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Old 09-21-2010, 08:51 PM   #51
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If anyone is interested I am selling my Raptor SC kit, PM if interested.
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Old 09-21-2010, 09:47 PM   #52
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it really comes down to how youre going to control detonation. there are only a few ways to do it, all of which are not cheap. you can run high octane gas all the time, run low timing, run low boost, throw a bunch of mods at the motor to promote good breathing habits, etc.

i wouldnt go straight for building the block or lowering compression ratio. there are other ways to do it without spending that much money. id suspect if you did a cam swap that would help to bleed boost (you need overlap of when the valves were open), a nice sized header, intake, exhaust, and a GOOD TUNE you could pull off 10-12 pounds of boost on the car without a ton of difficulty. the deciding factor here is going to be you running your tune on the ragged edge or being really conservative with it. when you run it really close to points where you'd get detonation the second you get a nice cool day the car will make more boost and youll turn a piston or four into dust.

the same thing goes even with motors built with low compression specifically for boost. you cant run the motor on the ragged edge of blowing up unless youre constantly logging and tweaking your tune.

10-12PSI on stock 2.5i internals with just a good tune and exhaust components for a DD I think is a pipe dream dude.
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Old 09-22-2010, 12:04 PM   #53
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what makes the internals so brittle? so long as youre not detonating, they should take it just fine. im not saying im right, but what makes them so weak?
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Old 09-22-2010, 01:18 PM   #54
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what makes the internals so brittle? so long as youre not detonating, they should take it just fine. im not saying im right, but what makes them so weak?
They are just not made for boost... Some people argue 5 psi is ok with good EM.. that's not even proven. I would be willing to say 10-12 PSI bone stock internals, exhaust and EM would make a very problematic daily driver.
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Old 09-22-2010, 01:51 PM   #55
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They are just not made for boost... Some people argue 5 psi is ok with good EM.. that's not even proven.
Depends on your definition of "proven".
Some people are still running on a Ludespeed Turbo kit at 6psi after many years.
A few are still running a FAT stage 3 with no issues.
Some people blew up their 5psi DIY kit after 2 months.
Others still have had 10psi for years.
I've been running 5psi of Supercharged boost for 2 years now.
None of which is proof, just examples.
The trend does however seem to be that less people have trouble at or below 6psi.
It's become the accepted recommended boost level for the NA scoob. Not a rule, just a norm.
Then there is the change in Pistons for the.. what was it.. '05 model?
Plenty of reputable people saying they were even less forgiving on boost.
In other words, there is no hard-and-fast rule! Just guidelines and a rule-of-thumb.

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I would be willing to say 10-12 PSI bone stock internals, exhaust and EM would make a very problematic daily driver.
I'd be inclined to agree. 10psi on a 10:1 motor is a crap load! Not just for stress on the internals (ring lands), but the power it'll make too. As someone who Daily Drives a 5psi 00RS, I an tell you right now, there is NOTHING wrong with a 5-6psi boosted RS/2.5i. If you've never been in one, then take my word for it, it's plenty of fun. 7-8psi is a hoot and 2/3s!!

Target 10-12 psi if you have a power goal in mind. Fair enough. But, if your just looking for a bit of fun and an increase in power, KISS (keep it simple) and just do the lower 5-8psi. It's just proven to be less likely to go Kaboom when compared to the higher boosted NAs.

Last edited by Skidd; 09-22-2010 at 01:57 PM.
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Old 09-22-2010, 02:02 PM   #56
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The main issue is the fuel used. It isn't able to support high compression and any reasonable amount of boost before igniting by itself. This is why the turboed cars run 8.0:1 to 8.5:1. You can step to another fuel, E85 for example, and you can get more of both. E85 will let you run stock 10:1 and add up to a couple bars of boost without detonating. However, if you're stuck with 91 octane, you're only option to run any significant level of boost is to drop static compression. Can you run boost with the stock internals, sure. You just can't run much, and not much boost equals not much gains either for the money you're putting into the mod. In retrospect, you can completely rebuild the motor with lower compression pistons, buy all the necessary turbo hardware, and run a more appropriate turbo package on pump gas for less and while making another 50% power over what the high compression, low boost setup can do.

I do question the fragility of the stock internals. I would say the pistons are not specifically designed for it, but the main issue is people attempting to crank up boost and timing and repeatedly getting knock. This is how internals break very easily, even on WRXs and STIs.
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Old 09-22-2010, 04:44 PM   #57
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The main issue is the fuel used. It isn't able to support high compression and any reasonable amount of boost before igniting by itself. This is why the turboed cars run 8.0:1 to 8.5:1. You can step to another fuel, E85 for example, and you can get more of both. E85 will let you run stock 10:1 and add up to a couple bars of boost without detonating. However, if you're stuck with 91 octane, you're only option to run any significant level of boost is to drop static compression. Can you run boost with the stock internals, sure. You just can't run much, and not much boost equals not much gains either for the money you're putting into the mod. In retrospect, you can completely rebuild the motor with lower compression pistons, buy all the necessary turbo hardware, and run a more appropriate turbo package on pump gas for less and while making another 50% power over what the high compression, low boost setup can do.

I do question the fragility of the stock internals. I would say the pistons are not specifically designed for it, but the main issue is people attempting to crank up boost and timing and repeatedly getting knock. This is how internals break very easily, even on WRXs and STIs.
It's probably a lot easier and cheaper to make a low-comp, high-boost engine feel more like N/A when off boost, and have the turbo spool up faster, than have a high-comp, low-boost engine produce more top-end power.
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Old 09-22-2010, 04:55 PM   #58
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The main issue is the fuel used. It isn't able to support high compression and any reasonable amount of boost before igniting by itself. This is why the turboed cars run 8.0:1 to 8.5:1. You can step to another fuel, E85 for example, and you can get more of both. E85 will let you run stock 10:1 and add up to a couple bars of boost without detonating. However, if you're stuck with 91 octane, you're only option to run any significant level of boost is to drop static compression. Can you run boost with the stock internals, sure. You just can't run much, and not much boost equals not much gains either for the money you're putting into the mod. In retrospect, you can completely rebuild the motor with lower compression pistons, buy all the necessary turbo hardware, and run a more appropriate turbo package on pump gas for less and while making another 50% power over what the high compression, low boost setup can do.

I do question the fragility of the stock internals. I would say the pistons are not specifically designed for it, but the main issue is people attempting to crank up boost and timing and repeatedly getting knock. This is how internals break very easily, even on WRXs and STIs.
This is a great post by you as always... I also agree with Skidd. It's not that Im am anti boost on the 2.5i and am saying it is not possible.. I don't feel the risk is worth the reward on 2002+ cars.. not to sound like a broken record, but when a turbo model designed for boost is readily available. It seems like many at first believe it to be a better cheaper option to buy a N/A and boost it on your own to save over the slightly higher WRX price.. My whole point in posting over and over agin on the issue, is that is not good logic.
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Old 09-22-2010, 05:27 PM   #59
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This is true but with EM being even better these days those risks can be taken. The Cobb unit I have is an amazing piece of hardware that's 1 for fighting det. My 2 core intercooler which drops intake charge by a good bit is 2. Me running 93 oct. Down here is 3 with an occasional 103 oct fill up every once in a while is 3. My colder plugs that I'm running is 4. With 2 and 3 that is fine for say 7 psi of boost. Again I don't gave to worry about boost spike on a SC. There is a guy running the kit 2 years running on 9 psi on an ej20 no issues. Along with my walbro and 440cc injectors I don't think I'll have a problem with running 9-10 psi. I can honestly say next year I want my built tech works block so the need to worry about motor isn't there for me. She is a DD but I also own a wrangler lifted jeep and a gixxer 600 so I gave loads of transportation just gottah pick one that's all. When built block comes she'll be at 14 psi and crazy fun. Right now it's fun on it's own.
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Old 09-22-2010, 05:34 PM   #60
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I think it's also for the factor of not many n/a set ups are boosting. Or the blocks at least. With work the blocks can run fine with not a care in the world. That with forged 10:1 pistons and or not rods it's a beast. 2.5i internals are actually really nicely put together. Bearings seem to be better rods and crank too. Once timing is right pistons work just fine with no issues. And that's with getting a good tune and leaving everything as is. Not messing around with it. People seem to think you have to keep playing with tunes once there set. Not true. Once it's tuned just oil maintenance is needed. My motor is at 19k I really think she will last till next year when new block is in. Low
Mileage helps my issue aswell.
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Old 09-22-2010, 07:22 PM   #61
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your tune will definitely have to change along with the weather unless you run it conservative enough. if you think otherwise then you're wrong.
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Old 09-22-2010, 07:27 PM   #62
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Wow, a mention of the FAT kit. That takes me back...

Jacob
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Old 09-22-2010, 07:35 PM   #63
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Wow, a mention of the FAT kit. That takes me back...

Jacob
What if I was to say "Minnam"?
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Old 09-23-2010, 02:03 AM   #64
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your tune will definitely have to change along with the weather unless you run it conservative enough. if you think otherwise then you're wrong.
I think other wise actually..I live in the tropics..its 80 degrees year round minus maybe lowest of 70 during the winter..and 95 during the summer. Again conservative should be every tune unless your building a race car lol Other than that its based on sea levels and what not..where as my highest peak might 1500 ft ASL and there aren't any cars going that high only wranglers in off road conditions..so say 1000 feet above for me to 0 at sea level. Until I have an issue or anyone else around with Subbys here in the islands then I'll take your word for it. Until then its get a good tune and leave it alone..maybe adjust for oct. levels but mostly its 93 and I'm sure the computer ca naccount for the fuel so no real need to adjust with software.
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Old 09-23-2010, 08:58 AM   #65
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well arent you lucky, mr. nice weather all year round. yes, that is me being jealous.

the problem with where i live is that its 80* outside in summer and 15* in winter. given that, i make more boost and command more timing in winter. under the wrong situation that means my motor just blew up.
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Old 09-27-2010, 02:57 PM   #66
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what makes the internals so brittle? so long as youre not detonating, they should take it just fine. im not saying im right, but what makes them so weak?
Metallurgically speaking non turbo rods and pistons are cast and not forged so the shear strength is far less btwn the two iterations of the metal. Think about a cast iron skillet and a fancy Paula Dean skillet. If you take a ball peen hammer and tap on a cast Iron or Aluminum skillet over and over it will crack but f it were forged it wold take the abuse while maintaining its structural integrity.

Cast iron or grey iron and cast Al have the same shear strength characteristics that are great for low impact infrequent acute forces not high boost detonation
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Old 09-27-2010, 04:51 PM   #67
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Neither of the USDM WRX or STi pistons are forged.
Rods are different from 2.5RS to WRX/STi but I don't think they're forged either.
EJ Cranks are the same throughout.


Materials-wise, EJ engines are very, similar, the biggest differences are this:
1. Piston face and Compression
2. Open-deck design


Suffice to say: #1 matters the most. People in the past have blamed the lack of boost-ability of the N/A blocks due to the open-deck design, but the true issue is actually the compression. 10:1 static compression with 5 psi of boost is a LOT to ask for even on built engines running pump gas. It's just the limit of physics, ie Ideal Gas Law.

And that's only figuring in static compression. I assure you the N/A piston face is quite different from the turbo pistons. This makes dynamic compression very high, and adding boost is just a bad idea.

While superchargers are pretty cool, this supercharger is just in essence a belt-driven turbo. I wish beyond wishing that I could use this viably, but in my head the math doesn't add up.

On the other hand I would love to see someone use this kit on a WRX block and pistons, and see what happens.
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Old 09-27-2010, 05:24 PM   #68
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assuming im coming from a car with hypeuretic pistons that break the top of the piston off in the 1:00 area whenever you run too much boost (heat) because of the piston ring gap closing up and snapping off the top skirt of the piston...what makes these more prone to 'sploding? i dont care for forged things, they just cost more and are just as easy to break if your tune isn't in check anyway. yeah, they'll take a hit or two, but they'll still bite the dust under severe detonation.

yeah, you can always lower the compression ratio and run more boost...but what fun is that? the problem with low CR cars is that out of boost they SUCK for driveability. given that you put enough money into the motor to run a good amount of boost (~15psi) the high CR car would not only make great amounts of power, but it'd drive very nicely even just cruising. i get that 10:1 is high, but there is no way in hell that if you put ported heads, cams, and a nicely sized header/intake combo that you couldnt run at least 10 pounds of boost on the car. i'm thinking it'd take more.

also, the CSC setup this kit actually is outdoes any other blower out there by miles. roots blowers suck and turbos are somewhat 'random' at times. a supercharged setup is always predictable and very easy to tune with the linear powerband it creates.
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Old 09-27-2010, 09:38 PM   #69
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On the other hand I would love to see someone use this kit on a WRX block and pistons, and see what happens.
Take a look at the Forced air technologies compound charged STi. it is supercharged and turbocharged. That's really a great application for cars with considerable lag with upgraded turbos.

If I remember correct it had a larger GT35 turbo and so the supercharger, when the switch was turned on, gave it the instant power and TQ while quickly fully spooling that large turbo for no lag.

EDIT:

their 2005 shop car was actually twin turbo and super charged too with dual GT30R turbos.

Last edited by Audi20Tdriver; 09-27-2010 at 09:44 PM.
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Old 09-27-2010, 09:59 PM   #70
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assuming im coming from a car with hypeuretic pistons that break the top of the piston off in the 1:00 area whenever you run too much boost (heat) because of the piston ring gap closing up and snapping off the top skirt of the piston...what makes these more prone to 'sploding? i dont care for forged things, they just cost more and are just as easy to break if your tune isn't in check anyway. yeah, they'll take a hit or two, but they'll still bite the dust under severe detonation.

yeah, you can always lower the compression ratio and run more boost...but what fun is that? the problem with low CR cars is that out of boost they SUCK for driveability. given that you put enough money into the motor to run a good amount of boost (~15psi) the high CR car would not only make great amounts of power, but it'd drive very nicely even just cruising. i get that 10:1 is high, but there is no way in hell that if you put ported heads, cams, and a nicely sized header/intake combo that you couldnt run at least 10 pounds of boost on the car. i'm thinking it'd take more.

also, the CSC setup this kit actually is outdoes any other blower out there by miles. roots blowers suck and turbos are somewhat 'random' at times. a supercharged setup is always predictable and very easy to tune with the linear powerband it creates.
You could run cams with very long duration to reduce dynamic CR. Over in the built engine forum the "high CR boost" build is considered starting with around 9-9.5:1 SCR and going from there.

I also forgot about how Subarus have a very unoptimized CC design. Normally, I would say, "Yes, I'm all for that, and it's all possible!" but these engines are too detonation prone because it the CC.

Lower Compression Ratios such as found on WRX and STi are not as bad as one might make it out to be. Sure they're kind of crappy as they are stock, and back when it was the 05 models with the 2.0L peaky thing with a wanky turbo... not my cup of tea, and insurance was too much...

However, I recall williaty saying he built an EJ257 with PnP heads, intake, turbo outlet, and some extra other stuff to reduce power lost when off boost. He said it was the first turbo car he actually didn't absolutely hate. Knowing him, that means a lot. I recall him saying that it felt N/A when off boost and had nice power when the turbo started to roll in.

In the end, I feel like this is a better option overall, and cheaper, and you still win in the end.
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Old 09-27-2010, 10:53 PM   #71
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Neither of the USDM WRX or STi pistons are forged.
Rods are different from 2.5RS to WRX/STi but I don't think they're forged either.
EJ Cranks are the same throughout.


Materials-wise, EJ engines are very, similar, the biggest differences are this:
1. Piston face and Compression
2. Open-deck design


Suffice to say: #1 matters the most. People in the past have blamed the lack of boost-ability of the N/A blocks due to the open-deck design, but the true issue is actually the compression. 10:1 static compression with 5 psi of boost is a LOT to ask for even on built engines running pump gas. It's just the limit of physics, ie Ideal Gas Law.

And that's only figuring in static compression. I assure you the N/A piston face is quite different from the turbo pistons. This makes dynamic compression very high, and adding boost is just a bad idea.

While superchargers are pretty cool, this supercharger is just in essence a belt-driven turbo. I wish beyond wishing that I could use this viably, but in my head the math doesn't add up.

On the other hand I would love to see someone use this kit on a WRX block and pistons, and see what happens.
Wrx block EJ20 are the same as Sohc blocks , only 2006 +up got the semi-closed EJ255 block
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Old 09-27-2010, 11:34 PM   #72
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Wrx block EJ20 are the same as Sohc blocks , only 2006 +up got the semi-closed EJ255 block
Well there you have it... one more thing to cross off the list.
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