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Discussion Starter #1
My 2014 Corvette has 40k miles. I just spent 4k replacing the clutch slave cylinder, jusssst as the warranty was over. I am sure more things are going to happen.

I am considering converting it. The idea would be to sell the motor and transmissions and then connect a motor directly to the rear end, and stuff the front with batteries.

I've swapped LS motors into old muscle cars, and I weld as a hobby, so I have the confidence I can do this (or maybe just more money than brains). I am in Miami, Florida USA.

Ideally the car would be *more* reliable than the corvette with the LT1 ICE. I am sure more things will break over the next 40000 miles if I leave the ICE, and the C7 has a flaw that will require removal of the heads at about 80-100,000 miles because of carbon build up in the cylinders due to the direct injection. I was hoping I could buy some new LiFePo4 batteries, or a lightly used couple of volt packs and run the converted corvette for hundreds of thousands of miles with no major maintenance (at least until the batteries fade). I read about a tesla that had 300,000 miles and didn't require any major service, just fluid changes and tire replacements. Am I dreaming to think such a thing would be possible on a conversion? Or are these conversions unreliable and having things break all the time?

I would like to have about 200 miles of range, and go 0-60 in about 4 seconds or less, with a top speed of like 110 mph. I would also like the stock traction control and magnetic suspension to remain intact. I would also like automatic regen.


So the question is, is this possible?

What motors should I be looking at? What vendors? What controllers?

Thanks for any input.
 

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Discussion Starter #2
Or would it be better to ditch the C7 differential and replace the entire rear end with a tesla motor and gearbox?
 

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You are talking about specs similar to what the tesla model 3 will have, so you should be looking at a battery size and motor/controller KW rating similar to that. As you speculate, your best bet might be to swap the guts from a wrecked model S into your corvette. The challenge will be fitting the battery, since the corvette chassis wasn't built with the "skateboard" design tesla uses. You could use leaf cells, but without adding 2 leaf packs at best your range would be about half your stated goal. LiFePO4 won't give you the power density you need to reliably give 4s 0-60. You could get the range but you'd probably need 1000-1200lbs of battery in that format.

Good news is the cost of all these parts are coming down, but the challenge these days is in integrating OEM components. There are several parties that have had some success in doing this, but I don't know how much of it has been made available for purchase or shameless copy.

Regen is automatic in any AC system, how it is controlled varies. traction control and suspension will depend on how hard it is to yank the engine from your corvette without affecting the function of other systems. However given the fact that corvettes have a lot of aftermarket options I would hope that their electronics and other systems are more modularized in anticipation of stuff being swapped out. Corvette forums are the best place to get that info.

Good luck.
 

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Discussion Starter #4
I am pretty sure the stock suspension/rear end traction stuff can be separated from the motor.

Assume I don't want to use a model S motor, as it is transverse and requires the elimination of the rear diff (as it has its own diff, what AC motors/controllers would you recommend - with a rear output shaft - that would give me 0-60 sub 4? I am assuming the car will weigh something like 34-3500 lbs with the batteries.

Thanks.
 

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Let me give you guys an example.

http://www.evwest.com/catalog/product_info.php?cPath=8&products_id=300

This motor says it can do
Rated Torque: 560 Lb Ft Peak (w/150kW controller)
Rated Power: 420 HP Peak (w/150kW controller)

It also mentions it can spin to 10,000 rpm.

It also says that it is 180lbs, 10.5" in diameter, and 18.5 inches end to end.

The TR6070 for the corvette is 21" end to end, and at least 10.5" in diameter. It weights 153 lbs dry.

So why not just fab up a mount for the above electric motor where the tranny sits, and fab up some sort of custom drive shaft/coupler to hook it up to the rear end?

Are there batteries I could stuff into the engine compartment/forward of the transmission in the tunnel?

Why do I need the transmission?
 

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The idea would be to sell the motor and transmissions and then connect a motor directly to the rear end...
The C7 - like the C6 and C5 - does not have a separate transmission and "rear end" (final drive with differential) - it has a transaxle. You might be able to split the case and leave only the final drive portion in the car, but it might need an additional shaft bearing, it would probably need a custom housing to close it off, and it would certainly need some sort of front mount.



I might be more practical to replaced the entire transaxle with a final drive unit (diff) from another vehicle with IRS (one that uses a separate transmission, such as the Camaro), and connect the motor to that.

Whether using the Corvette final drive or an alternative, tt would be slick to mount the motor directly to the final drive portion - making an electric drive unit - for the builder with the skills and tools to do it. Unfortunately, this would leave only the ring and pinion for reduction gearing, so the motor would be running slowly and so would be heavy and bulky. The 2014 Corvette final drive ratios is 3.42:1 with the manual (and as low as are 2.56:1 with the automatic transmission depending on performance package), which is half to a quarter of the gear reduction used by production EVs (other than the oddball Chevrolet Spark EV).
 

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Let me give you guys an example.

http://www.evwest.com/catalog/product_info.php?cPath=8&products_id=300

This motor says it can do
Rated Torque: 560 Lb Ft Peak (w/150kW controller)
Rated Power: 420 HP Peak (w/150kW controller)

It also mentions it can spin to 10,000 rpm.
...
So why not just fab up a mount for the above electric motor where the tranny sits, and fab up some sort of custom drive shaft/coupler to hook it up to the rear end?
Because that 10,000 rpm motor would only be turning a couple thousand RPM at highway speed, with just the final drive reduction. It needs another stage of reduction gearing... although an extreme final drive ratio would help and might be enough.

As far as performance is concerned, it would be like driving with the engine and with the transmission in 5th gear all of the time.
 

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Discussion Starter #8
The idea would be to sell the motor and transmissions and then connect a motor directly to the rear end...
The C7 - like the C6 and C5 - does not have a separate transmission and "rear end" (final drive with differential) - it has a transaxle. You might be able to split the case and leave only the final drive portion in the car, but it might need an additional shaft bearing, it would probably need a custom housing to close it off, and it would certainly need some sort of front mount.



I might be more practical to replaced the entire transaxle with a final drive unit (diff) from another vehicle with IRS (one that uses a separate transmission, such as the Camaro), and connect the motor to that.

Whether using the Corvette final drive or an alternative, tt would be slick to mount the motor directly to the final drive portion - making an electric drive unit - for the builder with the skills and tools to do it. Unfortunately, this would leave only the ring and pinion for reduction gearing, so the motor would be running slowly and so would be heavy and bulky. The 2014 Corvette final drive ratios is 3.42:1 with the manual (and as low as are 2.56:1 with the automatic transmission depending on performance package), which is half to a quarter of the gear reduction used by production EVs (other than the oddball Chevrolet Spark EV).
I see.
It would be sweet to somehow take advantage of the world class c7 traction control with the z51 option. But seems like a lot of enginerting/fabrication. If I can somehow fit a complete tesla motor where the transaxle goes, can I get the traction control to work? I take it that outside of solving the mounting problems, the only issue would be making the correct axle shafts?
 

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It would be sweet to somehow take advantage of the world class c7 traction control with the z51 option. But seems like a lot of enginerting/fabrication.
The Corvette uses a simple electronically-controlled differential, so in addition to accelerator override and applying the diff clutch, it would need to use application of individual brakes. It would be difficult to integrate GM's systems with the electric motor controller, but if you can get the GM stuff to ignore that the engine is missing :eek: then at least the brakes (and all of the sensors for wheel speeds and acceleration) would be unaffected and the diff clutch might still work.
 

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If I can somehow fit a complete tesla motor where the transaxle goes, can I get the traction control to work? I take it that outside of solving the mounting problems, the only issue would be making the correct axle shafts?
A Tesla drive unit (preferable the "large" higher-powered one) would be nice, but the mounting might be a challenge. Check the width of the drive unit (such as from Tesla Large Drive Unit Dimensions) and compare the width of the unit to the space between the frame rails just behind the C7's rear axle. Then there's the matter of checking for interference between the drive unit and the C7 suspension; I think it can be assumed that the C7 rear subframe would need to be replaced or modified.

Keep in mind that a Tesla drive unit is behind the axle line, other than the rear of the differential case portion (which is long because it contains an additional pinion shaft bearing); in contrast, the C7's transaxle is ahead of the axle line, other than the rear of the differential case portion. They really don't sit in the same place in the car. The Tesla motor and inverter would end up in the forward portion of the space occupied by the stock Corvette's mufflers.

I don't see how it matters what the motor is - it's not managed by a GM computer so it won't work with GM's traction control, and the rest of the car won't work with Tesla's systems for traction control with any reasonable amount of work.

Yes, there's also the fun of finding or building the parts to make a Tesla drive unit work with Corvette hubs. This sort of thing is frequently done, so it should be possible. For an example, there's the current project building a Tesla Powered BMW E31 8 Series, which is using custom-built shafts incorporating BMW and Tesla parts.

Any significant change in the rear axle area will be complicated by the rear spring, which is a composite leaf which runs across the car, under the back of the transaxle (yellow arrow in the first photo):
Left side of rear suspension, from below:


Rear of car, from below, top of photo is forward:

(photos from Edmunds: 2014 Chevrolet Corvette Stingray Z51 Suspension Walkaround)
 

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Discussion Starter #11
If I can somehow fit a complete tesla motor where the transaxle goes, can I get the traction control to work? I take it that outside of solving the mounting problems, the only issue would be making the correct axle shafts?
A Tesla drive unit (preferable the "large" higher-powered one) would be nice, but the mounting might be a challenge. Check the width of the drive unit (such as from Tesla Large Drive Unit Dimensions) and compare the width of the unit to the space between the frame rails just behind the C7's rear axle. Then there's the matter of checking for interference between the drive unit and the C7 suspension; I think it can be assumed that the C7 rear subframe would need to be replaced or modified.

Keep in mind that a Tesla drive unit is behind the axle line, other than the rear of the differential case portion (which is long because it contains an additional pinion shaft bearing); in contrast, the C7's transaxle is ahead of the axle line, other than the rear of the differential case portion. They really don't sit in the same place in the car. The Tesla motor and inverter would end up in the forward portion of the space occupied by the stock Corvette's mufflers.

I don't see how it matters what the motor is - it's not managed by a GM computer so it won't work with GM's traction control, and the rest of the car won't work with Tesla's systems for traction control with any reasonable amount of work.

Yes, there's also the fun of finding or building the parts to make a Tesla drive unit work with Corvette hubs. This sort of thing is frequently done, so it should be possible. For an example, there's the current project building a Tesla Powered BMW E31 8 Series, which is using custom-built shafts incorporating BMW and Tesla parts.

Any significant change in the rear axle area will be complicated by the rear spring, which is a composite leaf which runs across the car, under the back of the transaxle (yellow arrow in the first photo):
Left side of rear suspension, from below:


Rear of car, from below, top of photo is forward:

(photos from Edmunds: 2014 Chevrolet Corvette Stingray Z51 Suspension Walkaround)
This is from a c7 forum:
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The eLSD (Chevy's official name for it) works through a hydraulic reservoir with fluid separate from the diff fluid. The differential and eLSD system interact via a clutch package that minutely adjusts the power differential to the two rear half shafts, and miraculously doing it 83 times per second. The eLSD has its own computer module, which communicates with, at least: the ECU, the ABS sensors, the traction control system, the steering wheel position sensor, a transmission gear selection sensor, throttle position sensor and more. When Jim Mero, Mike Bailey and their Corvette development team colleagues were fine tuning the computer controls for eLSD, they were able, with a single computer "bit" or "byte," to fine tune the operation of the system to within 0.1% inputs, changing the car from over steering to under steering (at a given speed and inputs) then back to under steering again. That is how finely tuned the system is.

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It does seem like a lot of work. It would be so awesome to custom fabricate a bellhousing of sorts and a coupler that would mate the output shaft of the motor to the input shaft of the differential portion of the transaxle. I know they sell 4.10 gears for the c7 but I guess I would need an 9:1 ratio ring and pinion.
Then if I could tune the lookup tables of the z51 ediff cpu unit, I might have something there (tuning the engine gpu is easy, people do it all the time). You could replace the engine and front cooling system with batteries and have something that resembled the c7 very well, but without the less reliable parts of the ICE power train.

Too bad someone doesn't make a kit.
 

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The description from the C7 forum looks technically accurate, although written more like an advertisement than an objective technical assessment. I'm sure the eLSD works well, but it's just a computer-controlled LSD. All it can do it adjust the clutch - it can't make the faster-turning axle get more torque than the slower-turning one, so it doesn't have the capability of a "torque-vectoring" system such as those in the
  • Lexus RC F,
  • Mitsubishi vehicles with Active Yaw Control,
  • Acura vehicles with SH-AWD,
  • Audi vehicles with the Sport Differential (from Magna or ZF), or
  • BMW vehicles with Dynamic Performance Control (ZF's Vector Drive).
It would not likely be practical to adapt one of the more advanced differentials to the Corvette, so at least retaining the stock eLSD would be desirable.

Advanced designs are more important to handling (stability control and enhanced dynamics) than to traction for straight-line acceleration.
 

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Lingenfelter used to offer a coil spring conversion kit that eliminated the transverse fiberglass spring - the single spring reduces the independence of the rear suspension.
 

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Lingenfelter used to offer a coil spring conversion kit that eliminated the transverse fiberglass spring - the single spring reduces the independence of the rear suspension.
The springs don't change the geometry; this suspension is fully independent regardless of the springs.

The leaf spring does resist both individual wheel travel and roll travel; that's the same as having both coil springs on each side plus a stabilizer (anti-sway) bar. Chevrolet takes advantage of this: the base Corvette does not have a separate stabilizer bar, but still has suitable roll stiffness.

The reason for the coil spring conversion is that it allows the builder to separately adjust the spring rate and roll rate; doing this with just a leaf would require custom-fabricating a leaf for each combination (and/or moving the leaf mounting points), or using a stabilizer bar as well as the leaf (as Chevrolet does at the front of all C7's and at the rear in the Z51 and Z06 packages). If a leaf of the right spring rate for each wheel provides too much roll stiffness, there's no way to fix that, and racers often want very high wheel spring rates.

The net effect is that you can replace the stock dampers (shock absorbers) and composite leaf with coil-over shocks, coils, and a stabilizer bar. It will be heavier and it will cost US$2K-$4K (depending on brand and passive versus magnetic ride control shocks) plus the stabilizer bars, but it would be easier to tune and maybe out of the way... or maybe worse, because the stabilizer bar needs to run somewhere. At least you have the option of building a custom stabilizer bar installation, placing the bar where you need to in order to avoid drive components - the stock rear bar location is not compatible with a Tesla rear drive unit, for instance.
 

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To the OP
Sounds like you have to desire to find a solution, and it's an admirable desire in my eyes.
I deleted you have a huge opportunity thanks to the transaxle setup in the c7. I would agree with the plan to separate the transmission from the rear differential housing. I would then look to a specialist transmission/gear shop to find you a ring gear and pinion that you can run to take the motor output through 90deg in combination with an alternative helical ring gear on the diff that is driven by a reduction gear mated to the first ring gear in a reduction stage. Hope that makes sense, bit difficult to explain. Basically add a large and small gear between the motor and diff to add a reduction stage, and have an additional housing manufactured that holds this reduction assembly and to which the motor mounts to. You have the length in your tunnel for it and you'd have a killer solution plus potential marketable product for other builders/racers.
And you can fill the engine bay with Volt or leaf cells. If you don't want crazy acceleration as you stated I believe the leaf cells might cope if you have a large enough pack and aren't doing track work with persistent Accel decel. One caution though would be the ambient weather temperatures depending where you are based. A liquid cooled battery may therefore be better.
And no reason you couldn't mate a high power Tesla motor to your diff and mount the inverter remotely above it and keep the lovely Tesla power...
Sounds like a potentially amazing project, I will follow with bated breath.
 

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... you have a huge opportunity thanks to the transaxle setup in the c7. I would agree with the plan to separate the transmission from the rear differential housing. I would then look to a specialist transmission/gear shop to find you a ring gear and pinion that you can run to take the motor output through 90deg in combination with an alternative helical ring gear on the diff that is driven by a reduction gear mated to the first ring gear in a reduction stage. Hope that makes sense, bit difficult to explain. Basically add a large and small gear between the motor and diff to add a reduction stage, and have an additional housing manufactured that holds this reduction assembly and to which the motor mounts to.
Aside from not needing a new ring and pinion (use the ones that are already in that final drive portion), this makes sense to me. I just don't think many people - even dedicated enthusiasts - are up to either building this themselves, or paying someone else to do it.

One challenge is that in both manual (Tremec TR6070) and automatic (6L80 or 8L90) Corvette C7 transaxles, the transmission output shaft is on the car's centreline. An additional pair of reduction gears ahead of that would shift the motor shaft off centre or up or down. Ground clearance would likely be an issue if shifted down, space would likely be an issue if shifted up or to either side. If gears from the manual transmission were used, the spacing between shaft centrelines would be 85 mm. One way to avoid this is to take power to a layshaft and back (the stock design but with only one gear, and the same as production EVs); however, that would be two stages of gearing in addition to the final drive (in a production EV such as the Tesla, Leaf, etc. the second stage is the final drive to the ring gear around the differential), taking more length and adding more gear loss.

A planetary gearset could be used for reduction, and an obvious candidate would be the final (4th) planetary set of the automatic transmission. It might be possible to sell the manual transaxle, buy a used automatic, salvage both the final drive and the final planetary set of the automatic, and make a housing to support the ring gear (non-rotating) and the sun gear on a new input shaft coupled to the electric motor. That would duplicate the gearing of the transmission in first gear, which for a 8L90 (used starting in 2015) means 4.56:1 first reduction stage multiplied by a 2:41:1 (or 2.73:1 for Z51) final drive ratio. A similar arrangement is probably similarly workable with the earlier 6L80 6-speed automatic transmission (used for the C6 and the 2014); it would have 4.027:1 multiplied by 2.56:1 (or 2.73 w/ Z51) ratios.
Reference:
Saturation Dive: The GM 8L90 transmission
2014 Chevrolet Corvette Stingray Preliminary Specifications
2015 Chevrolet Corvette Stingray Specifications
 

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A Tesla drive unit (preferable the "large" higher-powered one) would be nice, but the mounting might be a challenge. Check the width of the drive unit (such as from Tesla Large Drive Unit Dimensions) and compare the width of the unit to the space between the frame rails just behind the C7's rear axle. Then there's the matter of checking for interference between the drive unit and the C7 suspension; I think it can be assumed that the C7 rear subframe would need to be replaced or modified.

Keep in mind that a Tesla drive unit is behind the axle line, other than the rear of the differential case portion (which is long because it contains an additional pinion shaft bearing); in contrast, the C7's transaxle is ahead of the axle line, other than the rear of the differential case portion. They really don't sit in the same place in the car. The Tesla motor and inverter would end up in the forward portion of the space occupied by the stock Corvette's mufflers.

I don't see how it matters what the motor is - it's not managed by a GM computer so it won't work with GM's traction control, and the rest of the car won't work with Tesla's systems for traction control with any reasonable amount of work.

Yes, there's also the fun of finding or building the parts to make a Tesla drive unit work with Corvette hubs. This sort of thing is frequently done, so it should be possible. For an example, there's the current project building a Tesla Powered BMW E31 8 Series, which is using custom-built shafts incorporating BMW and Tesla parts.

Any significant change in the rear axle area will be complicated by the rear spring, which is a composite leaf which runs across the car, under the back of the transaxle (yellow arrow in the first photo):
Left side of rear suspension, from below:


Rear of car, from below, top of photo is forward:

(photos from Edmunds: 2014 Chevrolet Corvette Stingray Z51 Suspension Walkaround)
Dont use salvaged parts on this nice car.
 

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nop.Highest performance salvaged drive train you can find is tela rear traction motor when you have better options new.like AC50 or HyPer9


You’re joking right? The Tesla large drive unit blows both of those out of the water. Neither of those are made to the quality level that an automotive OEM builds to. Good quality, but not high quality


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