What would be the best carb set-ups for a DCOE type on a 13B large street ported engine?

 

let me rephrase this..I know nothing about the basics of carbs or intakes for a rotary...or nothing about carbs at all. I learned my car stuff on Hondas. Whats the best carb for a 13B street port? Could be a 4-port or a 6-port.

 

i would say a weber 48.

you can go IDA(down draft) or DOCE(i think thats it.. its Side draft)

OR!

If you can tune carbs and have ***** go for dual makuni 40's..

 

Like me

 

Actually for a street port, I believe your supposed to use a weber 51, not a 48. You can check with robert at rotary shack though, he'll know the right size.

 

Can anyone say whether the IDA or D.C.O.E is better?I'm curious as to which makes more power,seeing that they are the same size.I think?

 

The IDA makes more power, but the DCOE is supposedly more streetable.

 

I have both a 51 IDA Weber (downdraft) and 48 DHLA Dellorto (sidedraft) on similarly-built motors and the sidedraft is a good bit more streetable. The downdraft doesn't have enough room for a filter, either, on my setup. Finally, though, the sidedraft is just a little more elegant and sexy, I think.

 

In general, the sidedraught will have longer intake runners, because we tend to mount them over the engine. Should you use a sidedraught on ver short intake runners, next to the engine (provided the space is there), a lot of the streetability would be lost.
The reason is that longer runners will give more torque, and shorter ones mor power, but only in the top range rpm's. Of course this is just a very rough description, but you could say longer runners mean more usable powerband, shorter runners give a peak powerband.
I'd stick with a sidedraught for street use. Allthough I'm really swearing at the carb right now: the car won't start, probable to cold

 

I think there's a Mikuni what I believe is a 40 could be a 44. I don't know how to tell. But I know it's a mikuni and it's on a sidedraft style manifold. Is this good? Oh and my car is hardly streetable by the way lol. It doesn't like to go one speed. And it hates going slow. Could this be a bridge? Or just a large street port?

 

Do you have any pictures. Could be the tuning of the carb which could give those types of symptoms and also the low gas mileage that I think you mentioned in another thread.

On the Mikuni, the size is on the side of one of the barrels just above the main body but before the velocity stack. It'll be in light black lettering. Mine was barely readable but I could see that it said 40PHH within the number. You could also use a milimeter scale and measure across the throat of one of the barrels. I used a micrometer and got 45mm at the top for my 40PHH which seems off because I would think it should be 40mm. Could have measured wrong or my micrometer could be off too, it was cheap

 

I drove a dellorto 48dhla on the short intake runner lake cities manifold. positioning carb next to motor. with 37mm chokes in the carb it made a hair less torque and noticeably more horsepower and revved tons better than RB intake with 39mm chokes.

 

I agree with Drivefast7. The SU sidedraughts are mounted next to the engine and the runners are also very short. It is definitely not lacking for low end.

 

www.cardomain.com/id/mazdagslse Thats the only place where I can load pics. It needs a new fuel filter or fuel pump. Car just keeps dying while I'm driving, like when I put in neutral it just dies. I think it's the fuel filter or pump. Could be the carb, but most likely the pump or filter. I'm really new to tuning rx7s and fixing them. I can work on a honda, but not a rx7. It's also hard to start. And it doesn't like to idle just dies. Anyone have any conclusions?

 

I'm a Holley man my self. Your idle just ain't set right. Fuel filter replace takes like 10 minutes (including wash up of gas running into your arm pit).

 

It was the worst tonight, it kept dying right when I went to go after starting it. I just finally dfid 2 donuts in my works parking lot. I think I got fired. Anyways it just pissed me off, sometimes it idloes good though, how could it be my idle.

 

when was the last time your Mikuni was rebuilt?

has the car been tuned up lately?

vacuum leak?

Ever pour a bottle of Gumout Carburetor and Fuel Injection cleaner in the gas tank? I like to do that every month or so. Keeps the fuel system and motor clean.

 

I haven't done it in a long time. And the carb from what I know hasn't been rebuilt. I wish I knew where to buy rebuild kits for a mikuni.

 

eBay is your friend. There is a dealer there that sells rebuild kits for the 40 and 44 PHH's. He sells them by the pair since most instances saw the Mikuni's installed as pairs. Just do a search for "Mikuni PHH" and it'll turn up. $45 for the pair plus shipping.

 

ok this is what I did, I messed with the jets and turned up the idle screw so it revs alittle higher, it just sits about 1200 now is this ok?

 

I have my idle on my weber at about 900, and its pretty steady there. You still got some tuning to do if the lowest you can get 1200.

BTW are you having idle problems during warmup or all the time. Mine doesnt idle for the first ten minutes when I start it in the morning. Thats normal for a carb without a choke.

 

yea thats it it does that. It doesn't idle for like the first ten minutes and then after me holding the accelerator at like 1200 or so it idles ok. But t never did that before.

 

read about the mikuni carb here:
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2465590090

and here
http://cgi.ebay.com/ebaymotors/ws/eB...ayphotohosting

buy the rebuild kit here:
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2467201110
***** BONUS!!! NOW A DEAL YOU CAN'T REFUSE - USE BUY-IT-NOW AND GET A COPY OF THE MIKUNI TUNING AND MAINTENANCE MANUAL AT NO ADDITIONAL CHARGE!! DO THAT REBUILD RIGHT!!! *****