Nova 45 DD going lean?

[Elias Vazquez]

The piston has nipped up in the liner very slightly. It could be from running the engine too cool at some stage

Are you running the stock water fittings without any restrictions?...you may be overcooling the top end of the motor, try restricting the amount of water thru the cooling cap. Some of the guys solder the inside of the cooling cap fitting, then drill it out with a small diameter bit. I use S.S. set screws with different size holes .040-.060, and a pressure bleed off hole in my 90° fitting on my rudder.

 

[charles siler]

The piston has nipped up in the liner very slightly. It could be from running the engine too cool at some stage

Did you debur the liner before you ran it .

 

[Elias Vazquez]

Charles, I was thinking overcooling, not allowing for the metals to properly aclimate on the top end where the piston crowns on the sleeve can result in premature piston wear. Especially when they're new. Also lean conditions...not getting adequate lubrication as well.

 

[Chris Wood]

What fuel / oil percent is he running ?

 

[DaveThynne]

60% fuel, 10% klotz kl200, 6% castor. Standard water fitting in, plugged outlet, with 1mm hole in top of water jacket. Water flows at around 80 on a gen4 boris. It usually runs HOT! I had a test day in June running it hard testing a lot of different load, and different running temps. I had a few glow plugs black holed in this process. Im thinking one of these runs did the damage

 

[RonShaw]

Dave,

Elias and Charles are providing excellent feedback above. Proper cooling/temps are very important with any ABC engine. Proper break-in of the engine up front before even going to the pond is crutial. Until the "squeak" fit has been properly eliminated and broken-in, bench running with a temp gun and adjustable water cooling to keep the top end temps at around 180-200 is crutial. Also, until the "squeak" fit is eliminated, slowly heat the top-end to 180-200 with a heat gun before you even attempt to start the engine each time. I would also like to include that we are seeing great results running as high as 50/50 racing grade synthetic/castor of your choice, in the 15-18% total lubrication range.

All of these steps will help assure proper break-in and a longer lifespan for your Novarossi engines.

 

[Elias Vazquez]

Dave,

Elias and Charles are providing excellent feedback above. Proper cooling/temps are very important with any ABC engine. Proper break-in of the engine up front before even going to the pond is crutial. Until the "squeak" fit has been properly eliminated and broken-in, bench running with a temp gun and adjustable water cooling to keep the top end temps at around 180-200 is crutial. Also, until the "squeak" fit is eliminated, slowly heat the top-end to 180-200 with a heat gun before you even attempt to start the engine each time. I would also like to include that we are seeing great results running as high as 50/50 racing grade synthetic/castor of your choice, in the 15-18% total lubrication range.

All of these steps will help assure proper break-in and a longer lifespan for your Novarossi engines.

X2....I had a few glow plugs black holed in this process. Im thinking one of these runs did the damage....X2

 

[Elias Vazquez]

I stay on the rich side of the needle...motors always reward me for it!!

 

[Elias Vazquez]

When I first put in I don't jump on the motor real hard, make a few slow laps letting the motor aclimate to water temp., gradually increasing throttle and listening & seeing what the motor/boat is telling me...making small/gradual needle adjustments along the way. Richening the needle every couple laps is sometimes necessary during the race as the fuel pressure drops in the tank.

 

[dwilfong]

some are squeaker than others.......

Hard tight pistons take a lot of time to break in..........................

I think a brass head button and smaller custom cooling cap would hold more heat in the eng and be less sensitive to temp changes........

May be worth a try.................

 

[Charles Dukes]

Olly,

I bought a CMB 21 Beta early 2015 and put it in Pete's boat (Speedmaster)and it does the exact same thing. You run it rich and it burbles around the pond at about 50-75% speed, you slowly lean it out and it picks up speed, then it suddenly takes off at extreme speed, sags to almost quitting, takes off again. So you richen it back up and it goes back to 50-75% speed and burbles along. Lean it out again and it does the exact same thing. I have re-plumbed the entire boat fuel system with larger lines, larger tubing, head clearances all over the map, a variety of pipes, props, plugs, different inboard needles, different pipe lengths, you name it. I finally gave up and put the CMB VAC motor back in the Speedmaster and it runs great, like it did before. I then put the Beta motor in my Yellow Speedmaster (which has been running with a MAC). Beta runs just fine, great speed, no sagging. For some reason my yellow Speedmaster has always had better fuel flow to the carb than Pete's Speedmaster. I have noticed Pete's boat has always been more sensitive to changes in the needle than my yellow Speedmaster. The Beta motor was starving for fuel when it really got on the pipe with the green boat. I might try elevating the hopper tank or drilling out the spray bar and see if I can get it to run in that boat. My two cents

BTW, you sure go through lot of fuel figuring these things out!

 

[Charles Dukes]

One more thing.

I wonder if it could have something to do with these newer motors with much less crankcase volume. I thought that was supposed to be the main difference between the CMB 21 VAC and the CMB 21 Beta.

I don't know if the Nova 46 DD is a low crankcase volume design or not.

 

[dwilfong]

Transfer port area has a lot to do with how the eng will take high nitro. There is a bridge in the transfers on the BETA.

The nova 46 has them also.

High nitro mix needs volume to move the suspended fuel.

If not it will lean over at high RPM.

Eng designed for lower nitro will not flow high nitro 60/65% threw the small case and ports.

Bigger spray bars will only dump more fuel the eng can not flow threw the small case and make it harder to find the needle.

Try a lower nitro % and smaller props you may be surprised.................

 

[Charles Perdue]

For what it is worth....one unusual going lean scenerio that I ran into was the cap that was used to plug off the third fill line going into the fuel tank was too thin and it did not seal tight enough. It was the common vinyl cap that is used to seal small drill/mill bit containers. It felt tight but when the engine came on the pipe, it would leak just enough pressure to cause it to go lean. It took several weekends at the lake to find this one. We swapped out fuel tanks, ran new fuel line, installed a new fuel filter and just about everything we could think of but continued using the same fuel line cap.....DUHHHhhhhh.

Installed a thicker, heavier grade cap and no more going lean problem.

This may help someone.

Charles

 

[KenOlvis]

If some one was to pressure test the fuel supply from tune pipe line to fuel line to carb what would be a safe limit of pressure to test?

Also how much pressure on average dose

.12 - .91 produce.

Dose somesone make a tool to test with before I make one up to check my fuel supplys in my boats

Thxs

Ken

 

[Charles Perdue]

You must use a one way check valve between the pipe and the pressure gauge to hold the pressure on the gauge side when testing the pipe pressure to keep the reading steady, otherwise you would be trying to read the gauge as it is pulsing, Not a good way to get an accurate reading.

Charles

 

[charles siler]

Had a bit of a set back on the twin and It could happen to anyone. My hopper tank came loose from the bottom of the fuel tank. No biggy you'd think at first and had to detect even on a single at first let alone a twin. Never the less as the particles of soldier started to format in the filter boom lean dead cost me a piston liner and I have to replace the tanks. Just something else too keep your eyes on gents pass ya later Charlie

 

[DaveThynne]

Ok guys I have sorted my issues out with my set up. Medium fuel pressure line was not large enough for my set up, even using 5/32 lines in my fuel tank. After changing nothing else but my pressure line I was able to go back to my usual pipe length and props. The boat ran good, but needed a very rich needle setting on launch and it needed to be richened up quite a lot to get it to step back up. After a little more homework, i bushed my nova muffled pipe's stinger from 10mm to 9.6, this gave me a little more fuel pressure. After sorting through some load issues at our last race, and some testing since and it seems a very happy set up with pipe length at 9 inches and a cupped 1655

 

[RonShaw]

Nice!!! Thanks for the update Dave.

 

[dr gary turner]

Check with M Bullard. His running great. Bad fast in an SST. Different head button and NR nitro non muffled pipe.