Xcelorin is the Losi branded brainchild of parent company Horizon Hobbies - bringing the Losi brand into the world of selling elecrics isn't a bad idea and lends a degree of confidence to the product it wouldn't instantly have. 
Xcelorin have several products out with various scales and performance points being catered for, but the one were interested in here is their top-line 1/10th racing system, the Xcelorin S combo. 

The combo comes in several flavours, bundled with different wind motors - but we chose the mid-range 6.5 wind as it's pretty much ideal for most off road racing applications without being either too fast or too slow.  Indeed, there seemed to be a 'gap' in the motors, with no 7.5 or 5.5 - so if you want faster you'll have to plump for the crazy-fast 4.5, or if you want slower the 10.5 are the next best options. Still - 6.5 is ideal the 4WD wich is what I usually race, so that's what I chose.

BIG capacitor

Losi battery connector

11 bladed fan doesn't seem the best

The brushless controller itself came pre-wired to the motor with long cables whilst the battery wires came pre-wired with connectors that I'd not seen before - I assume Losi also make LiPo batteries which have similar connectors but since I'd be using 'normal' corally-style plugs I cut these off straight away as will most racers I suspect. The connectors actually do look very good - I just didn't have a corresponding connector for my batteries.

The ESC is fairly large but not really any larger than its competitors, with the odd exception. The unit does have a large external capacitor however - and this will need taking into account when mounting in your car. A black heatsink is topped by a fan to keep things super-cool.

The Xcelorin S has several options included to tune the ESC - three pre-set profiles are included within the controller which can be selected by holding the setup button on the power switch - 'Stock Race' which is meant for users in the brushless 'stock' classes to get the most from their motors (and is strangely the default setting).  'Modified', which doesn't have quite such an agressive profile but is meant for low-turn motors and high traction conditions we'd suspect.  Lastly there's the 'Off Road' setting, which has a lower motor timing and initial acceleration than the other profiles and should help get the power to the ground better in off-road & lower traction conditions.

Advanced Quick Setting Card

AQPC
As well as the built-in profiles, the settings can be changed with the included advanced quick programming card (AQPC). This retro-looking device is included to help with quick and simple trackside changes. So there's no scrambling around for the manual when you need to change a setting - nice! Not all the settings can be changed, but those that can are changed on the currently selected profile.

Things that can be changed with the quick setting card are:

Cut Off Voltage: Nimh - 2 cell lipo - 3 cell lipo

Braking (strength): 20% - 30% - 40%

Drag Brake: 8% - 12% - 15% - 20%

Motor Timing: 0 - 2 - 4 - 6 - 8 degrees

Reverse mode: Forward & Brake - Forward, Brake, Reverse.

Throttle limit: No limit - 80% throttle - 60% throttle

Advanced Quick Setting Card in action

USB interface
For finer tuning Losi also supply something that's starting to catch on but is still pretty unusual and therefore a bit of a talking point - a PC interface and setting program.

The combo is supplied with a tiny USB adaptor which takes the radio plug and converts it to talk via USB to the computer. A mini-CD is supplied with the software but if you've got internet access it's probably better to just go to losi.com and download the latest version of the software.

At the same time as grabbing the latest setting software, you can get the latest 'firmware' from losi.com and this is probably a good idea.

The early Xcelorin's suffered some problems which were cured with later firmware additions - so it's best to make sure the ESC has the latest firmware before setting it up.

The tiny USB connector is connected to the ESC receiver plug and is powered during the setup / updating by the USB lead so doesn't need to be plugged into the battery pack.

With the ESC connected and the software installed on the laptop - I was ready to start playing with the settings. There's not really much more to it - it really is that simple.

The main page on the setup program enables fine tuning of all the previously mentioned setup options, with some extras like Legacy/2.4ghz, Reverse motor Rotation and Neutral Deadband among others.

The standard screen on the Xcelorin setup program.	Throttle curve is liner as standard.

There's a button for reading the settings from the ESC and another for sending them back once modified. Updating the firmware on the ESC is also done via the program but sadly you need to check on the Losi site and download the file seperately if you didn't have the latest version - probably not applicable to any newly bought systems.

Don't try this at home kids! You can't make pretty pictures with the Losi throttle curves - but you can make the ESC impossible to control if you desire.	Super smooth low end - a bit extreme, but it illustrates the point. The 0-100 is the travel of the throttle - so low down it's accelerating very slowly, then ramps up toward the end in this extreme curve.

Throttle and brake 'curves' are also available for editing in the setup program - if you're completely insane you can draw a mountainous landscape and see how that effects your lap time. For the sensible among us though, it's best to either leave the setting linear (a diagonal line, ramping up the speed as it goes) or introduce a slight curve.

I let the throttle curve as a linear line - if I need a throttle curve I find it easier to change settings on my transmitter, but the setup option is there if you need it.

The 6.5 motor supplied in our combo is a real gem. There are some pretty fancy looking motors out there these days and this isn't at the top of the looks list - but it certainly performs well enough. The neodymium sintered rotor is ~12.3mm in diameter and has serious torque without being over the top and a near-perfect top speed for 10th off road racing.

The motor came pre-wired to the ESC but the solder tabs make it easy to remove / attach the wires when needed.

Shiney sintered rotor looks like a quality thing

Ok, I guess it's quite pretty really, in a blue way.

The controller was just barely too large to fit.

Now that's a big capacitor

The losi Xcelorin system isn't the biggest around but it's certainly no micro-sized unit. The large heatsink and fan raises the height along with a fairly large footptint. I wanted to install the unit and test it in a couple of cars. The first install was the latest Tamiya TRF511 4WD buggy - a car with space constrictions to begin with so I knew it would be a squeeze.

With the full-sized steering servo it seemed like it wasn't going to be possible to install the system and clear the layshaft - it was really very close indeed but the heatsink fouled on the large slipper spring. If it were the smaller diameter spring from the 501X it might have fit - it was that close. Oh well - plan 'b' - I installed one of my low profile servos which I'd previously run in the 501X to allow some extra room. The large capacitor slotted in under the layshaft alongside the ESC no problem.

Calibrating the Xcelorin system really couldn't be easier - with the wheels off the ground you simply turn it on whilst holding down the small setup switch attached to the main power switch. Grab some throttle - apply some brakes - let go - and you're done!

I went with the standard settings available on the ESC - using the 'off road' profile, which felt the most progressive.

First time out with the Xcelorin S I wasn't entirely sure how the system would perform - my worst fear was that it might be some glorified 'basher' system and I really wasn't sure what to expect.  Because I was reviewing a car at the time I'd not had chance to drive the system at all before it was placed down on the track for practice. Thankfully my fears were unfounded and it instantly felt at home.  I put in several laps before pulling the car off to change the setup [of the car - it was too soft].  When I removed the body shell to switch the Xcelorin off I noticed the fan wasn't working!  what?! already?!  It turned out that the fan blades had become unseated and just needed pressing down, which thankfully brought it back to life.  I got talking to a local racer who had no shortage of love for his Xcelorin system but mentioned the fans weren't the best, so it seems it's a common problem.
I raced round one and I guess the heavy landings were the cause of the fan problem - but at some point in the race the same thing had happened and the fan wasn't working.  This was concerning to me since I was racing indoors with a fairly rapid motor and had no ventilation in the body since I wanted to keep it nice for photos!  Luckily I needn't have worried - the system was only slightly warm to the touch and a long-long way from cooking itself, not bad for a tight indoor track.

I qualified and finished 5th in the A final - the other drivers weren't far in front and I drove a flawless race, but they were just better drivers - what can I say.  Even using my old nimh cells the Xcelorin was seriously rapid and I had no shortage of controllable power - apart from when one pack of cells blew up mid-run of course.   The fan was a concern during the day - sometimes it would still be working fine after a run, sometimes not - but the ESC never felt stressed or overly hot so it wasn't a big issue on the day.

It's a shame when something goes wrong during a review - I've got to mention it as it's only fair to point out things. I tested the Losi system for a long time - in two cars, I've no excuse for that other than I'm sometimes a bit SLOW. So I gave the system a real work out and was only ever impressed by the feel and performance.

Then one wet club race day at a local track Bury Metro, I raced the first qualifier and finished 3rd in round using the Cyber10b. The car was going fantasticly well and as I completed lap one of the second qualifier the car stopped. It seemed the sensor had stopped sensing - the system didn't seem to be able to start the motor rotating without a helping hand. Oh dear - so it would give me a chance to test out that fantastic customer service I'd heard about at least.

Speaking to fellow racers who'd tried out the Losi system and especially those who'd tried some of the very early systems and had problems - they'd been sent back a brand new system within a couple of days.

I also tried the Xcelorin out in the HPI Cyber10B
A well-suited system for the car.

Big capacitor could be tricky to fit in some cars - but wasn't in ours.

I was really happy with the performance - with or without fan - of the Xcelorin S system. The sensored design ran cool and with really great control. I'm not big on making changes and I'm happy the system ran so well from the box that I'd never really need to go more in-depth with the setup. If you're running a more basic transmitter then the computer setup option could be especially useful - and it's a nice touch that both the advanced setup options are included in the box for those that want to fiddle.