SuzukiSavage.com - Quick question

MulletViper

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Quick question
03/13/12 at 13:51:36

Over the winter, I replaced the stock air box with something of my own design. I used exhaust pipe of the same diameter as the carb inlet and fashioned a homemade velocity stack. I also cut apart an air filter and attached it to the open end of the intake with a hose clamp.
Took it for a ride today and HOLY COW! She started right up without any choke, which is unusual. Even better, I opened her up and she pulls like a freakin night train. Grin

Got up to 55 in 4th gear and shifted to 5th, BAM! She started to die so I shifted back to 4th. Angry

On the plus side, she didn't backfire a single time, NOT EVEN ON SHUTDOWN. I guess those 4 months of winter tinkerin paid off.
Anywho, I tried turning the petcock to prime, still had the same problem. I'm thinking I need to go up a size with the main jet, but I could be wrong.

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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Quick question Reply #1 - 03/13/12 at 14:54:21 Next time, get er goin & reach down & pull the choke, while holdin the throttle steady. Id try that at about 1/2 throttle in second. PLay with that a while, different gears & 1/2 choke & full choke, You built a box that is greater in volume behind the filter than the cylinder volume, didnt you?
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MulletViper Junior Member Offline Professional Rivethead Posts: 53	Re: Quick question Reply #2 - 03/13/12 at 16:04:41 Here is an artists rendition of the intake if it helps diagnose
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verslagen1

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Re: Quick question
Reply #3 - 03/13/12 at 16:16:58

MulletViper wrote on 03/13/12 at 13:51:36:

Over the winter, I replaced the stock air box with something of my own design. I used exhaust pipe of the same diameter as the carb inlet and fashioned a homemade velocity stack.

How long? There's a magic length. My guess would be as long as the rubber ducky that's normally there. But, Diamond Jim found that it was something times the diameter.
Quote:

I also cut apart an air filter and attached it to the open end of the intake with a hose clamp.
Took it for a ride today and HOLY COW! She started right up without any choke, which is unusual. Even better, I opened her up and she pulls like a freakin night train. Grin

Got up to 55 in 4th gear and shifted to 5th, BAM! She started to die so I shifted back to 4th. Angry

On the plus side, she didn't backfire a single time, NOT EVEN ON SHUTDOWN. I guess those 4 months of winter tinkerin paid off.
Anywho, I tried turning the petcock to prime, still had the same problem. I'm thinking I need to go up a size with the main jet, but I could be wrong.

My guess is you're rich, and it'll get worse as you go faster.
The air filter will act as a restricter and that spinkter will only get tighter as the air goes faster. Since you velosity stack does not taper, the lead in will have an abrupter velocity change. If you can find a pod filter with a radiused lead in... this would be optimum.

So, replace your round disk filter with a pod filter to add more surface area and to create a gentler lead in.

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MulletViper Junior Member Offline Professional Rivethead Posts: 53	Re: Quick question Reply #4 - 03/13/12 at 16:35:17 It is 2 1/4 in diameter and about an inch longer than the stock rubber boot. So I need to add surface area to help stabilize the airflow, thanks for the help.
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verslagen1

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Re: Quick question
Reply #5 - 03/13/12 at 19:29:27

a lot of great work was done by this fella...

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1236788683/0

diamond jim wrote on 03/20/09 at 22:00:18:

Got the new honeycomb accelerator screen done. The straw lengths are 6x the diameter. I'll try it out tomorrow.

From a site about honeycombs and wind tunnels:
"The lateral components of mean velocity and of the larger turbulent eddies can be reduced more effectively by a honeycomb... cell length of the honeycomb should be at least six or eight times the cell diameter."

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Routy

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Re: Quick question
Reply #6 - 03/14/12 at 04:45:10

Your first clue that your homebuilt air intake was of a very bad design, was that you needed no choke when cold. To be that restrictive at that slow speed is the same as running 3/4 choke all the time. Any air filter that shows any restriction whatsoever at low speed, is not going to even run at hi speed. And it will wear rings and cyl walls in a short time.
The only way to increase airflow over the stock filter is to either have less screen mesh in the filter, or increase the sq inches of the filter area. And the stock air filter is already many times more sq inches than the diameter of the carb venturi intake. And I would NEVER decrease the filter mesh, as it will just pass more dirt....period !

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Rich
'07 S40 Blvd stocker, except drilled OEM exhaust and white spacer mod...1/2 (.055)

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justin_o_guy2

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Re: Quick question
Reply #7 - 03/14/12 at 11:22:16

Your first clue that your homebuilt air intake was of a very bad design, was that you needed no choke when cold.

Well No Duuh! & I completely missed that..

I did a little reading on intake design. When the intake pulse happens, the piston drops & vacuum hits the airbox, the more volume between filter & carb you have, the less it has work to draw the charge into the cylinder. If you were running & trying to avoid an oxygen debt, would your body be happy breathing thru a straw or would it be happier drawing air thru a 6 inch pipe? Surface area of the filter is crucial, if the filter is actually filtering, moreso when the airbox volume is decreased. Old Feller built a free flowing filter that filters just fine IMO, but its the same size as stock.Youd be more likely to be able to breathe enough if you had a1/2 inch inlet into a 5 gallon box than a 1/2 inch inlet into a 1/2 pint box,,So, its a combination of filter surface area & airbox volume to get max efficiency. People spend a lot of time on the exhaust & there are real gains to be made there, but at least the piston is pushing stuff out,, drawing in doesnt have near the mechanical advantage as p[ushing out. An efficient intake is a good thing, too. If you go small on the filter, then you have to make it pass air easily, which means less filtration.

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Routy Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 2280 Winston Oregon Gender:	Re: Quick question Reply #8 - 03/14/12 at 12:18:12 I couldn't have said it better than Jog......could I ? Right on,.....its a known fact,.....it is much easier to push air than to pull it. Playin around w/ these little cone etc filters, can burn you w/o even knowing it,......either by washing cyl walls, or by suckin dirt !
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