Power Flat Spots

[Ryland3210]

So Ryland, in the age old debate of "pods" vs "drilled air box" am I to understand that (assuming the intake runners remain in both set ups) the pods may be superior? IOW, is the "reflection" off the inside walls of the air box a negative that is eliminated with pods?

 

I sorry to say I don't know anything about the dimensions or geometry on which to base a comment.

 

 

Does the cross ram result in noticeable throttle lag?

"For '60, the 413 gained a radical ram induction system in which each four-barrel carb fed the opposite cylinder bank via 30-inch "outrigger" tubes. The length of the runners was calculated to produce a super-charging effect in the heart of the rpm range."

 

Given the speed of sound in the 1100 feet per second region, the less than three milliseconds involved would hardly be noticed. However, the surface area available for fuel to condense on when the throttle was suddenly opened would be significantly larger than a conventional intake manifold. The usual solution for that, in the days before unburned hydrocarbons was a concern, was simply a larger accelerator pump-whatever it took.

[Phil A]

However, with each cycle, the pressure wave amplitude is dampened, especially if the inlet end of the tract terminates into a relatively large cavity, especially if containing a filter which can dampen instead of reflecting a pressure wave.

 

The harmonics nature is to invert at the open end of a tube. It is only the energy that is lost that is disipated in the filter/air box. Hence my air box design, which I have published here in the past. The art is to maximise the destruction of the lost energy so not as to add to the effect again appon reflection, minimise the noise, and maximise the air flow at the same time.

The damping effect of the filter is minimal.

 

After optimising the design of the airbox I have the same power as with pods. I would rather have the air filtering ability and quieter intake than the maintenance and noise of pods.

[Ryland3210]

The harmonics nature is to invert at the open end of a tube. It is only the energy that is lost that is disipated in the filter/air box. Hence my air box design, which I have published here in the past. The art is to maximise the destruction of the lost energy so not as to add to the effect again appon reflection, minimise the noise, and maximise the air flow at the same time.

The damping effect of the filter is minimal.

 

After optimising the design of the airbox I have the same power as with pods. I would rather have the air filtering ability and quieter intake than the maintenance and noise of pods.

 

I'm fascinated but having a difficult time learning from your experience and theories, Phil.

 

Please clarify the following:

"invert": what is being inverted, pressure or rarifaction, both or velocity or other?

"destruction of the lost energy": a double negative-please explain.

"add to the effect": which effect?

If the filter is the typical convoluted paper element type, it would seem to be a good acoustic absorber. Why is its dampening effect minimal?

 

What is your opinion on bell mouth inlets?

[dlaing]

After optimising the design of the airbox I have the same power as with pods. I would rather have the air filtering ability and quieter intake than the maintenance and noise of pods.

FWIW dyno testing has shown that the airbox with lid removed makes more power than pods on V11s.

Also, I recall credible claims that the pods made more power when using the runner of the stock airbox rather than being directly connected to the throttle body.

 

***warning speculation follows, please ignore***

I would not be surprised if a better runner design could make the pods work better. I suspect the stock runner is not the ideal length for the pods, and also how the runner pushes the pods towards the frame puts a limit on what size pods can be used with the stock runner.

The V11Sport has only been out for a few years, eventually someone will test some runner tuning lengths beyond the two most obvious configurations.

I'd love to completely re-design the air box.

Phil has impressively maximized its potential by flaring open the intakes and cutting critically placed holes.

I wonder how much more power can be gotten out of a better designed airbox.

Larger filter area,

longer straighter runner,

filter placement so that gravity does not dump and trap crap in filter pleats,

Larger snorkles with tuned length and positive ram air positioning.

***speculation over, please return to your regular reading***

[Phil A]

Ryland 3210,

yes now I read this again, it was a poor explanation wasnt it.

I guess my main aim is to get people thinking, as often it is simply a matter of applying the laws of physics to solve problems.

I never give the complete answer as I believe those who can "make it work" will do the homework a reap the rewards.

Its a bit like the old saying... If have to explain, you wouldnt understand. If my statements provoke questions I am only too pleased to discuss them to inspire further thoughts or improvements.

There is so much we dont know and I find constructive discussion will always yield results.

 

DLaing, dismisses my simple modifications to the airbox, however if he took the time to reproduce it, some glaringly obvious improvements will follow to give even better flow.

Most people dismiss Dr Johns center expansion box however I have found that on a road bike where ridability is important, it works very well in conjunction with getting the rest of the system sorted.

 

I find that an internal combustion engine sometmes works "in spite of how it is made" not because of how it is made. For example, A V10 or V11 is so poorly set up that it will stall. It will not run!

How poorly does an engine need to be set up that it wont even maintain combustion??? To me this is totaly incomprehensible.

Havent we been building engines for nearly 150 years? And we cant even get em to idle!!!

Come on.... its not that hard.

The most efficient engines are still from during the war years. Lets quit the political horseshit and build engines that are worth using.

The fastest quickest , engines in the world today are still based on 1950s designs. What sort of crap is our political system forcing down our throats?

 

End of rant back to your questions.

 

"Inversion"..... look up organ pipe theory.

 

"Destruction of lost energy" This is reference to the energy which is lost at the "bell mouth" Once it is lost to the "air box" as such, it becomes problematic or extremely complicated to deal with.

In the case of our road bike it is easier to write it off or get rid of it to avoid its undesireable or more difficult to deal with, effects.

 

"The effect".... this was a bit broad wasnt it!

This reference begins at the back of the inlet valve, which is the source of this harmonic energy we are discussing here. As the valve slams shut it initialises an harmonic. This is the primary harmonic effect we try and utilise and find problematic at times. On this part of the effect we can verey loosely apply normal organ pipe theory. This is the energy that "inverts"

 

"Some" of this energy is lost, see above, and this creats another effect. In this case an unwantd effect.

 

Some manufacturers use what they call a still air box to influence this effect. This is a long story however if you need further reading, look up Helmholtz resonator.

 

Another effect that I have never seen mentioned is the secondary harmonic that is set up between the throttle butterfly and the bell mouth.

With this effect you can prove that adding to the ram tube length is not the same as adding to the inlet manifold length, however the ram tube is the way that most people seem to go.

 

Remember I mentioned inlet momentum? Think of this in relation to the above statement.

 

As the butterfly is opened and shut, the weight of air behind the butterfly takes on one characteristic and the air in front of the butterfly takes on another.

This is why slides in some carbies achieve better results than the butterflies in our system.

 

Pods and air cleaners can all be made work better by throwing the f*ckin things away, however for those of us who want maximum longevity from our engines, the well set up airbox is as good as anything.

 

A good way to understand inlets is to fit one that is too big and then change everything else untill you get it to work. Then you will begin to understand how it works.

 

I am up to 2x 46mm carbs on the race bike previously mentioned and you could send a 10 year old to the shops on it.

 

Thankyou for taking the time to put some thought into my post.

 

Hope this helps.

 

Phil.

[Ryland3210]

Hi Phil,

 

I enjoyed reading your response. Perhaps sometime this winter, I'll have more time to do the research you suggest to get specific answers on all the questions.

 

Cheers,

John

[dlaing]

DLaing, dismisses my simple modifications to the airbox, however if he took the time to reproduce it, some glaringly obvious improvements will follow to give even better flow.

Most people dismiss Dr Johns center expansion box however I have found that on a road bike where ridability is important, it works very well in conjunction with getting the rest of the system sorted.

I think your modifications are the best thing currently out there.

How did I dismiss it? By suggesting a better airbox could be built?

Are you dismissing my idea that a better airbox could be built?

What is Dr. John's center expansion box?

Is that the air box we have on our bikes?

He did not design our noise and power removing snorkles, right?

[Phil A]

Dlaing, my appologies for mis interpreting your post.

 

Are you dismissing my idea that a better airbox could be built?

 

Absolutely not. I think there is always room for improvement.

 

Dr Johns contribution I spoke about was the centre muffler behind the gearbox on the V10. This is often ridiculed and I feel, misunderstood.

He also spent some time getting extra power from the "original " airbox ie, pre production.

 

One can imagine that the snorkels are the doings of political horsesh*t.

[Ryland3210]

Hi Phil,

 

Can you provide a link to the thread where you describe your mod's?

Thanks,

John

[Pierre]

Hi Phil,

 

Can you provide a link to the thread where you describe your mod's?

Thanks,

John

http://www.v11lemans.com/forums/index.php?...=8924&st=15

[Pierre]

Dr Johns contribution I spoke about was the centre muffler behind the gearbox on the V10. This is often ridiculed and I feel, misunderstood.

Phil, it looks from the picture (Europe) of your lovely red Centauro that you have retained the stock center muffler and the stock Lafranconi pipes. Am I correct in that? Are either / both modified?

 

He [Dr. John] also spent some time getting extra power from the "original " air box ie, pre production.

 

One can imagine that the snorkels are the doings of political horsesh*t.

Phil, I take it the "snorkels" are the runners going into the air box pre filter, and it is those that get "bell mouthed." I assume the runners are the plastic extensions within the air box affixed to the Throttle body - and in your modified air box they remain and are unmodified. Is that correct?

 

Finally, after reviewing previous (paper filter) thread it is my understanding that the work you have done with the air box gets you to the same place (HP) as pods affixed to the stock runners with air box removed, and that retention of the air box was a "noise" and "filtration" driven approach. IOW, pods on the stock runners and your modified air box perform pretty much alike wrt HP? Am I correct in concluding that?

 

TIA.

[Phil A]

 

 

 

Maybe this will explain things a little clearer.

These mods will make your engine run lean so I dont recommend them them to anyone who does not have the provision to add more fuel to compensate. ie My16m or similar.

 

Pierre, exhaust rear mufflers are 2'' straight through. Centre muffler is stock.

 

For the mods described no modifications were done to the bell mouths or the ram tubes attached to the throttle bodies.

 

YEP, pods on stock runners with airbox removed and these airbox mods give similar hp figures.

 

YEP, this was a "noise and filtration driven approach "

 

Regards,

 

Phil A.

[Ryland3210]

....

 

These mods will make your engine run lean so I dont recommend them them to anyone who does not have the provision to add more fuel to compensate. ie My16m or similar.

....

 

Regards,

 

Phil A.

 

Phil,

A picture is worth a thousand words. Thanks. I would like to bounce some ideas off you.

 

1. I would expect the three holes to ingest warmer air than the snorkels. Suppose the snorkels were simply cut off the airbox. What would you expect the result to be?

 

2. I gather from your studies, that unless the ECU is remapped to add fuel at high throttle openings, there would be little change in HP. Moreover, if one were lucky enough to be able to spend any length of time at full throttle, the protracted lean condition could cause piston damage.

 

3. At cruise throttle openings, there would be no reason to change the mapping, because the relatively low air flow rates would not be affected by the reduced restriction provided by the modifications to the airboxl, agreed?

 

Cheers,

John

[Pierre]

...

Maybe this will explain things a little clearer.

...

Yes. Very much so. Thanks again.

[Greg Field]

I did my interpretation of Phil's mods to my airbox on my V11. The holes in mine are round, rather than teardrop shaped. It made more peak power by a very slight margin with the paper filter than with a BMC and cut-off airbox top. The BMC/cut box made better mid-range and torque, though. One of these days, I'll figure out how to post the charts.