View Single Post
Old 03-04-2012, 11:20 PM   #91 (permalink)
NYBladeZ
A True Z Fanatic
 
NYBladeZ's Avatar
 
Join Date: Apr 2009
Location: New York
Posts: 2,158
Drives: Lotus Exige S
Rep Power: 20
NYBladeZ has a spectacular aura aboutNYBladeZ has a spectacular aura about
Default

First off, I don't need aftermarket forced induction to be knowledgeable on the subject. I've done my research, talked to people experienced on the matter and while my Z still remains N/A (a good decision considering that F.I. options continue to grow i.e. GTM's twin supercharger ) I built a car running forced induction before. Driving one on the norm as opposed to not doesn't make one more knowledgeable than the other. With that said, members with the 7at have repeatedly stated they are hesitant or downright unwilling to achieve their full potential of power and torque because they have the 7AT. So, not only can you NOT hammer it in 5th gear and above, 5th gear being the "cruising" hear for the 7AT's but there is power out there that you can't confidently utilize.

Now you don't have to take my word for it so here is what GTM had to say, I saved you the work of having to do the search for yourself. GTM states:

Generally, when an OEM designs a transmission, they have a specific torque capacity in mind and use this capacity to specify the number of clutch disks used in each clutch pack. The valve body is also programmed to operate these clutch packs in a specified manner. For example, when cruising in 5th gear on a 5 speed automatic, the transmission will only downshift to 4th gear when a certain amount of
pedal pressure is applied for a certain amount of time. Because 5th gear is used mainly for cruising, there are less clutches in the clutch pack and therefore, the ultimate holding capacity is less than that of the lower gears that are used more for accelerating. In the case of a 7 speed automatic, both 6th and 7th use fewer clutch packs with 5th being a transition gear still using fewer clutches than 1st – 4th. When
more power is added, more load is placed on these clutch packs. One way to prevent premature wear of the clutch packs is to modify the valve body to increase hydraulic pressure so that the transmission will downshift more readily. A modified valve body also shifts faster and slips the clutches less to achieve a firmer feeling when the transmission shifts. This keeps the transmission in lower gears when
you are trying to accelerate the car with more torque. On the new 7 speed automatic, line pressure can be increased by reflashing the ECU. When going for serious power, however, increased line pressure simply isn’t enough.

Even with a heavy duty transmission fluid cooler and valve body upgrade, more than doubling the factory rated horsepower requires more extensive work to keep the transmission working well. In this case, it is necessary to overhaul the transmission and replace the clutch packs, pistons that actuate the clutches and drums that hold the clutches with high performance versions. The drums must be enlarged to accommodate additional clutches and a more aggressive friction material must be selected for the clutches themselves. In addition, the piston diameters are increased to apply additional force to the clutch packs. While these modifications increase the holding capacity of the transmission, it is not indestructible as there is only so much room for additional clutch packs, larger drums and pistons.

Ultimately, care must be used when driving a vehicle equipped with an automatic transmission and aftermarket forced induction. When accelerating in a high gear, damage can result with the additional torque. Therefore, it is vital that the driver is aware of the limitations of the transmission and downshift when they want to accelerate. High speed runs at full boost in high gears is inadvisable with an automatic transmission, modified or otherwise. Remember that the transmission was not designed for those operating parameters.

This doesn’t mean that forced induction cannot be added to an automatic transmission equipped car,just that care and caution must be exercised in addition to supporting modifications appropriate to the power level achieved.

I know the UpRev software can effect the shift points etc., that's why its the preferable tuning program and by all means hammer it in any gear you want. Thankfully guys like Sam will be there to assist you when you have failed to exercise "care and caution." All you have to do is bring the $$$.
__________________
2009 Carbon Fiber/Red 370z aka Trish: Sports Package, Meisterschaft full catback, Fast Intentions Longtube Headers, Injen Long Tube Intakes, UpRev Tune: Sold
2008 Lotus Exige S Club Racer aka Bella, always leaves me smiling
NYBladeZ is offline   Reply With Quote