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Old 05-18-2009, 05:19 PM   #1
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Default Mugen MBX5-T ~ Run a .21 or a .28?

I recently purchased a Mugen MBX5-T truggy with a BCE extended chassis, and now I am looking for an engine for it.


So after looking around, I found an engine which, from the reviews I read, is really good for the price. That would be the JPX.28
I plan on running it on 30%, which I have read produces more power, lower temps, but worse fuel economy. I was leaning toward a .28 mainly because of my tracks current layout, it is pretty tight and technical and I figured having the torque of a .28 would be ideal.

Now I was also thinking of getting a .21, the JPX.21
Since it is a .21 it will have better fuel economy on 30% than the .28 on 30%, and it will probably be a faster engine overall.
My main concern though is torque. With my driving style, I prefer a .28, and the track I race on, as I stated before, is tight and technical with not alot of run-up to the jumps, and I am not really sure but it seems like in that situation a .21 might not be a great idea?
I would put a tuned pipe on it for torque, and if that wasn't enough I would have to gear down some for more torque and that might cause me to lose speed.


So my main question is this, which would probably be better for my application? In a Mugen MBX5-T truggy, racing on a tight and technical track with not a huge amount of run-up to the jumps and I have a more aggressive driving style and like to "powerslide" around corners with plenty of power, running on 30%, running a torque tuned pipe, and I want decent runtimes (Somewhere in the range of 6 to 10 minutes).

I am still leaning toward the JPX.28 unless someone points out that it will get less than 6 minutes of runtime.
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Old 05-18-2009, 05:22 PM   #2
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21 hands down.
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Old 05-18-2009, 05:37 PM   #3
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if you go with a 28 its got more than enough power, most pros use 21's.
you dont need a low end pipe.
when we run the os28 we use the 5.5 rest. with 30% fuel and the os 2060 pipe which is great for fuel mileage/low temps and gives the big block more rpms.
if your thinking crazy low end motor/pipe/ unless its carpet high bite all your going to do is spin the tires.
with the 28 you need to go up on the center diff to keep it from balloning the front tires. 7/10/3 to a 7/20/3.
hope this helps, i never cared for the 28 but last weekend we put the 2060 pipe on and went up 1 tooth on the cb(28's dont turn the rpms on the straight that a 21 does) and i gotta say it was just too much fun.
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Old 05-18-2009, 06:15 PM   #4
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I just talked to a guy who races at my LHS, he said .28 seems to be the common choice for the track but I am still unsure. I just dont want to get an engine that is going to suck fuel like crazy, but still has great torque, but I guess I will have to make some kind of trade off.
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Old 05-18-2009, 06:44 PM   #5
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last year i ran a 21 in my 5t and it would make any jump my buggy could. i ran the ninja os jx21 with a 7 res on 30 % and i didnt even put a low end pipe on. i used the 2042 ninja(os 2060) but i should of tried the L header. the 28 with a 5.5 res gave me 8 min. many worry about fuel mileage when really a good pitstop is = to a wreck. get what makes you happy, the 21 is easy to go fast with and the 28 will just put a smile on your face.
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Old 05-18-2009, 06:47 PM   #6
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Quote:
Originally Posted by l3asher View Post
21 hands down.
X2
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Old 05-18-2009, 06:48 PM   #7
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if you plan on getting the 6t down the road a 28 will not be fun in the new light weight truck. in the buggies they are getting lighter and we are running 5.5/6 mm res.
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Old 05-18-2009, 06:50 PM   #8
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I have to say Allan's truggy was moving this weekend, had my head turning every time! Boy did he have a grin on his face too!!
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Old 05-18-2009, 06:51 PM   #9
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the two guys that are telling you a 21 may have a light quick losi 2.0 8t. the heavier 5t will be ok with a 28 but i would agree with them if i was putting it in a 6t.
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Old 05-18-2009, 06:54 PM   #10
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yep i liked the 21 last year but man i had too much fun sat, it was doing wheelies down the back straight.
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Old 05-18-2009, 07:08 PM   #11
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Quote:
Originally Posted by allan42r View Post
the two guys that are telling you a 21 may have a light quick losi 2.0 8t. the heavier 5t will be ok with a 28 but i would agree with them if i was putting it in a 6t.

the mugen is Not much different in that aspect....i race with alot of 5T's still and they perform just as well on .21's as mine.
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Old 05-18-2009, 07:16 PM   #12
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I run a Ninja JX B01 in my BCE 5T and i love it.. My home track http://www.rctech.net/forum/nitro-of...hester-ny.html always has the tightest layouts with the biggest jumps in this region and i have NO problem with lack of power. I'm running a .21 JX, 2042/2060 pipe with a p4 plug and an M2C clutch. I get around 10 mins run time.
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Old 05-18-2009, 07:29 PM   #13
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Well sorry if it sounds like I am going against most peoples word, but what Allan said about the .28 has really convinced me. I almost totally forgot about using carb venturi's/restrictors to tone down the power and increase fuel economy. And the fact that a .28 will put a big grin on everyone's face is very appealing.

And just wondering, but what kind of life could I expect out of one of those Jammin .28's on 30%? 9 gallons? And aren't they pretty much a Picco?
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Old 05-18-2009, 08:31 PM   #14
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Quote:
Originally Posted by Krawlin View Post
Well sorry if it sounds like I am going against most peoples word, but what Allan said about the .28 has really convinced me. I almost totally forgot about using carb venturi's/restrictors to tone down the power and increase fuel economy. And the fact that a .28 will put a big grin on everyone's face is very appealing.

And just wondering, but what kind of life could I expect out of one of those Jammin .28's on 30%? 9 gallons? And aren't they pretty much a Picco?


Yes a Jammin is a picco with a different color head basically....and .28's beat up on the drive train imo....your CVD's will not be very happy a couple gallon's down the road compared to a race .21...even with gearing up a tooth or 2 and trying smaller venturi's you'll find it's still too powerful for most any application...and gearing up also put's A lot of excessive stress on the clutch.
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Old 05-18-2009, 09:04 PM   #15
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Quote:
Originally Posted by Integra View Post
Yes a Jammin is a picco with a different color head basically....and .28's beat up on the drive train imo....your CVD's will not be very happy a couple gallon's down the road compared to a race .21...even with gearing up a tooth or 2 and trying smaller venturi's you'll find it's still too powerful for most any application...and gearing up also put's A lot of excessive stress on the clutch.
Yeah good point. Well I am still debating what to get, still leaning toward the .28 though since this truggy will see some bashing.
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