Reading flow pattern

G

georgieboy

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Jan 2, 2001

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• Oct 21, 2007

• #1

Hi all,
today lifted the jug off my bike and made a picture of the piston crown and cilinderhead.
The exhaust side is top.
I have a squish gap issue. It reads 1.65mm (0.063 inch).
But i want to ask you about the flow pattern.
Which side is flowing more?

 

G

georgieboy

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Jan 2, 2001

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• Oct 23, 2007

• Thread starter
• #2

Wauw....
quite in here.
There was a time that the mods forum had the most discussions and debates.
Times change.

 

7

76GMC1500

Uhhh...

Oct 19, 2006

2,142

1

• Oct 23, 2007

• #3

That's a lot of carbon, what kind of oil are you running?

 

G

georgieboy

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• Oct 24, 2007

• Thread starter
• #4

76, Hi.
I did that on purpose to get a good showing flow pattern ;)
So you guys cld comment on that.
ps:i know it is rich.

 

7

76GMC1500

Uhhh...

Oct 19, 2006

2,142

1

• Oct 24, 2007

• #5

I've always heard modern oils burn to cleanly/have too much detergent to give a good flow pattern on the piston crown.

 

G

georgieboy

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• Oct 26, 2007

• Thread starter
• #6

That is why i runned it rich ;)

 

Rich Rohrich

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• Oct 26, 2007

• #7

The only useful thing you can read from those pictures is how horribly rich (and slow) this engine is running.

Until you sharpen up the jetting you won't read much of value by looking at the piston crown or cylinder head.

 

7

76GMC1500

Uhhh...

Oct 19, 2006

2,142

1

• Oct 27, 2007

• #8

There is a burn pattern on the crown on my old piston. I couldn't tell you exactly what I did to get it. I Scotchbrited most of the old carbon off and ran the bike for a short time before I decided the piston was trashed and replaced it. I haven't pulled the head on the new piston yet so I couldn't tell you how that one looks. I've never had any carbon whatsoever on the underside of the head, you probably shouldn't either.

 

G

georgieboy

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• Oct 27, 2007

• Thread starter
• #9

I already said it was rich jetted.
My question was about the flow, but nobody wants to say anything about my flow pattern :(

 

Rich Rohrich

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• Oct 27, 2007

• #10

georgieboy said:

My question was about the flow, but nobody wants to say anything about my flow pattern :(

Click to expand...

That's because it is MEANINGLESS until you get the tuning correct.:bang:

When you sharpen the jetting you speed up the rate of combustion as well as increasing the piston crown and combustion chamber temperatures. The scavenging will be influenced by these changes and with it the pattern that is left behind.

You are wasting your time, and by association our time by chasing your tail here. :coocoo:

 

G

georgieboy

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• Oct 28, 2007

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• #11

Ahh Mr Rohrich, i knew in the end i wld recve an answer that i cld live with.
Sorry i wasted yr time, but since the only comment was: yr jetting is rich and for the rest no explaination with it, i assumed that nobody read my question in the first place.
So scavenging is related with temperatures. I thought that scavenging was related with motor-layout and rpm's.

 

Rich Rohrich

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• Oct 28, 2007

• #12

georgieboy said:

I thought that scavenging was related with motor-layout and rpm's.

Click to expand...

Scavenging is related to that as well. It's a complicated process that can be influenced by a lot of seemingly insignificant things.

 

G

georgieboy

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• Oct 29, 2007

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• #13

Ok won't take anymore of yr time to debate flow patterns.
Will look at the bigger picture and solve the richness in combination with getting the ports open symmetrically. Leave it with that... for now ;)
Thnks for yr patience.

 

Rich Rohrich

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• Oct 29, 2007

• #14

georgieboy said:

Will look at the bigger picture and solve the richness in combination with getting the ports open symmetrically. Leave it with that... for now ;)

Click to expand...

It's definitely a system and there are a lot of interactions that need to be considered. Going at it in a step by step way will get you the most useful info.

Eric Gorr and I flowed hundreds of cylinders on a special flow bench setup we built. Over the years using this equipment to try and balance transfers had some value, but only if the time/area and the rest of the scavenging process is optimized as well. Dwelling on flow patterns alone makes for some interesting nights in the shop but aren't likely to show much on the racetrack. ;)

 

G

georgieboy

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• Oct 29, 2007

• Thread starter
• #15

That is why i stay away from doing something drastic to a nice looking cilinder and head, other than matching everything together ;)
But i agree it is tempting to do something real cool like changing the angles or so.
Anyway, thx for the replies and help.
You surely advised me good with that decel knocking topic.

 

bclapham

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• Oct 29, 2007

• #16

Rich Rohrich said:

It's a complicated process that can be influenced by a lot of seemingly insignificant things.

Click to expand...

arent most things in life! :yell:

 

Rich Rohrich

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• Oct 29, 2007

• #17

bclapham said:

arent most things in life! :yell:

Click to expand...

So it seems. :nod:

 

M

mtk

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Jun 9, 2004

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• Oct 31, 2007

• #18

Stick to something simple then, like women. ;)