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Turbo LQ4 questions

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Old Jun 21, 2021 | 09:14 PM
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Default Turbo LQ4 questions

I’m going for a turbo LQ4 build, and I’m wondering what forged components (if any) I need? My current parts so far are:

98mm turbo
317 heads
sloppy stage 2 camshaft
pac1218 springs
new bearings all around
stock bore (honed)

Im just wondering if forged pistons are worth it or if the stock pistons can handle boost. I’m wanting to make around 550-600whp.
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Old Jun 21, 2021 | 09:35 PM
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You'll be alright.
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Old Jun 21, 2021 | 09:43 PM
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That's a huge turbo for the goal, if you haven't bought it yet i might re think that
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Old Jun 21, 2021 | 09:46 PM
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Originally Posted by GMCGreg
That's a huge turbo for the goal, if you haven't bought it yet i might re think that
I wish I would’ve got a 76mm but I already had a 98. It is definitely overkill though.
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Old Jun 21, 2021 | 10:02 PM
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Originally Posted by GMCGreg
That's a huge turbo for the goal, if you haven't bought it yet i might re think that
I'm glad I wasn't the only one thinking that lmao
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Old Jun 21, 2021 | 10:06 PM
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Originally Posted by shakenfake
I'm glad I wasn't the only one thinking that lmao
I mean, I wouldn’t mind more hp but I don’t want to explode
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Old Jun 21, 2021 | 11:12 PM
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I'm going to take a wild guess and say that your 98mm turbo is an Ebay GT45.
They market them as 98mm to people who don't know any better.

They're technically a 68mm turbo measured at the inducer, which is where turbos are normally measured.
An 80mm Borg Warner S480 is ~110mm measured at the exducer.
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Old Jun 21, 2021 | 11:17 PM
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Originally Posted by AwesomeAuto
I'm going to take a wild guess and say that your 98mm turbo is an Ebay GT45.
They market them as 98mm to people who don't know any better.

They're technically a 68mm turbo measured at the inducer, which is where turbos are normally measured.
An 80mm Borg Warner S480 is ~110mm measured at the exducer.
I actually didn’t know that, this is my first engine build so I’m very new to all of this. It is a GT45 though. Think I stick with it then or what would you recommend instead (turbo wise)?
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Old Jun 22, 2021 | 08:32 AM
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Stick with it
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Old Jun 22, 2021 | 12:41 PM
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Sell that GT45 and pick up that cast S480 that's for sale on the forum here.
Much better choice provided you have the room.
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Old Jun 22, 2021 | 01:16 PM
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Why? That is more than enough. I would stick with what you have. If you want to upgrade later then upgrade later.
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Old Jun 22, 2021 | 02:30 PM
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Originally Posted by shakenfake
Why? That is more than enough. I would stick with what you have. If you want to upgrade later then upgrade later.
GT45 starts to choke at 550whp on a 6.0. He's going to be doing things to find extra power to hit his goal.
Its also a hard turbo to upgrade from because the abnormal V-band diameter on the turbine requires you to fab an entire new downpipe, or at least resize/reflange the current one.
Its a turbo you use because you got it for free or because you're trying to do a $500-all-in budget turbo setup.

Even a $450 cast S475 from VS would be a significant step up.
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Old Jun 22, 2021 | 02:38 PM
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He says he wants to make 550-600. If the turbo starts to choke at 550 then great! It hasn't completely choked and he will be fine and have made his goal. I would still say he should run it and later if he wants to do something else then do it later. Getting a new down pipe made is one of those things that really is not the worst thing in the world lol

Better to run what you have and then upgrade later, this way you are able to find out if you are happy with it or if you want/need more power
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Old Jun 22, 2021 | 02:41 PM
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Originally Posted by flycole
I actually didn’t know that, this is my first engine build so I’m very new to all of this. It is a GT45 though. Think I stick with it then or what would you recommend instead (turbo wise)?
Here's the score.
My first turbo build was like you, only looking 550-600whp, started with an itty bitty TC7868 which was fun but choked at 5,500rpm around 6-7 lbs.
So in went an old school T7875 at the same 6-7 lbs. and an extra fuel pump, that lasted about one summer then got boring.
So I upped the boost to 12-13 lbs., now we're having fun, threw it on a stingy Mustang dyno and laid down almost 700whp, drove it like that for years before selling the car.
Point being, 550-600whp might not satisfy you very long, where do you think you'll end up, plan ahead, plan for a T6 flange perhaps, then your options are many and affordable.
Space requirements for the S-series turbos are the only limiting factor, my S484 is pretty big but **** an A does it look cool under the hood.
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Old Jun 24, 2021 | 10:43 PM
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Originally Posted by The ******
Sell that GT45 and pick up that cast S480 that's for sale on the forum here.
Much better choice provided you have the room.
I might do that. I wanna have some options as far as boost goes and don’t wanna be choking at 500 whp
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