mrfred

iTrader: (50)

Polish and paint is unlikely to provide much benefit because the tranny is bathed in waste heat from the engine. Tranny cooler is still the best option.

Wheelhaus

iTrader: (2)

I fail to understand why the cooler needs to be under the tranny case unless he was referring to a beefier heatsink... If the oil is pumped to a radiator up front, certainly it would receive more direct cooling air before being pumped back into the case than it would otherwise being under the car. Increased oil capacity is a secondary benefit.

I don't believe you need a race prepped 5sp tranny unless you're tracking a LOT, i.e. more than once or twice per month for more than 20 minute sessions. The standard 5speed trannys have proven durable enough to handle the track, so changing fluid more frequently should be sufficient. If you're paranoid, running an oil cooler should add plenty of insurance.

GTLocke13

iTrader: (1)

If the cooler is above the level of fluid in the transmission, how do you make sure it stays full? (The answer is it won't.)

EvoIXMR

iTrader: (66)

Doesnt the pump pump the fluid thru to keep it cool. Its cycling the fluid - thats how I understand it - I could be wrong.

GTLocke13

iTrader: (1)

Yes, but if the cooler isn't full of fluid it won't dissipate as much heat. You want the fluid to spend a long time in the cooler, and have enough fluid in there to raise the temperature of the cooler so that it radiates heat at a higher rate. If the cooler is full of air and you're just flowing fluid through it, the cooler stays cold and the fluid stays hot (relatively speaking).

The other part is you need more fluid in the system. If the cooler is above the level of fluid in the transmission, you would need a second fill point, and you would never know exactly how much fluid is in the transmission vs in the cooling system at any given time.

Wheelhaus

iTrader: (2)

This part has already been discussed.

Air:
The recommended radiators fill from bottom -> top. When activated, the pump fills from the bottom and forces the air through the system, thus self bleeding.

Backfill:
Many pumps apparently have a backflow diaphragm or simplar check valve. The only additional oil that would "backflow" is that from the return line, which descends back from the highest point at the top of the radiator back to the fill plug. The volume of a single 4ft hose is negligible. If backfill has you paranoid from the pump and radiator, use a high flow one-way check valve on the transmission drain plug. Viola, the oil remains suspended and cannot return unless its pumped.

Volume:
its not difficult to calculate the volume of the pump, radiator, and length of hose. Simply add this to your calculations when determining system volume.

Filling:
The oil suspended in the pump, radiator, and fill line would be old. If a switchable check valve exists then you could drain the whole system at once. If not... Fill the system, run the pump for a few minutes to ensure its full. Open the fill plug on the tranny (oil return line from the radiator) and fill the system until it spills out the fill plug like normal. Now the tranny is full, pump/radiator/hoses are full, and so long as you have a check valve it won't overfill the tranny.

GTLocke13

iTrader: (1)

Well, that does solve the problems I was seeing. I wouldn't exactly call that system "bomb proof" though. Too much room for user error. If you're selling stuff to the general public you have to build it so a half-trained monkey can use it, or you'll get a bunch of people coming back and saying your oil cooler blew up their transmission.

GEARS

iTrader: (5)

Let me try to clear up the location of the oil cooler...

I only recommended that the oil cooler be positioned low enough so that it is below the oil level in the transmission for the reason that when you have the pump turned off the transmission is not overfilled with oil.

Too much oil can lead to things such as aeration, foaming or webbing which doesn't lubricate all that well and can produce heat. Now this can be resolved by installing a one-way check ball on each side of the cooler so that the cooler retains the oil in the circuit, keeping the transmission oil at the desired level.

I don't mind where you install the oil cooler, as long it has plenty of airflow to it and it's not in a place where it could be damaged. Just don't skimp on the size of the cooler and you'll be fine.

Wheelhaus

iTrader: (2)

Gotcha.

timmiii

iTrader: (3)

I was wondering. Many FQ owners choose the car with the 6 speed transmission, how many of them have actually broken? In addition, the FQ-400 has a lot of power, wasn't Ralliart UK and Mitsumotors aware of the overheating issue with the 6 speed transmissions? If they were aware of this problem then what did they do to somewhat remedy it for the FQ series?

If what JON at TRE says is true and infact the 6 speed transmission cannot hold that much power, shouldn't the 6 speed in the FQ340 which MASE tuned here in the states have shredded 4th gear on the dyno or during the number of pulls performed ont eh street?

Sorry to go back to this topic, but I've just been thinking about it recently and to me it doesn't make much sense.

DaWorstPlaya

iTrader: (31)

It's torque that shreds gear and not HP. You can have a high HP # with relatively low torque, think Honda with a higher rev limit and run weaker gears with less failure due to metal fatigue. The FQ400 comes with rebuilt engine internals and hugh laggy turbo. All the power comes late in the powerband. You can get away with smaller gears (6 speed) when you aren't producing much torque. Higher RPMs also means more heat is produced in the tranny.

While I do feel that heat contributes, I don't think it is the main factor in all the failures. Put simply, the 4-5-6 gears are too small for some of the power levels people wish to put down. Keep your torque levels lower than 290TQ and you shouldn't have a problem. I think I've mentioned this multiple time through this thread. Cooling will help but its no substitue for stouter gears (5 speed).

timmiii

iTrader: (3)

The FQ-400 has 405bhp and 355ft-lbs of torque. If what you say is infact true, then shouldn't many other FQ owners or other 6 speed owners in other countries shredded 4th gear as well?

donour

iTrader: (6)

Not at the wheels it doesn't.

This is a tough one to tell, how many FQ400, FQ360, and FQ320s were sold? How many were tracked?

d

timmiii

iTrader: (3)

I understand it isn't to the wheels, but it's still more than what a standard evo gets to the wheels. Also Jon @ TRE did only say 280 to 290ft-lbs of tq and didn't specify where the numbers really came from besides from "Mitsubishi".

GEARS

iTrader: (5)

A few years ago when I first started rebuilding the 6 speed transmissions I had an opportunity to speak with an engineer at Mitsubishi about the 6 speed. They are well aware of the skepticism that surrounds the 6 speed but that doesn’t change the fact that the transmission is rated for 290ft.lbs of torque. I know... I didn't like to hear that either and it would have been nice if they shared that with us, the end users who can't stop thinking about the EVO.

This rating is what the transmission can deal with for the duration of the intended service life with an OEM clutch. We can assume that the intended service life would be just far enough to get through warranty. Sure you can shove more torque through the 6 speed but the number of cycles that the transmission can withstand before the probability of failure catching up to it will be less & less. This is the S/N fatigue curve and transmissions can’t escape from it either, especially when you’re attempting something that it wasn’t designed to do.

The whole trick is knowing the bleeding edge and backing away a few steps. In the case of the 6 speed I wouldn’t want to make it take anymore than 400ft.lbs if you are looking to get the most life out of it. Think of it like revving a stock block 4G63 past 8k, sure you can do it but for how long?