4eat be made to handle more?

[david_12121]

So some of you might remember my inquisitions about turbocharging. I'm finally getting to it after the suspension modifications on the SVX and all the work I've done to my RX7 (V8 swapped + superchaged)
So the turbo will happen and I'm shooting for 350-400 crank, for now (not sure how good I can get at megasquirting!). So let's go with 320whp, ~320wtq!
Unfortunately projects are expensive and I wouldn't have enough for a dccd, and I don't wanna deal with a 5mt breaking on me cuz of the torque.

So I was thinking of keeping the stock auto for a few months until I get a 6mt.
Do you guys think it can handle the power under the following conditions:
-I already have a pretty large cooler on it
-If I do not ever let it shift on its own while under power, as in I manumatic it, and let it rev down before shifting...
-never break boost and have an eye on the atf temp
-If I have to, weld the center "diff" and make it rwd!

I know this seems idiotic to many of you, and I understand why it would but I'd appreciate any info you can give me on that.

[Chucksta]

Just sayin'...

They aren't know to "grenade".. they are more known to fail for other reasons. Subaru designed the TCU / ECU to give mushy shifts. It was, after all, not meant to be a racer, it was designed to be a gentleman's GT cruiser. The factory settings gave slow, luxurious, barely noticeable shifts. "Unobtrusive" would be a good adjective to describe what Subaru aimed for. A shift kit would definitely help, as far as longevity is concerned. Limiting slippage helps keep heat and wear down to a dull roar. Excessive slippage results in excessive particulate in the transmission fluid, which results in clogged "campaign" filters, clogged passages, poor cooling and premature transmission failure. And Subaru also designed the TCU / ECU to limit engine output at WOT to "cushion" the shifts and avoid drive train shock. Some shift kits use a vacuum signal to change the resistor circuit of the transmission to raise line pressure to firm up the shifts and are simple to install and relatively inexpensive to purchase, but operate in an either "on", or "off" mode, and don't address the ECU power cut off at WOT shifts. Other shift kits, which are more expensive and require a more involved / complicated installation, progressively firm up the shifts by progressively increasing line pressure in relation to throttle pressure, and bypass the factory reduction of engine output at WOT shifts. Personally, I like the soft shifts at low throttle, and the hard snap of a full line pressure shift with no power reduction when I've got it mashed to the floor. When I engage "warp drive", I don't want impulse power. ( yeah, I'm a geek).

Hmmm.. Break a 5MT with the torque? Define "break"..LOL.. A lot of people say they broke one, but there's a huge difference between breaking it with torque, and breaking it shifting .. or missing a shift. The SVX is a heavy car, the result of that, as far as transmissions go, is that it is brutal on the drivetrain to pull all 4 loose.. I've got an '02 WRX that makes well over 300 H.P. 250,000 on the original transmission, second clutch courtesy of Subaru due to a silent recall for shuddering. However, I don't have a performance clutch, it's the bone stock after recall upgrade. If I bang it off the rev limiter and sidestep the clutch..and I DO mean side step, not "pop".. whatta ya think happens? Well, it slips!! It leaves like I got ass ended by a semi, the tach stays at 5K until it hooks up, rips to 7,250 RPM.. I leave my foot on the floor, bang it into second, side step the clutch again,and my accellerometer says I hit 60 MPH in 4.9 seconds.. And when I come to a stop... yes.. I can smell clutch. I love the smell of over heated organics in the morning!! I've only done that to her three times. Once to see if I could hit 60 MPH in less than 5 seconds, and twice for money. The factory clutch is designed to slip under that level of abuse, rather than strip output shaft splines or bust transmission gear teeth. Subaru designed them like that to avoid warrantee claims.. Bust a gear? might be their fault... Smoke the clutch... It's definitely on you.. A 5 MT might be a bit more fragile than a 6 MT, but enough abuse will still bust parts no matter what.. It's just a matter of when. Hot tires, hot pavement, 320 HP and a grabby clutch, with 3,500 pounds pressing the rubber to the road.... Sooner or later.. Bang! Wooot, woot, wooot bang! Crap! I need a tow truck,..sucks!

I don't know enough about the valve body of a 4EAT to give you a definitive opinion, but I'm not sure if manually shifting while backing off the throttle is best or not. The transmission has accumulators and springs and valves and reservoirs and the TCU talks to the ECU, which talks to the TPS... Etc, etc... If backing off the throttle lowers the line pressure, it might be better to let the trans do it's thing, especially if you toss a shift kit in. Some searching of this forum would probably find a thread about that, especially as I know there's a mixed school of thought about leaving the shifter in third gear around town.. Also, make sure the brake band is set properly. If you've got a sloppy 2 / 3 shift, be sure to check the setting.

Keep an eye on the ATF temp gauge? Do you have a stand alone gauge, or are you referring to the idiot light on the dash? If you're going by the light on the dash, by the time it's lighting up, it might be a bit late. You've got a "pretty large cooler".. As long as it's properly mounted where it gets tons of air flow, overheating shouldn't be an issue.

No clue about welding the center diff.. did you mean with the manual transmission? The USDM 4EAT is 90 /10 until the front wheels slip, then it splits power up to 50 /50 .. There are cheap, almost free mods that would let you pre select that electrically, so that 4WD is engaged before you mash the happy pedal. Those kinda mods are just a search away. they're quick too.

Then... there's the "Elephant in the room".. Why the manual transmission? Granted, some people just don't feel like they're driving unless they're driving a stick. If that's the case, then have at it! But, If it's a matter of performance, reliability, cost...have you considered it'd probably be half the cost for a 4.44 swap? A 4.44 trans, 320 WHP..you'd be looking at low 13s' in the 1/4 mile... all day every day. Personally, I love the stock gearing of the SVX, the low revs on the highway. It's my cruiser, that turns heads and still will smoke a lot of stuff, especially from 50 to 80 MPH. My WRX is my bantam weight blitzer. But hey!.. The best part of having your own toys is getting to do what you want with them!

Post back what you decide..

Good luck, have fun..

[svxfiles]

Originally Posted by Chucksta

Just sayin'...

They aren't know to "grenade".. they are more known to fail for other reasons. Subaru designed the TCU / ECU to give mushy shifts. It was, after all, not meant to be a racer, it was designed to be a gentleman's GT cruiser. The factory settings gave slow, luxurious, barely noticeable shifts. "Unobtrusive" would be a good adjective to describe what Subaru aimed for. A shift kit would definitely help, as far as longevity is concerned. Limiting slippage helps keep heat and wear down to a dull roar. Excessive slippage results in excessive particulate in the transmission fluid, which results in clogged "campaign" filters, clogged passages, poor cooling and premature transmission failure. And Subaru also designed the TCU / ECU to limit engine output at WOT to "cushion" the shifts and avoid drive train shock. Some shift kits use a vacuum signal to change the resistor circuit of the transmission to raise line pressure to firm up the shifts and are simple to install and relatively inexpensive to purchase, but operate in an either "on", or "off" mode, and don't address the ECU power cut off at WOT shifts. Other shift kits, which are more expensive and require a more involved / complicated installation, progressively firm up the shifts by progressively increasing line pressure in relation to throttle pressure, and bypass the factory reduction of engine output at WOT shifts. Personally, I like the soft shifts at low throttle, and the hard snap of a full line pressure shift with no power reduction when I've got it mashed to the floor. When I engage "warp drive", I don't want impulse power. ( yeah, I'm a geek).

Hmmm.. Break a 5MT with the torque? Define "break"..LOL.. A lot of people say they broke one, but there's a huge difference between breaking it with torque, and breaking it shifting .. or missing a shift. The SVX is a heavy car, the result of that, as far as transmissions go, is that it is brutal on the drivetrain to pull all 4 loose.. I've got an '02 WRX that makes well over 300 H.P. 250,000 on the original transmission, second clutch courtesy of Subaru due to a silent recall for shuddering. However, I don't have a performance clutch, it's the bone stock after recall upgrade. If I bang it off the rev limiter and sidestep the clutch..and I DO mean side step, not "pop".. whatta ya think happens? Well, it slips!! It leaves like I got ass ended by a semi, the tach stays at 5K until it hooks up, rips to 7,250 RPM.. I leave my foot on the floor, bang it into second, side step the clutch again,and my accellerometer says I hit 60 MPH in 4.9 seconds.. And when I come to a stop... yes.. I can smell clutch. I love the smell of over heated organics in the morning!! I've only done that to her three times. Once to see if I could hit 60 MPH in less than 5 seconds, and twice for money. The factory clutch is designed to slip under that level of abuse, rather than strip output shaft splines or bust transmission gear teeth. Subaru designed them like that to avoid warrantee claims.. Bust a gear? might be their fault... Smoke the clutch... It's definitely on you.. A 5 MT might be a bit more fragile than a 6 MT, but enough abuse will still bust parts no matter what.. It's just a matter of when. Hot tires, hot pavement, 320 HP and a grabby clutch, with 3,500 pounds pressing the rubber to the road.... Sooner or later.. Bang! Wooot, woot, wooot bang! Crap! I need a tow truck,..sucks!

I don't know enough about the valve body of a 4EAT to give you a definitive opinion, but I'm not sure if manually shifting while backing off the throttle is best or not. The transmission has accumulators and springs and valves and reservoirs and the TCU talks to the ECU, which talks to the TPS... Etc, etc... If backing off the throttle lowers the line pressure, it might be better to let the trans do it's thing, especially if you toss a shift kit in. Some searching of this forum would probably find a thread about that, especially as I know there's a mixed school of thought about leaving the shifter in third gear around town.. Also, make sure the brake band is set properly. If you've got a sloppy 2 / 3 shift, be sure to check the setting.

Keep an eye on the ATF temp gauge? Do you have a stand alone gauge, or are you referring to the idiot light on the dash? If you're going by the light on the dash, by the time it's lighting up, it might be a bit late. You've got a "pretty large cooler".. As long as it's properly mounted where it gets tons of air flow, overheating shouldn't be an issue.

No clue about welding the center diff.. did you mean with the manual transmission? The USDM 4EAT is 90 /10 until the front wheels slip, then it splits power up to 50 /50 .. There are cheap, almost free mods that would let you pre select that electrically, so that 4WD is engaged before you mash the happy pedal. Those kinda mods are just a search away. they're quick too.

Then... there's the "Elephant in the room".. Why the manual transmission? Granted, some people just don't feel like they're driving unless they're driving a stick. If that's the case, then have at it! But, If it's a matter of performance, reliability, cost...have you considered it'd probably be half the cost for a 4.44 swap? A 4.44 trans, 320 WHP..you'd be looking at low 13s' in the 1/4 mile... all day every day. Personally, I love the stock gearing of the SVX, the low revs on the highway. It's my cruiser, that turns heads and still will smoke a lot of stuff, especially from 50 to 80 MPH. My WRX is my bantam weight blitzer. But hey!.. The best part of having your own toys is getting to do what you want with them!

Post back what you decide..

Good luck, have fun..

I think that you mean that a manual is TWICE the cost of a 4.44.
Not saying that it is not a good way to go, but its alot more money to go stick.

[Chucksta]

"But, If it's a matter of performance, reliability, cost...have you considered it'd probably be half the cost for a 4.44 swap? "

Umm.. half the cost FOR a 4.44 swap ... Not half the cost OF 4.44 swap.

I think I know what I meant to say, but I realize that what I think I meant isn't what I think you heard. It could be that that you think I meant what I think I said, but I'm not sure if I accidentally obfuscated ... Ahhh screw it..

Thanks for the clarity!!

You definitely clarified what I meant.... Cool!!

Thanks.

Chuck.

[david_12121]

I'll try to touch up on all the points you guys brought up

-So you're telling me that a shift kit on a stock 4eat will make it handle 320wtq on a +3600lb car? I've heard good things about them but that seems like an awful lot of torque and weight for just a shift kit to make much of a difference!

-break a 5mt? I have been told by 2 friends with bugeyes that they both broke theirs, after a short while, one with 280w and one with 300w. One broke his 2nd gear, yes broke the actual gear, and the 2nd hasn't disassembled it yet. If that happens with less power, in a lighter car, I doubt it'll take the SVX much time to break it. Yes, both those guys are idiot drivers who deserve Hondas but I'd rather baby a 4eat than baby a 5mt.

-Regarding the valve body, I have no idea, that's why I was asking you guys.

-Yes, standalone sensor. Cooler mounted between the AC condenser and the radiator. I'll probably take out the AC at that point, so even more flow.
I believe it was a 9000gvwr, and people said it's too big for the SVX but I don't live ina cold area.

-I think someone used some tool from subie and it said it's between 70/30 and 50/50 but the chattering clutch is not one to handle that much power. So it's somewhat common for people to weld the clutch pack and take out the front axles! Easier to slip the tires, less stress on tranny!

-I don't want an auto, never enjoyed it and never will. The SVX is my weekend car, I commute on a motorcycle so it needs a manual.

Thanks for the help, Chuck...I'm used to getting shut down for my "insane" ideas!

[NiftySVX]

Lots of stuff to clear up here. You need to be monitoring the temp in the pan. Cooler line temp means nothing. The SVX stock has a very good transmission temp stabilizing system that works quite well unless you have a modified engine making substantially more power or a high stall converter.

The filter that was put on the early cars was a mistake and shouldn't have been done. Hopefully everyone has replaced their radiator and converter by now. That filter was a really dumb idea.

As for the transfer clutch, that is not how it works. It doesn't just hang out with some value. That is how many manufacturers worked that tried to copy the subaru system. It is based on the theory of predictive modeling. That is to say, the "Subaru all wheel driving system" (I just love to use their silly name) actually does what they advertised. It tries to anticipate wheel spin and stop it from happening. It was a state of the art system at that time. Let me try and illustrate:

The age old argument about the MPT clutch having a certain torque split is really just an exercise in futility. The clutch is constantly changing. So realistically you can have a torque split of, say, 5% or so when cruising in 4th at low throttle. In manual 1 it is more like 30-40%. In 2 at half throttle it might be 25%. In reverse it is something like 32%. If it slips at all it defaults back to its close to 50-50. Problem is that these transmissions don't have the line pressure to lock that clutch together. You can easily spin the front wheels on a low traction surface and the tcu will try but it can't/won't put enough pressure back to the rear to truly "lock" the thing. This is why I did what I did with my pump, transfer clutch, and line pressure when I still ran that system.

If you remove the front axles on an automatic that has the MPT you will break it in a big hurry. The transfer clutch hub is tiny and is spot welded on the reduction drive gear at the back of the output shaft. I've seen them break just from messed up duty Cs on AWD cars so I wouldn't try it…I wouldn't even try to drive an SVX with the old school "locked" the way some do. (these are just guesses/experience talking here)

If you want to do some math, you can make a roundabout calc, it will show the stock SVX 4eat should be good for something like 350 or more horsepower. But again, that was done by some of us as more of a mental exercise.

I would guess that taking an early SVX forward clutch with 8pc and a late model hc with all the holes and the small bearing and the newer hub and reverse drum, getting some pretty good accum springs, and modifying the pump and or software to increase base line should give you a 4eat that would hold up to a lot. I would probably take a donor trans, say a 1994 or newer SVX unit, tear it down, put a 4.11 or 4.44 gear in it and make those modifications if I wanted to build a strong 4EAT. But I am not aware of anyone who has done that.

I built mine this way but with a stock pump and a 3.70 ratio with VTD and I don't expect to have any problems out of it.