The Chips are Down

The Chips are Down


Steer clear of engine-enhancing power chips and mapping for your small-bore turbo diesel…

by Allan Whiting of 

Back when nearly all small diesels were naturally aspirated the performance enhancers pushed turbo kits and, later, turbo-intercooler kits. Some of these worked very well and some didn't. People who bought well-engineered kits and drove wisely had good experiences, but many a turbocharged pre-chamber diesel blew up. Our 2.8-litre HiLux expired with multiple combustion-zone cracks – and we had driven it carefully. 

Nowadays, all new diesels have forced induction, so the engine hot-up scene has shifted to newer gadgets. Manufacturers who thought the more-than-ample standard power and torque figures of 21st-century turbo-diesel engines would satisfy owners didn’t understand the passion for fiddling. 

In no time we had a wide choice of after-market performance chips. All these void engine warranty, of course, and are probably illegal from an emissions ADR angle. We say ‘probably illegal’ with some surety, because we’ve asked several chip makers and ECU re-mappers to verify that they don't alter ADR emissions compliance. None of them wants to go there, but then neither did some VW diesel engineers…

Chips and ECU re-maps are available from many sources these days and all claim to increase power and torque, and reduce fuel consumption. The fact that these devices increase power and torque is undisputed: any dyno test will prove that. We've tested some chipped engines in 4WDs and there's no doubt their performance was excellent.  Fuel consumption improvement is much more difficult to prove. Yep, we have some mates with 'chipped' diesels who swear their economy has improved, but we suspect that has more to do with a change in driving patterns – to produce the claimed result – rather than an inherent benefit of the chip installation. One even confessed that he found towing at 90 km/h produced the best economy, so we wonder why he bothered with an expensive performance-increasing chip in the first place? 

Chip makers and re-mappers claim their add-ons are well within engine design tolerances and can't do any harm. There is certainly some truth in this claim, but how do the chip designers know what the engine maker's exact operational parameters are? There is obviously some conservatism in the factory fuel injection mapping, but how much? Another assurance from chip makers is that their products are warranted against failure. Most chip buyers believe that's protection for them in the event of an engine failure. It's not: it covers chip failure. If your engine blows up or suffers serious wear after being chipped it's your responsibility to prove that the chip caused the failure. Good luck.

Understandably, the engine maker won't be interested in helping either. Some chip makers and re-mappers claim that 'enlightened' engine makers quietly endorse their procedures. We couldn't find any such 'enlightened' engine makers. Fit a chip or re-map the engine computer and you're on your own. We're also very concerned about the fact that all chip makers and re-mappers explain how their systems can't be detected by a dealer's diagnostic computer. If there's nothing to hide, why bother? 

One of our mates chipped his diesel manual to give him more flexibility and economy when towing, letting the vehicle run in top gear, rather than needing a downshift on hills. There are at least four downsides to this procedure: 

  • Firstly, the engine is operating at lower than designed revs for the torque/power figures it's producing and that loads the pistons, rods and bearings with forces that were never foreseen by the engine designer 
  • Secondly, combustion pressure and heat rise – check your pyrometer if you don't believe us 
  • Thirdly, loads on the overdrive gears in the box are also outside design expectations
  • Fourthly, water and oil pump speeds are lower at the very time increased cooling and oil circulation are vital

In most high-load, highway-speed situations a modern smaller turbo-diesel benefits from running no lower than 1600 rpm, while 2000 rpm is usually better. Heavy truck diesels and transmissions are different, having been designed from the outset to cruise and hill-climb at much lower revs.

Remember, the more power an engine produces the more stresses are placed on its internals and cooling system. Factory engineers do their best to balance output and reliability, but exceeding their (unknown) limits is a recipe for disaster – and an expensive one at that. Anyway, what’s the rush?

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