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Old 27th May 2005, 11:48   #1
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Default Valves and bits, what's this ?

Hi Guys,

Since the dawn of euro emission norms, a lot has changed in the Indian automobile scene. Euro 1 saw implantation of catalytic converters in all cars. Euro 2 saw implementation of multipoint fuel injection (MPFI). Alongside the new fuel management system, some car manufacturers also increased the number of valves in the engine. For example, Maruti came up with something called 16x4 hypertech and upgraded all their engines to feature 4 valves (2 intake, 2 exhaust) per cylinder. Therefore, Maruti 800 with 3 cylinders became 12-valve MPI and the Esteem, Wagon R, Zen became 16-valve MPI engines.

However, Hyundai stuck to 2-valves per cylinder making their engines, 8-valve MPFI engines. Even the NHC features a 8-valve, iDSI engine. Does the number of valves in the engine improve performance and fuel efficiency or is it just another tech jargon to baffle the Indian customer?

Also, there is a big uproar about the bit-length of the microcomputer that controls the engine. Hyundai, Fiat, Opel, featured 8-bit ECUs, while only Maruti featured 16-bit ECUs. However, with the dawn of Bharat Stage III, both Maruti and Hyundai (eRLX) seem to have upgraded their ECUs to 32-bit.

Hyundai seems to be beating their own drum about their latest eRLX technology that empowers their cars with a 32-bit ECU. If the eRLX, indeed, features a 32-bit ECU, making a contradiction of the sorts is the fact that when I was going through their website a couple of months back, there was a section that convincingly explained why 8-bits are more than enough for the engine ECU, obviously trying to negate Maruti's reasons for installing a 16-bit ECU.

From Hyundai India website:

8-bit or 16-bit Microprocessor?

Ever got the feeling you have compromised on something with an 8-bit microprocessor under your hood? Not really! Read on to understand what this means to you as a Hyundai owner..

What is the function of a Microprocessor under your car's hood?

New generation cars have various sensors that monitor engine performance. These include the Knock sensor, Vehicle speed sensor and the Oxygen sensor, among others. These sensors control the input parameters to the engine through 'actuators' like the fuel injector and the idle speed actuator through an ECM or the Engine Management System. The microprocessor is a part of this ECM and controls the speed at which the data is carried from the sensors to the actuators. The process speed is normally in milliseconds.

What is the difference between an 8 bit and a 16 bit microprocessor?

The difference is faster processing. A 32 bit microprocessor processes data faster than a 16 bit which processes faster than a 8 bit. Normally, the choice of the microprocessor depends on the volume of data to be processed, which in turn depends on the number of sensors used. To draw an analogy, it is like using an advanced Pentium 4 PC for your large graphic applications at work, while a simple Pentium II can fit almost your entire home computing requirements.

What difference does it make to me as a driver?

Very little. Most of the cars sold in India today have about 8 to 9 key sensors, which control about 4 to 5 actuators and a 8 bit microprocessor is more than adequate to handle this volume of data efficiently. In terms of speed of processing, a couple of milliseconds hardly make any difference to the quality of the drive or to the performance of the engine, given the above specifications.
So what your take on it? 8-bit, 16-bit or 32-bit ECUs? 2-valves or 4-valves per cylinder?

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Old 27th May 2005, 12:09   #2
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Originally Posted by DueLLeR
So what your take on it? 8-bit, 16-bit or 32-bit ECUs? 2-valves or 4-valves per cylinder?
The number of valves do make a difference if the total area of the 4 valves is greater than the 2 valves per cylinder, this improves the breathing of the engine (increases the CFM) and hence the engines tend to perform better with lower emmisions and better output (read: Volumetric efficiency).

As for the ECU's the bit's only stand for the processing power of the chips being used, however none yet knows what levels of usage of the chips processing power is directed to engine management and vehicle management. However larger bit's also mean more processing per cycle.
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Old 27th May 2005, 14:41   #3
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Yes the no. of valves does help with more easy breathing of the engine hence performance/efficiency will improve...Psycho said that already (I read it after typing the above line)

Btw Tata cars have 16-bit MPs as well..not just Marutis as mentioned in your post.
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