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Old 12-15-2010, 12:00 PM   #1
xluben
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Default 2011 WRX - Boost Taper - Stage 1 vs Stage 2

I was looking at the plots of the 2011 WRX, Stock, Stage 1 and Stage 2. With each upgraded level the peak boost increases. This is what I expected. But what I noticed is that the Stage 2 tune has the boost tapering off to actually be quite a bit lower than the Stage 1 boost in the upper RPM range. This results in the Stage 1 and Stage 2 tunes having nearly identical HP and TQ above ~5,250RPM's. What is the reason for the difference in boost taper?

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Old 12-15-2010, 12:14 PM   #2
Cobb Tuning
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Hello, thanks for your question...it's a good one I found the stock TMIC to be prone to heatsoak when running boost levels that did not taper. After quickly repeated runs it would cause detonation at higher RPM. The increased airflow of Stage2 helped make the same WHP as Stage1 using less boost while still providing a nice increase to WTQ down low. I'd recommend a nice TMIC or FMIC setup for these cars even at the Stage2 level in order to really take advantage of the potential. Hopefully that answers your question and please let me know if I can be of assistance in any other way.

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Old 12-15-2010, 12:43 PM   #3
xluben
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So would the Stage 2 tune actually be considered "safer" than the Stage 1 tune (due to lower boost at high RPM)?

If the IC were upgraded, what power would you expect to see without the boost taper? It looks like it might be a +10 or +15hp gain over Stage 1.
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Old 12-16-2010, 11:51 AM   #4
Cobb Tuning
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Quote:
Originally Posted by xluben View Post
So would the Stage 2 tune actually be considered "safer" than the Stage 1 tune (due to lower boost at high RPM)?

If the IC were upgraded, what power would you expect to see without the boost taper? It looks like it might be a +10 or +15hp gain over Stage 1.
In a sense, yes, though the amount of stress placed on the engine is probably relatively similar when power output is similar. I would expect the Stage2 setup to be less prone to knock under extreme condition though

I'd say that 10-15whp is indeed a pretty good estimate! The factory TMIC is just so easy to overrun on these cars. 'Tis really a shame the STi piece won't bolt on, but there are a few decent options available.

Thanks for your questions and please let me know if I can of assistance in any other way.

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Lance
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Old 12-16-2010, 01:09 PM   #5
xluben
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Are you saying that the WRX is topped out at 255hp with the stock TMIC?
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Old 12-17-2010, 05:46 PM   #6
Cobb Tuning
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Quote:
Originally Posted by xluben View Post
Are you saying that the WRX is topped out at 255hp with the stock TMIC?
Not necessarily, but the stock turbo does certainly begin to tax the TMIC at that power level. It is apparent when working with an STi that the larger TMIC on the STi is a benefit.

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Old 12-17-2010, 07:59 PM   #7
arf80
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Would you recommend a BPV as well to hold the increased boost? I know the plastic units have been leaking.
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Old 12-17-2010, 09:50 PM   #8
Blue_Rex
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I was wondering about the reduced boost at stage 2; is generating the same power at what appears to be lower manifold boost pressures a result of the pressurized air being able to flow more efficiently into the cylinders due to the improved exhaust flow, which make the manifold pressure read lower? Kind of like how you can retard timing to increase spool, but still run like a dog because the manifold pressure increases because the air isn't going anywhere? Or something like that. This is likely a very n00b post.
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Old 01-18-2011, 04:24 PM   #9
fulltimeW.O.T.
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this question might be slightly out of place, but I am completely puzzled and can't find an answer anywhere. Looking at Cobb's site under maps. How come the 2009 wrx stage 2 makes more power than stage2 2010 or 2011? I am almost certain the hardware is identical between them. Looking at the percentage of gain, the 09 is way higher on any given map than the 2011. Is this because the stage 2 map for the 09 is simply more aggressive? I am lost.
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