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Old 02-04-2020, 09:16 AM   #1
BurninSTI
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Default Shortblock Build for the LOLZ

Thinking about starting to piece together a shortblock to make a trackday monster yet still a DD.

9.5:1 or higher pistons and possible destroke, I want to hear that popcorn for the lolz and panty droppins

May or may not throw some cams in it to let it breath better as I'll be keeping the stock turbo. I'm thinking with the higher compression and rev limit alone I could be looking at ~400 WHP?
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Old 02-04-2020, 10:14 AM   #2
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Thinking about starting to piece together a shortblock to make a trackday monster yet still a DD.

9.5:1 or higher pistons and possible destroke, I want to hear that popcorn for the lolz and panty droppins

May or may not throw some cams in it to let it breath better as I'll be keeping the stock turbo. I'm thinking with the higher compression and rev limit alone I could be looking at ~400 WHP?
Might go read more about the de-strokers.

When i hear de-stroker, stock cams and stock turbo the package is very contradictory in that one of those things likes rpm and the other two things hit a wall by 6500 rpm typically.
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Old 02-04-2020, 12:19 PM   #3
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Uh not really, I've had a cammed stock turbo sti before and it absolutely ripped on a stock turbo, I'm most concerned with having a larger rpm range available than absolute hp, like I said I'm looking for around 400whp. More particularly a larger high hp rpm range with little or no lag. 4-9k would be ideal with the stock sti gearing, hit about 65-70 in second, perhaps 110 in 3rd, not quite sure of those numbers but that's the idea. Hold boost and power so the shift can happen on the straight, not a corner. Who says you cant use nitrous up top either if you absolutely need that hit?
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Old 02-04-2020, 02:48 PM   #4
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that 9.5 compression is going to be really hard to make power on pump, if you are going to use 100 or e it would be. what I have found is there really is no magic turbo out there. they have gotten better but to have a turbo that makes power from 3500 all the way to 9000 is tough. the best bet is a spoolinator with a 3067 or a efr 7163. subarus make their power with timing its not like the evos. so lots of boost is good but you need timing to really make power
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Old 02-04-2020, 03:56 PM   #5
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You are not hitting 400whp on a stock turbo.... just not happening. They don't move enough air to support 400 whp.

Some of your statements are fairly contradictory as gc8 and Scuby mentioned. There is no "magical best of both worlds turbo." The oem turbo runs out of steam before redline on an oem EJ25, when you increase the amount of air the engine can take in and get out on each cycle there is just no way that little snail can keep up. Get an FP blue or Dom turbo and go from there if you really want 400whp.
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Old 02-05-2020, 01:38 AM   #6
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Was thinking about running methanol or tolulene injection along with it and by God if I need to I'll put a bottle on it... but really how is that higher compression and cams not going to put it roughly 100 hp above a good stage 2/3 build.
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Old 02-05-2020, 09:31 AM   #7
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Uh not really, I've had a cammed stock turbo sti before and it absolutely ripped on a stock turbo, I'm most concerned with having a larger rpm range available than absolute hp, like I said I'm looking for around 400whp. More particularly a larger high hp rpm range with little or no lag. 4-9k would be ideal with the stock sti gearing, hit about 65-70 in second, perhaps 110 in 3rd, not quite sure of those numbers but that's the idea. Hold boost and power so the shift can happen on the straight, not a corner. Who says you cant use nitrous up top either if you absolutely need that hit?
I bet it ripped, but I would also bet it had the power rolling over not still climbing till redline (or even holding). Now add 2k rpm and what is the point? Why rev when it makes less and less whp? I love rpm think everyone should roll around over 4k all day but it needs the right combination of parts to flow the air up there.

Go look at a turbo match bot, toss in the information you have on the combination you plan to run and look at the amount of air you need to get past that little turbo to make 400whp up in that 7-9k rpm range.
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Old 02-05-2020, 12:08 PM   #8
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Was thinking about running methanol or tolulene injection along with it and by God if I need to I'll put a bottle on it... but really how is that higher compression and cams not going to put it roughly 100 hp above a good stage 2/3 build.
Because you are still using forced induction to supply the air that motor is taking in and putting out. That means the amount of air the turbo is capable of moving will ultimately limit your power potential. Fuel is not the only component necessary to complete combustion, you need AIR. You still need enough air to burn whatever fuel you inject(methanol, nitrous, etc) or you are just dumping more fuel than you are capable or burning into the chamber creating a rich condition. Changing the cams and raising compression doesn't make the turbo compress more air, it makes the engine capable of moving more air more efficiently.

Would you rather buy a nitrous kit and pay $6/lbs to refill it whenever you need to or just invest in a properly sized turbo that meets your power goals? There's no need to reinvent the wheel. Popular engine/turbo combinations are popular because they work.
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Old 02-05-2020, 12:59 PM   #9
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Was thinking about running methanol or tolulene injection along with it and by God if I need to I'll put a bottle on it... but really how is that higher compression and cams not going to put it roughly 100 hp above a good stage 2/3 build.
uhh yeah... so out car is pretty turbo dependant. you need to force more air into it to make that. other wise all you are going to do is blow it up. Nos at higher rpms with a turbo is going to be extremely hard to tue as well. most people when they use NOS they are using it to spool the turbo not make power up to. Minimum turbo you will need to have a solid 400hp car is going to be a gen 2 3071 or somthing around that size with a .82ar but you will shift your power band to the right..also that is what the cams will do too BtW.
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Old 02-06-2020, 02:24 PM   #10
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Shift the powerband yes, but what is to say it will make less hp all over?
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Old 02-06-2020, 05:28 PM   #11
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Shift the powerband yes, but what is to say it will make less hp all over?
It wonít make less HP. It will make the same(ish) power with less manifold pressure as the engine is breathing more efficiently(ie lower restriction). That doesnít change the fact that HP and TQ are a pretty basic equation determined by the amount of fuel being burned and you canít burn more fuel without more air and X turbo will only move X amount of air with any reasonable amount of efficiency.

If you want 400whp at all speeds then EV swap it otherwise you have to live with compromise. Nitrous can be used to help spool a larger turbo more quickly to get the best of a turbocharged ICE but it canít make a turbo keep up at high rpm where the engine requires more air than the turbo is capable of moving. You just end up with really hot air as the turbo spins faster in order to keep up; the faster you spin a turbo the hotter the charge air becomes.

Obviously some over simplification here but you get the point.

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Old 02-12-2020, 10:45 AM   #12
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Stop watching Fast and the Furious and do some research. Not to sound like a dick, just trying to help. Most of us have been there and realized how stupid we were as we grew up.

400 WHP is very easy to achieve on a 2.5 without "NOZ" and way cheaper and safer. Our cars are not designed for nitrous at high RPMs, if you want it safe you would have to throw way more money at it to make sure it does not blow up.

If you want 400WHP with decent spool, upgrade your intake system, get a FP green HTZ with a 84mm antisurge housing, delete your TVGs and upgrade exhaust. Well also injectors with a tune from JR, some other supporting mods and your are set.

If you want your exhaust to "pop" so you can get in to someones panties, then just install one of those "backfire flame kits" or just as your tuner to make you run a little rich and install and spark plug in the exhaust. But heads up, the back flow from the popping or the flames will over time damage the turbo and effect spool between shifts. If you want it to sound like you are at 9000 rpms when you really are at 6000 rpms then just install one of these.

https://www.protuninglab.com/exco-3-...yABEgIMDfD_BwE
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Old 02-13-2020, 02:35 PM   #13
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Stop watching Fast and the Furious and do some research. Not to sound like a dick, just trying to help. Most of us have been there and realized how stupid we were as we grew up.

400 WHP is very easy to achieve on a 2.5 without "NOZ" and way cheaper and safer. Our cars are not designed for nitrous at high RPMs, if you want it safe you would have to throw way more money at it to make sure it does not blow up.

If you want 400WHP with decent spool, upgrade your intake system, get a FP green HTZ with a 84mm antisurge housing, delete your TVGs and upgrade exhaust. Well also injectors with a tune from JR, some other supporting mods and your are set.

If you want your exhaust to "pop" so you can get in to someones panties, then just install one of those "backfire flame kits" or just as your tuner to make you run a little rich and install and spark plug in the exhaust. But heads up, the back flow from the popping or the flames will over time damage the turbo and effect spool between shifts. If you want it to sound like you are at 9000 rpms when you really are at 6000 rpms then just install one of these.

https://www.protuninglab.com/exco-3-...yABEgIMDfD_BwE
I think u need laid... but anyways the "NOZ" would be to provide more air when the turbo ****s the bed at higher rpm. Subarus aren't some unicorn time machine rocketships that can't use nos for power. Just to make a point I might put on an ewg and run 0 boost, all NOS, just because I can.
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Old 02-13-2020, 02:36 PM   #14
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It wonít make less HP. It will make the same(ish) power with less manifold pressure as the engine is breathing more efficiently(ie lower restriction). That doesnít change the fact that HP and TQ are a pretty basic equation determined by the amount of fuel being burned and you canít burn more fuel without more air and X turbo will only move X amount of air with any reasonable amount of efficiency.

If you want 400whp at all speeds then EV swap it otherwise you have to live with compromise. Nitrous can be used to help spool a larger turbo more quickly to get the best of a turbocharged ICE but it canít make a turbo keep up at high rpm where the engine requires more air than the turbo is capable of moving. You just end up with really hot air as the turbo spins faster in order to keep up; the faster you spin a turbo the hotter the charge air becomes.

Obviously some over simplification here but you get the point.
I am saying use nos to keep upping manifold pressure as the little guy runs out of steam.
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Old 02-13-2020, 03:34 PM   #15
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I am saying use nos to keep upping manifold pressure as the little guy runs out of steam.
Nitrous doesn't increase manifold pressure.

Do what you want. It's your car and you are going to do whatever you want anyways so why even post questions like this if all you are going to do is argue with people that disagree? I highly doubt any of this ever comes to fruition anyways.
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Old 02-13-2020, 07:15 PM   #16
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I think u need laid... but anyways the "NOZ" would be to provide more air when the turbo ****s the bed at higher rpm. Subarus aren't some unicorn time machine rocketships that can't use nos for power. Just to make a point I might put on an ewg and run 0 boost, all NOS, just because I can.
So this is actually been a relatively helpful/informative grouping of responses to your posts in this thread thus far. You just appear to not agree with the general consensus on this platform.

Nitrous is a simple power adder that when used on a car already making its power via BOOST is used to allow for a larger turbo to still function at lower RPM. I have NEVER seen someone successfully use nitrous on a SMALL turbo car with any real success.

That being said there are several ways to get 400whp out of a 2.5L turbo motor that have been mentioned. I think at this point you need to build it and "shut everyone up" or take a little advise from people whom have cars that meet the basic goals you want. My car makes 425whp on pump 92 (8:1cr with cams), it picks up by 4k and holds till 8500 (highest I have spun it) because I matched the whole system for that goal (track beast that's still a DD).

Ill just sit and wait for this all to come to fruition.
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Old 02-13-2020, 10:50 PM   #17
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I am saying use nos to keep upping manifold pressure as the little guy runs out of steam.
you might want to read up on how nitrous works...lol. Also be sure to employ a "DANGER TO MANIFOLD" sensor.
I think you should run propylene oxide or moth balls.
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Old 02-13-2020, 10:53 PM   #18
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Nitrous doesn't increase manifold pressure.

Do what you want. It's your car and you are going to do whatever you want anyways so why even post questions like this if all you are going to do is argue with people that disagree? I highly doubt any of this ever comes to fruition anyways.
Dont be furious that the OP isnt all that fast..lol. He should plumb a -8 nawz line to his mouf... report findings.
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Old 02-14-2020, 11:00 AM   #19
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You will also need to build a sealed firewall for the trunk if you plan to run SCCA events with a nitrous tank in the trunk. Not positive on all the regulations for nitrous with the SCCA as it isn't very prevalent but if it is categorized anything like a fuel cell you will need a sealed firewall.
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Old 02-16-2020, 11:12 PM   #20
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you might want to read up on how nitrous works...lol. Also be sure to employ a "DANGER TO MANIFOLD" sensor.
I think you should run propylene oxide or moth balls.
That's just for my boy, RIP... I'm sorry officer , I didnt realize we were dealing with the engineering police...
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Old 02-16-2020, 11:16 PM   #21
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Nitrous doesn't increase manifold pressure.

Do what you want. It's your car and you are going to do whatever you want anyways so why even post questions like this if all you are going to do is argue with people that disagree? I highly doubt any of this ever comes to fruition anyways.
How could it not? Under pressure in bottle ----> intake = not more total gas (as in air or n20) in intake tract? If you sealed up the intake and pumped it in would it not increase pressure.... facepalm
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Old 02-16-2020, 11:19 PM   #22
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You will also need to build a sealed firewall for the trunk if you plan to run SCCA events with a nitrous tank in the trunk. Not positive on all the regulations for nitrous with the SCCA as it isn't very prevalent but if it is categorized anything like a fuel cell you will need a sealed firewall.
Good point, what about just put the bottle in a sealed container in the trunk.
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Old 02-16-2020, 11:23 PM   #23
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you might want to read up on how nitrous works...lol. Also be sure to employ a "DANGER TO MANIFOLD" sensor.
I think you should run propylene oxide or moth balls.
I'm now thinking about running the whole build on hydrazine... I feed on trolls for breakfast lunch and dinner
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Old 02-17-2020, 12:17 PM   #24
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How could it not? Under pressure in bottle ----> intake = not more total gas (as in air or n20) in intake tract? If you sealed up the intake and pumped it in would it not increase pressure.... facepalm

That's not how it works, the pressure is regulated. When nitrous is heated to 572*F on the compression stroke the chemical compound of nitrous breaks down and releases oxygen(in the cylinder, not the manifold) which allows you to burn more fuel, ie more power.

Your intake manifold is not a sealed unit... Just because your boost gauge shows a positive manifold pressure that does not indicate that it is sealed, that is indicative of restriction. Boost is a measure of restriction, not airflow. For example, I used to run a Vortech Ti blower on my 99 C5 Corvette drag car and was making 11 psi on a 3.6" pulley and OEM crank pulley. When I swapped out the OEM headers and cats for longtube headers and a catless X-pipe I lost 2 psi but picked up 35whp. I did not change the pulley but I lost boost pressure and gained power, how did that happen? It happened because I reduced the amount of restriction in my motor but the blower itself was still moving the same amount of air.

I'm not trying to troll you, I'm honestly trying to help you understand why your plan is a bit backwards. My C5 is now running a big single and making upwards of 900whp on boost and E85 alone. My other car is a big single 1991 Nissan GTR that, once dyno'd, should be making around 650whp on E85. I'm not trying to flex on you, I've been reading, watching and learning from experience for 16 years now and all I am trying to do is share what I've learned to help save you the trouble of going down a road that won't achieve what you want.

Internal combustion engines require compromise, it's actually very simple science and science can't be beat. If you want a 400whp track beast and you want to build the motor then forge the motor, 8.5:1 compression ratio(maybe 9:1 if you feel lucky) and run E85 or water/meth injection with a turbo that is designed to top out around the 400whp mark. I made 409whp on an FP Blue and 93 octane, 375 on a rotated GTX3076R on 93 and 475 on the GTX30 on E85.

If you know how to drive and keep your car in it's powerband you will never notice the few hundred more RPM's it takes to spool these turbos over the OEM VF turdblow. E85 will help spool times as well.
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Old 02-17-2020, 12:20 PM   #25
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Good point, what about just put the bottle in a sealed container in the trunk.
You'd have to dig into the SCCA handbook and find out because I'm not 100% sure how they regulate compressed air cylinders since it's not a fuel but a compressed gas.
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