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Old 02-28-2008   #1 (permalink)
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Default Cobra Motor swap in an STi

Andrew,
Hey guys nice to meet all of you J
Need some help with a project… I have an 05 Subi STi and a 96 Cobra mustang. Well long story short I have an extra modular motor laying around and I just recently blew up my STi motor. My idea is to swap the cobra motor to the STi.

Anybody heard of doing this? What is everything I would need to do it?

And I am going to turbo the cobra motor when it’s all done.

I know I will need new motor mounts and stuff but does anybody know how the transmission in the STi would hold up with a motor like that sitting in front of it?

Any info would be good. Thanks in advance
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Old 03-01-2008   #2 (permalink)
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Sounds like a pretty cool idea. I've never heard of anything like this but it would be sweet to see a STI that sounds really good.
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Old 03-03-2008   #3 (permalink)
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how did you blow up an 05 sti? why isn't it under warranty?
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Old 03-04-2008   #4 (permalink)
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Default Blown

Quote:
Originally Posted by codyTHEoutlaw View Post
how did you blow up an 05 sti? why isn't it under warranty?
I'm just guessing, but I know of several folks who void their warranties with aftermarket turbos, BOV's and such...

As for the project, get a tape measure first thing. That DOHC 4.6 is a WIIIDE motor, and its widest point involves the exhaust headers (check for clearance).

I suspect it would NOT fit. The V8 is also a LOT longer than the sub motor.

No way can you use the subaru awd system with that motor. It could never handle the torque of a turbo cobra motor, and the hardware is designed for a FWD platform.

Sorry, you will have to swap in more than just a motor!
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Old 03-04-2008   #5 (permalink)
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I have to disagree about the STi drivetrain not handling the torque, there are some insane modified STi's out there running a $hitload of boost handling the torque just fine. Got my doubts about squeezing it in though. Not only is the DOHC wide, the layout of the boxer motor is short in length and height. I guess you could set it back, drive from the back seat and use the whole drivetrain from the Mustang.
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Old 03-05-2008   #6 (permalink)
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Default Twin Turbo

Typical twin turbo DOHC 4.6 in fighting trim puts out about 1000 foot pounds of torque. The stock STI drivetrain is rated at 360 pounds - and the stock 01 Cobra is too!

So my comment applies to the stock Cobra drivetrain as well.

One way the Subaru system withstands the torque is by splitting the power down the AWD friction-loss (Mercedes Patented) AWD system. Beyond the designed limits, lots of power gets turned into heat or directed to the other end of the car. That's on the STOCK setup. The wise Sub operators have developed mods and added beef to the drivetrain, etc, but that's no longer a stock drivetrain (anymore than the TKO600 in a turbo Cobra is).

This idea of plunking a giant V8 into the STi is a teenage dream anyway - the parts will NOT mate up short of some pretty tough engineering - the whole platform will get thrown out of whack with a giant front end weight bias - and the cooling issues would be enormous given the Cobra's tendency toward those problems even when in a Mustang.
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Old 03-05-2008   #7 (permalink)
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+1 tripleblack
if your wanting to drop a DOHC 4.6 get something like a mazda or old nissan that is already rearwheel drive....with your STi being awd..you'll need to custom make motor mounts, probably custom kmember, the transmissions in some mustangs are extremely large making ground clearance an issue, I don't know the exact wheelbase length of an STi vs 99-04 mustangs but a custom driveshaft will have to be in place....there's just so many things that come into play. In my opinion not worth it when you can just get a foxbody(which are very light) drop a turbo dohc 4.6 in it and wax a$$ in it all day long...or just beef up your STi
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Old 03-05-2008   #8 (permalink)
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sell the STI buy another stang, strip it down make it light as hell and you'll save a ton of time and money. plus the mustangs look way better anyways
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Old 03-05-2008   #9 (permalink)
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OR build the STi yourself to handle insane boost, then boos the S(#*t outta that thing.
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Old 03-09-2008   #10 (permalink)
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[quote=tripleblack;930590]Typical twin turbo DOHC 4.6 in fighting trim puts out about 1000 foot pounds of torque. The stock STI drivetrain is rated at 360 pounds - and the stock 01 Cobra is too!

So my comment applies to the stock Cobra drivetrain as well.

quote]

My apologies, I missed the line about the turbo's in the original post.
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Old 03-09-2008   #11 (permalink)
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I love the exhaust note of a WRX STI! Why change it? I recall a video of a civic hatch with a vette engine in it. Cool idea, was fast, sorta (too much power to weight ratio and the short wheel base made it spin like a top). It's too much trouble for something that already is excellent for what it was meant for. Just the word Subaru creates an image of break-neck speeds through forested trails barely a car wide. I'm thinking if you are having to ask for help around here for a swap like this then I have my doubts, but I don't know you. Set good goals and do work! I think it is possible with the right attitude in mind.
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Old 03-09-2008   #12 (permalink)
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Default Apologies

LOL, apologies accepted (but not necessary).

I think your response was a good one, and not off the beaten path at all. Lots of Mustangers don't know that the STI's come with 300+ HP stock from the factory.

Of course, its always the same old story, "a good big man will (all other things being equal) always beat a good small man".

Or...

"There's no replacement for displacement".

Turbocharge a 2 liter motor and spend $30,000, and you will get X power.

Turbocharge a 4.6 liter motor and spend $30,000, and you get XX power.

Its how physics works.

Its also the reason why 282 cubic inch Mustangs struggle with comparably modified 350 cubic inch Brand C's.

I actually don't mind the "what if" comparisons, so long as it all starts with dollar signs as one of the control points.

I used to own 280Z's, so I'm no Japanophobe, but I also know what building a first class high output car like a twin turbo Supra costs. I had a rather interesting bet going with a Supra owner one time that I could build a Mustang that would easily beat his Supra in the quarter mile, for the same money he had invested in his car.

Of course, he didn't know that I had his build list with notes about what he had spent that he had posted earlier on the site...

When I started listing my proposed buildup (spending over $60,000) on my Mustang, he cried foul, saying that no way had his car cost that much...

When I popped up his own old post, and mentioned that I would be willing to forget and forgive all the recent upgrades he had made (which must surely have greatly added to his total), he never responded and in fact, disappeared from the site.

The huge advantage Mustangs have over virtually all other cars is the low COST of achieving relatively high quality results. There is no doubt that, for instance, one could buy a nice Z car and modify it into a barn-stormer - but also no doubt that, for the same money, one could build a superior Mustang.

Just as it was once said that "Men are NOT created equal, but Mr. Colt changed all that", DOLLARS are the ultimate item to compare when building custom cars.

Just as a 7 liter Corvette starts with a huge advantage over a 4.6 liter Mustang in displacement, and so long as money is not studied the Mustang will be forever playing a game of catchup which it is doomed to lose, as soon as you involve Dollars, the tides of fortune shift to favor the Mustang.

Sure, billionaires could care less about the cost of a car...

But the rest of us sure do.



[quote=04CVPI;936604]
Quote:
Originally Posted by tripleblack View Post
Typical twin turbo DOHC 4.6 in fighting trim puts out about 1000 foot pounds of torque. The stock STI drivetrain is rated at 360 pounds - and the stock 01 Cobra is too!

So my comment applies to the stock Cobra drivetrain as well.

quote]

My apologies, I missed the line about the turbo's in the original post.
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