oakey

Well-Known Member

Full Member

• Aug 24, 2021

• #41

To go from No. 1 TDC on power stroke to No.1 TDC on power stroke ie one rev of the engine requires two turns of the crankshaft

 

marjon

Well-Known Member

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• Aug 24, 2021

• #42

kermit_rr said:

The rev counter counts how many times the crank turns in a minute

Click to expand...

All the way round

J

 

kermit_rr

Very

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• Aug 24, 2021

• #43

Just to be really annoying, the engine doesn't actually turn!! Unless it's an old plane engine

 

marjon

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• Aug 24, 2021

• #44

oakey said:

To go from No. 1 TDC on power stroke to No.1 TDC on power stroke ie one rev of the engine requires two turns of the crankshaft

Click to expand...

sorry no.

J

 

oakey

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• Aug 24, 2021

• #45

kermit_rr said:

The rev counter counts how many times the crank turns in a minute

Click to expand...

OK, I didnt know that but that is not engine revs

 

marjon

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Full Member

• Aug 24, 2021

• #46

kermit_rr said:

Just to be really annoying, the engine doesn't actually turn!! Unless it's an old plane rotary engine

Now let’s not start on rotaries.

J

Click to expand...

 

kermit_rr

Very

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• Aug 24, 2021

• #47

A revolution is 360 degrees

 

oakey

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• Aug 24, 2021

• #48

Oh yes it does
Ooops wrong season

 

kermit_rr

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• Aug 24, 2021

• #49

kermit_rr said:

A revolution is 360 degrees

Click to expand...

Not 720

 

kermit_rr

Very

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• Aug 24, 2021

• #50

kermit_rr said:

Not 720

Click to expand...

A single 4 stroke cycle is 2 revs

 

T

tomcat59alan

Well-Known Member

• Aug 24, 2021

• #51

Rpm is the number of times the crankshaft turns along its longitudinal axis per minute and is double the number of power strokes on a four stroke engine and the same on a two stroke.

 

oakey

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• Aug 24, 2021

• #52

kermit_rr said:

A single 4 stroke cycle is 2 revs

Click to expand...

Yes it is
But engine revs are not crank revs but I am not sure what the rev counter measures
Is a single cycle not an engine revolution?

 

marjon

Well-Known Member

Full Member

• Aug 24, 2021

• #53

oakey said:

To go from No. 1 TDC on power stroke to No.1 TDC on power stroke ie one rev of the engine requires two turns of the crankshaft

Click to expand...

Its revolution of crankshaft, not a complete 4 stroke cycle.

J

 

oakey

Well-Known Member

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• Aug 24, 2021

• #54

I agree with Alan and a cycle is a power stroke to power stroke and if the rev counter measure cycles eg no. 1 spark to no 1. spark then that is two crank revs.
Ignore the redundant spark bit

 

kermit_rr

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• Aug 24, 2021

• #55

Now about my target engine speed being 4x actual..

 

oakey

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• Aug 24, 2021

• #56

Is one engine rev not a full cycle>
In old days the rev counter was taken from the spark which would be one rev of engine

 

kermit_rr

Very

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• Aug 24, 2021

• #57

I still think i should tap the crank sensor.. what's the worst that could happen, another wrong value? Surely i won't fry anything..

 

oakey

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• Aug 24, 2021

• #58

I have no idea where the 4x comes from

 

kermit_rr

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• Aug 24, 2021

• #59

oakey said:

Is one engine rev not a full cycle>
In old days the rev counter was taken from the spark which would be one rev of engine

Click to expand...

There were several ways to measure revs.. spark being one of them, but the electrical gubbins that measured the spark, adjusted the value to actual RPM

 

kermit_rr

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Full Member

• Aug 24, 2021

• #60

oakey said:

I have no idea where the 4x comes from

Click to expand...

Nor me unless it just 'looks' 4x to the eye