Read an interesting writeup on Diesel Performance Chips on a blog maintained by an Aussie named Joe, who's into offloading, camping, fishing, etc .... big time. Thought sharing it would benefit other pakwheelers also.
Breaking Limits
Separate to the manufacturer?s specification, is there some other fundamental limit that a component is safe to operate under? A common misconception is that components have a breaking limit. A fundamental rating which should not be exceeded. Keeping below the limit ensures safety for the component. Actually there is no such limit. Probability of failure is a continuous curve. There is no fundamental limit, but the chances of failure increase as stress is increased. Understanding that probability of failure manifests as a smooth, continuous curve is critical in understanding why more power means higher risk of failure, regardless of any other conditions. There is no safe limit, all components will fail eventually, the higher the stress the sooner they will fail.
An Example: Diesel Generators
Consider diesel generators. Large generators worth hundreds of thousands of dollars come with several ratings depending on the duty they are being utilized for. The standard ratings are:
The exact same engine gets three different power ratings. Continuous is for when running all the time at full load and attracts the lowest power rating. Prime is for when running all the time but at varying loads, where full load is permitted only for restricted periods, and attracts an intermediate power rating. Standby is to supply backup power for limited durations and permits the highest power rating.
So, for a standby genset, the rating is increased and the generator is configured to deliver more power because the application is for short durations only ? you can get away with a smaller generator than you otherwise would for continuous applications, even with the same load. The manufacturer is picking points on failure probability distributions for various loads and time periods so that overall the generator will be adequately reliable. Run a generator at its standby rating for continuous periods of time? Then your warranty is void and you?ll likely suffer premature failure. I guess the generator manufacturer is doing their own in house version of ?chipping?, developing more power from the same engine, but it wears the engine out faster. Mechanically the engine is not changed, but the rating does change. Remember this is for an off the shelf genset worth hundreds of thousands of dollars, where the manufacturer has a huge development budget, perfect understanding of their hardware and plenty of development time to tune and optimise their products.
So, for a generator worth hundreds of thousands of dollars, the manufacturer doesn?t have the technology or capability to increase power without increasing failure rate. Why can?t they increase power in a way that doesn?t add stress to the engine, in the same way that some chip vendors suggest a chip works? It?s not possible. More power = more stress = increased risk of failure. There is no way to circumvent this. Increasing power in a genset from its continuous to its standby rating is the same as putting a chip in a vehicle?s engine. More fuel is dumped in, more power is developed, failure rate increases.
What if the increase in power yielded only an extremely small, insignificant increase in failure rate? Then genset manufacturer?s would always provide the standby rating. But they don?t. The difference in failure rate is significant enough for the different ratings to exist.
Lower RPM?
Some argue that a diesel performance chip allows lower rpm and thus offsets any additional engine wear caused by the chip. Almost all the time, with a chip installed, you?ll be doing the same rpm as without the chip installed. Some of the time with the chip you?d be doing higher rpm as you accelerate faster / drive up a hill faster / drive up the sand dune faster / overtake aggressively at high speed instead of waiting.
For a tiny fraction of the total operating time, having a chip may allow you to avoid changing back a gear. The chip allows more fuel to be dumped at lower rpm so that you can develop the power you need without the higher rpm necessary if the chip wasn?t installed. In either case the engine is generating roughly the same power but at different rpm. To develop the same power at lower rpm means more stress per power stroke. The reduced wear made available through reduced rpm is offset by more stress per power stroke. In fact you could argue that in this case, higher rpm yields less wear, because the same power is spread across more power strokes. Concentrating power usually increases wear in a non-linear fashion. However the dynamics of an engine generating power at various rpm are complicated ? it?s a fight between increased combustion stresses vs reduced friction and acceleration stresses. A safe conclusion is that, since the operating time of such a situation is so minuscule relative to total operating time, and the overall energy delivered is the same in each case, it doesn?t make much difference. So for the same power (at varying rpm) a diesel performance chip will not significantly change overall wear and tear. But tap into any additional power, then wear and tear will be increased. So the net result is that a chip increases stress and therefore wear and tear and so reduces the life of components.
How Much Will Component Life Be Reduced?
How much does wear and tear increase when a diesel performance chip is fitted? It?s hard to say, but we can make some guesses. In terms of mean time between failure, mechanical components with metal sliding or rolling against metal often have a cubic relationship with load. So if your chip delivers 35% more power, then mean time between failure is reduced by a factor of 1.35^3 = 2.5. So, on average, components will fail around two-and-a-half times as often. The life is less than half standard. This is independent of initial conditions. It does not matter if the engine was originally de-tuned, and the reasons for the tuning. It does not matter if certain stress or temperature limits are not exceeded. It does not matter if the chip maintains exhaust gas temperatures and coolant temperatures below certain values. It even does not matter if you treat the engine like a princess, service the engine every week, use the best most expensive oil and tenderly rub the car down every night. Any 35% increase in power, from any starting point, under any conditions, will reduce mean time between failure by a factor of 2.5. This is the nature of how failure manifests. It?s physics. Failure is a continuous curve.
In reality you won?t always be using the extra power, so mean time between failure will be affected to a lesser extent. Lets say you use 35% extra power for 10% of the time, 15% extra power for 20% of the time, and no extra power for 70% of the time. Taking a weighted linear combination to approximate the change in mean time between failure, you get 1.35^3*0.1 + 1.15^3*0.2 + 1^3*0.7 = 1.25. So component life will on average be 25% less. You?ve lost a quarter of the life.
This calculation is very rough. I?m not trying to give an exact figure. The point I am making is:
A significant increase in power must result in a significant increase in failure rate
To increase power without significantly increasing failure rate is the equivalent of saying:
I?m going to significantly increase speed without significantly increasing wind resistance
The relationship between speed and wind resistance is fixed. Wind resistance is proportional to speed squared. There is no alternative. There is no range of speeds where wind resistance remains relatively constant. The relationship is the same all the time. The same applies to power vs failure rate.
You can?t get a significant increase in power without simultaneously increasing failure rate by a significant amount. You can?t use that extra power for a significant period of time without simultaneously increasing failure rate by a significant amount. If you want to increase power without significantly increasing failure rate, then you need to restrict the increase in power to be practically imperceivable, or restrict the time that you use the extra power to be almost never.
Circumventing Restrictive Emission Systems?
Chips dump more fuel into the engine. Dumping more fuel means a bigger bang and more stress. Yes the original manufacturer may restrict fuel injection quantity for emission reasons but that is irrelevant. If you dump more fuel you increase stress which increases failure rate. This is true for any starting point, independent of initial conditions, independent of the reasons behind those initial conditions.
Do chips circumvent some other restrictive emission system, like EGR valve, catalytic converter or diesel particulate filter, that frees up some hidden capacity in the engine? Two answers. Firstly, no, chips have absolutely no interface to these devices and cannot physically affect them. Secondly, if they did, why are you giving me acid rain, smog and cancer just for your selfish desire to have more power?
Part of the reason fuel quantity is restricted is to minimize the production of soot. Dumping more fuel will generate more soot. The extra soot is another way the engine wears out faster, in addition to the extra wear caused by increased combustion temperatures and pressure. With extra soot you can also expect your EGR valve, catalytic converter and diesel particulate filter to clog up faster than usual and require extra maintenance.
Check out this article for a discussion on emission systems
More Sophisticated Chips?
What about your top of the line super expensive chip that employs multi-point fuel adjustment, fuel mapping adjustment based on throttle position, boost adjustment, timing adjustment and exhaust gas temperature compensation? Unfortunately these chips can?t escape the laws of physics. More power means more stress and more stress means increased risk of failure. Different brands will use extravagant wording like ?sophisticated mapping techniques,? ?extensive research and development? and ?optimized injection timing? etc but they are not special. Fancy chips simply dump more fuel into the motor, same as cheap chips. They just have more flexibility in the fuel mapping and have a few different ways of adding the extra fuel (and air). Fancy chips may also employ techniques to reduce the risk of limp mode, fault codes and engine check light. This is by adjusting inputs to the engine management system so it does not flag some sort of parameter correlation fault. It in no way changes how the chip develops more power nor does it change the affect on failure rate.
Whether a chip adds more fuel by increasing fuel rail pressure or whether it increases boost or whether it increases injector pulse time, it?s not really relevant. Each vendor will say their method is the best. Any method increases failure rate.
An expensive chip will probably reduce the risk of very large increases in failure rate, particularly if you are going for large power gains. For example the fancy chip may reduce how much extra fuel it adds when coolant temperature or exhaust gas temperature get dangerously high, or know to limit fuel addition at certain boost and rpm values where overfueling could be an issue. A cheap chip might keep adding more fuel until the engine suddenly fails. Apart from that the affect on failure probability is the same whether it?s a cheap chip or expensive chip.
Tuning?
Some vendors, particularly those selling piggy back ECUs, will have you think that ?tuning? is some sort of sophisticated optimisation process. It is implied that efficiency is improved through the tuning process. Actually tuning involves finding out exactly how much extra fuel can be dumped into the engine under various conditions. So if you want to really push the limits on what your engine is capable of then tuning is helpful. This doesn?t change how the extra power relates to failure rate. Using fancy programmable chips and tuning them on a dyno does not circumvent the laws of physics.
If you are after modest gains then any old chip from a reputable supplier will do. Plug it in, use it at a low setting and you should get acceptable results. If you want to push the limits then get a more fancy chip or piggy back ECU and tune it on a dyno. In either case you?ll suffer from increased failure rate. The higher the increase in power, the higher the increase in failure rate. Tuning at higher power gains will prevent high risk problems like over-fueling.
Is Your Engine Purposely De-Tuned?
To market their products, some chip vendors suggest your engine is de-tuned from the factory. De-tuned with respect to what?
There is no inherent or correct tuning level for an engine. No tune is more valid than any other tune. Any particular tune is simply picking a point on a continuous curve. No point on that curve is more special than any other point. Any tune is de-tuned with respect to a level of tuning higher up the curve. Similarly, any tune is over-tuned with respect to a level of tuning lower on the curve. It?s all relative. This means every tune is simultaneously de-tuned, over-tuned and perfectly tuned, depending on your reference. The chip vendor will label the factory tuning level as de-tuned to justify adding a chip. It?s irrelevant. If you crank up the power then you must increase failure rate. The starting point, and the reasons for it, are irrelevant.
Why Are Diesels So Easy To Chip?
Unlike petrol, diesel engines can run very lean (excess air). In fact, with modern diesel engines, they almost always run very lean. This encourages more complete combustion, improved fuel efficiency and less soot production. Running excess air means it?s a piece of cake to make more power ? simply dump more fuel.
Although petrol engines are tuned to run as lean as possible to maximise engine efficiency, they cannot run as lean as diesel engines. They run close to stoichiometric ratio of 14.7:1. Running lean on petrol causes inconsistent burns (leading to engine knock or pinging) and excessively high combustion temperatures. So there is little to no excess air in a petrol engine. You can?t simply dump more fuel. You need to get more air in the engine too. This makes getting more power out of a petrol engine much more complicated compared to diesel.
If You Do Have A Failure
So if you have a mechanical failure with a chip installed, was it caused by the chip, and if so can you claim warranty? People will find reasons like ?bad fuel? or ?bad driving style? or ?abused car? or ?towed a heavy caravan? or ?crappy design.? All those reasons might be valid, and could contribute to a failure. That doesn?t mean the chip didn?t contribute. As soon as the chip is installed it?s contributing to additional wear and tear and potentially contributing to an eventual failure. That extra wear and tear accumulates over time. People often relate a failure to a recent event or what the car was doing at the time. Actually failures develop over long periods with many contributing factors. Almost certainly a chip would contribute to a failure, because it is stressing out components more.
Your vehicle manufacturer?s warranty will be void, no question. And rightly so. You?ve overloaded the engine and science tells us this modification would certainly contribute to the failure. No investigation is necessary. Vehicle manufacturer?s warranty is void. It?s very easy for the manufacturer to legally void their warranty with this sort of modification and I 100% support them in this case. If you sold buckets rated at 20kg and someone put 30kg in the bucket and broke the handle would you provide warranty?
What about the chip manufacturer?s warranty? Some warrant their product against damaging your engine. However it?s very difficult to prove the chip was the main culprit. Normal wear and tear would have contributed. A defect in the vehicle could have contributed. I am yet to hear of a chip manufacturer footing the bill for an engine failure, despite many engines going bang. You would need to employ an engineer that specializes in engine failures to investigate the cause of the failure and produce a report that you can take to court. This could cost thousands of dollars and consume a lot of your time.
Essentially, if you get a diesel performance chip, you?re on your own. Use at your own risk. The vehicle manufacturer is freed of any responsibility because you?ve overloaded the engine and it?s difficult to pursue the chip manufacturer.
Will a Chip Save Fuel?
This is something that particularly annoys me ? the dishonest marketing of chip vendors claiming that chips improve fuel economy. Some throw around ridiculous figures like 30% improvement. Where the hell is 30% of the fuel injected into the stock engine going?
I feel for people who buy a chip to save fuel. How can a device that dumps more fuel into an engine save fuel? Chips increase fuel consumption. This is true for practically all scenarios. Chips do not improve combustion efficiency, they dump more fuel into the engine.
Do not buy a chip if you want to save fuel
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With a chip you drive faster. This means without a chip you drive slower. Driving slower means:
- lower RPM
- less mechanical friction
- less wheel friction
- less wind resistance
- less energy wasted accelerating towards conditions where you need to slow down
Every point above saves you fuel. This is without a chip.
Any device that claims ?more complete burn? you can instantly dismiss as having any fuel saving ability. There simply isn?t any margin to exploit on a modern engine in terms of more complete combustion (for more details search the net for info debunking fuel saving devices). Fuel efficiency is mainly governed by the mechanical arrangement of the engine / vehicle and the laws of thermodynamics. A chip does not alter any of those. Some people report a small increase in fuel consumption when a chip is fitted. Some people report a minor improvement. Some report not much change. The small variation in fuel consumption is less than the accuracy of the test, given all the uncontrolled variables when testing fuel efficiency.
Many people who report a fuel saving would experience psychological effects such as selective perception and confirmation bias. Many people who report a fuel saving are looking at the trip computer rather than actually measuring fuel use. When a chip is installed, a trip computer will always report better than actual fuel usage, as the chip is injecting more fuel than that calculated by the trip computer. Some people are so addicted to spending money on gizmos that they are desperate to validate their spending and will confirm everything that the marketing has trained them to believe. You will sometimes hear ?If I don?t use the extra power, fuel efficiency is improved.? The fact that the driver changes his driving habits, purposely driving more economically, makes the test results invalid. Use the extra power and you will definitely consume more fuel. The chip is putting more fuel into your motor. If there were ways to make a vehicle more economical through engine fuel mapping, the manufacturer would definitely exploit it. The manufacturer isn?t going to throw away fuel for nothing.
Some suggest that lower RPM afforded by a chip reduces fuel consumption. This is the only possible way that a chip could improve fuel consumption. For me this will never happen ? I drive for efficiency and I am nearly always in top gear at any speed above 60km/h. I can easily take a corner in third gear. I can up change so that the engine is barely above idle and still accelerate away. My Hilux has 126kW. A Hilux of 20 years prior had around 60kW. A modern vehicle has a tonnes of power. More power than necessary. I can change gears as early as I want. Anyone can drive like this if they want to minimise fuel use, with or without a chip. Changing gears earlier means accelerating gently. Adding a chip allows you to accelerate more rapidly given the RPM you decide to change gears at.
You may have heard someone say something along the lines of ?with a chip I can maintain 100km/h up a particular hill in my area. Without the chip I?d always slow down to 90?. This is what you?d expect ? with a chip you go faster. Wind resistance and friction is higher and so fuel economy suffers.
It is true that lower RPM reduces engine friction and thus reduces fuel consumption. However, with a chip, for the vast majority of operating conditions, engine rpm would be the same or higher compared to without a chip (see ?Lower RPM? section above). The time when a chip may afford lower rpm is when engine loading is increased beyond that capable of an unchipped engine, for example driving up a long hill, and you need to change back a gear. This is if you don?t simply keep it in top gear and allow the speed to fall a bit. But under higher loads, higher revs can actually be more efficient. At higher loads friction becomes less significant and the thermodynamic efficiency of the engine becomes more significant. Peak thermodynamic efficiency occurs at around peak torque, when compression reaches its maximum. So being in top gear and minimizing engine rpm doesn?t necessarily mean less fuel under high engine loads. You may have heard people who tow reporting improved fuel consumption by towing in a lower gear. This is because at high loads top gear may not be most efficient. Dropping back a gear may be more efficient, in which case the chipped engine will use more fuel. Either way, any difference in fuel consumption would be offset by being forced to go slower up the hill with the unchipped vehicle which means less wind resistance and less friction losses through the drivetrain and tyres. For all other scenarios, engine rpm is going to be the same (or less because you accelerate slower) when running without a chip so the rpm argument is not valid.
Another way that chips may increase fuel consumption is by encouraging less efficient driving habits. For example being able to accelerate faster means you?ll often approach a red light, slower traffic or an intersection faster than what you would have been able to without a chip. This means the extra fuel you burnt accelerating the car is a complete waste ? you send all that kinetic energy off to waste heat through use of the brakes. People with chips might be more prone to drive aggressively, for example overtaking only to have to immediately slow down in traffic. Again fuel is wastefully consumed heating up the brakes. In general driving faster also means higher losses through wind resistance and mechanical friction.
For ways of reducing fuel consumption that actually work, check out this article.
Leaning Out to Save Fuel
Some vendors claim chips save fuel by making the mixture leaner. On a diesel engine this is impossible. Diesel engines are not throttled through the air intake and are always running with excess air. Any claim of leaning out a diesel you can immediately dismiss. Actually chips make diesel run richer which reduces fuel economy and increases combustion temperatures and soot production.
What about petrol engines? Maybe in the old days there was some scope to lean out an engine. There was a large safety margin since fuel metering and instrumentation was crude. In a modern engine, with its myriad of sensors, sophisticated control systems and precise fuel metering, it comes out of the factory already as close to the limits as what the engine can safely run at. The manufacturer will not throw fuel away for nothing, especially given their billion dollar development budgets. They will exploit a lean fuel mixture as a way of maximizing fuel efficiency as best as can safely be done given the error margins and tolerances that can be achieved with the vehicle?s control system.
Is a Chip Safer on the Road?
Any study I?ve seen published on engine power vs mortality indicates that mortality rate increases with engine power. Similarly studies have found incremental increases in speed to be associated with incremental increases in accidents and death. This is why, in some jurisdictions, young drivers have restricted licenses which prevent them from driving high powered vehicles. This is why more powerful vehicles attract higher insurance premiums. If you think getting a chip is safer, you should see if your insurance company will reduce your premiums when you tell them you have a chip. I doubt it! When have you heard of a motor vehicle accident or fatality that was attributed to insufficient engine power?
Don?t use safety as an excuse to justify a chip!
If you want to be safe then drive slowly and patiently. Wait for long straight roads with no oncoming traffic before overtaking. Or even better wait for an overtaking lane or dual carriageway. Or even better still, drive slow enough so you hardly ever have to overtake. Not only will you be extremely safe but you?ll get rich from fuel savings too! And the difference in travel time is not much at all.
Conclusion
Driving fast doesn?t make me happy. Camping, fishing and being free in the outback makes me happy. Not getting a chip increases my capability of doing the things that make me happy. Without a chip I save money on the initial purchase plus I save money on a longer lasting vehicle. Plus I drive slower and save even more money on fuel costs and vehicle wear. This means more camping, more fishing, more beer and less working to pay for gizmos that don?t make me happy. So no chip for me. Ever. Even if it was given to me for free. It detracts from my ability to achieve my goals by increasing transport costs and reducing the life of my vehicle. Why would I want it?
That doesn?t mean you should not consider a performance chip. They are good products and they definitely increase power ? that is easy to measure and prove. They aren?t going to blow up your motor in 5 minutes ? they wouldn?t exist if they did, and many people have experienced long living engines with performance chips installed. If more power makes you happy then get a chip and acknowledge that the happiness comes at a cost. To minimize that cost, service your vehicle regularly, drive it nicely, use the lowest tune you?re happy with, minimize rpm, avoid short trips with a cold engine, get a chip that can be easily turned off when not required, keep its use to a minimum, drive very gently when not up to operating temperature and only tap into the extra power when you need to. Then your chipped vehicle should last a long time, even if it lasts less than it would have without the chip.
The purpose of this article is not to instruct people not to get performance chips. It?s to explain why more power means more wear and debunk the myth that extra power can be obtained risk free. You can?t get something for nothing. Chips do increase wear and run the risk of contributing to eventual failures. More power will be of greater value to some ? for example those who enjoy fast acceleration or those that tow a heavy caravan. The benefits of a chip are greater under high load such as when towing, however the risks are greater too. Preferably you should have bought a car with a bigger engine or even better tow a smaller van or nothing at all. But it?s up to the individual to decide their vehicle setup and whether a performance chip is worth the risk. For me I am happy chugging away with my slow but hopefully long living 4WD.
Driving on soft sand is one area where a diesel performance chip may help. It can prevent you from losing revs and speed, giving you a chance to power through deep sand rather than getting bogged.
