About to put the maxx back together, a quick Q or two.

[lykan]

OK guys, I did an exhaustive (no pun intented) search last nigth onr the TRX pro exhaust. I didn't find the answers I was looking for. A lot of info on the trx 2.5 tho

here goes I have a stock head, and a goofy kind of exhaust going on. I have another header to put on. It has a bit bigger tube, and would allow me to put a tuned pipe on.

I'm all for it and would do it, but I'm hesitant. I know these motors need backpressure, and the trx .15 is and older motor. I dont know if this header was deisgned for the trx, or some of the newer .15's.

MY isssue is that I don't want to loose low end grunt for the sake of high revs. It's geared high enough anways, and I think the motor would last longer without the 40k rpm runs.

So the question is, what exhaust is going to be better for me, and my motor. Looking for low grunt to mid range power.

Here's a pic for comparision.

 

[SkyMaxx]

My question is why is there a pipe that was designed specifically for the TRX 2.5 strapped onto your TRX Pro .15? Not exactly the optimal set up for that older engine.

As far as the header goes, you can use any .15 designed side exhaust header as long as it doesn't interfere with your suspension. If you are handy with a dremmel tool, you could also port match the header to your exhaust port on the side of the engine.

I run the TRAXXAS Tuned pipe (it is blue, aluminum, and shaped like the two illustrated above). It is designed for high end, but you can easily get the grunt you wany by changing the gearing towards the torque side of things. Other than that, I do not see any reason you couldn't use one of those two pipes shown above.

 

[olds97_lss]

Not 100% sure, but I think short and fat are for low end, long and skinny are for high end.

So, the one on the left for you.

 

[lykan]

I bought the trx .15 used (still has a bunch of compression), it came with the trx 2.5 pipe. Thanks for the input. I was just afraid to throw on one of the bigger tuned pipes, and or header and loose low ed. I do however have a 18t clutch bell in case it makes the low end worse.

It sure does sound different than my other enigines with that plastic pipe lol.

 

[FastEddy]

With an 18 tooth bell you will have only low end. Don't expect to win any drag races.

As mentioned above, it will work. I just wanted to make a comment on working on your engine and hope its not taken the wrong way.

CLEAN YOUR poop OFF! LoL

Any tome you open your engine you need to make absolutely positive there is no chance od even a speck of dirt getting inside. One grain of sand can trash an engine. Flush your new header out with DA and dry it. Remove your engine and clean the outside till its spotless before you take the old header off.

Wow typing this thread made me feel like It was the old days and I was picking on Error401 for trashing his engine.

Nostalgic.

 

[Error401]

Tweak it till it smokes, then back off an 1/8th of a turn.

 

[lykan]

Yeah, I'm bad at keeping my rigs clean. No way could I take good advice in a bad way lol. I had it coming. :shrug:

I always clean the hell out of my motors before I work on them tho, specially around the carbs.

I didn't know the header was a sensitve spot to dirt/debris. I guess now that I am thinking of it, it's not like a 1/1 engine the sleeve/piston is right against the exhaust port. Thanks fer the heads up on that one.


BTW brake cleaner is like $1.50 a can, is high pressure, and drys fast. Works just as good as nitro clean.

I guess what I am looking for is instant acceleration, not so much wheelie power as throttle=go power.

 

[SkyMaxx]

Originally posted by lykan
...

I guess what I am looking for is instant acceleration, not so much wheelie power as throttle=go power.

The only real way to do that would be to have a snappy engine (tuned to the nines), proper gearing (more teeth on the clutch bell and fewer teeth on the spur gear) and the spur gear pretty much locked down (tighten the slipper clutch nut all the way down).

That being said, a good pipe can contribute to the performance of the engine, but it will certainly not give you wheelies or any great changes in acceleration performance. Also, if you go the route mentioned above, be prepared for problems in the tranny or other areas of the drive train. Why? When you lock down the slipper clutch, you transfer all shocks to the drive train from instant onset of rpms straight into the tranny.

 

[lykan]

I belive right now I am running a 72t spur, with a 20t clutch bell.

I cetainly don't wan to ruin the tranny. I havent had any time with the trx. With the mach, it kind of had a power band, shortly after it took off, I could turn the wheels and goose it. It would break loose on command.

Is it possible to get that same response down low on the rpm band, or is it just how nitro engines work?

I love the speed, and the jumps. It just get frusterating when Ipull up to the wall of a ditch, and it sits and hums rather than starts up the hill. (steep of coure).

If I can't get the type of torque? needed to climb things without a run. I suppose I'll either have to deal with it, or drop in a bigger motor and expect to replace things.

I guess I got spoiled on the XTM stadium truck with the .18. It was a rocket after a touch of the throttle. Of course I never even thougt about jumping the picni table either.

Bare with me, this is my first MT i'm still learnign the boundarys, and what to expect. Thanks for your patience

 

[olds97_lss]

The maxx is probably significantly heavier than your ST. I know mine tips the scales at 15lb. A stadium runs around 5-6lbs.

This is mostly why I don't believe the maxx should have anything smaller than a 21 on it. It's 3 times heavier than my ST with the same displacement? My losi xxx-nt is quick and agile and more power than I can handle easily with an OS 15 cv-r(x) on it. I first tried the same engine on the maxx with poor results. Overheated regardless how rich I ran it. If I could keep the temps below 260, it meant I was putsing around on pavement.

Now with a 21, the maxx really comes alive.

Do what you will, it's your $. Depending on what you want to do, you may be able to get away without the 21. For what I do, I couldn't.

 

[alkyula]

Originally posted by olds97_lss
The maxx is probably significantly heavier than your ST. I know mine tips the scales at 15lb. A stadium runs around 5-6lbs.

This is mostly why I don't believe the maxx should have anything smaller than a 21 on it. It's 3 times heavier than my ST with the same displacement? My losi xxx-nt is quick and agile and more power than I can handle easily with an OS 15 cv-r(x) on it. I first tried the same engine on the maxx with poor results. Overheated regardless how rich I ran it. If I could keep the temps below 260, it meant I was putsing around on pavement.

Now with a 21, the maxx really comes alive.

Do what you will, it's your $. Depending on what you want to do, you may be able to get away without the 21. For what I do, I couldn't.

holy crap 15lbs!?!? i have all aluminum/RPM steel cvd's steel gears xtm .21 conversion and my t-maxx weighs 10.4oz exactly using a digital scale at work....damn your truck is heavy!

 

[lykan]

well olds, you kinda made me come to realization. I either need to get a 18-21, a 25 or bettter (lots of money on upgraded parts).

Or I need to sell my maxx, and my st, and go with a savage. I am wondering now if the savage is a lot heavier than the maxx, hence the same problem with a 25 in the savage. too heavy, for too little go.

I think you are right, for the size of the maxx I think it needs a bigger engine off the bat.

Their are so many directions to go, it gets confusing quick. I thank you all for helping me figure out what to go forward with.

Is a fresh ,18 worth puttin gin, or am I gong to have pretty much the ame result as the .15?

 

[alkyula]

for me the small block equiped t-maxx just could not push the truck around while keeping good operating temps....yeah the trx 2.5 made the t-maxx move fast....but lost its breaht while doing so. so i went big block, but i will tell you it will not be cheap, although a properly equiped big block t-maxx is one pissed off truck...as for how much heavier a savage is than a t-maxx...yes stock for stock a savage is about 3lbs heavier than a t-maxx..but the s-25 can push the savage around off-road quite easily. i own both a big block t-maxx and an 24.7 savage, and both have there strong points, but in all the savage can perform just a well as my 1500$ t-maxx and I've only put about 300$ into it, including an upgraded engine.

 

[olds97_lss]

I have aluminum trans case, bulks, shock towers, gas tank, steel skid plates, steel 3-point roll bar, steel cvd's,aluminum diff cases and all the RRP steel gears as well. It's somewhere between 14 and 15lbs last time I checked it.

 

[lykan]

Thanks for the info Alkyula. I like to wrench and build things, but i am not into fix and repair daily. It looks like the savage may be the way to go for me. Less initial output for a strong truck.

Olds, after all those upgraded parts, how well does it stand up to your abuse? Of course I mean durability vs how hard you are on it.

LOL some people are just plain Evil to their trucks.. *cough* el *cough* pirata

 

[SkyMaxx]

LOL...El Pirata isn't evil, he's just plain mean.

As for the truck not handling the torque, perhaps it isn't the gearing or the engine. Maybe it is the clutch bell and shoes. You engine might just be driving the shoes around the clutch bell in slip and slide mode. Without being able to hook up, you will just get a truck that sits there and whines at you.

My .15 powered T-Maxx has a 17T and whatever the stock tooth count is for a spur, and from a dead stop can take a 45 degree or greater incline just fine. If it goes much more than 60 degrees on the incline the truck tends to flip over and come back down. I have some video of it trying to take some vertical climbs and it would make it to the top buy be so petered out that it couldn't plop down level at the summit and drive away...it usually just fell back down the hill.

So, you may want to look at the clutch bell and shoes. You may be able to buy yourself some performance and time for a few dollars less. This will afford you time to save up for a good .21 or better conversion. I think $50-$80 is much better than say $200-400 (engine and kit dependent).

Just some food for thought.

 

[lykan]

You know I guess I'll explain wha my problem is/what i don't like.

Say I pull up to a curb or something like it. If I hit th throttle, it won't... hrmm jump forward, or push the front tires up and over. It sits and hums, in the low rpm range. It doesn't whine or rap up. It just sits and hmms, like a low growl.

I dont mind if it takes a second to get rolling either. As long as once it is rolling it can jump forwrd, or squat and take off.

No wheelies for me please, My stadium truck does back flips at about 30 if I nail the gas. I've had enough of that uncontrolability. Just power when i need/want it.

 

[SkyMaxx]

If all it does is sit there and growl without any increase in rpms from the engine, then it might be time for a new engine or at least a rebuild.

If I had to give you something to look into I'd say check your LSN. You should be able to nail the gas and get a nice high pitched scream from it when it is nosing into a curb. Mine gives a scream and then climbs the curb. That is from a complete standstill from idle.

Your tuning might be the problem, but without seeing the engine in action it is kind of hard to tell. All I know is with the stock gearing and the crappy TRX Pro .15 that I started with, I was able to climb over curbs like they were speed bumps.

Are there any other peculiar behaviors that this engine displays?

 

[lykan]

I just ot back in from a short run. This engine is new to me, onlyhadit out and about twice. Today it seemed to do really good, except for runing a bit on the hot side.

I can't handle this anymroe I'm going to gt a temp gun so I can quit guessing

 

[olds97_lss]

Sounds like sky has something for you to look into. Also, your clutch is probably just slipping. Whens the last time you cleaned the clutchbell and clutch shoes? Over time they build up a shiny film that doesn't allow them to work properly, just slip. I use a wire brush attachment on my dremel to buff mine up.

If I peg the throttle on my 21 maxx, it does a standing flip and lands on the roof... It was cool the first few times, but now it's kind of agrivating.

It holds up pretty good to my abuse. The only complaints I have I think I just fixed with new skid plates from RC-Solutions. They are thier spring steel skids/bumper plates. And, I kept braking fuel tanks, which is why I went with the aluminum one. Just realised that it was my rear shock tower bending so far that it was smashing into the back of the tank and destroying it. Just fixed that tonight hopefully with integy aluminum shock tower on the rear.

Now my only issue is an annoying radio glitch that I can't shake. It only seems to affect the throttle servo. But that's for another thread.