Safe tune boost levels

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Safe tune boost levels

Postby Newbie GT » Mon Jul 22, 2013 5:19 pm

Hey gents this question is coming up so I thought I'd post new topic..

So as topic says what is safe S# boost levels without engine failure is 18 psi to much ?
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Re: Safe tune boost levels

Postby Deep Heat » Mon Jul 22, 2013 5:21 pm

Depends on a million other factors.
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Re: Safe tune boost levels

Postby bigBADbenny » Mon Jul 22, 2013 7:36 pm

18psi is the best efficiency for a VF46.
More than that and the charge is over heated or the pressure too great for the stock headstuds which lift at 22psi (if hitting that regularly).
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Re: Safe tune boost levels

Postby Boogs » Mon Jul 22, 2013 7:39 pm

40psi sounds good.

Just keep upping it til its not safe anymore.
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Re: Safe tune boost levels

Postby peadya100 » Mon Jul 22, 2013 7:56 pm

Interesting... what psi do they usually tune the vf52 to?
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Re: Safe tune boost levels

Postby bigBADbenny » Mon Jul 22, 2013 8:33 pm

afaik similar, the VF52 will drop off a little less due to the slightly larger compressor, afaik :)
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Re: Safe tune boost levels

Postby coyote » Mon Jul 22, 2013 8:53 pm

You just keep increasing boost until the engine blows, then back it off a bit.


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Re: Safe tune boost levels

Postby chubbs » Mon Jul 22, 2013 8:57 pm

coyote wrote:You just keep increasing boost until the engine blows, then back it off a bit.


:lol: :lol: :lol: :lol: :lol: :lol: :lol:
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Re: Safe tune boost levels

Postby Newbie GT » Mon Jul 22, 2013 9:07 pm

bigBADbenny wrote:afaik similar, the VF52 will drop off a little less due to the slightly larger compressor, afaik :)


Sorry Benny but can a tuner set to say 18psi and have it not over boost more than that ?
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Re: Safe tune boost levels

Postby peadya100 » Mon Jul 22, 2013 9:26 pm

coyote wrote:You just keep increasing boost until the engine blows, then back it off a bit.


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Makes sense :wink:

I guess ill find out in a couple weeks. MSR doesnt actually ask me what boost pressure I want, he just does it. Hes tuned so many subarus I guess he knows what works best.
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Re: Safe tune boost levels

Postby Manaz » Mon Jul 22, 2013 9:28 pm

Newbie GT wrote:
bigBADbenny wrote:afaik similar, the VF52 will drop off a little less due to the slightly larger compressor, afaik :)


Sorry Benny but can a tuner set to say 18psi and have it not over boost more than that ?


In theory, yes. That's what boost control and the wastegate on the turbo are for.

One thing to be aware of though are boost spikes - when boost increases sharply, and potentially goes beyond the boost limit the tune has set before the ECU realises what's going on and operates the wastegate. In general, boost spikes shouldn't happen with a good tune.
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Re: Safe tune boost levels

Postby dr20t » Mon Jul 22, 2013 9:34 pm

28 psi :)
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Re: Safe tune boost levels

Postby kiahatsiu » Tue Jul 23, 2013 9:59 am

24+
Kinda flush. Fitment is something. ADM as F*ck.
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Re: Safe tune boost levels

Postby spec.B » Tue Jul 23, 2013 8:54 pm

Newbie GT wrote:
bigBADbenny wrote:afaik similar, the VF52 will drop off a little less due to the slightly larger compressor, afaik :)


Sorry Benny but can a tuner set to say 18psi and have it not over boost more than that ?


Our ECU's run a PI controller (https://en.wikipedia.org/wiki/PID_controller) for boost, you set boost targets and the control loop tries to hit those targets, but input disturbances upset the system (shit happens and can cause boost spikes. The closer you set your targets to mechanical limits (clamping force of head studs) or closer to running your actuators at full saturation (wastegate duty cycle close to 100%) the higher the risk.

In more general terms, you have a requirement - more power. Let your tuner arrive at the best practice way to meet this requirement. Don't specify a solution to your requirement (some aspirational boost target for whatever reason).
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Re: Safe tune boost levels

Postby BlackSTI » Wed Jul 24, 2013 4:21 pm

Doesn't the stock BOV start leaking pressure at around 15psi (my thoughts would be that it would save damaging the engine, but it looks like this isn't the case).
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