Crispin38

iTrader: (3)

Is anyone running they're secondary linkage so that all 4 barrels open at the same time? If so, tell how.
Pictures appreciated.

-Crispin

Kentetsu

You would not want to do that. It would result in low airflow velocity and run like crap...




.

stofficer1226

yup ask me how.... I was doing the typical nikki mod but did it incorrectly since it was my first time ever touching a carb on an engine that was bigger than 90cc. I accidently and incorrectly modded it so they open at the same time. It ran like crap. It's not one of those where it ran bad but resulted in a ton more power. It ran terrible.

Crispin38

iTrader: (3)

I will let you know of the results.

Crispin38

iTrader: (3)

Just figured it all out today and I already love it.
Almost comparable to a weber but has much much better throttle response.
There's really no comparison to progressive actuation. Just like mechanical secondaries, it takes skill to master your timing. This setup is even more critical, which is why some might call it a failure.
It takes time to master the tuning and driving style.

You're losing vacuum and velocity when you're matting the gas at a low rpm when the engine can't handle all the fuel/air.
The carburetor is still the same size/cfm. It will run the same at WOT. Again, the catch is learning how to lay in it at the right rate. If your banging through the gears(taking it to 8K RPM) you can keep it matted if your jetting is correct. So that isn't a question.

Glazedham42

iTrader: (4)

So you're bogging down the engine at low rpm for what purpose? My progressive Nikki will still flow just as much as yours at WOT, but be much more driveable at low rpm, and get better fuel economy.

What are you gaining other than making the car difficult to drive, and lowering your fuel economy?

Crispin38

iTrader: (3)

You're not actually bogging your engine down at low rpm unless you mash it down when it won't take the fuel/air!
The engine is much more response at low RPM actually, but like i said you have to gradually apply throttle till about 4500 RPM, it feels like you're using twice the amount of throttle you were before to achieve the same rate of accel, and really, you are compared to the progressive linkage because all four barrels are gradually opening. Versus the primaries being opened slowly till 4500 RPM, then mashing on it to open up the secondaries which are just an on/off switch anyways... You also have the ability to change you rate of throttle applied in each gear.. Because it is different in each gear your in,
I would imagine my results are much different because of my style of porting.. I'm not sure how this would work on stock port engine. It should be great, because you're basically giving the nikki the driving charateristics of a big 2-Barrel. Like a weber, which you also have to drive with the same philosophy.

Define driveable? Easy to drive?
1:1 linkage doesn't necessarily make it hard to drive(i think it' more fun), but it sure as hell is was more response, i honestly feel like i've added about 30HP from 3-4.5K RPM when i'm only at part throttle, my rate of accel has definetly improved.. I was interested in this mod because i knew it would make autocrossing so much easier. I have much much much more control in how much air/fuel i'm feeding the engine, at least i feel that way. I really enjoy it. If it does result in bogging down at low rpm, or a loss in air velocity at low rpm then hell i like it! Cause it runs goouuiidd.

j9fd3s

iTrader: (3)

in principal i agree with you, MY weber car is jetted right, and i can floor it anytime and it goes with no bog/hesitation.

however on your nikki, the time you spend "laying in the throttle right" is the time a vacuum secondary nikki with a different spring in it is faster than you.

Crispin38

iTrader: (3)

Your weber is also feeding an engine that can handle more fuel/air.

I've tried 3 different linkage setups, I think this one is most efficient for my wants and application.
There's a lot of variables that all of us could never cover.

Kentetsu

I don't know man, it still sounds like you are crippling your carb.

Its like saying "hey, if I mutilate my legs like this, then I can still walk if I'm really carefull and I can still run top speed just like I used to!"

It just doesn't sound like a gain to me...

Crispin38

iTrader: (3)

Makes perfect sense to me. But to those who it doesn't, do me a favor, try it. Then tell me what you think.

Crispin38

iTrader: (3)

Makes perfect sense to me. But to those who it doesn't, do me a favor, try it. Then tell me what you think. It's obvious none on here have..

I got the idea from somewhere, from someone who had success with it.

DivinDriver

iTrader: (15)

Sorry, sir, but that's not how it works;

First, you get explain how it actually makes things better in a way that others can understand, then we decide whether or not it makes enough sense to try on our cars.

I don't do stuff to my car that 1) doesn't make good engineering/physics sense to me, and 2) the guy who's touting it can't explain.


That's sort of the definition of 'bogging,' isn't it? Giving it more throttle than it can handle at current rpm/load/gear, resulting in low torque?

If you have to carefully manage the throttle all the way up to 4500 RPM, the engine is less, not more, responsive - - it's not responding to the throttle commands you are issuing. Instead, you are responding to the engine's inability to handle the airflow you're commanding.

Maybe you can explain it better to the rest of us with a video of your driving it this way?

j9fd3s

iTrader: (3)

this is where a car with the vacuum secondaries is faster, cause driver can floor it and um drive, and not modulate the throttle.

the human brain is only like 1hz, so you can't really handle the driving part AND the trying to feed the engine more throttle but maybe not part.

ok you're like 18, maybe you're like 1.5hz, but still

LizardFC

iTrader: (1)

It sounds like you're interpreting the fact that it requires less throttle input at low RPM to mean that it is producing more torque, which would be false. You're opening all the plates to give it more air at low RPM, but you're also dumping more fuel in with it. Even with a lot of porting, the engine isn't quite that hungry at low RPM. The primaries are small for a reason. A wideband would show that you're running crazy rich up until high RPM. So I believe that all you are doing is wasting gas.

Not to say that you should be burned at the stake for trying. I think it's great that people are still experimenting with the Nikki. And I'm curious how your idea would do with a small turbo or supercharger.

Crispin38

iTrader: (3)

Then I guess I don't know what exactly I need to say to explain it.
I do have a wideband, although it does show a rich mixture, it's 11.3ish through the whole spectrum. Which is where I've felt I'm making the most power. I'm currently running 100's for primary jets, and 175's for secondaries. As stated, I'm seeing low elevens at WOT. I've also adjusted my AP so that it leans the mixture just enough when I start to open it up at low revs.
I wouldn't be running 1:1 linkage if I didn't think it was better, that would be stupid.

j9fd3s,
18 yes, let's just leave it at that,

LizardFC

iTrader: (1)

What kind of AFR's does it show when just putting around town? I'm still setting up my wideband so I don't have much to compare your numbers too.

DivinDriver

iTrader: (15)

Don't get us wrong; we're not throwing rocks at ya... j9fd3s' comment was that at 18 your reaction time is a lot faster than some of us older farts.

+100 for experimentation. Now you just have to quantify your results, otherwise it's not 'Science (tm) '!

Rotary engine theory says best power is made at 12:1 - 14:1, so you're at least moderately rich. You're also probably not atomizing your fuel very effectively, since having 4 bores working instead of 2 means that air velocity through any given bore is halved (or worse, since the secondaries are larger).

With a normally-aspirated engine (as opposed to boosted) total airflow is strictly a function of RPM and displacement; if you let the flow rate over the individual venturis drop too low, you end up with a loss of Bernoulli effect (like a wing stall in an airplane) which in part means fuel doesn't mix as well, since its not sucked out the feed or through the emulsion tubes with enough force to mix well.

t_g_farrell

iTrader: (1)

We need empirical evidence that this is improving performance.

If your wanting us to agree that its a good mod based on what your saying we can't/won't.

If you care, then get a dyno of your car with mech or vaccum secondaries vs.
this new improve full secodary mod. That will shut us up

j9fd3s

iTrader: (3)

its not like that, i'm jealous.

DivinDriver

iTrader: (15)

See, the whole point to multi-barrel carbs is to keep venturi air velocity high even at low air volumes, while allowing for free flow at high volumes.

Likewise the whole point to progressive-opening secondaries (vac or mech). It's an attempt simulate something that mechanically would be almost impossible to do directly or reliably, which is to vary the diameter of the venturi in response to throttle position.

If this weren't important, all cars could run perfectly on a large single-barrel carb with one massive butterfly.

Kentetsu

Its good to see somebody using their brain and trying new things, but the new thing that you are trying has been covered before.

You might want to do some reading over at Sterling's site, which is about the best resource for information on these carbs. He does a great job of explaining things in layman's terms, and there is a great explaination on venturi velocity too.

www.sterlingmetalworks.com