Can someone explain these things? Is it a worthwhile mod for my setup (2005 Coupe 5AT).

Where do you buy them? Who makes them? Where is Jimmy Hoffa?

All important questions I need to know.

Thanks,

Jeff

 

A TC is a torque multiplication device. The easiest way to describe how one works is to visualize two fans facing each other. When you turn one fan on, the other fan will eventually start to turn in the same direction. Instead of air being the media, fluid is the media in the TC. This is basically how it works. Believe it or not, fluid movement is the connection and acceleration forced between the engine and the tranny under all driving situation except when the TC is locked. That is the only time there is a mechanical connection (like a manual tranny). The fluid movement is also the main reason automatics loose more power through the drivetrain.

To get better launching performance, a lot of racers go for a higher stall and more efficent TC. A higher stall TC will allow you to launch harder (higher rpm with a ton more torque) and the efficency of the upgraded TC won't bleed off as much power once you're underway. Many Lexus GS400 owners go with upgraded TCs and they drop about .3-.4 seconds in ET. However, the G35's TC has a much higher stall speed (~2,800rpms vs 2,300rpms) than the GS400 so seeing the types of gains the GS400 owners see is unlikely.

The downside to a higher stall TC is around the town part throttle acceleration. The car will feel lethargic because there will be more RPM needed to move the car intially. Though a quality higher stall TC that has maybe 500-700rpms more stall will probably drive very close to stock. The TC will also generate more heat therefore you'll need a better tranny cooler. Gas MPGs will also suffer in city driving because of the additional slippage.

Where to get one? Do a search because there are a couple members on here that have them.

 

DaveB, That was an awesome explaination- This should be pinned.

 

Thanks, I agree. This needs to be put at the top and kept.

Thanks again!

 

So I'm guessing my best best is.......and please correct me if you see something inaccurate:

Upgrade my gearing to 3.5 or 3.9
Get torque converter
Get a tranny cooling system
-----------------------------------------
All this and my automatic will become a beast

 

I've been researching this and I think it may be a good mod to get that low end torque on launching a 5AT. The current TC in our cars (data from 2004 5AT coupe service manual) has a stall of 2600-2900 and I learned (from GurgenPB) that it has a multiplier of 1.6.

That is already a really high stall speed and probably the reason 5AT get crappy gas mileage, but also why we can keep up with (i refrained from saying "blow by" ) 6MT cars easily on launching. ISMSolutions with an upgraded TC (stall 3600) was able to get 60' times of 1.6s - amazing!

I've looked at multiple stock G35 dynos and the torque curve is "pretty" flat down low though most dynos drop off below 3k rpm, so... I've been thinking of getting an upgraded TC that is more efficient, has a torque multiplier of 2, but lowers the stall speed to 2400-2600 rpm. My goal is to increase launch torque while increasing fuel efficiency and low to mid range driveability.

I need some free time to discuss this with folks over at EdgeRacing (as referred by GurgenPB). Any thoughts are welcome...

(Also if anyone can post a link to a dyno that shows a stock G35 torque curve down to 2k rpm that would be awesome - thanks!)

 

I'd definitely recommend you do further research as some may have forgotten a few things.

Here's a few of my research notes from an article that was never finished. I believe they're fundamentally correct.

Torque Converter components and functions:
1. The basic components of a modern Torque Converter are the cover, impeller or pump, the stator & sprag and the turbine.
2. The torque converter body is comprised of the cover, impeller & drive hub.
3. The cover is bolted to the engine’s “drive plate” (Nissan’s term). When the engine rotates the torque converter body moves at the same rpm.
4. The impeller “pumps” ATF to stator and turbine.
5. The impeller’s drive hub is mounted through the transmissions front seal and “locks” into the transmissions pump.
6. The turbine is “splined” to the automatic transmission’s input shaft. When the turbine moves the transmission’s input shaft moves.
7. The stator is mounted on a stationary “Stator Support Shaft”.
8. The primary purpose of the stator is to provide initial torque multiplication. WITHOUT THE STATOR A TORQUE CONVERTER IS ONLY A FLUID COUPLING.
9. The stator’s “sprag” is a one way mechanical clutch that allows the stator to work with the turbine during initial acceleration and then spin free.
10. TORQUE MULTIPLICATION OCCURES WHEN THE STATOR IS MOVING SLOWER THAN THE TURBINE. Usually the first 60 feet os so.

Notes from conversation with Andre at Edge Racing 4/16/04:
1. Stator is mounted on a stationary “Stator Support Shaft”.
2. In Park or Neutral - ATF flows from the AT pump (if TC is not 100% full) through the impeller, stationary stator, turbine and back to the impeller.
3. In Park or Neutral - The turbine is “inactive”
4. The torque converter always rotates in the same direction as the engine.
5. The Impeller and Turbine move in opposite directions. Therefore the engine and transmission’s input shaft also move in opposite directions.
6. Most if not all TC’s operate fully “charged” or full of fluid.
7. Power braking is pre-loading the stator.
8. A properly designed stator “cloaks” once the turbine speed exceeds the stator’s speed.
9. What well on the track may not work well on the street.

DaveO
Custom Street Edge TC 11/20/03

 

Thank you for the extremely in-depth explanation. Now, since I am auto technology retarded, basically this is a great mod that may work in some applications, but may not necessarily be for me. Am I reading you correctly?

 

TC are upgraded primarily for improving launch but also dictate when/how the engine engages the transmission (i.e. at what rpm will it be directly coupled). So you can alter driveability and drivetrain efficiency as well.

Sometimes you can get the best of all worlds - improve acceleration, driveability and fuel efficiency.

However, the question is whether a better sweet spot can be found on the G35, because I have found that our stock TCs look to have pretty darn good specs. The STR (stall torque ratio) I got from GurgenPB is wrong I think - I read in the 2004 Coupe manual that the ratio is actually 2.0. That's already pretty high. And stall speed is pretty high. So what's left to improve? I have an e-mail sent off to Andre to see if he can answer this question. Will let you know what he says...

 

Get rid of that programmed bog in 1st gear. I wish TS would focus on trying to get rid of this "nanny". The 350Z 5ATs don't have this bog hence the reason they can yank 1.9 60 foots on street tires whereas we're stuck with 2.1+.

 

You can learn more at www.howstuffworks.com

 

That's an interesting tidbit I didn't know. I wonder if the difference is in the TC? Anyone have the service manual specs for the 350Z 5AT? Stall speed and STR in particular.

I have no doubt that someone can make a more efficient TC with less drivetrain loss and better launch characterisitics. I just don't know if it can be made *significantly* better than the one we already have. GurgenPB went through quite the trial and error process (and then he went FI which changes everything) and I just don't see myself changing out this part more than once.

 

Most of the technical explanations are WAY over my head... but I have driven DaveO's car and strongly considered a TQ afterwards! Not so much for the launch - mine is pretty good, but his mid range torque blows the snot out of my car (although I'd bring it back in the end).

Gurgen did go through a lot of trial and error - with his turbo too... I think he and DaveO would be good resources - they both have 'em and I'm sure would be happy to share their experience/knowledge.

Personally I'm waiting to get more warranty under my belt before tearing into motor and drivertrain.

 

On the 350 z the stall is 2100 rpm. Thats what they told me as i am looking to change mine to a Pro torque converter next year with a 2900 stall. I expect to get 2 tenths of a second from that mod and may be 2 tenths from slicks.
Best 60 ft time 1.925 (hit the limiter and ran a 13.2
average 60 ft time 2.062 = 13.1. It should go 12.8 with these mod. ( fully modified SC stillen.

 

From experience -

3.92 gears and the TC at about 3600 rocks! You'll need some real tire after the mods, but it rocks!

go to www.actperformance.com - they re-work your TC for up to 3600 stall. I picked one up at a yard for $110 and sent it over for the rebuild.

For more info - look for my posts..pretty in-depth. BTW - drive-ability and mileage impact = ZERO