Hey all, silly question but I'm just curious as to what I'd need to reach 450hp, whist also preserving as much torque as possible. The car as it stands is a 2006 STi Spec D, and the engine work its had done when my dad had it, from what I know of, without seeing the full invoice for the work is as follows;

Forged rods and pistons (unsure what make)
STi Nitrided crank
Cosworth head gaskets
ARP headstuds
660cc injectors
Scoobyclinic fuel rails
Ecutek ECU
Walboro 255 fuel pump
Few other little supporting things I can't remember exactly

The car is still on oem 2.5 semiclosed block, stock oem top mount, and I THINK stock turbo, 15 psi peak boost at around late 3000 rpm ish. It currently has been running about 330hp with about 475ft lbs of torque and I love it, heaps of fun and I've kinda gotten used to it with it being my daily but I'm just curious as in the next few years once I've got the cosmetic stuff done, I wanna go for 450hp and I'm wondering what it'll cost considering the (admittedly) vague mod list I have given. I'll probably also be going for better brakes as I'm not sure the standard brembos would be able to keep up, even with how good they are at the current power level. I was thinking maybe I'll need bigger injectors, bigger turbo, and an uprated top mount like the perrin one, Process west top mount, etc... Don't want to have to go front mount unless absolutely necessary.

As I said I'm Not thinking about buying stuff this month or anything but future plans over a couple years and I'm just curious of the cost to get there reliably. Thanks!

 

The only thing i feel qualified to answer is to go fmic, i wasted years trying to get what i wanted out of a grimspeed tmic, you just get so much heat soak because its sat on top of the engine.

 

Really all you need is a set of injectors and a larger turbo (assuming you have a decent flowing intake and downpipe already). People have hit over 400bhp on top mount intercoolers but heat soak becomes an issue, and you’ll see your ECU pull timing if you are sat at a set of lights for a while and pull away aggressively. A decent front mount will be able to control your intake temps much better.

There’s a number of standard locations turbos that will see you reach 450bhp, I tan an MDX321T myself and found it to be an extremely capable and fast spooling turbo. I have also driven a car with a GTX3071r which also spooled very nicely and made a great road car.

I would also look to add a decent set of headers in to the equation too, and a Harvey up-pipe matched to your chosen turbo from Alyn at AS Performance will further enhance your setup.

 

Yes a 3071r has been on my radar becuase of the early spool and capability of it, also good notes about the ecu and the timing I'll bear that in mind. Heatsoak is gonna be an issue if I stay tmic but I'll see if I can find a way to keep it cool somehow. After hearing other peoples stories on reaching 400-500hp I thought I'd need a lot more.

my car does have a 3 inch system with only a catted downpipe so that's pretty free flowing! Essentially you're telling me I could hit mid 400hp with something like 800cc injectors, gt3071r, and MAYBE a bigger top mount? That's actually fairly surprising if so. Thank you for your input, when the time comes I'll be sure to look back to this post

 

​​​​​​Heatsoak is my main worry, I know uprated top mounts are capable of 450 so if I do stay top mount, I'll get myself an intake temp gauge so I can keep track of what's going on so that I know nothing is getting too crazy. As long as I'm not sitting in stop start traffic or dealing with the heat like we've had recently then I should be relatively okay...

Obviously front mount would net the best gains and be much better for the engine but the slow spooling and need to cut the bumper is something I don't want to have to do. But if its necessary then I'll cross that bridge when we get to it.

Wanna wait until next year at least, when my insurance drops below 3k! lol

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Essentially, yes, the issue with the 2.5 engine isn’t making the power, its maintaining reliability. The standard SCD case halves will support 450, and the hard work has already been done for you with forged internals, decent head gaskets and a decent ECU. It’s just a case of bolting on something that’ll flow enough and a set of injectors that will provide the fuel, have it all mapped in and away you go.

 

I personally think the slow spooling with a front mount is a bit of a myth. With cooler charge temps a decent mapper will be able to run more aggressive timing to help spool the turbo earlier, which negates any minimal lag you might see. And there’s FMIC kits on the market that shouldn’t require any cutting.

 

Awesome! yeah I just wanna make sure it's going to last, obviously not WOT everywhere in every single gear bouncing off the limiter but something that can take a little bit of a shakedown every so often and be okay. I know its also got a really good aftermarket Exedy clutch, and flywheel so it should be able to hold it down at that power. Sounds good!

 

If I can do it without cutting then I might consider it, but again just for ease of install I'd rather go top mount. I'll stick TMIC and if it doesn't work then I'll slap myself for not listening to you lol but I reckon if I do it all properly I should be relatively okay. Either way it's gonna be a hell of a fun car

 

You can still get good results on a top mount, there’s certainly no issues there. Keep us all posted won’t you.

 

Yes when the time comes I'll be sure to post pictures, got some good ideas for where I want to take it. Fully custom exterior and Interior parts and stuff like that before more power because its already fun at 300 odd bhp for the time being, cheers for giving your experiences so I know what to be ready for

 

Hi.
When you're ready if you need any help with insurance at all then please feel free to drop me a line.
Regards,
Dan.

 

[QUOTE=DAN@ADRIAN FLUX;12123938]Hi.
When you're ready if you need any help with insurance at all then please feel free to drop me a line.
Regards,
Yes you will and when he changes power mid year you cane the hell out of him on the price .

 

That 2.5 will fall to pieces literally at 450 hp

 

[QUOTE=lockheed;12123939]

 

At that power level you will definitely need a bigger flowing fuel pump particularly with bigger injectors