Engine Mods
02-06-2004, 10:28 AM
#136
Originally posted by afm
In general terms, what performance change do you enhance if you increase induction by advancing opening or retarding closing of the crank opening.
I.E. advancing opening = more torque
retarding closing = more top end
Or is it the opposite.
Same way with transfer ports, what effect does it have to rise the port or lower it.
AFM
In general terms, what performance change do you enhance if you increase induction by advancing opening or retarding closing of the crank opening.
I.E. advancing opening = more torque
retarding closing = more top end
Or is it the opposite.
Same way with transfer ports, what effect does it have to rise the port or lower it.
AFM
Transfer port has to be at certain opening, to have enoough time to transfer all mixture to combustion chamber. Exhaust opening is more complecated. lower exhasut-longer dwelf time-more torq, higher exhaust-smaller dwelf time, less torq, bu higher RPM. Also difference between exhaust and transfer will dictate your pipe performance. There were alot of studies done to find the best suitble difference and so far is about 40 degree. In our aplication little bit different due to our pipe design ( two cycle).
\ Got go, will be later.
Didn't finish.
02-06-2004, 10:34 AM
#137
I got question. Don't touch botom of ther port-it changes nothing. If you want to change timing just cut the top line of sleeve.
02-06-2004, 12:46 PM
#138
Originally posted by Top Gun 777
It is about right, but you have to remember of resonable limits and balance, meaning if you keep opening to any of the ways trying to achive one of the parameters and cross the limit line.........engine will just stop to perform at all.
Transfer ports have to be at certain opening, to have enough time to transfer all mixture to combustion chamber.
Exhaust opening is more complicated.
-Lower exhasut-longer dwel time-more torq,
-Higher exhaust-smaller dwel time, less torq, but higher RPM.
Also difference between exhaust and transfer will dictate your pipe performance. There were a lot of studies done to find the best suitable difference and so far it is about 40 degrees.
In our aplication a little bit different due to our pipe design ( two cycle).
\ Got to go, will be late.
Didn't finish.
It is about right, but you have to remember of resonable limits and balance, meaning if you keep opening to any of the ways trying to achive one of the parameters and cross the limit line.........engine will just stop to perform at all.
Transfer ports have to be at certain opening, to have enough time to transfer all mixture to combustion chamber.
Exhaust opening is more complicated.
-Lower exhasut-longer dwel time-more torq,
-Higher exhaust-smaller dwel time, less torq, but higher RPM.
Also difference between exhaust and transfer will dictate your pipe performance. There were a lot of studies done to find the best suitable difference and so far it is about 40 degrees.
In our aplication a little bit different due to our pipe design ( two cycle).
\ Got to go, will be late.
Didn't finish.
AFM
02-06-2004, 01:08 PM
#139
Originally posted by Top Gun 777
I do very steep taper there, right under the exhaust port. It is free up piston. Under the exhaust port we don't need any sealing, so the more we take out-less friction we have there. It is only guyding piston to go straight. Sorry can't release phisical numbers-this is one of the numbers can be disclose.
You need to try, lap it little by little and will see the difference, once you got overlaped-you will notice the piston will hit top line of exhaust port on sleeve. When you got to that point, just mesure it and do little bit less.
I do very steep taper there, right under the exhaust port. It is free up piston. Under the exhaust port we don't need any sealing, so the more we take out-less friction we have there. It is only guyding piston to go straight. Sorry can't release phisical numbers-this is one of the numbers can be disclose.
You need to try, lap it little by little and will see the difference, once you got overlaped-you will notice the piston will hit top line of exhaust port on sleeve. When you got to that point, just mesure it and do little bit less.
02-06-2004, 01:18 PM
#140
Originally posted by rskoncepts
Top Gun 777...can you explain that a little more. I taper the bottom of the exhaust port but not sure if you mean the same. Do you have pictures or drawing to illustrate that? Thanks
Top Gun 777...can you explain that a little more. I taper the bottom of the exhaust port but not sure if you mean the same. Do you have pictures or drawing to illustrate that? Thanks
i don't have saner to make pics of drawing, but will try find one, after winter nats.
02-06-2004, 01:26 PM
#141
Originally posted by Top Gun 777
In my post I was meaning to make bigger taper in diameter of sleeve, not the exhaust port it self.
i don't have saner to make pics of drawing, but will try find one, after winter nats.
In my post I was meaning to make bigger taper in diameter of sleeve, not the exhaust port it self.
i don't have saner to make pics of drawing, but will try find one, after winter nats.
02-15-2004, 08:40 AM
#142
If also you will use my P/S/conrod set you will see even a lot of more difference.
later
02-15-2004, 09:21 PM
#143
Originally posted by rskoncepts
So you mean inside the sleeve so there is slight gap between the piston and the sleeve below the exhaust port?
So you mean inside the sleeve so there is slight gap between the piston and the sleeve below the exhaust port?
My P/S sets were use in Ft. Myers and you can check with Stefan abiout performance, he was the one of the racers who used. He loved it so much and reserved more from me.
02-15-2004, 09:23 PM
#144
Originally posted by Chewdogg
Hey TG do I buy the P/S/conrod set directly from you. I want to try one in my MR12(3 port) or my NS12 (5 port). PM me
later
Hey TG do I buy the P/S/conrod set directly from you. I want to try one in my MR12(3 port) or my NS12 (5 port). PM me
later
02-20-2004, 07:10 AM
#146
Hey guys,
I'm looking at the package of my mugen P/S set for my MR12. The package says MR RS NS RR...If these engines use the same sleeve what makes the power different?..Is is carb? crank?
I'm looking at the package of my mugen P/S set for my MR12. The package says MR RS NS RR...If these engines use the same sleeve what makes the power different?..Is is carb? crank?
02-20-2004, 07:38 AM
#147
Originally posted by Chewdogg
Hey guys,
I'm looking at the package of my mugen P/S set for my MR12. The package says MR RS NS RR...If these engines use the same sleeve what makes the power different?..Is is carb? crank?
Hey guys,
I'm looking at the package of my mugen P/S set for my MR12. The package says MR RS NS RR...If these engines use the same sleeve what makes the power different?..Is is carb? crank?
I had an experience rebuilding an RBX12 with a Novamega P/S set and tried it with RB's crank and the engine had more torque, when I tried it with the Novamega crank, the engine had more top end
AFM
02-22-2004, 05:40 PM
#148
Tech Adept
what are some good numbers for a 4 port .21 to achieve max lowend?
Last edited by Josh K.; 02-22-2004 at 10:36 PM.
02-22-2004, 10:12 PM
#149
Tech Adept
this is my first time playing with timing and below is the numbers from the pos 4 port HPI .21BB I'll be practicing on, I have 4 of these so I can do all the damage I want in the quest for knowledge 
• INDUCTION—open 35 degrees ABDC (above bottom dead center); close 41 degrees ATDC (at top dead center); duration 186 degrees.
• EXHAUST—open 81 degrees BBDC (below bottom dead center); close 81 degrees ABDC; duration 162 degrees.
• TRANSFERS—open 67 degrees BBDC; close 67 degrees ABDC; duration 134 degrees
so what way should I go for the HPI to get the most lowend while still giving a little more room on top?
I'm thinking of pushing the induction closing to 55 resulting in a 200 duration and opening the exhaust duration to 170.
Does that sound close?
• INDUCTION—open 35 degrees ABDC (above bottom dead center); close 41 degrees ATDC (at top dead center); duration 186 degrees.
• EXHAUST—open 81 degrees BBDC (below bottom dead center); close 81 degrees ABDC; duration 162 degrees.
• TRANSFERS—open 67 degrees BBDC; close 67 degrees ABDC; duration 134 degrees
so what way should I go for the HPI to get the most lowend while still giving a little more room on top?
I'm thinking of pushing the induction closing to 55 resulting in a 200 duration and opening the exhaust duration to 170.
Does that sound close?
Last edited by Josh K.; 02-22-2004 at 10:36 PM.
02-22-2004, 10:59 PM
#150
If you lengthen the exhaust duration you will lose torque and gain top end power. When I tried increasing the intake (sleeve)duration, like 8* or so, I thought it had more power everywhere. if your induction port opens sooner it shuld have more bottom end power, while if you grind on it to stay open longer it should have more top end power, I thought like a 210* duration was good. You can also change your combustion chamber's shape, the taper, band width, radius of the bend/angle, and can put some grooves in it to get the fuel/air to mix better and burn more powerful b/c the rich spots shouldn't be as bad. I have only ran .12 engines so the principles will be the same for .21's but the numbers might differ.