Edit: Read the whole post before so you full understand whats being asked here. There is a misunderstanding by what is actually being asked.

I did search and came up with nothing regarding the design, all i found was the specs on the duration and lift. My question is....what is the exact purpose of the primary and secondary lobes being different.

In other words why does one valve in the same cylinder have a different lift and duration then the other? I know none of you are honda engineers , but i was hoping someone might have a suggestion or even correct answer for me.

Thanks in advance


Modified by Jon D at 10:32 AM 11/4/2005

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jon D &raquo;</TD></TR><TR><TD CLASS="quote">In other words why does one valve in the same cylinder have a different lift and duration then the other? </TD></TR></TABLE>
vtec?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jon D &raquo;</TD></TR><TR><TD CLASS="quote">I did search and came up with nothing regarding the design, all i found was the specs on the duration and lift. My question is....what is the exact purpose of the primary and secondary lobes being different.

In other words why does one valve in the same cylinder have a different lift and duration then the other? I know none of you are honda engineers , but i was hoping someone might have a suggestion or even correct answer for me.

Thanks in advance </TD></TR></TABLE>

im guessing to better control the air intake under vtec.....ever see how vtec-e works?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Willard &raquo;</TD></TR><TR><TD CLASS="quote">
vtec?</TD></TR></TABLE>

i guess i should have clarified that further...... primary and secondary, not vtec. Or are the two smaller lobes considered primary and vtec secondary? What i ultimately want to know is why is there a difference in size between the two smaller lobes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jon D &raquo;</TD></TR><TR><TD CLASS="quote">Or are the two smaller lobes considered primary and vtec secondary?</TD></TR></TABLE>

That's it.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jon D &raquo;</TD></TR><TR><TD CLASS="quote">What i ultimately want to know is why is there a difference in size between the two smaller lobes.</TD></TR></TABLE>

I didn't know there was a difference in the two primary lobes per cylinder. Interesting.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 330R &raquo;</TD></TR><TR><TD CLASS="quote">

That's it. </TD></TR></TABLE>

so why the difference in size of the primary lobes?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jon D &raquo;</TD></TR><TR><TD CLASS="quote">

so why the difference in size of the primary lobes?</TD></TR></TABLE>

I'll have to research this.

 

arent the intake and exhaust valves different sizes?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Crx Jimmy &raquo;</TD></TR><TR><TD CLASS="quote">arent the intake and exhaust valves different sizes?</TD></TR></TABLE>

yes i intakes are 33mm and exhausts i believe are 28mm

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Crx Jimmy &raquo;</TD></TR><TR><TD CLASS="quote">arent the intake and exhaust valves different sizes?</TD></TR></TABLE>

I understand that, intake valves are larger bc air thats not combusted has more volume then air that has been combusted!

 

Jon D - Are you talking about a difference in size of the two primary lobes per cylinder on one particular camshaft (for example, on the intake cam), or are you talking about a difference between the intake camshaft and the exhaust camshaft primary lobes?

I was taking your question to be about differences found on one camshaft.

edit: post above this one answered my question.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 330R &raquo;</TD></TR><TR><TD CLASS="quote">Jon D - Are you talking about a difference in size of the two primary lobes per cylinder on one particular camshaft (for example, on the intake cam), or are you talking about a difference between the intake camshaft and the exhaust camshaft primary lobes?

I was taking your question to be about differences found on one camshaft.

edit: post above this one answered my question.</TD></TR></TABLE>

i think hes talking about on one shaft

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by projectTeG &raquo;</TD></TR><TR><TD CLASS="quote">

i think hes talking about on one shaft</TD></TR></TABLE>

YES ..... he is! One cam one cylinder!

 

Why have both intake valves on one cylinder opening at different lift and duration? What purpose does this serve?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jon D &raquo;</TD></TR><TR><TD CLASS="quote">

YES ..... he is! One cam one cylinder! </TD></TR></TABLE>

Thought so, just making sure.

Well, looks like I'm wrong about the "primary, secondary" lobes. Jon D had it right.

Looking at an Integra service manual (from '96 so no B18C5 specs), it lists the following for the B18C1's cams:

cam lobe height
IN.........Primary.........33.411 (1.3154)
............Mid................36.377 (1.4322)
............Secondary.....34.547 (1.3601)

EX........Primary..........33.111 (1.3036)
............Mid................35.720 (1.4063)
............Secondary......34.381 (1.3536)


Sooo.. Mid would be VTEC, obviously, looking at the measurements. This shows the two smaller non-VTEC lobes are different sizes. Why? hmmm

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 330R &raquo;</TD></TR><TR><TD CLASS="quote">

Thought so, just making sure.

Well, looks like I'm wrong about the "primary, secondary" lobes. Jon D had it right.

Looking at an Integra service manual (from '96 so no B18C5 specs), it lists the following for the B18C1's cams:

cam lobe height
IN.........Primary.........33.411 (1.3154)
............Mid................36.377 (1.4322)
............Secondary.....34.547 (1.3601)

EX........Primary..........33.111 (1.3036)
............Mid................35.720 (1.4063)
............Secondary......34.381 (1.3536)


Sooo.. Mid would be VTEC, obviously, looking at the measurements. This shows the two smaller non-VTEC lobes are different sizes. Why? hmmm</TD></TR></TABLE>

my only guess would be for the major function of vtec...for economy. smaller lob=less air= less gas . any of yal heard of vtec-e before?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by projectTeG &raquo;</TD></TR><TR><TD CLASS="quote">

my only guess would be for the major function of vtec...for economy. smaller lob=less air= less gas . any of yal heard of vtec-e before?</TD></TR></TABLE>

Yes, this difference in lobes seems to be a method to stagger the air entering the combustion camber during non-VTEC operation. It's almost like while inhaling through your nose you block one nostril while still inhaling through the other.

Maybe that's the thing - it's almost like having 1.5 intake valves per cylinder when not in VTEC.

About VTEC-E.. it's been a long time since I read anything about that system. I know it's purely for economy and was found in the Civic VX. I'd have to revisit it.


Modified by 330R at 11:03 PM 11/3/2005

 

So in reality, Honda screwed us into thinking we had 4 valves per cyl when we only have 3....?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HondaHemp &raquo;</TD></TR><TR><TD CLASS="quote">So in reality, Honda screwed us into thinking we had 4 valves per cyl when we only have 3....?</TD></TR></TABLE>

Haha nooo, it's just that one intake valve stays open a little longer than the other, but they both open.

 

i believe and correct me if im wrong but i think it has something to do with it helping to create a swirling affect in the cylinder to help mix the air and fuel... and also i think it has something to do with how the air echoes through the manifold and the head before entering the cylinder... like majority of the air is focused towards the valve with higher lift and duration

 

I almost feel like making a cam that has the same lift and duration for both valves just to see what the effects are. Would be interesting. What do you think?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 330R &raquo;</TD></TR><TR><TD CLASS="quote">

Yes, this difference in lobes seems to be a method to stagger the air entering the combustion camber during non-VTEC operation. It's almost like while inhaling through your nose you block one nostril while still inhaling through the other.

Maybe that's the thing - it's almost like having 1.5 intake valves per cylinder when not in VTEC.

About VTEC-E.. it's been a long time since I read anything about that system. I know it's purely for economy and was found in the Civic VX. I'd have to revisit it.


Modified by 330R at 11:03 PM 11/3/2005</TD></TR></TABLE>

i know that the non tsx k24 engines and the k20a3's have a version of vtec-e(i believe its i-vtec e) it was also in the feiro 3-stage vtec d15b right?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by whiteJDMdc2 &raquo;</TD></TR><TR><TD CLASS="quote">i believe and correct me if im wrong but i think it has something to do with it helping to create a swirling affect in the cylinder to help mix the air and fuel... and also i think it has something to do with how the air echoes through the manifold and the head before entering the cylinder... like majority of the air is focused towards the valve with higher lift and duration</TD></TR></TABLE>

That's what it sounds like to me, too.

From just reading up on VTEC-E, it's like implementing a less extreme variation of it for the DOHC VTEC engine.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">A VTEC-E engine has two different intake cam profiles. At low RPMs, each intake valve works from its own intake cam profile. One of the intake cam profiles is very normal looking. The other one, however, is almost perfectly round, with just enough profile to it so that it pushes the valve open just enough to avoid pooling of fuel above the valve lip. Therefore at low RPM, only one intake valve is opening and closing. Most of the intake fuel and air are squeezed through this one valve, resulting in a good swirling effect in the cylinder. The swirling effect optimizes the fuel/air mixture, thus allowing a very lean mixture to be used.</TD></TR></TABLE>

from: http://www.leecao.com/honda/vtec/sohcvtece.html

 

well not saying your idea sucks or anything but honda made the cames liek that for a reason and i believe even if you get aftermarket street cams they come like that... i know some race cames have the same lift and duration lobes.... so if you made a cam with the same lift and duration lobes i have a feeling you would mess with your performance mainly at idle and low rpms not so much i think at higher r's

 

vtec-e is a lil different i think how it works is at very low r's you only run on one lobe... go higher and it kicks in the second lobe... rev even higher and "vtec" kicks in like on a normal d series... pretty much like a 2 stage vtec... supposed to be ultra economical