Thunder Tiger .21 O.B. Hop Ups

[Bill Deutsch]

Hello All,

New to the forums here I read on rcu there was a thread here on this topic and can't find it so I am starting one. If there is another please post a link. I have been running boats for the past 2 years with some guys from my airplane club, We meet once a week and run for fun and bragging rights. The common set up is T.S. 3 or VS 1 with stock TT 21's. I am looking for ways to hop up the motor without a big expense as it's for fun. I de-tongued / Polished / Balanced prop. I also Polished / Sharpened lower unit. I was thinking of polishing the ports inside the case. I run 15% fuel Because thats what I run in the plane engines. I was thinking of cutting the muffler off and using a tuned pipe. Any thoughts or Ideas are Greatly appreciated. Also if you have pics of your O.B. please share them.

Thanks,

Bill

 

[Kevin Krogness]

If you do a search you will find a lot of info on this subject. After work Ican tell you more that I have learned over the years ....

 

[anthony_marquart]

Tuned pipe and more nitro will gain you tons!

 

[RodneyPierce]

Bill, I have personally found that there was not a very big performance increase in the TT OB engines when switching from 35% nitro to 66% nitro. I only seen a gain of about 1 mph. (Im usually a very big advocate for high nitro fuel in these little guys, but the TT is one platform I did not notice enough difference to warrant it)

Also, what prop do you have? If its the prather 215 that came on it, I would switch it out for an X637. That is the prop to have on the TT.

If your going to run a tuned pipe, you need to do some sleeve work, as the numbers stock are very low. Raise the timing up, have the head button cut to .17cc and drop the head clearance down to .008. Crank induction numbers are a little shy as well, but they will work stock.

Solder the water outlet shut, and drill a .030 hole in it to restrict the water and get some heat in the motor. She will run darn good. Fastest I had my sport OB tunnel running was 44mph on a stalker radar gun. Not too shabby!

 

[Tim_Duggan]

Rodney Speaketh the truth.

Forget about polishing the ports in the case - waste of time.

 

[Kevin Krogness]

Rodney hit the nail on the head!!! Get the temp up by removing some water and throw a 637 on it! You could remove the head shim and bump the nitro % up also. But for sure the 637 prop and make sure it is making some good heat.

 

[Bill Deutsch]

Thanks for all the info, I did a search and found alot info. Kevin your motor looks awesome! I am running the stock prather, I had an octura 437-3 on it I don't think the motor was set up right on the hull I had to cut the mounts and add shims to lift the motor up to get it to run pretty good. This motor has the 1.09-1 gears in it. I do have another TT with the 1.19 gears and a 440-3 that runs great although I popped the motor and replaced piston/rod/sleeve out of TT car motor don't know if that helped with porting? I would like some pics of the porting that you guys have done I am not an idiot but when you talk about cross port intake I hear the Charlie Brown teacher. I am a visual learner just ask my wife. I gotta get to work.

Thanks,

Bill

 

[Chris Roberts]

Guys

I'm one of the old guys that runs with Bill for what use to be fun & bragging rights. My question is, does anyone have the name of a good engine builder that can say " I'll make your engine run faster than Bills for $"

 

[RodneyPierce]

Chris, there arent many that work on the TT's these days. Jerry Wyss used to be the guy. Then Alden Cost, but Alden has fallen on some hard times as of lately, and Im afraid doesnt have the time to mod them.

I just dont know who to refer you to for that work.

Bill, the pictures really dont do much justice, as all we are doing is raising the port roof's X amount to get to the timing numbers that we like to run. The best way to go about it is to get yourself a good set of digital calipers, a depth gauge, and Marty Davis Engine Analysis Program. Take the measurements needed (accurately) and input them into the software.

You can then figure out how much you need to remove from the top of each port to get to whatever number your after. Just be very careful and easy, as it doesnt take much to remove too much from the port roof, then the sleeve is junk.

 

[shoboat]

Chris and Bill,

There is a lot more to performance than motor work.

The propeller will give you probably the most bang for your buck.

If you are just running stock propellers there is a lot more to be had.

Set up is also very important, and quite a few overlook driveline lubrication

also with outboards.

Keep Testing Different Set Ups,

Mark Sholund

 

[Grimracer]

Bill and the rest of you "GEAR HEADS" welcome to racing the way we love it!



Some years ago I met a BAD MOFO racer by the name of Tommy Lee. He had two quite profound quotes that I have stuck by over the years.



#1- "If the waters to rough for good tunnel racing leave em the in trailer". I was full of piss and vinegar and did not listen. After some years however I now know what he was talking about. Its about a good time and a good side by side race. Not fighting or racing the water. You are going to have WAY more fun if you wait for the water.



#2- “After the boat is right I go “IN” the motor IF” I need more speed” Meaning he very seldom went into the motor. I guarantee you this, his hull, prop and setup was DEAD ON. I have not raced a modified tunnel motor in over 10 years and have had some good wins in this time.



Get the hull itself proper. Blueprint the bottoms, Scuff and re-check what need attention.

-Test-

Get the motor on the transom and learn it. Meaning make sure you know what happens FULLY when you make an adjustment, Lower, tilt, pin shimming.. whatever..

-test-

Props. EVERYBODY here has WAY MORE props that do not work then work.. that is if they are winning races! Get a hand full of props, S/B, line em up side by side and test each one fully..

-test-

-test-

-test-



Then.. don’t just drive the boat around.. drive it around something!.. Make sure you setup a course of some kind. Its not about making it fair for everybody its about you getting to know your boat better. When to lift, when to counter steer, when to punch it!

-test-





Make sure the hull is right for you. Not everybody has the same driving style. It’s seldom talked about on the forums and the boats you have now might not be the boat you ultimately settle on. In the future try a few others.. with all of the above in mind.. mind you!



Then when you have all this done.. and need to win some races.. you can go into the motor to learn more.. OR hire somebody to warm one up for you. You will find some very good engine builders for sale here..(or learn yourself and pocket the money). Some of the best engine builders I know really do very little to their motors…lol They just, like the boat tips above.. “learn” the motor and only adjust when needed!



Welcome and have fun!



Grimracer

 

[Kevin Krogness]

Grim is spot on!!! He came to the local race and beat all the modified tunnels with his stocker OS!!! As he says get to know your boat and how it reacts to what. As I was the guy trying to chase him down with a lap or 2 left and I hooked my boat and killed it... So instead of finishing 2nd or catching the Legendary Grim Racer I got 25 points for a start....

I can say this both Alden and Jerry both told me and many others

And I do believe the 637 is probably the best prop for the TT! Thay also loved th K&B 1l plugs.

But for sure find the boat/engine combination out first as that will yield better results when its time for the engine mods!!!

 

[Bill Deutsch]

Thanks for all the input. I am going to do some mods, though I won't say what as Chris has found this topic. We are really chasing down 1 guy that runs with us.We all have the same boats n motors/props and he just blows by. He is running your VS1 Mike! Which by the way I have one NIB in the basement to replace my TS3 when it's time. (we trade ALOT of paint/wood/fiberglass) We do run a triangle course that was described in the TT manual and it works for the room we have. I recently bought a Zip Kits O.B. outrigger kit to build over the winter in between my airplane projects. I am putting the slightly modded TT on it. I got a prather O.B. outrigger with a K&B gold with tuned pipe and lawless drive that I may put on the VS1 to try and catch the O.S.'s on the pond.

 

[Grimracer]

Bill.. Kevin brings up a good thought..



Plugs, fuel and basic engine settings...



Rule one.. if the motor just quits its lean.. be it needle, bearings or other.. Repeat with me.. if it quits.. its lean!



Next.. (non Piped).. use the hottest plug you can get away with. 1L, MC-59, OS8, ODRED, or other. I have had the best luck in 2012 using LC3 from OS. I also had great results with the #8.

Please use BOAT FUEL, and truth is 50% is plenty of Nitro. Dont get caught up in the nitro game. 50% will get it done.



Lastly.. If your motor just sits and idles fantastic.. its likely too lean to heat race well.. here is why.



Your RC boat motor is under the most amount of load of any of the RC segments. In saying this you want a rich fuel load to the motor at all times but this is very important when you lit off the throttle. The combustion chamber is hot and is going to need a fresh fuel load to get the RPMs to cycle back up. So.. you want a “have to stab the throttle from time to time” to clear the motor before launch.. OR.. when racing a hydro or mono a very high idle..



Go get em and thanks for choosing an AquaCraft Product!



Grimracer

 

[Slideblues]

I splintered one before figuring this out: Villain series (VS1) blip throttle (sets sponsons) before turn in, finesse hull not white knuckle.........

Gene

 

[Mike Daly]

Hi Guy's - great info here !

Would the advice given on running the TT hotter by reducing the water supply also apply to the K+B's ?

Mike

 

[Grimracer]

The best way to get higher constant combustion temperature with a K+B 21 is with a Keeley Head..

 

[Mike Daly]

Thanks Mike