stock 92 civic vx vtec question?

[DOFZO]

Originally Posted by DOFZO

Originally Posted by 83gs1100g

i know its not going to through you back but you should feel something??? this is my point. the only time you you feel a kick is when coming out of lean burn. as you stated before the 2500 rpm switchover it is just to keep 12v mode out. so below 2500 when your in L/B and you hit the throttle its going to 16v mode(vtec on) even at idle.

Look at the table above "Variable Timing Change Conditions": Engine Speed 2500 rpm min

How can the secondary intake valve be engaged at idle if one of the the minimum conditions for the secondary intake valve rocker arm to engage is 2500 rpm?

"Lean burn" is a 12 valve operation. In order to exit "lean burn" the secondary intake valve rocker arm must be engaged by the spool valve "vtec" which it CAN'T do below 2500 rpm. There is NO way to have all 16 valves on a D15Z1 engine operating at idle.


I've provided plenty of evidence to back up my "claim". All you have is your feeling or lack there of. You'll have to take your argument to Honda engineers, good luck with that.






ZO.

[83gs1100g]

Originally Posted by DOFZO

If you accelerate from idle what rpm are you shifting at and how "hard" is your acceleration? This isn't a DOHC B18C5, it's a SOHC D15Z1. There is no power!

its easy to keep from L/B engaging. you dont have to throttle much at all to keep L/B from engaging. this is my point. L/B is 12v mode. any other time you are not in L/B its in 16v mode. this is just how it feels when you drive it. i just dont know how to prove it from a electrical stand point or not sure which mode you are calling vtec-e and non-vtec?[/QUOTE]

[83gs1100g]

Originally Posted by DOFZO

Look at the table above "Variable Timing Change Conditions": Engine Speed 2500 rpm min

How can the secondary intake valve be engaged at idle if one of the the minimum conditions for the secondary intake valve rocker arm to engage is 2500 rpm? .

this is saying 12v mode should disengage then.

[/QUOTE]
"Lean burn" is a 12 valve operation. In order to exit "lean burn" the secondary intake valve rocker arm must be engaged by the spool valve "vtec" which it CAN'T do below 2500 rpm. There is NO way to have all 16 valves on a D15Z1 engine operating at idle. [/QUOTE]

so your saying the vx motor operates in L/B at idle? i don't this this is the case at all.
[/QUOTE]

[/QUOTE]

I've provided plenty of evidence to back up my "claim". All you have is your feeling or lack there of. You'll have to take your argument to Honda engineers, good luck with that. [/QUOTE]

please show me cause im still in belief just by how the motor feels when L/B kicks in and out that L/B is the only time its in 12v mode.

[DOFZO]

Originally Posted by 83gs1100g

its easy to keep from L/B engaging. you dont have to throttle much at all to keep L/B from engaging. this is my point. L/B is 12v mode. any other time you are not in L/B its in 16v mode. this is just how it feels when you drive it. i just dont know how to prove it from a electrical stand point or not sure which mode you are calling vtec-e and non-vtec?

Vtec-e isn't a mode. It's a operation:





Here's another SOURCE for you.

Again, you CAN'T have 16 valves at idle. It's impossible. You CAN rev the engine to 2500 rpm and go WOT to get 16 valves from a dead stop, but as you sit at a red light with your right foot on the floor only 12 valves are working.


EDIT: the bolded part is wrong. You must have a minimum wheel speed of 3 mph and be above 2500 rpm to get all 16 valves.

The more correct statement would then be:

As you're rolling (3 mph) up to a red light in neutral, the light turns green, you then put the transmission in first, go WOT and release the clutch you in theory should be in a 16 valve operation. Enjoy.


ZO.

[DOFZO]

Originally Posted by 83gs1100g

this is saying 12v mode should disengage then.

so your saying the vx motor operates in L/B at idle? i don't this this is the case at all.

Originally Posted by 83gs1100g

please show me cause im still in belief just by how the motor feels when L/B kicks in and out that L/B is the only time its in 12v mode.

Read the first paragraph.

Low rpm, defined as less then 2500 rpm, is a 12 valve operation. Also known as "lean burn".

High rpm, at a minimum of 2500 rpm, is the 16 valve operation. Also known as "not being in lean burn".

Vtec-e is the two part operation and engagement of a primary and secondary rocker arm. When the vtec solenoid becomes engaged, above 2500 rpm, the secondary rocker arm is lock to the primary rocker arm and both intake valves work at the same time. That ONLY happens above a minimum of 2500 rpm.

[DOFZO]

Originally Posted by 83gs1100g

this is saying 12v mode should disengage then.

12 valves are always working. All vtec does is engage 1 additional valve per cylinder. The "normal" mode of the engine is 12 valves, when you need more "power"*, that word is relative, vtec engages all 16 valves.

*Power is the ponies provided above 2500 rpm.





ZO.

[DOFZO]

Originally Posted by 83gs1100g

so at idle its 12v? i disagree. when you accelerate from idle and dont let it get into L/B and you rev past 2500 rpms does the motor gain a sudden increase in power? no it doesn't. then this means vtec it always engaged from idle on and only disengages for L/B.

I think this is where you're going wrong.

You are somehow imagining a "spike" in power because of the engagement of the additional valve. There's no spike. You AREN'T going from 10hp with 12 valves to 92hp with 16 valve. You are just ABLE to get to 92hp (at 5500 rpm) because you have 16 valves. LOOK AT A D15B8. It only has 8 valves, but I bet if you were to "drag race" a CX off the line it would be an even race until you went above 2500 rpm where you would SLOWY pull ahead.

You can google images of "vtec-e dyno" to get an idea of what I mean, but the power curve is "linear" with respect to it being a curve. The transition from 12 valves to 16 valve doesn't create a "mountain" in the curve. It isn't an exponential curve either.




ZO.

[83gs1100g]

ok what happens here? the car is cold and you start it and take off will the motor go into L/B? no it wont. why not?

[83gs1100g]

Originally Posted by DOFZO

You are somehow imagining a "spike" in power because of the engagement of the additional valve. There's no spike. You AREN'T going from 10hp with 12 valves to 92hp with 16 valve. You are just ABLE to get to 92hp (at 5500 rpm) because you have 16 valves. LOOK AT A D15B8. It only has 8 valves, but I bet if you were to "drag race" a CX off the line it would be an even race until you went above 2500 rpm where you would SLOWY pull ahead..

i know its not going to spike in power. what gave you that idea? what i am referring to is you will feel what is like when the a/c kicks on and off. that suttle change in power is the same as L/B engaging and disengaging. the shift light is my gauge for when L/b kicks in and out. when shift light comes on L/B will engage if you stay easy on throttle. my buddy has one and he says he cant tell when his L/b kicks in and out. so i drove it and i can tell. its very similar to a/c kicking on and off..[/QUOTE]

[DOFZO]

Originally Posted by 83gs1100g

ok what happens here? the car is cold and you start it and take off will the motor go into L/B?

The default "mode" is L/B (12 valves). You have four conditions to meet in order to exit L/B "mode" (16 valves).

For 16 valve operations, all four conditions have to be met:

-Minimum engine speed: 2500 rpm. (NOT IDLE)
-Minimum vehicle speed: 3 mph. (NOT STOPPED)
-Minimum water temp: 22.5*F (On a 90*F day, that condition is probably met with a "cold" engine)
-Engine load: Some negative intake manifold pressure


So to answer your question:

We'll assume it's a nice warm morning and before you even start your car the water temp is above 22.5*F. So you hop in, start your engine (12 valves), you then put the transmission in 1st and floor it, you will be using 12 valve until you're going more then 3 mph and over 2500 rpm on the tach. As you shift from 1st to 2nd, if the rpms fall below 2500, you will return to a 12 valve operation until exceeding 2500 rpms in 2nd gear.

If you were at 70 mph in 3th gear (3500 rpm, 16 valve operation) and put the transmission into neutral (idle) vtec would unlock the secondary intake rocker arm and you would be in a 12 valve operation or "lean burn".

Look at the four conditions. If ONE isn't met, you don't get the additional valve. You get 12 valves for free and have to "work" for the other 4 valves.


Good?





ZO.