V-Twin Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
60 Posts
Discussion Starter #1
I am not sure where to post this question, but since I have a TC88 I figured I would start here.

I want to change up the look of my FXSTI a little bit and I was wondering if putting on a velocity stack would cause any problems if I were to put one on my bike. My bike looks so generic so I figured what little things I can do would help.

Currently I have Stage One, SERT and a V&H Propipe HS.

Are velocity stacks primarily used on bigger engines or am I ok to use one on my bike?

Also, if it is ok, can anyone recommend what type/size/make to purchase?

Thank you.
 

·
Registered
Joined
·
60 Posts
Discussion Starter #3
thanks for the reply.......head up my a * *...... did not think about the air filter......

you answered my question...thanks.
 

·
Known Associate
Joined
·
175 Posts
Even if the stack has a filter or screen in it, they're still worthless pass 100mph, as the air passing by the inlet is traveling too fast and cannot make it into the engine: bottom line, your engine starves for air...

All those pretty bikes with glistening chrome and polished velocity stacks are just for show. They don't run worth a s**t at high speeds.
 

·
Registered
Joined
·
9,250 Posts
Slammed,

Plenty of other air cleaner options if you're looking for style. Not many really seem to add much performance, but they don't detract either and they look cool.

More into performance myself, but those forcewinders and wimmer set-ups look good to me.
 

·
Banned
Joined
·
5,114 Posts
Mad Dog said:
Even if the stack has a filter or screen in it, they're still worthless pass 100mph, as the air passing by the inlet is traveling too fast and cannot make it into the engine: bottom line, your engine starves for air...

All those pretty bikes with glistening chrome and polished velocity stacks are just for show. They don't run worth a s**t at high speeds.
Sorry Mad dog but I highly disagree with your top end statment....Velocity stacks are for intake trac tuning and add more velocity to the engines V.E. which is more air inturns gives more power. The intake trac air velocity is 690 feet per second at WOT, thats 60% the speed of sound. If the intake velocity is trully this strong 100 mph will not effect it. You would have to go two and a half foot ball fields in less than one second to over come the intake velocity....that my friend is faster than Super Man out of a phone booth.
Velocity stacks are for go....
 

·
Life is what you make it
Joined
·
3,568 Posts
Correct me if I am wrong. But on the dyno you will see no difference going down the road there would be a difference. I know from Drag racing my car with a hood scoop, if I left the base pan off the scoop that sealed the scoop to the carb I would loose a good tenth of a second on my ET. Thats a lot in Drag racing on a 10.80 car. I often have wondered why there isnt a better scoop type air cleaner out there for the bikes. I guess there is that hypercharger thing ? Something clean simple like a pro stock scoop for a car but smaller :hmmm:
 

·
Registered
Joined
·
1,460 Posts
Mad Dog said:
Even if the stack has a filter or screen in it, they're still worthless pass 100mph, as the air passing by the inlet is traveling too fast and cannot make it into the engine: bottom line, your engine starves for air...

All those pretty bikes with glistening chrome and polished velocity stacks are just for show. They don't run worth a s**t at high speeds.
Ahh Mad Dog...........you might want to step back on that remark as almost every top fuel bike, dragster, hilborn injected V8 etc. etc. etc. all run stacks at speeds way above 100mpg.

All the best, Ozzie
 

·
Registered
Joined
·
1,460 Posts
hotshotfxdl said:
Correct me if I am wrong. But on the dyno you will see no difference going down the road there would be a difference. I know from Drag racing my car with a hood scoop, if I left the base pan off the scoop that sealed the scoop to the carb I would loose a good tenth of a second on my ET. Thats a lot in Drag racing on a 10.80 car. I often have wondered why there isnt a better scoop type air cleaner out there for the bikes. I guess there is that hypercharger thing ? Something clean simple like a pro stock scoop for a car but smaller :hmmm:
I think it was Carl Morrow that actually put a small cup on the inside trailing edge of his stacks which grabbed the air and showed an increase in air velocity through his carb setups..........like a ram effect with good success.

All the best, Ozzie
 

·
Registered
Joined
·
4,741 Posts
I know my Buddy's dragbike works pretty dang good at 145mph with a tuned velocity stack on it. It does have the trailing edge cup also mentioned. He is also starting to experiment with the Novi concentric stack design also.

Here's a picture of the X Mod bike, it's a 113" TC that runs consistent 8.9's at 145mph in the 1/4.
 

·
Legend in my own mind
Joined
·
157 Posts
Some of the LSR folks had pretty significant issues with straight velocity stacks changing the mixture at speed. Whether you believe it creates low pressure or high pressure; you have to agree that any change in pressure does change the fuel metering in a way that's not able to be reproduced on the dyno.

Comparing drag bikes with street bikes is a bit off the mark. Guys running Alcohol and Fuel use dump cans and any other number of ways to make sure they don't lean out - the carb is not tuned to the degree a street bike (or LSR bike) is. Stack there are used for intake port tuning and not any ram air effect. You do most often see scoops covering these stacks.

If a guy wants a different look, the Forcewinder is a pretty good choice. The lack of a good filter on most straight stacks does make that family of stacks a bad choice for the street.
 

·
Registered
Joined
·
4,741 Posts
The point is, velocity stacks work at very high speeds, you just have to know how to use them. As I understand it, the trailing edge cup is there to prevent the siphoning air/fuel out of the motor on the top end at high speed to prevent lean out. Kind of like blowing across an open Coke bottle, if you did it hard enough, you could begin to lift the contents out of the bottle. I'm pretty sure the cup is not there for a ram effect though. Tuning the velocity stack on the intake is pretty much the same reasoning for tuning the pipes on the exhaust. Bob at RB Racing told me once about the origins of this siphoning issues at Bonneville years ago, pretty interesting story. The trailing edge cup pretty much has become a standard in all forms of racing that involves high speeds. Recently, the Novi dual concentric stack has been making a statement though. My buddy is just starting to play with it.

The dragbike carb.........
Well, all I can tell you is from my limited involvement, that it has to idle well enough so the motor doesn't stall(no starter on the dragbike), it has 3 fuel circuits and it is the main focus of attention between rounds keeping it jetted right with the changing atmospherics. Maybe even more finely tuned at WOT than a street bike carb? Oh, and it uses an extra big extended fuel bowl to keep the motor from starving out on the top end during the pass.

Cool stuff!
 

·
semi-retired
Joined
·
1,844 Posts
tp enginering

Slammed Ride said:
I am not sure where to post this question, but since I have a TC88 I figured I would start here.

I want to change up the look of my FXSTI a little bit and I was wondering if putting on a velocity stack would cause any problems if I were to put one on my bike. My bike looks so generic so I figured what little things I can do would help.

Currently I have Stage One, SERT and a V&H Propipe HS.

Are velocity stacks primarily used on bigger engines or am I ok to use one on my bike?

Also, if it is ok, can anyone recommend what type/size/make to purchase?

Thank you.
If you want something different,check out tp's scramjet airfilter,looks good.
 

·
Liberal Slayer
Joined
·
212 Posts
All the insight into the stack is great, but no one answered Slammed Ride's question about what kind of stack if good for his EFI bike. I was kinda wondering the same thing. I have never seen a Velocity Stack for an EFI bike. Do they even make them yet for EFI bikes?

I am not saying that I would ride 10,000 miles with one on, but maybe I would like to put one on for a bike show for or something just to change it up a bit when I desire. Believe me, I understand the cons of the stack, I still thinks it looks cool. I still wouldnt chance hurting my motor by running it day in and day out.

With that said, can anyone commment about Velocity Stacks and EFI TC-88/95 motors. Thanks
 
1 - 14 of 14 Posts
Top