!! Mods for the 2.5 that WORK!!!??

!! Mods for the 2.5 that WORK!!!??
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!! Mods for the 2.5 that WORK!!!?? - 6/9/2004 6:51:46 PM

Deandome

Posts: 1128
Joined: 9/3/2003
From: Libertyville, IL, USA
Status: offline

I've been loitering & shopping over at the Unlimited Engineering forums, and there are several threads that talk about how putting an RB Concepts carb on the 2.5 is a really sweet upgrade!! Here's what MonsterMaxx (owner? Head dude @ UE) himself had to say:

quote:

I've got the X15 carb,[RB Concepts] a restricter (don't know which one) and have extensively ported it by whatever magic recipie makes mine work good most of the time. It's not repeatable, it's not dynoed, but about 70% of the time I end up with a really hot motor.
I watched, there was nothing faster than this one down the straight in the .15 class and there were silly expensive motors in that class. Motors you and I can't even get.
Truck was clearly on the TQ spot & w/o being put out by two corner marshals in a qual and the main there's no doubt the results would have been different.
I run it on 30% blue and don't reshim the head. I think they had it running on some sort of clear 20% last weekend.

We are all standing around scratching our heads on why that truck runs so good and handles so well.

Rody did the same thing to us this weekend, far out handling any of the other trucks...and we aren't sure why. Maybe just luck associated with being firsts

.

Positive vibes on the 2.5 in the land of UE??!! I thought the vitriol woulda been 10X worse than it is over here!! Dunno how much that carb costs, but I believe UE sells them, as they seem to be a full RB dealer (and very tight with their owner & engineer, Rody Roehm, the guy mentioned in the quote!!).

Of course I hear this AFTER I chose to upgrade to the OFNA mid-block, but maybe I'll hold on to my 2.5 7 rebuild it down the line...with an RB carb!!

BTW, UE's site is www.unlimitedengineering.com , but you'll need to register to peruse the Forums.

Dean

Post #: 1

RE: !! Mods for the 2.5 that WORK!!!?? - 6/10/2004 4:10:24 AM

R/C Madman

Posts: 1325
Joined: 12/10/2003
From: Monee, IL, USA
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As qouted "I've got the X15 carb,[RB Concepts] a restricter (don't know which one) and have extensively ported it by whatever magic recipie makes mine work good most of the time."

So, the carb it's self will not be a magic fix. Now if you could just find out if he or whoever ports his engines would do that for you you would have something!

_____________________________

Hardcore Basher!

(in reply to Deandome)

Post #: 2

RE: !! Mods for the 2.5 that WORK!!!?? - 6/10/2004 7:09:01 AM

fhm101

Posts: 2467
Joined: 12/22/2003
From: Pinson, AL, USA
Status: offline

I saw several 2.5 trucks with the RB carb this weekend and they were having as much, if not more trouble dialing in their engines as where the 2.5's with a traxxas carb. If you want ease of tuning for less money, pick up an OS 10D or 10J, both work fine on the 2.5 and both will produce as much power as the stock 2.5 with much less hassle. I've used both of the above OS carbs on the 2.5 and they are the only way to fly if you want rock solid reliability.

< Message edited by fhm101 -- 6/10/2004 2:11:16 AM >

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Post #: 3

RE: !! Mods for the 2.5 that WORK!!!?? - 6/10/2004 9:49:45 PM

Running_On_E

Posts: 127
Joined: 4/7/2004
From: Ft. Lauderdale, FL, USA
Status: offline

Here is my secret to turning the 2.5, Get rid of the fuel tank! put a kyosho 120cc tank on.. and use the Siro big bore pipe, ( i live in south florida, and race, on saturday at night, and then sunday in the morning to after noon. with a huge temp change.. and I dont even have to touch carb settings.. i have soo much power!! my top end is like insain,, and my temps at around 190 at night to about 240 in the day time.. i could lean this puppy out even more,, but its already way to much power for me to handle.. .. top qualifier at the last two races, but due to melted diff bearings and a stripped spur gear.. i didnt do so well in the mains.

Reason for these additions.. are as follows
The Kyosho 120cc tank created a higher pressure on the fuel, forceing more fuel to the carb.
The Big Bore Pipe, Reduced the back pressure of the exhaust. Kicking out more heat, and clearing the chamber quicker.
Also, i applied some Silver Heat flux on both sides of the engine mount.. ( causing the whole chassis to become one large heat sink )

And this is repeatable, My bro owns a T-maxx with an upgrade sirio .18, he was just fooling around with old parts and put together a rally sports car, with buggy diffs, a sheet of allumin, Axis II suspention. , a spare kyosho 120 fuel tank, his old 2.5 engine, we already knew that the big bore .18 gave the trx 2.5 a serious kick of bottom end.. so we decided to strap it on.. At first i was puzzled, 3 turns out on the HSN and the engine was still bogging down seriously, after re-checking the carb, and air filter we decided what the heck lets keep screwing the HSN in, finaly at 2.5 turns out on the HSN this home made racer came alive. I was impressed , partly because i thought this engine had already expired.. but mostly because how freakin quick this car raced thru the whole RPM range.. for a single speed, it had serious bottom end.. and yet i wasnt able to red line then engine nor reach a point at which it looked like the car had stopped accelerating.
So i was like if it can work on an old worn out engine.. what will this setup do with a Freshly rebuilt 2.5 engine. Slapped the fuel tank and exhaust in my TMaxx, and Tuned it in, and now I have the fastest truck around.. and no more tunning issues.

Try it and see for yourself

< Message edited by Running_On_E -- 6/10/2004 4:51:36 PM >

(in reply to fhm101)

Post #: 4

RE: !! Mods for the 2.5 that WORK!!!?? - 6/10/2004 10:03:34 PM

Deandome

Posts: 1128
Joined: 9/3/2003
From: Libertyville, IL, USA
Status: offline

Hmmm...

I'm starting to believe some 2.5s come 'better' than others, but the biggie is break in. BTW, I just read somewhere that making sure the piston is in full/center DOWN position during the break-in's cooling off phases is really important.

Your mods are sound...EXCEPT the Kyosho tank one, IMO!! The problem with relying with tank "pressure" (caused by having the fuel level higher than the carb) to increase flow is that as the fuel level changes, so does that pressure, so the engine runs differently. That's the big problem w/Savages, it's called "leaning".

The fuel tank mods that MANY people recommend is dropping in either this OFNA tank, or a tank from the Rustler, both of which have LOW profiles.

You say your tune stays constant all the time, but I think, and the laws of fluid dynamics dictate, that this would be in SPITE of the Kyosho tank, not BECAUSE of it!!

Dean

< Message edited by Deandome -- 6/10/2004 5:12:03 PM >

(in reply to Running_On_E)

Post #: 5

RE: !! Mods for the 2.5 that WORK!!!?? - 6/10/2004 10:41:52 PM

Running_On_E

Posts: 127
Joined: 4/7/2004
From: Ft. Lauderdale, FL, USA
Status: offline

Yea I would have to agree that is probably the reason, but i cant prove it because ive only used the kyosho tank. The other thing is that there is a serious increase in pressure on the fuel..even when only using the stock pipe and this fuel tank, I had to zip tye the fuel line on, not because of air leaks but because fuel was being forced out. After that i had a hole in the fuel line,, instead of causing an airleak, it caused a fuel leak.! I do not understand why this mod had such a drastic effect on the fuel pressure so i attributed it to the fuel tank design as it was the only thing I had changed at this time. ( This was a mod that failed due to the excess of fuel pressure, it would not clear the chamber or over heat. ) So i scrapped the tank off and let my bro use it for his rally car.

Before adding the fuel tank HSN was at 5.5
After adding the Kyosho 120cc tank HSN was at 2.5

< Message edited by Running_On_E -- 6/10/2004 5:45:03 PM >

(in reply to Deandome)

Post #: 6

RE: !! Mods for the 2.5 that WORK!!!?? - 6/11/2004 8:01:00 AM

fhm101

Posts: 2467
Joined: 12/22/2003
From: Pinson, AL, USA
Status: offline

I have used both OFNA and Mugen buggy tanks on my maxx race trucks and both are very consistent. I recently tried a rustler tank on a maxx with an .18 sirio and an RB outlaw pipe. The pipe put so much pressure on the tank when I nailed the throttle that the fuel would be blown away from the pickup, allowing air to be sucked into the fuel line. I kept thinking I was too lean and continued to crank the HSN out until the thing just wouldn't run worth carp it was so rich. I has to put the truck on a tuning stand and run it with the body off before I discoverd what was actually happening. It ran great as long as I eased into the throttle, but any time I hammered on it, it would take off, run for a second or so then act like it was starving for fuel, which it was, but not because of carb adjustment.

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Post #: 7

RE: !! Mods for the 2.5 that WORK!!!?? - 6/11/2004 3:58:14 PM

Melancholy43920

Posts: 246
Joined: 4/16/2004
From: East Liverpool, OH, USA
Status: offline

i don't understand that Kyosho fuel tank, both fuel nipples are on the top of the tank so how is fuel supposed to get to your carb? doesn't one of them need to be on the bottom for the fuel to flow?

_____________________________

Traxxas T-Maxx 2.5
Trinity Mini-T

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Post #: 8

RE: !! Mods for the 2.5 that WORK!!!?? - 6/11/2004 5:18:37 PM

fhm101

Posts: 2467
Joined: 12/22/2003
From: Pinson, AL, USA
Status: offline

The pressure from the exhaust forces fuel to the carb.

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Post #: 9

RE: !! Mods for the 2.5 that WORK!!!?? - 6/11/2004 8:21:20 PM

Running_On_E

Posts: 127
Joined: 4/7/2004
From: Ft. Lauderdale, FL, USA
Status: offline

yes, but inside of the tank there is a extention that goes to the bottom of the fuel tank, and has a fuel filter on it.

(in reply to fhm101)

Post #: 10

RE: !! Mods for the 2.5 that WORK!!!?? - 6/19/2004 11:41:08 PM

davechappelle

Posts: 62
Joined: 6/2/2004
From: , FL, USA
Status: offline

quote:

ORIGINAL: Running_On_E

Here is my secret to turning the 2.5, Get rid of the fuel tank! put a kyosho 120cc tank on.. and use the Siro big bore pipe, ( i live in south florida, and race, on saturday at night, and then sunday in the morning to after noon. with a huge temp change.. and I dont even have to touch carb settings.. i have soo much power!! my top end is like insain,, and my temps at around 190 at night to about 240 in the day time.. i could lean this puppy out even more,, but its already way to much power for me to handle.. .. top qualifier at the last two races, but due to melted diff bearings and a stripped spur gear.. i didnt do so well in the mains.

Reason for these additions.. are as follows
The Kyosho 120cc tank created a higher pressure on the fuel, forceing more fuel to the carb.
The Big Bore Pipe, Reduced the back pressure of the exhaust. Kicking out more heat, and clearing the chamber quicker.
Also, i applied some Silver Heat flux on both sides of the engine mount.. ( causing the whole chassis to become one large heat sink )

And this is repeatable, My bro owns a T-maxx with an upgrade sirio .18, he was just fooling around with old parts and put together a rally sports car, with buggy diffs, a sheet of allumin, Axis II suspention. , a spare kyosho 120 fuel tank, his old 2.5 engine, we already knew that the big bore .18 gave the trx 2.5 a serious kick of bottom end.. so we decided to strap it on.. At first i was puzzled, 3 turns out on the HSN and the engine was still bogging down seriously, after re-checking the carb, and air filter we decided what the heck lets keep screwing the HSN in, finaly at 2.5 turns out on the HSN this home made racer came alive. I was impressed , partly because i thought this engine had already expired.. but mostly because how freakin quick this car raced thru the whole RPM range.. for a single speed, it had serious bottom end.. and yet i wasnt able to red line then engine nor reach a point at which it looked like the car had stopped accelerating.
So i was like if it can work on an old worn out engine.. what will this setup do with a Freshly rebuilt 2.5 engine. Slapped the fuel tank and exhaust in my TMaxx, and Tuned it in, and now I have the fastest truck around.. and no more tunning issues.

Try it and see for yourself

These are pretty good suggestions, Running_on_E, The only thing that I would correct in your statement is the Kyosho tank. The reason why your Kyosho tank works well is because the tank is not tall. That is the problem with the stock maxx tank. The fuel pressure is different from full to 1/2 full on a stock maxx tank. Any fuel tank (Traxxas Nitro 4 tec, Mugen 1/8th scale, Kyosho 1/8th scale, Serpent on-road) that is no taller than the seam line on the stock t-maxx pipe will have the same affect. I personally use a Mbx-5 tank, a Paris-Rex Pipe (for .12 on-road engines), the stock carburetor, and 30% racing fuel(I've used Powermaster and o'donnel before and I am currently using Sidewinder for no particular reason other than experimentation).
Hope thias helps

< Message edited by davechappelle -- 6/19/2004 6:42:31 PM >

(in reply to Running_On_E)

Post #: 11

RE: !! Mods for the 2.5 that WORK!!!?? - 6/20/2004 6:05:49 PM

N-4-Speeed

Posts: 286
Joined: 4/23/2004
From: Kpt, TN, USA
Status: offline

So installing a buggy fuel tank will make the car a little faster? Does it fit the chassis easily (like without custom work)?

(in reply to davechappelle)

Post #: 12

RE: !! Mods for the 2.5 that WORK!!!?? - 6/20/2004 9:12:57 PM

N-4-Speeed

Posts: 286
Joined: 4/23/2004
From: Kpt, TN, USA
Status: offline

Do those motor-saver airfilters help? I was looking for one with a rain cover, and there is a rain cover available for them so i can run it in the mud and rain w/o feeling like im killing the engine lol. I obviously still need to waterproof the electronics tho. Do the motor-saver airfilters give a little more power?

(in reply to N-4-Speeed)

Post #: 13

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