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what is the benefit of the 'flat plane crank' feature?
the crank is significantly lighter than having every cylinder spaced 90 deg apart, vs flat plane which is 180 deg apart. So the engine can rev a lot higher in a flat pane config. Drawback though is the engine isnt as smooth and has higher NVH as cross plane fires in a balanced order. Cross plane has more frequent firing orders so it has higher and earlier torque. The power cycling is different as well as a so the engine has a different sound, thats why the GT350 sounds very euro exotic which use this same type of crank design.
the crank is significantly lighter than having every cylinder spaced 90 deg apart, vs flat plane which is 180 deg apart. So the engine can rev a lot higher in a flat pane config. Drawback though is the engine isnt as smooth and has higher NVH as cross plane fires in a balanced order. Cross plane has more frequent firing orders so it has higher and earlier torque. The power cycling is different as well as a so the engine has a different sound, thats why the GT350 sounds very euro exotic which use this same type of crank design.
Ford stated that they equipped the car with a HARMONIC BALANCER to mitigate the excessive engine forces caused by a flat plane design.
Anyways, here's an interview I got from Mustang6G.com forums =)
Mustang6G.com Q&A with Jamal Hameedi on the new Shelby GT350 Mustang
PRODUCTION:
Q: Do you expect it to be a limited production?
A: It will be about the same as a GT500.
Q: Will there be as many built as customers want?
A: …Up to a point.
WEIGHT:
Q: Is the GT350 lighter than the base GT?
A: Yea, we’re not really talking curb weight today, but there was a lot of light-weighting. Much of it went to offset all the mass that we added in terms of power, brakes, etc., but we also went beyond that too.
Q: So you’re optimistic that…
A: Yea, I’m not going to tell you. [laughs]
ENGINE:
Q: Is it dry sump?
A: It’s not dry sump.
Q: Is it direct injection?
A: No.
Q: Where do you get the extra 0.2 liter displacement
A: It’s all bore. It’s got plasma sprayed bore lining. Same lining coating as the 2013 GT500.
Q: Better breathing with flat planes?
A: It’s the rotational inertia that it reduces and also from an exhaust standpoint because you’re going side to side, you’re never disturbing the next cylinder’s firing.
Q: And mass reduction on the crank right?
A: Right.
Q: Where is the crank made?
A. It’s mostly in-house.
Q: You guys forge the crank and machine it yourselves?
A: Yea, there’s bits that are forged…
Q: This is a pretty big motor for a flat plane crank (big displacement). What have you done in terms of crankshaft damping?
A: There’s almost 30 things we did (outside the block) to compensate for it. It’s going to be a whole other story on how we did that.
Q: Challenges with emissions compliance with a flat plane crank?
A: It was harder than usual.
Q: Tell us about the variable loading exhaust valve?
A: It’s got an electric valve. So the valve, depending on what driver mode you’re in, the valve will either be open all the time (track mode) or it will open under certain conditions.
Q: Is it dependent on RPM or back pressure?
A: It’s electronically controlled so there’s algorithms in there that turn valve on in the right point in time.
Q: How much were you able to share with the 5.0L?
A: There are little common parts (i.e. things in the valve train), but it’s pretty much an all-new engine: new heads, new casting, new intake, new crank, new pistons, new rods, new halfshafts.
Q: There were rumors this engine was nicknamed Voodoo, is that the name it’s going by?
A: That was its nickname, yes.
Q: Any chance of seeing this engine in anything else?
A: Right now it’s just in this car. Which we’ve always done, just like the Trinity engine in the GT500. The GT500 was the only place you got the 5.8L.
Q: So it’s exclusive for now at least?
A: Yea.
Q: Is factory top speed software-limited?
A: No, it is drag-limited.
Q: How high does it go?
A: We’re not talking numbers today.
BENCHMARKS:
Q: What were your benchmarks for this car?
A: We had four cars that we bought. One was a 911 Carrera S — that was our main one. But we also bought a Ferrari California and that was mostly for NVH benchmarking. That’s the only flat plane crank front-engine car really out there. And then we bought a C7 corvette and also a Z28.
Q: Relative lap times compared to a Boss 302 around a race track?
A: Not really comparable. Way faster.. an order of magnitude faster.
SUSPENSION:
Q: What is the percentage of stiffness difference on the bushing between the GT350 and the standard GT?
A: Not that much. The bushings are different. The rate, the springs, the swaybars are different.
Q: Is the bushing changes primarily a handling thing or is it for NVH?
A: All for responsiveness and handling.
GEARBOX/TRANSMISSION:
Q: Tell us a little about the gearbox/transmission.
A: It’s a Tremec 3160 transmission gearbox that’s been modified fairly significantly to cope with the demands of the flat plane crank engine.
Q: What about the fly wheel and the clutch?
A: It’s got a low inertial dual mass flywheel and two 15-mm dual disc clutch.
WHEELS/BRAKES:
Q: Why black wheels?
A: Actually there’s a reason for that. The brake pads we use, they create so much dust and customers just hate it. You drive the car once with clean wheels and they are dirty after a short drive. So that’s why we got dark wheels.
Q: Why no carbon ceramic brakes?
A: I think you’ll find out later that affordability was a big part of this car.
Q: So keeping price down was a big part of that?
A: Yes. That was a priority with this car.
MISC:
Q: Is it meant to be a Boss 302 replacement or a GT500 replacement? Where is it positioned in the lineup?
A: It is its own beast. Just because the whole flat plane crank is so different than anything we’ve done and anything that’s out there.
Q: In terms of the body panels, how much does it share with the GT and how much of it is new?
A: From the A-pillar forward it’s all new. The whole rear diffuser is new. Rear quarter panels are the same.
Q: Will this be a platform for the GT500?
A: The car has got really good bones so…
Q: How much fun was it working on this?
A: It was awesome. I don’t want to stop.
Had the distinct pleasure of driving the Shelby GT350 on the track yesterday (we had about 15-20 cars we were driving for a media day), and this was a gem. Superb power, handling, dynamics. Lustful V8 sound, and a supremely easy to modulate clutch.