(INTAKE) Can a Nikki carb be tuned to meet the holly and weber.
(INTAKE) Can a Nikki carb be tuned to meet the holly and weber.
03-18-06, 03:57 AM
#3
http://www.pbandjracing.com/
The Nikki-mod Gods...
Stu Aull
80GS
Alaska
The Nikki-mod Gods...
Stu Aull
80GS
Alaska
Originally Posted by Nicholas P.
Can you match the HP to the weber and the holly by tuning it?
03-18-06, 04:28 AM
#4
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from what i've read its entirely possible, however maybe some people on the site just want to make some $$$ 
i'd rather stick with a nikki if i still had a 12a, holleys can be a friggin' pain in the ****..
i'd rather stick with a nikki if i still had a 12a, holleys can be a friggin' pain in the ****..
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03-18-06, 11:43 AM
#11
Yep. Tuned from his shop for street use, but also it is engineered with the ease of being able to change jets within minutes on the track.
It is honestly the best bolt on available for us aside from a header.
Hell combine the two and you don't have to do **** until you decided to turbo or port.
It is honestly the best bolt on available for us aside from a header.
Hell combine the two and you don't have to do **** until you decided to turbo or port.
03-19-06, 07:48 AM
#16
Lorem ipsum dolor sit ame
Originally Posted by Paradox
hey man, i was siding with you 
to see the subject come up over and over and over and over and over and over and over and over and over.
03-20-06, 12:23 PM
#21
Nikki-Modder Rex-Rodder
Join Date: Feb 2001
Location: Trying to convince some clown not to put a Holley 600 on his 12a.
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Tranquil is correct.
I suggest that a Sterling Nikki can be tuned to out perform a Weber or Dellorto, or just about anything else, but I don't have enough compiled data.
I base it on physics for now; -A theory to be tested.
The carb flows 465 cfm. As Tranquil stated, that's the "yippee-skippy, my speedo goes to 200 MPH!!!" number. In other words, the number that sells the carb to people that like bigger numbers, but don't realize that bigger numbers don't always mean everything!
If you do the math for a 13B 80 cid engine, multiplied by 10,000 RPMs, at 100%Volumetric Efficiency, you find that it can't possibly eat more than 463 cfm!
Now there are plenty of other factors involved, including pulsing harmonics, how well the air flows in due to exhaust gas expansion back pressure, the flowability of the manifold and the intake port...But these all detract from the VE number.
There are rare, and very specific situations where the intake pulse rate, engine RPM, exhaust pulse rate, temperature, and perfect alignment of the planets can cause such a perfect harmony in an NA engine that the VE actually exceeds 100%, but it's only for a brief second, and considered a rare anomaly.
But flow alone doesn't make the carburetor. Not at all.
In fact, a carb too small for the rotary will often out perform a carb that's too big on the street, because the big carb only has a very narrow RPM band, way up high, when the velocity is actually fast enough to create a strong, and therefore tunable, signal to the main circuit where the fuel delivery can be properly metered and atomized.
I love the Nikki, and here's why;
VELOCITY is key. It's the single most important part of having a tunable carburetor.
The Holley carbs have 4 venturis that are the same diameter. That's V8 stuff!
The rotary engine has such a terrifically wider RPM range, that it really needs two carbs; a tiny one that will provide high intake velocity for the lower part of the band, and a much bigger one for the higher end of the band for when the little high velocity carb gets maxed out.
A 4 bbl carb does exactly that. The smaller the primary carb is, the lower in the engine RPMs that high velocity air flow will effect the carb. That's good, because you want that strong signal to the main fuel circuit to pull up fuel into the air. But too small, and it will max out the air it can flow too soon. Then the secondary carb has to come on.
...Well, that's not really too much of a problem. Even uncut Nikki primary venturis will suffice as far as air flow for a performance primary carb's duties. But then the secondaries would have to be cut more than we do.
The Nikki secondaries don't have enough material to remove that much without starting to disrupt the critical inlet & outlet angles that are so crucial to making a venturi have such high velocity at it's apex, so we have no choice but to do most of the removal to the primaries. Still, when they are done they flow far less overall than the Holley primaries, which translates into higher velocity by comparison. MUCH higher. This combined with the fact that Holley venturi geometry leaves much to be desired has me scratching my head at Holley, saying "WTF?"
The fuel signal primary half of a Holley, just like any Weber or other 2 bbl, could be air jet regulated a bit on the delicate side so that it has a high signal low in the RPMs, at relatively low velocity. But at low air velocity the fuel won't atomize very well and will be more like it's dribbling in, compared to the good atomization that comes from high velocity. Also, by the time the primary circuit is maxed out in it's air flow, the velocity is sucking too hard on the fuel circuit for that calibration, and you'll have to limit the fuel by the primary jets. This can cause a flat spot that pops up on you seemingly at random, when in fact it's occurring when you're under load. (The flat spot should ordinarily be hard to notice except that it will come on directly after a point where the air velocity is very high, and the fuel mixture is just perfect for that tiny window of the RPM band. -That happens in all carbs and is what you're always working to tune out by finding the perfect circuit transition...whole 'nother chapter...)
All this can be applied to the secondary portion of any carb, too, though there is almost always enough air flow velocity by the time the secondaries kick in, mechanical or vacuum, that the fuel is from that fuel circuit gets well atomized.
So to find the best carb set up for a rotary, do this;
Calculate the maximum flow of your engine.
Choose an appropriate carb based on this number.
You want one that will give the maximum air flow velocity possible...the smallest venturis you can get that will deliver your air, but at the same time you don't want one you're going to max out at your high RPM.
Then divide that number up between two carbs, -One big, and one little.
Combine them into a single two stage 4 bbl.
Make the two circuits completely tunable so that you can control maximum fuel they get, bleed off the signal to the main circuit with air bleeds, and control when the second one begins to work.
Now add an accelerator pump that will squirt fuel not only to get you going from an idling dead stop, but will also squirt fuel as the second carb is opening. ...And make that tunable.
Now you have a Sterling Nikki.
Nevermind what it looks like, and nevermind what brand name it sports.
Just undertand that it was engineered by Nikki, and modded by me & Carl based on physics.
-And make no mistake about it, this is NOT a "bolt-on & go" performance part.
Those folks who have done so and have had good results either have been extremelt lucky, or most likely, are not running their Sterlings @ full performance potential.
Everyone's application is different due to environment, altitude, and driving style.
It really does need to be regarded as a fully tunable carb in a "driver's application customisable" way.
I suggest that a Sterling Nikki can be tuned to out perform a Weber or Dellorto, or just about anything else, but I don't have enough compiled data.
I base it on physics for now; -A theory to be tested.
The carb flows 465 cfm. As Tranquil stated, that's the "yippee-skippy, my speedo goes to 200 MPH!!!" number. In other words, the number that sells the carb to people that like bigger numbers, but don't realize that bigger numbers don't always mean everything!
If you do the math for a 13B 80 cid engine, multiplied by 10,000 RPMs, at 100%Volumetric Efficiency, you find that it can't possibly eat more than 463 cfm!
Now there are plenty of other factors involved, including pulsing harmonics, how well the air flows in due to exhaust gas expansion back pressure, the flowability of the manifold and the intake port...But these all detract from the VE number.
There are rare, and very specific situations where the intake pulse rate, engine RPM, exhaust pulse rate, temperature, and perfect alignment of the planets can cause such a perfect harmony in an NA engine that the VE actually exceeds 100%, but it's only for a brief second, and considered a rare anomaly.
But flow alone doesn't make the carburetor. Not at all.
In fact, a carb too small for the rotary will often out perform a carb that's too big on the street, because the big carb only has a very narrow RPM band, way up high, when the velocity is actually fast enough to create a strong, and therefore tunable, signal to the main circuit where the fuel delivery can be properly metered and atomized.
I love the Nikki, and here's why;
VELOCITY is key. It's the single most important part of having a tunable carburetor.
The Holley carbs have 4 venturis that are the same diameter. That's V8 stuff!
The rotary engine has such a terrifically wider RPM range, that it really needs two carbs; a tiny one that will provide high intake velocity for the lower part of the band, and a much bigger one for the higher end of the band for when the little high velocity carb gets maxed out.
A 4 bbl carb does exactly that. The smaller the primary carb is, the lower in the engine RPMs that high velocity air flow will effect the carb. That's good, because you want that strong signal to the main fuel circuit to pull up fuel into the air. But too small, and it will max out the air it can flow too soon. Then the secondary carb has to come on.
...Well, that's not really too much of a problem. Even uncut Nikki primary venturis will suffice as far as air flow for a performance primary carb's duties. But then the secondaries would have to be cut more than we do.
The Nikki secondaries don't have enough material to remove that much without starting to disrupt the critical inlet & outlet angles that are so crucial to making a venturi have such high velocity at it's apex, so we have no choice but to do most of the removal to the primaries. Still, when they are done they flow far less overall than the Holley primaries, which translates into higher velocity by comparison. MUCH higher. This combined with the fact that Holley venturi geometry leaves much to be desired has me scratching my head at Holley, saying "WTF?"
The fuel signal primary half of a Holley, just like any Weber or other 2 bbl, could be air jet regulated a bit on the delicate side so that it has a high signal low in the RPMs, at relatively low velocity. But at low air velocity the fuel won't atomize very well and will be more like it's dribbling in, compared to the good atomization that comes from high velocity. Also, by the time the primary circuit is maxed out in it's air flow, the velocity is sucking too hard on the fuel circuit for that calibration, and you'll have to limit the fuel by the primary jets. This can cause a flat spot that pops up on you seemingly at random, when in fact it's occurring when you're under load. (The flat spot should ordinarily be hard to notice except that it will come on directly after a point where the air velocity is very high, and the fuel mixture is just perfect for that tiny window of the RPM band. -That happens in all carbs and is what you're always working to tune out by finding the perfect circuit transition...whole 'nother chapter...)
All this can be applied to the secondary portion of any carb, too, though there is almost always enough air flow velocity by the time the secondaries kick in, mechanical or vacuum, that the fuel is from that fuel circuit gets well atomized.
So to find the best carb set up for a rotary, do this;
Calculate the maximum flow of your engine.
Choose an appropriate carb based on this number.
You want one that will give the maximum air flow velocity possible...the smallest venturis you can get that will deliver your air, but at the same time you don't want one you're going to max out at your high RPM.
Then divide that number up between two carbs, -One big, and one little.
Combine them into a single two stage 4 bbl.
Make the two circuits completely tunable so that you can control maximum fuel they get, bleed off the signal to the main circuit with air bleeds, and control when the second one begins to work.
Now add an accelerator pump that will squirt fuel not only to get you going from an idling dead stop, but will also squirt fuel as the second carb is opening. ...And make that tunable.
Now you have a Sterling Nikki.
Nevermind what it looks like, and nevermind what brand name it sports.
Just undertand that it was engineered by Nikki, and modded by me & Carl based on physics.
-And make no mistake about it, this is NOT a "bolt-on & go" performance part.
Those folks who have done so and have had good results either have been extremelt lucky, or most likely, are not running their Sterlings @ full performance potential.
Everyone's application is different due to environment, altitude, and driving style.
It really does need to be regarded as a fully tunable carb in a "driver's application customisable" way.
03-26-06, 02:36 PM
#22
I've been asked to add this information in the sake of "fairness" to other carburetors, by Robert (680RWHP12A)
Originally Posted by 680RWHP12A
a weber//oer carb from its birth is a very easily tuneable hi-performance// race oriented carb.. there are several books out on weber carbs and weber tuning that are easy to get...
on a weber, , jet canges are as simple as removing a wing nut on top of the carb(there you have access to the main fuel and air jets and idle jets), there are over 12 different emulsion tubes available for fine tuning the carbs powerband to your specific engines demands.. remove 2 set screws and within minutes you can quickly swap out venturies, essentially changing the cfm's your carb will flow (more or less cfm's) and again changing the powerband of your engine... accelerator pump circut needs adjusting? its made easy with a weber, simply change the pump squirters and go! it goes on and on....
nikki carb facts
with a nikki carb,you cant change the emulsion tubes, the air jets are hard to get to, fuel jets are hard to get to,idle jets, want to change the venturies yourself? forget it, thier pressed into the nikki.
ill just keep sending this until you add it to the very one sided archive..ill let ryan know about it too.. thanks
on a weber, , jet canges are as simple as removing a wing nut on top of the carb(there you have access to the main fuel and air jets and idle jets), there are over 12 different emulsion tubes available for fine tuning the carbs powerband to your specific engines demands.. remove 2 set screws and within minutes you can quickly swap out venturies, essentially changing the cfm's your carb will flow (more or less cfm's) and again changing the powerband of your engine... accelerator pump circut needs adjusting? its made easy with a weber, simply change the pump squirters and go! it goes on and on....
nikki carb facts
with a nikki carb,you cant change the emulsion tubes, the air jets are hard to get to, fuel jets are hard to get to,idle jets, want to change the venturies yourself? forget it, thier pressed into the nikki.
ill just keep sending this until you add it to the very one sided archive..ill let ryan know about it too.. thanks
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