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RE: Engine porting - 3/1/2007 5:33:27 AM   
Pro Twister Mods



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Status: offline 		yup, My team driver has a new Losi and it's equiped with a Pro Twister .21R. I'm running gas truck with a Pro Twister .12R. Stop buy and say hi, i would like to meet ya.

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       Post #: 101

RE: Engine porting - 7/5/2007 2:10:48 PM   
Jerseyboy



Posts: 206
Joined: 11/1/2006
From: SA Buggy Racer, SOUTH AFRICA
Status: offline 		Ive done quite a few engines. Mainly flowing the sleeve. The cranks were quite good so never touched the crank.
The only timing changes Ive done was raising the exhaust port by.5 or 1 mm. This took away some bottom end and better top end.

On My SH28 6P I raised the exhaust port and flowed the engine. This beast was just way too powerfull. It revved better but snapped the rod. This mill cannot take repeated high rpm, top heavy.



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       Post #: 102

RE: Engine porting - 7/5/2007 10:26:09 PM   
Colt4g63


 

Posts: 230
Joined: 4/30/2005
From: New Albany, IN, USA
Status: offline 		Ahhh all the timing and porting advice ive gave to my good buddy supertib and he doesnt even mention me LOL. Its ok buddy i forgive ya. But i may have to charge u now to use my X-Dyno!! J/J

This engine moding thing is a huge learning experience! Ive been doin it for years and i still learn more and improve my engines all the time. And theres nothing more satisfying then watching an engine u modified improve before your eyes. It still to this day gives me that rush So for u guys that are wanting to learn how to port your own engines with great results dont give up. It takes a long time to really get to know these engines, but in the end it is VERY rewarding!

< Message edited by Colt4g63 -- 7/5/2007 10:34:46 PM >

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       Post #: 103

RE: Engine porting - 7/6/2007 2:39:19 AM   
SAVAGEJIM



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quote:

ORIGINAL: Jerseyboy

Ive done quite a few engines. Mainly flowing the sleeve. The cranks were quite good so never touched the crank.
The only timing changes Ive done was raising the exhaust port by.5 or 1 mm. This took away some bottom end and better top end.

On My SH28 6P I raised the exhaust port and flowed the engine. This beast was just way too powerfull. It revved better but snapped the rod. This mill cannot take repeated high rpm, top heavy.




So after you cut the ports up, what were the final timing profiles of these engines you modded?
Crank induction duration?
Lateral intake port durations?
Boost port duration?
Exhuast port duration?
How many degrees after TDC does the induction port open after TDC?

I too am still learning about engine modding and am trying to learn as many timing profiles as possible to determine what each profile does as far as low RPM performance, mid-RPM performance, and high RPM performance.


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       Post #: 104

RE: Engine porting - 7/6/2007 6:48:11 AM   
Jerseyboy



Posts: 206
Joined: 11/1/2006
From: SA Buggy Racer, SOUTH AFRICA
Status: offline 		Up until this point I have not radically changed the timing of an engine. I mostly flow the sleeve and wont change the timing profile as that is the characteristics of the engine. I do not want to change that. By lifting the exhaust port I am only moving the power band ex let say the power band was 7000rpm to 34000rpm, it will be 9000rpm to 36000 rpm.
I recently changed the this on my P5X.
The engine had just rediculopusly too much bottom end. Now I find good bottom with a phenomenal midrange and very good top end.

Everyone modifies in their own way. I only mod for more overall power and economy, maybe if it needs better top end.

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       Post #: 105

RE: Engine porting - 7/6/2007 1:57:39 PM   
SAVAGEJIM



Posts: 4315
Joined: 7/6/2005
From: behind my 'puter, USA
Status: offline 		On the past few engines I modded, most recently, 2 Axial .28 Spec1 RRs, I did not alter the timing profiles. I did entirely sleeve work and did flow mods and touch-up work on my RR sleeves. In particular, I matched the exhaust port of the sleeve to the exhaust port of the block. From looking through the back nozzle, an unaltered sleeve is poorly matched to the block port; you can literally see a whole ot of brass sticking out where it should not be at all.

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       Post #: 106

RE: Engine porting - 1/17/2008 3:12:48 AM   
ruch1


 

Posts: 3
Joined: 1/11/2008
From: stillwater, OK, USA
Status: offline 		Interesting subject,I'm new to this forum, but may open a new can of worms,I build motorcycle dragrace engines, from complete cylinder heads ,extensive porting,flow testing, seat and guide installation serdi valve jobs etc.4- cycle but anyway ,Knowing what I know about piston port 2-cycle engines ,I have a question? When you mill a cylinder head to make the combustion chamber smaller you raise C.R (compression ratio),correct? when you remove material from a cylinderhead chamber it increases c.c's lowering C.R correct? Then what happens when you remove a moderate amount of material from the lower end,Crankshaft, cylinder sleeve, cases piston skirt,etc. ? My point being, My take on piston port 2-cycle engines whether it's nitro or gas, Their are primary and secondary compressions going on ,again I am just asking a question , and not trying to stir the pot, actually it's a three stroke, think about it,When the piston travel's upward and the crank window opens and its drawing in fresh fuel charge on the compression stroke , when the fuel ignites driving the piston down on the power stroke it also exausts and uncovers the transfers to allow the fresh charge into the c.c (Combustion chamber) from the crank case performing three actions in one revolution , so my question being ,By removing material from the lower end any at all seems to me it would make the secondary compression lazier on discharge through the transfers, in other words would compromise velocity, and make charge motion slooooower, and yes I know there are many variables, maybe these engines are allready to small in the lower half , where is the ellusive balance,Just My 2 cents. Thank's Mike R.

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       Post #: 107

RE: Engine porting - 1/17/2008 8:00:36 AM   
proptop



Posts: 4447
Joined: 10/18/2002
From: Rome, NY, USA
Status: offline 		Mike...that's exactly right...removing material anywhere inside the case will effectively lower base compression, so you have to tread lightly.

When I mod a sleeve for example, I basically just radius the sharp edges in the fuel/air mixture's flow path. When I do a crank, I'll bell mouth the opening of the induction passage where it opens into the case, and polish the passageway if necessary...and sometimes add silicone in the area immediately under the carb. I will add here though that I don't race, and just do my own mods for bashing, so I'm not looking to get the max out of any one particular engine, but basically to improve efficiency somewhat.

If you go and remove a lot of material from the crank, sleeve, case, etc. and increase the internal volume by a substantial percentage, that will lower the flow velocity, soften the bottom end torque, and you'll need to work the ports and timing for top end power to get something back, or you'll end up with a doggy, less powerful engine than you started with.

< Message edited by proptop -- 1/17/2008 8:12:37 AM >

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RE: Engine porting - 1/18/2008 8:48:44 PM   
supertib


 

Posts: 3308
Joined: 3/30/2004
From: , MB, CANADA
Status: online 		here is a modded Jammin JPX .21 that I just completed..... this work is done 100% by hand using the files in the pictures.the rough surface is deliberate, I usually will polish up a sleeve for taking pictures, but I am lazy today..... so this is how i would run the sleeve in my motor......this is a fully altered motor with pretty extensive port modifications.... Notice how the exhaust port lining is brass not chrome ?



< Message edited by supertib -- 1/25/2008 12:32:17 AM >

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RE: Engine porting - 1/18/2008 9:08:25 PM   
JB COMP



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Joined: 11/23/2006
From: Navarre, FL, USA
Status: offline 		nice job supertib.

did you change the intake timing? because it dosen't look like it.

can you give me a link to where you got those files? I found some but there not that small, and there not diamond files.

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RE: Engine porting - 1/18/2008 9:12:21 PM   
supertib


 

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quote:

ORIGINAL: JB COMP

nice job supertib.

did you change the intake timing? because it dosen't look like it.

can you give me a link to where you got those files? I found some but there not that small, and there not diamond files.



the intake timing is altered slightly ( I still have a little more work to do yet FYI) ...notice the front corners of the transfer ports ?

unfortunately you will likely never find these exact files, as they are only available locally to me in a very limited supply.. I would very much love to find a more available source of these fantastic little files ........ Be warned using these files to alter ports takes an extremely long time and also it can be extremely difficult to cut cleanly... The chrome is very tough and very difficult to remove nicely., you will likely mess up several sleeves before you get the feel of the metals......

< Message edited by supertib -- 1/18/2008 9:16:03 PM >

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RE: Engine porting - 1/18/2008 9:45:28 PM   
JB COMP



Posts: 4029
Joined: 11/23/2006
From: Navarre, FL, USA
Status: offline 		I did see the corners, but I didn't think that was veary much. my files are normal and there about 8" long, I think they will work but the chrome is harder than the brass. I got a old sleeve to work on then the hyper 21 8-port before I start on any good engines.


how about these http://item.express.ebay.com/5-Mini-Diamond-Files-for-Lapidary-Tools_W0QQitemZ160199484924QQihZ006QQcmdZExpressItem

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RE: Engine porting - 1/18/2008 9:46:51 PM   
supertib


 

Posts: 3308
Joined: 3/30/2004
From: , MB, CANADA
Status: online
quote:

ORIGINAL: JB COMP

I did see the corners, but I didn't think that was veary much. my files are normal and there about 8" long, I think they will work but the chrome is harder than the brass. I got a old sleeve to work on then the hyper 21 8-port before I start on any good engines.


how about these http://item.express.ebay.com/5-Mini-Diamond-Files-for-Lapidary-Tools_W0QQitemZ160199484924QQihZ006QQcmdZExpressItem



those will work......... regular files will never cut the chrome...they need to be diamond files.

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RE: Engine porting - 1/18/2008 9:54:54 PM   
JB COMP



Posts: 4029
Joined: 11/23/2006
From: Navarre, FL, USA
Status: offline 		I'll try to talk my Mom into ordering those for me

I want to start, but I need to finish my other project first. oh, you should have got an e-mail with pictures.

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       Post #: 114

RE: Engine porting - 1/18/2008 10:26:47 PM