discussion of transfer, boost,exh ports,int/exh rotor timing...

[Michael Costanzo]

I wanted to keep the venturi shape of the induction passage way. I do not know if a larger case window would have improved the engines performance. No. there is no bushing of any type used with any bell valve.

JA

jim,was this set up your idea or did you just adapt it to your application?

 

[Jim Allen]

Michael,

The bell valve was invented in 1965 by an Austrian school teacher (Paul Bugl) who flew speed planes as a hobby. In 1968 engines were produced under the name of HP, which stood for High Precision Power Performance. I have one of the original engines (#456) with it's automatic fuel metering system on a barrel type carburetor & a ringed piston; still in the original box. Henry Nelson introduced me to the bell valve after I had completed the research work on the steel roller rods. He said I would be able to use this type of induction system because the steel roller rods could run on 6% oil without any failure problems.

JA

 

[Michael Costanzo]

Michael,

The bell valve was invented in 1965 by an Austrian school teacher (Paul Bugl} who flew speed planes as a hobby. In 1968 engines were produced under the name of HP, which stood for High Precision Power Performance. I have one of the original engines (#456) with it's automatic fuel metering system on a barrel type carburetor & a ringed piston; still in the original box. Henry Nelson introduced me to the bell valve after I had completed the research work on the steel roller rods. He said I would be able to use this type of induction system because the steel roller rods could run on 6% oil without any failure problems.

JA

thanks jim for showing that great piece of history,mike.

 

[brad nichols]

Did the HP engines have the bell valve??

Brad

 

[Jim Allen]

Did the HP engines have the bell valve??

Brad

Brad,

Yes. Notice how the carburetor & induction tract are in line with each other. The throttle linkage which controls both the fuel metering & the closing of the barrel carburetor at the same time is also unique.

JA

 

[Michael Costanzo]

Did the HP engines have the bell valve??

Brad

Brad,

Yes. Notice how the carburetor & induction tract are in line with each other. The throttle linkage which controls both the fuel metering & the closing of the barrel carburetor at the same time is also unique.

JA

it is amazing that this was thought of 40+ years ago! i wonder why this is not used today? too expensive and time comsuming to manufacture??

 

[Jim Allen]

"kind of interested in learning more about the boost and transfer ports.i see different manufactures like different #'s.why is this?also have read that some like the timing #'s the same between the 2 and some like the transfer higher,roof angles,wider and higher,etc."

Michael,

In the engines that I have built the main transfer ports were opened at 130* & the boost ports at 124*. The idea was to have the gasses from the mains collide in the middle of the bore (stop moving) & then have the boost gasses pass over the top to clean out any remaining exhaust gasses. The main transfer ports in these engines were flat on top & the boost ports were angled upward 55*. Things such as radial angles. axial angles, bore size, cylinder wall thickness, transfer shape & volume must be considered. The drawings show some of the different radial & axial angles tested as well as diffenent exhaust shapes & angles.

Jim Allen

 

[Michael Costanzo]

"kind of interested in learning more about the boost and transfer ports.i see different manufactures like different #'s.why is this?also have read that some like the timing #'s the same between the 2 and some like the transfer higher,roof angles,wider and higher,etc."

Michael,

In the engines that I have built the main transfer ports were opened at 130* & the boost ports at 124*. The idea was to have the gasses from the mains collide in the middle of the bore (stop moving) & then have the boost gasses pass over the top to clean out any remaining exhaust gasses. The main transfer ports in these engines were flat on top & the boost ports were angled upward 55*. Things such as radial angles. axial angles, bore size, cylinder wall thickness, transfer shape & volume must be considered. The drawings show some of the different radial & axial angles tested as well as diffenent exhaust shapes & angles.

Jim Allen

jim,thank you for the explanation of why the main transfer's were opened at a certain # and then the boost.that's what i was trying to understand.i see a lot on my modified (JP Racing, Muran, Collarri) On-road car engines .12 & .21 size that they try to squeeze many transfer ports or stacking one on top of the other (with a little liner material in between),any thoughts on why this is done? mike.

 

[dwilfong]

opening the transfers first will decrees the velocity of the charge in to the cylinder. The compression caused by the piston moving down has only so much volume. opening the largest port first is not the way to go. open the boost first this way the charge is faster moving to the top of the cylinder. this way you take advantage of the plus from the piston better to scavenge the cylinder best. If you get things moving in the right direction first with a high velocity flow path Inertia will take over.

try blowing a pile of leaves with a blower buy sticking it in the big pile. Then drop the pile on the steam of the blower . see how many leaves blow and how far?

Get the air moving up then drop the transfers in . strait in and have them collide in the center.

This also lets you open the intake at BDC and gain timed area with out loss of velocity of the charge by trying to move a large mass first.

 

[Jim Allen]

I think there is a great deal of difference between blowing leaves with a leaf blower & gases traveling at the speed of Mach 1. Many high performance speed engines such as the Nelson Q-40 & the MB-40 open their main transfers first. What is important is that the main transfers be exactly the same on both sides of the cylinder! Some may be angled upwards slightly (15*), others may have no upward angle, but both types will have radial angles that are different on the leading & trailing edges of the windows. This is why a very thin walled cylinder will have very little effect on the direction of where the incoming charges should be directed. Differences in the radial & axial angles of the main transfers will cause unwanted turbulence when the two charges attempt to meet each other.

Jim Allen

 

[LohringMiller]

The state of the art is probably the Aprilia 125 cc engine. However, we found an interesting result when testing the CMB 35. Angled cuts on the second cylinder pictured like some of the car engines run helped power. I think that's because the cuts direct flow up and deflect the boost port flow away from the exhaust.

Lohring Miller

 

[Jim Allen]

Latter this week I'll take some better pictures of the transfers used in the MB-40 engines. They make use of the COANDA effect & are similar to the transfers used in the Aprillia 125 cc & Quick Draw Pioneer engines. The MB-40 engines also use a domed piston crown which helps to control the direction of the incoming charge when the incomng charge attaches itself to the piston crown as the main transfers open. This is another reason why the main transfers should open before the boost ports. This also helps to cool the piston's crown which is exposed to the heat of combustion.

JA

 

[dwilfong]

How many "Modern" car or boat RC eng opens the transfer first?

Funny the Mercury out board engs I and messing with now also open the transfers first. That is the way every one ports them.

Not me I pop the boost first then the secondary boost then the transfers. Run high timing # just like the RC boat engs do.

Every one said it will not work it will have no bottom end power and never rev up.

WELL WRONG ANSWER.............................It worked killer............................F up a few minds with that one.

Works killer in are RC boat eng also.

Lohring you boost stopper cut as I call it gave me great info and I use it in ever eng I do. IT WORKS >>>>>>>>>>>>>>>>>>

Almost every modern RC nitro eng uses it in one form or and other. Thy also pop the boost first.

 

[David Ashcroft]

Lohring looking at the picture of cylinders and the last cylinder has the arch cut under the boost.

My question is if too much is cut away what affect will that have ?

 

[Michael Costanzo]

this is a 4 port modded N/R .21 Off-Road Sleeve out of my buggy that i race. i had asked about "Stacked" Transfer Port and why they do it like this.

 

[dwilfong]

Mike thy do that to get flow under the piston to help cool it. It also helps the flow when the piston is at BDC. depends on the intake design if that makes a difference if you ask me. With a intake in the crank or the slant back rear intake it helps as the case is not set up for direct flow to the ports.

On a drum or disk I don't feel it dose any thing but mess up the flow path.

 

[Michael Costanzo]

Mike thy do that to get flow under the piston to help cool it. It also helps the flow when the piston is at BDC. depends on the intake design if that makes a difference if you ask me. With a intake in the crank or the slant back rear intake it helps as the case is not set up for direct flow to the ports.

On a drum or disk I don't feel it dose any thing but mess up the flow path.

yes, these car engine cases are angled back with the carb on top.what ever the good modder's are doing these engines spool up fast (also has putty in the ramps) and rpm to the moon!! that for the explanation,mike.

 

[LohringMiller]

this is a 4 port modded N/R .21 Off-Road Sleeve out of my buggy that i race. i had asked about "Stacked" Transfer Port and why they do it like this.

005.JPG

That cut was to remove the section of sleeve that blocked flow from the disk valve. To our surprise, it didn't make any difference in power. The same was true of most attempts to "streamline" the flow. Flat topped transfers seemed to give the best power, contrary to the results from most modern two strokes. That's because the poor tunnel shape results in a wide stream coming out of the port. Well shaped transfer tunnels aim the stream much better. A lot of the weird modifications seen on model engine sleeves won't be helpful with proper transfer tunnel shapes.

Lohring Miller

 

[Michael Costanzo]

this is a 4 port modded N/R .21 Off-Road Sleeve out of my buggy that i race. i had asked about "Stacked" Transfer Port and why they do it like this.

005.JPG

That cut was to remove the section of sleeve that blocked flow from the disk valve. To our surprise, it didn't make any difference in power. The same was true of most attempts to "streamline" the flow. Flat topped transfers seemed to give the best power, contrary to the results from most modern two strokes. That's because the poor tunnel shape results in a wide stream coming out of the port. Well shaped transfer tunnels aim the stream much better. A lot of the weird modifications seen on model engine sleeves won't be helpful with proper transfer tunnel shapes.

Lohring Miller

liners boost.JPG

i have owned a lot of on-road engines over the past 25 years and love to see what different guy's are doing and there are only a few that really know how to get it right. i had a 7 port that was modded by collarri and it was stupid fast! i a 1/8 on road car,it would spin the tires comming out of a corner and that was in a car that has LOTS of grip!! never seen anything like it. now for my boat engines,dave wilfong has done a bunch of motors for me in many different size for all type's of hull's and i am super happy with how well they run,not just really fast but great throttle response and the best part he has tought me a lot about 2 stroke motors..wish i knew him 25 years ago,guy's in NAMBA D1 would have really been in deep poop...

PS loring,you mentioned disc flow,the car motors are all .12/.21 with crank induction,mike.

 

[Michael Costanzo]

any info for as to (rotor) or induction open and closing points? too far or not enough in both direction what happens??