Shno's House of Z

[DGthe3]

Originally Posted by Bhobbs

Seeing how the LT1 runs out of steam around 4800 rpm, I wonder what the LTx would be capable of with some CNC heads and enough cam. Spin it past 7000 rpm, like the LS7. It may not beat the Voodoo, but with the money saved, they can put that back in the Z/28 in light weighting and that kind of stuff.

Huh?

LT4 hits peak power at 6400 rpm:





*edit*

derp ... I saw 'LT1' as 'LT4'. Whoopsie.

Here is the 'official' LT1 dynochart:

Its still building power at 4800 rpm, and keeps doing so all the way out to 6 grand

[1leNPP]

Some my not like what I going to say but when you look at the chart and the power ban of the motor why in the hell would you put a 10 speed trans behind a high tork low rpm (you buss up to 9k that fast 6.5 is not ) motor . The gear spacing is going to be to close together to use the motor . I just do not see it . I think that what wrong with the M4 and the 7 speed DCT trans in that car . The gears are to close together an the M4 can not put power down . That motor need a 2 speed powerglide trans in it .

[Mr. Wyndham]

Originally Posted by 1leNPP

Some my not like what I going to say but when you look at the chart and the power ban of the motor why in the hell would you put a 10 speed trans behind a high tork low rpm (you buss up to 9k that fast 6.5 is not ) motor . The gear spacing to going to be to close together to use the motor . I just do not see it . I think that what wrong with the M4 and the 7 speed DCT trans in that car . The gears are to close together an the M4 can not put power down . That motor need a 2 speed powerglide trans in it .

For fastest acceleration, ideally the engine should be operating at it's peak hp/tq level from 0mph up to the vehicle's top speed. It doesn't matter where in the rpm range that is. A CVT can do this in concept...but it fails miserably in real life because the design cannot handle high power levels. So...more gears/speeds mean more time at that sweet spot.

High RPM engines are designed to spin so quickly because they don't produce enough torque to serve their purpose at lower rpms. The LT4, by contrast, produces insane levels of torque at lower rpms, so it doesn't *need* to spin very fast to perform well.

Two different methods...but there is the same result: Speed.

I assure you, the A10 successfully used the engine's power output on our hot laps.

[DGthe3]

Originally Posted by 1leNPP

Some my not like what I going to say but when you look at the chart and the power ban of the motor why in the hell would you put a 10 speed trans behind a high tork low rpm (you buss up to 9k that fast 6.5 is not ) motor . The gear spacing is going to be to close together to use the motor . I just do not see it . I think that what wrong with the M4 and the 7 speed DCT trans in that car . The gears are to close together an the M4 can not put power down . That motor need a 2 speed powerglide trans in it .

Huh?
They did it so that there is both a wide overall spread from 1st to last and close ratios between each gear along the way.

And what are you talking about with the M4 having gears 'too close together to put the power down'? That is precisely why you go with closely spaced gears in the first place: to keep the engine in the powerband between shifts.

[1leNPP]

Ok and that why M4 with the DCT tran is a sec slower at the street of willow than with the manual trans with just 6 gears in it that are space wider apart than the 7 speed DCT . That DCT trans keeping that motor in it power ban so it could blow the tires off the car work really good for its laps times .

Tork suck if you can not hook it up . That is why the z/28 lost to the gt350 they could not put power down coming out of the corners as soon as the gt350 . Now you got 650ft. of tork through the full power ban and 10 gears use so what going to happen is the car going to pull power in every gear trying to get this thing to hook up. Just do not see the point in it .

[Number 3]

Think of it this way.

Have you ever driven a Camaro or Corvette with CAGS? What happens when you try to accelerate after getting forced to shift into a gear that is too high? It takes a much longer time to get back up the power band to have good acceleration.

More gears means more flexibility and the ability to optimize the right gear for the right situation. This helps for both FE and performance.

Now that being said, it needs to shift lightning fast. This is one reason why gearing is critical in a 0 - 60 or 1/4 mile run. If you are shifting, you aren't accelerating anymore.

Now my hope is GM doesn't screw up the powertrain calibrations. The last transmission JV was the 6 speed FWD that went into the Traverse, Outlook, Acadia and Enclave. GM had multiple recalls to recalibrate. Ford's version that I'm aware of had no issues.

This is a critical point for everyone to pay attention to. It's not simply the hardware, it's the ability to calibrate/integrate into the vehicle. The best calibrator/integrator WINS!

[Bhobbs]

Originally Posted by DGthe3

Huh?

LT4 hits peak power at 6400 rpm:





*edit*

derp ... I saw 'LT1' as 'LT4'. Whoopsie.

Here is the 'official' LT1 dynochart:

Its still building power at 4800 rpm, and keeps doing so all the way out to 6 grand

Ok, maybe running out of steam was a poor choice of words, but there is a serious drop in torque production after 4800 rpm. If you look at the torque curve vs the LS3, the LT1 has a good advantage up to 4800 rpm where it starts to drop. The LS3 carries its torque much better. By redline, the LT1 drops almost to LS3 torque levels.

[JusticePete]

How power is available is as important as how quickly the power spools up, the engine spins up. If two vehicles have the same exact power, same HP and TQ curves, the engine that spins up to power faster under load will be faster.

I have no time in the seat of a new ZL1 so it is impossible for me to venture an opinion. For guys like Joe Scoop, it is just as hard to compare because the new ZL1 is so mcuh lighter. So with this in mind, Joe do you think the power in the new engine comes on more quickly, slower or similar to the old engine?

[Mr. Wyndham]

Originally Posted by JusticePete

How power is available is as important as how quickly the power spools up, the engine spins up. If two vehicles have the same exact power, same HP and TQ curves, the engine that spins up to power faster under load will be faster.

I have no time in the seat of a new ZL1 so it is impossible for me to venture an opinion. For guys like Joe Scoop, it is just as hard to compare because the new ZL1 is so mcuh lighter. So with this in mind, Joe do you think the power in the new engine comes on more quickly, slower or similar to the old engine?

Joe Scoop.

Theoretically, only vehicle weight and gearing will alter the speed at which both identical engines speed up.

The engine incorporates many more lightweight features than the LSA did. A smaller supercharger, aluminum balancer/damper, forged pistons/rods/crank, titanium valves. All of these things add up to decrease reciprocating mass, and increases how quickly the engine spins up. Many of you already know this.

That all said, I thought the LT4 spun up pretty damn quick. I was in the manual transmission car. If you watch videos of the automatic, the engine spins up and responds instantly to the different gear changes with little to no jolting of the passengers.

[DGthe3]

Originally Posted by 1leNPP

Ok and that why M4 with the DCT tran is a sec slower at the street of willow than with the manual trans with just 6 gears in it that are space wider apart than the 7 speed DCT . That DCT trans keeping that motor in it power ban so it could blow the tires off the car work really good for its laps times .

Tork suck if you can not hook it up . That is why the z/28 lost to the gt350 they could not put power down coming out of the corners as soon as the gt350 . Now you got 650ft. of tork through the full power ban and 10 gears use so what going to happen is the car going to pull power in every gear trying to get this thing to hook up. Just do not see the point in it .

I have no idea what you're talking about with the M4 being unable to put the power down due to closely spaced gearing with the DCT. Was there some sort of comparison test between the DCT & manual, or are you comparing two different drivers on two different days?


And Z/28 vs GT350R ... that's probably a bad example for you to use as it goes contrary to the point you're trying to make. The GT350 has a slightly closer ratio transmission than the Z/28 has (1st to 6th spread of 5.172:1 vs 5.32:1) as well as roughly 20% more torque multiplication in every gear. Thats in addition being more powerful, lighter, having wider rear tires, and lighter wheels (all of which would contribute to it accelerating out of the corners better than the Z/28).

[Jackass]

Originally Posted by Mr. Wyndham

Joe Scoop.

Theoretically, only vehicle weight and gearing will alter the speed at which both identical engines speed up.

The engine incorporates many more lightweight features than the LSA did. A smaller supercharger, aluminum balancer/damper, forged pistons/rods/crank, titanium valves. All of these things add up to decrease reciprocating mass, and increases how quickly the engine spins up. Many of you already know this.

That all said, I thought the LT4 spun up pretty damn quick. I was in the manual transmission car. If you watch videos of the automatic, the engine spins up and responds instantly to the different gear changes with little to no jolting of the passengers.

Not really , at some point the airdinamic design will be more so than the weight and gearing

[Number 3]

Originally Posted by Jackass

Not really , at some point the airdinamic design will be more so than the weight and gearing

You are correct, aerodynamics do matter quite a bit. Once you clear 55 to 60 mph it becomes a bigger deal.

At highway cruising speed 3 things matter moving a vehicle down the road.

Powertrain (engine and drivetrain)

Rolling resistance (weigh of the vehicle pressing the tires on the road)

Aerodynamics (air flow over and around the vehicle)

At cruising speed, aero is 50% of the equation, as much as the other two.

And aero consists of two elements, Coefficient of Drag, Cd and Cross Sectional Area, A. That is CdA. So being slippery and small matter.

Now to take that a step further and look at a car designed to rule on the road course, you actually want to increase the effective rolling resistance to create "down force". This is done using aerodynamics as well. So the Z/28 and the Z07 package on the Corvette are intended to this. So to be great on the track you are doing things counter to what you want for a car to move easily down the road by making aero worse in order to selectively make rolling resistance worse.

And the HP required to overcome aerodynamics/down force goes up exponentially with speed.

[1leNPP]

http://fastestlaps.com/tracks/willow...eets-of-willow Number 16 on the list and number 12 on the list two Heads to Heads that motor trends did and Randy Pobst drove the BMW M4 on each test . The manual was faster than DCT trans because the manual trans car did a better job at putting down power. I like to think its the gear spacing being wider on the manual trans working better with the Turbo motor power band .

The 10 peed trans can be a great thing for the right engine like a E92 s65 motor that only make 300 FT. torque and max power at 8,000 RPM. The LT4 is making 400ft. of torque at a 1,000 rpm its making 500ft. torque of at 2,000 up to it max 600+ ft. torque that engine is never out of its power band . For the car to be able to use that I think the car is going to need wider gearing spacing to be able to use the torque the motor has to make the car go faster with out blowing the tire off the car or the car just going to pull power to hook the car up . If the car is pulling power to hook the car up than what the point. The only time you really be able to use it is at speed over 150 MPH. So how many road course that you can really run a 150 MPH+ on.

Let me make this clear I am not nocking the 10 speed trans, I just think the LT4 engine is not a good match for that trans.

Hole point of the Z/28 part is that you have to be able to put power down on corner exit to run fast lap times . That is why the new 2017 GS corvette with only 450 HP & 450 ft. torque ran only .6 off the ZR1 lap time ( so say GM) . That tells me the C7 corvette chassis can really can only handle the LT1 motor and that car is running a P325 cup2 tire on the back of it. The new ZL1 is only going to have a P305 on the back and a motor with 640 HP & 600ft + torque and you are pack 10 gears in the trans together with it . Now its just me thinking here I don't see how the car not pulling power every time you go WOT under 100 MPH.

[Scarrzz]

Originally Posted by Number 3

You are correct, aerodynamics do matter quite a bit. Once you clear 55 to 60 mph it becomes a bigger deal.

At highway cruising speed 3 things matter moving a vehicle down the road.

Powertrain (engine and drivetrain)

Rolling resistance (weigh of the vehicle pressing the tires on the road)

Aerodynamics (air flow over and around the vehicle)

At cruising speed, aero is 50% of the equation, as much as the other two.

And aero consists of two elements, Coefficient of Drag, Cd and Cross Sectional Area, A. That is CdA. So being slippery and small matter.

Now to take that a step further and look at a car designed to rule on the road course, you actually want to increase the effective rolling resistance to create "down force". This is done using aerodynamics as well. So the Z/28 and the Z07 package on the Corvette are intended to this. So to be great on the track you are doing things counter to what you want for a car to move easily down the road by making aero worse in order to selectively make rolling resistance worse.

And the HP required to overcome aerodynamics/down force goes up exponentially with speed.

Aerodynamics was my second favorite course back in college, right behind Babeology.