Brokenparts

iTrader: (6)

The biggest weak link in a stock 2.5 is the diffs and the 2.5 itself. When I had one, the engine was tuned properly and it was still running hot. It needed a bigger head for cooling. I dont know about the new 2.5s though.

We bought and put a O.S. .18TM into my cousins tmaxx and the engine has performed flawlessly since we had it. Say what you want to about their price, they are great engines. 90% of the nitro engines I see running locally or online are not tuned properly and I think that has a lot to do with view on nitro engines as a whole. Why would you spend an extra 100 bucks on an engine with just a short of a life span as the others? I think a lot has to do with engine care and the ability to tune.

I always run the 30%, extra punch. Works great if you keep it tuned and add that extra shim under the head. The guy that got my stock .30 couldnt believe it wasnt modded, lol. I had put at least 2 gallons through it, beating on it mercilessly. Never used a temp gauge. I dont think you need to as long as the tune is in check and you have a big opening for air. The engine is going to run at the temp it wants to. Why would you pull the tune out of the sweet spot just for temps sake?

The o.s. 30 that I had in my savage xl outran the stock 5.9 from start to finish and always held its tune. The only thing I did to it when I got it was add another head shim under the head and completely seal the back plate and carb to the block. RB products has a tuning guid on their website somewhere. After a WOT run, the engine should return directly to idle, or very very close, and at no time in its life should the engine 4-cycle or sound like its missing a fire.

Nitro engines are inherently high maintenance. Cleaning air filters and keeping them loaded with sticky oil and the two main front bearings should always be looked at, which requires you to pull the crank.

Sorry for the rant but I for see someone bashing OS >.> I have had nothing but great success with these engines, the quality is there. After my LHS saw my cousins truck running, they decided to start carrying them. They could never get one to run right, and that was a HOBBY SHOP o.O

I traded my savage XL to a guy that works behind the counter on customers cars at another LHS and the first thing he asked me was, "is it modded?" No, its bone stock running 30% nitro. It started running funny on me so I had put it up for a while but the guy at the LHS tore it apart and found a ball in the main bearing was chipped. That engine has a lot of power crammed into a .21 size case, that and the XL is a huge truck, sure it put a lot of stress on it.

Cummins Driver

iTrader: (19)

I agree that most people dont know how to tune, and that is why a lot of engines get a bad rap. My current 2.5 and 3.3 run excellent. I hardly have to touch the needles other than weather changes and fine tuning from day to day.

However, I have to point out that I dont agree with tuning by temperature. I have heard traxxas engines run hotter than some, but I dont know because I have never checked the temperature on any of my engines. Tune for performance, and if the engine is responding good, never cuts out, and is clean with proper airflow through the body and had no air leaks, then the temperatures will be fine.

Overdriven

iTrader: (18)

I have a soft spot for these trucks, I've had at least a dozen, but it's a love hate relationship. They're finicky. You can cartwheel it half a dozen times one minute and it'll be fine. Then roll it twice a minute later and something is broke. Working on them is time consuming especially if you have to get to the diffs but they are fun to drive. The upgrades you list are smart, sensible and affordable and would make it more fun to drive.

I've had mixed results with Traxxas engines. Some were easy to tune, others I've had to chase all day long. But most were fine as long as I went for performance and didn't try to stay on the safe side. If you're looking for an upgrade go with the OS 18 or 21 that are a direct drop in as they have more power and are a breeze to tune. Chassis, the best setup is aluminum bulks and stock arms. Aluminum bulks with RPM arms sounds better but then the weak link is hinge pins. They won't break, but even Lunsford titanium hinge pins will bend to the point that the suspension binds. To get the old pins out you'll have to use a hammer to pound another straight pin in. The guys with UE stuff make their hinge pins from Ejector pins that are supposedly stronger but I've never tried them.

Upbasher

iTrader: (3)

I HAVE owned a tmaxx 2.5, the exact one he is talking about. That's how I know. If I didn't know anything about the subject matter then I wouldn't be recommending things. As for tuning, you are right, forget the temperatures. If its running good, has good power and doesn't make any strange noises then you're fine. I've been tuning nitros for three years and have never once used a temp gauge....and never had any problems

Brokenparts

iTrader: (6)

Cummins Driver, I did stop tuning by temp. I got sucked into it when I first got into nitro.
The 2.5 that was in my truck had the old small cast heat sink and it ran over 300F. That is too hot regardless!!!! The newer 2.5s have a nicer machined head I think.

Overdriven, I know you are experienced so dont take this the wrong way please. Just something I want to point out. If you are chasing the tune on an engine, there is an air leak somewhere. In the carb, back plate, main bearings (I have had air leak from them, you can spot it because there will be oil pooling under or around the flywheel). There could even be a leak in the exhaust somewhere or in the fuel tank. These things rely on being 100% sealed to keep the pressure regulated. If you are losing pressure in the tank or air is escaping/entering the engine that will seriously screw with your tune.

Once an engine is in tune, it only takes 1/16 - 1/8 turns of the needles to keep it there. Imagine how small of an adjustment that is. Now picture a gap in the engine block somewhere, that gap will expand and contract with the change in temp of the engine, usually leaning the engine out causing it to run hotter which in turn will widen the gap allowing it to run leaner still. Then you finally get the engine cooled down and its so rich it doesnt want to run at all. A worn out piston and sleeve can act similar.

Then there is the issue of break in. I break my engines in with a SLIGHTLY rich tune compared to what it would run full bore out on the track. Sometimes I run the tune spot on and just take it easy on the engine, constantly varying the revs. There is a million ways to do it but what I am trying to get at is that you do not want your engine so rich that it is spitting oil out of the pipe and 4-cycling. That is just my opinion. It causes a lot of unneeded stress inside of the engine. If your tune is close to what you would run in the parking lot or on the track, there is plenty of oil in the fuel to keep things lubricated.

Sorry for hi jacking your thread
I run a brushless emaxx right now and the weakest link was the rear diff and the bulk heads. A set of GA aluminum bulks or fast lane with robinson racing gears or a 1/8 diff setup would be ideal. Those are the hardest parts of the truck to work on. Suspension arms, towers, shocks and the like are a lot easier to get to and replace. Do yourself a favor if you have the cash and grab those two items. Make sure everything is shimmed properly in the diffs and you will have a tough truck, I promise.

I am not a complete OS fan boy. One of the greatest engines I ever had was an RB concepts. This was back when I was still kind of new to the hobby. I did not have enough oil in the air filter and on a dusty track it sucked the dirt right through it. While it was running it out ran everything at the track, C5BB. It was a little harder to tune because the mixture window was a little smaller but holy crap was it fast when you got it right!!

OS .18 is plenty for a 2.5 platform. The .21 would probably rip the transmission apart and you would not be able to keep the front end on the ground. I think RB makes a tmaxx drop in too. If you do buy one of these power houses, I would also eliminate reverse. It will break.

Brokenparts

iTrader: (6)

I am 26 and started tuning nitro engines when I was around 8

Novarossi makes a budget engine with pipe for 175. I am sure that is a great engine. Just about anything would be better then the traxxas engines.

I would buy
Ofna/Picco
Novarossi
RB
OS
Werks/sh
axial... maybe

I would stay away from
Dynamite
GO
Mach
Dont know much about ORION

I dont know who produces the engines or where they come from. I am just speculating from my past experience and what I have seen/read on the forums over the years. RB holds a spot in my heart for pure performance and OS for their excellent performance and build quality.

And I can not stress enough on sealing the engines with RV sealant or the product they sell at just about any nitro retailer. I used ATV air filter oil, its sticky as hell. Buying the right plug for the nitro % and weather conditions and shimming the head properly for the fuel you chose. It all does make a difference and can make or break the performance and tuning experience.

STEPS OFF OF SOAP BOX

Cummins Driver

iTrader: (19)

Sorry, wasnt trying to come off as saying no one here had owned on. Its just that all the replies before mine seemed like they were saying the maxx was a hopeless platform that was good for nothing. It does for sure have its flaws and things that need upgraded, but it can also be a very fun truck if you dont abuse your stuff too badly. With the new design upgrades to the 3.3 that can be swapped onto the 2.5 platform, it helps a lot because it used to be that you had to buy expensive aftermarket CVD's, diffs, etc... which were a lot more expensive than the chop shop 3.3 parts that are available now. I just hate to see people telling him his truck is crap and not to spend any money on it, when for a fairly reasonable amount of money (in this hobby), it can actually be upgraded to have a strong driveline and be reasonably tough for most normal bashing(not pure abuse).

Cummins Driver

iTrader: (19)

I know exactly what you mean. I broke several things on my old 2.5 before I sold it, but at the time, I was young and didnt have much money to spend on it, and worse than anything was that the truck was basically worn out before I got it. Those upgrades I listed above, as well as fixing some of the rigging that was done on the truck would have fixed most of my issues. However, I have never broken a single part on my savage aside from busting the rear differential after about 10 gallons, and replacing some drive cups and a driveshaft. Its been bulletproof for the way I run them and I think the savage is darn hard to beat for out of the box durability. However, I did enjoy driving my t-maxx and would for sure own another being a little smarter on how to make one last now than I was with my first one.

In4mation

After upgrading the shocks on my Savage XL, it was practically bullet proof, except for the front and rear ring and pinion. Aluminum diff cases would probably solve that. I used to jump it at the top of 3rd gear down hill over my head. Tough truck.

Is it diff cases? Im not talking about the case mounted to the gear but the case that surrounds the diff and holds the bearings for the output shafts.. That would keep the gear mesh in check.

Overdriven

iTrader: (18)

@Brokenparts: l I had plenty of issues with air leaks on my Tmaxx's, mostly from the header. But even all sealed up with RTV there were some I had to chase constantly. Overall my biggest issue with Traxxas engines was getting a good consistent idle.

@Cummins: I was younger when I had all my Tmaxx's too, but I spent quite a bit on a few of them, even had 3 big blocks. I still love the truck and would like to have another, but wish I had spent less on that platform and invested in another instead. I never went for bling on any of mine but still found you can definitely be crazier with what you spend on the truck than you can be driving it. One day I'll get another with an O.S. 21, EZ start, aluminum bulks, skids, outer diff cases, maybe Ofna buggy shocks and the rest will just be 3.3 spec. That should be a fun runner that'll take some abuse and only the arms will break.

Edit: Before someone thinks I'm nuts for having owned a dozen Tmaxx's, it wasn't all at once. Most we're bought for cheap, fixed up a bit and moved on. Only one was bought new, and I did build 5 trucks for myself, 3 big blocks, one small block and one Emaxx.

Jimmy Lauri

iTrader: (2)

A great read you guys! Love this stuff! Im gonna order a new TMaxx now! Its what got me back into the hobby. Nostalgia reasons..ya know! Always...thank you guys! Jimmy