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Sprayed Mikuni's(Nitrous)


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I am gonna be running triple mikuni 40's on my L28 setup, and was looking at spraying. I have a few questions that maybe somebody could answer. I have a wet shot kit already, and was wondering howto hook it up. I don't really like the idea of drilling and tapping 6 holes into the intake and having to jet them all the same, and have a bunch of lines and such running everywhere. Its gonna be more of a hidden setup, and with one line, its easy to hide. 6 isn't so easy to hide. I know your supposed to run the spray after the carbs, but what would happen if I sprayed before the carbs? I have an airbox that I can spray into, would it work? Am I asking for trouble?

 

I will be running a fuel injection fuel pump on the application, with a regulator holding the correct fuel pressure for the carbs. I read on here that nitrous doesn't like fuel pressure below 7psi, but I'd be running around 3.5psi most of the time. What do I do about this?

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Running a single wet fogger into your airbox is an almost sure way of having a cyl run lean ,running lean on nitrous is never a good thing. The safest way is a direct port , as for the fuel system if you have a return style regulator and use a dead end style regulator for the carbs you can run one pressure for the nitrous and 3.5 for the carbs.

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Possible solution. I assume you have the carbs off the car right now? If so, (and assuming that they are the same design basically as the 44PHH model), you should see three threaded holes on the lower portion of each throat, all the same size [two at the six o'clock, one at the....call it 4:30 or 7:30 depending on which throat]. The non vertical holes hold the actual venturis in place, however, I don't THINK that the other two are actually used, and the one closest to the engine SHOULD work, assuming I'm reading the manual right....

 

I don't know spray very well, but it would put the injection b/w the venturis and the throttle valve, which it seems is what you are looking for?

 

As for fuel pressure, do you mean that the nitrous system should be at 7psi, or that it actually calls for the gas to be at 7? Seems to me that gas system pressure shouldn't matter at all.

 

Your sig says boost, I assume you mean a blow through setup? What kind? (I'm interested in that as well).

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The reason I wonder about the fuel system, is the fact that the pressure would always be changing from the regulator. I'm also not sure if the regulator is a return style either. Maybe Tony D can chime in on this.

 

The airbox isn't a normal airbox, its designed with baffles to feed boost to all cylinders fairly equally, and its also sealed. I'm just not sure if I'm gonna be spraying into the right place. Without giving too much away, the setup is a blow-through triple mikuni setup. If I was to spray into the piping right before the airbox(which would send it to all cylinders fairly equal) Mind you all this is under boost, going through the carbs too. Would I have alot of problems, or is it a recipe for disaster?

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I don't know spray very well, but it would put the injection b/w the venturis and the throttle valve, which it seems is what you are looking for?

 

As for fuel pressure, do you mean that the nitrous system should be at 7psi, or that it actually calls for the gas to be at 7? Seems to me that gas system pressure shouldn't matter at all.

 

Your sig says boost, I assume you mean a blow through setup? What kind? (I'm interested in that as well).

 

On a wet system, there is additional fuel being added with the nitrous, so the pressure of the fuel side is VERY important, to keep from running lean, and melting down.

 

The actual pressure seems to be a variable from different nitrous manifacturers, some say 7, some say 5 PSIG, some say that 5 PSIG still has a lot of safe margin, with thier tune-ups. Blanket statements of "needs to be 7 PSIG" will only hurt you in the end. There is a balance between amount of nitrous and fuel added, metered through different sized jets.

 

Direct port, especially with multiple carbs.

 

The only other way to do it is, by using 3 plates, though I'm sure there are no off the shelf plate systems for the Mikunis. ;)

 

The really nice thing about direct port is that each cylinder can be tuned, to compensate for a rich or lean cylinder, by adjusting either the nitrous or fuel jet of that particular cylinder.

 

Remember liquid does NOT flow the same as air, even when broken down like nitrous does when it comes out of the nozzle. Nitrous doesn't like to turn when sprayed, and I'm sure you'll find that most of the nitrous would sprayed into the rear cylinder(s), due to the actual flow characteristics of a pressurized chamber, even if it wasn't pressurized it would do the same, but maybe to a lesser extent.

 

Just because you want the nitrous to turn and flow into the first 2 carbs, doesn't mean that it will.

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The safest way to run wet nitrous is to have a seperate fuel pump, regulator and lines feeding the fuel solenoid. Using a return style regulator with the nitrous is good idea as it ensures that a lean condition is not created from fuel boiling out of the fuel line before the solenoid is activated.This is especially true with a non crossflow turbo motor.

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The only other way to do it is, by using 3 plates, though I'm sure there are no off the shelf plate systems for the Mikunis. ;)

Just because you want the nitrous to turn and flow into the first 2 carbs, doesn't mean that it will.

 

I might build a bolt-on fogger plate for the mikuni's here soon then.

 

Its not what I want it to do, its what I need it to do. What I'm thinking is the fact that with pressure, it should help to move the mixture though the carbs. The box has an internal baffle to ensure that it equals out.

 

The safest way to run wet nitrous is to have a seperate fuel pump, regulator and lines feeding the fuel solenoid. Using a return style regulator with the nitrous is good idea as it ensures that a lean condition is not created from fuel boiling out of the fuel line before the solenoid is activated.This is especially true with a non crossflow turbo motor.

 

If I had a return style regulator that ensured the correct pressure for the motor, but still running a constant fuel pressure for the spray, would this suffice for something like a 100hp increase?

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You would still end up having to use two regulators, a port on the return style regulator to a "dead end' regulator to the carbs (it all depends on how much of a fuel pressure increase to the carbs as boost pressure rises). Then run the nitrous fuel solenoid return style, you are still looking at needing higher fuel pressure for the nitrous than for the carbs. You are actually better off having more than 5-7 psi as it promotes better fuel atomization.

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Not sure exactly what pump I'm gonna use yet, but most fuel injection pumps run 40psi+, correct? More pressure would be better for the carbs?

 

No, too much pressure = breaking stuff inside carbs like gaskets or floats depending on what you're running. Happy zone: 2-5psi, atleast for Webers.

 

 

 

 

Maybe you do something like a fuel rail instead of having 6 lines, then run it underneath the mani rather than on top. This way its not so visible. And throw in a heat shield too. I don't know how that stuff works but it sounds like it would be a bright idea to keep it shielded from hot pipes.

 

OR maybe you do like this:

 

The injectors are spraying directly into the throttle body barrels. MAYBE you use the air box, but inside the air box is where you hide the pipes. Then you do the same concept as a fuel rail and you have a nozzle spraying into each carb barrel (1 for each cylinder). This way its hidden inside the airbox, and you don't just spray the whole shot into the airbox and it just goes into whichever cylinder, but you spray directly into the barrel.

 

 

Excuse my John Madden drawing:

91735477ym0.jpg

:icon44:

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