EG-B20vtec

Here's my idea:

I was contemplating the effects produced by two different sets of valves on one head. As in using half of one set of oversized Intake valves and one half of the oversized Exhaust valves. Wouldn't this aid in creating a swirl effect entering and exiting the combustion chamber along with other flow improvements?

For example:

Running one oversized valve on the appropriate mid sized lobe on a VTEC bumpstick. By doing this on intake and exhaust I'm sure there would be a significant benefit.

This would also allow someone to run half of the oversized valve setup in order to run huge cams with no interference between valves. This was the problem T-Bone was running into while trying to advance his Cam Gears when using the BC5.

Talk amongst yourselves!

mgags7

Keep in mind that both the big valve and the small valve open on the vtec lobe...

before vtec, the primary and secondary lobes each open their specific valve, but then when vtec hits, the vtec lobe opens both valves

D-Rob

Your 'swirl' wouldn't have the same effect in VTEC.

I was always under the impression swirl came from the different lift/duration of the primary/secondary lobes.

EG-B20vtec

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bb4ever &raquo;</TD></TR><TR><TD CLASS="quote">Keep in mind that both the big valve and the small valve open on the vtec lobe...

before vtec, the primary and secondary lobes each open their specific valve, but then when vtec hits, the vtec lobe opens both valves</TD></TR></TABLE>

Keep in my that I have to explain VTEC to people who claim to know how it works.
I'm well aware that both valves are engaged simultaneously by the same larger VTEC lobe and that this takes place as a result of locking the three rocker arms together.

d16dcoe45

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EG-B20vtec &raquo;</TD></TR><TR><TD CLASS="quote">

Keep in my that I have to explain VTEC to people who claim to know how it works.
I'm well aware that both valves are engaged simultaneously by the same larger VTEC lobe and that this takes place as a result of locking the three rocker arms together. </TD></TR></TABLE>Its actually not very clear if you got the jist of what he was saying. So most people have the general concept of vtec down, but what he (d-rob) was saying (I think) is that since there are three lobes for every two valves--when the valves are still on the low rpm cam, one of the valves opens just a trifle more than the other one (low lobe, mid lobe) and that is what induces swirl--when the pin locks--they both follow one large lobe. Your idea is interesting though, I wonder if it would help?

Combustion Contraption

Well, you could calculate air speed at a given air density and vacuum in the cylinder, then calculate how long in milliseconds it takes for the piston to decsend from TDC to around 30-40 ABdC, then you would know how much time the air has to 'swirl' at high RPM. I think you can guess from this post what i think of 'swirl'

Combustion Contraption

I think youll find more power optimising the flow path for high rpm speed, and optimising quench area as well.

EG-B20vtec

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by D-Rob &raquo;</TD></TR><TR><TD CLASS="quote">Your 'swirl' wouldn't have the same effect in VTEC.

I was always under the impression swirl came from the different lift/duration of the primary/secondary lobes.</TD></TR></TABLE>

The swirl would have a more pronounced effect while in VTEC. The differing Valve Diameters alone would create a volume split entering and exiting the chamber. This split would have differing velocities and volumes between the large and small sides of the port.

EG-B20vtec

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">I think youll find more power optimising the flow path for high rpm speed, and optimising quench area as well.</TD></TR></TABLE>

How so?

Dually noted...I have a feeling why you might feel the way you do about swirl.
So excuse my poor choice of title. I would probably rather focus my emphasis on the utilization of Larger cams without Valve to Valve contact. I still belive a gain is to be had by varied valve sizes.

MAX_CFM

TUMBLE ...

EG-B20vtec

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

I take it thats bad...

MAX_CFM

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EG-B20vtec &raquo;</TD></TR><TR><TD CLASS="quote">I take it thats bad...</TD></TR></TABLE>

I have had Swirl before ..

I think Its a type of ICE Cream

I wouldnt be looking for swirl on a hi port 4 valve head

thats just my 2 cents ...

EG-B20vtec

thanks for the schooling!

Point well taken...i can see where this is going.

Intake port geometry and the "tumble-port" combustion chamber design provide engine efficiency and performance. The "tumble-port" design relates to the way the fuel-air charge enters the combustion chamber, in a "tumble" fashion instead of a "swirl". The "tumbling" charge of fuel-air mix is more volatile as it enters the chamber... creating more power.

EG-B20vtec

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

Isn't this term rather Ambiguous?

Maybe you could eloborate?

Combustion Contraption

Unless you create buttloads more velocity with your staggered valve setup, youll be taking a step backward.

motoman

If you want to understand the effects of more swirl, you should look into lean burn engines. For example, the primary lobes of the intake cam in the civic vx are different sizes. This is done so that one valve opens more than the other, which creates a swirl effect. I think the primary lobes in the b series are also staggered, but to less of a degree. Generally, more swirl promotes a faster and more complete burn, which is especially important in a lean burn engine, because lean (in this context lean is something like &gt; 18:1 afr) mixtures tend to burn less completely and more erratically. Swirl is also useful with high EGR, as lean burn and high EGR have similar combustion difficulties.

Swirl and tumble are two different phenomena, the former promoting combustion, and the latter promoting scavenging.

Rocket

Why would you want to create a velocity differential between from one side of the port versus the other? You already have to deal what that for the floor and the roof of the port.

Swirl is very common in low speed motors for increased low speed peformance or for lower emissions. The Toyota 22R motor (low speed truck motor) or 8 valve Honda HF motor come to mind, neither of which is designed to perform past 6k rpms.

If you want to make really good power you design your motor (with emphasis on the intake track) to be able to run the maximum mean valve opening for you intake valve(s).