Air cleaner stuff

[Keith Winter]

Here's a trick for anyone that wonder's how restrictive their air cleaners are. I've tested mine with my shop vac. I have the biggest one Sear's makes, and it flows allot more cfm that your air filter will ever see. Find the attachment or hose size that fits over the mouth of your filter, stick the filter on the hose, and with the vacuum running, listen for the sound to change. If the sound of the vac doesn't change or changes very little, you know the air flow is more than good enough for your bike. My buddy and I compared his K&N's with my cheap filters and found, surprise, surprise, no difference. This is also a good way to test the filter oil you may be useing. I oil mine with a mix of 50/50 deisel fuel and 2 stroke oil. It's cheap, and stops any dust, after a drip dry doesn't suck off, and won't slow down the air flow.

[spots25]

the flow difference in air cleaners is pretty minimal, and an unscientific test such as that doesn't prove anything. I read a flow test of air filters (for cars) a couple years ago, and their expensive flow meter wouldn't even read because the air filters were flowing so much. They had to duct tape off half of the filters in order to get a reading. A little tiny bit of air will make a difference though

[Keith Winter]

Who said anything about scientific? And I'll tell you what, take 2 air filters that are the same make and model, for a bike that is. Duct tape off half of one of them, and leave the other one wide open. Stick them both on the vac as I said, and you WILL notice the difference. And as I said it will also be obvious how good your filter oil is as well, no oil inside the vac pipe and your oil isn't too thin anyway. And actually if there is no restriction with ALLOT of cfm, then there will be even less with a small cfm. Holly prints allot of stuff on this subject, and anyone wishing to learn about air flow can learn allot from their books.

[robinjo]

Have you done any calculations how much cfm a GS1100 or 1000 flows at 9k rpm in comparison to your vacuumcleaner? Or how about liters per minute.

[sv650]

CFM

Approx 175?

SV

[Keith Winter]

175cfm would be really the max that a VM26ss carb will flow. I did all the caculations on this stuff when I was putting my 1000 together, and it seemed to me the math worked out to around 160cfm, but I have to find my book with all this stuff to be sure. That was using a pumping loss figure of 30%, and I think thats being generous. On the 1100/1150, with their 4 valve heads, I have no clue. My shop vac I THINK was 300cfm, but I'm going to check that. 300cfm with no hose loss, that it is. I use a peice of smooth bore large hose, 6 feet long, when I play around so there isn't much loss. I will find the math you use for all this stuff, re-calculate and post some data if anyone want's it.

[robinjo]

175cfm would be really the max that a VM26ss carb will flow. I did all the calculations on this stuff when I was putting my 1000 together, and it seemed to me the math worked out to around 160cfm, but I have to find my book with all this stuff to be sure. That was using a pumping loss figure of 30%, and I think thats being generous. On the 1100/1150, with their 4 valve heads, I have no clue. My shop vac I THINK was 300cfm, but I'm going to check that. 300cfm with no hose loss, that it is. I use a piece of smooth bore large hose, 6 feet long, when I play around so there isn't much loss. I will find the math you use for all this stuff, re-calculate and post some data if anyone wants it.

PLEASE DO! I love this stuff. I'm also interested how much one of my 34mm CV flows in comparison to a 26 or 28mm VM carb. Ans another thing...if you still have the stock air box with the conical filter in it that will need to cope with all 4 carbs their suction but not at the same time right? Or could it overlap a little with resonances and shock waves in effect?

[Keith Winter]

Robin;
I also like this stuff, always have. There are formula's for air flow through things like carbs, and other holes, and they are different than the math for fuel. Air is compressable, gas is not, so the calculations are different than the ones you use for main jets, ect, ect. If you don't mind doing a little work with a Dremel tool, you can get your stock carbs to flow more air. But you never gain in one area with out some loss some where else! Back when I built and sometimes raced inline Mercury outboards, I learned allot about air flow improvements. I'm going for a week long ride on my 1000 on the 14th, so I have no time right now to dig up all this stuff. When I get back though I will find all my books and make a point of sending some info to you. By the way, I know outboards are 2 cycle engines, but pumping loss and air flow loss is the same for any internal combustion engine.
Keith

[Nerobro]

I would KILL to know the CFM rating of my 29mm roundslide carbs :-) engine analizer will thank you.