Pressure Source and Fuel Flow

[Joe-405]

I don't usually use the power jet. I cap off the circuit and try to make sure the main jet provides enough fuel alone.

Can you explain what you mean by you "gravity feed them where they are supposed to be at"?

Gravity feed the carb? Or gravity feed the power jet and source the fuel from somewhere else besides the bowl?

I only use the inlet for the fuel line in the regular spot. And gravity feed equals no fuel pump so tank above carburetors so it will flow as needed.

---------- Post added at 04:46 PM ---------- Previous post was at 04:44 PM ----------

I had a regular pump in my minibike and it pushed past the needle. If you were sitting still it would leak out the overflow hose.

The pump was the standard one used on race karts. The round plastic black Honda ones.

 

[bob58o]

When Bob has a problem he whips-it.

https://m.youtube.com/watch?v=j_QLzthSkfM

I have no idea why this song makes me smile. LOL
No one gets away!!! Unless they whippit.

---------- Post added at 12:39 AM ---------- Previous post was at 12:35 AM ----------

I only use the inlet for the fuel line in the regular spot. And gravity feed equals no fuel pump so tank above carburetors so it will flow as needed.

---------- Post added at 04:46 PM ---------- Previous post was at 04:44 PM ----------

I had a regular pump in my minibike and it pushed past the needle. If you were sitting still it would leak out the overflow hose.

The pump was the standard one used on race karts. The round plastic black Honda ones.

My plan is to gravity fed the carb bowl. But to use a separate tank with pump and solenoid to only feed the power jet.

When the solenoid is closed, fuel from the primary tank gravity feeds the carb bowl. When the solenoid is open, the bowl still gets gravity fed from the primary tank - but in addition to that I'll have a pump feeding fuel from the aux tank through the solenoid directly to the power jet (bypassing the bowl). So main jet fed from bowl, which is gravity fed from primary tank. And power jet is pump fed from aux tank (only when solenoid is open).

 

[bob58o]

Aux Fuel Tank with “Fill Gauge”, petcock, and vented cap.
This is a special cap. Made from parts I had laying around.

 

[bob58o]

It appears I forgot the fuel jet.
That seemed like quite a bit of fuel, and realized the jet I need is installed in a different carb.
Test did not show me what I wanted, but at least I know the pump and tank are functional.

https://www.youtube.com/watch?v=dv6WE7-1Q-0&feature=youtu.be

 

[ezcome-ezgo]

That was spectacular.

 

[bob58o]

This is with the 0.014” Jet installed.
https://youtu.be/h5N7Ggr9mMg

 

[ezcome-ezgo]

I'm worried about you Bob.

 

[65ShelbyClone]

That's a wet system alright...soaking wet.

When the velocity of the air in the horn increases enough, the pressure in the horn gets lowered to the point where the atmospheric pressure in the bowl (which is vented) can overcome the "head height" and push the fuel up the hose to the jet.

At least this is how I understand that it works. Same concept as the main jet and venturi inside the carb.

I have a Lectron carb of similar design. What I think happens is the power jet comes online when the slide opens to a point that enough air can flow by the siphon tube to cause fuel flow.

Also, I wouldn't spend the money on CO2 fire extinguishers just for the cylinder; paintball CO2 tanks are vastly cheaper. The 1800psi working pressure also means that they can hold Nitrous oxide, but they won't have an internal dip tube for picking up liquid N2O.

Aparently some guys in the tuner scene, try running jet fuel or avgas in the engine, as a additional boost.
Usually have a pressurized system not unlike a NO2 systems...

They might be more myth than actually done, but crazy guys with money to burn think of interesting ways to do stuff.

Yeah, that's mostly urban legend. Proper "jet fuel" is analogous to kerosene or diesel and doesn't cause anything but problems for a gas engine. Aviation gasoline (usually 100LL) is not a myth. Hotrodders have and sometimes still do use it in place of race gas, but there are better options. "Rocket fuel," which you didn't mention, is typically a colloquial reference to the likes of nitromethane, propylene oxide, and other nasty fuels that have origins in aerospace and rocket programs.

 

[bob58o]

That's a wet system alright...soaking wet.

From what I can find online this pressure and jet size seem about right for the fuel delivery with about a 10HP N2O shot.

When I get a chance I'll measure flow volume rate. I think I'm looking for 16oz in about 10-12 minutes. 41 seconds per oz.

http://www.nitrous.info/nitrous-fuel-jetting.htm

What doesn't seem to make sense is that I've been assuming 700 psi in the charger and the smallest jet they have is 0.4mm and that is for 99cc and under engines. 700 psi and 0.4mm jet gives 8-11 HP on most sites I can find. 8 - 11 HP seems like a bunch for a 79 or 99cc engine.

 

[itsid]

well. N2O is not a combustible gas itself, it's a reaction enhancer..
(better oxygen source than air)

So with only the amount of N2O you cannot calculate any hp enhancement
without knowing the engine and amount of fuel..

enhancement will be a percental value not an absolute one!

(at best based on a 100 hp engine, but judging by the rest of that website.. likely based on a 150 hp eninge )

Anyways, he's referring to either a 1100 GSX-R (likely 1995 model)
or a GSX-R 750W SRAD (likely 1997 model)
sooo we talk 147 or 135 horses as the base unrestricted engine (depends on exact jetting and setup so numbers can vary slightly)

let's call it 140 horses for brevity...
8hp enhancement is ~6%, 11hp ~8%
soo 6-8% enhancement for the assumed 140hp base engine

since amount of burned fuel (it's octane rating) is more important than engine's nominated power,
that was dumbed down..
but it is fair to assume that a 750cc four cylinder race bike,
processes more fuel than a 99cc industrial engine per stroke, not?

'sid

 

[65ShelbyClone]

From what I can find online this pressure and jet size seem about right for the fuel delivery with about a 10HP N2O shot.

When I get a chance I'll measure flow volume rate. I think I'm looking for 16oz in about 10-12 minutes. 41 seconds per oz.

http://www.nitrous.info/nitrous-fuel-jetting.htm

What doesn't seem to make sense is that I've been assuming 700 psi in the charger and the smallest jet they have is 0.4mm and that is for 99cc and under engines. 700 psi and 0.4mm jet gives 8-11 HP on most sites I can find. 8 - 11 HP seems like a bunch for a 79 or 99cc engine.

The information out there pertaining to automotive nitrous systems assumes liquid nitrous oxide is flowing through the jet. Systems using the 8g(?) disposable cartridges seem to rely on it being gaseous since the cartridge capacity is so small in relation to the system volume.

 

[bob58o]

I was thinking more along the lines of....

Brake Specific Fuel Consumption = fuel mass flow rate / effective engine power

If BSFC is 0.45 lbs / hp / hr
and I want 10 HP.

0.45 lbs / (HP*hr) = flow rate / 10 HP
Flow Rate (for 10 HP)= 4.5 lbs per hour.

Gasoline weighs about 6.25 lbs per gallon.

Flow rate = 0.72 gallons per hour.
Flow rate = 92 fl oz per hour
Flow rate = 1.53 fl oz per minute
Flow rate = 0.0256 fl oz per second
Flow rate = 39 seconds per fl oz

HP based off fuel flow rate and BSFC. Not as a %, but as absolute HP.
Spray the amount of fuel you want, then add the amount of nitrous to make the AFR correct.
Or am I off with this????

I assume this is how the calculators and charts work. Nitrous pressure and jet size is used to calculate the amount of oxygen, which is used to find out how much fuel needs to be delivered to make the mixture right. Once you know how much gasoline needs to be added to keep the AFR ratio correct, you can use the amount of gas and BSFC to calculate the HP gain.
http://www.robietherobot.com/nitrousjetcalculator.htm

MOTORCYCLE WET NITROUS JETTING CHART

The following is intended as a safe baseline for fogger systems. There are two fuel jet columns listed below. One column for fuel jet size with the fuel pump that comes in the kits and the other column for hi-output pumps – like the Holley Blue with 5-7 psi flowing pressure. The nitrous jet chart is based on bottle pressure of 900-950 psi. Ignition timing should as a baseline be retarded to 1/5 to 2 degrees for every 50 h.p. worth of nitrous hp used. Ignition timing should be retarded from the best timing on motor only. (The point at which best MPH or Torque was achieved.)


NitrousJet:
FUEL JET w/ 5-7psi Pump:
HP Gain:

14 14 6hp
16 16 9hp
18 18 12hp
20 20 15hp
22 22 17hp
24 24 20hp
26 26 25hp
28 28 30hp
30 30 34hp
32 32 38hp
34 34 40hp
36 36 45hp
40 40 50hp
42 42 60hp

 

[bob58o]

I tried to test the flow rate.
It wasn't a very accurate test, but I just wanted to see if I was close (order of magnitude close).

I measured about 40mL per 40 seconds. 1 fl oz is 30 mL.
A second test was closer to 35mL in 40 seconds (which is about right for 10HP with BSFC of 0.5 lbs of gas per hp per hour.

I might need to add another hole to vent while I fill.
1/8 male to 1/4 female npt Adapter. Funnel has o-ring and 1/4 npt male thread.


C8H18 + 12.5 O2 = 8CO2 + 9H20
If I need 12.5 O2's for every octane, I guess that means I need 25 O's for every octane. N2O has a single O. So 25 N2O's for every octane???? I'm not a fan of chemistry.

 

[ezcome-ezgo]

You may hate chemistry, but you have fallen into it's rabbit hole.

 

[bob58o]

9 days ago, my fuel solenoid was processed through the ISC Chicago Facility.
Two days ago, it was in Elk Grove Village (former location of my former employer - Oxford Instruments Measurement Systems).

I'm guessing by now it is on its way to California.

ISC Chicago is the worst. Send my stuff from China to San Francisco (less of language barrier? LOL) or somewhere in else in California to go through customs. Ugghhh.

 

[Randy H]

Probably just Homeland Security.
If you disappear I'll personally contact Bruce Rauner, unless you think he might be behind this. Dang man I'm sorry this is happening to you.

 

[bob58o]

Well this is what happens when you say "Bomb" on my thread while I'm googling oxidation reaction equations, nitromethane, and nitrous oxide.

Well that would be a bomb.

https://www.youtube.com/watch?v=DcK5gSRti4g

 

[Randy H]

Heck, what's done is done. Who isn't on somebody's watch list?

I'm not gonna provide any more key words though. Lol(kinda).

 

[bob58o]

Instructions: Spray dry nitrous into air filter using fitting provided.

Normal Person: Ok I’ll just fatten up the main jet a bit and run a little rich when off the bottle.

Bob: Well there is KISS, then there is what I do.

 

[bob58o]

This shows how the power jet kinda works at high RPMs on a two-stroke.
At about 1min:30sec.....
https://www.youtube.com/watch?v=-2qoI0mBBKE