Mastermind Meets The MS661 Again

[KG441c]

I feel like velocity is very important.......but that's just my gut feeling.

So hogging out the transfers would decrease velocity and crankcase compression?

 

[KG441c]

UPS just came!!!

 

[Trx250r180]

Will you make me a 661-461 hybrid ,that 661 top looks like will fit my 461 cases

 

[MustangMike]

Someone please correct me if I'm wrong, but I think on the new saws they are paying a lot of attention to the angle the transfers go into the combustion chamber in order to maximize the amount of air/fuel that stays in the chamber and maximize the exhaust being expended.

Almost like the research that GM did to get a 2 Valve pushrod engine to produce the power and reduced emissions comparable to multi valve overhead cam motors.

 

[singinwoodwackr]

Not with any reasonably affordable machines.

The one we have here at work can print ABS, and I think perhaps nylon with an additional bed adapter. Nylon might be suitable.

I think an insert could be retained by drilling a hole in the insert spout, and running a countersunk screw in from the outside. That way the screw could not enter the intake even if it came loose. Maybe the insert could be formed so as to hook over the intake inlet spout? I don't know what the boot looks like, but it probably fits too closely for that.

Overall a pre-made insert would be a challenge on a port that had been modified, as the shape would have to match very closely. It might be viable on a stock port. Even with a stock port, drawing it would be fun, as it is an obscure shape. I suspect filling it with epoxy and grinding it down would be the best process for low volume mods, but even that is a PITA..

yea, not even close to being cost effective...yet. The vid about making the 1911s was still pretty cool to watch. The technology is starting to remind me of Star Trek's 'processors'

https://blog.solidconcepts.com/evolution-custom-manufacturing/how-its-made-3d-printed-1911-pistol/

 

[fordf150]

hogging out the transfers slows the flow of fuel/ air. higher velocity will lead to a scavenging affect that will continue to pull air/fuel in even after the pressure differential has changed. less is sometimes more in the world of flow.

 

[Ron660]

No Andrew, one is with unfinished Devcon, the next is after finishing, then next is a stock port.

The factory port ends up at 85* after machine work. That's not crazy low on a 90cc saw, but I would like to be able to cut more from the squish to get the compression a little higher. At 85*, that's as far as I will lower the jug.

Even then I can't raise the transfers quite as high as I'd like to.

So, I'm at 102/122/85 on the two jugs without epoxy.

The jug with epoxy in the intake is at 100/120/80.

Randy, I know how to fix that. Put a 660 cylinder on it! 661/660 Hybrid and add bridges between the transfers.....quad port....lol.

 

[User Name Here]

Im certainly no expert but i would imagine that would be a step backwards in technology and drop off in power from the stock 661

 

[MustangMike]

I'm sure it is not compatible. Quad, instead of dual, transfers.

 

[KG441c]

Wonder if the 461 crankcase will mate to the 661

 

[Ron660]

Im certainly no expert but i would imagine that would be a step backwards in technology and drop off in power from the stock 661

I was joking but I'm sure the 660 jug is a lot easier to get the timing numbers right.

 

[User Name Here]

I was joking but I'm sure the 660 jug is a lot easier to get the timing numbers right.

I'm picking up what you're putting down. I guess I missed the context. Sorry about that

 

[tree monkey]

Randy, I know how to fix that. Put a 660 cylinder on it! 661/660 Hybrid and add bridges between the transfers.....quad port....lol.

I did just that

 

[Ron660]

I did just that
[/QU
I knew it would work!

 

[LegDeLimber]

https://en.wikipedia.org/wiki/Flow_conditioning

 

[KG441c]

https://en.wikipedia.org/wiki/Flow_conditioning

Wow!! Alot of information!! Thanks. What I can gather from all that was the smoothest entry into transfers as possible is needed, least restrictive flow characteristics with velocity taken into consideration, and finally an exit toward the right directions in the combustion chamber would be ideal? Figured Id ask Randy about these ideas in my head and Randys statement that He and Wiggs have talked countless hrs about these saws and the chatacteristics that usually apply to longer stroked motors just dont apply here. I tend to believe Randys theory on 87 octane fuel in these short stroke motors vs longer stroked. Im interested to see what he comes up with on this 661 and if succesful just maybe he might share a few of thoso out of the box discoveries that are successful with us. Thats why I joined AS and everyone here has been helpful and I have bugged Randy days upon end with questions and he has always been there to help. Thanks everyone

 

[MustangMike]

Keith, be careful with "too smooth", you need turbulence on the intake. Part of what GM did to achieve dramatic results in a traditional design engine in both performance and reduced emissions was to ensure the air/fuel mix was uniform across the entire combustion chamber. That required some built in turbulence.

 

[old-cat]

Keith, be careful with "too smooth", you need turbulence on the intake. Part of what GM did to achieve dramatic results in a traditional design engine in both performance and reduced emissions was to ensure the air/fuel mix was uniform across the entire combustion chamber. That required some built in turbulence.

Well, I'm sorry Mike but you're getting stuff mixed up. Turbulence in the cylinder is good but turbulence in the intake reduces flow.

 

[MustangMike]

Well, I'm sorry Mike but you're getting stuff mixed up. Turbulence in the cylinder is good but turbulence in the intake reduces flow.

Technically I agree with you, but I do not think you will achieve the the turbulence needed in the combustion chamber without some degree of turbulence in the transfer port. And yes, it is a balancing act, as turbulence will reduce flow.

It is also interesting to note that a dimpled golf ball will travel further than a smooth round one.

If you look at what the GM engineers did, it involved the intake manifold runner, the port into the head, and the combustion chamber design. I wish we had the type of testing equipment and expertise that they have to achieve similar results, but the bottom line is they must all work well together.

 

[KG441c]

Well, I'm sorry Mike but you're getting stuff mixed up. Turbulence in the cylinder is good but turbulence in the intake reduces flow.

Oldcat would u mind explaining turbulance inside the cylinder?