Lynn is right on with the Weber tips...
I spent wayyyy too many hours tuning Webers and when they are right the motor sings. the problem is you will yank out all your hair getting it right <G> . I originally was going to use DCOE48 on my experimental, I bought a new one and then found out they don't have a choke circuit like 45. My idea was to tune my motor for peak HP. Probably F-8 tubes, air and mains to whatever they need to be and then utilize the starting (choke) circuit for the mixture leaning. To do this would have been pretty straight forward as the starting circuit is an enrichening tool, not a butterfly arrangment as most carbs have. Tune the motor, go up three sizes on the air jets and then make up the needed fuel flow using the starting circuit. This concept is a easy option as the lever uses a push pull cable, ya just have to route the cable backwards where it attachs to the carb so it will act just like a normal mixture control and not opposite directions. I would have also removed the spring so the lever would not default to the lean side but hopefully remain in whatever position it was in in case the cable actually broke. Better rich then lean in that case for sure.
This whole concept went right out the window when I found the 48 cannot be ordered with a start circuit. altho the 45 with the largest chokes ( actual ID of the carb bore) installed would not have given up too much HP. I do have a brand new 48 sitting here if anyone wants a smokin deal. I have not taken the cap off yet to look but my guess is it has F-2 tubes, 160 mains, 180 airs. As Lynn says you will need alot of jets to dial the carb in and when you get through you will end up with alot of tubes, jets chokes etc you will never need again. they just sit there in the tool box and bring back alot of good/ bad memories. <GG>
On the dyno stories I have many but one still sticks in my mind. Back in another life I lived in Apopka Fla and had a very nice Dyno at my house/shop. Mostly SCCA regional guys would buy time, out of 100 guys there might have been 5 who actually had any idea what they wanted and how to achieve it. The rest were a pain in the ass so I quickly starting catering to the street rod, IMSA ,Busch, marine, drag and high dollar round e round teams. Life got alot more interesting then. One day an old friend' bones' called and says he needs to buy alot of dyno time for he was chosen to develop a 4 valveMercedes engine to go in Bob Strange's car. They were making an entry into a I think a SCCA pro class and B.F Goodrich was pouring a ton of money into the team, and I mean a TON. Well, to get baseline he shows up with a stock engine and we machined up all the adapters, brackets etc, etc, etc. As anyone knows who does dyno work that in itself is a full time job. So we make a few pulls to get some numbers and the results were ok but not impressive. Now, as a good racer knows one must NEVER disclose the speed secrets and will not give a blow by blow account of what ensued, but needless to say we went through 'several' motors. Modify this, blow it up, do an autopsy, modify that,blow it up, do an autopsy, yada yada yada. Well, these motors were not out of american cars, they were Euro ones. I bet BF Goodrich spent 100,000 bucks with Flying Tigers airfreight in shipping alone to provide us with additional cores so the development could continue. Long story short, got the motor pretty competa tive, on the second outing Bob ran a quick lap and the " testicle" inspectors strapped us with a intake restrictor that we never were able to overcome. The old addage, air and fuel in,,, HP out. Limit the air and you are screwed. I HATE rules. We are paid to cheat,,,,,,,,,,,, they are paid to catch us. Ahhh, life in the fast lane. When I moved here to Jackson Hole I sold all my racing stuff, my dyno went to Jasper Engines for their entry into cup racing and it then went to Penske racing. I have been told it is still used quite often for restrictor plate stuff. I do miss the hours of ' music" a motor makes when singing at top rpm on the dyno. maybe thats why I have a pretty stout V-8 smallblock in my experimental. <GGGGGGGGGGGGG> And as Lynn says, I too have a hearing loss but the price was worth it.
Ben.
Ben Haas
www.haaspowerair.com
To: flyrotary@lancaironline.net
Date: Thu, 7 Jan 2010 01:02:10 -0500
From: lehanover@gmail.com
Subject: [FlyRotary] First start
thank you for all your input. guess I won't buy 25 gallons of antifreeze to dump in a 55 gal drum! no, I'm in no rush, hell, it's raining every day around here, I can barely fly what I have.
the msd has a limiter circuit. I think I can trust it to work. I could disconnect the trailing plugs at first since they have no limiters. I have to review the msd literature. I think I need to snip a wire to make it think I have a 6 cylinder engine (?)
I need a light weight prop, considering how my engine mount came in at some staggering 30+ lbs. the exhaust was hefty too. I need to find a used one for now.
with a carb is there a need for an oxygen sensor? will I tune the jets othermeans? ken welter said he'd help me with those, he's figured his jet sizes long ago.
[Lynn - coffee comes in a can? I dump it from a bin at the store into a paper bag and grind it at home! ☺ yes, and real beer comes in a bottle requiring an opener! it's a Pacific NW thing]
ummm, the "elephant with diarrhea" . yes, it actually gets hits with google, but no sound tracks [thank you] ☺ kevin
4 cylinders for a 2 rotor. 6 cylinders if its a 3 rotor.
Unloaded the oxygen sensor will be all over the place with low temps. A heated sensor if you want to tune low power. Loaded the sensor will stay hot and read accuratly. And, or, EGT probes 3 incha out from the port. Best power is about 1600 degrees or, 12.7 F/A. This is actually very close to best power with a margin on the rich side. This to support good apex seal health. Once at cruise you can lean to rough running and back up a bit to smooth just like an airplane, except it will run far leaner than a piston engine. Of course the power goes down along with the reduced fuel flow. For short runs you just pull off throttle, but for long runs, the throttle stays up and fuel flow is reduced.
One tuning trick for racers is to get on a long straight at full tilt and shut off the fuel pumps. If the power drops off instantly it was too lean. If the power goes up a bit and then goes away, it was right on mixture. (just rich of peak EGT).
This would be too lean also for long apex seal life. If it builds power for a second or longer then goes flat, it was a bit too rich. Kind of crude but it works, and tells you where you are with no equipment at all. The idle circuit is all by itself.
Power is all from the booster. The big tube hanging in the middle of the choke, or main venturi (also changable) Overall fuel supply is the main jet. Mid range and transition is the emulsion tube. F-7, F-8 or F-11 is all you need for every situation. Usually F-7. Top end mixture is air corrector. Fuel level too high to too low is 3 main jet sizes. Two air corrector sizes is the same as one main jet change. 99% of all the jets anyone buys are usless and never get used. All of the jets to cover a scalding hot day or a winter day fit in a very small pill vile. If your chokes are the same as Kens, just use the same jats he uses. He hammers his with a nitrus shot to get off the water. He also shuts off the trailing plugs during nitrus to prevent detonation. He knows what he's doing.
You cannot keep new lightly oiled AN-4 bolts in a paper bag. There is a bar across the bridge from here. The guy has beer in a bottle. But its just to look at. He won't sell it or open it.
Don't feel bad. Its cold here in Florida. Some Northwest weather spilled down here.
Lynn E. Hanover
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