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I've been reading the posts by the folks getting their superchargers installed over on scionlife. It seems they are putting out much better numbers than originally stated. 197 whp sounds like a lot more than 203 at the crank. I've never heard of driveline loss less than 3% before, so TRD is lowballing (as usual for Toyco).
Another interesting thing is also popping up. Scionspeed broke their driveshafts on their stage three turbo (according to their own website), and now Dezod has also broken driveshafts on their turbo prototype. Why is this important? Glad you asked!
TRD intentionally limited maximum torque increase to a claimed 13 ftlbs, and looking at the dyno charts they provided, it appears they basically took a small torque increase and instead of having torque drop like a rock after 4500 rpm, they hold it almost all the way to redline. So we get a great horsepower increase without a large torque increase. OK, so it sounds like a lot of Internet mumbo-jumbo at this point. Let's look at it a little closer.
The OEM clutch and gearbox are rated for a certain amount of torque. They don't care about hp, only torque because torque is what breaks gearboxes and makes clutches slip. Toyota is NOT known for building bulletproof gearboxes, and in fact, many of the issues I have heard about in Toyota's past have centered around gearbox problems. No, the MkIV TT Supra isn't included in this, but everyone with an NA-T Supra knows the W58 5 speed gearbox is THE weak link in the NA Supra driveline. So let's get back to the tC.
If the tC's drivetrain is a known quantity for TRD, and it is, and TRD knows they will be providing a complete powertrain warranty just as if the supercharger came from Japan, then they know they need to be intelligent about how they make power so the modded cars don't break driveline parts.
Let's look specifically at the E350 transmission in the tC. It has an extremely low final drive ratio (hence the "requests" for a sixth gear), and the first two gears are so low that they are only good for launching, all the real driving happens in third through fifth. For you mathematics guys, crankshaft torque is multiplied by these factors:
1st - 14.983
2nd - 8.661
3rd - 5.645
4th - 4.116
5th - 3.282
So, at peak torque with the supercharger, 173 ftlbs, here are the numbers at the wheel (at zero loss, delivered the axles!)
1st - 2592 ftlbs = 2527 lbs force at contact patch
2nd - 1498 ftlbs= 1461 lbs force at contact patch
3rd - 977 ftlbs = 952 lbs force at contact patch
4th - 712 ftlbs = 694 lbs force at contact patch
5th - 568 ftlbs = 554 lbs force at contact patch
Lets compare this to the auto:
1st - 10.804
2nd - 6.020
3rd - 3.872
4th - 2.795
1st - 1869 ftlbs = 1822 lbs force at contact patch
2nd - 1041 ftlbs= 1015 lbs force at contact patch
3rd - 670 ftlbs = 653 lbs force at contact patch
4th - 484 ftlbs = 471 lbs force at contact patch
All the numbers are calculated at zero loss, but we know we're losing 15% to 18% through the bearings and gears. Still, I don't know about you, but I'd bet the likelihood of killing the axles in a manual transmission is a LOT greater.
So TRD, in their engineering wisdom decided a less than 10% increase in peak torque would preserve the drivetrain better than just pushing the hp up on the stock curve by making 20% or 25% more torque at the same peak and stressing the whole drivetrain, adding to torque steer, and having more warranty issues than an 80's Hyundai. Pretty damn clever if you ask me.
I expect we will see growing drivetrain issues with turbocharged tCs because they make a LOT more torque and a lot sooner. Sure it feels good today, but I can tell you from personal experience, driving a car with a bad gearbox sucks every single day. AMHIK. Breaking driveshafts/axles/final drive gears/etc. is just that much worse.
If there's interest, I can also post similar numbers for the MkIV Supra and Mitsubishi EVO VIII. It's enlightening.
EDIT - fixed my arithmetic..
Another interesting thing is also popping up. Scionspeed broke their driveshafts on their stage three turbo (according to their own website), and now Dezod has also broken driveshafts on their turbo prototype. Why is this important? Glad you asked!
TRD intentionally limited maximum torque increase to a claimed 13 ftlbs, and looking at the dyno charts they provided, it appears they basically took a small torque increase and instead of having torque drop like a rock after 4500 rpm, they hold it almost all the way to redline. So we get a great horsepower increase without a large torque increase. OK, so it sounds like a lot of Internet mumbo-jumbo at this point. Let's look at it a little closer.
The OEM clutch and gearbox are rated for a certain amount of torque. They don't care about hp, only torque because torque is what breaks gearboxes and makes clutches slip. Toyota is NOT known for building bulletproof gearboxes, and in fact, many of the issues I have heard about in Toyota's past have centered around gearbox problems. No, the MkIV TT Supra isn't included in this, but everyone with an NA-T Supra knows the W58 5 speed gearbox is THE weak link in the NA Supra driveline. So let's get back to the tC.
If the tC's drivetrain is a known quantity for TRD, and it is, and TRD knows they will be providing a complete powertrain warranty just as if the supercharger came from Japan, then they know they need to be intelligent about how they make power so the modded cars don't break driveline parts.
Let's look specifically at the E350 transmission in the tC. It has an extremely low final drive ratio (hence the "requests" for a sixth gear), and the first two gears are so low that they are only good for launching, all the real driving happens in third through fifth. For you mathematics guys, crankshaft torque is multiplied by these factors:
1st - 14.983
2nd - 8.661
3rd - 5.645
4th - 4.116
5th - 3.282
So, at peak torque with the supercharger, 173 ftlbs, here are the numbers at the wheel (at zero loss, delivered the axles!)
1st - 2592 ftlbs = 2527 lbs force at contact patch
2nd - 1498 ftlbs= 1461 lbs force at contact patch
3rd - 977 ftlbs = 952 lbs force at contact patch
4th - 712 ftlbs = 694 lbs force at contact patch
5th - 568 ftlbs = 554 lbs force at contact patch
Lets compare this to the auto:
1st - 10.804
2nd - 6.020
3rd - 3.872
4th - 2.795
1st - 1869 ftlbs = 1822 lbs force at contact patch
2nd - 1041 ftlbs= 1015 lbs force at contact patch
3rd - 670 ftlbs = 653 lbs force at contact patch
4th - 484 ftlbs = 471 lbs force at contact patch
All the numbers are calculated at zero loss, but we know we're losing 15% to 18% through the bearings and gears. Still, I don't know about you, but I'd bet the likelihood of killing the axles in a manual transmission is a LOT greater.
So TRD, in their engineering wisdom decided a less than 10% increase in peak torque would preserve the drivetrain better than just pushing the hp up on the stock curve by making 20% or 25% more torque at the same peak and stressing the whole drivetrain, adding to torque steer, and having more warranty issues than an 80's Hyundai. Pretty damn clever if you ask me.
I expect we will see growing drivetrain issues with turbocharged tCs because they make a LOT more torque and a lot sooner. Sure it feels good today, but I can tell you from personal experience, driving a car with a bad gearbox sucks every single day. AMHIK. Breaking driveshafts/axles/final drive gears/etc. is just that much worse.
If there's interest, I can also post similar numbers for the MkIV Supra and Mitsubishi EVO VIII. It's enlightening.
EDIT - fixed my arithmetic..
