More LT5 Rumors
 

http://www.corvetteonline.com/news/t...the-lt5-engine

I expect the next designated ZR-1 to be announce at Road Atlanta, but will not have the rumored LT5. That engine might be destined for the C8 about a year and a half out, as construction to the closed door factory hints at a ramp up for the C8 would be when after the building is complete.

Just rumors...


Sent from my iPhone using ZR-1 Net Registry

Re: More LT5 Rumors
 

This following rumor is the work of Andrew Hitler via GM Authority posting.

The 2018 Corvette ZR1 will have a centrifugal supercharger producing 36.5 PSI of boost inside of the 6.3-liter LT5 V8 engine with an output of 909 horsepower at 8,000 rpm and 600 lb-ft of torque at 7,950 rpm. Front tires are 275/30ZR19 front and this is not a typo 395/35ZR18 rear (first ever) Michelin Pilot Extreme Sport XCR (Cross Country Racing) tires.

Unfortunately, for the stick shifting fans, the 10-speed automatic will be the only transmission available for the new 2018 C7 ZR1.

The Corvette ZR1 actually smacked the quarter-mile down in 8.90 seconds at 157.55 mph on August 20th, 2017 at the Lucas Oil NHRA Nationals dragstrip, making it not only the fastest street-legal production car ever, but also the first street-legal production car to break into the territory of EIGHT seconds through the first 400+ meters.

The ZR1 also pulls 1.70 g on a skidpad with Z07 package, or half a g more than the current Z07-packed Z06. The ZR1 will again be the fastest Corvette with a top speed of 236 miles per hour. With the Z07 package, the top speed will be brought down to 201 mph, and with Z07XX package (probably improving the skidpad to around 2 g’s), the top speed will be 178 mph.

This is the post from Reddit..

As a poster on reddit discovered, tucked away on the fifth page of a recent GM service department document detailing the internal codes the company will use for its 2018 model year vehicles sits a table called “Passenger Car Engines for GMNA,” and at the end of the table lies the description of an utterly alien engine: ENGINE GAS CYL, 6.2L, SIDI, DOHC, VVT, ALUM, GM, It’s listed with the book code “Y,” which in internal GM parlance means it will only be available in the Corvette. And it has its own internal name: LT5.

This is a post from Justin Pritchard.

SIDI is spark-ignited direct injection and VVT is Varible Valve Timing. These two technologies are taking center stage in the battle against high fuel consumption are Direct Injection (DI) and Variable Valve Timing (VVT). ... Simply, DI allows the engine to extract the most possible energy from every molecule of gasoline...

Mike Anderson is the Chief Engineer of Ecotec powerplants at GM. He explains “the 2,200 PSI of pressure that feeds the injectors provides a more atomized and precisely metered fuel spray to each cylinder before every combustion event."

VVT works to control engine breathing requirements in real time for optimized power and efficiency. By taking control of an engine’s all-important breathing characteristics via the manipulation of its valves, Variable Valve Timing systems can seamlessly switch a vehicle’s powerplant from ‘thrifty fuel-miser, to ‘high-performance’ and back on a whim.

By monitoring driver demands and engine operation, as well as dozens of other parameters, the valve timing can be adjusted within the engine in real time to match current conditions and demands.

I will assume that the announcement will be this Fall, so that Pratt & Miller can prepare a racecar version for the 2018 Daytona 24-hour race. BUT THIS IS ALL RUMORS. :cheers:

Re: More LT5 Rumors
 

If true... OMG:jawdrop:

Re: More LT5 Rumors
 

Too any rumors flying around to get too excited about anything. I'll believe it when I see it.

Re: More LT5 Rumors
 

So is or isn't the LT5 a DOHC motor?

Re: More LT5 Rumors
 

Special packaging for the LT5!

GM patents active-aero control package—for a super Corvette?
While Chevrolet is thus far mum on the subject, there’s rampant speculation that a 750-hp (559 kW) Corvette ZR1 will break cover this fall. Beyond the spy photos of camouflaged mules adorned with a towering rear wing, the best evidence of what’s afoot is GM’s U.S. Patent Application 2017/0080770 A1 dated March 23, 2017. The document is titled Vehicle Ride-Height Determination For Control of Vehicle Aerodynamics.

All six of the annotated illustrations in this patent show a current Corvette Stingray adorned with “a plurality of adjustable aerodynamic elements and various sensors mounted to the vehicle body…” Background statements clarify the reasons for this pursuit: “to reduce drag and wind noise…and to prevent undesired lift forces and other causes of aerodynamic instability at high speeds” and “to achieve down force in vehicles in order to improve vehicle traction, high speed stability, and cornering.”

The list of adjustable devices includes a spoiler, an air dam, a shutter with moveable louvers, a specialized wing, an airfoil and a dive plane. The patent description says that these devices may be located at both ends of the vehicle and be adjusted by an electric motor or other types of actuators. In addition to an accelerometer to quantify acceleration and braking dynamics, laser and ultrasonic sensors are noted for ride height determination.

To vary the position of the aero elements relative to the body, electric, mechanical, electro-mechanical, and pneumatic actuators are specified plus “any other type appropriate for the specific packaging, efficiency, and cost constraints…” CPUs responsible for managing ride-height, body pitch angle, and aerodynamic component settings are mentioned.

Now that the Lamborghini and Corvette supercars are about to demonstrate what can be achieved with active aerodynamics, this technology will likely continue trickling down to mainstream models with a performance bent.


http://www.sae.org/dlymagazineimages...5523_26179.jpg

Re: More LT5 Rumors
 

According to the GM description, one of the descriptors is DOHC for the LT5.


Sent from my iPhone using ZR-1 Net Registry

Re: More LT5 Rumors
 

Supercharge this, supercharge that....I know it's the future, but impress me by making it all motor. An art seemed to lost nowdays.

Sent from my XT1585 using ZR-1 Net Registry mobile app

Re: More LT5 Rumors
 

"The 2018 Corvette ZR1 will have a centrifugal supercharger producing 36.5 PSI of boost inside of the 6.3-liter LT5 V8 engine with an output of 909 horsepower at 8,000 rpm and 600 lb-ft of torque at 7,950 rpm."

If those rpm at which both peak power/torque occurs are anywhere close to the production engine, I'd think that they would be a good indicator that the engine is DOHC.


The centrifugal supercharger would be a unique departure from the Positive Displacement superchargers that GM has been using of late on the GEN-IV LSA/LS9 and GEN-V LT4 V8 engines.

Re: More LT5 Rumors
 

According to the book, Heart of the Beast, the LT5 engine was limited to 7000 RPM's, because that was the redline for the installed AC unit....


Sent from my iPhone using ZR-1 Net Registry

Re: More LT5 Rumors
 

I can't get past the name of the author of these "rumors"....Andrew Hitler?


Sent from my iPhone using ZR-1 Net Registry

Re: More LT5 Rumors
 

BTW, doesn't the AC compressor have a clutch on it?


Sent from my iPhone using ZR-1 Net Registry

Re: More LT5 Rumors
 

In which many GM platforms would disengage at WOT.


The waterpump was specifically ratioed for this high rpm usage. Cam chain durability would come into play shortly after redline IIRC.

Re: More LT5 Rumors
 

So, it doesn't have a clutch that releases it at high rpm ?


Sent from my iPhone using ZR-1 Net Registry

Re: More LT5 Rumors
 

Re: More LT5 Rumors
 

Old news from May.

Re: More LT5 Rumors
 

figures

Re: More LT5 Rumors
 

Yes the LT5 has an a/c compressor that engaes and disengages through its normal duty cycle. I am not 100% sure if the LT5s A/C clutch disengages at high TPS(throttle position sensor) angles or not.


I was hoping one of the ECM calibrators would chime in. I don't have a calibration disassembly in front of me.


edit
OK I just checked and ys the 1990 calibration at least has the A/C clutch disengaging at a certain TPS %.
1990
A/C Disable TPS Threshold
A/C Disable Coolant Temp. Threshold
A/C Disable Oil Temp. Threshold
A/C Enable Oil Temp Threshold Hysteresis
A/C Disable Speed Threshold
A/C Disable RPM Threshold


1991
A/C Disable TPS Threshold
A/C Disable Coolant Temp. Threshold
A/C Disable Oil Temp. Threshold
A/C Enable Oil Temp Threshold Hysteresis
A/C Disable Speed Threshold
A/C Disable RPM Threshold






1992
A/C Disable TPS Threshold
A/C Disable Coolant Temp. Threshold
A/C Disable Oil Temp. Threshold
A/C Enable Oil Temp Threshold Hysteresis
A/C Disable Speed Threshold
A/C Disable RPM Threshold


and the 93-95 calibrations
A/C Disable TPS Threshold
A/C Disable Coolant Temp. Threshold
A/C Disable Oil Temp. Threshold
A/C Enable Oil Temp Threshold Hysteresis
A/C Disable Speed Threshold
A/C Disable RPM Threshold




So the a/c is controlled by many constraints, more than just the TPS to which I alluded to earlier. More importantly the actual rpm comes into play, as you could be at WOT while only revving 1500rpm if you wished.

Re: More LT5 Rumors
 

The 2018 ZR1 will not use a "6.3L LT5" engine.

The '18 ZR1 will be the "swan song" for the higher-performance versions of the C7. The engine will be a supercharged, 2-valve, pushrod 6.2L. As for 36.5-psi boost–I won't discount that, becasue it is possible, but if that's the boost number the engine will either have a pretty low static compression ratio or it will have a pretty damn large charge air cooling system.

As for 909-hp at 8000 and 600-lb/ft torque at 7950, if those are really the numbers, they'd tend to confirm that the engine is centrifugally supercharged as engines with hair-blowers typically make max. boost near max engine speed.

I'll guess that the centrifugally supercharged engine in the C7 ZR1 will be a lot easier to drive than the Roots blown LT4 in the C7 Z06. This is because the vast differences in the boost curves of Roots blown vs centrifugally blown engines.

As for the "new" LT5, it will be in the mid-engine car. I'm sticking to my long-time WAG on this. The car will be AWD. The new LT5 will be a DOHC version of the Gen V V8 of 550-600-hp and will drive the rear wheels. The front wheels will be driven by electricity–perhaps wheel motors of maybe 150-200-hp each for a total of 900-1000-hp to the ground.

On SIDI and VVT...both have been on Corvette since 2014.

Re: More LT5 Rumors
 

Not sure that's true because the HVAC compressor on the LT5 likely had a high-rpm cutout.

What I do know is the engine itself had a valve train limiting speed of 8000 rpm with the production cams. Keep in mind that valve train limiting speed might have been 8000 rpm but I suspect that the cam chains would have significantly reduced reliability/durability if run on an engine which was frequently over 7000-rpm.

The engine went to production with a 7072-rpm rev limiter 1) because of concern about accessories, mainly the alternator and power steering pump and 2) because by 7000 rpm was way past peak power.

Re: More LT5 Rumors
 

Here are the AC params for controlling shutoff. These are the stock numbers.

Re: More LT5 Rumors
 

Is there a rev limiter control on all z's in case I miss a power shift? [emoji848]


Sent from my iPhone using ZR-1 Net Registry

Re: More LT5 Rumors
 

There's fuel cutoff and u can limit timing.

Re: More LT5 Rumors
 

But is is not set that way for a stock ZR-1?


Sent from my iPhone using ZR-1 Net Registry

Re: More LT5 Rumors
 

Stock params set on Rev Limiting