Twilightoptics

iTrader: (1)

How come everyone seems to go towards the 390/465 CFM 4 bll holley's where there are 350/500cfm 2bbl Holleys that seem like they would make life a whole lot easier. Especially in a boosted application.

Just curious. Tried the search and all I read was some people "thinking" It'd get worse milage than the 4bbl.



And is a stock nikki really too small? 313CFM Stock and people putting 465 CFM carbs on stock motors saying it's better? Seems like a huge jump....

-Paul

wecycle

2 bbl carbs are rated at 3 in. hg pressure drop while 4 bbl carbs are rated at 1.5 in..
This means the 500 CFM rated carb will flow 354 CFM at the 1.5 in. hg. that the 4 bbl was tested at.
Might be worth a shot for simplicity, but you would probably need to create more of a plenum to smooth out the intake pulses so the Holley will work right.

Jeezus

iTrader: (4)

Because God made Weber's.

OneRotor

iTrader: (3)

And Delloratos (sp?)

Super82

iTrader: (1)

Why we make that big jump in CFM is purely because the Nikki is a bottleneck when you start making modifications. The motor with exhaust and other mods can flow 465cfm. On a stock motor what you are saying may be better but if you're going to upgrade your carb why not upgrade it bigger and put on headers for an even greater gain?

Sterling

Show me the math. Show me how the 70 cid rotary can move 465 cfm @ 8,400 RPM.

...Show me. I really, REALLY wanna see.

-I'll even give you 130% VE!!!

IanS

iTrader: (4)

lol, Sterling you're so crazy.

Sterling

Yeah, I know.

Hyper4mance2k

iTrader: (40)

I'm not sure your equation works for rotaries considering we move all 1.2 or 1.3L per revolution. Where as a 1.2 or 1.3l piston is only displacing half that per revolution. Plus the shape of the cumbustion chamber requires more air and fuel per displacement than a pissed on to create the same power.
But anyway, acording to your equation a 12A w/ 130% VE @8400 rpm needs 508.715277776 CFM LOL!!! Now at 100% VE it's 391 and your arguement stands. Remember as VE gets over 100% then demands for air and fuel increase rapidly.

PercentSevenC

His equation already takes that into account.

Though, actually, if you do use 130% as the VE, you get 509 CFM.

IanS

iTrader: (4)

Did you use 1.2 or 1.146? Could change the number a little bit... Just saying.

Sterling

Wrong.
You're adding 15%.
-Why? The 130% VE isn't enough for you?

Sterling

1146cc = 70 ci.

IanS

iTrader: (4)

Doh, displacement in cubic inches which makes the 1728 so important. My bad.

PercentSevenC

Well, if you meant it that way, you should have said 113% VE.

Sterling

Hmmm?
I said show me math where the 12a can huff 465 cfm, and I would even give a VE of 130%.
-Nevermind the equasion in my sig, which adds 15% just for ***** & giggles.
I'm talking about demonstrating how much the 12a can possibly breathe.

The 465 cfm carb works fine because the low end RPM still provides enough velocity to draw out & atomise the fuel well. But Carl & I spent ridiculous hours testing, cutting venturis, retesting, etc, etc, just so we could achieve that all so stupid "magical number" of 465 cfm just to make the Sterling more appealing to people.
The FACT of the matter is that at the Racing Beat recommended redline of 8400 RPM, at a VE of 100%, which just ain't happening in a stock port, the 12a can only really huff 340 cfm.
Go ahead and do it with 10,000 RPMs, and you STILL only get 405 cfm!

RXvedub

iTrader: (1)

that may be how you calculate the size of a 12A but if you have ever tried to feed one then you would know they will take much more and use it. what i mean by use it is make more power. a rotary has **** low end to begin with so why try to improve something it never had to begin with, so but a bigger carb, a free flowing exhaust and take advantage of the rotary with a bigger carb=TOP END POWER!!!

oh and that racingbeat testing is 20+ years old and it was with a restrictive exhaust.
ask them about boosting a 12A they will tell you its next to impossible, LOL

Starfox07

Close, because God made EFI

Super82

iTrader: (1)

Sterling, I take back what I said, I guess it can't flow that much. But what is your deal pushing this so hardcore? If going above the 340cfm is just a waste that will hurt your performance then why do you make your carb at 465? You say it yourself in your signature-'Choosing a carburetor that exceeds your engines maximum cfm requirements (340cfm) will only result in crappy low end performance.'

Your carb is 465, therefore your carb will give me crappy lowend perfomance and I should really mod my nikki at home for 340 . But we both know this wouldn't be as good. BTW I'm not trying to start another debate here, but you just seem a lil crazy about all this carb math lol.

At the question at hand despite the cfm ratings I think you'd just be best off going with a tried and true way of doing things in this case. Like I said, I'm quite sure we all acknowledge that the stock nikki is a bottleneck and upgrading to a higher flowing, better atomizing carb will help things. Nobody here has really complained about using a 465, whether it be a holley or a sterling, so it can't be a big issue. Plus secondaries are so much fun. But I'm sure someone else will have a different viewpoint on this....

Sterling

Well, this is the second time you've intentionally rubbed me the wrong way.

Most of my problem is what I call the "perpetuation of ignorance". People get stuck on things without doing the research themselves. People insist the Holley 600 is a fantastic choice for the 12a, or they refuse to acknowledge plain old inarguable physics that explains why a 4bbl carburetor that breathes as much at the top end as it's 2bbl counterpart is actually better for the rotary because the rotary notoriously suffers from lack of low end performance. Part of it is the constant battle with people who are stuck on nothing more than brand loyalty.


As for the "Ah-ha! Gotcha, ya ******' hypocrite!" with regards to my carb being over sized, I already explained (now twice in threads you've been a part of) just why we had to get the Sterling to flow that much; general ignorance. People just love numbers, even when they don't seem to understand their relevance. I can't even count how many times I've explained what I've gone through to raise the Sterling's cfm from it's initial 420 cfm to 465 without sacrificing low flow velocity. You've been a smart-*** to me before, but I'm gonna tell you something straight out right now; You have no idea wtf I've done with the Nikki. Reconfiguring the venturis wasn't the half of it. I pushed over the 465 limit by clipping OMP lines, booster venturi supports, reshaping the existing booster leg, thinning the primary throttle shaft instead of just cutting one edge off, -even using button head screws to mount the valves. It ends up being wayyyy too damned much work compared to the 420 cfm predesessor, but because people listen to "tried & true" ignorance, if the damned thing doesn't flow 465 like the Holley, ain't nobody gonna buy it. So as a result, I make far less money on my carbs. It's that simple.
So don't tell ME that my carb gives crappy low end. I worked my *** off to make damned sure it doesn't.

As for your whole "use something that's tried & true; -Use a Holley" shtick, it's pretty tiring. You're simply assuming that no one could modify a Nikki to be better than the Holley 465 just because you can't. But I did, and I put my money where my big mouth is- I give people 30 days to return the damned thing for a refund if they're not satisfied.
I feel plenty justified in being adamant about "the math" because I've paid my dues.

Jeezus

iTrader: (4)

Super82

iTrader: (1)

Man you didn't take any of my points. First, I'm not arguing with you, I never would. There is no point in arguing with you, it seems you have a .pdf file full of 'holley 465 rhetoric responses' and you just flip them out randomly. I was making a joke and agreeing with you. I mentioned that he should try something tried and true-like a sterling. I never said your carb has bad low end. Do you like to flip off on people like this because it makes your carb seem better? Because I never directly said anything bad about your carb in the 'first time I rubbed you the wrong way' and I surely mentioned NOTHING AT ALL WRONG WITH YOUR PRODUCT THIS TIME!!! I think you relate to arguing with people to get more sales, but I don't want another thread closed so I'll end it at that. I made my point to the OP in my previous posts.

justint5387

iTrader: (1)

You are the one that doubted his carb in the first place with the last thread. Can't expect the maker of a product to be nice and happy with you when you talk trash about a product that you never seen in person, let alone used it.... I.E. Doubting it actually flowed 465 cfm.

MattG

iTrader: (2)

My sterling kicks so much ***, chuck norris took notes from it!!

Kentetsu

Crappy low end performance on rotaries is a problem, no doubt. But I think that the Sterling carb addresses this issue quite nicely by ensuring that you still have high velocity airflow on the primaries.

Even in autocross racing, I probably spend at least 80% of my time on primaries alone, only dipping into the secondaries for brief periods on short straight sections. My win record will attest to the fact that I do not have crappy low end performance.