EGT and timing
08-07-2002, 08:54 PM
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EGT and timing
Can someone explain why retarding the timing will raise the EGT? My first thought is that the opposite would happen, since you would be getting further away from detonation, correct?
08-07-2002, 10:21 PM
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Re: EGT and timing (ion_four)
Detonation occur when you ignite too early which while piston is still coming up to TDC and you start the power stroke which forcing it to come up. Then you break rods, pistons, and some times things fly out.
Preignition occurs when anything besides the commanding spark plug is ignition the fuel. ( hot spots on the spark plug, piston residues, anything small, sharp that get heat up red and able to ignite.)
In theory, EGT climbs high due to too much retarding or late ignite process. Unburnt fuel exiting the compression stage because of late ignition and get lit up near the egt probe while fuel behind it is igniting.
Preignition occurs when anything besides the commanding spark plug is ignition the fuel. ( hot spots on the spark plug, piston residues, anything small, sharp that get heat up red and able to ignite.)
In theory, EGT climbs high due to too much retarding or late ignite process. Unburnt fuel exiting the compression stage because of late ignition and get lit up near the egt probe while fuel behind it is igniting.
08-08-2002, 12:05 AM
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Re: EGT and timing ([Evo]Hybrid)
thanks, but I don't think that's what I was looking for. It just seems to me that unburnt fuel would have a cooling effect on the egt...if the fuel isn't being burnt in the combustion chamber, doesn't that mean that the cylinder temps are lower?
08-08-2002, 12:34 AM
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Re: EGT and timing (ion_four)
An engine is being dyno tested , and is tuned to its best
and proper Air/Fuel Ratio , and its EGT is recorded .
If for some reason , the distributor came loose, and
ignition timing went retarded, the EGT would also "skyrocket"
All it did was start burning the same correct A/F Ratio later
and was continuing to burn as it went out exhaust ports
as you were pretty much wasting it and sort
of blow-torching the EGT probes.
[Modified by [Evo]Hybrid, 10:09 AM 8/8/2002]
and proper Air/Fuel Ratio , and its EGT is recorded .
If for some reason , the distributor came loose, and
ignition timing went retarded, the EGT would also "skyrocket"
All it did was start burning the same correct A/F Ratio later
and was continuing to burn as it went out exhaust ports
as you were pretty much wasting it and sort
of blow-torching the EGT probes.
[Modified by [Evo]Hybrid, 10:09 AM 8/8/2002]
08-08-2002, 01:14 AM
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Re: EGT and timing (ion_four)
basically, you must remember not all of the air fuel mixture burns inside of the combustion chamber - this is normal. Retarding the ign timing causes less of the mixture to be burnt inside the chamber, and thus is still burning when pushed out the exhaust side. This is one way EGT's are affected by timing. I've posted many many explanations of EGT's here, so I won't go any further. Here's an excellent link about EGT's. Read and learn
https://honda-tech.com/zerothread?id=248965
[Modified by VaporTrail, 5:27 AM 8/8/2002]
https://honda-tech.com/zerothread?id=248965
[Modified by VaporTrail, 5:27 AM 8/8/2002]
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