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Discussion Starter · #1 ·
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..
 

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Great job with the research and calculations
 

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I won't be too surprised when I see aftermarket axles coming out shortly. It will be a lot better w/ a true LSD on the car as well, makes the load on the axles more even.
 

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Discussion Starter · #7 ·
Where are they breaking? I haven't seen a pic yet.

If they're shearing at the root of the transmission spline, there's pretty much no hope.
 

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From what I've heard, it's the inner joint. I don't believe they are shearing at the root of the transmission spline.
 

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Discussion Starter · #9 ·
Shearing or cracking at the inner joint? Shearing at the splines on the axle where the cross goes on? It might be damn difficult to solve this problem...

2500 ftlbs is nothing to sneeze at...
 

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Discussion Starter · #13 ·
Some more numbers for you:

Instantaneous acceleration at peak torque in first gear with a 185 lb driver is 26.22 ft/sec^2. Not quite one G (32ft/sec^2), but still respectable. For you metric guys, it's 7.97 m/sec^2. That's why we launch as near peak torque as possible...too bad first gear runs out so quickly. Here's the rest of the bad news...this assumes 15% power loss through the geartrain/axles:

1st - 22.29
2nd - 12.89
3rd - 8.40
4th - 6.12
5th - 4.88

Again, assuming perfect traction, no wind resistance, etc., YMMV.

Here are the numbers for the automatic assuming 18% loss:

1st - 15.70
2nd - 8.75
3rd - 5.62
4th - 4.06

Pretty easy to see why the manual is so much spunkier.
 

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Discussion Starter · #14 ·

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Originally posted by lo bux racer@Oct 23 2005, 01:55 AM
Pretty easy to see why the manual is so much spunkier.
Yeah. I occasionaly drive my buddies auto tC. Besides my left leg yelling at me telling me how bored he is, there is a huge difference in acceleration, torque, and overall driving impression. I can't imagine how crazy it'll be once I get the SC installed!!!

I can't even sleep now, I'm just so high strung thinking about it!!!!!

THE DAY HAS COME. I can't believe how long it has been though. I first started reading about it like a year ago. Wow.

No more Cobalt SS beatings, no more RSX Spankings, it's time to put these punks in there place. (no lance, with the tC... hehe).
 

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Sounds sweet, it's cool that it's out. It's like finally learning that big foot wasn't just some tall, hairy guy on a nudist colony.
 

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If it's making dang-near 200hp at the wheels, it's putting out at least as much crank hp as a 2.0liter WRX and the, "area under the curve," is way larger to boot--far more driveable (not counting the wrongwheeldrive)! With less weight and lower cost, tC is rockin'!

Subaru's not playing around, though; that '06 2.5liter WRX is probably scorchin'!

-Ed
 

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Discussion Starter · #18 ·
Yeah, and from looking at the dynos, if the redline went up, so would the power. Torque is barely dropping at all at redline. Now it really make sense only to shift at redline in all gears.
 

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I'm going to wait till Spring to get mine installed. What's the point of having the power right now when it's about to snow up here in NY?


It can wait though. It will give me some extra time to throw some cash together for it, so i won't feel it like i would now!


Btw, the price of premium fuel sux. Ugh. But it'll be worth it
 

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Time for me to admit where i was wrong. About all those numbers you put out there lance i like the SC now still iwsh it put out more power but all of you guys saying that waranty and ann the other benefits are worth more money well ill agree now. Since i have gotten in my accident i see things in a different light. The fact that toyota is geting me all there parts why would i want to put anything else on my car unless it was from Toyota, And besides i can always get an SAFC to put a lil more power out there so you know what i am thinkig of going out there and geting a loan to get my self a S/C and have sparks toyota put it in for me. I admit i was wrong and follish for what i was thinking b4 and i am not affraid to say you guys were right. Thatx for talking me out of turbo fellas i want to keep this car for a long time and turbo just wouldnt do it for me so thax for puting the numbers and the facts out there.
 
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