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Discussion Starter #1
I will do my best to keep it short,

2005 FXT low compression on one cylinder at 105,000 miles when I purchased the car. Have a motor built with all the fixins just shy of closed deck. Forged pistons, rods, STI crank, 1/2" ARP head studs, 272 cams with titanium springs and such in the full valve job. 1000cc injectors, 360 LPH fuel pump etc. Added a full front mount intercooler and a rotated Precision 5558 turbo. The down side is the car is a 4EAT auto trans car. On a Mustang dyno known as the heart breaker it did 359 hp. The shop that built the motor said 550hp was a safe number for the motor when it was built. They also said with the auto it would never get close to that. Fast forward 9 months and the trans is slipping and there is smoke from the tail pipe. I take the car to another shop and they say oil is getting past the seal in the 9 month old turbo and the trans is in its last days.

The solution is a 6 speed swap staying 5x100 and solve turbo issue. For 2 weeks I and the shop have been calling and emailing Precision with no reply to try and get an RMA to send in the turbo. So I am looking at going to a Garrett and chalking the precision up as a loss. My hope is to get the car to as close to 500hp as I can on 93 fuel as I do not have access to E85 near me. It will not be a dedicated track car but more a fun car on the street. The questions, What clutch? The shop wants to put in a stage 3 south bend drag clutch. What turbo? The shop wants to put in a Garrett GTX3076R 0.83 A/R. Is my dream of 500hp just that a dream? The car has all pipe work done and is setup for V band in and out so nothing stock is left under the hood or body. Even with the issues she would pull hard and the boost came on around 3700 RPM and was only at 19psi to try and keep trans alive. 25 to 30 psi is the plan after the trans swap and that has just started. As a side note on the dyno, the same day mine was run a new Nissan GTR was run and did 478hp as a point of reference.

Any one else gone too far that might have some advice?
 

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in stock form, none of the subaru transmissions whether manual or auto are built to hold up to 500 hp or around there, if you are going to do this fully;. get a custom transmission rebuild to make it more stout , beef up the unibody and mounts, ';............. and imo a supercharger, is a better design then a turbo for this boxer engine, although it will require custom intake and reshaping of intake flow, power comes on right away but gradually with engine speed, and there is not sudden power spikes as with a single turbo system, stock exhaust shape remains also , today superchargers can be gear driven, belt driven or electric motor driven, giving you options
 

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Discussion Starter #3
I have a Magnuson 2300 on my truck so I have some experience with chargers. The 6MT beefed up with a good clutch I am doing now. All of the mounts have been changed out for solid mounts already. Body stiffening I have not done but I have gone too far to abandon turbo at this point.
 

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6 speed is pretty stout, should be fine. One thing to get your head around, you can’t just put a big turbo on and crank up the boost. 19 psi is about right for a daily driver on pump gas. To go much higher e85 would help, which you don't have. You can do meth injection, which has a few pitfalls. Or run race gas, not great for a daily driver. Get heavy handed with the boost and the first hard pull with a sub-par tank of gas might be the last.
 

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I'm running an outfront grocery getter with longer rods short block, stx67, grimmspeed topmount/intake/crosspipe/uppipe, cobb ebc, turbo back exhaust. My auto was rebuilt by IPT with an upgraded torque converter. 2" lift with upsized tires. With stock injectors and 91 I put down 315/350 on a mustang. The stock injectors are maxed out and run lean if I push it. I will be upgrading to FI1000's and getting a retune in a couple few months. I'm hoping I break 350hp. I bet the 6 speed will get you closer to 400. Past that, I think you'll need to consider water/meth injection in order to hit 500.
 

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Old thread, no idea if you've made any decision yet - check out the new G series turbos by Garret.
The G25-550 or G25-600 is about right for that level of power, brand new design.

Intended to have big-turbo power with small-turbo spool characteristics.

Even has provision for production-level shaft speed sensor to assist in boost-control tuning to optimise for the turbo's given boost map. V-band mounts also.

I did notice you didnt mention if you are running internal gate or not - at that level I'd be running only external gate or you risk boost spike issues (dont care how well built your engine is, super-heated high-pressure air will knock the teeth out of any block).

The 6-speed should be ok for 500, but it is going to be seriously stressing it out.

For clutch, opt for a multi-plate custom setup - ideally sprung plates - otherwise prepare to have a ridiculously strong/sore leg for proper clutch engagement.
 

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Question for you in regards to your power level and the automatic. How are you driving it? I'm going to be at a similar power level soon, but don't an on regularly tracking it or launching it or anything, was just curious if you think anything besides the power contributed to you issue or not
 

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Discussion Starter #9
The 6 speed is in and the car is alive once more. Base tune is done at this point. Had the turbo rebuilt by a shop in Florida so staying with the Precision for now. On base tune it made 461hp 401tq on a mustang dyno.
 
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