Fooling the ECU


Has anybody tried this product -

Which (in case my copy & paste above doesn't work) is the Magnum Dyno-BOOST.

Magnum claim mighty performance increases for the YRV (mine)and petrol Rocky and Feroza (about which I know very little except that they are really tough).

Their description calls it a 'chip', but I know it's probably really something like a fixed 4.7Kohm resistor (a few pence at Maplins) which substitutes for the inlet air temperature sensor and fools the ECU into thinking the air is much colder, so in ecologically friendly manner the ECU calls for more petrol, which they say produces more power (rather than an over-rich mixure to mess up the cat?).

Any particularly long-term experiences of this type of product?

YRV Tony

I would rather use a good

I would rather use a good piggyback, like the UNICHIP Q

Japanese cars are best.


Forget it it will not work properly and screw up your cat and engine in the long term. The air inlet sensor does not measure the air temperature, it measures the volume and density of the air to allow compensation for varying conditions encountered during hot summers and cold winters, and adjusts the fuel supply as required. All this and ensuring the emissions stay within the required tolerance.

Who ever posted this is a total dickhead as they clearly have no idea of fuel injection systems and engine management, over the years i have seen more such claims, and not one could be substantiated or proven to work. To prove my point i have had engines on the rolling road and shown how much power is lost due to incorrect fuel metering, and have even stripped one engine to show the effects of bore washing due to surplus fuel being injected. In a petrol engine it has a mixture, that is fuel and air mixed in the correct proportions for the engine speed, acceleration, and load; to put more fuel in requires more air to ensure the mixture is correct.

Fooling the ECU

Thanks for that Assassin. I thought as fact the way you describe it, it's much worse than I had suspected for the engine.

The post on eBay provided by Magnum Tuning is a long and very earnest piece, designed to convince.

But you are quite add performance you have to first increase input air flow. An ECU controlled engine will then inject the correct extra amount of fuel to give added performance. For a carburetted engine you have to increase jet sizes appropriately or you would run weak and damage the engine.

Presumably the same logic applies to any engine 'chipping'.

YRV Tony

YRV Tony

The device you describe from

The device you describe from Ebay is the cheap variable resistor which fools the ECU into overfuelling - hence the claimed extra power.

Depending on the vehicle and the type of fuel management system, the lambda sensors detect the unburnt fuel from O2 readings and instruct the ECU to compensate for the extra fuel and negate the 'performance gain'.

In older fuel management systems this type of resistor could cause the engine to run permanently rich, use more fuel and wash the oil out of the piston bores causing rapid engine wear.

Most tuners can get performance gains from remapping the ECU's fuelling and ignition timing settings, but as the standard Sirion's 1.3 litre engine was giving 101bhp in any case ( at least in the F-Speed) improving the induction and exhaust and fitting a reprofiled cam would have been the next obvious and cost effective steps.

Any bhp achieved after that would be a much greater cost or would remove a lot of the car's everyday drivability.

Chip Tuning

Lets clarify the situation once and for all with chip tuning:

The ECU holds a map, this collects various information from various types of sensors located within the engine, or where appropriate, an integrated engine, transmission, ABS, or other systems on the vehicle. This works within a certain limit and will adjust the engine to whatever the optimum conditions are for your particular driving style within 1/1000th of a second.

Factory vehicles leave with an average setting or map in the ECU, this is where many chip tuners excel by optimising these settings for a sporty biased drive on performance vehicles, or a torque biased system on 4X4's. Theoretically, many cars can obtain a chip tuned performance advantage, but the important question is what power gain for what cost. On a YRV engine, we know it is a well designed engine, well made, and to tolerances at the higher end of the quality and manufacturing scale. This means a large cost for a very insignificant performance gain, and to achieve more will mean going outside the tolerances pre set within the ECU; this means it will drop into limp home mode as it exceeds these tolerances, and the ECU senses a fault. On a lower performance engine such as your average repmobile, significant gains can be made by chip tuning, these are far lower output engines, and manufactured to lesser tolerances, this is where the gains are made as far more can be achieved by optimising a poorer system, and where chip manufacturers often obtain their data from.

The ECU has a pre determined limit, to obtain more power would entail a full reprogramming to alter these limits, once done more power could be obtained, but as we see the YRV is a good performer manufactured to significantly better tolerances than most, so it would not be effective on this engine. Even if this were done, the sensors on the engine would be working outside their limits, so it would drop into limp home mode as it would sense a fault. So we can conclude very little power for considerable expense as all these need to be changed for suitable items, so we now have a full injection system change.

Now we need to look at the mechanical aspects, the engine is a good performer, the inlet side is ok, the exhaust is ok, so the constriction is within the engine itself, so larger valves matched to a better profiled camshaft would be the next bet. The performance gain would be more significant as more air can be admitted, this can utilise the full range of our standard injection system, so no chips, its purely mechanical as it removes the constriction which is mechanical. We know the combustion chambers are fine as they produce considerable power from a small and reliable engine, so this is the next best option, but with expertise they may be worked slightly to obtain better combustion.

Now we know the main problem we can address it, get more air into the engine, and if possible, more dense air, and we know the standard injection system will do the rest, so its the camshaft and valves which need work. Minimal cost, more air, and the standard injection will provide considerably more power.

This dispels many of the myths of chip tuning, and the fraudulent claims made by the poor quality rip off merchants, but keeps the reputation of the excellent chip tuners who provide accurate data instead of inflated claims.

Hey assasin that is such a

Hey assasin that is such a good post and even to very limited mechanical minded guys like me, it is very clear. Your point bears out exactly what I have read and indeed points out why Daihatsu followed exactly your guide on modifying Camshafts/ airflow and indeed said that this was the best method of getting the extra power they were looking for in the Rally2/4 engine. They too found that as they tried to tinker electronically, the ECU 'compensated' and so that route was futile.

I have had the experience of good results from having a Rover 75 2.0 CDT chipped to give it similar performance to the later model CDTI. However, after reading your comments it is obvious that much research needs to be done regarding any engine one might be thinking of chipping, especially as a fee of around £400 plus is often asked.


This is the issue, an engine such as the Daihatsu unit was well optimised from the factory, the Rover was not, this is why it, and many others respond well to chip tuning. Such optimising can be taken further on some engines, and less so on others.

Moving this on means a rolling road so the chip can be tuned to the cars specific characteristics, this may include any other mods, or even wear and tear on the engine. This is the optimum for the vehicle, and at around a cost of £80/hour is indeed expensive, particularly if it is on for the best part of a day.

The only real answer is to find the problem and resolve it, in the case of the Daihatsu unit is to improve the mechanical restrictions of valves and camshafts.