Engine capacity increase, wilder cam?

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23-02-2007, 10:18 AM
Mr_will

Quote:

Originally Posted by honest muz

Mr_Will,
It's not as simple as just increase duration and height.
Think about bore and stroke of each engine. Are they comparable? Is one a stroked version of the other? Think about what gas flow characteristics are getting the best scavenging. Need x-ray specs here. You should checkout the following site that says better scavenging can be had from smaller ports. How does that fit with higher lift/duration?
http://www.mototuneusa.com/break_in_secrets.htm

like i said, not claiming to be an expert at all.
btw it was me who gave you that little red square :)
23-02-2007, 01:35 PM
ZeForce

Quote:

Originally Posted by honest muz

Think about bore and stroke of each engine. Are they comparable? Is one a stroked version of the other?

Thats right, small engine's with high rod/stroke ratio need cams with more overlap to take advantage of the scavenging effect, since they have low piston speeds. With a good header and exhaust system the exiting exhaust gases will create a low pressure area at the exhaust valve and if the intake valve is open at the same time the vacuum will actually help suck in the next lot of air and increase volumetric efficiency. Bigger engine's with lower rod/stroke ratios have higher piston speeds/acceleration and need cams with less overlap, or you might be able to dial some of the overlap out with a set of adjustable cam gears. If you have a bigger displacement engine with same geometry as the smaller displacement then there shouldnt be a need for a "larger" cam....

"So here we have a small engine vs. a large engine which have bore / stroke ratios that are identical at 1.14-1, and rod length to stroke ratios which were also equal at 1.75-1, so geometrically they were equal, and the cam (valve timing) identical, but the big engine didn't appear to me to need a cam with more lift or duration." -The Old One (Larry Widmer)

This is my understanding so far, correct me if Im wrong.....
23-02-2007, 07:39 PM
tinkerbell

Quote:

Originally Posted by ZeForce

Thats right, small engine's with high rod/stroke ratio need cams with more overlap to take advantage of the scavenging effect, since they have low piston speeds.

why did honda not change cams between B16A and B18C?

With a good header and exhaust system the exiting exhaust gases will create a low pressure area at the exhaust valve and if the intake valve is open at the same time the vacuum will actually help suck in the next lot of air and increase volumetric efficiency. Bigger engine's with lower rod/stroke ratios have higher piston speeds/acceleration and need cams with less overlap,

why is this?

or you might be able to dial some of the overlap out with a set of adjustable cam gears. If you have a bigger displacement engine with same geometry as the smaller displacement then there shouldnt be a need for a "larger" cam....

the point is more power, so who cares what it *shouldn't have a need for*

"So here we have a small engine vs. a large engine which have bore / stroke ratios that are identical at 1.14-1, and rod length to stroke ratios which were also equal at 1.75-1, so geometrically they were equal, and the cam (valve timing) identical, but the big engine didn't appear to me to need a cam with more lift or duration." -The Old One (Larry Widmer)

pity larry aint talking about a B honda...

This is my understanding so far, correct me if Im wrong.....

my experience = ITR cams in B20VTEC = more power
24-02-2007, 01:13 AM
ZeForce

Quote:

Originally Posted by tinkerbell

why did honda not change cams between B16A and B18C?

They did.

why is this?

Which part were you refering to?

the point is more power, so who cares what it *shouldn't have a need for*

True, but the question was "would the B20 with B16A cams but all the other work still generate enough power/torque at the 8000rpm mark?"

pity larry aint talking about a B honda...

Does that really matter? The basic principles would be the same

my experience = ITR cams in B20VTEC = more power

Im sure they would and I never said otherwise
24-02-2007, 01:44 AM
ZeForce

Quote:

Originally Posted by claymore

Air fuel mixture is not "Sucked" into any engine..... they are forced in by outside air pressure which is higher then the air pressure in the cylinder which is lower. Air always moves toward lower pressure. You said correct me if I'm wrong:angel:

http://en.wikipedia.org/wiki/Suction

Suction or to "suck" is the creation of a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area.

Thanks for trying though....
24-02-2007, 06:28 PM
ZeForce

Quote:

Originally Posted by claymore

"The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area."

Thanks for not having any reading comprehension.

lol dude your post makes no sense.....

"The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area."

....this is the very definition of "suck", which means I did actually use it in the correct context and didnt need you to correct me.
24-02-2007, 08:01 PM
TODA AU

Quote:

Originally Posted by ZeForce

lol dude your post makes no sense.....
"The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area."
....this is the very definition of "suck", which means I did actually use it in the correct context and didnt need you to correct me.

If you read his post again, you will see it makes perfect sense.
Example:
If you are in an aircraft pressurised to 10,000ft, flying at 40,000ft.
Should a hole open in the side of the aircraft,
By your thinking you are sucked from the aircraft.
In reality, you would in fact blown from it. (Greater pressure in the craft)
Though it really is a perspective thing, physics is on Claymore's side.
The same applies from global weather paterns to internal combustion engines...
(Just my 2c worth)

Also... For the previous argument with Tink
Originally Posted by tinkerbell http://www.ozhonda.com/forum/images/...s/viewpost.gif
why did honda not change cams between B16A and B18C?
They did.
Actually they didn't... Only Type R is different (in the Vtec lobe only)

Regarding the B20 with the quads etc...
Regardless of theory,
Reality is a set of larger cams will work & work really well.
25-02-2007, 01:18 PM
ZeForce

Quote:

Originally Posted by TODA AU

Also... For the previous argument with Tink

No arguing, just friendly discussion

Quote:

Originally Posted by TODA AU

why did honda not change cams between B16A and B18C?
They did.
Actually they didn't... Only Type R is different (in the Vtec lobe only)

Crower seems to disagree.... http://www.crower.com/cat/import/hon...s/b_vtec.shtml
25-02-2007, 07:06 PM
Edgeauto

With a similar set up to yours we gained 6Kw by repalcing the standard B18c cams with ITR ones then another 3Kw peak and 10kw in the midrange with a tune:)
26-02-2007, 09:35 AM
honest muz

Quote:

Originally Posted by ZeForce

http://en.wikipedia.org/wiki/Suction

Suction or to "suck" is the creation of a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area.

Thanks for trying though....

Giday ZeForce,
Great posts, and that needs to be said!:wave:

I don't know why some of the above posters get so antagonistic when detail gets added to a post. It's got me F^(#&@!:o

Anyway, here's a starting point for you hyper-ventilating knockers....suck it up, it's wiki!!

http://en.wikipedia.org/wiki/Harry_Ricardo
26-02-2007, 09:59 PM
tinkerbell

ZeForce,

Quote:

Originally Posted by tinkerbell

pity larry aint talking about a B honda...

Quote:

Originally Posted by ZeForce

Does that really matter? The basic principles would be the same

hmmm, probably not the same - with an engine with Variable Valve Timing and Lift Electronic Control feature...

plus, we are comparing a B20B to a B16A...

these are not identical engines so NO the basic principles are VASTLY different:

B16A bore/stroke = 1.05
B20B bore/stroke = 0.94

B16A rod/stroke = 1.74
B20B rod/stroke = 1.53

one is "oversquare"
one is "undersquare"

simply "uncomparable" in regards to *breathing* requirements...

and since you love wikipedia -

http://en.wikipedia.org/wiki/Stroke_ratio

and regarding your crower stuff - i'd trust TODA AU over the Crower website ;)
26-02-2007, 10:35 PM
ZeForce

Quote:

Originally Posted by tinkerbell

plus, we are comparing a B20B to a B16A...

these are not identical engines so NO the basic principles are VASTLY different:

B16A bore/stroke = 1.05
B20B bore/stroke = 0.94

B16A rod/stroke = 1.74
B20B rod/stroke = 1.53

one is "oversquare"
one is "undersquare"

simply "uncomparable" in regards to *breathing* requirements...

Very true and I do actually agree. I was simply trying to point out to the thread starter that its not the increase in displacement which requires a bigger/different cam specs but in fact the change in the engines geometry....

Quote:

Originally Posted by tinkerbell

and since you love wikipedia -

http://en.wikipedia.org/wiki/Stroke_ratio

Don't patronise me....

Quote:

Originally Posted by tinkerbell

and regarding your crower stuff - i'd trust TODA AU over the Crower website ;)

Check this out as well its from a completely different source.

http://www.myfilehut.com/userfiles/5...am%20Specs.gif

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