[NSRCA-discussion] YS DZ pump settings

Sun Feb 12 01:20:32 AKST 2006

Ed the back fire could be its too rich rather than its too lean. Since the DZ motors inject raw fuel in the intake valve a too rich setting will result in a chamber full of fuel that doesn't compress really well and doesn't burn well so raw fuel then hits the pipe and burns there.

140DZ on 30% heli CP should be up near about 8500 rpm. If you are not there then its too much prop. By the way ona  fresh motor that should not be too much prop. But if its been running on Buzzy stuff....who knows what its like. Check the RPMS. 

Pump should be about flush maybe a little inside which is rich of flush. In is rich and out is lean on the pump. Then the HS ends up around 1.5 and can go as closed as 1 turn open. This all depends on the pressure the pump is putting out. The richer the pump the more fuel can squirt through in the given time frame. So the needle will need to be closed more. Basically when you adjust a pump you adjust the HS needle opposite to that. Richen the pump then you lean the HS to match the setting. 

Now if the motor is leaking air....then it can backfire and go lean while in flight. Look at valve cover and gasket. possibly face the mating surface on the rocker cover. Look at orings on the pushrod-pump tubes. and look at the oring that is on the base of the pump under the black plastic cover. 

If it were my motor I would tach it. If its 8500 or so its good in terms of rpms. The HS on the 140's was a little flat. turn it slowly leaner. you will find actually 2 peaks. one at about 2 turns open and one at about 1.25turn open....Then 2 turn open one will be back about 300 rpm from the proper one. The needle in the middle of these two will act like its not doing much at all....this is where the motor is too rich!!!  

Another thing that will really help the motor idle and transition is a small header tank. I started running a 2oz header tank. I can get 16mins out of my 20oz plus 2oz header and the motor never burps. This is important as the burp is a lean run. 

You will not see the carb build up with the CP fuel. In fact it will start to clean it out of the motor. The NMP header has a huge volume and should not be a problem with carbon build up. I get a very slight amount on the exhaust valve stem and the header turns black but not really any build up....I would look at taking the head off it and removing the exhaust valve. I scrape the carbon off with an x-acto blade. If the valve is really carboned up it can affect things but I have never gotten there with the Cool Power.. I don't know what Morgan uses for oil but its the good stuff. Non of the other fuels I have seen or tried have come close to its performance. We even converted a local "expert" to it. He was having trouble....problems solved with some good fuel.

On the DZ's while too lean can hurt them too rich is worse. I listen with my calibrated ear and can tell when the motor is detonating. You don't want that. I adjust the HS when the motor is at idle(high idle) and then throttle up slowly listen for detonation. If it gets that hollow banging sound throttle back and open the HS...then throttle up again. you should be able to get it transition very smoothly without detonation. If the HS has to be open plus 2turns then the motor has an air leak somewhere they just don't run there. I have 3 160's and a 170 that all run at 1.5 to 1 turn open. The one turn open ones have needles that are worn and need to be further closed. I also had 3 or 4 140's and all of them ran at the same needle settings. Another sign of an air leak is oil all over in the cowl. There will be a little that mists out the carb...but if its externally lubricated its leaking somewhere. Check head bolts, check the rocker cover and gasket. Check the pushrod-pump tube orings. check for  a cut fuel line or a pin hole at the fuel nipple. Also check the fuel lines to make sure they are tight on the nipples. We had a problem a few weeks ago with old fuel line that kept coming off the nipple. the motor would run OK but the fuel line was leaking then next flight it would pop off. Finally we cut to a new section and it stayed on and we had to lean the motor out. It was leaking air where the fuel line attached to the carb from the pump.

The key especially on the 140 is the 8500 rpm. load it down to 8000 and it will act like a temperamental beast. let it rap up to 8500 and it will have as much or more power than 2 strokes. Besides the smaller diam props will make noise easier although at 8500 the 16's will be under AMA noise but at or above FAI noise.  An air cleaner or a restrictor takes care of the 1db and put you at or under FAI limits.

I would lean it down to 1.5 turns open and throttle it up slowly and let it warm up. Set the pump slightly inside flush. See if it gets that hollow too lean sound. Then look for the idle to be rough if its too rough its rich and if its surging its too lean. Then as you transition if the top end mixture is good but the transition gets lean then richen the pump and reset the HS. They work together. The pump goes leaner the HS must go richer as the pressure is less. You might be surprised and it was way to rich. Blubbering rich is a bad thing on the DZ. I have actually seen bend con-rods on DZ's run too rich. It "hydrolocks up" it has all that raw fuel in there. The fuel has to mix with the air as the intake valve opens. If it just runs in and doesn't spray then its too rich.

TN
  ----- Original Message ----- 
  From: Ed Deaver 
  To: NSRCA Mailing List 
  Sent: Saturday, February 11, 2006 8:56 PM
  Subject: [NSRCA-discussion] YS DZ pump settings

  My buddy has a 140DZ and is having problems.  CoolPower 30% Heli fuel, 16.5x12.5W prop, flying at sea level.  

  We had been using Magnum DZ but his header kept getting plugged, so switched fuel.

  Now he is having problems with it backfiring.  He lost his spinner the other day, and another time it was held on only by a thread or so on the spinner bolt.

  He has tried richening up the pump(turning in) and has also tried running it blubbery rich(2.25 turns out)  

  On the ground, it starts easily, runs well he states, then soon as taking off, it begins to run ragged, and recently yeilding 10 of 10 dead sticks.

  Any suggestions??

  Thanx in advance

  ed

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