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Old 22nd February 2008, 01:09   #1
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Default What do manufacturers do to "Detune" their cars for indian conditions?

i had a query.When a manufacturer states that the car has been detuned from 180 to 150bhp(taking an octavia's example),what kind of parameters are changed when detuning?
Also,if we use a chip or a remap to increase the power,wouldnt that be harmful because the manufacturer has actually detuned the car due to India's bad fuel,climate conditions.
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Old 22nd February 2008, 10:01   #2
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Originally Posted by hellspawn View Post
i had a query.When a manufacturer states that the car has been detuned from 180 to 150bhp(taking an octavia's example),what kind of parameters are changed when detuning?
I will give you a gist of what came out of a lengthy discussion (more like argument) with a friend of mine who works for Ford Powertrain. We were talking about the finer points of electronic boost control. Some of this has also been confirmed by my room-mate who used to work for Holset (yes, the same jokers who manufacture turbochargers). And yet another who calibrates MY2010 Chrysler engines all day long sitting somewhere in some hick town in the midwest:

In case of turbocharged engines which use solenoid-actuated boost control, the boost map is modified to open the wastegate so that manifold absolute pressure (MAP) is kept to a safe limit with a very wide margin before knock onset. If a traditional wastegate actuator is used, the boost is calibrated by changing the spring tension of the actuator.

Usually OEM's do not exceed 1.75 bar MAP on gasoline vehicles for lack of a wide enough margin before knock onset. Even then, the use of 93 RON fuel is mandatory. Testing is also done with 87 RON fuel whereby the ECU retards the timing based on closed-loop operation (knock sensor and PPP detection via ion sensing).

When a recalibration is done for lower octane fuel, a more conservative spark advance map is used. The engine is also run leaner (yes, leaner) to keep the EGT within the operating limits of the turbine impeller material, specially when the spark is retarded by large amounts to control knock.

This is the complex answer to your question. The simple answer is, the spark advance and MAP are the main controlled parameters for what is commonly called "detuning".

Last edited by Rehaan : 23rd February 2008 at 05:27.
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Old 23rd February 2008, 22:50   #3
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So does this hold true for Naturally aspirated engines as well.
And when we go ahead and get custom code remaps etc(not targeting custom code but thats the only name i know) for turbocharger petrol/diesel engines,we are basically running a more aggressive map reducing the margin of safety.Doesnt this harm the engine?
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Old 24th February 2008, 05:52   #4
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Unless there is detonation, there is no way that the engine can be damaged.
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Old 25th February 2008, 00:32   #5
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I would say it as "Fuel Efficient" not detuned.
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Old 25th February 2008, 11:55   #6
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Quote:
Originally Posted by ananthkamath View Post
I will give you a gist of what came out of a lengthy discussion ...This is the complex answer to your question. ...
Complex or not, this is a damn good answer, @ananthkamath!!!

Maybe you could explain the driveability map to complete the picture? And how to account / cater for the different gearbox ratios?
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Old 25th February 2008, 12:01   #7
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Originally Posted by low_bass_makker View Post
I would say it as "Fuel Efficient" not detuned.
Decreasing the compression ratio will actually "reduce" the FE, not increase it, but with poor quality fuel(low octane + adulteration) having a high compression ratio would cause excessive knocking and lead to engine damage.
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Old 25th February 2008, 12:08   #8
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Quote:
Originally Posted by ananthkamath View Post
Unless there is detonation, there is no way that the engine can be damaged.
Great stuff Ananth,

What about running the engine leaner (as you mentioned) causing it to run a lot hotter, would that cause slow damage to the engine, or is the change negligible?

cya
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Old 25th February 2008, 21:38   #9
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Unless the thermal limits of the valves or the pistons are exceeded, I doubt there would be significant degradation of engine life. However I wont speculate because......see my signature LOL.

And I said that they run it leaner to keep the EGT (exhaust gas temperature) within limits to offset the retarded ignition.

The principle is LEANER = lower EGT, RETARD = higher EGT.

@tsk1979, reduction of compression ratio is an old trick. No one does that anymore. The same safety margin can be achieved only through an ECM re-calibration. Reducing compression ratio does not make economic sense for the manufacturer. Look at most Indian cars and their overseas counterparts. The compression ratio is equal or within +/- 0.5:1.

Last edited by ananthkamath : 25th February 2008 at 21:41.
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Old 26th February 2008, 14:50   #10
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I had asked the same question to RD Karthik some time back and his reply matches Ananth's description. The ignition timing is backed off, and considering that no hardware fidgeting is needed for the same, a conservative timing map does the trick without increasing costs. For turbocharged engines, manufacturers can play with the boost threshold depending on the market and the fuel widely available.
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Old 26th February 2008, 18:08   #11
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Hi ananth, how does retarding the ignition advance increase exhaust gas temperature and then how does making the mixture leaner decrease EGT ? Shouldn't both the aforementioned techniques lead to the same consequence, that is an increase in exhaust gas emission due to slightly ineffecient combustion now (since the engine is basically producing less power now).
P.S-is the increase in EGT due to an increase in the exhaust gas emissions ?

Last edited by revvedup : 26th February 2008 at 18:09.
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Old 26th February 2008, 22:44   #12
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EGT is different from emissions. EGT will increase if you retard the ignition because the ignition process starts a little later in the cycle. That is, the in-cylinder temperature is higher when the exhaust valve opens. Ergo, EGT is higher.

Its not accurate to say that leaner equals less power. Its also absolutely wrong to say leaner equals more emission. Too many other factors are involved.

Actually my previous statement that leaner = lower EGT is not fully correct, it should be modified to leaner than stoichiometric = lower EGT. This strategy is implemented at cruise conditions and small throttle openings to extend the turbine impeller's life. In an NA engine EGT is generally not an issue.
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Old 26th February 2008, 23:00   #13
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Quote:
Originally Posted by ananthkamath View Post
The principle is LEANER = lower EGT, RETARD = higher EGT.
.. it also depends on which side of the AFR u are on.
initially leaner = higher EGT till a particular AFR depending on fuel
after u go too lean u get drop in EGT.
And usually the power is to be made when the relation of leaner = higher EGT is valid.
we cant make a blanket statement that leaner = lower EGT

Last edited by chetanhanda : 26th February 2008 at 23:01.
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Old 26th February 2008, 23:51   #14
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Quote:
Originally Posted by ananthkamath View Post
EGT is different from emissions. EGT will increase if you retard the ignition because the ignition process starts a little later in the cycle. That is, the in-cylinder temperature is higher when the exhaust valve opens. Ergo, EGT is higher.

This strategy is implemented at cruise conditions and small throttle openings to extend the turbine impeller's life. In an NA engine EGT is generally not an issue.
Ok got it, and regarding EGT just had a thought that you don't need to offset it because in today's world of catalytic converters a higher EGT means less use of exotic catalysts or the need to bring the catalytic converter closer to the exhaust manifold, which will infact lower emissions so my previous post's statement about emissions is wrong.

Quote:
Its not accurate to say that leaner equals less power. Its also absolutely wrong to say leaner equals more emission. Too many other factors are involved. Actually my previous statement that leaner = lower EGT is not fully correct, it should be modified to leaner than stoichiometric = lower EGT.
Can you please elaborate about some of these factors ? I wanted to say leaner than in the stoichometric AFR but didn't use the phrase because I thought you mean't the same in your post and hence did not want to state the obvious.

Another Query In diesel engines, how do we reduce detonation ?

Last edited by revvedup : 26th February 2008 at 23:55. Reason: typo
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Old 27th February 2008, 09:44   #15
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Originally Posted by tsk1979 View Post
Decreasing the compression ratio will actually "reduce" the FE, not increase it, but with poor quality fuel(low octane + adulteration) having a high compression ratio would cause excessive knocking and lead to engine damage.
Exactly.

Plus the fact that we Indians are total morons when it comes to mechanical abilities. A very small example is looking around to see how many people will warm up the car or wait patiently for 30sec or so after starting the engine to help the engine oil work up, how many will blip the throttle hard and immediately turn off the engine. You will be surprised to count the number.
Especially in cases of turbo charged engines.

No Manufacturer is happy honouring more and more warranty claims just because they wanted to give the "Real Deal" to the public.
A detuned engine is cheap insurance.
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