I have no paperwork on this carb on the top is stamped 48DCO2s/p. I assume its basically a DCOE?

I did search. No answer for 12a.

12a SCCA EP car street port
SDJ Exhaust header 3"-4" pipe.
Stock ignition (for now)

I think the current sizes of 160 main jets, 65 idle jet may be off. Anyone have any opinions.

 

e-mail robert at rotary shack...he's good

 

A DCO is a DCOE without a choke, otherwise known as the competition version of the DCOE

 

Thank's that helpful. I need to buy the Weber manual/tuning guide.

 

heres a web page I found a while back check it out. its aimed at 4 &6 boingers but it might help

http://www.teglerizer.com/dcoe/rasorcom.htm

ken

 

Thanks Ken, I found that site and a multitude of other sites but no one has a 12a recomendation starting point with a street port and wide open 100db exhaust. I posted that my main jet is 160, but I believe its actually 140. The car is in the shop and I don't have access to it. We can't get the back rotor to fire, and think that the carb needs to be rebuilt. I have the carb rebuild kit being shipped today and the jets could ride along. I should have just ordered it from Robert at Rotary shack, and let him choose what jets I should have on hand for tuning.

 

Bump, no one running a Weber DCO on a streetported 12a??

 

My first post

- I have been reading over all the threads about DCOE webers and it seems that noone is having much luck with them.

I have just bought myself a 48DCOE for my 12A Mild port.

Can anyone suggest a starting point. With some base settings it shouldn't be too hard to just trial and error a decent tune.

My carb was previously running on a 12A Bridgie. It has 220 mains, 165 airs, F11 tubes, 60-F9 idle and 42mm chokes.

For my near stock engine I am thinking of going for a 36 or 38mm choke and around 170-180 main jets.

Any input would be great!

Cheers,
Scott.

 

Well I have learned a lot since I first posted this question, but am still looking for answers.
I went to 210 air, 190 main, f2 tube, idle is 65-??. THe DCO s/p has no choke. The stuff I've read shows the air bleeder jet about 20 larger than the main jet???? I felt like I was running a little rich as my egt's were running 1450 or so. I went to 200 air, 180 main and had further complications due to a leakey intake gasket, so never got a good read on the egt's.

Scott any input you come up with in the coming weeks would be most helpful. There is a good calculator on this page http://www.teglerizer.com/dcoe/rasorcom.htm but it's set up for piston engines. I think your main jets are about right in the 180 range.

Good luck, Paul

 

That site is very helpfull! I used to run twin 40mm DCOEs in my Capella (616 to you guys I think). For piston cars, there are general equations to work out jetting. Eg: venturi x displacement + 60 = air bleed. I can not find anything like this about rotaries. I was able to get my twin DCOEs tuned near perfect just buy doing those equations and a bit of tweaking.

I am going to order a book from Racing Beat. I believe they go into some detail about jetting carbs for different applications.

If anyone else wants to share their jetting, I would really appreciate it.

One last thing : What type of air filters are you guys using? If you are using the K&N style filters, are you still using ram tubes underneath or are you just bolting the filter to the face of the carby?

Cheers,
Scott.

 

I just thought I would let you all know how I have been going with my jetting.

I started off with 60F8 idle jets, 180 main, 200 air, F11 tubes, 38mm chokes.

I could not get the car to actually move with those idle jets in there. As soon as I cracked the throttle it would stall. I then went to a 65F9 idle jet and have it about 80% right.

At the moment, I still have a bit of a flat spot in the off-idle progression circuit, but I think this may be accel pump related. If I ever so slowly open the throttle, it will rev without any stumbling. It is only quick stabs at the throttle (ie, taking off on a hill, heel+toe when changing gears) that causes the problems.

My main jets seem pretty good. Mid to top end power is significantly better than the Nikki. Of course, I am only using the old backside dyno, so I cannot be certain to exactly how much better it is.

I am yet to try different main jets as I am happy enough with the power increase I have already achieved.

I am hoping that my fuel economy will still be ok. With the 65F9 jets I have lean-best idle at exactly 1,1/4 turns off seated - so, about perfect according to all the books.

 

Scott, Thanks for the good info. I just saw that you posted.

As it turns out I ran a similar setup in my 1st and only race with this setup. F2 emulsion tube(et), 190 main with 210 air correctors, 65?? idle jet. The second race day I changed to a 180 main and 200 ac. I blew the back apex seal in qualifying due to a leaky intake gasket, could also have been due to lack of fuel?? I'll never know for sure. Rebuilding now and plan to dyno the setup with different mains, et's, ac & idle jets. I need to break it in on the dyno anyway.

Tom just posted this in the race section:
Quote:
"For a given air correction jet, a larger main jet will flow more fuel across the RPM range.

For a given main jet, a larger air correction jet will reduce fuel flow in the higher RPM range


That came from http://www.teglerizer.com/dcoe/webertune.htm"

My gut feel is that a 190-200 main for a streetport 12a and a smaller et will be about right. I will post all my dyno results with a/f & egt's in about a month.

Paul

 

I think thats right. You need to run a air corrector thats a bit smaller than your main jet to get the top end. Im still wondering what all the f numbers represent. I want to get a larger idle jet in my street ported 4 port 13b with a 48 dco 2sp but I dont know if it should be an f2 f5 f11 or what ever all those f #'s are. what the heck does that number stand for?

Brian

 

do you think someone could compile post of successful dcoe jetting and put it in the FAQ?

 

do you think someone could compile posts of successful dcoe jetting and put it in the FAQ?

 

yeah the faq would be an excellent place for this. or even just STICKY this query string

Any how. I have, I think sucessfully jetted my 48 dco. As I mentioned before... Its on a street ported 4 port 13b with a lake city rotaries intake and a racing beat header. The exhaust from there back is a home made colage of 2" and 2.5" and so on.

Im running

180 mains

220 air correction

65f9 idle jets

f15 emulsion tube

I have no idea what the pump jet size is but it works great! I can get plenty of scratch in the first 2 gears and some in third too depending on road surface with my cold kumho ecsta v700's. I detected bit of hesitation once or twice but that seemed the exception. I didnt get a chance to do any long runs with it as school is just getting out and there are kids walking home so bad idea at the moment. I'l try one tomorrow morning but I think I have it nailed.

Im so happy I could wizz my pants :-D

 

Use the FAQ as starting point. first work on your idle jets then the main jets/venturies. No rule book on the street

 

http://www.pugspares.co.uk/ManualsDisplay.asp?offset=10

there is a book that you can buy there that is for tunning the webbers and dellortos. you can probly find it online too fo free

 

Ok well I got around to doing a sustained acceleration run (through 3rd gear) and the car seems a little flat above 5,000. Its not bad at all... just falls off a tad bit. Like I said I have a 220 air corrector. I tried a 210 too but it ran like crap at high rpm's. I know that im supposed to get better power at the top end with a smaller air corrector but it ran in an acceptable manner only after going to this 220 air. I think that the f15 emulsion tube is pretty big too and that might have something to do with the carb using such a big air corrector. I have a f 7 emulsion tube too. is that a more resonable one to use?

Brian

 

i know on the racing beat page it has some weber guides and i think it says the 48 isnt recommended for anything less than a bridgeport,that might be a problem,when you click on the wber carb there will be a link,and two links on the bigger carb,which is only for peripheral ports

 

f is the flute size of the jet.

 

https://www.rx7club.com/showthread.p...highlight=dcoe

 

All the racers are running the 48's and larger in SCCA racing. On 12a streetported motors all the way to brigeported GT-3 cars. The carbs are totally adjustable by the jetting. Getting it right for each particular application is an art. Trial and error, using egt's and a/f numbers or just street tuning using the butt dyno.

The racing beat suff is linked in the mazspeed link. Still no direct help for the DCO or DCOE, this thread is an attempt to set good baseline jet settings for others to use as a starting point in the future. It did start out with me 3 days away from a race trying to figure out jetting with the car still apart.

Hyper4mance2k]https://www.rx7club.com/showthread.p...highlight=dcoe[/QUOTE]

Good link, with some good information. Also show's how hard all this is.

 

No, I've searched for hours. Weber makes a tuning manual, I'm going to have to bite the bullet and buy it. The web sites listed in this thread are the best I could come up with.

 

watching this thread fall down the list really disapoints me. Looking at the stuff that stays at top. There are a lot of varryablea, but I've found one constant the 65F9 idle jet seems to be the best for any setup. I'm currently running a 60F9 and with some custom 40mm chokes I had made. And the car stumbles just a little more than it did with the 38mm chokes. Once I move up to the 65F9i think it'll be solved. Also I'm running a 45 acceleratorbpump jet and I feel its just too small. No one ever really messes with that jet. This jet squirts a straight streem of gas down the carb durring large stabs at the throttle. And this is where people seem to be having the biggest trouble with stumbles. I feel accelerator pump jet tunning would solve a lot of peoples problems, but no one really goes there.