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Hello everyone

 

im wanting to know why my turbo is so damn laggy. i have a feeling it could be the boost solenoid. i have a v7 sti motor in my B4 legacy and it runs mint apart from this annoying lag, turbo spools to 7 psi and sits there until about 5k rpm then it finally hits full boost at 14.5psi. everything is factory v7 sti (engine, loom ecu) so its not like a aftermarket ecu without a tune or something. 

 

im wanting to know if i should disconnect the boost solenoid and run wastegate pressure. 

 

Cheers

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Are you sure everything is wired and plumbed up correctly? Have you also confirmed in the ECU ROM what it is actually aiming to make? Seems like a super weird situation.

 

Running wastegate pressure will just hold around 7psi the whole way so won't tell you much. Probably worth disconnecting the solenoid and putting a boost tap in instead to see if it makes boost fine that way to start with.

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ive been thinking of adding a boost tap in. or should i just go external wastegate with a 15psi spring in it and run wastegate pressure so ill just consistantly get 15 psi

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I'd try the tap first using all new vac lines. That'll confirm it is something to do with the solenoid/electrical side rather than mechanical.

 

Is the solenoid a factory one or a 3-port? Do you still have all the restrictor pills in place?

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Fitting an external wastegate to diagnose a boost problem in an oem setup is bats*** crazy.

 

Put a clamp on the boost control line to see if it boosts... go from there.

 

 

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These cars have halfway intelligent boost systems. If it's not making boost, either it's because something is faulty, incorrectly installed, or the ECU is literally telling it not to build boost.

 

Forcing it to make boost, with a tap or an external, is a good way to blow up a motor.

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17 minutes ago, boon said:

These cars have halfway intelligent boost systems. If it's not making boost, either it's because something is faulty, incorrectly installed, or the ECU is literally telling it not to build boost.

 

Forcing it to make boost, with a tap or an external, is a good way to blow up a motor.

 

lol. It will explode and leave a massive crater.

 

One second of boost won't hurt it.

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For diagnosis pull the waste gate hose off, clamp it. Go for a drive and floor it, keep an eye on the boost gauge, note what rpm it hits 14psi and let off the gas.

 

If it's still "laggy" and at 5k then it's likely a mechanical fault (turbo, exhaust leak, boost leak etc.). No form of boost control will fix those issues.

 

If it comes on boost earlier then fault is likely within the boost control system or ecu. If it's this, fix the fault rather than patch it by adding boost control.

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On 19/08/2020 at 6:00 PM, Loren said:

 

lol. It will explode and leave a massive crater.

 

One second of boost won't hurt it.

 

More a reference to all the awesome people whose car is clearly in limp mode and they just wham a boost tap in it long-term and the car is there going "wtf I'm in limp mode because some s*** is badly wrong".

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8 minutes ago, boon said:

 

More a reference to all the awesome people whose car is clearly in limp mode and they just wham a boost tap in it long-term and the car is there going "wtf I'm in limp mode because some s*** is badly wrong".

 

If people are too stupid to be able to distinguish between short term diagnosis instructions, and permanent band aids... then they should blow their s*** cars up and take the bus :)

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so i done some looking around under the bonnet and found a bunch of s*** not right.... so i didnt do the engine swap and after some research and looking under the bonnet i found that block and internals are v7 sti (ej207) BUT from my understanding the intake manifold and the heads are still the legacy (ej208) heads and intake mani. the turbo is also a td05 16g so what ive found is the guy i bought it off was bulls***ting the whole time saying it was a "full v7 sti swap" so im f***ed of what to do, do i get a link ecu and get a tune OR do i "complete" the swap and make it v7 sti everything like it should be. Cheers

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21 hours ago, pl0x said:

For diagnosis pull the waste gate hose off, clamp it. Go for a drive and floor it, keep an eye on the boost gauge, note what rpm it hits 14psi and let off the gas.

 

If it's still "laggy" and at 5k then it's likely a mechanical fault (turbo, exhaust leak, boost leak etc.). No form of boost control will fix those issues.

 

If it comes on boost earlier then fault is likely within the boost control system or ecu. If it's this, fix the fault rather than patch it by adding boost control.

by wastegate hose do you mean the vacuum line connected to the actuator or the turbo? Cheers

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How does the boost control set up look? Wonder if half of the weird ass Legacy TT bits are still in there messing things up

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19 minutes ago, Andy_Mac said:

How does the boost control set up look? Wonder if half of the weird ass Legacy TT bits are still in there messing things up

could that be making it so its boosting in 2 stages like the factory TT does? 

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26 minutes ago, subaru99b4 said:

could that be making it so its boosting in 2 stages like the factory TT does? 

 

You know at this point I'm not going to exclude them having done something deeply stupid like using the factory black box of doom for boost control.

 

I bet two internet cents it's an EJ208 in the middle too.

 

What's the ECU? If it's running all the EJ208 heads and manifold then it's probably running that sensor setup with that ECU.

 

To be honest it sounds like the "V7 STI" swap was actually a really average single turbo conversion.

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1 minute ago, boon said:

 

You know at this point I'm not going to exclude them having done something deeply stupid like using the factory black box of doom for boost control.

 

I bet two internet cents it's an EJ208 in the middle too.

 

What's the ECU? If it's running all the EJ208 heads and manifold then it's probably running that sensor setup with that ECU.

 

To be honest it sounds like the "V7 STI" swap was actually a really average single turbo conversion.

believe it or not it is definitely a ej207 block and internals, thats the one thing the guy provided photo proof and receipts for and as far as i know its a v6 STI ecu so its all over the bloody place 

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Ok so ive found the issue, the restrictor pill was in the wrong place, found a diagram of how it should be and now its way more responsive, goes straight to full boost at 3.7k rpm instead of 6k rpm! way happier with it now! also found my ecu is a j2 which from what ive found out is from a V6 WRX STI RA Limited. Cheers for all of the info everyone gave me! 

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