Retarded Timing=Hotter Engine Why?
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Retarded Timing=Hotter Engine Why? (nunus79)
Won’t anybody talk to you?
Retarded timing causes higher temps because: It takes a certain amount of time to burn a cylinder full of fuel. At higher rpm you could have the timing retarded to the point where your actually getting fuel still on fire roaring past an open exhaust valve. To compound the problem since your not ever getting maximum pressure to push the piston down on the combustion stroke. You have to have your foot farther down on the throttle to maintain a speed on level ground so you using more fuel and getting less work out of it.
Retarded timing causes higher temps because: It takes a certain amount of time to burn a cylinder full of fuel. At higher rpm you could have the timing retarded to the point where your actually getting fuel still on fire roaring past an open exhaust valve. To compound the problem since your not ever getting maximum pressure to push the piston down on the combustion stroke. You have to have your foot farther down on the throttle to maintain a speed on level ground so you using more fuel and getting less work out of it.
Thread Starter
Drifting
Joined: Nov 2000
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From: Honolulu Hawaii
Re: Retarded Timing=Hotter Engine Why? (gkull)
Appreciate the response! Maybe folks think I got the cooties or something.
I entered into a thread about how this guy got rid of his piston slap by running 87-octane instead of his normal 92. I made a comment about how the engine would retard the timing because of the 87-octane and that the engine would run hotter because of the timing retard. Then because of the hotter engine, the piston to cylinder clearance may have tightened enough to get rid of the slap.
I then got questioned as to why timing retard would make the engine hotter. His understanding was a retarded engine would run cooler.
I entered into a thread about how this guy got rid of his piston slap by running 87-octane instead of his normal 92. I made a comment about how the engine would retard the timing because of the 87-octane and that the engine would run hotter because of the timing retard. Then because of the hotter engine, the piston to cylinder clearance may have tightened enough to get rid of the slap.
I then got questioned as to why timing retard would make the engine hotter. His understanding was a retarded engine would run cooler.
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,361
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From: Honolulu Hawaii
Re: Retarded Timing=Hotter Engine Why? (nunus79)
I DON'T HAVE COOTIES!!!
Where's all of the Forum geniuses that typically write a publishable dissertation to technical questions like this??? I understand Gkulls point, but I don't get the complete connection between late combustion heat leaving the exhaust vs. that same heat in the combustion chamber. What makes the late heat hotter than the properly timed heat?
Where's all of the Forum geniuses that typically write a publishable dissertation to technical questions like this??? I understand Gkulls point, but I don't get the complete connection between late combustion heat leaving the exhaust vs. that same heat in the combustion chamber. What makes the late heat hotter than the properly timed heat?
Burning Brakes
Joined: Sep 2000
Posts: 922
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From: Maine
Re: Retarded Timing=Hotter Engine Why? (nunus79)
I think it's more to George's point of fuel being used less efficiently. The reason gasoline is burned is to raise cylinder pressure to provide force on the piston. If the combustion process starts too late than the energy in the gas isn't being used as well as it could. To provide the same work (ex. to maintain a given road speed) you need more air (and gas) with commensurate increase in waste heat: higher temps.
Burning Brakes
Joined: Dec 1999
Posts: 845
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From: Ventura Harbor CA California
Re: Retarded Timing=Hotter Engine Why? (Frank75)
Nunus
George and Frank are right on. Here's the deal. If with a 9.5 cr your motor makes 400 hp and you lower the cr to 8.0 you would lose X hp. The weight of the vehical hasn't changed but the available power to pull it has. The idea is to start the fire just as the piston passes TDC, Optimum compression and power. If the piston travels 4 or 5 crank degrees down the hole we have lost CR and lost power and efficiency which equals more work and more heat to pull the weight.. I hope this wasn't a dissertation.
George and Frank are right on. Here's the deal. If with a 9.5 cr your motor makes 400 hp and you lower the cr to 8.0 you would lose X hp. The weight of the vehical hasn't changed but the available power to pull it has. The idea is to start the fire just as the piston passes TDC, Optimum compression and power. If the piston travels 4 or 5 crank degrees down the hole we have lost CR and lost power and efficiency which equals more work and more heat to pull the weight.. I hope this wasn't a dissertation.
Thread Starter
Drifting
Joined: Nov 2000
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From: Honolulu Hawaii
Re: Retarded Timing=Hotter Engine Why? (Bob Blackmon)
So, the explanation is too simple for a full-on dissertation. LOL
Okay, it makes sense. The engine will have to complete more revolutions to reach a given cruise rpm w/the retarded timing because of the less power per combustion stroke. Less heat being transfered into power makes for more waste heat that the engine needs to shed.
I truly appreciate all of your replies. Thank you.
Okay, it makes sense. The engine will have to complete more revolutions to reach a given cruise rpm w/the retarded timing because of the less power per combustion stroke. Less heat being transfered into power makes for more waste heat that the engine needs to shed.
I truly appreciate all of your replies. Thank you.
Safety Car
Joined: Feb 1999
Posts: 3,631
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From: Fountain Hills AZ
Re: Retarded Timing=Hotter Engine Why? (nunus79)
I've seen another explanation before that included what George said and also attributed part of the higher coolant temps to a larger area of the cylinder wall being exposed to combustion heat. This expanation stated that the later firing of the cylinder resulted in the piston being farther down the cylinder during combustion and more combustion heat was transfered through the cylinder walls.
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