airwebb

My Feedback: (3)

Iam just getting into the q-500 racing. I have heard from another member in my club that there is something you can do to modify the tt pro 40 with out breaking the rules to get alot more RPMs. Of course he wont tell me. So i thought the right people to ask would you guys. Right now i race club 40. My tt pro 40 spins 14400 rpms with a 10.5x 4.5 prop. I have heard of guys getting 16k ALMOST 17k rpms out of there tt pro 40s. any ideas? I have lined the fuel intake nipple up with the hole in the high speed needle so the fuel flows directly into the carb. Is there anything else i can do or buy to make this think faster with out breaking the rules. Thanks alot. Justin

speedracerntrixie

My Feedback: (29)

Justin, while I don't race Q-500 anymore, I'm fairly sure that according to the rules you are allowed some shimming and thats all. Shimming the piston liner up in the case will alter the port timiming to work better at a slightly higher RPM. Using a slightly thinner head shim ( gasket ) will increase compression. Too much compression can make the engine pre-ignite and loose power.


When I did race Q-500 what worked best for me was to take apart a new engine, clean the parts very thoroughly and re assemble using ATF as an assembly lube. I spent a little extra time getting the bearings in alignment. The next is a proper break in. You want operating RPM, light load and rich needle setting. For the TT I would break in with a 9X6 and after 1/2 gallon I would throw on a 9X7 and go race. Selecting a plug with the correct heat range makes a difference too. In the warbird series I do race in, my engine of choice is a Rossi .45 with a Jett muffler. The APC 9X7 sport prop is what has worked the best for me along with an Enya 3 plug

blindfaithnogod

break in a tt 40 with a 9x5 prop spinning it at 17k rich first run. you will need to monitor the rpms throuh the run. the engine will free up through the run. next run fly it rich with the prop you intend to race with. and lean on it each following run.

you can also remove the stock head shim and replace it with about a .003 thick shim. rossi shims work in these enigines. also check with performace specialties.

i would recommend a 10x4 for club 40, esp if you pull hard turns. other wise you could go up in pitch if you fly wider and smoother.

Bozarth

My Feedback: (15)

FYI: Normally APC 9x6 are the only props allowed in 424.

airwebb

My Feedback: (3)

great information.  Thanks a ton.  Ill be ordering some shims this week.  And maybe a new engine to breaki it in properly.  Thanks again.

fizzwater2

My Feedback: (61)

check with Performance Specialties (www.pspec.com) - they used to have an assortment of shims that will fit the TTpro .40

blindfaithnogod

also if you get a new one, you may want to check the clearance between the rod and the crank. around here we've had at least 4 recent engines have the rod come apart because it got too hot. not enough clearance.

fizzwater2

My Feedback: (61)

where is it rubbing? I have a new one I haven't run yet, I ought to check too.

PylonDave

It you are racing in the Nepro series in new england . I believe they DO NOT allow removing the stock head shim. You may want to go to thier site and ask someone.

http://www.neproclub.org/

This is from thier site.
ENGINE AND MOUNT

No modifications are allowed. This includes head shims and the removal of the muffler baffle!!

The only engine allowed is the Thunder Tiger Pro .40 R/C. Remote needle valves are permitted for safety reasons. The only pressure allowed is muffler pressure. All replacement parts except screws, bearings, glow plugs, prop washer and nut must come from the manufacturer. A rounded spinner or safety nut is required. The engine must be fully exposed between the engine lugs. No cowling or streamlining of the engine is permitted. It must be demonstrated that the throttle is operational and able to be shut off by a dedicated servo on demand by the transmitter.

Mikey D

Its a combination of events. I know your asking about Engine Stuff, but I assume your ultimately asking about how to go faster? With that in mind, your biggest gain will be flying a tight course, level and consistent. If you don't get this part right, the momentum you lose with inconsitent laps will never be able to be made up with your engine setup. If you get right, you be tuff to beat. In addition to the above, you may also want to back out your low needle valve setting that's usually good for a few hundred RPM. Also, try some different plugs. If you can find some K&B 1L's they work good. I don't fly 424 very often so there may be some other plugs as well

I haven't seen to many people messing with shims, I have heard people taking them out though.

I will leave it with this..... I've seen plenty of good pilots bolt brand spanking new motors right out of the box no modifications what so ever, and spank the field. Like I said the biggest gain is staying level, consistent, and tight on the course. You may not win everytime, but it's a pretty good recipe.

Mikey D

blindfaithnogod

the rod to the crank. it needs lapped in.

GSJames

Mike: What do you use for lapping compound these days? In my CL Combat days, on the G21-35's we used automotive rubbing and/or polishing compound.

blindfaithnogod

I am paul f.

mike did lap mine in. not sure what he used. I'll ask him when I see him tommarow. we have club combat. he doesn't fly, but he supports us. he'll be around for the event in august. hope you can make it up.

by the way, the break-in procedure i described earlier came direct from him.

[email protected]

refer to a PM I've just sent to you, trevor H, NZ

GSJames

Sorry Paul, I thought that "blindfaithnogod" was Mike's "handle". I'll see ya at "Anarchy over Afton" in August.

PylonDave

Cmon Trev , share it with us all!!! :-)

[email protected]

there are no secrets -very simple - give the big end some 'big' clearance -like about 2 thou. Easily done with a rolled up piece of wet and dry 660 grit paper and you dont want it polished...coarser the better. The bigger the clearance the more lubrication is possible-never broke a rod yet. Actually tried to destroy a TT to see which bits broke first- even running one at 20,000+, the engine is still running strong after two years use. The newer engines have got the better bearings so don't replace them. Check end float on the shaft- you should have some. I've found some to have zero...If you have changed the bearings to C3 clearance then this won't be an issue. The engine is undecompressed - good for unwinding in the air. I run mine with head clearance as supplied but have a variety of HOT plugs that I change to suit the weather- enya #3, and merlins, and even McCoy....there is a significant difference. The plug type being determined by wet or dry air. Experiment with a rev counter. Carb mods are very simple but very importantly remove the barrel spring, and replace with a piece of fuel tubing about 3mm long. the spring has been known to be digested by the engine.- wind out the bottom jet as far as you can and cyano in place. I threadloock all the carb body components together, have even used epoxy. (epoxy is possibly a better product to use)The needle body is known to harmonic at the 15,000 - 16,000 rpm and destroys the orings on the needle very quickly. Slide a large diameter fuel tube over the needle/ needle body to ensure airtightness, this tends to stabilise the needle and raise the harmonic level quite suibstantially........
There are two blade shapes for a 9x6 APC- one is the normal curved shape but there is a straight blade also available- that is in my opinion the better prop.This shuld help,
Found the engine performs best with the baffle retained inside the mufflere, but suggest you get the muffler welded together. regards trevor h, nz

daven

My Feedback: (1)

Read your local rules, then read them again.

Many of the mods above are NOT legal.

[email protected]

Yes, you maywell be correct for the USA, I haven't checked your rules, but the comments that I have listed comply with NZ rules, trevor H

djlyon

Nothing you've done violates APRA rules ( flown in most of the southwest and west US) as long as you do not remove baffle. Generally I end up with the head shim about .005 to .008. Generally what you have done is typical for us except for working the rod big end. Never heard of a big end breaking.

Denis

fizzwater2

My Feedback: (61)

424 engine rules from the AMA:

16.3.2. Powerplant
a. Engine.
1) Maximum displacement: 0.403 cubic inch.
2) Configuration: Stock, commercially available, front-intake, side-exhaust.
3) Intake: A single carburetor, as supplied by the manufacturer of the engine being used, with a maximum inner diameter of 0.325 inch. The carburetor shall be fully functional and shall be stock, except for longevity-enhancing modifications as follows:
(a) Adjustment screws and idle needle valves may be held in place with commercially available thread locker, epoxy, or other adhesives and safetied with rubber bands, wire, or plastic ties.
(b) Barrel retaining screws or pins may be replaced with commercially available screws or pins of harder material and may be held in place with commercially available adhesives. Barrels may be deburred for smoother movement and may be safetied with rubber bands, wire, or plastic ties.
(c) Throttle arms may be modified or replaced.

According to this, removing the spring from the carb and replacing it with fuel tubing might not be considered entirely legal, since the "fully functional and stock" would be violated. It looks like you can glue / loctite / all of the screws & such in place.

Is this what you're getting at, Dave? Just wondering.

airwebb

My Feedback: (3)

when i use head shims, do i use a head gasket too or not?

[email protected]

I would argue that removing the spring is a bonafide longevity modification.........it certainly could extend the life of your engine- isn't that the intent of the rule? TH

daven

My Feedback: (1)

I'm just saying make sure what you do conforms to your local rules, lots of variations from group to group.

Not pointing fingers, just not sure what is acceptable in every area.

I don't believe Nepro allows head shims.

djlyon

By head gasket as opposed to shims I am assuming you mean a fabric gasket of some sort. The TT PRO 40 does not use a fabric gasket. It uses an aluminum shim. The shim it comes with is about .012 to .014. Generally here when we speak of changing the shims, we are talking about changing that shim to a thinner one in an effort to get more RPM on a 9/6 apc prop. But it is necessary to be careful with even that generalization. Engine tolerances need to be considered and local rules. There are many ways to maximize your engines performance and stay with in the local rules. Shim selection is one way and meets the APRA rules.

Denis