When you fire your ign too advanced you effectively ignite the air/fuel mixture in the cylinder too early.. e.g. when the piston is still on its upward stroke.
This can result in increased heat as effectively you are igniting an explosion in the cylinder but then your compressing it because it's ignited too early and the piston is still moving up!
This can cause an uneven flame front in that explosion or it can pre ignite anyhow as a result of that compression causing hot spots on the piston crown.
Often a clear sign of this kind of thing on an exhaust gas temp gauge is the temps rising significantly but the car doesn't feel faster or make any more power on a dyno.

That's my understanding as such. I might have it wrong but essentially ign timing is paramount because if you are too advanced you don't make power but a bundle of heat and potentially pre ignition in the chamber and too late you just make no power anyhow and the car feels flat and dull.

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You want to advance ignition timing to make the combustion more complete (fuel and air are more compressed).
Being under the knock limit it will make more torque because more energy is released.
But more energy means also more heat.
So yes, your engine may run too hot without knocking.

 

Advancing ignition timing increases engine temperatures. As you increase towards MBT you get more power but temperatures may get so high that you melt a through the combustion temperature + compression increasing temperatures. You may also end up causing knock as the heat causes the flamefront to start forming away from the spark which causes pressure spikes that can shock load components to failure.

Pre-ignition is when the engine "diesels" and excessively high temperatures can lead to this. No amount of spark timing adjustment can prevent this, just AFR.

EGTs actually rise as you retard ignition timing as less fuel is burned before exhaust begins. Low (rich) AFRs will also cause high EGTs as the fuel hits the catalytic converter or fresh air and burns on contact.

Over-advancing your timing past MBT is never a good thing. You lose power and if you don't have knock every degree of advance will bring you closer to the knock threshold.

As a general rule if you are not knock-limited, you should advance timing to MBT and then back off until you lose ~3-5% torque. It will be just at the edge of perceptible loss and reduces the chances that you over-advance or start knocking in hot conditions.

I'm just a casual tuner though. Someone with real experience will probably chime in and prove me wrong.

 

I’m a licensed A&P and I approve of this msg. Release temperature increases (exhaust temp) from unburnt fuel (afterburne) in a rich mix or slow engine (retarded timing). Both can be used to lower engine operating temperature.
Inversely, advancing timing to the correct amount will increase engine operating temperature while decreasing exhaust gas temperature. It varies by how much the temps will change because timing isn’t the only factor in engine temperature at that point.
So what can we discern from all this relevant information so that it becomes useful in your circumstance? If she’s too hot either increase the fuel to air ration (run it rich- recommended). Better to have and not need if you want to go fast- cool, or change the thermostat to one that opens at lower operating temperatures. Lol- I didn’t even look at how old this was before I posted but hopefully this helps someone.

 

In my practical experience engine temp goes up as ignition is retarded the reason for this is you are releasing the same amount of energy but instead of converting into useful energy it is wasted as heat out of the exhaust valve which is why temperature goes up

 

In the automotive industry it is also common practise to add ignition retard during cold start to aid warm up of the engine

 

Thanks for all the replies.
Basically my engine has no knock on the dyno although it is making good power.
The only issue is the engine runs hotter than previously before it was retuned to a more aggressive ignition timing.
May have to discuss with the tuner to retard the timing a notch probably and see if it gets better.

 

If you're reading EGTs for engine temperature pulling timing will increase EGTs, not the other way around. Advancing timing will likely cause your coolant + oil temps to go up.

If you are very worried about overheating/melting something consider water injection. Just a single port after the intercooler will see some gains although due to the plenum design you're going to see uneven flow between each cylinder if you don't do port injection.

 

interesting proposition ...
but it does not solve the underlying problem if there is any. probably something to consider after I get the temp to a more reasonable level...

will keep this in mind.

Will need to read up on water injection though cos I have no knowledge how it works and where to inject...

 

I am surprised no one has said this sooner but if the difference between retarding or advancing your timing a few degrees is causing you a cooling issue there is something much more fundamental wrong with your car.

I think it is more likely advancing the ignition has caused slight head gasket damage or crack to open in the cylinder head which you are now seeing as overheating.

I have zero confidence you will fix this by changing the ignition timing.

 

That's a fair point. I was assuming that temperatures are within spec but noticeably increasing. An increase in water/oil temps beyond expectation would suggest something else.

 

Just seen this thread, slightly off topic but, had injectors cleaned and engine seems to be running hotter and leaner for some reason, checked timing and spot on. Was running NGK 7 plugs, just changed to 8's, will need to see if makes a difference. would cleaned injectors make a difference like that?
Also idle speed slightly increased, Confused????

 

Agree with most of what has been said above.

Advancing ignition reduces EGT.

Increasing the air/fuel ratio will cool the charge and reduce cylinder temps.

Might be that your water thermostat, or your water pump is on the way out / need upgrading and you are blaming the mapping for something mechanical that needs changing.

 

Just because one factor to consider hasn't been mentioned here - adding timing generally reduces EGT and general core engine temperature, HOWEVER this is on the assumption that everything has been done "properly"... ie, when the timing has been added the engine health and operation has been monitored to ensure combustion is stable and the engine is holding the cylinder pressures correctly.

Detonation (which often results from over-advanced timing) CAN cause the engine temperature to go up, so can the head lifting - even if there is strictly speaking no detonation. Both of those things can be caused by increasing the timing from a point where the engine was previously happy to maintain temperature.

 

Thanks folks for the replies.
Was away for holiday the past few weeks.
We are changing the water pump pulley to that from a Z32, hopefully the coolant flow will be better with the smaller pulley.
My engine is only 6 months new, so I do not think there is any problem with the engine or the parts.
If changing to a smaller pulley does not solve the issue, I will probably need to look for another tuner to retune the map and see what happens.
Will keep this thread updated after I replaced the pulley.

My Ignition table ... there is no knocking or whatsoever

 

I am experiencing high coolant temps - can go up to 105 deg C if stationary for some time.

EGTs stay nice and low though.

 

very similar to my situation I reckon. high coolant temp only when the car is idling and stationary, or crawling in traffic...

no problem when cruising or when on boost ...

 

Will your heaters on max hot bring down engine temp in traffic? If it will I'd check the core of the rad for blockages, my alu rad furred up when it had been left drained during a rebuild I think. It just kept running hot but the rad appeared to be working, hot on the in and cooler on the out but what you can't check is the flow rate.
I took the big windmill off the front of my rb26 and bolted a 16" through the core of a new alu rad. The sand which oil heater went in favour of an oil to air cooler between the ic and ac condenser rad. Without a stat it was about 42deg at 70 mph, with a stat it's 80deg as is the water temp. And they warm up faster from cold too.:thumbsup:

 

Nice post,

Good information is always a help, even if there is a bit of time elapsed between posts - so great contribution.

Not familiar with the term A&P though.

"inversely, advancing timing to the correct amount will increase engine operating temperature while decreasing exhaust gas temperature" is an important point, well made and not one that is always easy to understand.

 

Thanks, I appreciate it! Good to know my time wasn’t wasted. A&P is short for Airframe & Powerplant (some just have the A or the P) It’s a licensed certification you must hold to work on airplanes and return the aircraft to service. The school you have to go to is a 28hr week, year and a half long that culminates with a written and practical test. Shits no joke buddy, I spent more hours “ass in chair” than it takes to get Bachelors Degree.