An Inside Look at mountune's GRC Ford Duratec Engine!

by Mike Kojima

The current engines used in today's GRC Rallycross racers are some of the highest stressed production based engines in all of Motorsports.  Only Import Drag Racing engines see more stress and perhaps no production based race engines not even Time Attack engines are stressed for as long a period of time as Rallycross powerplants.

Breathing through a 45mm restrictor that limits power to "around" 550 hp, the mountune Ford Duratec puts out 625 lb/ft of torque.  Because of the restrictor, the Garrett Turbo pumps in 45 plus psi absolute of boost to make that power, generating an amazing 3200 psi of cylinder pressure.  To put this in perspective, this is more cylinder pressure than the Audi LMP1 Diesel!

To adapt a production based engine to survive in this rigorous environment requires some interesting engineering.  Also interesting are some of the engine's peripheral controls meant to provide the instantaneous throttle response needed from a modern AWD racer that must excel on both tarmac and dirt. 

Let's take a look inside mountune's Marvelous Monster Ford Duratec engine and see what makes it tick or at least stay alive!


The first thing you notice about mountune's engine is that it's longitudinally mounted.  The stock Fiesta is not AWD but to convert it, the engines must be switched to a north/south configuration. There's a lot of external plumbing on the engine and most of that is related to boost control and anti lag hardware.  The back part of the block is machined to allow the transmission to be mounted as close to the engine as possible and a few production based bosses are removed to save weight.

The original development of the Ford 2 liter Duratec engine was done by Olsberg MSE or OMSE.  OMSE has successfully campaigned the engine in Rallycrosss and a more restricted version of the powerplant in WRC Rally for several years. Ultimately, the engine had long term durability issues and not the greatest race reliability.  

mountune's involvement with OMSE began when mountune founder David Mountain met OSME bossman Andreas Eriksson at the 2009 Pikes Peak hill climb and struck up a deal to aid in the engine's development.  mountune started making some changes to the engine in the 2010 season and assumed control of engine preparation and development in 2011.

Since then mountune has made revisions to nearly very part of the motor to improve durability and performance including the block, crank, rods, pistons, head sealing, turbo, intake system, sump and ECU.


mountune's engine is based on the Mazda derived Ford MZR Duratec which is becoming the basis of many race engines from LMP1 protoype endurance racers, to WRC rally cars to BTCC Touring cars and open wheel stuff like the new Formula Ford and Super 2000. In mountune's variant, the block is the production Duratec while the head is a bespoke design by OMSE. While the engine developed by OMSE was fast mountune made many changes to make it fast and reliable.

One of the biggest changes that you can't see was in the engine control department with mountune going from what was basically a reprogrammed OEM SAAB ECU to a Motorpsorts Cosworth Pectel SQ6 unit. One of the most important features of the Pectel unit that greatly impacted reliability was advanced knock detection and suppression.  Although knock detection on tarmac is a pretty understood subject nowadays, on dirt, the vibrations from rocks hitting the chassis makes it much more difficult.  A lot of the secret stuff is the ability to resolve actual knock from rock impacts.

The Pectel also afforded higher resolution of the fuel and spark maps, sophisticated launch control and improved boost control strategies. The engine also features a dry sump oiling system and other features we will talk about later. 

mountune revised the block prep compared to the original OSME spec. The engine's block starts as a production 1999cc Duratec piece with an 87.5mm bore.  mountune pushes out the stock iron cylinder liners and replaces them with stronger nikasil plated steel pieces from F1 supplier Capricorn with a final bore of 88mm.  With an 84mm stroke (up from the stock 83.1mm), the final displacement is 2044cc. 

The original OSME block used gas filled o-rings for head sealing which proved to be problematic as there was not enough bore spacing to install them correctly, hence they were installed into a step in the bore where they were fully exposed to combustion pressure and the combustion flame front. This led to erosion of the o-rings causing them to fail early. 

mountune solved the problem by going to a 5-layer MLS gasket designed and produced by Elring Klinger.  The gasket consists of 5 layers of elastomer coasted spring steel that is deeply embossed with a stopper layer.  The gasket not only seals better but is also much more forgiving to slight variations in machining.  Converting from the o-rings to the MLS gasket has vastly improved the engine's reliablity. All of the head fasteners are replaced with 10 oversized ARP studs for improved torque and clamping of the head gasket.

The production Duratec block has really deep skirts which extend past the main caps.  Deep skirted blocks are very stiff and mountune exploits this with a special oil pan which we will see later.

Even with all the prep, the rallycross engine has a relatively short service life due to to the high boost pressures, combustion pressure and the rough operating conditions of rallycross.  The engines are rebuilt every 3 to 4 events even though the total mileage for a rallycross weekend is only 25-50 miles of running.

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Monday, March 02, 2015 7:26 AM
Which Saab ECU? Saab's are kinda well known for their knock detection/prevention in the euro tuning world. Granted, you have to use the expensive and saab coilpack (direct ignition cassette) for that to be functional.

But tuners have taken the t5 and t8 saab ecu's and coilpacks over 800BHP in europe.
Monday, March 02, 2015 7:36 AM
I mean I don't doubt that the pectel has a shitload more features, support, and reliability as well as a much faster cpu, but T5 was a pretty crazy factory ecu.

More info here: http://socalsaab.com/suites/Trionic5.pdf
Monday, March 02, 2015 8:08 AM
I'd like to know more about that main girdle thing. Looks like there's a lot more going on in there.
Also, perhaps Khiem or someone can explain crankshafts to us. I still don't know why we need all of those counterweights on a 4 cylinder engine. Isn't it naturally balanced? I'd like to know more about how crankshafts create vibrations and why they need balancing and dampening.
Monday, March 02, 2015 9:20 AM
The rear radiator....... its mounted in the trunk horizontally? Does it pull air up from under the car and dump it out the back? I didn't think this would be that effective with the lower pressure area under the car?
Monday, March 02, 2015 10:07 AM
They are Toyota corolla/Yaris coils. The EVO guys use them often. They have a very short dwell time requirement (~2.5ms) which means they have a very short charge/discharge cycle. While they are only like 50mJ coils, they deliver a VERY intense but short duration spark that is capable of very high voltages. IMO, it's the only way to go on a turbo motor. With N/A motors where charge density is much lower, something like a 100mJ LSX coil with a ton of discharge time makes sense as you want to make sure you hit fuel but can get away with 35k volts because the cylinder pressure at ignition is so much lower. With 45psi, retarded timing (late into the compression cycle where cylinder pressure is higher) and rich AFRs, you just need to make sure the spark happens at all (high voltage) and that it has enough heat to actually light it (high discharge current). If that happens...you'll hit fuel without concern so the discharge time can be short.

Very interesting on the crank stuff as many engines go down on journal size to reduce bearing surface speeds at high RPM. Makes sense though in something like this were revs aren't as high due to the restrictor and shear strength is far more important. Very surprised by the lack of damper though.

On the radiator, the cars aren't usually going at high speeds so they likely rely more on a very powerful fan instead of ideal aerodynamics. I think they also do it to get the radiator off the front of the car in an effort to protect it from damage during wheel to wheel comp.
Mike Kojima
Mike Kojimalink
Monday, March 02, 2015 10:52 AM
@jefferyballs610, Think of the pan as a bed plate that is also the pan in this case. Inline 4 cylinders have an up and down shaking moment. They also go through a second harmonic torsional whip are around 8000 rpm. This engine is under a lot of stress from combustion pressure, hence the large journals. The trend in NA engine development is to go to smaller journals to reduce bearing surface speed but this engine needs the stiffness. With a full counterweighted crank to handle the up and down vibrations and the big journaled stiff crank, the torsional damper isn't needed. mountune decided it was better to get rid of the reciprocating mass here instead of internally like what is trendy in race engine development now.
Monday, March 02, 2015 11:25 AM
The rear mounted radiator has a number of benefits. In this case due to the platform being front engine, mounting the radiator in the rear shifts the weight distribution more rearward which should make it more even and improve handling.

Having the radiator mounted back there as opposed to stacked up front with the intercooler improves the cooling of both. By separating the two, the airflow going to each is much higher. The radiator is getting air from the side vents just behind the doors. Of course, in the body slamming nature of GRC, it helps to have the radiator protected.
Monday, March 02, 2015 6:49 PM
Love the article. ITBs are autopornography. Usually have to splurge on Race Engine Technology magazine to see relatively current race engineering.

The second rail above the fuel rail is different in the two engines depicted. Is this to do with the cross cooled cylinder head? Also the plenum cover has a billet rail mounted centered over the runners. Is this for possible fuel injection into the trumpets? I'd love bigger high resolution pictures.
Thanks for the interesting tech!
Monday, March 02, 2015 7:23 PM
The rail in the plenum cover looks to be for showerhead injectors, yes. The second rail by the head is for some kind of uncontrolled liquid flow (no flow control for individual cylinders) and uses banjo fittings, so likely cooling.
Mike Kojima
Mike Kojimalink
Monday, March 02, 2015 7:40 PM
The pictures are two different motors on two different cars. The part difference you see are for minor developmental variants. Both cars were competing as of last season.
Monday, March 02, 2015 8:02 PM
Good stuff on the ecu and coils info guys! As for the intake manifold design, that was how Audi designed their manifolds for their old R8 Lemans race engine. However, it seems they have gone to a more standard, single plenum manifold design once they switched to diesel. I'm guessing they required more even flow distribution for the petrol engine and can get away with a more simple design for the diesel engine.
Mike Kojima
Mike Kojimalink
Monday, March 02, 2015 10:27 PM
The reason why they run this sort of plenum is that there isn't enough room for a normal well designed plenum.
Wednesday, March 04, 2015 9:04 AM
@ Khiem: Also, no need for throttles on a diesel... :)
Wednesday, March 04, 2015 2:34 PM
Awesome article. Love the antilag setup. So simple, but tuning must be a fine art.
Tuesday, April 14, 2015 9:23 AM
"Balancing" - jeffreyball610 " explain crankshafts - why we need all of those counterweights on a 4 cylinder engine. Isn't it naturally balanced? "

No - you confuse 2 different processes.
A Vtwin Harley crank/rods/pistons - is perfect balanced spinning assembly.
If crankshaft spun test on a bench. There will never be a spot it stops at freely.
Yet Power Pulse - shakes eyeballs out of sockets.

Boxer Engines - BMW/Honda Goldwing/Porsche is a Flat direct opposed power pulse balanced engine.

Crankshaft Assembly has to be a perfectly balanced w/i a gram.
Or it would self destruct.

4cyl Inline Power Pulse balance doesn't have wide overlapping pulse - still felt.
6cyl inline, the pulse is now a narrower overlap, quite smooth.
8cyl is prime example of best overlap smoothness.

The length of stroke is also involved, the shorter the stroke, the smoother,
but less torque.
Short stroke requires high RPM to create HP is the trade off.
F1 - heard screaming 10,000 RPM, are short stroke engines.
Harleys rods are 2 times longer. Low RPM High Torque monster - Low HP.
Mike Kojima
Mike Kojimalink
Tuesday, April 14, 2015 4:20 PM
Harley engines have a 112 degree offset and are infamous for having horrible balance.
Tuesday, June 07, 2016 1:25 PM
Any more details on the cooling system? Does this mean the coolant doesn't go from the block through the head? Are they each treated as individual circuits?
Tuesday, June 07, 2016 1:47 PM
Great article! I love reading the in depth technical writing on well engineered machines.
Tuesday, June 07, 2016 2:45 PM
Great Article!
Friday, June 10, 2016 10:52 AM
Another reason the radiator is mounted in the trunk is to keep it from getting plugged with mud if it rains. Many of the European tracks have much more dirt than tarmac on them. I believe this is also done on short course trucks for this reason.
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