supercharger

[Denny]

Bob, where did you get my video from?

 

[A Manco Dingo]

You i am in high school and we just had a lockdown someone had a wepon and we where in a lock down for 50mins

 

[Denny]

It wasn’t me!

 

[Thepartsguy]

We’re getting there

 

[BaconBitRacing]

Hey! Did you get oil on Momma's picnic blanket!?!

 

[A Manco Dingo]

We’re getting thereView attachment 147439View attachment 147441View attachment 147442

What paint did you use

 

[A Manco Dingo]

Alot has happend to my go kart

 

[Denny]

And none of it good?

 

[Thepartsguy]

Hey! Did you get oil on Momma's picnic blanket!?!

We are in the clear today’s wash day! Clean and back on the kitchen table before anyone noticed the oil stains!

 

[Thepartsguy]

What paint did you use

Rusto Safety red and I also like ford safety blue it paints up so well.

 

[Thepartsguy]

Can someone speak up about backfires?? It won’t blow this pump up?

 

[65ShelbyClone]

Well yeah, it could.

 

[karte_m0lim]

does it suck?
carburetor:

 

[Thepartsguy]

does it suck?
carburetor:
View attachment 147447

Ahaahahhahahahahahahahahahah

 

[A Manco Dingo]

Hey will a 30mm be to big for a 212

 

[Rat]

Hey will a 30mm be to big for a 212

WAAAY to big

26mm ABSOLUTE MAX, 24mm is a lot easier to dial in and tends to run better across all throttle positions. You will need jets to dial it in with

I have a Koso PWK (Keihin copy) with a screened velocity stack on a Husqvarna 208 in the 2000ft alt range and it's jetted in the "normal range" 38p/120m needle clip at default (#3 position)... it has other work done so that it really winds up.

Honest evaluation though, carb is one of the last upgrades one should worry about... in part because the variety of carb you're talking about requires popping the cover and pulling the crank out to gut the governor assembly so that you don't end up having it become shrapnel destroying the engine.

Heavier (18 or 22) weight valve springs with split keepers should always be first thing even if its the only thing done.

An unrestricted ignition coil should be second because most stock coils just won't fire correctly above 4300, and the few that do won't get too far above 4800.

After that things get more technical but still supercede the neccisarity to upgrade or swap the carb.

 

[A Manco Dingo]

WAAAY to big

26mm ABSOLUTE MAX, 24mm is a lot easier to dial in and tends to run better across all throttle positions. You will need jets to dial it in with

I have a Koso PWK (Keihin copy) with a screened velocity stack on a Husqvarna 208 in the 2000ft alt range and it's jetted in the "normal range" 38p/120m needle clip at default (#3 position)... it has other work done so that it really winds up.

Honest evaluation though, carb is one of the last upgrades one should worry about... in part because the variety of carb you're talking about requires popping the cover and pulling the crank out to gut the governor assembly so that you don't end up having it become shrapnel destroying the engine.

Heavier (18 or 22) weight valve springs with split keepers should always be first thing even if its the only thing done.

An unrestricted ignition coil should be second because most stock coils just won't fire correctly above 4300, and the few that do won't get too far above 4800.

After that things get more technical but still supercede the neccisarity to upgrade or swap the carb.

I was going to get heaver valve springs but thanks i though 30mm was a little big

 

[Rat]

I was going to get heaver valve springs but thanks i though 30mm was a little big

The following equation assumes a mechanically impossible 100% VFE (volumetric flow efficiency) rate to [over] simplify a lot of measuring, math, less than cost effective flow testing, and more math before even more math.

√(D)2=cmf

√(212)2= 29.12 rule if thumb is to round down to the nearest actual carburetor size, this gets you 28 which is to large for 80% VFE (at best) this brings us to 26 as the maximum but not ideal leaving 24mm as the optimum

 

[bob58o]

I think I’m planning on using a 30mm on supercharged 212.

100% VE with forced induction?

in the following formula we will use the constant, K, as being proportional to VE.

0.65 for crappy VE
0.78 for average VE
0.90 for race engine (ported, gasket matched,…)

I’ll use 0.925 for forced induction, but maybe 1.00 works too. Maybe depends on quality of blower.

D = K x Square Root(C x n)

where:
D=carb diameter, in millimeters
K= constant between 0.65 and 0.90
(Higher than 0.90 for forced induction)
C=cylinder displacement, in cubic centimeters
n= RPM at peak power/1,000

K= 0.925
C = 212cc
N = 5000 / 1000 = 5 (rpm = 5000)

D= 0.925 * SqRt(212 * 5)
D= 0.925 * SqRt (1060)
D= 0.925 * 32.6

D= 30mm

I could probably create a better formula that uses intake valve size as an input so that for NA engines, the carb diameter isn’t ever bigger than the intake valve.

In general for NA engines, maybe….
If looking for top end…

24mm carb for 25mm intake valve
26mm carb for 27mm intake valve
28mm carb for 28.5mm intake valve

smaller carbs if looking for snappy throttle response and stop/go driving

 

[Rat]

I think I’m planning on using a 30mm on supercharged 212.

100% VE with forced induction?

in the following formula we will use the constant, K, as being proportional to VE.

0.65 for crappy VE
0.78 for average VE
0.90 for race engine (ported, gasket matched,…)

I’ll use 0.925 for forced induction, but maybe 1.00 works too. Maybe depends on quality of blower.

D = K x Square Root(C x n)

where:
D=carb diameter, in millimeters
K= constant between 0.65 and 0.90
(Higher than 0.90 for forced induction)
C=cylinder displacement, in cubic centimeters
n= RPM at peak power/1,000

K= 0.925
C = 212cc
N = 5000 / 1000 = 5 (rpm = 5000)

D= 0.925 * SqRt(212 * 5)
D= 0.925 * SqRt (1060)
D= 0.925 * 32.6

D= 30mm

I could probably create a better formula that uses intake valve size as an input so that for NA engines, the carb diameter isn’t ever bigger than the intake valve.

In general for NA engines, maybe….
24mm carb for 25mm intake valve
26mm carb for 27mm intake valve
28mm carb for 28.5mm intake valve

Ok then...

Doesnt change the bottom line being that a 24mm is the largest reasonable carb for a standard N/A set up that provides reliable performance and doest have unpredictable tuning responses. Depending on the intake manifold length used a 22mm could in some cases possibly perform better.

Not that it has been a specific goal, but 24mm doesn't exceed port size by a relevant amount.

When I say unpredictable responses I'm referring to the intake negative pressure exceeding or not meeting the carb metering abilities. When a carb is too lean you jet up, thats common tuner sense.
Unfortunately jets tend to come in limited size ranges so the real issue come into play when the rich/lean state is a direct result of an inappropriate carb size that is either sucking the jets too hard or not hard enough.