Full build forced induction

[Spartarus]

Originally Posted by flat4-86

The car won't be abused too often, but I was going to look into local auto cross events and some track days here and there. Will the transmission so be in danger? Or is it still uncertain what the transmission will be able to take. ... and what kind of mods will need to be done to the transmission to get it to comfortably hold that amount of power?

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No tested or proven transmission mods out there. There's a straight cut gearset out there from PAR, but it's untested and expensive. Could be great though... Who knows?

From your stated objectives, you should be fine. I mentioned that Element was blowing the trans at 390 to illustrate that it is a weak trans and it won't take a huge beating, but I'll be fair, they're racing the Sh*t out of it: 9krpm, 305 slicks on a widebody, 1000+ lbs downforce, 1+G corners, 150mph, going airborne over a rise in the track etc.

3rd and 4th gears are the ones that shear. If you aren't thrashing the sh*t out of it in those gears, (bangshift, hard launch, clutch dumps, drifting on the rev-limiter) it'll hold together at 400. Around 450 the teeth will literally shear off of the gears (eventually. Not necessarily imediately). There's pictures.

[flat4-86]

Originally Posted by Spartarus

No tested or proven transmission mods out there. There's a straight cut gearset out there from PAR, but it's untested and expensive. Could be great though... Who knows?

From your stated objectives, you should be fine. I mentioned that Element was blowing the trans at 390 to illustrate that it is a weak trans and it won't take a huge beating, but I'll be fair, they're racing the Sh*t out of it: 9krpm, 305 slicks on a widebody, 1000+ lbs downforce, 1+G corners, 150mph, going airborne over a rise in the track etc.

3rd and 4th gears are the ones that shear. If you aren't thrashing the sh*t out of it in those gears, (bangshift, hard launch, clutch dumps, drifting on the rev-limiter) it'll hold together at 400. Around 450 the teeth will literally shear off of the gears (eventually. Not necessarily imediately). There's pictures.

I'm years away from any kind of torture line that on my car.... goal is occasional auto cross with a few weekend Track days at the local tracks, and some high way pulls. ... also not going to go with a tire setup such as that either. Is good to know the transmission will/should handle that power. Thank you for all your advice. Maybe I'll look more into it if I ever get serious with racing

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[BRZoomTX]

Originally Posted by Spartarus

3rd and 4th gears are the ones that shear. If you aren't thrashing the sh*t out of it in those gears, (bangshift, hard launch, clutch dumps, drifting on the rev-limiter) it'll hold together at 400. Around 450 the teeth will literally shear off of the gears (eventually. Not necessarily imediately). There's pictures.

You're referring to HP, correct? Just weird to reference HP because torque is what eats up the gears. Having really conservative mid-range torque while going all out 4-5k+ will help save the trans. Crazy torque in the mid RPM ranges are what causes the issues, both for the stock motor and trans.

[flat4-86]

Originally Posted by BRZoomTX

You're referring to HP, correct? Just weird to reference HP because torque is what eats up the gears. Having really conservative mid-range torque while going all out 4-5k+ will help save the trans. Crazy torque in the mid RPM ranges are what causes the issues, both for the stock motor and trans.

I'm under the assumption that he is referring to the hp rating. I never consistedthe torque figures which i should have. I wasn't expecting more than 300-350wtq...more concerned with achieving high horsepower figures at the 6-8k range.

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[Spartarus]

Originally Posted by BRZoomTX

You're referring to HP, correct? Just weird to reference HP because torque is what eats up the gears. Having really conservative mid-range torque while going all out 4-5k+ will help save the trans. Crazy torque in the mid RPM ranges are what causes the issues, both for the stock motor and trans.

Oh man. Not again. Yeah, I said horsepower, and I had a good reason to say it. Yes, you are technically correct, in the narrowest sense of the word. Let me explain my reasoning, because there are caveats to that statement. I'm sick of seeing the "torque breaks gears" argument, so let me end it for you.

I highlighted your statement. Green for correct, Red for incorrect

I say horsepower because it's a number people recognize, and it's close enough to correct, here's why: Broadly put, these engines share the same torque curve for a given power level at a given boost unless you've done something crazy for low-end like a twin-scroll, or a tiny little turbo. So, it's fair to say "around 450 whp the trans is a time bomb" because the torque curve (and therefore peak torque) required to produce 450 WHP in a given gear, from this engine is broadly similar. It's a narrow, arbitrary, derivative range limited by many fixed factors and very few variables. Coincidentally, the peak torque at 450 whp almost always exceeds the value that the transmission can handle.

That torque value, by the way, is unpublished, unknown as of yet, it is different for every gear, and it goes down as the transmission ages or is abused.

The torque required to achieve a given horsepower in a given gear is arbitrary and derivative, and I don't care.[/B] This is why I say "around 450" because there's some wiggle room, depending on when you hit peak torque. That said, there's not a lot of wiggle room, because the rev range and gear ratios are fixed values.

Yes horsepower is a measure of the rate of mechanical work and doesn't state a specific applied force, rather, hp = (torque x speed) / constant. The gears will break at a specific applied force, and therefore a specific torque, not a specific HP.

Coincidentally, you are right; if you move an unaltered torque curve higher into the rev range, you will make more horsepower with the same torque figure, without applying any more stress to the transmission. Note that I said "unaltered"

If you "go all out," it doesn't matter where in the rev range you do it, the transmission sees the same force, because the gear ratio in a given gear is fixed. All you're changing is the wheel speed at which the unit sh*ts broken metal into the sump.

Here's why, and here's where everybody goes wrong: It's not just input-side torque that matters. It's output side torque as well, because both shafts have gears on them, and both gears have a breaking strength, measured in torque. The shafts are parallel in a constant mesh transmission. There is a fixed distance center-to-center on the shafts, thereby limiting gear size for a given gear ratio. That is why, among other things, they're more likely to break as you reduce the gear ratio. As that happens, the applied force is transmitted closer to the center of the output shaft, requiring more force to achieve the same moment. It's only 2 gears that seem to like to break; so if we assume a fixed gear ratio, then at a given output shaft speed, the output shaft and associated gearing see the same torque regardless of engine torque. As you raise high-end power, you're raising the torque applied.

I'll give you an outlandish illustration of what I'm saying. Skip this if you don't care. A Pratt & Whitney PT6 engine uses a gas turbine to spin a reduction gearbox. The engine peaks out below 150 ft. lbs of torque. It produces 750 HP though. How? That torque is produced at 37,500 RPM. The reduction gearbox runs that down to a very reasonable 2200 RPM, which means the output shaft is holding 1800 ft. lbs. of torque. The gear attached to that shaft doesn't see anything like 1800 ft.lbs. though, because it's five times the diameter of the output shaft. Do the math. Force x arm = Moment The teeth on that gear don't see anything like 1800 lbs. They would shatter. By the way, that gearbox is physically smaller than ours, and it can hold that kind of power. There's no comparison: It's a planetary gearset, but that's why it holds that kind of reduction ratio without breaking.

Whatever, either way, the salient point is regardless of input or output torque, every component in the transmission sees a different applied force. (torque)

Back on topic, to our transmission; 3rd and 4th seem to like to break, but 5th and 6th don't, (at the same input torque) even though they're an even lower reduction ratio. Why? Speculation abound, but the last red statement above is the relevant point here. According to simple "torque breaks gears" logic, they should break sooner if they're the same material, but they don't. Why is it the gear teeth that break and not the engagement teeth? The gear teeth are much bigger, and made of the same material. The best speculation is twofold: the gears are helical. That reduces the contact patch between the gear teeth. 3rd and 4th are the furthest from a bearing, meaning they're the most susceptible to shaft flex, further reducing the surface area in contact. Eventually, as the contact area decreases, force per square mm exceeds the strength of the gear. Also, assuming that's correct, the axial force increases as the shaft flexes, due to the helical cut, and drivetrain loss therefore increases. Considering most dyno runs are dine in 3rd or 4th gear, the correlation between horsepower measured and horsepower produced could be diverging as power increases. If they (5th and 6th) have a smaller helix angle, that could drastically change their breaking strength as well

What I'm saying is, there's more factors than torque. Saying the trans breaks at a certain torque is just as inaccurate and approximate as saying it breaks at a given horsepower. More so, in fact.

edit: changed "dog" to "engagement" because I don't want to argue semantics about that. Regardless, I hope this ends the "torque breaks gears" argument, because I'm sick of seeing it.

[BRZoomTX]

Originally Posted by Spartarus

Oh man. Not again. Yeah, I said horsepower, and I ...[/B]

We're saying the same things. You're just being overly technical, though for good reason. Torque obviously isn't the only cause. That is pretty obvious seeing as how transmissions at the stock power level have been reportedly having problems. I was just replying to your gear shearing comment at 450hp+.

You're right, it won't save the trans. Thats why I said help save the trans. The trans will last a lot longer with peak torque coming in later. Making effort to not power shift and not completely dog on the trans will help even more. It directly translates to less overall abuse, which was my point.

We can get as technical as we want. There are multiple cars around here in DFW running at the 350tq range in excess of 15k+ boosted miles still on their first transmission. With all other abuse out of the equation, delayed peak torque can directly contribute to the stock trans lasting a lot longer. You may need to take a nap between shifts, but it will still last longer. Keeps you well out of peak torque even when getting in to boost while putting around town. That is the important part when we think long term reliability on a street car. Minimal unnecessary stress.

At the end of the day, most people could care less about the details. They want to know what power they can make and for how long. A good answer is to not beat on the trans, keeping your peak torque within the 300 to 350 range with late peak torque. Interpret me saying that however you want. Even then, the trans is still unreliable at that level. That can differ by what you consider reliable of course, but I personally consider getting less than 30k miles out of a street car transmission unreliable on a sub-500hp car.

[flat4-86]

Can someone please assist me then as to a direction to look into or a company to look at for a transmission build. ... as reliability is a huge concern for me with this build. I'm not trying to chew through a transmission in 30,40, or even 50K miles. I would like that something that is going to last and take the occasional thrashing from auto crossing and rare track day use. I'm at a loss of knowledge as to where to search for tranny components

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[spitfire481]

Originally Posted by flat4-86

Can someone please assist me then as to a direction to look into or a company to look at for a transmission build. ... as reliability is a huge concern for me with this build. I'm not trying to chew through a transmission in 30,40, or even 50K miles. I would like that something that is going to last and take the occasional thrashing from auto crossing and rare track day use. I'm at a loss of knowledge as to where to search for tranny components

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Full blowns v160 swap is what you want then

[flat4-86]

Originally Posted by spitfire481

Full blowns v160 swap is what you want then

This is referring to the transmission correct?

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[spitfire481]

Originally Posted by flat4-86

This is referring to the transmission correct?

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Yes

[flat4-86]

Okay, thank you

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[flat4-86]

I noticed ( at least on FBM'S website) that the v160 conversion is only listed for the S2K.... is this correct or do they offer this conversion for the FR-S as well? If so, what other mods will need to be done... ie, drive shaft, diff, axles??? Or is this a direct bolt up option to the factory parts already on the FR-S

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[spitfire481]

Originally Posted by flat4-86

I noticed ( at least on FBM'S website) that the v160 conversion is only listed for the S2K.... is this correct or do they offer this conversion for the FR-S as well? If so, what other mods will need to be done... ie, drive shaft, diff, axles??? Or is this a direct bolt up option to the factory parts already on the FR-S

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Call them and they will tell you everything you need to know. They sell a full bolt up kit (minus the trans itself)

[Spartarus]

v160 swap is crazy expensive. by all accounts, once you find a v160, the swap is $11,000 or so finished. Replacement used stock trans will only run you $600 - $1200. That, and swapping it out is as easy as changing the clutch. It's tempting to fix a problem before it happens, but in this case, it's unlikely to break anything else when it fails.

My advice is sit on a spare stock trans if it makes you feel comfortable, and you will be surprised how long your original transmission lasts. It may outlast your motor. If it ever gives up, swap in the dirt-cheap spare and start looking at other options. Maybe by then there will be a good selection of transmission parts. Right now there isn't. Also gives you the luxury of waiting a long time for a really good deal to come up on a used one. It's what I did.

Besides, if you ever decide, like me, that you need to swap the motor, and you're patient, you can resell it for way more than you paid.