Erdin

Hi can some off you more knowledgeable guys help me understand what happends with the Egt when you add or retard timing.

Thankfully
Erdin

Jeff20B

iTrader: (13)

I think the exhaust heats up when you retard timing.

Erdin

Thanks for the reply Jeff and why does this happen and what will happen if you advanced the timing.

forcefed1

ok Ill take a stab. the more timing you run. the more time there is to convert the heat energy of the combustion into torque. so more advance on the timing adds up to more torque because of higher combustion pressures from the greater heat. this is good to a point. on a turbo car that point is changed quite a bit by the earlier onset of knock caused by the higher compression from the boost.
the less timing you run, the less time there is for the heat to be used to produce torque. and the hotter your exhause will run as a result of more heat being pumped into it. a rapid rise in EGTs can sometimes mean flames are burning in the exhaust as the timing was so late the mixture is still burning upon exiting the engine.
DON"T forget, AFR plays into EGTs a lot also. leaner is more power and hotter.

Im not very clear about what I have stated above. Im actually intrested in some other collected answers and elaborations on this topic.

Erdin

Thanks Forcefed for the reply i have also red up on some of the other answers but was not shur but your reply helped.

Thanks
Erdin

RETed

As ignition timing is advanced, EGT will increase and stabilize. Once timing goes into detonation, the EGT's will skyrocket due to the uncontrolled combustion.

Retarding timing will cool EGT's to a point. If there is extreme ignition timing retard, fuel starts burning out the exhaust and EGT's will skyrocket - this will look almost identical as overly advanced ignition timing. If you have a very responsive EGT gauge and a sharp eye, you'll see a slight dip in the EGT prior to the temps start to climb. Also, this type of increasing EGT is slightly slower than advanced/detonation type of EGT increase.

To discern between the two condition, I use a cheapie AFR gauge to read gross rich/lean conditions. This will immediately tell me which is which.

Also, it is possible to damage a motor with excessively retarded timing, as the burning mixture out the exhaust shakes the internals enough to cause a seal failure. We've done this before...


-Ted

Erdin

Thanks alot Ted i i understand now alot better.

Thanks
Erdin