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Discussion Starter · #1 ·
I recently discovered a large tear in my iPd OTE pipe, right at the base of the neck for their diverter valve. The tear goes almost halfway round, very likely my power loss culprit! Talked to iPd about it and sent them pictures of my finger inside the tear, and they've never seen anything like it. Don't bash iPd though, something almost certainly cut it, there's no way it just blew open, and there appears to be a corresponding mark on the heat liner in the engine bay. PO was a fool...
Anyway I'm probably replacing the OTE pipe with another one from iPd, along with some other stuff while I'm in there. My question is, barring the price difference, is there any benefit to iPd's external diverter valve over the conventional compressor bypass valves like Forge's unit? Most times this question comes up it devolves into the price battle without ever answering the question, and I'm curious to know the actual benefit. Plus their silicone hoses look a bit goofy if you've got two completely unused necks sticking off of them...
 

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All bypass valves do the same thing so their location is pretty inconsequential, so I recommend keeping it simple and going back to the scroll bypass if you still have a turbo that will accept one.

Then again if you want to be all showy with it and hear it more, an external unit will give you that.
 

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Best solution would be to route it to recirculate after the intercooler. This way it recirculates already cooled air instead of hot coming straight from the compressor.
 

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That hot air returns to about the ambient temp as it expands back to ambient pressure. There is a small increase in temp during the round trip due to compressor inefficiencies, but considering it only kicks when you close the throttle its a moot point.
 

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What it really comes down to is that having a real external bypass valve with it setup how IPD does it, will let you adjust or replace the Bypass valve in minutes, not hours or days like it would take having the BPV on the compressor housing like the stock K24 does.

Pretty much all of good bypass valves on the market allow for adjustment. Some you switch springs, some you add washers to, and some have an adjustable nut on top. This allows you to adjust the preload on the unit and when it opens.

You have to decide if you want to spend hours sitting spread eagle over the R motor trying to reach down to get to the stock location on the compressor housing, or 5 minutes with it up on top with an external valve. Also, God forbid you have a boost leak from the valve and have to try to fix it.
 

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There is also the GFB DV+ T9301 (100% re-circulation)if you're looking for something more affordable than the IPD unit.

http://www.do88.se/en/artiklar/gfb-dv-tms-diverter-valve.html

A couple benefits I can think of:

- Fine adjustment for spring tension, no need to change springs for higher boost.
- Eliminates the need to ever service the stock CBV which is a bear.
- All metal parts, no need to worry about a ruptured diagram.
- No increase in sound (unless you are running an open air filter)

Here's my setup with an open air filter with the GFB DV+
 

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Discussion Starter · #7 ·
Service and adjustment is a good point. I'd always thought it had something to do with turbo life, iPd kind of rails on the CBV design a little bit but never specifically addressed anything.
I'd never seen that GBV TV+ from do88, that's pretty cool. Closer to Forge's price than iPd too, and the same size. Might have to consider that one.
So does iPd's diverter not have an option for 100% recirculation? I thought you had the option to either remove that plate for a nice whoosh, or run it fully closed.
 

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There are really two different functions or aspects of the CBP (or diverter).

One is to prevent turbo damage from the shaft deflecting too far under boost surges. This only happens in the most extreme situations and is even less likely (almost impossible) with a roller bearing turbo like the 4T4. It is certainly possible, but not very advisable, to run a car without any kind of bypass. Keep in mind that damage to your charge air system is far more likely than damage to the turbo. Yes, we have popped intercoolers before.

The other is to prevent the boost surge waves from interfering with a smooth and predictable boost delivery. This is where the factory K24 CBV fails. Optimally, you need an adjustable unit to allow you to custom tailor the behavior of your bypass to achieve zero bypass when closed and smooth transition from closed to open and back again. Thus achieving the most predictable power that the ECU doesn't need to correct for.

A chattering bypass or blow-off is not good. This represents multiple pressure waves through your charge air system.

Our CBV is very good. There are certainly other very good units on the market, but most are "less than they could be". CBV and blow-off leakage is one of the most common problems that tuners face in their daily work. Buy one elsewhere if you need to, but don't cheap out on this. It is VERY DIFFICULT to chase down this power robbing failure later if it is a full bypass unit.

Accidental Learning Opportunity
Obviously this kind of mechanical set-up is becoming old school ghetto. The current Volvo lines feature KKK turbos with electronically controlled bypasses.
 

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