Notices
Glow Engines Discuss RC glow engines

Welcome to Club SAITO !

Old 09-08-2011, 08:44 PM
  #20776  
My Feedback: (15)
 
frets24's Avatar
 
Join Date: Dec 2007
Location: charlotte, NC
Posts: 1,245
Likes: 0
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !


ORIGINAL: JariV

That's not a real velocity stack. The mouth of the stack should be considerably larger and the contour is very important. I did a stack into my radial Saito and power went up by 10 % after adjusting the needles.

More info please pics and specifications would be nice for those of us who may like to copy your plans( if you will allow of course)
Old 09-09-2011, 12:25 AM
  #20777  
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !

ORIGINAL: JariV
That's not a real velocity stack. The mouth of the stack should be considerably larger and the contour is very important. I did a stack into my radial Saito and power went up by 10 % after adjusting the needles.
Guys please confirm or deny if the velocity stack does provide a better mix of the fuel-air intake charge,
so leads to a more efficient burn!
Old 09-09-2011, 04:07 AM
  #20778  
 
Join Date: Feb 2007
Location: Dearborn, MI
Posts: 3,216
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !


ORIGINAL: Kostas1

ORIGINAL: JariV
That's not a real velocity stack. The mouth of the stack should be considerably larger and the contour is very important. I did a stack into my radial Saito and power went up by 10 % after adjusting the needles.
Guys please confirm or deny if the velocity stack does provide a better mix of the fuel-air intake charge,
so leads to a more efficient burn!
I know that in automotive engines, a longer intake runner gives better low-end torque. Maybe that can apply here (if done properly)?
Old 09-09-2011, 04:23 AM
  #20779  
 
earlwb's Avatar
 
Join Date: Aug 2009
Location: Grapevine, TX
Posts: 5,993
Likes: 0
Received 3 Likes on 3 Posts
Default RE: Welcome to Club SAITO !

ORIGINAL: Kostas1
ORIGINAL: JariV
That's not a real velocity stack. The mouth of the stack should be considerably larger and the contour is very important. I did a stack into my radial Saito and power went up by 10 % after adjusting the needles.
Guys please confirm or deny if the velocity stack does provide a better mix of the fuel-air intake charge,
so leads to a more efficient burn!
It does not improve engine performance. it improves fuel consumption and how the engine behaves in the air when flying.

The short intake stack on the Saito engines, improves fuel consumption. When a engine is running there is a backflow occuring where a small plume or cloud of fuel droplets form just outside of the carb's intake. On a test bench you can hold your hand behind the engine running and feel little tiny cold droplets of fuel hitting your hand. the intake stack helps to keep that fuel inside where it can be run through the engine. So your fuel economy goes up with the engine and it gets more fuel. Sometimes you even have to lean the engine out a little bit more too. Also if the engine is out in the open on a airplane the airflow and turbulence around the engine and carb upsets that cloud of fuel just outside the carb and aggravates the situation. The intake stack helps prevent that too. 2 stroke engines have it more pronounced as well. They sometimes call the intake stack "anti-reversion" flow device. The 2 cycle engines with a short intake tube tend to spit fuel like crazy too, they call that "reversion" flow. The high performance 2 strokes are really bad at it with their more radicical port timing. the newer control line engines all have long intake stacks on the intake venturi nowadays as well. This helps prevent the fuel spitting and also the effects of the airflow in and around the intake causing interference too. The air flowing around the carb can actually cause momentary reverses where it actually causes intake suction to go away, this causes misfiring or momentary loss of power in the air in radical aerobatics. So the intake stack helps to prevent that from occurring.

Probably a good example of the effect is the HarleyDavidson V-twin engine with carb in between. Due to the uneven flow characteristics of the intake, a large plume or cloud of raw fuel forms just outside of the carb. If you ride a HD motorcycle at slower speeds up a long uphill mountain road, you'll see raw fuel dripping off the air filter box, on the engines with carburetors on them. it is something of a fire hazard too, as I have seen guys smoking cigarettes with their right hand, holding the lit cigarette right down next to the air filter box like that before. yes a few bikes have caught fire in that situation too.

For performance the intake stack needs to be designed as a velocity stack. It is not a velocity stack at this time.
Old 09-09-2011, 04:30 AM
  #20780  
My Feedback: (102)
 
Hobbsy's Avatar
 
Join Date: Dec 2001
Location: Colonial Beach, VA
Posts: 20,370
Likes: 0
Received 25 Likes on 25 Posts
Default RE: Welcome to Club SAITO !

A tuned intake stack could also make the engine peaky by increasing torque at a certain rpm but fall flat on its face above or below that rpm.
Old 09-09-2011, 05:04 AM
  #20781  
 
Rudolph Hart's Avatar
 
Join Date: Apr 2008
Location: Perth, AUSTRALIA
Posts: 4,383
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Welcome to Club SAITO !

Trust you to be sensible and spoil the show earl i think frets asks a good question mate.If costus all keeps writing his posts in capital green red and orange colours i'm going to give that bugger a black eye or two,howdy mate..
Old 09-09-2011, 05:08 AM
  #20782  
 
Join Date: Feb 2007
Location: Dearborn, MI
Posts: 3,216
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !

The Saito 1.8 that I purchased used came with a velocity stack already installed.
Old 09-09-2011, 05:10 AM
  #20783  
 
Join Date: Feb 2007
Location: Dearborn, MI
Posts: 3,216
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !


ORIGINAL: Old Fart

Trust you to be sensible and spoil the show earl i think frets asks a good question mate.If costus all keeps writing his posts in capital green red and orange colours i'm going to give that bugger a black eye or two,howdy mate..
I thought he does the red and green colors to give the Christmas Spirit effect.
Old 09-09-2011, 05:48 AM
  #20784  
My Feedback: (102)
 
Hobbsy's Avatar
 
Join Date: Dec 2001
Location: Colonial Beach, VA
Posts: 20,370
Likes: 0
Received 25 Likes on 25 Posts
Default RE: Welcome to Club SAITO !

Here is the reason for the "dancing fuel" at the entrance to the carb.
Picture #1==intake valve opening
Picture #2==exhaust valve closed, both are open between these pictures.
Picture #3==intake valve closed, as you can see the intake valve is open for a long time, picture #3 is also the beginning of the compression stroke.
Attached Thumbnails Click image for larger version

Name:	Vt57294.jpg
Views:	29
Size:	50.3 KB
ID:	1659836   Click image for larger version

Name:	Ez83140.jpg
Views:	32
Size:	53.2 KB
ID:	1659837   Click image for larger version

Name:	Ze86956.jpg
Views:	35
Size:	50.6 KB
ID:	1659838  
Old 09-09-2011, 06:33 AM
  #20785  
 
earlwb's Avatar
 
Join Date: Aug 2009
Location: Grapevine, TX
Posts: 5,993
Likes: 0
Received 3 Likes on 3 Posts
Default RE: Welcome to Club SAITO !

I remember years ago seeing guys set the fiberglass insulation on the inside of their car's hood on fire, when they ran them without an air filter too.
They would put in a hotter camshaft, bigger carb, et cetera. But now the engine tended to spit fuel out of the carb. You can to put on a good air filter intake system to keep the gasoline vapor cloud just outside of the carb in control.


The Saito 1.8 that I purchased used came with a velocity stack already installed. <span class="info"> </span>
I think they had to do that on some engines as the carb was affected a lot by the air flow patterns around it during flight and aerobatics. You could perform something like a high speed snap roll and the engine would stumble, hesitate, and even stall out and quit on you. The quick burst of air across the mouth of the carb would negate the suction and the engine would stop as it couldn't draw fuel momentarily.


The gasoline engines with pumper carbs were even more affected, as the pumper carb had a air pressure equalization orifice that was affected by the rapid air flow of a airplane in flight. especially with the side mounted carb on the engines. So the intake stack was a big improvement in having the engine run reliably and well.


You know in thinking about it, I suppose it does improve performance, not in speed or RPMs or horsepower per se, but in reliability and consistency and good running.



Old 09-09-2011, 06:45 AM
  #20786  
Senior Member
 
Join Date: Jul 2003
Location: Near Princeton, WV
Posts: 157
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Welcome to Club SAITO !

The intake valve stays open past Bottom Dead Center because the intake runner has velocity, this velocity continues to push air into the cylinder after BDC. This changes a lot depending of the rpm of the engine, and length of the intake runner.

The reversion happens because of this velocity too. When the intake valve closes the air compresses on the intake valve, then bounces back creating a revers flow.

As mentioned earlier runner length can be used to tun an engine by setting up a resonance at a desired rpm, but the lengths required are prohibitive. around 8" for an engine at 10K, exhaust figures differently. From something I read from a Chrysler engineer.

Intake
Code:
 84000/runner inches.  = rpm
Code:
205000/runner inches=rpm
Obviously there might be better numbers now days, but this was muscle car era.

Velocity stack design is very tricky for optional performance. Here is a little run down on the art. http://en.wikipedia.org/wiki/Velocity_stack there is a link to a file named bellmouth.zip


Cory
Old 09-09-2011, 06:53 AM
  #20787  
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !

I am quoteing the following information from wikipedia.



A velocity stack is a trumpet-shaped device of differing lengths which is fitted to the air entry of an engine's intake system, carburetor or fuel injection. It is designed to:

1. Allow smooth and even entry of air at high velocities into the intake tract with the flow stream adhering to the pipe walls.[citation needed]
2. Modify the dynamic tuning range of the intake tract by functioning as a resonating pipe which can adjust the frequency of pressure pulses, based on its length, within the tract.

In the real world, on high-rpm IR IC engine, using a minimum amount of inlet radius gives the best wave strength and a power boost of 2% to 4% over a 3000 to 3500 rpm range. Using a larger radius, like 3/4", broadens out the resonant pressure wave rpm range, but the compression boosting pressure wave is greatly diminished and almost unnoticed by the engine.
Old 09-09-2011, 07:01 AM
  #20788  
blw
My Feedback: (3)
 
blw's Avatar
 
Join Date: Mar 2004
Location: Opelika, AL
Posts: 9,447
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Welcome to Club SAITO !

You can appreciate the potential effect of the velocity stack for small Saitos by putting one on a 125 and seeing the engine lose performance.
Old 09-09-2011, 07:10 AM
  #20789  
Senior Member
 
Join Date: Jul 2003
Location: Near Princeton, WV
Posts: 157
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Welcome to Club SAITO !


ORIGINAL: blw

You can appreciate the potential effect of the velocity stack for small Saitos by putting one on a 125 and seeing the engine lose performance.
I thought they were smaller than the 1.25's carb bore? If so chocking the engine is a different subject.

Cory
Old 09-09-2011, 07:16 AM
  #20790  
 
Join Date: Feb 2007
Location: Dearborn, MI
Posts: 3,216
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !


ORIGINAL: blw

You can appreciate the potential effect of the velocity stack for small Saitos by putting one on a 125 and seeing the engine lose performance.
Hmmm!!! I will keep that in mind for my 1.8 Saito. I only ran WITH the stack installed. I might try to remove it, but not sure if I will get to it this flying season, it is already getting rainy and windy.[&o]
Old 09-09-2011, 07:23 AM
  #20791  
 
Join Date: Feb 2007
Location: Dearborn, MI
Posts: 3,216
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !

The valve opening overlap plus longer intake runners cause a supercharging effect of the fuel/air mixture entering the cylinder.

In modern automobiles, the tube upstream of the throttle body is a complex design (involves a whole bunch of engineering). The plastic tube upstream of the throttle body is called the "zip tube" and is designed to improve airflow and dampen out noise. So, the backflow of fuel is not a concern due to port or direct fuel injection, but intake air hissing noise is a big concern. Intake air hissing noise is not something we are concerned about in this hobby.
Old 09-09-2011, 08:36 AM
  #20792  
Senior Member
 
Join Date: Dec 2008
Location: Athens, GREECE
Posts: 136
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Welcome to Club SAITO !

An example of one model engine with a real velocity stack is the OS 49PI Type II Rotary. It gave the engine the ability to swing a larger prop than the previous model.
Old 09-09-2011, 12:12 PM
  #20793  
My Feedback: (102)
 
Hobbsy's Avatar
 
Join Date: Dec 2001
Location: Colonial Beach, VA
Posts: 20,370
Likes: 0
Received 25 Likes on 25 Posts
Default RE: Welcome to Club SAITO !

H, the reason the 1.25 loses about 150 rpm is that the velocity stack for the rest of the smaller Saitos has a smaller id than the 1.25s venturi. The 1.00 on down are fine, the .40a and the little .30 have there's cast in to the carb. The .40a stack is about 7/16" deep & convergent.
Attached Thumbnails Click image for larger version

Name:	Lj23557.jpg
Views:	30
Size:	40.9 KB
ID:	1659907  
Old 09-09-2011, 12:34 PM
  #20794  
 
earlwb's Avatar
 
Join Date: Aug 2009
Location: Grapevine, TX
Posts: 5,993
Likes: 0
Received 3 Likes on 3 Posts
Default RE: Welcome to Club SAITO !

ORIGINAL: Nikolas K
An example of one model engine with a real velocity stack is the OS 49PI Type II Rotary. It gave the engine the ability to swing a larger prop than the previous model.
Yes it looks like they have a pretty good one on the carb there.



I noticed that the control line engines all started putting on a longer venturi intake too. But it isn't a velocity stack though.


Old 09-09-2011, 12:37 PM
  #20795  
 
Join Date: Feb 2007
Location: Dearborn, MI
Posts: 3,216
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !


ORIGINAL: earlwb

ORIGINAL: Nikolas K
An example of one model engine with a real velocity stack is the OS 49PI Type II Rotary. It gave the engine the ability to swing a larger prop than the previous model.
Yes it looks like they have a pretty good one on the carb there.

[img][/img]

The minute somebody says ROTARY or RADIAL, I know I can't afford it!!!
Old 09-09-2011, 12:40 PM
  #20796  
 
Join Date: Feb 2007
Location: Dearborn, MI
Posts: 3,216
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !


ORIGINAL: earlwb

ORIGINAL: Nikolas K
An example of one model engine with a real velocity stack is the OS 49PI Type II Rotary. It gave the engine the ability to swing a larger prop than the previous model.
Yes it looks like they have a pretty good one on the carb there.

[img][/img]

I noticed that the control line engines all started putting on a longer venturi intake too. But it isn't a velocity stack though.
[img][/img]

Hey Earl, what is that wild looking single cylinder engine? Check out the massive front bearing on it!!! Too bad you can't get an RC version for it.
Old 09-09-2011, 02:08 PM
  #20797  
 
earlwb's Avatar
 
Join Date: Aug 2009
Location: Grapevine, TX
Posts: 5,993
Likes: 0
Received 3 Likes on 3 Posts
Default RE: Welcome to Club SAITO !

ORIGINAL: hsukaria
Hey Earl, what is that wild looking single cylinder engine? Check out the massive front bearing on it!!! Too bad you can't get an RC version for it.

Yes they have a RC carb version too. yes they put in a big crank and it needs a big pair of bearings too.



Old 09-09-2011, 02:46 PM
  #20798  
 
Join Date: Feb 2007
Location: Dearborn, MI
Posts: 3,216
Received 1 Like on 1 Post
Default RE: Welcome to Club SAITO !


ORIGINAL: earlwb

ORIGINAL: hsukaria
Hey Earl, what is that wild looking single cylinder engine? Check out the massive front bearing on it!!! Too bad you can't get an RC version for it.

Yes they have a RC carb version too. [img][/img] yes they put in a big crank and it needs a big pair of bearings too.

[img][/img]

what size displacement is it?
Old 09-09-2011, 04:15 PM
  #20799  
My Feedback: (5)
 
AmishWarlord's Avatar
 
Join Date: Oct 2002
Location: Indian Trail, NC
Posts: 2,939
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Welcome to Club SAITO !

I saw this 150 basket case on ebay.
http://www.ebay.com/itm/Saito-150-RC...item2a13e033dc


"not yet broken in" Oh this engine looks really "Broken in" to me. Why would someone strip down an engine that wasn't even broken in? Crash?

"Saito 150 RC engine", No this is used parts for a Saito 150 engine, not even all the parts for a Saito 150 engine.
Old 09-09-2011, 04:19 PM
  #20800  
My Feedback: (102)
 
Hobbsy's Avatar
 
Join Date: Dec 2001
Location: Colonial Beach, VA
Posts: 20,370
Likes: 0
Received 25 Likes on 25 Posts
Default RE: Welcome to Club SAITO !

The backplate appears to have been violated some way, like maybe the crank being driven into it while under power.

Thread Tools
Search this Thread

Contact Us - Manage Preferences Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.