Turbo Problem

[cre]

Let's review... you've apparently misread or misunderstood or both.

This:

Originally Posted by dunewarz

Mklll don't come with wastegates.

Equals:

Originally Posted by cre

You are dead wrong.... the CT-26 uses an internal wastegate. The wastegate actuator is the round metal can with the rod coming out that is mounted to the CT-26.

This:

Originally Posted by dunewarz

[a stuck BOV]...will cause a large amount of pressure build up in your pipes.

(Close, but not quite... you'll only see a little more pressure than normal.)

Equals:

Originally Posted by cre

BOVs do not vent from boost; They vent when the actuator sees vacuum. They are not a device for controlling boost levels.

Lets examine this statement further: "They are not a device for controlling boost levels."

Nowhere did I say they do not vent boost... I said they are not triggered or caused to open from boost (a requirement of any device which is supposed to open to release excess boost).

The BOV is used to flat out DUMP the pressurized air within the intake in order to prevent the turbo's inducer and shaft from absorbing a shock and possibly spinning backward due to the repercussive surge which follows the closing of the throttle plate.

When you release the throttle the intake plenum after the throttle plate goes into a state of vacuum, the turbo's impeller is (due to a neato thing called inertia) still spinning and the air is smacking the throttle plate and bouncing backward. To prevent this shockwave from reaching the turbo and thus extending the turbo's life (also to help the turbo spool up faster by preventing the need for the incuder to reverse direction yet again) a blow off valve or a bypass valve (there is a difference and each has its own benefits and downfalls) is employed to dump as much pressure as possible. This valve is opened by using the vacuum pressure when the throttle is closed to pull open the valve.

A wastegate is driven by the pressure level of the intake manifold. There is a spring inside which prevents it from opening below a certain level... this is the reference load. In order for a wastegate to open the signal load must be higher than the reference load. Once the manifold reaches the a point above that level the wastegate slowly opens allowing the exducer to slow but just until the reference level is again higher... it's a balancing act. The wastegate keeps the pressure constant, not the BOV which simply dumps as much as it can.


You can run a car without a BOV or BPV; You can't or at least definitely shouldn't run without a wastegate.

Originally Posted by dunewarz

Actually BOVs do vent boost. Waste gates prevents boost from occurring by venting exhaust gas from the turbo fin.

Yes, right on both counts... which has me wondering how it is you fail to understand what their purposes are.

Originally Posted by dunewarz

You'd have high boost lag if your turbo was running full boost. You'd have high acceleration if your BOV was stuck closed.

Wrong... you've got it backward. If the waste gate is stuck closed you'd overboost; The waste gate is the pressure regulation device. Stuck BOV or BPV = lag and potential damage to the inducer and shaft.

[MA70-3.0GT]

Top quality answer award & +1 for patience goes to..... CRE.... lol

Dunewarz, your rebuttal???

[cre]

Now, now.... that's not called for. It's just a misunderstanding, easily remedied.

[MA70-3.0GT]

Good God, I look back at some of the posts I made the last time I was online & gotta wonder, how bored & cranky can I have been?

First part still applies though I guess.

[916MKIIIx2]

The BOV also helps stop compressor surge ^^, but anyway... I had the same problem once before... turned out to be a 5 dollar problem, check all the hoses coming from your turbo/wastegate might just have a hole ;p

[rob87]

What about the other way around to the original posting. No turbo boosting or very little according to the gauge and hearing a whining pitch sound when you should be getting boost from the turbo?

Would it be a bad turbo unit, wastegate or BOV?

This just started happening to me and not sure what to tackle or look for to confirm what is wrong.


87 turbo manual trans
rob87

[cre]

It would probably be cleaner for you to start a new thread. It's kind of hard to diagnose a "whine" without actually being there. I'd starts with checking the least expensive to replace components first: check IC plumbing for boost leak, check BOV for leak, test wastegate actuator movement with a bicycle tire pump.

Otherwise, yes, it could also be the infamous "whine of death" of the turbo.

[rob87]

thanks for the info, at least I have somewhere to start checking.