comradegiant

Just kind of curious as to why side drafts on RX's always have a manifold that brings them up on top of the motor. I'm used to the Nissan Zs and British setups where the carb comes straight out the side of the motor. Any particular reason for the change on the rotary?

nevarmore

A somewhat educated guess: Piston engines with sidedraught carbs will naturally have the carb sitting higher up on the engine on the heads. With a 12a your carbs would be way down in the engine bay, wherethey'd be getting heated up. Its also harder to get cool clean air the closer to the center and bottom of the engine you get.

It may also have something to do with building intake velocity through the length and size of the intake runners. I'm not familiar enough with that area or how a rotary responds to different length intake runners.

alien_rx7

There were actually two or three companies that use to make sidedraft intakes that came right out to the side with no bends. I've got one from TWM with two Mikuni 40 PHH carbs on it. To see it go to http://www.milisake.com/gallery/view...-7GSL&id=carb3

hornbm

the wrap around style also allows for longer runners.

Terror7

I want that sooooo much.....

cosmicbang

The SU intakes also come straight out. You can get them from Hurley.
http://www.hurley-engineering.ltd.uk/mazda12a.aspx

1stgen_tn

I would say they are also on top of the engine so that they can suck COOL air rather than sucking hot air if they were to the side just above the headers.

For the guys running these sidedrafts, would a hood scoop help? You are not really pulling in any cold air on those type setups... Just curious about that. Maybe it doesn't matter either way??

alien_rx7

Nope, sorry. OT, not sure if it is the same, but I've been thinking about making a rotary powered sand dragster since we have a local strip that runs sand drags every weekend.

alien_rx7

I'm sure some ducting will help bring in some cooler air. I haven't installed mine yet but will definitely be running a heat shield underneath them over the header and some ducting either from in front of the radiator or a small scoop offset to that side of the hood.

web777

The longer manifold creates more torque which what rotaries need.

prefix

You'd actually be surprised on how cold those things stay. I have the RB header and intake manifold with a 45dcoe carb. I was thinking about putting a scoop in and touched the bottom of my intake manifold after running my car for a while and it was actually pretty cool. If anything is going to help at all you should make a heat shield to go between your intake and exhaust manifolds.

1stgen_tn

about how much more torque are we talking?

horsepower??

I know they made some mean power on the ole' datsuns my Dad used to run..... Well worth $500 for the setup if same scenario.

Not sure why anyone would spend $300 for a sterling when you can get a Weber (or similiar) for around $500 (no offense Carl)

Oh, and yeah, the heat shields make perfect since.....

Rx7carl

No offense taken.

Its a matter of application. The straight out "lake cities" style manifold with a weber are made for hi rpm use. With almost no runner length they will suck at low to midrange. Probably about as streetable as a PP engine. The wrap around side draft manifolds with their long runners drops the torque peak into a more useable area for the street. The short down draft manifolds would fall in between the other two.

For streetablilty its hard to beat the little 4bbl from Japan IMHO. It has none of the vices of the Holley or Webers, and can be made to perform extremely well. But I know that for some its an ugly duckling . Those guys like the of the other carbs, regardless of its performance, and lack therof in certain areas.

1stgen_tn

Well, I'm sure this has been asked before but how MORE power do you get out of the sterlings? It's like a 100CFM gain, right?

Still no answer on how much power gains on the webers/mikunis/RB's guys.......Does anyone know? Dyno chart??

1stgen_tn

Well, I'm sure this has been asked before but how MORE power do you get out of the sterlings? It's like a 100CFM gain, right?

Still no answer on how much power gains on the webers/mikunis/RB's guys.......Does anyone know? Dyno chart??

cosmicbang

That is not the case for SU's which also use short runners. They are very streetable, have good fuel economy, and are definitely not lacking for torque at low or mid range rpms.

The SU intake is not horizontally out, but angles up (to clear the steering on RHD cars). So the position of the air cleaner is higher up and it is not sucking air off the headers.

Rx7carl

Im not that familiar with SU's. At least Ive never worked with them that is. So I cannot speak intelligently about them sorry. I will defer to your experience. Tell us more about them. I hear they can be finicky, especially the oil leakage from the bellows, keeping them sync'd and other such small problems.

Rx7carl

No dyno sheets yet sorry. 152CFM gain over stock.

1stgen_tn

yes, do tell. I'm looking for the best "bang for the buck" upgrade for carburetation myself.

I don't want s/c or turbo that is for sure. Just a little extra power and torque, and yes, the look too.

so far, best deal I've seen is 500 bucks at Rotaryshack for the weber sytsem....

Sterling

Till someone actually dynos the Sterling Carb, I won't know concretely.
But I can at least confidently use Yaw's dyno sheet as a reference, because I know my carb is better than his.
The stock Nikki flows 313. Yaws flowed 429. Ours flows 452.
The Sterling Carb's venturis are the same diameter as Yaw's were, but they are more efficient, hence the better flow. The fact that there's more volume flowing through the same sized opening means more velocity even at low rpms compared to Yaw's, which means stronger signal to the main circuit which ensures power on tap down low.
We are working on manifold porting configurations.

When we have come up with the production-porting manifold prototype, we will dyno the Sterling Carb.

Because if you know anything about carburetion, you'd know that a four bbl carb that outflows the engine @ 100% VE by no more than 25-30% will allow for peak engine horsepower, but also for adequate main circuit signal low in the RPMs to ensure power down low- where every two bbl that outflows the engine suffers; and that the tuneability of the Sterling Carb is unmatched by any 2 bbl carb, or any Holley 4 bbl carb suited for the rotary - because we make it that way.
Plus I'll refund your money if you don't like it.

Narcisse91

I'll do a before and after dyno if you cut me a break on the cost of the upgrade

1stgen_tn

guilty! I don't know that much about carburation......

I just know the webers and mikunis are very desirable among the 70s and 80s cars. Best thing to happen to a Datsun 510 or 240z. Now, I know the rotaries are TOTALLY different so maybe the same princibles don't apply here.

So are you saying the sterlings are just as good, or better, than the other (2 bbls)??????

seanrot

iTrader: (2)

yeah i think thats what he said. better than anyother in the tuneability department.... I think he is kinda byass though. but im sure he is puting out a quality pruduct.

Anyone now the flow rate on a weber 48? just curious.

Ill give you credit on the tuneability but who do you give props to on all out gas swallowing power making ability??????

cosmicbang

In my experience I never had any problems at all with them. That may or may not be typical; perhaps I was just lucky. They are a simple design. Like any multiple carburettor, they need to be balanced when they are tuned, but they should not get out of synch on their own for no reason.

Rx7carl

Well I remember having the 4 1bbl setup on my Corvair years ago. The damn things would never stay in sync for more than a week. I know some Alfa and Volvo people who have told me that out of the box, SU's have the quirks I mentioned. A good rework fixes most of the problems, but they still use/seep oil from the bellows and need to be refilled occasionally. I got it on good advice that sewing machine oil or 3n1 oil is the best to use.