Nova 45 DD going lean?

[John Beardslee]

Hi Andy,

As long as the oil in the fuel is enough to make the seal when running then the gap can be pretty sloppy. Good old castor right?

Thanks, John

 

[aaron alberico]

John

Don't know why Nova have changed them!

As I got them to do the pipes with a 10mm (.393) stinger all ones I've had have been with 10mm

And personally I run even bigger.

 

[John Beardslee]

Hi Aaron,

Interesting, guess I'll open one up and see how it runs, I can always make it smaller if it doesn't work. I do have a large spray bar in my carb.

Thanks, John

 

[Olly]

Hi John

What size did you drill out the spray bar to?

Thanks

Olly

 

[Buckshot]

I am currently running an OLD CMB 100

Best "big block" they ever built.

 

[Andy Brown]

Hi Aaron,

Interesting, guess I'll open one up and see how it runs, I can always make it smaller if it doesn't work. I do have a large spray bar in my carb.

Thanks, John

John,

If you are running the stock carb then stay with the .355"ish bore that you have if the engine is in a rigger. If in a sport or mono I would actually recommend a smaller carb bore (about .350")

When I ran the nova on the stock carb I had to bush my stinger down to .360" to get everything working right. That was in cool weather in a rigger. If you make the stinger bore bigger the engine will exhibit the problems that Olly is having. The .355" stinger bore is a different story in a sport hydro or mono. It can be run, but the carb must go much smaller or the spraybay must go much bigger.

C/R, nitro %, length and size of fuel lines and several other things effect the final combination.

I can't give exact number for every application. There are many factors. Knowing how it all interacts together and then tuning to the sweet spot is what makes the difference.

The things I am talking about here are crucial to good running nitro engine and this information is understood by very few. Not knowing this stuff is why so many people struggle with nitro engines.

P.S. John, I missed that you have a bigger spraybar. You could then sneak your way up on stinger bore until it starts going lean at the top end of the Straight.

 

[aaron alberico]

Hi Aaron,

Interesting, guess I'll open one up and see how it runs, I can always make it smaller if it doesn't work. I do have a large spray bar in my carb.

Thanks, John

John,If you are running the stock carb then stay with the .355"ish bore that you have if the engine is in a rigger. If in a sport or mono I would actually recommend a smaller carb bore (about .350")

When I ran the nova on the stock carb I had to bush my stinger down to .360" to get everything working right. That was in cool weather in a rigger. If you make the stinger bore bigger the engine will exhibit the problems that Olly is having. The .355" stinger bore is a different story in a sport hydro or mono. It can be run, but the carb must go much smaller or the spraybay must go much bigger.

C/R, nitro %, length and size of fuel lines and several other things effect the final combination.

I can't give exact number for every application. There are many factors. Knowing how it all interacts together and then tuning to the sweet spot is what makes the difference.

The things I am talking about here are crucial to good running nitro engine and this information is understood by very few. Not knowing this stuff is why so many people struggle with nitro engines.

P.S. John, I missed that you have a bigger spraybar. You could then sneak your way up on stinger bore until it starts going lean at the top end of the Straight.

Andy is spot on!

It's hole combo that has to work together!

I've run .510 bore carb on my 46DD! Don't mean it will work for everybody.

Hope u guys figure out problem fast! Set up right Nova46 will produce great power and awesome Rpm's.

Regards Aaron

 

[John Beardslee]

I'm not running the stock carb now but did some of the time last year in an older rigger. I'm around .420 on the carb bore now with an 1/8" spray bar so according to what you're say I can work my way a little at a time larger on the stinger. I'll play leap frog with the two pipes until I get it.

Thanks, John

 

[Andy Brown]

I'm not running the stock carb now but did some of the time last year in an older rigger. I'm around .420 on the carb bore now with an 1/8" spray bar so according to what you're say I can work my way a little at a time larger on the stinger. I'll play leap frog with the two pipes until I get it.

Thanks, John

Sounds good John! If the stinger is too small the engine will go rich as the boat progresses down the straight. If the stinger is too big the engine will sag lean about 2/3's down the straight. When the stinger is just right the engine will pull out of the corner very strong and accelerate for the full straight with no lean sag or not going rich at the last half of the straight. This is temperature dependent. In cooler weather the engine will want a smaller stinger. In hot weather it will want a bigger stinger bore. That is why we sold stinger bushings at CMDi for the AB 67 and 80 pipes. Stock bore was .472" and we have bushing sets .410", .430", .450".

So in the end you could set up your two pipes, one for cool Spring and Fall weather and one for hot Summer weather.

 

[John Beardslee]

Thanks Andy,

 

[dwilfong]

Andy is there a way to calculate the spray bar ID compared to the boar of the carb or is it a cut and try kinda thing?

 

[Andy Brown]

Andy is there a way to calculate the spray bar ID compared to the boar of the carb or is it a cut and try kinda thing?

David,

I have determined a formula that works for me. It includes engine displacement, RPM, Nitro%, Header diameter, Stinger diameter, carb bore, and stinger bore.

After that there is still a little cut and try, because things like oil % and brand will have an effect, not to mention details like how the tank in plumbed....and even how the mixture flows through a particular engine.

 

[dwilfong]

Andy is there a way to calculate the spray bar ID compared to the boar of the carb or is it a cut and try kinda thing?

David,I have determined a formula that works for me. It includes engine displacement, RPM, Nitro%, Header diameter, Stinger diameter, carb bore, and stinger bore.

After that there is still a little cut and try, because things like oil % and brand will have an effect, not to mention details like how the tank in plumbed....and even how the mixture flows through a particular engine.

Thanks for the insight as always.No wonder your boats and motors are in the for front when you are at your best.

 

[Glenn McClintic]

I have limited experience with the Nova 46 and I'm runnng a rear exhaust motor with the wrap around header in a mono. I could never get the Nova remote needle to flow enough fuel, so I installed a Don Ferrette needle base with the course OS needle. It's mounted to the engine rails and works fine. I also run large fuel tubing from the plastic Sullivan tank to the remote needle and to the carb, but the internal tank tubing is the standard 1/8". The carb is stock with the low speed needle removed. Pipe is unmuffled Nova as short as I can get it. I noticed a big difference in consistancy when I added 2% castor to my fuel which is 65% with16% total oil. No water restriction. It runs awesome.

Don't know if any of that helps, just what works on this motor.

Glenn

 

[Andy Brown]

Nova made a BIG change on the 46 when they changed from the wrap around to the DD. That being a MUCH longer rod. Putting that longer rod in the new DD engine after they figured out what head and pipe and carb was needed for the wrap around engine through a monkey wrench in the works. The Longer rod increases the piston dwell at TDC. This does 3 things. #1 It advances the ignition point and #2 it gives the fuel more time to burn while the cylinder is at maximum pressure near TDC. #3 It shortens the dwell time at BDC when the transfer ports are open which allows less mixture into the cylinder which will provide less cooling and burn up even quicker...advancing the ignition even more.

That is the same as putting a hotter plug in the engine, increasing the C/R and reducing fuel flow all at the same time.....and doing it to an engine that was already tuned properly.

It is easy to see how that can lead to the problems that have been discussed here.

Oh and a fourth thing the longer rod did was change the engine from being an engine that had incredible acceleration out of the corner to an engine that will not accelerate so quickly but will spool up to higher rpm and the end of the straight.

The bottom line is that the Nova DD engines are MUCH different animals than the wrap around engine, including the .21.

I am not saying the longer rod is a bad thing. I welcome the longer rod. It is close to the MAC 45 rod length. I am just saying the DD and the original engine are two VERY different animals and what was learned to work well on one will not work so well on the other.

 

[aaron alberico]

Nova made a BIG change on the 46 when they changed from the wrap around to the DD. That being a MUCH longer rod. Putting that longer rod in the new DD engine after they figured out what head and pipe and carb was needed for the wrap around engine through a monkey wrench in the works. The Longer rod increases the piston dwell at TDC. This does 3 things. #1 It advances the ignition point and #2 it gives the fuel more time to burn while the cylinder is at maximum pressure near TDC. #3 It shortens the dwell time at BDC when the transfer ports are open which allows less mixture into the cylinder which will provide less cooling and burn up even quicker...advancing the ignition even more.

That is the same as putting a hotter plug in the engine, increasing the C/R and reducing fuel flow all at the same time.....and doing it to an engine that was already tuned properly.

It is easy to see how that can lead to the problems that have been discussed here.

Oh and a fourth thing the longer rod did was change the engine from being an engine that had incredible acceleration out of the corner to an engine that will not accelerate so quickly but will spool up to higher rpm and the end of the straight.

The bottom line is that the Nova DD engines are MUCH different animals than the wrap around engine, including the .21.

I am not saying the longer rod is a bad thing. I welcome the longer rod. It is close to the MAC 45 rod length. I am just saying the DD and the original engine are two VERY different animals and what was learned to work well on one will not work so well on the other.

Andy Are you so sure about this longer rod in 46DD motor?

As the part numbers are the same and my 46 wrap around and DD measure the same rod length!

Yes 21DD has a longer rod!

Regards Aaron

 

[mtruex]

Same thing here.

 

[SayMikey]

Same thing here.

Cya Sunday Martin Jeff and I will be rooting for ya from the infield. Honk when toy get to the lead

 

[Andy Brown]

Nova made a BIG change on the 46 when they changed from the wrap around to the DD. That being a MUCH longer rod. Putting that longer rod in the new DD engine after they figured out what head and pipe and carb was needed for the wrap around engine through a monkey wrench in the works. The Longer rod increases the piston dwell at TDC. This does 3 things. #1 It advances the ignition point and #2 it gives the fuel more time to burn while the cylinder is at maximum pressure near TDC. #3 It shortens the dwell time at BDC when the transfer ports are open which allows less mixture into the cylinder which will provide less cooling and burn up even quicker...advancing the ignition even more.

That is the same as putting a hotter plug in the engine, increasing the C/R and reducing fuel flow all at the same time.....and doing it to an engine that was already tuned properly.

It is easy to see how that can lead to the problems that have been discussed here.

Oh and a fourth thing the longer rod did was change the engine from being an engine that had incredible acceleration out of the corner to an engine that will not accelerate so quickly but will spool up to higher rpm and the end of the straight.

The bottom line is that the Nova DD engines are MUCH different animals than the wrap around engine, including the .21.

I am not saying the longer rod is a bad thing. I welcome the longer rod. It is close to the MAC 45 rod length. I am just saying the DD and the original engine are two VERY different animals and what was learned to work well on one will not work so well on the other.

AndyAre you so sure about this longer rod in 46DD motor?

As the part numbers are the same and my 46 wrap around and DD measure the same rod length!

Yes 21DD has a longer rod!

Regards Aaron

Yes, my mistake! It's just the 21. Maybe I heard they were thinking about changing the 46 rod and I jumped the gun here.

 

[John Beardslee]

Any progress over the week end with Olly's engine?

Thanks, John