Blow Off Valve to cure overboost?

[LotusEnthusiast]

Hey Everyone. Need some advice/knowledge. I've searched and I know porting the wastegate to 21mm is the way to go to solve overboost but what about a BOV?

I've been talking to my dad about porting my wastegate sometime over summer to solve my overboost problem I've been having. It doesn't happen all the time but it needs to be fixed.

He suggested that I should just put a BOV instead because my bolts and nuts are all rusted up and if something breaks we have more problems and that's not good. However I asked him do you think that would cure it? He said he's not sure but its a whole a lot cheaper and safer than having someone take your turbo off and porting the wastegate. We came to the conclusion to ask you guys and see if you guys could help.

Any feed back would be much appreciated,
Thanks Chris

[Rusty Wishbone]

I think that a BOV is fitted on the induction side of the engine, and porting is done on the exhaust side. If I am right, a BOV won't help. However, I'll let others who are more expert give the answer so that you don't have to rely on my speculation.

[rip]

The OP is proposing to bleed off excess pressure after the turbo has already generated it.

I don't think a dump valve could be controlled accurately enough to do the job. It is designed to be open or closed, not continuously bleed off a controlled amount of excess pressure.

A BOV is slightly different. It works by detecting a pressure difference across the throttle valve plate, so would not be suitable for this task.

[LotusEnthusiast]

Alright thanks guys.

[lotusgirlmarie]

A direct answer. No, a BOV or a dump valve will not solve your problems and in some cases make it worse. Porting the easy gate is always the best way. Just get extra studs and nuts for the manifolds and turbo. Should one go, you have options.

[GeoffSmith]

Releasing the pressure after the turbo will take load off and it could spin too fast and cause damage, particularly if it is slightly out of balance due to e.g. foreign body ingestion - Force is proportional to rotational velocity squared so 20% overspeed increases the forces by nearly 50%. It must be tackled on the exhaust side and if you're looking for a temporary solution you could put a restriction (baffle plate) in one of the exhaust joints.

[Enright]

Short answer - Marie's right.
Bit longer answer: have a look here:
viewtopic.php?f=31&t=17991
It's a while since I wrote it and it may not directly answer your question, but it's a fairly decent analogy.

[LotusEnthusiast]

Thanks for the great info everyone. Looks like the wastegate will be getting ported this summer.

Thanks Chris

[superbad]

Turbocharged Indycars used to have a popoff valve to control boost at the manifold (to keep you from exceeding the maximum boost allowed by the rules). You would always go to great lengths to avoid triggering it- it's just a spring operated valve, and when it opened it would abruptly dump most of the boost. If you used an electronically controlled valve that could more closely maintain the pressure it might work better, but porting the wastegate would be easier, simpler, and you'd be treating the actual problem rather than its symptom.

[lotos]

Forgive my ignorance, but how do you detect/diagnose overboost?

[rip]

Forgive my ignorance, but how do you detect/diagnose overboost?

When you're on maximum throttle at high revs, you will feela brief hesitation before the ecu cuts engine power suddenly. It feels like someone slamming the brakes on. It is not subtle at all.
The CEL then stays on for 40 seconds limiting revs to 4000. You can paperclip it or run Elanscan to find the fault code.

[lotos]

Okay thanks, yeah that doesn't sound subtle at all!

[GeoffSmith]

Forgive my ignorance, but how do you detect/diagnose overboost?

Look in the mirror and if there is a groove in your forehead the same shape as your steering wheel....

[HJ2]

This analogy goes only for those without uprated front brakes ....