Topic: Split - What is wrong with the stock Honda induction system?

[Laminar]

Very well sir.....

Please feel free to post your principles.

You didn't take the time to read Bernoulli so please post the research you have done.

For the record....I said Restricts.

Given the head pressure in the bowl, the size of the jet, and the pressure in the venturi......What do you think Restricts flow?

Bowl pressure should be atmospheric or there abouts.

Venturi pressure will be dependant on RPM but at  WOT the venturi shape and size is fixed.

Now....put a bigger orifice in the mix......and what have you got?

Enrichment.

You didn't change the venturi size or the atmosperic pressure acting on the fuel in the bowl......

Wheres the restriction?

You're jumping all over the place here.

Your initial statement:

You will no doubt know that the main Jet acts as a restriction only at Wide Open Throttle.

Then this:

A certain diameter straw will in fact flow only so much liquid. eventually you reach a point at which no more fluid can flow regardless of the suction.

However the diameter of the straw (or jet) is in relation to the suction.

So at wide open throttle....the diameter of the jet (or straw) AND the suction determine the flow.

True, but not exclusive. At 50% throttle, the diameter of the main jet AND the suction play a major part in determining fuel flow. Same for 75%.

Rereading through all of this, I wonder if the initial statement you meant to make was:

You will no doubt know that the main Jet acts as the only restriction at Wide Open Throttle.

That would make sense, and render the previous several pages a semantic mistake.

Semantics aside, I did do some calculations for fun.

- Assuming a BSFC of 0.45, each main jet sees 59.15 cc/min of fuel flow at the horsepower peak.
- A #100 main jet has a diameter of 1.00mm (according to an old TT post)
- With a cross-sectional area of pi()*(0.05cm)^2 I estimate the free-stream fluid velocity to be 125.52 cm/s, or 1.25m/s
- I found all sorts of values for the kinematic viscosity of gasoline, from 0.46 to 0.88, all at 15.6 degrees C.
- With a v of 0.88 and density at 15.5 C of 700kg/m^3, the dynamic viscosity is u=6.16x10^-4
- The hydraulic diameter of the pipe is 0.001 m

This makes the Reynolds number 1420, which is well within the laminar flow range for the restricting section of the main jet, neglecting entrance and exit conditions, etc.

But at this point I'm assuming this whole thing was a semantic mistake.

[MickeyX]

I'm learning a lot on here. Much of it I didn't care about one way or the other but, well, there it is. Shoved in a little corner of my brain for at least, oh, a day and a 1/2.

Now excuse me while I take your soapbox. I've got plans for that thing. Thanks. 

Maybe you can just stand up on your toes or something?

[BobbyR]

Mlinder,

I like the velocipod.  It eliminates the pumping work losses that the stock system is plagued with.  TT's comments at the beginning of this saga are very well researched, and show the quality work that went into the stock system, but it remains that the path from intake to engine is very tortuous with the stock design.  Every bend and ridge in the intake creates pumping losses in the intake system that the engine has to provide the power to overcome.  Pumping loss has a real impact on engine power and volummetric efficiency, and that is what pod filters are able to reduce, and what a design like the velocipod is able to reduce.

I like the stock system, but it can definitely be improved upon... easily.

Camelman
Heat Transfer and Fluid Dynamics Engineer (yep, I'm legit)

I like the Velocipede also

[Frankenkit]

I remember when I was a little kid on the playground.  All the athletic kids, at one time or another, would seem to end up in a fistfight to see who was the toughest.  All us nerdy smart kids kind of felt left out.  Thank God for the internet....

Watch out, nerd boy, or you're gonna get yer glasses broke in a full-on case of...

NERD



In all seriousness I'm subscribing to this thread because I find it interesting. I wish we could apply the rules of formal debate teams etc, but such is life on a forum.

Please continue, gentlemen.

[kghost]

Very well sir.....

Please feel free to post your principles.

You didn't take the time to read Bernoulli so please post the research you have done.

For the record....I said Restricts.

Given the head pressure in the bowl, the size of the jet, and the pressure in the venturi......What do you think Restricts flow?

Bowl pressure should be atmospheric or there abouts.

Venturi pressure will be dependant on RPM but at  WOT the venturi shape and size is fixed.

Now....put a bigger orifice in the mix......and what have you got?

Enrichment.

You didn't change the venturi size or the atmosperic pressure acting on the fuel in the bowl......

Wheres the restriction?

You're jumping all over the place here.

Your initial statement:

You will no doubt know that the main Jet acts as a restriction only at Wide Open Throttle.

Then this:

A certain diameter straw will in fact flow only so much liquid. eventually you reach a point at which no more fluid can flow regardless of the suction.

However the diameter of the straw (or jet) is in relation to the suction.

So at wide open throttle....the diameter of the jet (or straw) AND the suction determine the flow.

True, but not exclusive. At 50% throttle, the diameter of the main jet AND the suction play a major part in determining fuel flow. Same for 75%.

Rereading through all of this, I wonder if the initial statement you meant to make was:

You will no doubt know that the main Jet acts as the only restriction at Wide Open Throttle.

That would make sense, and render the previous several pages a semantic mistake.

Semantics aside, I did do some calculations for fun.

- Assuming a BSFC of 0.45, each main jet sees 59.15 cc/min of fuel flow at the horsepower peak.
- A #100 main jet has a diameter of 1.00mm (according to an old TT post)
- With a cross-sectional area of pi()*(0.05cm)^2 I estimate the free-stream fluid velocity to be 125.52 cm/s, or 1.25m/s
- I found all sorts of values for the kinematic viscosity of gasoline, from 0.46 to 0.88, all at 15.6 degrees C.
- With a v of 0.88 and density at 15.5 C of 700kg/m^3, the dynamic viscosity is u=6.16x10^-4
- The hydraulic diameter of the pipe is 0.001 m

This makes the Reynolds number 1420, which is well within the laminar flow range for the restricting section of the main jet, neglecting entrance and exit conditions, etc.

But at this point I'm assuming this whole thing was a semantic mistake.

All that and you call me a Jew?

Oh wait thats semitic......

Damn difficult to get a consensus on the viscosity of gasoline.

Not factoring pipe friction....and your guess would be as good as mine....I'd agree with you that 1420 would be well below the 2320 reynolds for laminar flow.

[MickeyX]

All I know is that my bike is better and faster than yours.

[kghost]

All I know is that my bike is better and faster than yours.

Which one of mine?  I have lots. 

[MickeyX]

this one   

[ekpent]

Is that the airbox hanging off the back behind the seat   

[MickeyX]

airbox / makeup kit. 

[kghost]

this one   

Holy crap....I have one of those in the shop. Cept its gold.

My Mother bought it for $30 and it needs a new battery.

Too Funny.

[MickeyX]

she got robbed. 

[MRieck]

 Spitting back is more a cam timing issue, too much overlap with narrow lobe centers and lowish rpm,

PJ

I don't think it's a cam timing thing (to much overlap) with SOHC as much as it is the fixed lobe separation. I guess it could be called cam timing but I think of cam timing as it applies to individual lobe centers. More lift and duration will increase overlap but you really can't control that with a single cam system. That's one of the great things about 2 cam systems. You can control the opening and closing of the intake and exhaust individually. Automobile cams (American V8 single cam) make cams with different degrees of separation....I'm sure you could get Megacycle or Web to do it.

[754]

 I believe that thing behind the seat is the airheadbox....


 Yeah, I know, I am gonna fry for that one, but the Devil made me do it...







....and it was worth it......

[fang]

TT -- THANK YOU FOR THE GREAT INFORMATION AND STUBBORN SUPPORT OF IT!

Here is a pic of a modified airbox I made for one of my modified CB750s.  you can click the image for a larger view:

It is a K&N filter, and I think the airbox is stock, except the sides of the bottom half are removed.  I have a custom plate sealing the bottom of the filter and affixing it to the top half.  IMHO this a good compromising performance mod -- I get the benefits of factory velocity stacks, et all.  Plus I get the potentially increased air flow from which a  900cc modified motor and hot cam might benefit.

peace and grease,
-fang

[edbikerii]

OK TT, your very direct "No." answer has brought me to the light.  My most basic assumption was wrong, and I apologize for my stubbornness.

These answers and your link to http://www.freshgasflow.com/physics/flow/flow.html have opened my eyes to the direct relationship between pressure and flow through a fixed-size orifice.

This is causing me to re-evaluate my conclusion that I had to increase my main jet sizes 17% because I had 17% more air flow.  The more I thought about that conclusion, the more I realized it was wrong as well.  The 17% increase in the diameter of the hole in the jets actually results in a MUCH GREATER cross-sectional area, and there is just no way that I experienced that much of a power increase, not even just in my head!!!  While I still feel that the SOTP dyno shows a performance gain, there is no way that there could be anywhere near a 17% performance gain, and certainly not the MUCH LARGER percentage increase due to the larger increase in cross-sectional area of the jets.

Thank you for the explanation and the knowledge, TwoTired,

Edward

Thank you for confirming what I said, what, 10 posts ago?  No matter how much vacuum you apply, once you have reached the maximum flow for a given orifice, NO MORE FUEL WILL FLOW.  Does everybody agree on that?

No.  And you simply CANNOT prove it!  Even if a committee votes in your favor.  Committees don't create physical principles.

The smaller the orifice (the straw) is, the less liquid will flow.  Everybody agree on that?

Only when the pressure differential across the orifice is the same.

The smaller the orifice is, the lower the vacuum (meaning less pressure differential) required to reach the maximum flow through the orifice.  Everyone agree on that?

No.  Unless you have also added turbulence to the flow, which is very very unlikely in the SOHC4 carb.

At WOT, the main jet has reached its maximum flow.  Everyone agree on that?

Main jet still flows at a rate determined by the pressure differential.  If you change the pressure differential at WOT then the amount of fuel flowing though it changes as well. As in switching from the stock filter membrane to a filter membrane with less pressure drop across it.

[TwoTired]

OK TT, your very direct "No." answer has brought me to the light.  My most basic assumption was wrong, and I apologize for my stubbornness.

Thank you for the explanation and the knowledge, TwoTired,

Edward

That's fine, Edward.  And, thanks for that post.  I really am here to try and help out.  Glad to be of some assistance.
Cheers,

[mick750F]

OK TT, your very direct "No." answer has brought me to the light.  My most basic assumption was wrong, and I apologize for my stubbornness.

These answers and your link to http://www.freshgasflow.com/physics/flow/flow.html have opened my eyes to the direct relationship between pressure and flow through a fixed-size orifice.

This is causing me to re-evaluate my conclusion that I had to increase my main jet sizes 17% because I had 17% more air flow.  The more I thought about that conclusion, the more I realized it was wrong as well.  The 17% increase in the diameter of the hole in the jets actually results in a MUCH GREATER cross-sectional area, and there is just no way that I experienced that much of a power increase, not even just in my head!!!  While I still feel that the SOTP dyno shows a performance gain, there is no way that there could be anywhere near a 17% performance gain, and certainly not the MUCH LARGER percentage increase due to the larger increase in cross-sectional area of the jets.

Thank you for the explanation and the knowledge, TwoTired,

Edward

Thank you for confirming what I said, what, 10 posts ago?  No matter how much vacuum you apply, once you have reached the maximum flow for a given orifice, NO MORE FUEL WILL FLOW.  Does everybody agree on that?

No.  And you simply CANNOT prove it!  Even if a committee votes in your favor.  Committees don't create physical principles.

The smaller the orifice (the straw) is, the less liquid will flow.  Everybody agree on that?

Only when the pressure differential across the orifice is the same.

The smaller the orifice is, the lower the vacuum (meaning less pressure differential) required to reach the maximum flow through the orifice.  Everyone agree on that?

No.  Unless you have also added turbulence to the flow, which is very very unlikely in the SOHC4 carb.

At WOT, the main jet has reached its maximum flow.  Everyone agree on that?

Main jet still flows at a rate determined by the pressure differential.  If you change the pressure differential at WOT then the amount of fuel flowing though it changes as well. As in switching from the stock filter membrane to a filter membrane with less pressure drop across it.

   It's very refreshing to to see one of our more cantankerous members step up and serve themselves a piece of humble pie. Please don't look at this as a slight Ed, it's not intended to be. People who are cantankerous are themselves refreshing...in my eye anyway.

   And thank you Lloyd for yet another informative post and your cantankerous effort to stick around and defend basic physics. 

Mike

[kghost]

I think this has been one of the most enlightening and positive discussions we've had in a while.

I know I've learned some things and gotten refreshed on some long forgotten science.

It reminds me why I joined this forum to begin with.

Props to Edward for his post.

[Retro Rocket]

OK TT, your very direct "No." answer has brought me to the light.  My most basic assumption was wrong, and I apologize for my stubbornness.

These answers and your link to http://www.freshgasflow.com/physics/flow/flow.html have opened my eyes to the direct relationship between pressure and flow through a fixed-size orifice.

This is causing me to re-evaluate my conclusion that I had to increase my main jet sizes 17% because I had 17% more air flow.  The more I thought about that conclusion, the more I realized it was wrong as well.  The 17% increase in the diameter of the hole in the jets actually results in a MUCH GREATER cross-sectional area, and there is just no way that I experienced that much of a power increase, not even just in my head!!!  While I still feel that the SOTP dyno shows a performance gain, there is no way that there could be anywhere near a 17% performance gain, and certainly not the MUCH LARGER percentage increase due to the larger increase in cross-sectional area of the jets.

Thank you for the explanation and the knowledge, TwoTired,

Edward

Thank you for confirming what I said, what, 10 posts ago?  No matter how much vacuum you apply, once you have reached the maximum flow for a given orifice, NO MORE FUEL WILL FLOW.  Does everybody agree on that?

No.  And you simply CANNOT prove it!  Even if a committee votes in your favor.  Committees don't create physical principles.

The smaller the orifice (the straw) is, the less liquid will flow.  Everybody agree on that?

Only when the pressure differential across the orifice is the same.

The smaller the orifice is, the lower the vacuum (meaning less pressure differential) required to reach the maximum flow through the orifice.  Everyone agree on that?

No.  Unless you have also added turbulence to the flow, which is very very unlikely in the SOHC4 carb.

At WOT, the main jet has reached its maximum flow.  Everyone agree on that?

Main jet still flows at a rate determined by the pressure differential.  If you change the pressure differential at WOT then the amount of fuel flowing though it changes as well. As in switching from the stock filter membrane to a filter membrane with less pressure drop across it.

   It's very refreshing to to see one of our more cantankerous members step up and serve themselves a piece of humble pie. Please don't look at this as a slight Ed, it's not intended to be. People who are cantankerous are themselves refreshing...in my eye anyway.

   And thank you Lloyd for yet another informative post and your cantankerous effort to stick around and defend basic physics. 

Mike

+1

[edbikerii]

Yes, quite.  I think this was definitely in the top five or so for me.  How do we get this stickied or put in the FAQs or something?

I think this has been one of the most enlightening and positive discussions we've had in a while.

[mlinder]

nedes moar turbo! thats what's wrong with the stock induction system!

Kidding. I'll message a real moderator/admin and see if we can get this stickied, or some-such.

[edbikerii]

Thanks for the props, but I'm undeserving.  It was no great accomplishment to make a fool of myself and then be educated.

The credit goes to TT and you guys that were patient enough to keep trying to teach the (cantankerous) dunce.

I think this has been one of the most enlightening and positive discussions we've had in a while.

I know I've learned some things and gotten refreshed on some long forgotten science.

It reminds me why I joined this forum to begin with.

Props to Edward for his post.

[BobbyR]

OK the dust is settling. I am at a point I wish to do more riding and stop fiddling with the bike. What is a good source for filters for the stock airbox. I have used my last one in the stash. I change them every year. Foam, K&N etc. I am open to suggestions.

[manjisann]

OK the dust is settling. I am at a point I wish to do more riding and stop fiddling with the bike. What is a good source for filters for the stock airbox. I have used my last one in the stash. I change them every year. Foam, K&N etc. I am open to suggestions.

Use pods, more airflow and the cool factor add at least 100hp 

Before I get totally flamed, I'm just kidding!!

I realize they aren't paper element, but I like the K&N filters since they can be cleaned and reused. I'm not convinced that anything small enough to bypass one of those would really be that detrimental to the engine.

Brandon