There She Blows

[bob58o]

It may not run yet, but it looks cool.

 

[BrownStainRacing]

It may not run yet, but it looks cool.

I love the look on the dogs face !!!!

Is he sayin "WTF have you done now" ???

 

[bob58o]

I love the look on the dogs face !!!!

Is he sayin "WTF have you done now" ???

The dog hates when I work on stuff. Mostly because I’m sitting on the floor and he thinks it’s play time.

His favorite game when I don’t give him enough attention is to steal sandpaper, sponges, paint brushes, silicone hose, connecting rod bearings, and then look at me at waiting for me to chase. If I don’t chase, he’ll just chew the heck out of it.

He loves sandpaper. Will chew it like bubble gum.

 

[65ShelbyClone]

I wonder if I have an 11/128th bit somewhere?

Or a #44.

 

[Denny]

I was just thinking the same thing, the dog knows better!

 

[bob58o]

Or a #44.

Yes I do believe a #44 drill bit is close to where I think I’ll need to be. I think that will give me around a 225 jet size.

It seems huge to me (that’s what she said) but I’m not very familiar with how the carb circuit “signal” changes with Venturi size and especially when in a suck through set up.

For example with same engine, if a 22mm carb requires a 120 jet, when going to a bigger carb, does this reduce “signal” requiring a larger jet to maintain AFR?

I still don’t know why this style intake would require such a large jet.

It says 170-190 mikuni size jet with this intake and a VM22 carb, compared to 100 size stock jet. The intake did get icy cold before. I don’t know where all the extra fuel goes? Into my oil? Perhaps there’s isn’t more fuel? Perhaps the larger jet is just required because the signal is weaker?

Only part of that intake is being used now, but it’s now a much longer version of it.

 

[bob58o]

Horse powers?
All the Torques and at 5252 RPM,

1.00 Puppy Powers

 

[65ShelbyClone]

For example with same engine, if a 22mm carb requires a 120 jet, when going to a bigger carb, does this reduce “signal” requiring a larger jet to maintain AFR?

Generally yes that is what happens. All else being equal, a larger carb throat reduces velocity which is what the venturi effect relies on to make the low pressure that pulls fuel through the jets.

The Keihin jet sizes you're talking about are absolutely enormous, even for E85.

 

[bob58o]

Generally yes that is what happens. All else being equal, a larger carb throat reduces velocity which is what the venturi effect relies on to make the low pressure that pulls fuel through the jets.

The Keihin jet sizes you're talking about are absolutely enormous, even for E85.

Thanks for the reply.
Using that 35% increase in area of orifice vs the stock carb jetting would give something closer to 155 or 160 for the main jet vs the 135 I pulled out of it.

Well I guess the correct jetting is somewhere between 150 and 250.

I just checked my booger welded exhaust bung and it appears to be air tight. Good thing I have the O2 sensor.

My fuel pump pulls 1 amp.
I think the O2 sensor might use up to 1.4 amps.

The charging system makes 3 amps I think.

I don’t this engine is going to run long enough to recharge the battery.

I think the starter should still work ok. The cam still has the compression release mechanism.

 

[bob58o]

I guess 0.8 lambda is on the fat side of stoich, and the internet said 0.8 lambda for E-85 is somewhere around 8:1 AFR (gasoline ~12:1)

 

[65ShelbyClone]

Before you finalize brackets for the blower, you'll need to turn it over so the drain plug is facing down. It is currently oriented to blow air backward out of the carb. Ignore this, brain fade on my part.

You have probably seen this already, but I hadn't until now.

Yeah, that's way too much boost. Look at the timing line on that spark plug. He burned it back that far without any load on the engine.

 

[bob58o]

22mm carb = 380 mm^2
30mm carb = 707 mm^2

So if a 30mm carb has about twice the throat area compared to a 22mm carb, would it need a jet with twice the orifice area?

PV=nRT
Ideal gas law is the only thing so remember from school and never know how to use it properly.

If area of the Venturi is doubled, I assume the volume of the throat is also doubled. If volume doubles and we assume constant ambient temp for both systems, the change in pressure would be halved.

Perhaps a 30mm carb needs a jet with twice the orifice area than a 22mm carb would need?

If a 22mm uses around 100, twice that for a 30mm would be about 141. Add 35 % area to that it’s around 164.

 

[bob58o]

Hmmm. Air gets compressed around the outside of the rotor housing chamber thing right?

 

[bob58o]

Red beard also has his pulley driven from the crank side. Blower oriented same as mine.

 

[bob58o]

Before you finalize brackets for the blower, you'll need to turn it over so the drain plug is facing down. It is currently oriented to blow air backward out of the carb.

You have probably seen this already, but I hadn't until now.

Yeah, that's way too much boost. Look at the timing line on that spark plug. He burned it back that far without any load on the engine.

I’m not sure I watched it all the way through. I didn’t hear him talk about tuning. I’ll watch it again, but maybe he talks about it in previous video on propane?

 

[bob58o]

Is this a reasonable location to monitor vacuum / boost ?

 

[Denny]

Here’s a little free tip add 1.0 ounces of marvel mystery oil to a gallon of e85. It is a dry fuel and will help the blower live longer and save a little corrosion from the carb.

 

[bob58o]

So this was Red Beards plug.
Assuming stock plug heat range
No load.
Using stock Polaris 500 carb
Stock Jetting
Stock Ignition Timing (no clue on 440cc)
I think big blocks come at around 24-25 BTDC
1:1 Pulley Ratio
300cc blower
440cc engine (220cc per stroke)

I believe my math puts that around 5 lbs of boost.

Not sure how he makes 15 lbs?
My Math may be make believe
Maybe I’ll make 30 lbs. oh no!

300 cc per blower stroke
220 cc per engine stroke
300/220 = 1.36
Atmospheric pressure is 14.7 psi
14.7 * 1.36 =

20 psi absolute pressure
20 - 14.7 = 5.3 psi above atmospheric pressure.

5.3 lbs boost?
15 lbs boost?

A 500cc blower on a 440cc engine (with my math) would make 18.7 lbs of boost with 1:1 pulley ratio. Since it’s not perfect, 15 lbs seems reasonable for the 500cc blower.

I might need an eraser?

 

[bob58o]

Here’s a little free tip add 1.0 ounces of marvel mystery oil to a gallon of e85. It is a dry fuel and will help the blower live longer and save a little corrosion from the carb.

If it’s going to blow up, maybe I should use the 250 jet and some 30% Nitromethane RC fuel. Lol

 

[bob58o]

Hmmm. I calculated about 11 psi without including inefficiencies.

This seems to agree with my calc.

https://www.performancetrends.com/Calculators/Supercharger-Boost-Calculator/Supercharger-Boost-Calculator.php