Does it need forged?
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From: harlow
My logic was that if AF is confident to map a WRX to circa 390bhp, he must be fairly confident it's going to last the mapping session?
I'm all up for making a solid engine, if that's what is required to get into the 12's, but I'm just making sure it's totally required
I'm all up for making a solid engine, if that's what is required to get into the 12's, but I'm just making sure it's totally required
Last edited by boosted; Nov 19, 2014 at 03:35 PM.
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From: Holywell
I'm not sure about all the 9 engine failures, I switched off when he said all he wanted was to be able to bounce it off the rev limiter in every gear, I quoted him 10K and said call me!! Your problem with a wrx engine as Ive said is the pistons will crack around the ring lands under the extra boost and the rods will let go at high revs. Don't forget it could take your turbo out as well.
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From: Hampshire
You know what happened to my pistons running a 16G...
I would forge your spare engine, pistons and rods, maybe even make it a 2.1 (
), then you'll have a strong base to work from, because when you decide you want to get into the 11's you won't need a new engine.
STi pistons are apparently only good until around 450, but I don't think they're that much stronger than WRX items personally.
I put a 2.1 in mine because i wanted to do it once properly and future proof it.
But I still think you should see if your hashed up wrx lump will cope before swapping the engine
I would forge your spare engine, pistons and rods, maybe even make it a 2.1 (
), then you'll have a strong base to work from, because when you decide you want to get into the 11's you won't need a new engine. STi pistons are apparently only good until around 450, but I don't think they're that much stronger than WRX items personally.
I put a 2.1 in mine because i wanted to do it once properly and future proof it.
But I still think you should see if your hashed up wrx lump will cope before swapping the engine
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From: Torpoint
Only slightly concern with the engine I'm running (and have been since I built it 6000 miles ago) is that it's a bitsa.
Was a £60 na engine I got off a farm, covered in mud beside a landrover, swapped my WRX pistons into it after honing the bores (never split the casings)
Then re used the MLS steel head gaskets as they looked fresh enough. Wee wipe of hylomar on them. Re used head bolts and put it all back together. Re used oil pump, Clean and new oil and filter obviously. Other than a bit of piston slap when it's cold it performs well at 1.5 bar on the 16g. Taking the pi55 trying to put 360hp through it maybe.
Hence the spare engine or two...
Cheapest (successful) WRX rebuild after big end failure ever?
Was a £60 na engine I got off a farm, covered in mud beside a landrover, swapped my WRX pistons into it after honing the bores (never split the casings)
Then re used the MLS steel head gaskets as they looked fresh enough. Wee wipe of hylomar on them. Re used head bolts and put it all back together. Re used oil pump, Clean and new oil and filter obviously. Other than a bit of piston slap when it's cold it performs well at 1.5 bar on the 16g. Taking the pi55 trying to put 360hp through it maybe.
Hence the spare engine or two...
Cheapest (successful) WRX rebuild after big end failure ever?
Now if you are going to pull a WRX block apart and not use a STi block to go over 350 bhp then it would be because you dont want to muck about with different mapping for the various versions of sensors. That's my case. I will be going for lighter forged pistons for the simple reason that they are going to put less stress on the bottom end bearings at high revs. Essentially you don't need new conrods at 350 bhp but if you want a more power later and you have the engine open then you may as well do them too. Generally 1.5 bar is considered to be more than enough most tuners don't tune a WRX to that level due to the risk of detonation , ( I safely get away with 1.45bar as I have 102 octane here) instead the tuners work and will suggest mods to you for the torque curve particularly if you have WRX 5 spd you should concern yourself with that first. Oh and don't forget to improve the clutch the OEM will burn nicely at 350bhp , I use a Excedy blue very carefully (almost like a fuse to protect the 5spd ) and accept that it won't last long. If I spend money and my time on new pistons I would use a new oil cooler and pump and maybe radiator as I would not want to have to repeat the excercise. Successful engine builders are scrupulously clean. Hope all this makes sense.
Im going to say it , I also have a 16g and my 2 second long >1.5 bar experience killed my WRX motor. albeit it was caused by the MBC jamming because I was kiding myself that I could wait for another week for a new WG and had put too much pretension on the Std one. Lesson Learned. Now if you are going to pull a WRX block apart and not use a STi block to go over 350 bhp then it would be because you dont want to muck about with different mapping for the various versions of sensors. That's my case. I will be going for lighter forged pistons for the simple reason that they are going to put less stress on the bottom end bearings at high revs. Essentially you don't need new conrods at 350 bhp but if you want a more power later and you have the engine open then you may as well do them too. Generally 1.5 bar is considered to be more than enough most tuners don't tune a WRX to that level due to the risk of detonation , ( I safely get away with 1.45bar as I have 102 octane here) instead the tuners work and will suggest mods to you for the torque curve particularly if you have WRX 5 spd you should concern yourself with that first. Oh and don't forget to improve the clutch the OEM will burn nicely at 350bhp ,
I use a Excedy blue very carefully (almost like a fuse to protect the 5spd ) and accept that it won't last long. If I spend money and my time on new pistons I would use a new oil cooler and pump and maybe radiator as I would not want to have to repeat the excercise. Successful engine builders are scrupulously clean. Hope all this makes sense.
Now if you are going to pull a WRX block apart and not use a STi block to go over 350 bhp then it would be because you dont want to muck about with different mapping for the various versions of sensors. That's my case. I will be going for lighter forged pistons for the simple reason that they are going to put less stress on the bottom end bearings at high revs. Essentially you don't need new conrods at 350 bhp but if you want a more power later and you have the engine open then you may as well do them too. Generally 1.5 bar is considered to be more than enough most tuners don't tune a WRX to that level due to the risk of detonation , ( I safely get away with 1.45bar as I have 102 octane here) instead the tuners work and will suggest mods to you for the torque curve particularly if you have WRX 5 spd you should concern yourself with that first. Oh and don't forget to improve the clutch the OEM will burn nicely at 350bhp , I use a Excedy blue very carefully (almost like a fuse to protect the 5spd ) and accept that it won't last long. If I spend money and my time on new pistons I would use a new oil cooler and pump and maybe radiator as I would not want to have to repeat the excercise. Successful engine builders are scrupulously clean. Hope all this makes sense.
I personally don't think tuning a wrx engine is a problem at all, as said earlier in the thread if its capable of 500+hp in odb form then I wouldn't worry too mucch as long as you use decent internals
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From: harlow
Im going to say it , I also have a 16g and my 2 second long >1.5 bar experience killed my WRX motor. albeit it was caused by the MBC jamming because I was kiding myself that I could wait for another week for a new WG and had put too much pretension on the Std one. Lesson Learned. Now if you are going to pull a WRX block apart and not use a STi block to go over 350 bhp then it would be because you dont want to muck about with different mapping for the various versions of sensors. That's my case. I will be going for lighter forged pistons for the simple reason that they are going to put less stress on the bottom end bearings at high revs. Essentially you don't need new conrods at 350 bhp but if you want a more power later and you have the engine open then you may as well do them too. Generally 1.5 bar is considered to be more than enough most tuners don't tune a WRX to that level due to the risk of detonation , ( I safely get away with 1.45bar as I have 102 octane here) instead the tuners work and will suggest mods to you for the torque curve particularly if you have WRX 5 spd you should concern yourself with that first. Oh and don't forget to improve the clutch the OEM will burn nicely at 350bhp ,
I use a Excedy blue very carefully (almost like a fuse to protect the 5spd ) and accept that it won't last long. If I spend money and my time on new pistons I would use a new oil cooler and pump and maybe radiator as I would not want to have to repeat the excercise. Successful engine builders are scrupulously clean. Hope all this makes sense.
Now if you are going to pull a WRX block apart and not use a STi block to go over 350 bhp then it would be because you dont want to muck about with different mapping for the various versions of sensors. That's my case. I will be going for lighter forged pistons for the simple reason that they are going to put less stress on the bottom end bearings at high revs. Essentially you don't need new conrods at 350 bhp but if you want a more power later and you have the engine open then you may as well do them too. Generally 1.5 bar is considered to be more than enough most tuners don't tune a WRX to that level due to the risk of detonation , ( I safely get away with 1.45bar as I have 102 octane here) instead the tuners work and will suggest mods to you for the torque curve particularly if you have WRX 5 spd you should concern yourself with that first. Oh and don't forget to improve the clutch the OEM will burn nicely at 350bhp , I use a Excedy blue very carefully (almost like a fuse to protect the 5spd ) and accept that it won't last long. If I spend money and my time on new pistons I would use a new oil cooler and pump and maybe radiator as I would not want to have to repeat the excercise. Successful engine builders are scrupulously clean. Hope all this makes sense.
I think everyone is right here, I'm going to make it as forged as I can afford to. It's an old car and I'm not spending a fortune on it, so probably H beam rods and a set of STI pistons. The turbo I've just bought is only good for 370ish so that's where I'm heading just now.
Oh gearbox and clutch are just fine mate;
https://www.scoobynet.com/general-technical-10/1012846-audi-quattro-6-sp-impreza-conversion.html
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From: harlow
You know what happened to my pistons running a 16G...
I would forge your spare engine, pistons and rods, maybe even make it a 2.1 (), then you'll have a strong base to work from, because when you decide you want to get into the 11's you won't need a new engine.
STi pistons are apparently only good until around 450, but I don't think they're that much stronger than WRX items personally.
I put a 2.1 in mine because i wanted to do it once properly and future proof it.
But I still think you should see if your hashed up wrx lump will cope before swapping the engine
I would forge your spare engine, pistons and rods, maybe even make it a 2.1 (
), then you'll have a strong base to work from, because when you decide you want to get into the 11's you won't need a new engine. STi pistons are apparently only good until around 450, but I don't think they're that much stronger than WRX items personally.
I put a 2.1 in mine because i wanted to do it once properly and future proof it.
But I still think you should see if your hashed up wrx lump will cope before swapping the engine
Hmmm 2.1 sounds expensive, I've got three 2.0 cranks and blocks lying about, be silly not to use what I have.
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From: Holywell
You may damage your crank if you crack a piston, the debris/oil can cause it to hydraulic and bend the crank or flatten the big end bearing, if you loose a rod you will most likely loose the crank, and maybe the block as well.
I'm not trying to pee on your plans, just sharing what ive found out the hard way over the past years. If you do plan on pushing it to destruction, why don't you run it as a project thread, i'm sure alot of people will want to see the failure points as/if they occur?
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From: harlow
I'm most probably going to build the decent engine and fit it, then wind up the boost.
I'll remove my good running WRX engine as my get out of jail free card.
Thanks for everyone's useful input here, a few people have now helped me make up my mind with the direction I am going.
Probably;
WRX block (same as NA)
WRX crank (same as NA)
WRX oil pump
Std head gaskets and bolts
Forged H section con rods (£225)
Fresh bearings (£95)
STI v5 pistons
Probably ported headers, big injectors, TD05h 20g (7cm) 1.6-1.7 bar on optimax.
We thinking 360-370bhp reliably?
And hopefully a 12 second 1/4 mile
I'll remove my good running WRX engine as my get out of jail free card.
Thanks for everyone's useful input here, a few people have now helped me make up my mind with the direction I am going.
Probably;
WRX block (same as NA)
WRX crank (same as NA)
WRX oil pump
Std head gaskets and bolts
Forged H section con rods (£225)
Fresh bearings (£95)
STI v5 pistons
Probably ported headers, big injectors, TD05h 20g (7cm) 1.6-1.7 bar on optimax.
We thinking 360-370bhp reliably?
And hopefully a 12 second 1/4 mile
The engine running 400bhp in a friend's WRX (20g and standard internals I think) lasted about 3 years before the bottom end finally went due to the additional power - was very noisy after that! 
A friend whose WRX blob ran a billet 18g ran the block on just shy of 380bhp and it ended up with cylinder 3 misfires and a partially melted piston, and he rebuilt it with forged pistons (no rods though).
In standard form I guess it depends how much boost you stick through it and how much abuse you give it!
A friend whose WRX blob ran a billet 18g ran the block on just shy of 380bhp and it ended up with cylinder 3 misfires and a partially melted piston, and he rebuilt it with forged pistons (no rods though).
In standard form I guess it depends how much boost you stick through it and how much abuse you give it!
Last edited by MrNoisy; Nov 20, 2014 at 03:27 PM.
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