Pushing the tune limits and risking engine knocking/pinging

[crackelaktor]

Having owned a highly modified and tuned WRX in 2000, the tuner (MRT Performance) always stressed the importance of not pushing the tune too far due to the risks of damage from a pinging/knocking engine. Their advice was gold and they were more on the conservative side compared to some others who didn't place the same importance on reliability. My question for our beloved HSVs, in particular the later models, is how workshop tuners detect pinging and what they do to ensure your fabulous tune doesn't slowly destroy your engine.

Whilst I will probably keep my new E3 GTS for 5-7 years, I'd like to know that I won't be up for engine repairs just because my tuner gave me the most impressive dyno graph.

Do any of you have knock sensors installed to give you a visual signal if and when your motor pings?

Btw, for those that are also part of the HSV forum, you'll see the same post there.

[LooneyR8]

It really comes down to the individual tuner as you may well be aware but all LS based engine have factory knock sensors fitted to them so you shouldnt really have to many issues.

Just use a reputable tuner and you will be fine....

[swingtan]

There are a number of ways to manage the timing applied applied by the ECM to the motor. Here's something to think about....


Knock Cans/Phones: These are, basically, headphones that amplify the sounds occurring inside the motor. As the intake charge is ignited, it makes a unique sound that the Knock Phones pick up and amplify for the dyno operator to hear. A skilled operator can tell by the sound of the ignition, when the timing is approaching the knock point. More sophisticated versions will apply a "noise gate" to the signal, only amplifying the signal at ignition time. This helps reduce background noise from lifters, valves and other moving components.
Mean Best Timing (MBT): Generally speaking, an engine will produce more power with more timing advance. That is until the the cylinder pressures rise too quickly and attempt to stop the piston from rising to TDC. At this point, timing advance starts to reduce power, even though no knock may be heard or detected. Setting the engine up on a dyno to measure the power output vs timing input will find the point where timing advance starts reducing power.
Guestimation: The LS series motor is a mass produced item that surprisingly maintains a fair amount of consistency in build quality. I'm not saying that all engines are the same, but as a general rule, they are pretty close. the amount of timing any engine can take depends on a few factors, but if all other items are the same, then engine airflow is a good indicator for ignition timing. the general rule here is that any increase in airflow allows for an increase in timing. If you combine the known or calculated airflow, the known engine configuration and feedback from logged data, you can get close to optimal timing without taking it too far.



Simon.

[HDT-EFI]

There are a number of ways to manage the timing applied applied by the ECM to the motor. Here's something to think about....


Knock Cans/Phones: These are, basically, headphones that amplify the sounds occurring inside the motor. As the intake charge is ignited, it makes a unique sound that the Knock Phones pick up and amplify for the dyno operator to hear. A skilled operator can tell by the sound of the ignition, when the timing is approaching the knock point. More sophisticated versions will apply a "noise gate" to the signal, only amplifying the signal at ignition time. This helps reduce background noise from lifters, valves and other moving components.
Mean Best Timing (MBT): Generally speaking, an engine will produce more power with more timing advance. That is until the the cylinder pressures rise too quickly and attempt to stop the piston from rising to TDC. At this point, timing advance starts to reduce power, even though no knock may be heard or detected. Setting the engine up on a dyno to measure the power output vs timing input will find the point where timing advance starts reducing power.
Guestimation: The LS series motor is a mass produced item that surprisingly maintains a fair amount of consistency in build quality. I'm not saying that all engines are the same, but as a general rule, they are pretty close. the amount of timing any engine can take depends on a few factors, but if all other items are the same, then engine airflow is a good indicator for ignition timing. the general rule here is that any increase in airflow allows for an increase in timing. If you combine the known or calculated airflow, the known engine configuration and feedback from logged data, you can get close to optimal timing without taking it too far.


Simon.

wow, that all made perfect sense....:goodjob:

[Soopy]

Its Swingtan, of course it did :P

[HYMEY]

LS engines require fairly text book tuning, same as any modern internal combustion engine. The best advice I can give you is some cylinders will be over advanced some possibly not enough due to header/intake and cylinder temps. Cylinders over timed will have the timing mark on the ground strap past the centre point and pushed further down the ground strap , half way between centre and the thread. This means negative torque is occuring and there will be black specs on the porcelain, ie detonation is occuring on this cylinder. Every LS I have tuned an you will see how much negative torque will effect hp in a big way at the track. If you pull the timing back, slip in new set of plugs and the timing marks are in the centre torque increases and the timing mark(which looks like a plate heated with an oxy torch it changes colour) will be in the centre. One thing I have noticed is as soon as that timing mark dips past the centre it will start hurting mph, this is also the same as xr6T and even RB30 turbos. The cylinder heads are very efficient and burn very fast, most big hp LS aspirated engines use around 26 degrees of ignition advance. This is also an indicator of the dynamic compression of the engine, the tuning window or how timing sensitive it is, also is a very strong indicator. engines that do not respond as well to timing change generally have poor VE, to large a camshaft for the static comp and most likely poor work on the grinder by the head porter. Engines with two high dynamics have high compression and small or stock camshaft just like a LS3. These engines are very sensitive to engine mods/timing changes/exhaust changes. On a carby engine it will simply increase the fuel to engine if airspeed passes the boosters however on an efi engine, like installing a set of 4 into 1s can lean an engine as much as 7% and put engine into detonation, so any changes make sure the tune is compensated to suit.

LS engines always do well with the right tune, there is no such thing as an aggressive tune and no need for it, you tune to the fuel being used and ambient conditions, they always do well with correct timing which is mostly 4 degrees away from audible detonation in most cases and correct conservative fuel mixtures will give you good torque and very good consistantcy.

[LuisS]

LS engines require fairly text book tuning, same as any modern internal combustion engine. The best advice I can give you is some cylinders will be over advanced some possibly not enough due to header/intake and cylinder temps. Cylinders over timed will have the timing mark on the ground strap past the centre point and pushed further down the ground strap , half way between centre and the thread. This means negative torque is occuring and there will be black specs on the porcelain, ie detonation is occuring on this cylinder. Every LS I have tuned an you will see how much negative torque will effect hp in a big way at the track. If you pull the timing back, slip in new set of plugs and the timing marks are in the centre torque increases and the timing mark(which looks like a plate heated with an oxy torch it changes colour) will be in the centre. One thing I have noticed is as soon as that timing mark dips past the centre it will start hurting mph, this is also the same as xr6T and even RB30 turbos. The cylinder heads are very efficient and burn very fast, most big hp LS aspirated engines use around 26 degrees of ignition advance. This is also an indicator of the dynamic compression of the engine, the tuning window or how timing sensitive it is, also is a very strong indicator. engines that do not respond as well to timing change generally have poor VE, to large a camshaft for the static comp and most likely poor work on the grinder by the head porter. Engines with two high dynamics have high compression and small or stock camshaft just like a LS3. These engines are very sensitive to engine mods/timing changes/exhaust changes. On a carby engine it will simply increase the fuel to engine if airspeed passes the boosters however on an efi engine, like installing a set of 4 into 1s can lean an engine as much as 7% and put engine into detonation, so any changes make sure the tune is compensated to suit.

LS engines always do well with the right tune, there is no such thing as an aggressive tune and no need for it, you tune to the fuel being used and ambient conditions, they always do well with correct timing which is mostly 4 degrees away from audible detonation in most cases and correct conservative fuel mixtures will give you good torque and very good consistantcy.

Could you elaborate a little more? :)

[swingtan]

Earth Strap: The earth electrode on the spark plug.
Timing mark: The point where you can see a change in colour on the earth electrode.


At least that's how I read it.