Extending the carb out?

Advertise with us
shop deals on amazon
Shop deals on ebay
Intlwaters

Help Support Intlwaters:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Samuel Hagan JR

Samuel Hagan JR

Well-Known Member
Joined
Jul 18, 2010
Messages
4,568
Has anyone tried adding a spacer maybe 3/8" or 1/2" in between the carb and the case to give the fuel more time to mix with the air?

Kinda like something you would see in a old carbureted car.
 
The longer intake tract would have the opposite effect. The fuel would be more likely to fall OUT of atomization due to the longer intake tract. I am assuming you are talking about a nitro engine
 
Last edited by a moderator:
Sam

I made a spacer for the black head Beta it is .200 thick and the carb can be rotated 90 deg.and it runs fine.See no changes in the way it runs.It a spacer between the carb and front housing.
 
Eric Canto said:
The longer intake tract would have the opposite effect. The fuel would be more likely to fall OUT of atomization due to the longer intake tract. I am assuming you are talking about a nitro engine
Click to expand...
Yes.

I'm assuming because the Nitro is mixed with the oil.
 
Intake tuning is not as important as exhaust tuning, but it does have an effect. From another forum:

Here is some info to help with the issue of what harmonic reflection is being used in an intake - use this formula to see what is happening.

In most cases the primary reflection is way to long to fit into any bike/ski etc ,but tuning to the second is sometimes possible but has a lesser effect over a narrower range.

The third reflection is usually the most doable, but again has less effect than a second harmonic.

RPM = 108K ( 1st hamonic ) 97K ( 2nd harmonic ) 54K ( 3rd harmonic ) / L ( inches )

So examples are 1st Harmonic 6000 rpm = 18",and 12,000 rpm = 9"

2nd Harmonic 6000 rpm = 16.16" and 12,000 rpm = 8.08"

3rd Harmonic 6000 rpm = 9" and 12,000 rpm = 4.5"

You can juggle the reflection number as well as tune for peak torque or tune for peak rpm, all depends upon the end use and the room available.

So for a bike needing intake tuning at 9000, the choice would have to be 3rd harmonic at 6.75" or going to the second would be near 12" so no way would that fit I would imagine.

Lohring Miller
 
The closure you can get the spray bar to the rotor,

Disk/Zimmerman, crank intake or drum intake it is the best

Years ago

Martin David had a motor with throttle exhaust and no carb or Venturi

The spray bar was in the housing where a Venturi or carb went

Thus the spray bar was as close as you could get to the rotor

Ran AWSOME
 
The "high rise" intakes on car engines were set up to increase the speed the air and fuel mixture entered the cylinders to increase the "swirl" effect for a more complete fuel burning. It had nothing to do with timing since the timing was set by the cam shaft as to when to open the valves and the distributor due to it's rotation speed(most being driven by the oil pump off the crankshaft) and vacuum advance. Since the carb would continuously spray fuel into the air flow being drawn through the carb barrels, it was just a matter of matching the carb jets to the air flow volume to get the right mix in a manner not that much different from us adjusting the needle valve to match the weather conditions, etc.
 
Last edited by a moderator:
Many years ago I was told that the closer the spray bar to the conrod, the greater the torque.

I do not know if it is true, but I trust the person that told me this in the first place.

Al Hobbs
 
johnsteltzer said:
If you want to see the carb move back check out this intake I made for my tiger king 27 it worked awesome
Click to expand...
Kudos....whether it increased power performance or not.....very clean and it looks just cool as hell.....I like it!!!

I really like the re-positioning of the carb to avoid water problems..... nice work....
 
We have done extensive testing on intake length and volumes. And whether it helps performance or not, just a heads up;

When you have a larger volume of atomized fuel between the carb and the case, when you get out of the throttle the engine can continue to rev - using up that extra until it is spent. This delayed reaction can be trouble in a heat race situation.
 
Samuel Hagan JR said:
Has anyone tried adding a spacer maybe 3/8" or 1/2" in between the carb and the case to give the fuel more time to mix with the air?

Kinda like something you would see in a old carbureted car.
Click to expand...
read the theory on FRICTION LOSS. You can google it.
 
We have tested two carb block lengths on 26 cc gas engines. The slightly shorter block helps top end power a little. Again, it's intake tuning as mentioned above that makes the difference.

Lohring Miller
 
The reason I think it work so well is the intake had no restrictions it flowed

So good and I know this sounds funny but the carb didn't know it was further away than stock location I know in a my prostreet nova with a tunnel ram you could run bigger carbs and gain more top in rpms and I thought it might work the same on this motor better air fuel mixture
 

Similar threads

M
Custom 32in nitro boat
Replies
1
Views
1K
dasboata
dasboata
Bradley Maglinger
Optimal ID pipe pressure size?
2
Replies
21
Views
3K
Bill Eilers
B
J
7PXR Failsafe Mystery-thoughts/advice
2 3
Replies
59
Views
4K
Mike Hughes
Mike Hughes
E
1/8 Miller sponson depth
Replies
2
Views
1K
Eugene Lyle
E
Ron Drake
Parts For Sale Nelson 45 Outboard & Parts Lot
Replies
3
Views
1K
Ron Drake
Ron Drake

Latest posts

Back
Top