bov before mbc?

Q&A regarding engines, turbos, and intercoolers and power upgrades

bov before mbc?

Postby Aaron » Thu Oct 07, 2004 9:38 pm

Is it necessary to get a bov before upping the boost to ~14psi?
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Postby zblu81 » Thu Oct 07, 2004 10:25 pm

upping the boost will put more stress on the turbo during a high boost gear shift. A bov will help protect the turbo during those shifts. Necessary is a matter of opinion. There's really no reason not to do it before. If you're trying to save money remember that replacing/rebuilding a turbo is not cheap.
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Postby goldfish » Thu Oct 07, 2004 11:24 pm

I have one and i have an upgraded CT26 and FMIC - i dont really think it is necessary until you have something other than a stock turbo or have removed stock fuel cut.
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Postby Doge » Fri Oct 08, 2004 2:36 am

dont kid yourself... not having a blow off valve just puts more stress on your turbo... ALOT more. Even with at stock boost when you shift thats 10-12 psi shooting straight back on your turbo blades... NOT GOOD. It is a mystery why the alltrac didnt come with one... the mr2's did.
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Postby goldfish » Fri Oct 08, 2004 1:10 pm

i completely understand and agree that it is better to have a BOV - but i know people running increased boost on a factory turbo that has never been removed with over 140K miles on it...and it has been holding up just fine since the day it came off the lot... Heck, on stock boost 140k miles is impressive...

Can anyone prove that their stock turbo has gone out, or their seals started to leak due to not having a BOV and not pushing past fuel cut?
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Postby SuperWhite92 » Fri Oct 08, 2004 9:52 pm

think about the stress on the turbo when you stop a blade from 25,000rpm in its tracks. Ouch.
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Postby goldfish » Fri Oct 08, 2004 10:20 pm

Again - i know what a BOV is for - and i KNOW it is a good thing, which is why i have one. But - people who have been running 12ish psi on a stock turbo for 120k++ miles dont have problems. I realize that it is some stress on the turbo, but if it were detrimental at those boost levels, then why wouldn't the turbo give out so much sooner. And by the way it is 100,000+ Rpms. ;-) If not having a BOV was SO detrimemnal to the turbo - peoples turbos wouldn't last so long. Come on, we are talking about turbos that are 12-16 years old with tons of miles that still boost fine...

My own car was boosting about 13 psi from 55K miles until about 135k miles when the turbo seals finally decided to go out. I wont buy into the argument that it was the fact that i didn't have a BOV at the time is the reason that the seals went. There is TOO much internet myth.

Things I know:
1 - A BOV is good for your turbo

Things that haven't been proven:
1 - You NEED a BOV on a stock turbo under 14psi

If someone is able to prove yes/no that a stock turbo running under boost cut needs a BOV, then i will agree either way. I just wont take one post on alltrac.net as the end-all resolution of an issue when it is only backed by theory (even though the theory is logical)

Here's a question - do MR2 Turbos last longer than Alltrac turbos since MR2s have BOVs? I'd be curious to know that...
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Postby busdriver » Sat Oct 09, 2004 5:51 am

Anything that receives more stress/force is going to be more likely to fail, I think the question is would the added stress cause failure before an unrelated failure occurs? It is entirely possible for your turbo to last quite a while w/out a BOV at higher than stock boost levels, it is also possible that the added stress causes failure very soon. I would go the safe route and install the BOV first, reguardless of the lack of proven failures.
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Re: bov before mbc?

Postby illGT4 » Sat Oct 09, 2004 5:56 am

Aaron wrote:Is it necessary to get a bov before upping the boost to ~14psi?


It's not necessary, but it's nice to have. Won't hurt at all. Unless you vent it to atmosphere (like most) and run even more rich. :)

Anyhow.. I'd get one, it's part of the "base mods" that you should have before you start asking for more power..

get a full exhaust with dp
a nice air filter in a cooler spot of the enigne bay
a fan on the stock intercooler
a bov

and most important.. make sure the car is tuned up. Repalce all the ignition components before you increase boost.. Buy a new fuel filter if you don't know when the last time it was changed..

I've made a lot of choices both good and bad with my car. ..just ideas for you..
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