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Discussion Starter #1
Hey i am fully catless now, (just got my uppipe in). So my question is can i turn my boost up, its at about 1 bar, a hair below it??? Which is like 15.9 psi....I remeber reading somewhere u can go up to like 16.5 safly catless..is this correct?

I have a turboxs mbc

I just want to feel that extra power before i get rid of my mbc for accessport in 9 weeks.:rolleyes:

Thanks
Tom
 

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NO EM? I wouldn't touch boost.

Jack said:
Hey i am fully catless now, (just got my uppipe in). So my question is can i turn my boost up, its at about 1 bar, a hair below it??? Which is like 15.9 psi....I remeber reading somewhere u can go up to like 16.5 safly catless..is this correct?

I have a turboxs mbc

I just want to feel that extra power before i get rid of my mbc for accessport in 9 weeks.:rolleyes:

Thanks
Tom
 

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Discussion Starter #7
Re: Re: Fully Catless...MBC can go up?

BrianH said:
NO EM? I wouldn't touch boost.
I have been for the past two years, nothing bad so far.:D
 

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Discussion Starter #9
BrianH said:
good, consider yourself lucky then.

I say turn it up to 19 then, em doesn't matter anyways.
Turning it up to 19 right now and returning my accessport! Thank you for ur replys!:wiggles:
 

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The most you should go is 16 PSI with all the cats. Any more and the fuel system will run out of breath at higher RPMs.

Removing the cats will up the volumetric efficiency of the engine, requiring the turbo to push less to produce the same power levels (simlified much). A car with all cats and 16 PSI may max out the fuel system (mine did), with more VE a car with no cats and 15 PSI might max out the system so the rule is just dont mess with it unless you can safely monitor your air/fuel ratios.

I've generalized, but you get the idea.

-Chris
 

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Discussion Starter #13
cdvma said:
The most you should go is 16 PSI with all the cats. Any more and the fuel system will run out of breath at higher RPMs.

Removing the cats will up the volumetric efficiency of the engine, requiring the turbo to push less to produce the same power levels (simlified much). A car with all cats and 16 PSI may max out the fuel system (mine did), with more VE a car with no cats and 15 PSI might max out the system so the rule is just dont mess with it unless you can safely monitor your air/fuel ratios.

I've generalized, but you get the idea.

-Chris
So ur saying if i run 100 Oct i can safly run 16.5 psi and still feel the results?
 

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Jack said:
So ur saying if i run 100 Oct i can safly run 16.5 psi and still feel the results?
timing plays a bigger role in power then boost does. you'll be able to run more boost, sure. the stock turbo has it's limits as well, and with a mbc, you aren't going to be able to run 17psi in the midrange and then have it taper to 14psi (or something) at the end, when all the supporting mods are there.

i'd leave it at 16psi in 4th to be safe. there really isn't a reason to push it any further.
 

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When I was talking to Nathan @ TXS about this, he said that if you want a reliable car(down the road) it is not a good idea to use a MBC w/o EM. On the other hand he said it is a great and cheap way to make HP.

In this months current Import Tuner mag I believe they got around 20hp to the wheels with a MBC from TXS.

So, I guess what you do know may affect your reliability later in your car's life.
 

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BrianH said:
good, consider yourself lucky then.

I say turn it up to 19 then, em doesn't matter anyways.
Now that we are talking about it. I can say that I have been running stock car w/ prodrive axel back and MBC @ 20psi for 1 year without any problems, then added a uppipe and ran the same boost for 6mnd still no problems.... This was on 98octane..

My old car Audi A4 1.8tq boosted 23psi on stock turbo & exhaust..
The little turbo got totally destoyed but the engine was fine untill the timing belt snapped ;)

Ps I'm not saying boosting 20psi is safe ! This is on a euro spec car (don't know if there is anything different between them and with 98octane fuel)
 

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Roffa said:
Now that we are talking about it. I can say that I have been running stock car w/ prodrive axel back and MBC @ 20psi for 1 year without any problems, then added a uppipe and ran the same boost for 6mnd still no problems.... This was on 98octane..

My old car Audi A4 1.8tq boosted 23psi on stock turbo & exhaust..
The little turbo got totally destoyed but the engine was fine untill the timing belt snapped ;)

Ps I'm not saying boosting 20psi is safe ! This is on a euro spec car (don't know if there is anything different between them and with 98octane fuel)
I don't know the details of a euro-spec, but I don't see any reason to run the stock turbo at 20psi (at any rpm range) unless the euro-spec uses a different stock turbo. i've heard of a few stock turbo setups that definatly push 17psi or a little more on the stocker, but taper down towards redline. mabye it's me, but timing seems to play a larger role then boost. this of course is assuming the euro wrx and the us wrx are the same as far as engine, turbo, etc.
 

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Set it at 15psi and leave it, i went 13.36 with a mbc set at 15psi, so with your full exhaust and 15psi, you should be making pretty good power.

Oh ya.....had a mbc on the car for over a year now with no negative side effects at all.

steve
 
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