Air inlet tubes - do I need them?

DONCZ · Jun 20, 2017

Hello,
I think title describes everything

.
Are those tubes necessary in air box ?
Box is enclosed , not much of false air can get in. Don't see real purpose of those pipes.
Sorry to post , I couldn't find old threads about it.

T_C · Jun 20, 2017

Re: AIR INLET TUBES - DO I NEED THEM ?

Yes, you need.

They tune the intake.
Length and size of exhaust pipe matters, same applies for intake.

Blrfl · Jun 20, 2017

More importantly, what would be the benefit in removing them?

--Mark

spiderman302 · Jun 20, 2017

Yes you need - if you want a quiet bike.
Noise does not make the bike go faster, it just gives the impression that it does.

Catmandu2 · Jun 20, 2017

Removing your inlet tubes will reduce performance. Cat'

DONCZ · Jun 20, 2017

Catmandu2 said:
Removing your inlet tubes will reduce performance. Cat'

and how , if you remove inlet tubes from air box you and up with one air mass not restricted by additional structures.

Did somebody actually try to do this ?

T_C · Jun 20, 2017

DONCZ said:
if you remove inlet tubes from air box you and up with one air mass not restricted by additional structures. Did somebody actually try to do this ?

Obviously there is only one answer... Go For It!

Tuning the intake plenum could be snake oil.. we will wait to hear how yours works. Could be the next big performance we didn't know we needed.

PS You might want to start reading about inlet manifolds, resonance, runners and tuning here. Ever notice you don't get to see the inlet manifold on a drag racer?

Byron · Jun 20, 2017

DONCZ said:
and how , if you remove inlet tubes from air box you and up with one air mass not restricted by additional structures.

Did somebody actually try to do this ?

How about them not being there and instead of smooth air flow you end up with uneven and turbulent air flow instead. Look at the car world, in days gone by you had cross ram with long runners which increased performance, today they are going back to long runners for the same reasons.

Catmandu2 · Jun 20, 2017

I remember reading a magazine evaluation (I believe it was),, that described the ST13's airbox design as "the best there is". From a performance standpoint,, intake tuning is as important as exhaust tuning. An engines power potential depends on getting the maximum amount of fuel/air mixture in, and scavenging as much of the spent exhaust gas's out. Optimum length of the intake track for a given engine speed range increases the air/fuel charge that is drawn into each cylinder. No,, I have not tried removing my tuned inlets. I would be interested to hear what experiences others have had,, as I expect that a power reduction would result from the removal of the inlet stacks. The power loss would increase with rpm,,, imho,,,, Cat'

DONCZ said:
and how , if you remove inlet tubes from air box you and up with one air mass not restricted by additional structures.

Did somebody actually try to do this ?

thekaz · Jun 20, 2017

are we talking about the rubber velocity stacks inside the air box ?
if it is then you really wanna keep them as they are part of what makes the ST1300 smooth with a great torque curve.
Tuning velocity stacks can be quite the voodoo science similar to tuning a multi carb system. It can greatly effect torque curves and engine noise.
Lots of the land speed guys go mental experimenting with different shapes & lengths to get the extra "little"... I put bear short stacks in my ZX12R and it does not "feel" different to me LOL

SMSW · Jun 20, 2017

Catmandu2 said:
I remember reading a magazine evaluation (I believe it was),, that described the ST13's airbox design as "the best there is". From a performance standpoint,, intake tuning is as important as exhaust tuning. An engines power potential depends on getting the maximum amount of fuel/air mixture in, and scavenging as much of the spent exhaust gas's out. Optimum length of the intake track for a given engine speed range increases the air/fuel charge that is drawn into each cylinder. No,, I have not tried removing my tuned inlets. I would be interested to hear what experiences others have had,, as I expect that a power reduction would result from the removal of the inlet stacks. The power loss would increase with rpm,,, imho,,,, Cat'

Wouldn't the OP have to dyno test the bike first, then remove the air inlet tubes, and then dyno the bike again to get a definitive answer? Or will there be enough of a drop (or change) in performance that we could trust his seat of the pants evaluation?

mlheck · Jun 20, 2017

I'm all for trying new things, but this really makes no since. Intake tuning provides torque. Do a little research. If these were not needed I hardly think Honda would have gone through the expense of installing them.

I'm really struggling to understand what the potential upside to this would be.

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ST Gui · Jun 20, 2017

thekaz said:
are we talking about the rubber velocity stacks inside the air box ?

Bingo! These are velocity stacks. They smooth airflow and keep it flowing fast to individual cylinders. Getting maximum airflow into each cylinder is as important as scavenge the airflow out of it.

Catmandu2 · Jun 20, 2017

Yes,,, smsw,,, I would expect the drop would be easily discernible,, even on the old butt dyno,,, Cat'

SMSW said:
Wouldn't the OP have to dyno test the bike first, then remove the air inlet tubes, and then dyno the bike again to get a definitive answer? Or will there be enough of a drop (or change) in performance that we could trust his seat of the pants evaluation?

Wahrsuul · Jun 21, 2017

IIRC, they increase air speed at lower rpms to increase low-mid torque. But hey, it's your bike, pull them and see what happens.

Blrfl · Jun 21, 2017

ST Gui said:
Bingo! These are velocity stacks.

Can't say I've ever seen a velocity stack with a bend in it, and these lack the horn-shaped opening that pulls it into a shape that will maximize air flow. (If you suck air into the blunt end of a tube, the air moves in such a way that the column only occupies a fraction of its diameter. The shape of the stack forces the air to fill it.)

There may be some tuning of the intake length happening, but I think there's more going on. Take the lid off the air box and you'll see this:

I'd wager that if you could put a clear lid on the air box and add some smoke to the intake while the engine is running, you'd see flow along four distinct paths from the air filter to the snorkels. The two front cylinders draw from the top and bottom halves of the air filter at the front and the two in the rear draw from the sides. Next time I pull my filter out, I'll check to see if the dirt is in a pattern that would bear that out. Anyway, with none of the snorkels drawing air in a way that crosses paths with any other, there's no opportunity for vacuum from one cylinder to affect the flow of air to any of the others. Take them out of the box and I'll bet anything cylinders 3 and 4 start seeing choppy air.

(Also interesting to note in the picture is that the seam in the filter screen is right in front of the snorkels for cylinders 1 and 2. I wonder if installing the filter as shown disturbs the air flow to those cylinders.)

--Mark

Don B · Jun 21, 2017

I'm thinking that removing the snorkels would really upset the starter valve synchronization as well result in increased fuel consumption.

Mellow · Jun 21, 2017

Also, any dust/oil/debris that ends up in the airbox should settle to the bottom so the snorkels help with getting clean air to the throttle bodies... whenever you open up the airbox, there's usually some oil in there.

wjbertrand · Jun 24, 2017

Don B said:
I'm thinking that removing the snorkels would really upset the starter valve synchronization as well result in increased fuel consumption.

Shouldn't affect the starter valve sync as that is actually performed with the air cleaner assembly completely removed. It would likely screw up the careful acoustic intake tuning Honda has done though, and make the bike run poorly.

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Igofar · Jun 24, 2017

wjbertrand said:
Shouldn't affect the starter valve sync as that is actually performed with the air cleaner assembly completely removed. It would likely screw up the careful acoustic intake tuning has done though, and make the bike run poorly.

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Air inlet tubes - do I need them?

DONCZ

T_C

Blrfl

Natural Rider Enhancement

spiderman302

Catmandu2

DONCZ

T_C

Byron

Catmandu2

thekaz

haz gone feral

SMSW

mlheck

ST Gui

240Robert

Catmandu2

Wahrsuul

Blrfl

Natural Rider Enhancement

Don B

Mellow

Joe

wjbertrand

Ventura Highway

Igofar