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Head shims?
- Thread starter Kephasd
- Start date
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MudSlinger33
Hardcore RCTalk User
Never heard of adding shims, since this would decrease compression I have a feeling it would make a troublesome engine worse. I have removed shims before and have gained some compression.
dub c
RCTalk Talkaholic
adding shims has several different effects on a nitro engine. mainly it would relate to nitro percentage and ignition timing.
When upping the nitro percentage two things change. first off is the fuel to air ratio. higher % nitro has a quicker flash, and in order to compensate this quicker flash a richer air/fuel ratio is required. so now that more fuel is entering the combustion chamber it becomes more difficult to compress. hence the need fot additional room atop the piston!
second reason and equally important. ntro engines are like diesel engines in sence that it ignights fuel in relation to compression. if compressed to soon it fires too soon.
so if your engine is running hot and tempermental, than yes by adding a thicker head shim may tone it down and give you a richer more ideal mixture.
When upping the nitro percentage two things change. first off is the fuel to air ratio. higher % nitro has a quicker flash, and in order to compensate this quicker flash a richer air/fuel ratio is required. so now that more fuel is entering the combustion chamber it becomes more difficult to compress. hence the need fot additional room atop the piston!
second reason and equally important. ntro engines are like diesel engines in sence that it ignights fuel in relation to compression. if compressed to soon it fires too soon.
so if your engine is running hot and tempermental, than yes by adding a thicker head shim may tone it down and give you a richer more ideal mixture.
MudSlinger33
Hardcore RCTalk User
You learn something new every day! Thanks for the info dub!
i have aded shims on a 3.3 to run 50-70% nitro. shims with normal % doesn't not drop hp much. it should make it easer to start, but iam not sure it does. to: dubc that is one of best descriptions of how compresion/nitro, ect work i have seen.
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if nitros flash point was 4 degrees higher it wouldnt be a flammable but would be combustable. compared to the other fuels, nitro is VERY hard to light. that why top fuel cars are started with gasoline
