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Old 10-01-2005, 09:06 AM   #31
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Quote:
Originally Posted by Top Gun 777
As I sad before-later closing defenetly helps on top RPMs, but earlier opening is not quiete work like that. There is combination of exhuast timing and induction which shifting power band. Higher exhaust-less dwelf time when combustion pressure push piston down-less torq ( this is general rull). So balance between opening-closing-exhaust is shifting power band.
But again, just timing will not make engine run as fast as possible. Piston/liner assembly makes a lot of inturation (mechanical friction due to the slikines of piston material, tapering on sleeve which create extra friction etc) and here is another art to find best set up. I know that not many people can make their own piston/liner set (actualy it is only one guy can in the world), but defenetly there is big potential baried and our chalange is to bring everything to surface.
Edward
Thanks Edward,

lately I really get the hang of it with my restricted resources...
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Old 10-01-2005, 05:34 PM   #32
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Originally Posted by Top Gun 777
Polishing doesn't worth a thing, just waist of time!!!
With Brian Kinney from Xdyno we did some test and max RPM and HP we got from motor which was plain from cutting tools, no polishing no massaging and it was 45 K with .92 HP on his certifyed dyno ( just for comparicing RB 5 ports Rody modded 43K and .9 HP). No cuts on sleeve, no turbo scoop, but big chamfer on exit of center hole, basecaly its look like stock engine but with my P/L set and my cranck.
Edward
its not just polished come on open eyes they set timing and ported and balance the engine the polishing is just a bonus
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Old 10-01-2005, 05:59 PM   #33
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Polishing doesn't worth a thing, just waist of time!!!
Ed on this point I have to disagree with you. Polishing the OD of the crank reduces friction through the case tunnel. Polishing the pin before the first run in greatly reduces crank pin wearover the life of the motor. And polishing the crank tunnel can be usefull if you want to use the rotational centrifical force of the crank for improved distribution.(not flow) If you just want to drag air through a hole at the lowest restance then polishing the tunnel is not what you want to do.
PS whats new dude. Long time no talk.

Opinion: After 30 years of modifying engines I have this advice. You need to ask yourself why you are doing what you are doing. After you've asked yourself that question and you have a justifyable engineering reason for doing it then and only then should you do it. Otherwise its just hacking and whacking. This is what seperates the pro tuners from the rest. A pro tuner can tell you exactly why he does what he does and can back it up with theoretical physics. as far as balancing goes there are very few who understand how to go about it properly, and those who know literally won't discuss it in more than generalities. The same goes for overall transfer timing interaction and piston speed based on stroke. (one of the most critical things in the engine next to the tuned pipe)

One last comment from somone who has been doing it a very long time and I am sure ED and Uriah will agree. Everytime you think you know what you know somthing comes along and blows your theory all to hell! If you have not experienced this you haven't been doing it long enough.
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Old 10-01-2005, 07:59 PM   #34
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Hey Dennis!!! How is going man? Haven't seen you, but honestly was expecting you come to RD logics race and was pretty disappointed to find out that you are not comming.
Listen, about flow theories-there is too many of them and we are stays with ours-there is no laminar flow at velicity we have in cranck tunnel, so clean machine cut surface more then enough to support uninterupted flow, but again-it is our theory. I wouldn't spend my time to polish that tunnel.
The rest you are absolutly right and nothing further I will have to add.
Edward
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Old 10-01-2005, 08:11 PM   #35
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Quote:
Originally Posted by mgtman
its not just polished come on open eyes they set timing and ported and balance the engine the polishing is just a bonus
You got me wrong, I just sad somewhere above-I am not discusing anybody work here. I just put my knowlodge and expirience.
About open my eyes-I can see better then you can imaging when we are talking about engines. I am in this hobby (nitro engines) since 1975 and 1977 I have made my first own engine, not modded, not polished, made from scratch. BTW, just look our web site and you will understand that if I sad something about engines- I know exactly what I am talking about. I do not modufy engines, I do not masage them-I build them! Since I am here in Rc cars I used orginal P/L set in motor just ones within 2 weeks, since that I am using only my own built stuff, verry succesfully! Who else in the world can say the same words? So I can see almost everything about engines with closed eyes.
Best regards
Edward
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Old 10-03-2005, 11:43 AM   #36
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Stephan,

Try using the postitive stop method when trying to determine exact BDC. I made a stop using an old glow plug and a long bolt, rounded at the end. I place the degree wheel on the crank, and eyeball it to BDC. Then insert the stop so the piston hits it around 30 ABDC. Write this down, Then go back to BBDC and read the degrees from pointer, Write this down. (this figure might be 35deg or 25deg, doesn't matter) Now add the two figures together and divide by two. This will be the point where your pointer should be for absolute BDC.

Example:

Set pointer at 0 deg BDC and tighten degree wheel to crank.
Adjust pointer close to 0
Install positive stop and set it to 30 DEG BBDC or TDC for that matter.
Rotate engine one way and measure deg. =31deg
Rotate engine Other way and measure deg. =27deg
31+27/2=29 Original setting was 30deg. 30-29=1deg.
Now adjust your pointer 1deg by bending your pointer, and remeasure

When you get 39ABDC and 39 BBDC or 30 ABDC and 30BBDC or whatever then you know you are dead nuts at 0BDC.

I hope this helps, and I hope I havent confused anyone!
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