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Old 08-07-2009, 12:06 PM   #1
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Questions?? Cylinder Modifications for power increase

Has anyone had success in enlarging the intake or exhaust ports to increase the power output. I bought an OS .12TG engine to experiment with. I have a OS .12XZ Power house engine, and I'm going to use it as a guide to modify the intake and exhaust, and possibly increase to air opening on the carb from 5.0 to 6.5 as it is in the 12XZ.

Anyone's help would be useful.


Thanks
Matthew
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Old 08-07-2009, 12:22 PM   #2
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Easy there!

The carbs throat or "runner" has a specific shape, length, diameter, etc. it's a venturi shape, that is responsible of pulling the fuel out of the needle/jet as air flows through it, if you just bore it out you'll have your share of problems at least from low to mid range.

You can obtain a fair amount of power just by timming the engine just like the XZ. Other than that you need to balance the crank, work up the squish band, do the usual reciprocating lightening and the all important flow mod.

BUT - if its your first time,and if its a new engine, do an old one fisrt for practice!!, I've seen many people wreck new engines and turn them into trash. Im not saying dont do it, go a head do your thing and learn your stuff thats prety cool, but dont youst throw away $150, before you do, get an old, working!, $40 used engine and do some port testing a bit at a time and see results. THEN wreck your new one with no excuses!!!

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Old 08-07-2009, 12:45 PM   #3
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http://www.rctech.net/forum/exclusiv...o-engines.html
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Old 08-07-2009, 03:00 PM   #4
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look at this to http://www.rctech.net/forum/nitro-ro...ro-engine.html
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Old 08-07-2009, 03:15 PM   #5
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Default Thanks - but further questions

Roelof,

Thank for the link to you description of tuning, timing etc.
I was not aware of the carb opening restriction. All things being equal, if I am successful at modifying the ports with side to side enlargements, and I need aa bigger carb, I could purchase one.

"Changing crankshaft timing can do a lot to get more power or more rpm, it can only be done by grinding", ,

In your link - could you explain the above quote from your post in a little more detail?

Also, the 12XZ I mentioned earlier - is a SOB to start with an OFNA box and 12v 7a battery. Its in my sprint car from Custom Works (Sprint Car) and the flywheel is very narrow and does not have sharp teeth. It either stalls the starter of just grinds away the wheel. The engine is stock, no mods at all. but at the top of the stroke with the head off it pushes the cylinder right out and you can hardly force it down. Any ideas how I can start this beast any easier? I ran the engine on a drill for hours using two cycle engine oil to lube it. It did free it up quite a bit but with compression added its still a bear to turn over. The first time I started it, the glow plug was loose so it would just turn over. Need some help here!!!!!!!!!

Thanks for your help, both of you!
Matthew
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Old 08-07-2009, 06:00 PM   #6
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The tightness is normal for new high performance engines. They need a long break-in to loosen them up. Try heating the motor with a heat gun before starting and get a stronger box.
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Old 08-08-2009, 03:04 AM   #7
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Quote:
Originally Posted by MSmitty View Post
Roelof,

"Changing crankshaft timing can do a lot to get more power or more rpm, it can only be done by grinding", ,

In your link - could you explain the above quote from your post in a little more detail?
It is written in that topic with a drawing.

And indeed an easier start is made with pre-heating the engine and/or loosen the glowplug.
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Old 08-08-2009, 08:16 AM   #8
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Timming is what the camshaft is in a full scale car. It is the "moment" that the crankshaft intake valve opens and closes in relation to piston position and the "moment" that sleeve ports open and close in relation to crankshaft position. It can make your engine pretty damn fast, it can make it worth crap too.

You can probably do that 0.15~0.25mm cut in your tg's crank with only gains, the tg is fairly tame to start.
Yes you can get the bigger carb but here's rule of thumb, more than 5.5 is for bashing, more than 6 is for drag racing.
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Old 08-09-2009, 02:17 PM   #9
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Default Stroner Starter Box?

Roelof,

You mentioned a stronger stater box - What do you recommend.

Also my statement on enlarging the Carb was misstated. I know what you're talking about. And cannot describe what I was talking about in a few words. I do understand what you're saying, I just didn't state it right.
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Old 08-09-2009, 02:23 PM   #10
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Talking Great little .12 engines

What engines can you recommend for future purchase. I'm into On-Road and Sprint Cars

I'm 51, retired and disabled and I'm not worried about spending money on my Hobby. Let face it, there are far more expensive hobbies.
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Old 08-09-2009, 02:30 PM   #11
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I really like my Mugen starter box. Not many motors are tight enough to lock up on that thing, though some still will.

For dirt oval racing, the Piccos are great. Cheap and smooth power. For all out. tire spinning rip Novarossi is the way to go.
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Old 08-09-2009, 02:36 PM   #12
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Lightbulb Which box is it?

[QUOTE=wingracer;6181465]I really like my Mugen starter box. Not many motors are tight enough to lock up on that thing, though some still will.

Is it the Mugen Pro Starter RII w/ Two prewired 540 size motors
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Old 08-09-2009, 02:52 PM   #13
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I believe the TM starterboxes have 550 motors. If your current box has 2 standard 540 motors you can get som 21 or 23 turns rebuildable (V2) motors, much power and less maintenance, I also have 23 turns motors.

I hope one day a manufacturer will show up with an electronic box to mount brushless motors in a starterbox.

Regarding motors... If anything is alowed, get an OS 18TZ
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Old 08-09-2009, 03:31 PM   #14
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Yep, don't let that box fool you. It has lots of rip.
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Old 08-13-2009, 10:15 PM   #15
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regarding liner mods, what happen if i only smooth the boost ports entry with lower angle and the bottom liner? just wanted to know the effects on performance and tuning wise..

thanks in advance
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