More LT5 Rumors

[Bob Eyres]

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


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[Bob Eyres]

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


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[Hog]

Originally Posted by Bob Eyres

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


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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.

[Bob Eyres]

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


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[-=Jeff=-]

http://www.gminsidenews.com/articles...-corvette-zr1/

[XfireZ51]

Originally Posted by -=Jeff=-

http://www.gminsidenews.com/articles...-corvette-zr1/

Old news from May.

[-=Jeff=-]

figures

[Hog]

Originally Posted by Bob Eyres

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


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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.

[Hib Halverson]

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.

[Hib Halverson]

Originally Posted by lfalzarano

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....

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.