Thoughts on using long air runners in place of pod filters

[Vamisk]

Would using a longer intake runner after the filter clear up the airflow enough to allow proper carburation that pod filters can't do? I found radiator hoses at autozone that fits the BS34 air horn perfectly.
The hose number is D72241 at autozone, i think it's for a 2018 Ram with a Cummins.

I'm worried about residual gas eating through the rubber but i'm going to try it.

When i bought my GS1100 it didn't have a stock airbox, just pods and big surprise it didn't run. I richened the carbs up but it started lean knocking shortly after starting it.
I'm hoping increasing the runner length using longer hose would allow a calmer stream of air to enter the carburetor and correct all the problems pod filters cause.

Does anyone have an opinion on this or some tips for what i could be doing?

 

[Nessism]

A Dynojet kit and quality pods like real K&N's or APE filters will solve the running issues. No need to reinvent the wheel.

 

[wyly]

I had this discussion with my mechanic who is a crew chief in Super Bike Racing he recommended I leave the stock air box in. He said the factory engineers are smart they know what they're doing.

Regardless how well the carbs were adjusted I would lose as much as 10% of torque somewhere in RPM range.

If I encountered a strong cross wind I may need to shield the pods with my leg or hand.

Rain, moisture can be an issue.

The engine will wear 25% faster.

But the bike would look cooler if that was what I wanted.

Despite wanting a cool looking bike I'm a performance guy first, I like silky smooth engine and torque everywhere. I put my air box back in.

 

[Tom R]

My guess is it would be a jetting nightmare. I tried something similar on my cl175 for different reasons.... I added a 7 or 8 inch piece of hard plastic tubing on the end of the carbs because the frame interfered with fitting a filter otherwise. It looked neat when it was done.... but wouldn?t rev past 4K before it broke up. I pulled that off and have just been running without filters.... but it?s a track only bike.

 

[eil]

Your mechanic is right, stock is the way to go unless you have prior experience tuning how an engine breathes. (Or unless you don't mind taking months of time to learn by trial and error.) That's just my opinion anywho.

 

[Guest]

Stock air boxes are out there, get one and go ride.

 

[Buffalo Bill]

I had this discussion with my mechanic who is a crew chief in Super Bike Racing he recommended I leave the stock air box in. He said the factory engineers are smart they know what they're doing.

Regardless how well the carbs were adjusted I would lose as much as 10% of torque somewhere in RPM range.

If I encountered a strong cross wind I may need to shield the pods with my leg or hand.

Rain, moisture can be an issue.

The engine will wear 25% faster.

But the bike would look cooler if that was what I wanted.

Despite wanting a cool looking bike I'm a performance guy first, I like silky smooth engine and torque everywhere. I put my air box back in.

So true, on track it's WOT or braking.
The airbox is designed to provide high vacuum and high velocity air flow. Airbox, carbs, cams and exhaust are designed as a unit, tested as a unit, tested for thousands of miles by the ultimate engineering staff.
Take that team on if you got the money to pay for better results.

 

[Big T]

It wouldn't work, because it doesn't increase the velocity of the incoming air.
That's why race bikes sometimes use velocity stacks, aka bellmouths.
Bernoulli's principle is what's needed. Whether CV stands for constant velocity or constant vacuum, the velocity creates the vacuum

 

[Vamisk]

My primary concern was reducing turbulence right at the air horn. The previous owner also installed an aftermarket header.

 

[hannibal]

Long, skinny runners are good for torque and low rpm power. Short, wide runners (aka velocity stacks) are good for high rpm power. The long runners may help with low end power, but that goes against everything the engine was designed for. I'd stick with short runners.

 

[Steve]

Where would you route these longer runners?

Pods themselves don’t “cause problems”, they only remove the restriction of the airbox. Open carbs will be sucking turbulent air (which is cured by velocity stacks). Longer tubes might help, but how much longer, where would they end, and how do you plan to eliminate the turbulence on them.

.

 

[Vamisk]

I was under the impression that pods contributed to turbulence at the air horn due to not having a plenum of air and drawing air in from all directions.
Regardless i ordered an airbox with boots, Hopefully i can get this thing going good this weekend.

 

[rphillips]

Maybe I'm wrong, but the pods have much less intake air restriction, restriction that creates vacuum, to pull the gas thru the jets. With less vacuum, you will need larger jets to get enough fuel. Turbulence may be a small factor, but vacuum, My opinion, will be way more important than the turbulence.

 

[Nessism]

Many moons ago when I was a poor college student in need of air filters for my XS400 I bought some uni pods because they were cheap. Installed them and rejetted but the bike just didn't run right. After much consternation I reinstalled the plastic/rubber intake runners and clamped the pods onto the ends of that. Problem solved. The runner tube pushed back the pods about 5" or so and made all the difference.

 

[Grimly]

Maybe I'm wrong, but the pods have much less intake air restriction, restriction that creates vacuum, to pull the gas thru the jets. With less vacuum, you will need larger jets to get enough fuel. Turbulence may be a small factor, but vacuum, My opinion, will be way more important than the turbulence.

Bernoulli's Principle. http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html

The pods only play an indirect part in it.

 

[Steve]

Maybe I'm wrong, but the pods have much less intake air restriction, restriction that creates vacuum, to pull the gas thru the jets. With less vacuum, you will need larger jets to get enough fuel. Turbulence may be a small factor, but vacuum, My opinion, will be way more important than the turbulence.

Close, but not quite. :-k

Yes, there is less restriction.
No, it is not the restriction that causes the vacuum.

The vacuum that pulls the gas through the jets is due to Bernoulli's principle. That is, moving air lowers the pressure. Faster-moving air (through a venturi) lowers the pressure even more.

What pods contribute to the mix is, indeed, less restriction, but that lower resctriction merely allows more airflow. More air requires more fuel, hence the need for larger jets.

Pods do help to reduce/remove the turbulence over the sharp edge of the carb intake. Some of the better pods will have a small bellmouth that leads to the carb intake. On the down side, some of the cheaper pods might actually block some critical ports on the carb intake, which leads to other problems.

Yes, you need vacuum for the carbs to work, but it's airflow, not the airbox that creates it.

.

 

[RichDesmond]

Done right, with some intelligent thought and careful jetting, the runners aren't a bad idea. One of the things that made the Toomey kit work so well in the RZ350 was a Y-runner, one chamber with a oiled foam filter mounted to the open end and two runners off of that to the carbs. I believe it was actually a part from a Honda 3-wheeler. The extra volume and more constant airflow through the filter really smoothed out the powerband.
In your case, you could think of each runner as a small airbox for a single cylinder engine.

Done as a shortcut hack, all bets are off.

 

[bobgroger]

I have 2 GS bikes with Pods and a Dynojet kit, and 2 with stock airbox. All run really well. The airbox bikes are a bit smoother throughout the range, the pod bikes have a bit better top end and a gnarly sound. Your choice, but don't try pods without the proper jet needles.

 

[850 Combat]

On my firsr RD, when it got pipes and heads from DG, the airbox left. I put pod filters on it using the orifinal rubber tubes which had been installed between the reed blocks and the air box. It moved the pods back out of sight. I was hoping for some ram effect. It worked fine, and seemed to clear up the transition on to the pipe powerband. I don't remember if they were K&Ns or Unis. It was in the 70s. I would have preferred L&N, but not sure they were around. Current RD400 is using RD350 "Y" style intake runners with a single vertical K&N, which was considered the best practice a few years ago when I built it.

The RD 400 airbox was mostly there to quiet down the intake noise.

 

[Vamisk]

My airbox is coming in today. It won't make a difference at this time because as i found out over the weekend there's so much resistance in the butchered wiring that i don't even get enough voltage to the starter to spin it. Attempted jumping it with even a new battery and wiped out the starter relay so once i clean up the wiring i'll let you guys know how it went.