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Acceleration
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Discussion Starter #1 (Edited)
Well, I'm going 1jz and I have a few questions. I already have a 3" catless exhaust (Slimfastsupra's old exhaust), intake filter/piping, and I was planning on just adding on a DP while the engine is out. Well I've got a friend with the aussie y pipe that's made for a soarer, so a midpipe needs to be fabricated for it since the dp doesn't line up, and he has offered it to me.

My main questions were that I was under the impression that with intake dp and exhaust, I would be at 14 psi, and that fuel cut is at 1 bar (14.7 psi right? im new to turbos :) ). Now with this y pipe and a fabricated mid pipe bolted up to my exhaust, what psi will I be running, and will I be hitting fuel cut? I don't want to be hitting fuel cut because I know that will be frustrating the hell out of me, but are there easy ways of getting around it? Excuse the dumb question but does higher octane help? Or is it simply a trigger in the ecu that shuts off fuel when boost reaches 14.7 psi?

I really do want to have a full exhaust with no restrictions, and I want it all done when the engine is out so I don't have to go back later and struggle with it. The only other mod for now that I was planning to do was a fmic, a nicely sized one (Not too big, not too small) that fills my lower grill. Does all of this sound good? I've read through the faq's as best I could but go figure, a lot of it I couldn't understand. Is this y pipe going to have the same problems as the ebay y pipe where the fitament is going to be extremely poor? If so, is it still worth it?

Hope this doesn't sound like too much of a newbie post, just trying to learn with an open mind and I'm hoping you guys can help me out.

TIA :)



And btw, :lol: at this smiley.. :madjerk:
 

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I dont know too much about my 1j yet because I havent driven it ne where but up and down my road (not registered ATM)...But it does boost 15+ with the china Y pipe, no cat, AVCR (untuned), and a Tanabe exhaust withought hitting FC.
 

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Supras are never 'done'
1989 Toyota Supra
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601 Posts
Glad to see you're going 1J :) I'd love to hear about your project and I'm sure the rest of the forum would too.

AGlobalThreat said:
Or is it simply a trigger in the ecu that shuts off fuel when boost reaches 14.7 psi?
Bingo. It's referred to as 'fuel cut' but reall it's 'spark cut'. It would be bad to actually cut fuel since you'd run lean.

I have the china Y-pipe and downpipe, 3" cat-back and 3" test pipe, and I haven't hit fuel cut. I don't know what I'm boosting since I just finished the swap and I haven't installed my AVC-R yet (wanted to make sure everything ran ok to start with, ya know?), but I'm -guessing- it's around 14psi. We'll see, the next time I work on the car I think it's time for the AVC-R, S-AFC, 440's and 2JZ map :)
 

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Acceleration
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Discussion Starter #4
Wow this is great, ok. What's the difference from the China y pipe and the Aussie y pipe? These won't have the horrible fitament issues like the ebay ones correct?
 

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Yeah isnt the AU Y pipe 2" instead of the 2.5" on the China? Either way if the engine is out and you have a dremel or a grinder its not big deal.
 

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Supras are never 'done'
1989 Toyota Supra
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601 Posts
I don't think anyone here has any experience with the Aussie ones. My Y-pipe fit OK, but I had to modify the downpipe because it sat like an INCH AND A HALF too high. I cut it and put in a flex section and it fits ok now. It sounds similair to what you'll have to do - so I can't help but wonder if the China ones are supposed to be for Soarers as well.
 

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I had intake, FMIC, 3" downpipe, 3" mp, 3" cb and was boosting 11psi~ but I have a Mark II TourerV.
 

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Acceleration
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Discussion Starter #8
92SupraMan said:
Yeah isnt the AU Y pipe 2" instead of the 2.5" on the China? Either way if the engine is out and you have a dremel or a grinder its not big deal.
I'm assuming you mean the inside diameter of the piping? Would I be better off buying a China Y pipe for more power then? Or is it such little difference it shouldn't even be debating it?

Btw thanks for all the quick help you guys, really appreciate this.
 

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Akai Suisei - 赤い彗星
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On our 1Js fuel cut will always be the same regardless if you're using stock twins or a GT42. It's not like the 7M where it's 13psi give or take depending on other sensors and stuff. It's at 1Bar and unless you do something to change that, it will be there
 

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Acceleration
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Discussion Starter #11
K this sounds good, so I should go ahead and get this then correct? And I won't need a normal DP because I'll be having a connecting pipe fabricated. Any estimated hp/tq gains from a y pipe? Just looking for something general, not used to turbo upgrades, 5, 10, 15, 20 hp? I'm clueless but trying to learn quickly.
 

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1JZ BLING!
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Welcome to the darkside, what took you so long ?

Did you smog before you pulled the motor?

You have my old MR carbon straight back?
 

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going broke fast
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the aussie y-pipe is a smaller diameter but the wastegate's dump into a seperate pipe.its like the dp bic made for the ct26,except for two turbo's.i'm not really sure if anybody has tried this y-pipe on a supra.so you could run into fittment issues.the aussie dp i do believe is mild steel and not s.s. like the china y-pipe.the china one is alot cheaper,but i haven't seen them on e-bay in a while.
 

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Acceleration
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Discussion Starter #15
SlimFastSupra said:
Welcome to the darkside, what took you so long ?

Did you smog before you pulled the motor?

You have my old MR carbon straight back?
Fucking GE took forever to blow :rolleyes:

Yes smog is fine

Yup I got the exhaust after Carson, I love it. Tucks so perfectly.

Haven't addressed speed cut really, that's what killed my old engine, so I'm not looking to go hauling ass down the freeway again any time soon. I'll address speed cut when the time comes, I still have about a month.

I was unaware that the aussie Y pipe also had wastegate dumps, does this mean I could have a ddp for the 1jz? The main reason I wanted a 7mgte in the first place was for the bic ddp. I know most people don't like it, but I just love how scary loud and surprising it is once the wastegates open. If I could get this on the 1jz that would be awesome. :)

Btw this section is so nice, friendly, and helpful. This is like my first day, I got everything OK'ed this morning for the swap. I love you guys :hug:
 

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.the :dunno: -pipe should fit if you use Bic's motor mounts.Trust me, after its in with the engine, youll wonder what the big fitting issue is all about. :)
 

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who makes these twin dumps? There are quite a few people making y pipes and proper twin dumps for 1jz's mostly jzz30 soarers over here.
 
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