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Thread: Basher Build from a Racer's Perspective- Mugen MBX5R Prospec

  1. #11
    Junior Member
    Join Date
    Aug 2011
    Location
    Playin in the desert with lots of suspension travel and too much horsepower, Arizona
    Posts
    12
    Just a quick note on this build, I finished this a few weeks ago, and copy pasted the build from another forum I am on, so if it says that I "just ordered" something or "did this and this yesterday", it's been just a little longer than that, but only by a few weeks. Hope everyone enjoys reading about this build as much as I enjoyed building it!

    And a 15 tank report card on the Werks B5....
    (Rating system of 1 through 10, 10 being the best)

    Initial Impressions/Packaging - 9
    -This engine comes out of the box looking like a champ, and the massive billet cooling head is the first thing that caught my eye. It is well packaged, but the engine DOES NOT include an instruction manual, and there is a reason for this... According to the Werks B5 thread on RCTech, Werks believes that 4 different racers will give you 4 different answers on tuning, needle settings, etc, so to prevent confusion and risk of engine damage by providing needle settings that even as a baseline may be completely wrong for one person's application, Werks does not include this information. They preset the carb to a rough baseline, then it's up to you as the nitro RC hobbyist to do the rest. This is not an engine for beginner tuners, even though it is extremely easy to tune and break in, the lack of baseline settings could be bad news for newbies. If you know how to tune a nitro, and know the general stuff like how your air to fuel ratio is really what you should be tuning in conjunction with your LSN and idle speed and that the HSN controls the main flow of fuel to the carb and whatnot and have owned a few nitro engine, you should be fine with this engine. But at $200, for some this is a steal deal and for others it could be alot of money, if you are not 100% confident in your tuning abilities, I wouldn't recommend this engine. If you are 100% confident in your tuning abilities, by all means get a Werks B5, best bang for your buck power for the intermediate to advanced nitro enthusiast!

    Pre-break in tear down and rebuild/Impressions of engine internals - 8 & 10
    -As with any nitro engine you should always pull it apart before break in to make sure there are no shavings inside from the manufacturing process. Even super high end engines are not immune to metal shavings, it's better to be safe than sorry, and I probably had a chance of being sorry if I didn't take this engine apart, as I did find one rather large metal shaving stuck to the cylinder wall, as well as a loose casting bur in the exhaust port. They may not have harmed the engine a bit, or they may have, but $200 is a good bit of money, so why risk it when it only costs maybe 30 minutes of your time to do a tear down and inspection. Other than those two shavings/burs, I found no other debris in the engine. The tear down went very smooth, no screws stripped and I was very impressed with the quality of this engine. As shown in the pictures a few posts up, the conrod of this Werks is as big if not bigger than a Picco P3-28 conrod, talk about beef! The crank looks nicely machined, as does the piston and sleeve. The carb is aluminum with a thick composite insulator around the base neck. 10 out of 10 for Initial Quality Impressions of the internals.

    Break in and beyond - 10
    -The Werks B5 .21 does not have a ton of mechanical pinch from the factory, but that shouldn't scare you away, it's actually a good thing, less mechanical pinch means less stress on the crank/conrod/wrist pin/piston/bearings. After break in (currently sitting at around tank 15), I cannot turn the flywheel much past where the piston goes above the exhaust port (where your compression ratio measurement would start from), and from how it feels, I would say that I can't turn the engine over farther by hand because the compression is so high, not because of insane mechanical pinch, as the piston does not stick or feel like it's dragging along in the sleeve like it does in an engine with lots of mechanical pinch. Anyway, to put that in a shorter form, this engine has lots of compression, so much so that I cannot turn it over with it in the buggy. Break in was easy with this engine once I figured out my rough idle gap and LSN. I had to preheat it with a heat gun to get my starter box to even crank it over (4S LiPo powered twin 550 motor OFNA box at that!), but it fired just a few bumps after it was primed. For a plug I used O'Donnell hot plug (This is a turbo head engine, unfortunately I don't think there is a standard plug head button option out there), and the hot plug was only for break in to get the temps up, but I couldn't get it much past 150* so I had to use aluminum foil and a sock around the head to get it up to 230/240* (my personal temp preference for break in). Too low of temps during break in will cause an engine to lose compression because it's not expanding enough and wearing too much off the piston/sleeve wall, so break in this engine on a hot day and put a sock of the head to get it up to temp. For the first tank I was after a smooth steady idle but still on the rich side at the LSN, and once I achieved that I let the engine idle on the box for 2 tanks, shutting it down when it got up to temp. For tank 3 and 4, I started doing figure 8's and started leaning the tune a little more (still with a sock over the head) to keep the temps up and so it wouldn't stall out, and still repeating the shut down when up to temp, let it cool completely, then repeat. I did this for tanks 3 through 7 (probably a bit much but that's just my personal preference). After that I started giving the engine more throttle, but not winding it out just yet, so tanks 8 through 12 were with a tune very close to a normal race tune, but with a low smooth and steady idle. Tanks 13 through 15 are at a full race tune but I am not going quite all out with this engine yet, any full throttle is in short bursts.

    I am using the stock 7.5mm carb insert/venturi, a Dynamite 086 pipe with a smooth flow round header, Byrons Race 3000 30% nitro, factory head shims (and it's shimmed tall! 2 thick aluminum shims and 2 thin copper/steel shims), Hot glow plug up until tank 8, then switched to a medium plug and adjusted the tune accordingly, and stock gearing for this MBX5R buggy. My clutch setup is a standard Mugen 3 shoe with an aluminum fly wheel, OFNA 7075 aluminum shoes, non vented 13t OFNA clutch bell, two 1.0mm springs and one 1.1mm spring. This engine is a torque monster though, it throws this buggy around like a rag doll and the short bursts of WOT I've done so far show that it's insanely fast, and could be even faster without adverse side effects by going up 1 tooth on the clutch bell, this engine easily has the torque to handle that. The runtimes with the stock 7.5mm venturi are also very impressive given the power that this engine has, I am averaging around 12 to 13 minutes just bashing it around the yard but remember that is with a fairly large venturi and it's not the same kind of continuous driving like racing, so the track runtimes will probably be a bit shorter.


    Overall rating with this engine thus far, factoring in ease of tuning, quality of components, initial impressions, and comparing it to all of like 3 other .21's that I have owned, I rate it a 9.5 out of 10 as a budget racers engine and 8 out of 10 as a basher buggy engine (lower rating as a bash engine due to not being nitro newbie friendly).

    I will post another short review like this once I get a full gallon on the engine, which should be about when it really starts waking up and making ALOT of power.
    -Chris
    My Race/Bash Rigs ~ Mugen MBX5T Prospec Truggy / MBX5R Prospec Buggy - Picco/Werks - ACE~XP - Fioroni - Reckward Tuning - King Headz - JConcepts/Proline

  2. #12
    Junior Member
    Join Date
    Aug 2011
    Location
    Playin in the desert with lots of suspension travel and too much horsepower, Arizona
    Posts
    12
    No response to this? Kind of disappointing, was expecting a bit more from a smaller tighter knit forum like this.
    -Chris
    My Race/Bash Rigs ~ Mugen MBX5T Prospec Truggy / MBX5R Prospec Buggy - Picco/Werks - ACE~XP - Fioroni - Reckward Tuning - King Headz - JConcepts/Proline

  3. #13
    Senior Member
    Join Date
    Apr 2011
    Location
    Ontario Canada
    Posts
    110
    Wow! Very detailed build. For me, I learn a couple things about nitro cause I am a nitro newbie. Thanks!

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