R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Nitro Off-Road

Reply
 
Thread Tools Search this Thread
Old 06-30-2008, 07:04 AM   #1
Tech Apprentice
 
Join Date: Jun 2008
Posts: 94
Trader Rating: 2 (100%+)
Default inside pic's of 3port rb i modded

Ok I have posted these same pic's on another forum and got some info but still looking a little more. So here it is to get some of you guys thoughts and maybe some of the guys that mod engines could weigh in. I am not asking for there secrets but to see what everyone thinks. Yes I know it is radical and I have been told you are not supposed to cut the trailing edge of the crank. I ramped down the trailing edge for a reason, to reduce turbulence. If you have ever followed an 18 wheeler pulling a box trailer down the road when it is raining the water in the air shows the air swirling as it comes off of the square box. So I tried it. As far opening up the crank inlet, I opened up the leading edge about a 1 mm smoothed out the inside of the crank barrel and opened it up also. On porting the sleeve I did not raise the port height on intake, I did open it some by bringing it down and opened the sleeve all the way to the bottom. This was to in able more air/fuel mix to pass between the block and sleeve to the port. On the exhaust port I matched the sleeve opening to the block opening. I am not a pro on RC engines I am not trying to learn how to do this so I can apply it on others engines, just my own. This engine screams and has done so for a gallon now of 30%. I don't know how many gallons it will last, but it is smooth and sounds great, I guess we will see. Looking forward to hearing from everyone, Thanks


http://i305.photobucket.com/albums/n...t/100_4331.jpg
http://i305.photobucket.com/albums/n...t/100_4330.jpg
http://i305.photobucket.com/albums/n...t/100_4329.jpg
http://i305.photobucket.com/albums/n...t/100_4327.jpg
http://i305.photobucket.com/albums/n...t/100_4326.jpg
http://i305.photobucket.com/albums/n...t/100_4324.jpg
mfroot is offline   Reply With Quote
Old 06-30-2008, 08:03 AM   #2
Tech Apprentice
 
Join Date: Jun 2008
Posts: 94
Trader Rating: 2 (100%+)
Default

Anyboby anything good bad?
mfroot is offline   Reply With Quote
Old 06-30-2008, 08:22 AM   #3
Tech Addict
 
desertbird's Avatar
 
Join Date: Apr 2008
Location: Surprise, AZ
Posts: 551
Trader Rating: 7 (100%+)
Default

I wish I could give you some feedback. I too am interested in tinkering with engine modding. I know it screams now, but what kind of improvements did you get with this?
desertbird is offline   Reply With Quote
Old 06-30-2008, 08:25 AM   #4
Tech Addict
 
Crim3Wav3's Avatar
 
Join Date: Dec 2005
Location: MasshoL3
Posts: 715
Trader Rating: 8 (100%+)
Default

I have a buddy at the track who has the RB S3 L2G, just started the break-in and it already seems to be a decent engine...for an INSANELY good price.

My question is what was your reasoning for attempting the mod? Were you not happy with some aspect of the engine in stock form? Were you just curious to see what you could do?

I am asking only to be insformed...

Oh, and my comment is: learn your camera's settings. I see a whole lot of red blamket and blurry engine internals.
Crim3Wav3 is offline   Reply With Quote
Old 06-30-2008, 08:36 AM   #5
Tech Addict
 
dieseldog20's Avatar
 
Join Date: Dec 2007
Location: RAF Mildenhall, United States Air Force
Posts: 572
Trader Rating: 2 (100%+)
Send a message via AIM to dieseldog20 Send a message via Yahoo to dieseldog20
Default

http://www.rctech.net/forum/showthre...ght=Powerhouse

check that forum out its about modding
dieseldog20 is offline   Reply With Quote
Old 06-30-2008, 08:52 AM   #6
Tech Regular
 
Join Date: Mar 2008
Posts: 367
Trader Rating: 12 (100%+)
Default

Im glad someone took the time to do some modding themselves and post a pic!

My question is about the turbo crank. When you cut the extra scallops in the counterwieght you obviously removed a decent amount of wieght. With that spinning at 30,000+ rpms wont that leave the internals very unballanced? I would think that would put a ton of extra stress on the rear bearing especially. Any ideas?
clarksib is offline   Reply With Quote
Old 06-30-2008, 08:56 AM   #7
Tech Apprentice
 
Join Date: Jun 2008
Posts: 94
Trader Rating: 2 (100%+)
Default

Ok I guess the reason I did it was for several reasons. The first being I own an ATV / Dirt bike repair shop, so I get paid to professionally modify 2 and 4 stroke engines. So I wanted to try my hand at moding one of these. The other reason I did it was my buddy runs a os 21 v spec and he was out running me and I did not like that. So now my l2g 3 port rb has no problem running with the v spec. Thanks for the questions.
mfroot is offline   Reply With Quote
Old 06-30-2008, 09:23 AM   #8
Tech Lord
 
wingracer's Avatar
 
Join Date: Nov 2007
Posts: 12,781
Trader Rating: 23 (100%+)
Default

No single cylinder engine is "balanced". All you can do is change the plane that the imbalance is in. In fact, you can't truly balance any engine with less then four cylinders.
__________________
Sean. Certified speed crazed mowron.
Team Shepherd USA
www.ashfordhobby.com
wingracer is offline   Reply With Quote
Old 06-30-2008, 09:31 AM   #9
Tech Master
 
Join Date: Jul 2007
Location: Planet Earth, 3rd Planet from the Sun
Posts: 1,119
Trader Rating: 38 (100%+)
Default

Modding is trial and error. I own and engine modding biz. We started out by modelling an OS V-Spec on high-end computers used in the Aerospace industry. But that was only part of it. Real-life testing was the next part. We learned alot...

Cutting the scoop will help some with packing. The flywheel (crank) is now lightened. Part of the affect of this is less low-end torque. If you are doing it to an engine like an RB, which IMO are already weak on the bottom it makes it more noticable... It will also spin more RPMs faster. We've seen con-rods go easily with this mod...

As you mod you may make the engine much for finicky when it comes to tuning. You make the tuning window much more narrow. Again, not good. There is a balance...

And as mentioned in one of the above posts, we is it you are looking to achieve? What is wrong with the current engine now that you don't like? Did you already try other methods to improve the performance such as different clutch shoes, pipe/header combos, plugs, shims?

Again, there is alot of work in modding an engine correctly. We've got a stack of destroyed motors from when we first started out...
__________________
JQ Products "Le Car" - 3 of them. Primary, back-up, and spares car
Bunch of "classic" Schumachers
Tamiya - Leopard 2A6, Tiger 1
HPI - Blitz
bushyar15 is offline   Reply With Quote
Old 06-30-2008, 02:42 PM   #10
Tech Apprentice
 
Join Date: Jun 2008
Posts: 94
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by bushyar15 View Post
Modding is trial and error. I own and engine modding biz. We started out by modelling an OS V-Spec on high-end computers used in the Aerospace industry. But that was only part of it. Real-life testing was the next part. We learned alot...

Cutting the scoop will help some with packing. The flywheel (crank) is now lightened. Part of the affect of this is less low-end torque. If you are doing it to an engine like an RB, which IMO are already weak on the bottom it makes it more noticable... It will also spin more RPMs faster. We've seen con-rods go easily with this mod...

As you mod you may make the engine much for finicky when it comes to tuning. You make the tuning window much more narrow. Again, not good. There is a balance...

And as mentioned in one of the above posts, we is it you are looking to achieve? What is wrong with the current engine now that you don't like? Did you already try other methods to improve the performance such as different clutch shoes, pipe/header combos, plugs, shims?

Again, there is alot of work in modding an engine correctly. We've got a stack of destroyed motors from when we first started out...
thanks for the reply far as being finicky this engine idles great and the tune does fluctuate. I don't have to touch needles temps are constant @ 260 to 270 and has been this way for a gallon of 30%. As far as it not having any bottom end, I am running a 13 tooth clutch bell with 3 aluminum shoes with stiff springs, so the engine is making good rpm's before it engages also a jp1 pipe. Like I said before one of the reasons I did this was to try something new. I have read before not to cut the trailing edge of the crank, but no one would say why, so what the h%*#. I figured I would cut it and figure out why I was not supposed to. Still have not figured out why. The other reason is like I have already said. My buddy runs an os vspec and I wanted to see if I could make this rb 3 port as fast as the v spec and I did.
mfroot is offline   Reply With Quote
Old 06-30-2008, 02:53 PM   #11
Tech Lord
 
wingracer's Avatar
 
Join Date: Nov 2007
Posts: 12,781
Trader Rating: 23 (100%+)
Default

I cut trailing edges all the time.

There is one part of the crank you didn't touch though. Think about it and break out the dremel again.
__________________
Sean. Certified speed crazed mowron.
Team Shepherd USA
www.ashfordhobby.com
wingracer is offline   Reply With Quote
Old 06-30-2008, 02:56 PM   #12
Tech Apprentice
 
Join Date: Jun 2008
Posts: 94
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by wingracer View Post
I cut trailing edges all the time.

There is one part of the crank you didn't touch though. Think about it and break out the dremel again.
OK OK OK you got me scratching my head tell me pm me post it i can't stand wanderring it might give me a head ache.
mfroot is offline   Reply With Quote
Old 06-30-2008, 07:20 PM   #13
Tech Apprentice
 
Join Date: Jun 2008
Posts: 94
Trader Rating: 2 (100%+)
Default

anymore thoughts
mfroot is offline   Reply With Quote
Old 06-30-2008, 07:25 PM   #14
Tech Master
 
PowerHouse's Avatar
 
Join Date: Nov 2007
Location: Buffalo, New York
Posts: 1,351
Trader Rating: 66 (100%+)
Default

Looks like you are on the right track. The changes you made from what I read will not hurt anything. You made some good key changes, made enough change to make a noticable change but still on the conservative side so there is still room to make changes if you need to target a specific need. When trying to accomplish that, there is alot of mathmatics involved but also experience. What I mean by experience is over years of R+D, you will be able to look at a motor and know exactly what it needs without even having to measure it up. I'm at the point now, all I do is figure out bore, stroke, blowdown timing, crank intake timing, what exhaust will be used degree the ports and grind. I don't need to port, test, make changes, test again and then do it all over again. Been there, got several t-shirts. I got your email and I will answer it here so everyone can read and understand:

One thing you will learn about these engine is that the tooling is everything. There are so many tricks you can do and the right bits will make it come alive. They help to cut down grinding time but at the same time it helps shape the ports to the proper size, shape and entry angle. I have approximately 75-80 different diamond tipped and tungston carbide bits that run anywhere from $6-$15 apiece and it takes awhile to find them. I have searched high and low for different bits that will help with new ideas but also reduce production time. I can now mod 3-4 engines in an 8 hour time period depending on the port package and the port count.

As far as lowering the transfer window. You are better off leaving the bottom of the window flush with the piston at BDC because if you lower it any further, the incoming charge will actually ride the contour of the sleeve and will be redirected straight up into the top of the window creating a wall the rest of the charge needs to penetrate before entering the chamber causing turbulance and pack reduction. If you want to get more pack into the case and case transfers, you should try adding some windows at the piston skirts edge. The vacuume that is formed from the down stroke will force the mixture trapped under the piston head to turn the corner and assist with chamber pack. This will increase pack percentage but also help pull the mixture from under and around the crank reducing loadup and wasted fuel. Remember, its not always about the big number but about efficiency. A more efficient motor will always produce more usable horsepower which in turn will be faster in the long run. There are alot more things you can do to change a motors running characteristic but thats something you will have to experiment with and find out for yourself . That's the best way to learn!!

Good Luck!!
PowerHouse is offline   Reply With Quote
Old 06-30-2008, 07:31 PM   #15
Tech Apprentice
 
Join Date: Jun 2008
Posts: 94
Trader Rating: 2 (100%+)
Default

Thank you so much for the reply i will keep working with it and see what happens.
mfroot is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Mugen MBX-6 pic's Blackscale Nitro Off-Road 8 08-18-2008 01:18 PM
Modded novarossi rec 21/modded sts d21B ckeebler R/C Items: For Sale/Trade 3 12-07-2007 04:11 PM
Sacker Pro with Full Option parts for sale, pic's inside!! df-jr Malaysian R/C Racers 7 11-23-2006 12:03 AM
modded revo trade for modded savage savagelover R/C Items: For Sale/Trade 6 08-13-2006 10:30 AM
F/S: Losi Triple XXX-NT, heavily modded, pics inside Dealer Xing R/C Items: For Sale/Trade 3 01-31-2002 06:54 AM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 10:45 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net