mobydickk

Does anyone know for fact why the Traaxas 2.5 and 3.3 are so powerfull?
Mobydickk

Anthoop

They are? What engines are you comparing them to?

To make more power then you need to burn more fuel and/or burn the fuel more efficiently.

mobydickk

I always compare apples to apples, such as (1) $125.00 engine against another $125.00 engine, as the traaxas 2.5 and 3.3 engines have some thing very unique about there design which is something I have observed in only (3) other engines my question was to see if anyone else had observed this in the traaxas engines mentioned above?
Moby

nitroexpress

Please enlighten us as to what is so special. Other than a carb that tends to vapor lock and a rod than tends to break, they seem run of the mill.

mobydickk

So how would U go about "burning more fuel and/or burn the fuel more efficiently"?
Moby

mobydickk

Since U brought up [2} items that were not part of the original question, I shall address these first.
Vapor lock? In my many years of being apart of the small engine hobby, I have witnessed hundreds of different engine brands with,"carb related vapor lock simply due to, "operator error"
Rod tends to break? This one is very easy to explain, pick the engine brand, and or size, .049,.051, 090,.12, .15, .17, .18, .19, .20,.21,.25, .26,.27, .28, .29,.30, .35, .36, .40, .45, .49., .60, .61, .65, .67, .69, .77, .80, .84, .90, .91, .94, 1.00, 1.01, 1.10, and I have personally seem rods break on all these engines due to, "operator error".

In regards to the original question regarding the Traaxas 2.5 and 3.5 engines Xpower, and also having a unique manufacturing design, these engines are both a long stroke and a short stroke engine.
Consider yourself enlightened!
Moby

nitroexpress

Besides disagreeing with your response to item one and two, you need to explain yourself a bit further regarding the long stroke/short stroke claim.

I'm not enlightened. I'm mystified how anyone could make such a claim. There is nothing unique about their design.

Anthoop

How would I go about making an existing engine more powerful? Alter the timing...lighten components...change the pipe....change the fuel...change the plug...change the head clearance/modify the button.
When designing an engine there are a whole plethora of options. High performance engines in general use higher grade materials and manufacture.

1QwkSport2.5r

Using a turbo or Nelson plug alone is good for 500rpm too.

mobydickk

If U could not do any of the items listed above, and could not alter any of the engines internal components, explain the quickest and easiest change to make more an engine produce more power please.
Moby

mobydickk

You replied that U "disagree" with my post regarding "operator error", as to what causes carb vapor lock and rod breakage. Perhaps U can explain why U disagree and what data U are using in your conclusions.

Regarding my post "traaxas 2.5 and 3.3" engines that are both a "long stroke" and a "short stroke engine, if U have not studied these engines enough to have all of the data on these 2 engine parameters, that would explain why u are mystified. What I have posted about these engines is not just a claim, or something I made up, it is something very easy to understand when U have all the data at hand.
Moby
BTW, many years ago a man named duke fox, released a new control line 36X engine for slow and fast combat that was also a "long stroke", and a "short stroke engine", no claim, just facts!

nitroexpress

You haven't provided any data to back up anything you've said. That being said, back in the day I had a Fox CS and used it for control line combat. They were never claimed to be long stroke/short stroke.
One of my first RC engines was the TRX. After it broke a rod during break in, I researched the problem. Rod breakage can be caused by user error, but the shear mass of TRX breakages was discussed on all the forums. Sorry you missed it. The problem even prompted Davis diesel and others to produce HD TRX rods.

Anyway it's clear you're a Traxxas fanboy. That's cool. I'm not. Enjoy the cool-aid. I'm out.

Anthoop

Add more nitro to the fuel.

1QwkSport2.5r

The 3.3 engine has a 15.1mm stroke and 16.8mm bore which makes it a bit over square and a short stroke engine. The 2.5/R has a square bore/stroke ratio at 14.75mm each.

The 3.3 is a short stroke engine and typically this means its a low-mid rpm engine as compared to the 2.5 which is not a short stroke or a long stroke engine. I don't have the exact figures in front of me but the 3.3 is timed a little better than the 2.5, roughly 153* in the 2.5 and 167* in the 3.3. I can double check later but it doesn't really matter much IMO.

mobydickk

That was {1] of the items U listed in post #9, so without changing any of the items U listed, what is the easiest way to make more power?
Moby

mobydickk

A question for U, have U ever replaced the piston and liner in the 2.5 or the 3.3 Traaxas engine?
Moby

1QwkSport2.5r

No, I've never needed to. Haven't been able to wear one out yet. I've had 1 - 2.5r and 3 - 3.3's. Mine all ran pretty well. The 3.3 really likes 30% nitro.

Anthoop

Clearly I do not understand what you are asking.
You want to know how to make an engine more powerful...but I have to think of something other than the things I have already listed and I am not allowed to change anything?

On2_n_On4

?? "operator error" ??

Next edition

Shave the cylinder head port and polish,drill your carb jets out slightly ohhll right.

mobydickk

Anthoop
I would agree with your post, "add more nitro to the fuel", however this was suggested in post #10. I was asking as an informational thought process on the quick and easy way to increase horse power with a quick and simple changing to a larger carb.
I am posting some engine data from my software program on the traaxas 3.3 engine, a lot of numbers to look at, the time study is great for understanding what actually takes place during 1 complete revolution, and how fast every thing happens..
Moby
Date 03 21 2011
engine Traaxas 3.3
serial # 321
practical RPM 31000
engine bore 0.665
engine stroke 0.578
rod length C to C 1.118
max rod angle 15.0
exhaust swept 0.428
exhaust duration 159.6
boost intake duration deg. 115.1
boost swept stroke total 0.522
transfer swept stroke tot. 0.501
head clearance in. 0.015
head volume cc 0.19
compression ratio 9.3
rotor open in.tol/top 0.587
rotor open degrees ATDC 216
rotor close in. tol/top 0.250
rotor close deg. ATDC 65
rotor duration degrees 209




timestudy @ 31000 RPM in seconds
exhaustexchange time 0.00086
intakeexchange time 0.00068
rotorexchange time 0.0113
optimalcarb size in. .321

mobydickk

The rod lengths on the traaxas 2.5 and 3.3 are same,1.118, strokes are the same, 0.578, I do not understand how U say one engine is a long stroke and the other is not when the have the same stroke length?
I have included my engine analysis info for the 3.3
moby

Date 03 21 2011
engine Traaxas 3.3
serial # 321
practical RPM 31000
engine bore 0.665
engine stroke 0.578
rod length C to C 1.118
max rod angle 15.0
exhaust swept 0.428
exhaust duration 159.6
boost intake duration deg. 115.1
boost swept stroke total 0.522
transfer swept stroke tot. 0.501
head clearance in. 0.015
head volume cc 0.19
compression ratio 9.3
rotor open in.tol/top 0.587
rotor open degrees ATDC 216
rotor close in. tol/top 0.250
rotor close deg. ATDC 65
rotor duration degrees 209




timestudy @ 31000 RPM in seconds
exhaust exchange time 0.00086
intake exchange time 0.00068
roto rexchange time 0.0113
optimal carb size in. .321

1QwkSport2.5r

Two things. First, you shouldn't post the same information in two posts in a row. Second, I couldn't pull my own engines apart to measure them so I was going off of specs I sourced from the often wrong internet. I measured my own engines before posting this. I'll edit the specs I posted previously to reflect the closer figures I obtained today.

The 2.5 has a 1:1 bore/stroke ratio at 14.75mm(.580") each approximately. The 3.3 is over-square with a bore/stroke ratio of 1.10:1; the bore is 16.8mm(.660") and stroke is 15.1mm(.590") approximately. What separates a long stroke engine from a short stroke engine is the bore/stroke ratio. Bigger bore than stroke = short stroke; smaller bore than stroke = long stroke. So my previously posted specs for the 3.3 are wrong; it is a short stroke engine which would lend it to be a low-mid rpm engine. I did not figure the head clearance in because I didn't have time.

2 engines can have the same rod but the wristpin height can be different as well as the fact the 3.3 uses a different crankshaft than the 2.5 to boot.


It's been shown through Dyno tests that the 3.3 makes around 0.9-1.0hp on 30% fuel. Making much more power is going to require some big timing modifications, compression adjustments, and cylinder head modifications at minimum. For the time it would take, you'd be better off buying a better engine.

Anthoop

A larger carb. will not necessarily make it produce more power...more nitro will.
Other than that, as said above, other alterations will give more power. Changing the carb. would only be necessary if it is inadequate/poor in the first place...and that I do not know.

mobydickk

So how does increasing NITRO percentage actually make more power?
moby