Overboost protection? Dont take as being correct, confusing thread.

[S2central.net]

I was going to have a rant, but thank you Jamo for spotting the fundamental flaw introduced into this thread - causing much confusion along the way for some...

Paul

[mojogoes]

Thanks for the 101/correction i'm not familiar with your setups , so what is the spring tension set at in the standard external wastegate!!.......does it keep the wastegate closed until 1 bar or 5psi.

If you were to run much over 16/18psi which is considered to be high boost internal wastegates work out better though.

[martinjs]

If you were to run much over 16/18psi which is considered to be high boost internal wastegates work out better though.

Why?

[S2central.net]

Why indeed - when just about every high boosting turbocharged engine I have every seen runs with an external wastegate. I don't see any gains with an internal wastegate - other than neat packaging - which isn't a consideration in the world of modified motors.


Paul

[newsh]

I thought this was ******... Actually I pretty much knew this was ******, this bloke hasn't written one single post that makes any sense......

[Jon441cc]

Thanks for the 101/correction i'm not familiar with your setups , so what is the spring tension set at in the standard external wastegate!!.......does it keep the wastegate closed until 1 bar or 5psi.

If you were to run much over 16/18psi which is considered to be high boost internal wastegates work out better though.

18 psi in an s2 is NOT high boost! and external wastegates are far superior than internal wastegates in high boost applications.
There is plenty of info on this site about how the s2 controls boost.

[mojogoes]

What's the difference between internal and external wastegates?
Internal wastegates are comprised of a flapper door which is built in the turbine housing, usually operated pneumatically by a mechanical actuator. These flapper doors are limited in size, but work well in certain applications. Usually found in smaller turbos, internal wastegates are relatively inexpensive, simple in design, and very durable. Larger turbo can be fitted with internal wastegates, but boost control can be tricky. If you are looking to run high boost (20+ psi) all the time, then an internal gate may be fine. If you are looking to run lower boost levels, you will need an external wastegate.

External wastegates are generally mounted to the exhaust manifold or to the O2 housing, and are self contained units. External wastegates have the ability to bypass large amounts of air, and can provide steady boost control at any pressure level. A common myth is that in order to run higher boost pressures, you need a larger wastegate. This is incorrect. Larger wastegates are necessary to run low boost levels on large turbos.
"QUOTE"

[ThatGUY]

@mojogoes

Do you own an Audi 5 pot?

[mojogoes]

No!!!

[Corey]

Renault 5GT???

[Greg_S]

External wastegates are generally mounted to the exhaust manifold or to the O2 housing, and are self contained units. External wastegates have the ability to bypass large amounts of air, and can provide steady boost control at any pressure level. A common myth is that in order to run higher boost pressures, you need a larger wastegate. This is incorrect. Larger wastegates are necessary to run low boost levels on large turbos.

I can understand what you are trying to say, but it isnt strictly true. In order to correctly control the boost in high boost applications a large wastegate is required so that the boost can be modulated. For example some of our forum membes run high boost and in order to control boost at the red line to say 1.5bar an external wastegate is required. Whilst full boost may be 2.5bar. Neither of these two figures is low boost.

Also the internal wastegate has the disadvantage of creating more turbulence in the exhaust near the exhuast turbine outlet due to its construction and can represent a restriction. by using an external wastegate it is possible to join the gasses back into the main flow further down the exhaust where they will not affect the exhuast turbine

[alg]

Having read this thread I have to say that anyone searching the forum re 'overboost protection' is going to end up very confused due to the 'stateside rubbish'. A very good reason for the mods to lock and/or delete it.
WRT the original post it does sound like a small boost leak rather than WGFV. I had a loose wire connection which gave an intermittent drop to mechanical boost limits. Caused some head scratching @ MRC.
Old story really, check fault codes, pressure test and also you can test the WGFV with vagcom.

[Greg_S]

I have closed this thread now