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Discussion Starter #1
Well I just did a swap with my NA. A JDM TT Auto w/ an NA SP Built Tranny. Everything runs great except when I'm at WOT. The Boost is the problem. It quickly shoots up to 10psi and then suddenly backs off to about 7 psi. If I slowly roll on the throttle to a certain point it holds at 10 psi and feels great. But if I get on it anymore it backs off. What could this be? Thanks.

Mods I have: Intake, 3" DP, and 3" Catback Super Dragger.

Any ideas would be appreciated. My guesses are that I need a boost cut controller and a boost controller. But what do I know?....
 
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fuel cut?

mine will hit 16-17 for awhile then descide its boosting to much then fuel cut hits.... boost drops to 13-14 and its fine.

I'd say its time for a FCD of some sort and a MBC or EBC
 

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Discussion Starter #4
ToMuchBoost said:
what ecu are you using the JDM one or a US spec one?
It's all JDM.
 

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so what ur sayin is you cant boost past 10psi at all?...if so i might have had the same problem. do you have a boost controller?
sorry if this is off subject...did everything work out with sherbaz ? i ordered my motor from him (jdm tt 6spd) and so far the things been great.
 

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Hi own the same car and 7psi is stock.

BCC wont add anything here, maybe check all teh hoses for the VPC and get a BC.

Try the t method to see, maybe a boost leek?
 

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Discussion Starter #7 (Edited)
95240sx-2jzgte said:
so what ur sayin is you cant boost past 10psi at all?...if so i might have had the same problem. do you have a boost controller?
sorry if this is off subject...did everything work out with sherbaz ? i ordered my motor from him (jdm tt 6spd) and so far the things been great.
Well yeah I can't boost past 10 psi, cause I think thats stock level. But what I'm thinking now after driving it a bit, it may be a boost leak or the ECUs cutting back the Boost cause at Higer RPM's it cuts back to about 7. I think with the 3" DP and 3" exhaust it may be boosting too quickly for the ECU? I don't know though that's just a guess. But even at 7 psi, it still pulls like a mad man. Well compared to my old NA engine that is....
 

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Discussion Starter #8
Jay-450 said:
Hi own the same car and 7psi is stock.

BCC wont add anything here, maybe check all teh hoses for the VPC and get a BC.

Try the t method to see, maybe a boost leek?
So 7 PSI is Stock for the JDM??? So when I'm seeing 10 I'm actually over boosting. Well at least it won't go any higher. But if that's true than I'm all good. But I wonder why it surges to 10psi and then backs down to 7???

Anyone else know about this?
 

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Ok,

7psi is factory, but with the dragger you have you should see around 10psi as thats where the restriction is.


But seriously, just check all your VPC hoses and Get youself a manual boost controller for now if you cant afford the $$$.

Dont forget a BCC or your drive train will suffer!!!!
 

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Discussion Starter #10
Jay-450 said:
Ok,

7psi is factory, but with the dragger you have you should see around 10psi as thats where the restriction is.


But seriously, just check all your VPC hoses and Get youself a manual boost controller for now if you cant afford the $$$.

Dont forget a BCC or your drive train will suffer!!!!
Why will my drive train suffer?

So right now at 10 psi initially is what I should be seeing, right? And so I may have a boost leak? That sounds about right. I'll check all the hoses. But I will be getting a Manual Boost controller soon.
 

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Jay-450 said:
Hi own the same car and 7psi is stock.

BCC wont add anything here, maybe check all teh hoses for the VPC and get a BC.

Try the t method to see, maybe a boost leek?
There is no VPC on this car it's a JDM TT

Your TT only runs at 7psi, get it looked at if that's on the second turbo.
 

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begone said:
Why will my drive train suffer?

So right now at 10 psi initially is what I should be seeing, right? And so I may have a boost leak? That sounds about right. I'll check all the hoses. But I will be getting a Manual Boost controller soon.
It won't suffer


Are you sure the second turbo is coming online? A JDM TT with downpipe and exhaust should overboost dangerously
 

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Discussion Starter #13
Bullseye said:
It won't suffer


Are you sure the second turbo is coming online? A JDM TT with downpipe and exhaust should overboost dangerously
If it isn't, that First turbo is putting down a ton of power. I also drive an M3 and as far as seat of your pants, these cars are comparable. The M3's putting down around 280 rwhp, and this supra feels pretty close to that.
 

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Then I'm going to say it's a boost leak somewhere.

Remember a decatted/dragger JDM Supra will mostly likely overboost to destruction unless you add a restriction back into the system (not a boost controller).
 

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Discussion Starter #15
Bullseye said:
Then I'm going to say it's a boost leak somewhere.

Remember a decatted/dragger JDM Supra will mostly likely overboost to destruction unless you add a restriction back into the system (not a boost controller).
So I should actually keep it like it is now so I don't blow up my Turbos huh? But once I find this leak, what should I do to keep from Overboosting?

Like I said it shoots up to 10psi and then once the RPM's build it backs down to 7 psi. 7psi is plenty right now, especially since these Turbos are prone to blow.
 

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Did you extend the harness?
As some time the ecu has to learn the boost curve agian,or something like that,Drive it for 1 week and see whats happens,if it stays the same get a boost cut and see what happens.
 

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begone said:
So I should actually keep it like it is now so I don't blow up my Turbos huh? But once I find this leak, what should I do to keep from Overboosting?

Like I said it shoots up to 10psi and then once the RPM's build it backs down to 7 psi. 7psi is plenty right now, especially since these Turbos are prone to blow.
You can either:

1. Put back in a cat, second one is best

2. Make and fit a restrictor plate between the dp and exhaust. Just open out the hole in the restrictor until you get say 1 bar of boost and control it with a MBC or EBC
 
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