Trackaholic
Well-Known Member
- Thread starter
- #1
http://wot.motortrend.com/1409_ford_shelby_mustang_gt350_to_get_5_2_liter_flat_plane_crank_v_8.htmlI mentioned this to our technical director, Frank Markus, and he gave me back a virtual earful, “I’m highly skeptical that an engine of 5.0 or 5.2 liters could tolerate a flat-plane crank. All the examples I can find top out at 4.5 liters. The shaking force gets bigger and bigger with displacement. If you want power and quick-revving from a flat-plane crank (which needs no counterbalances and hence has way lower rotational inertia), you dial up the boost to whatever power you need. Balance shafts would almost certainly be required, and their mass begins to negate any possible benefit the added displacement provides.”
Oh boy. Time to do some pavement pounding, which in 2014 means lots of frantic emailing and text messaging. Remember, that a flat-plane crank V-8 is essentially two four-cylinders. Meaning that four-bangers are subject to the same limitations as flat-plane V-8s. Which is why, not that you’ve wondered, you almost never see inline-fours above 2.3-liters of displacement. Some of you may be wondering about the old 2.5-liter and 3.0-liter I-4s from the Porsche 924, 944, and 968. How’d they do that? By licensing balance shaft technology from Mitsubishi, that’s how. Rumor has it that Porsche’s still paying Mitsu royalties for said tech. Anyhow, can Ford do a 5.2-liter flat-plane V-8 without balance shafts? According to our sources, yup.
One source says they’re still working out the kinks. Another says that the kinks are in fact engine accessories. Ford’s solved the second-order vibration issue by attaching a big, honking vibration damper on the end of the crankshaft. That seems to do the trick. However, when testing the GT350 on the Nurburgring those same secondary vibrations backed a bolt out of the car’s starter, shutting down the entire electrical system while the car was going pretty fast. That’s bad. However, the SVT boys and girls have taken the necessary steps and have essentially beefed up the Mustang’s accessories for GT350 duty. We hear they’ve had one spinning happily at 7500 rpm for quite some time for a durability test. As for power, we’re guessing close to 600 hp and around 430 lb-ft of torque. Whatever the final numbers, this is one hopped-up Mustang we’re dying to drive.
The 600 HP guess just seems crazy. Since when has anyone made over 100 HP/Liter on a naturally aspirated engine that large without it going in a $200,000 car?
In order to make 600 HP @ 7500 RPM you need to be making 420 lb-ft at that same RPM. The RoadRunner is making what, 444 HP @ 7500 RPM or so? So it's making 310 lb-ft at that RPM. I'm just not seeing how a 4% boost in displacement is going to translate into a 35% increase in HP.
I think even 500 HP is going to be a stretch.
But I hope to be proven wrong in a big way!
-T
Sponsored