06
The turbo used on the mountune GRC engine is a variation of the legendary Garrett TR30R Motorsports turbo.  The TR30R uses bespoke mountune wheels optimized for use with high boot and a lot of inlet restriction due to the mandated 45mm restrictor. mountune also speced an exhaust housing with a larger A/R for less backpressure over the previous OMSE spec turbo.  It features lightweight thinwall non containment compressor and turbine housings.  The compressor housing is made of magnesium while the exhaust housing is cast Inconel.  The center section is not water cooled and has been cast from thinwall iron for lighter weight.  The wheels spin on ceramic ball bearings for low friction and fast spooling.  The exhaust housing is open single scroll and is fed from a 4-1 tubular header with a large water cooled TiAL wastegate. Antilag creates a lot of heat so the wastegate must be water cooled to live.  Unfortunately, it's hard to see a lot of this trick stuff going on with all of the heat jacketing in place.  The turbo weighs only 9 lbs due to all of the attention spent on weight reduction while your typical stock turbo for an Evo X for instance weighs around 22 lbs!  In this picture you can also see the cylinder head external water passage for the cross flow cooling system.
The restrictor is carefully made with its contour optimized using CFD for maximum air flow.  It securely bolts to the front of the turbo. The turbo sucks air from a shielded airbox in the passenger side nose that contains a large K&N air filter.
The Pectel SQ6 fires the NGK M14 racing plugs with the aid of Denso direct fire coils which are sourced from another OEM application.  We think they are Honda CBR type coils.  The coils have their own internal igniter so they can be fired directly by the ECU.  Direct fire is the only way to go in super high boost applications like this.  Under load the engine runs about 20 degrees BTDC.
The mountune intake manifold is pretty interesting.  The intake plenum is fed by a tapered tube from the intercooler that feeds the plenum chamber via slots between the tube and the plenum.  This was found to feed all 4 cylinders more evenly with the low and small volume plenum needed in the tight space between the head and the shock tower.  The arrangement you see here on top of the plenum is the 5th throttle which controls air for the anti lag system.  The valve in the 5th throttle allows air to bypass the throttle plates where it is mixed with injected fuel and burned to keep the turbo speed up while the throttle is closed.  The ECU greatly retards timing while antilag is operating to both increase exhaust heat to drive the turbo and to keep the engine from making torque while the throttle is closed.  The antilag is so effective that sometimes traction suffers due to the extra torque the system can create. Since traction control is not allowed in GRC, the anti lag system is very tunable for the conditions.
The mountune intake manifold has individual throttle plates for each cylinder for best throttle response.  The intake also features two individually staged injectors per cylinder spraying Sunoco 260 GT Plus fuel for best throttle response and best anti lag control.  The rules require that the throttle be manually controlled so throttle actuation is by acable.
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Comments
cbgoding
cbgodinglink
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.
cbgoding
cbgodinglink
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
jeffreyball610
jeffreyball610link
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.
JR
JRlink
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?
mike156
mike156link
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.
spdracerut
spdracerutlink
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.
supergreddyrx
supergreddyrxlink
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!
Fabrik8
Fabrik8link
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.
spdracerut
spdracerutlink
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.
Rockwood
Rockwoodlink
Wednesday, March 04, 2015 9:04 AM
@ Khiem: Also, no need for throttles on a diesel... :)
SM_Clay72
SM_Clay72link
Wednesday, March 04, 2015 2:34 PM
Awesome article. Love the antilag setup. So simple, but tuning must be a fine art.
Neoart
Neoartlink
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.
Cheers.
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.
rawkus
rawkuslink
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?
induetime
induetimelink
Tuesday, June 07, 2016 1:47 PM
Great article! I love reading the in depth technical writing on well engineered machines.
engineered
engineeredlink
Tuesday, June 07, 2016 2:45 PM
Great Article!
ErikO
ErikOlink
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.
Anonymous User
Anonymous Userlink
Wednesday, August 02, 2017 11:30 PM
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