusted at each gear shift but the actual timing that is safe in each gear was not previously known. It was experimentally derived, which can be expensive when you go too far.

"Before they used SmartFire, they didn’t know precisely where detonation occurred within the run," notes VanDyne. "We were able to give them 4 degrees more timing in first gear. They knew they could run that safely on the dyno but each time they had followed dyno readings on track the engine had failed. Until they had our feedback they hadn’t appreciated that they could get away with that much in first gear..."

Changing the subject to compression-ignition, VanDyne notes that the SmartFire system provides a very hot spark, which can be used in place of a conventional glow plug in diesel engine applications. Having the SmartFire plug in each of the cylinders of a diesel engine enables it to be used as a diesel combustion analysis tool. SmartFire has already been used on the test bench for the development of a high profile diesel racing engine and there is potential for it to be used on the racetrack.

A key challenge of the diesel race engine is transient performance. When the driver accelerates there is not necessarily sufficient combustion chamber temperature to ignite the fuel at the calibrated timing, leading to a ‘soot spike’. The tendency is to err on the side of caution, leaving injection late at the cost of potential performance.

To avoid smoke (any sign of which is against the rules at Le Mans) and to optimise engine output it is necessary to tailor the turbocharger output (via the electronically controlled wastegate) and the fuel injection timing to in-cylinder conditions. There is no obvious means of reading piston crown temperature. However, SmartFire’s real time ionisation signal can be a means of successfully monitoring diesel incylinder conditions. It could therefore conceivably be part of a closedloop fuelling system for racing diesel engines.

Currently Woodward is working on its own engine management system, which will link to SmartFire and will offer closed loop control on direct combustion feedback in gas or diesel engines.

Added to the database on 17th July 2007

Keywords: Super Turbo Woodward Formula One Ed VanDyne SuperFlow SmartFire