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Unread 08-10-2016, 07:10 PM
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Fair! Fair! is offline
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Default Re: Ford Focus RS Development Thread

Update for August 10th, 2016: It has been a a little over a month since our first post and the Focus RS has been put through its paces at a local race track by Vorshlag (MSR-Cresson), then it was raced at two different Optima/USCA 2 day competition weekends by the owner Todd (Charlotte and COTA). We have gained a lot of first-hand experience with this car and several issues jumped out at us, which we will share in this post. We will also offer up a few potential solutions to these issues.

When reading this, please understand that we are not auto journalists, looking to gain readership with a shiny happy car review and a few funny quips. There won't be a cup holder count, radio features won't be explained, none of that. We care about simpler things than car mag writers - we want to know how does a car go, stop, and turn in track and/or autocross use. Also, is it reliable on track, or does it overheat some system quickly? Are there any electronic gremlins that deter from the track experience, things like that. Honestly we're a bit jaded and have seen so many whiz-bang special new hotness cars that when finally tested on track, were a flop. And we've seen others that did all right. This RS seems in the middle of that range, so far.

While the RS is popular with the auto journalist types, it is also a hugely popular car on the internets. The Focus forum fanboys are extremely unforgiving of anyone saying anything critical about this car. There is a lot of special sounding jargon and internet mythology being associated with the Focus RS, but frankly I just don't buy into the hocus pocus.

This RS is just a car. It is a small-ish car with AWD (sometimes), decent (front) brakes, and a turbocharged 350 hp engine. It weighs a good bit, has a relatively small tire, and a bunch of it's weight is on the nose (59% front weight biased). Just so we are all on the same page, these are called: the facts.

There is no magic breakthrough technology on this car (except the RDU - see documents below - but it doesn't work well on track). Sure, the RS has adjustable shocks (cockpit adjustable twin tubes, circa 1990), a launch control "rev limiter" mode (which has been on many cars for years, and with as complex of a procedure this car has to set it, this has very limited usefulness), and there is active disengagement of the rear drive axle - which is not usually a good thing. Bill Caswell mentioned this "Torque Vectoring Rear Drive Module (RDM), which combines a differential and two hydraulically activated clutches to control the power distribution to the rear wheels" in this R&T article. He did some track driving in an RS which put the rear diff (admittedly very small) into thermal overload, which disengages the rear drive completely. Many others are seeing this same issue, including me at our test and the owner Todd when he drove it at Optima events.

In my track test in-car video (see below) I mention many times while driving the car on track that the car felt like it had no rear drive at all. "It just handles like a Front Wheel Drive car", and that was because the rear drive unit was disengaged almost the entire time I was on track. This isn't me being hyper critical, its a known flaw in the RS. I've driven many AWD cars (Subarus, EVOs, etc) on track in the past 15 years and never had this issue happen on another car, until the Focus RS. It was disappointing to say the least, and "rumor has it" that Ford is coming out with a diff cooler retrofit unit that you might want to add to your race prep budget if you plan on tracking your Focus RS.

In this post we also disassemble this car's suspension and brakes, to weigh and measure things. Again, to show the facts. Many items look correctly sized for the power this car has (front brakes), while others look woefully undersized (rear axle, driveshaft, halfshafts, rear brakes, wheel width, tire width, etc). Some of these judgement calls are indeed guesstimates made by our crew, which includes engineers, race car fabricators, and other race experienced folks. Take that as you will, but its all part of our honest assessment of this chassis after tearing it apart and racing it on track first hand.

We are not Focus forum experts, nor blind believer internet fan boys, and we don't have all of the answers (or special lingo) for the issues we noted on track. All we know and trust about this car are what we can see, measure, and test first hand. When driven on track at three different venues by two different drivers, this car's oil temps got very hot very quickly, as did the coolant temps. The rear drive unit seemed be disengaged constantly; if you ever overlap the gas and brake (which happens when you Left Foot Brake - which all experienced racers should be doing if they don't need to downshift in a corner) or if the rear diff fluid gets hot (which it does).

There are many things we feel are needed to make this car more reliable on track, and to catch up with similar AWD turbo 4 doors from the past 10 years. Sure, it might be on par with a current VW Golf R, but not a Mitsubishi EVO X or GR Subaru STi (which had similar prices when new). An engine oil cooler is a must do upgrade on the RS for track use, unless you drive like Mr Magoo or race above the Arctic Circle. The 235mm Michelin PSS tires are overwhelmed by the power level and WEIGHT that this car has on track. The lack of camber adjustment up front shreds the outer shoulders of the front tires, which are doing almost all of the work on this car. The stock dampers and springs - although adjustable - are still too soft for this car's weight and power, so you get a lot of roll/heave/dive even with not-soft 300 treadwear tires. Vorshlag has a set of monotube coilovers on hand to install on this car, plus we are designing the camber plates for use with those, to be installed in the coming weeks before another Optima event.

Ford isn't in the business of making and selling 100% indestructible track terrors - they never have been - and this one is no different. It needs help to deal with the higher thermal load of a turbocharged engine, and cool the undersized driveline components. So while we may seem critical of this car in this post, know that we are pointing out the flaws we see - like we do on all cars we dig into this far. We're also committed to fixing or minimizing those issues with more track-worthy components, as time and budget allows. We end up needing to do this for almost every new car we encounter.


After the brief "intro" post on July 8th we had a chance to really dig into this Focus - by taking it apart and measuring lots of things. Our intent was to see what this car was capable of, and checking the potential for a camber plate design that utilized the OEM springs and struts. We also wanted to measure to see potential for wheel and tire width increases, brake cooling, engine cooling, etc. There were several eye opening discoveries which we have detailed in the pictures below.

After getting the car in the air we started by looking at many things underneath, under the hood, and then dug further. Let's start under the car.

The RS front undertray is a hodge-podge of scoops and shapes...

This unusually shaped, extremely non-flat fabric/plastic front undertray has several NACA scoops to help direct air to hot things underhood. This would be a decent design if this fabric panel wasn't so flimsy and non-flat. We will look at a smooth bottom aluminum undertray (and short splitter) with the NACA ducts added as needed.

The diameter of the driveshaft that feeds power to the rear differential, or as the fanboys call it the "Rear Drive Unit" (RDU), is remarkably small. The section above right necks down to the size of my finger. How does this transmit "up to 70% power" of 350 hp to the rear wheels? Doesn't add up.

Not to mention the Rear differential itself, which is painfully small in the RS. This is the size of what you'd expect to see in a side-by-side or ATV that has a 500-750cc engine. Not exaggerating here; this differential housing is small. I've never seen a car with any sort of rear drive that used an axle this small in 3 decades. It is no wonder it overheats and disengages the rear drive, to protect this differential from damage.

Some light reading from Ford documents that explains the complicated controls and overtemp protection on the RDU

After some digging through Ford documents, turns out this car doesn't even have a differential unit at all. There are electronically controlled clutches in the center diff as well as one for each rear drive axle. There are a network of computers, hydraulics, and robots controlling torque to each wheel. Lots of fancy doo-dads that are neat on paper, but terrible in practice. Hopefully there are some industrious folks who can crack the code and reprogram this unit to work better for performance driving.

This images above show the rear axle housing and rear suspension from a 2008 EVO X, which we spent two years tracking and autocrossing with. The differential housing looks like a similar shape but is substantially larger in person, and the rear suspension has aluminum multi-link arms. Just wanted to show what was available 8 years ago in AWD 4 doors.

The Focus RS exhaust system is oddly shaped around one of the center bearings of the THREE PIECE rear driveshaft. Yes, this subcompact car with a 104" wheelbase, has a 3-piece rear driveshaft. Which is a bit nutty given the length, but that seems to be a theme in this car. The exhaust is smashed nearly flat there, but there is ample room to leave it full size there. The aftermarket can and will fix this.

Sure enough, Magnaflow has already responded with a better exhaust routing, shown above. No smashed section, no problem. Ford does this exhaust smash trick on a number of their cars, and it is mind boggling.

The rest of the factory RS exhaust isn't too bad, just a bit on a small side for a 350 hp turbo car. There is a bit of a gimmick feature out back - a computer controlled exhaust bypass valve which can bypass the muffler. Hey, even the Corvette Z06 has this. But it seems that some RS tuners are using this and some "tuning tricks" to make the exhaust "pop" and burble. To me this is akin to adding an exhaust whistle... If I see a tuner bragging about how they add this "feature", I will label them as a clown. #BubRub #WooWoo

One of the worst features of the rear suspension is this trailing arm torsion blade. This is a 1960s-era design used on the VW bug, where you use a flat spring steel arm that can accommodate the suspension arc by twisting. This arm is needed to locate the suspension fore-aft during travel. Massive rubber bushing up front also allows for all of this twist. That front bushing should get a spherical. You only do this type of rear suspension to save money.

The rest of the rear suspension is heavy, stamped steel bits. Not an ounce of aluminum anywhere back here. This seems to have been done for cost savings. I would expect more from a nearly $38K car, but I guess I'm picky. At least they improved on the janky rear swaybar endlink design used on the Focus ST, but that is about it.

This Focus is made by the same company that designed and built the S550 Mustang (shown above), which has an independent rear suspension light years ahead of the Focus - and which can take real power to a properly sized rear differential. Aluminum is used on the throughout Mustang's rear suspension to save weight. And while some of the GT350 Mustangs (non-track pack cars) are seeing differential overtemp issues on track, it seems to be a programming glitch. This only affect the small portion of these Mustangs that even have a temp sensor in the rear differential housing. We've seen S550 Mustangs being abused on track for years with no long term negative effects.

Engine bay in the RS is the definition of "tight". There's not a whole lot of space for a turbocharged 2.3-liter four-cylinder and transaxle that sends 350 hp and 350 lb-ft of torque to all four wheels. The bulk of the drivetrain is in front of the front axle centerline, which explains the 59% front weight bias. The Subarus and EVOs suffer from the same thing - they all tend to sit around 58% or 59% front bias.

Ford does the RS no favors by putting a full sized battery in the cramped driver's side corner of the engine bay, either. I'm sure they had their reasons, but this would be something I moved to the trunk area on even a semi-serious build.

The best part of this car, to me, are the front brakes. The calipers up front are an OEM style Brembo 4 piston matched with beefy rotors. Lots of brake capability for a Subcompact car, and I we will talk about their track worthiness below. The front brakes are one of the few things on the RS that are matched well with the 3450 pound tested weight.

Now the calipers and rotors aren't anything magical - no co-cast aluminum brake hats or radial mount calipers - just a properly sized, OEM style 4-piston Brembo solution and decently sized iron rotor. Not gigantically silly or undersized, but just right. The front rotor weights and measurements are shown above. They are also not big enough to justify a 19" wheel - we could fit 17" wheels over these front brakes. Ford's 19" wheel choice was simply a fashion statement.

continued below

Last edited by Fair!; 08-11-2016 at 02:34 PM.
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