Boast vs Transfer

[Terry Keeley]

Hey Adam: Ever play with opening the intake earlier (drum, disk, crank)? Most like to open 25-30* ABDC stok (lol).

 

[dwilfong]

Try opening at BDC and see what you get,,,,,,,,

 

[Adam Blevins]

I've moved crank and sleeve timings all over the place lol. I surprised myself and ive also threw a few engine parts away in my days of R&D

 

[TimothyJones]

To make it easier for all to understand, please identify which are the sleeve ports - boost, transfer, etc. Some are new at this hobby and are not up with the lingo. Picture will be most helpful.

Some of these liners have ports all over it and some are easy to identify but

pics would be really great.

I like this simple free program FastStone Image Viewer.

You can take a pic and add words,arrows,and modify the image.

Tim

 

[Marty Davis]

David Wilfong hit the nail on the head...

He probably didn't know about these type ports specifically but had the idea for sure.

If we could ever get one of the engine manufacturers to design an engine with what are called "Tea Cup Ports" we would have something special. Brian Callahan told me about this design and said that if we had that type of casting in the case, we would really have some HP. Look it up by that name and post what you find. These are port runners that actually protrude out the sides of the case similar to the Japanese motor cycles.

 

[dwilfong]

I have one with the ports you are talking about. IR.21

Remember I showed it to you in Norms garage a few years ago when you showed me how to make the buttons?

The Mercury 2.5 V6 I am playing with has the castings in the case like you are talking about.

I will post some pics of both when I get home.

Also the Cyclon eng from Russia has a very thick liner with cuts to direct the flow.

Also there is a guy in one of the Baltic states doing this with a gas eng.

Now if the Italians would just get on board..................

 

[dwilfong]

Here are a few pics of my IR .21

Look how the case is slap filled up and the ports continue in to the case.

I will get back to this eng some day when I have the time and a few spare pistons made up for it.

Ceramic coated bore is hard on the pistons. Need lots of oil to survive..

The Russian masters have a good handle on what is what.

 

[dwilfong]

Here is a sleeve fom a gentleman in the Ukraine. This is for a gas eng he is designing for production some day.

He got a little upset with me when I stated it looked like a Russian Cyclon eng sleeve.

At the time Russia was invading the Ukraine....................my bad..................

 

[dwilfong]

Funny most marine eng coming out now are just a rehash of a aero eng case thy already have.

It would not be profitable to make a true high performance marine eng designed for HIGH nitro.

You would have to start from scratch with the whole design.

But we can dream now can't we.........................................

Andy posted a pic of a fat belly case he designed.

Would love to see it again with some input on what is what................................

 

[dwilfong]

Here is a pic of a Mercury 2.5 block transfer port with the liner out.

Notice how the castings are.

 

[John Beardslee]

My 3W 150cc aero gas engine from early 2000 has tea cup style case castings I think. Other manufactures have had to increase cc to make the same hp.

John

 

[Marty Davis]

Here are a few pics of my IR .21

Look how the case is slap filled up and the ports continue in to the case.

I will get back to this eng some day when I have the time and a few spare pistons made up for it.

Ceramic coated bore is hard on the pistons. Need lots of oil to survive..

The Russian masters have a good handle on what is what.

Not really tea cup ports. The case has the ports well outside the normal case for Tea Cup Ports.

 

[Jack ODonnell]

Marty, I think the MB 40 pylon engine is close to what you are talking about. J.

 

[dwilfong]

Here you go.

 

[Brad Christy]

Marty, Andy, others,

I have always thought the function of the boost port was to fire a shot of fresh fuel/air mixture directly into the pipe, at the tail end of the exhaust charge, adding to the burnable fuel to the incoming exhaust charge as it returns from the pipe. Yes? No?

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Model Machine And Precision LLC

 

[Jim Allen]

Marty,

"If we could ever get one of the engine manufacturers to design an engine with what are called "Tea Cup Ports" we would have something special. Brian Callahan told me about this design and said that if we had that type of casting in the case, we would really have some HP. Look it up by that name and post what you find. These are port runners that actually protrude out the sides of the case similar to the Japanese motor cycles."

It is well documented & proven, with at least two available engines, that transfers with an inside & outside radius, can be better than the Tea Cup shaped ports developed & tested by Professor Gordon Blair Of Belfast University. The engineers at Aprilia proved beyond any doubt that curved transfers, with the correct inside & outside radius, that use the Coanda affect, can flow better than the Tea Cup shaped ports. Two engines that presently use these type ports are the QD Pioneer engines & the MB 40 pylon racing engines. Frits Overmars of Aprilia was instrumental in the development of the 35,000 RPM MB 40 engines.

Jim Allen

 

[Jeff Lutz]

Actually all the intake ports are really transfer ports. We started calling the port opposite the Exhaust the Boost Port because it boosted the charge upward to create the loop. Our engines use this loop to efficiently charge the cylinder and then empty the cylinder after the burn out the exhaust port. The side transfers are mass input ports to supply a LOT of charge. Opening the boost port a few degrees earlier starts the loop in a really straight line and CATCH the charge that the side transfers supply a few degrees after the boost starts supplying. Just a boost port wouldn't be enough to charge the cylinder totally so we need the area supplied by the side transfers.

I haven't worked a lot with grinding the channel that the side transfers use to charge the combustion chamber, but I suspect that it would make some difference in where the charge ends up to help it by some redirection. Of all the people that modify engines and work in that area, Stan, Jr and his Dad are probably at the leading edge of that technology. Jack and Steve O'Donnell probably know a substantial amount in this area as Jack has Teather Cars running over 200 mph and turning amazing rpm's.

Most of us RC boaters are more of the "Hacker Type". I am one of those

If you have ever seen one of Stan's liners, you would be amazed at the Jewelry Quality channels, etc that he puts in his parts.

There are some others on this Forum that are the real craftsmen in this area, but we seldom hear from them. Jeff Lutz is also one of them, as is Andy Brown. Would be nice to hear from them.

Since I started running the Nova Rossi 21DD I have not has to do a lot of modification. The engines are so well engineered that the pipe selection and carb selection makes it a dominant engine. I have found only a mod to the head button, a larger carb and some other very minor mods are all that are necessary. In fact I have run the engine stok (still can't spell that) most of time I have had mine. I now am starting to experiment in some more mods and each time it seems to give me more performance. Unless you have your boat/prop combination optimized, I wouldn't suggest that you do much. Once you do, then it does makes sense.

Thanks for the compliment Marty. I think this thread would be well served discussing engines from the past and mods that worked well for these engines. Some people have touched on big transfers flowing the best , and I would lean in this direction also. But, big boost ports have also proven to flow good fuel and do the same if not more than transfers. There have been a few engines that this was taken advantage of. Some of the old piccos had two boost ports with a divider. Typically these engines had small transfers. The picco 90 Competition had two boosts with small transfer area, and the picco 90 hydro had a small boost and larger transfer area. Both engines had the same bore and stroke and rod length. The only difference was the case and port lay out ( for the most part) between the two engines. Both of these engines are probably the biggest reason that drove Jack and Steve Odonnell into balancing engines (They were way out) . If you cut the divider out of the boost on a 90 competition and hog the case dividers out you have a huge boost area , add piston ports to the transfers and some good flow work, a little rotor work and it will out perform the picco 90 hydro that most people feel was piccos best 90 engine ever. Alot of big port engines like low volume pipes, and small port engines like big volume pipes, but Ive also used big pipes on big port areas and it worked well. At the 1990 Nats Ron Lauderdale had a twin Pinckert Daytona with picco hydro 90's he ran 72 mph through the lights , Tom Pretzfield had a twin Coyote with picco 90 hydros and he ran 80 mph and both had 1667's on them. The boats only difference were the hulls they had the same front sponsons. I asked my Dad "Why is Toms that much faster?" Dad said " the only difference worth talking about are the pipes" . Ron had low volume pipes that were muffled. Tom had bigger volume nitro pipes . The bigger diffuser angle on the pipe pulled more fuel into Toms engines, (he did not even know this) that is just what was going on. Years later I was talking with Andy Brown (you had to know what to ask Andy to get him to talk) and he was running large ports with small pipes, mainly because even though the small volume pipe (low diffuser angle) has less pull on the engine coming off the power stroke , but it has a stronger return wave coming back to the engine. Large angle diffusers have more pull coming off power stroke but have a weaker return. I have read many books confirming what Andy was talking about, and have witnessed this at the boat pond myself. There is alot more to talk about on this subject, but this is a start. Pipes and their (angles) need to be discussed when talking about transfer and boost area. The cmb 101's were coming out with .585" wide transfers (almost 20 years before they were at least .635" wide) makes me shake my head about cmb being in left field. Ive ran transfers as wide as .750" on this engine and never even tried the stock transfers on the 101's because of this. There is alot all of us can talk about on this subject but like you mentioned Marty , all the ports transfer fuel and need to be looked at as the same when it come to flowing fuel. The cmb mod 80 evo style engine is one of 'the best that never was', it had a large boost and small transfer area. When this thread gets a little longer lets talk about how the bigger ports effect the pipe temperature and this is what really makes some differences.

 

[Tom Foley]

https://www.google.com/search?q=loop+scavenging&biw=1280&bih=565&tbm=isch&tbo=u&source=univ&sa=X&sqi=2&ved=0ahUKEwi68b2MjNfNAhVILyYKHWGSDyYQ7AkIKg

 

[Jim Allen]

Pictures of the actual MB 40 mold show the curved transfers & downward facing exhaust duct.

JA

 

[dwilfong]

Thanks for sharing Jeff,

Now where cooking with NITRO.....................................

So what do you think will work better for a heat racing eng.

Smaller ports and a higher angle diffuser on pipe?

Larger ports sallower diffuser angle on pipe?

Is the a rule of thumb as far as diffuser angle and port area?