Hi Randy,

I am asking here ,now, since the last time I never really got an answer that I can remember.

Some time ago, I saw (Stunt News, maybe??) an article where the NVA position compared to the centerline of the tank was *proven* (not my word!) to not be of great consequence.    The engine tested was an inverted mount ST G51 with the stock venturi where the NVA sits above the crankcase throat.  The engine was trimmed in to a correct upright/inverted run and then the engine was altered to have the NVA mounted in a more traditional ST location, and finally a through the case NVA.  I am guessing, but it seems the NVA height location was altered about 1/4" at least, overall. 

The engine ran the same in all configurations.  Something was mentioned about a *center of crankcase pressure*, or something like that. (?? ?? )

What's up with that?  (in simple terms! LOL!!)

Thanks
Bill <><

HI Bill

I have never seen that in any of the Super Tigers I have ran, they all respond to moving the needle position, and when I had a stock located ST 51 in my Magnumm I had to move the tank down.. in the  ship almost a 1\4 of an inch.
However with that said, it is not where the "needle" is, its at what point does the fuel enter the atmosphere inside the venturie, Which explains why there is very little differance, if any when using an ST 60 or ST46 with the rearward located venturie, or using a drilled thru case and a restrictor.

None of what I said about the G-51 applies if your using it side mounted or on a profile

Randy

<<However with that said, it is not where the "needle" is, its at what point does the fuel enter the atmosphere inside the venturie>>

Isn't that the same point ??
 
I would think that its determined where the pressure drop occurrs, is that not always at the point of greatest restriction, ie the orifice created by the needle ??

Hi Allan

Nope it is not the same point, the Stock G51 has the fuel coming out at a much higher level than the older 51 or the 46 or 60, what i was talking about has nothing to do with the pressure drop or the restriction, you can put a venturie or restrictor that has  zero taper and it would still run differently.
I have seen  several people make  restrictors that were just that ,constant diameter  tubes with no taper at all. they still will have an effect on where you have to put the tank, if you move  the  NVA up or down in the restictors.
What Bill  was asking is basically this: if you had ,for example, a new G51 and put in 3 differant types of induction systems, the stock high mounted NVA, a typical drilled thru the middle of the case lower restrictor, or a true venturie with a rear mounted NVA would the tank stay in the same  place?
the answer is  NO.    maybe on a profile or sidemounted engine, but in a  inverted or right side up mount  the  tank will have to move.

Regards
Randy