piston pounder

Hey all, Im having a bitch of a time tuning the 50dco Weber that I bought from Mazdaracing. Its like im running out of fuel in the uper rpms and am getting some detenation noises threw the carb. Now get this it doesnt always happen, only when under load and still not everytime. This was my first Rotary engine rebuild and the motor runs good (comp. and no smoke). I street-ported all the housings and put small bridge-ports on the end housings, making it a half-bridge. My exhaust is Mindtrain (header, 2 1/2" piping, Big throats muffler) so that shouldnt be the problem. The timing is set at Yaws reco.'s, and no matter where I put it still detenates. The fuel pump is a Holley Blue and same thing as with the timing no matter where I set it, it still ***** up!. Im going CrAzY trying to get this thing tuned! and am about to say **** it and sell all my **** and get a Z. Ok the last part was a lie, I love these cars!. Ive asked for help here before and got no help, someone on here has to know my problem and experienced something like this before. Finnally sorry about how long this is, I apoligize. Last thing heres what I have in the carb right now
-main gas jets 180
-air bleeds 200
-F-11 emulsion tubes
Im not to sure about the idle jets and the acccel. jets. Also before I go, remember my elevation here in Colorado is nearly 1 mile above sea level. ANY INFO IS WELCOME. Laterz. Jami.

WackyRotary

I don't know for sure you problem. I have a 50DCO also. Do you have a fuel pressure regulator? THats VERY VERY VERY important. I had a cheap one that worked for a little while and it failed one day and the car ran crappy as hell!!! It got horrible fuel milage and the throttle was very strange and ran excessively rich. Anyway, get a holley regulator which is actually cheaper and keep it at 4psi about. Make sure you have a fuel filter that is very clean ofcourse and check it often. Once I got that regulator, power was much better over the whole rpm range pretty much.

I am not sure what your exhuast is, but I custom made mine to collect right near the rear axle like Racing beats long tube header. That ALSO made a HUGE Difference in power.

I have a full 12a bridgeport with 240main jets, 170correctors F11 emusion tubes. Good power from that combo. The idle jets and accerator pump nozzles are less critical unless you notice it stumbling very baddly when you give it gas. I'm uncertain how much different the relative air density is at 1 mile high, but its probably about 78% of sea level air density.

piston pounder

One more thing what did you do with your return fuel line and also the vent line under the hood?. I plugged my return line off because fuel would come throgh it after it built up pressure.

REVHED

That sounds really weird. You sure that it's detonation and it's not your ignition breaking up or something like that. My only other guess is that it's a combination of your air bleeds being too big and the mains too small causing you to run really lean in the top end. I'm not sure about the jetting on DCOE's but on an IDA 200 air and 170 fuel would be way too lean. I'm actually running 190 fuel and 140 air on an extend port.

WackyRotary

I have virtually everything possible removed under my hood. I don't know why you have the return line or how because the 50DCO has no return line on it. You just run your fuel pump to your regulator and have it relatively close to the carb. There is no return line I'm aware of? In stock form you do, but this is not stock.

I have no charcoal canestor and the tubes go to open air. I don't have fuel coming out anywere it shouldn't. Oh, I removed the one-way valve that the main fuel line from the tank goes through before the filter and fuel pump. I also have a holley pump on my car by the way. Also, be sure you timing is right. I know at upper altitudes that people can run more advance since the the air is thinner, but have it at stock, its the safest.

piston pounder

I also have all my emissions stuff removed and are open into the air, the metal return line to the tank is still there and after the tank builds up pressure fuel will drip out of it. So I plugged it with a cap. That one way check valve by the tank has also been removed. I never thought that maybee my ignition could be getting weak, what should I check for?. I have thought about going down a size or two on the air bleeds, but the Losers at Mazdaracing said it should work(yea right). One more thing when I first got this carb I had the fuel pressure set at about 4psi, and every now and then fuel would start driping out of the air horn. Ive re-adjusted the float levels and that problem stopped, just thought I would mention that. What really bugs me is that this problem isnt real consistent!.

79+80_rx-7

well.. i dont think their should be pressure in the tank... is there suposed to be??? dunno...


LATERZ, Andrew

DriveFast7

iTrader: (1)

For my Dellorto 48 DHLA it didn't come with a return line fitting on it. After talking to several road racers I bought a fuel fitting for the carb that has the fuel inlet and return on it. Only cost 5 bucks. It's a good idea to let the unused fuel in the hot engine bay get pumped all the way back to the cool fuel tank. I bet you can get such fitting for 50 DCO.

You guys with ported engines really need to invest in a good air/fuel meter. They make turning the carb MUCH EASIER, ACCURATE, AND QUICKER. Autometer and Intellitrox sell cheap ones thru summitracing.com. Use a good ol cheap GM oxygen sensor and bung.

What size needle and seat are you using? Should use 3.00mm.

A fuel pressure gauge will help out a lot here.

There will be pressure in the fuel tank since it is sealed and fuel is being sucked out of it. That's what the return line and charcoal canister help alleviate.

-bp-

WackyRotary

I am not following you don't have the return line hooked up at the tank? I still have the tubing going up to the front, that is were it goes to open air. If you plug it off in the back by the tank, it stands to reason it will build pressure and leak there when you brake. I have mine just open up by the engine, never leaked, I don't know why yours would?

piston pounder

No Wacky, its the same as yours from what you described. It will drip fuel out of it during agressive driving when pressure builds up in the tank!. Im very suprised yours dosent do this. I do have an a/f gauge, I just dont know how accurate it is. At idle it reads just one bar below halfway towards lean. While driving it doesnt even register, until right when I get off the gas completly. This is why I think im running lean and detenating.