Mazda sports racer with an early 12A bridgeport, engine will run fine part throttle but falls flat on its face no power under full throttle load. 48 IDA with 205 mains and 180AC, runs one msd fire lead and trailing at same. Went through the carb and up and down on jetting all weekend with no change, I think its ignition getting weak under throttle load. We use two hall effect sensors in the distr, triggers one msd which fires both coils. this is a common setup and works well for others, msd plug wires ohmed out. I am at a loss need all suggestions

 

what size of venturies are you using.

 

36 MM Venturis

 

Those are pretty small venturis.

How is the ignition setup exactly? Are you running the leading and trailing together for each rotor?

 

Hall effect sensors in distrubtor, using the leading sensor to trigger the msd which then fires both coils, I have swapped sensors no change and swapped coils from leading to trailing no change.

 

Fuel pressure/volume?

Vernon

 

holley blue fuel pump 4.5 lbs pressure, we went up and down on fuel pressure up and down on jetting, wend through the carb completely. clean as can be clean filters

 

I certainly wouldn't run an ignition system that way. To be blunt, it's functioning as it should—that's why there was no change when you swaped parts around.

Why not do some research into rotary ignition systems? There is a ton of info on this forum. Since you already have an MSD, you could go for the DIS setup.

Just some questions for you. Why did you install a Hall sensor when the stock VR sensor is perfectly acceptible, especially with an MSD? Did you change the reluctor wheel at all? Also why do you want to run your ignition through a cap and rotor when it's not necessary, at least on the leading circuit (which is the only important one on a rotary). If leading is run direct-fire, then the trailing could be routed through the leading part of the cap (to take advantage of the carbon button and only one gap to jump). Both leading plugs could also be sparked twice per revolution to take advantage of the late-leading effect... That's probably too much information at this time.

Use these search terms in the 1st gen subforum: MSD-DIS, DLIDFIS, 2GCDFIS, ignition, direct fire, BR8EQ-14, J-109, reluctor, carbon button, cap and rotor

Just start off with those. They ought to keep you busy for several hours.

 

I guess I called the sensors in the stock mazda ig "hall Effect" they are simply the stock items triggering the MSD which fires both coils at the same time. I did just run across some "direct fire" ignition information, looks interesting. maybe I will try it. I am also going to pull the distr out this weekend and check for wear. The dam thing with a racing car is you cant really test anything you do to it unless you are at the track on a race weekend. I am in scottsdale arizona, not out in the sticks somewhere. some times I wish I was out in the cornfields!
thanks
keep the ideas coming

 

still up sh*t creek, I could be racing this weekend if the car wasnt fu**ed the more I think about it the more I think about it seems I have a fuel Problem. I run a holley blue and will try a fuel volume test, while running though the fuel pressure is very good and remains constant at 4.54 LBS. I intend to change the ignition to running two MSD firing two coils direct to plug ala DLIDIS Style and a HEI Ignitor to fire the trailing coil.

 

You did say that the fuel filter is confirmed to be clean, right? Have you verified your flow rate and pressure? You might need to install an in-line fuel pressure gauge (mounted where you can see it while driving) so you can see if there is a drop when you start having issues.

It sure sounds like a fuel issue to me. It's not backfiring or anything when this happens, is it? Strong smell of fuel? Smoke of any kind? If not, then my money is on the fuel system. Good luck..

 

well it had always seemed that the engine was detonating even though the timing was only 20 degrees (no advance) indicated. well back up the timeing to 0 degrees indicated thatn viola runs good!, I guess the racing beat pulley has moved and wedged enough to move the timing mark....has this ever happened to anyone else??? Always trust empirical evidence....that which is proven by fact.