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Old 01-20-2005, 07:34 PM   #1
blackie
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Default Adding a mbc to hit target boost???

hello, im currenntly running Cobbs stage 2.5 map with a vf34, header, fuel pump, and larger intercooler and im not hitting target boost anymore because of my header and large tmic. i even use cobbs restrictor and i only hit 15-16 psi max (if im lucky) with my vf-34 i know i should be safe at 17-18 psi. i want to use a MBC to band-aid my problem. does anyone have experience doing somthing like this? will using the new MBC to controll my boost have any negative effects with my set-up?
also what is the correct way to install a mbc? do i still use the oem boost controll solinoid along with the mbc, or just use the mbc by itself? also will i leave the restrictor on with the mbc or take it off? thanks.
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Old 01-20-2005, 07:54 PM   #2
zaxrex
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if you do a search on over in the EM tuning forum, there was a post I caught where that was deiscussed.
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Old 01-20-2005, 08:06 PM   #3
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Quote:
Originally Posted by zaxrex
if you do a search on over in the EM tuning forum, there was a post I caught where that was deiscussed.
i did a search and found nothing, which thread are you reffering too?
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Old 01-20-2005, 08:09 PM   #4
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Adjusting wastegate arm may be a better way to go than a MBC. At least that is what i would try first.
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Old 01-20-2005, 08:53 PM   #5
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i dont have an adjustable wastgate arm, thats why i think my only option now is get a mbc.
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Old 01-20-2005, 08:59 PM   #6
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Woops OK then i would go for the dual MBC
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Old 01-20-2005, 11:15 PM   #7
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try and MBC and try to log it with someone elses delta dash, it sound be fine cuz cobb takes care of PTFB.
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Old 01-20-2005, 11:50 PM   #8
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If i use a mbc how can my Cobb ecu take care of PTFB? do you always get PTFB with a MBC?
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Old 01-21-2005, 12:19 AM   #9
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Yes, PTFB is the main problem with MBC. Thats why you need a dual stage MBC With a switch that you control or is controlled by the TPS. Set one at 8 to 10 PSi for normal driving, the other at 17.5 or more when TPS is 90% or more. I never actually tried this but i'm thinking about it.
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Old 01-21-2005, 12:33 AM   #10
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Quote:
Originally Posted by wrxdrvr
Yes, PTFB is the main problem with MBC. Thats why you need a dual stage MBC With a switch that you control or is controlled by the TPS. Set one at 8 to 10 PSi for normal driving, the other at 17.5 or more when TPS is 90% or more. I never actually tried this but i'm thinking about it.
wow thats sounds really cool! what could be used as the window switch on the tps sensor though??? maybe just have the high boost come on at WOT, that would be pretty cool and alot easier to set up, what do you think?
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Old 01-21-2005, 12:42 AM   #11
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what the hell are you guys talking about

COBB MAPS EXTRA FUEL FOR PART THROTTLE FULL BOOST, therefore that problem with a MBC is NULL. Have you ever gone 60% throttle on your cobb? notice you go past 10 psi?

i dont know about the part mbc possibly throwing the boost curve off.
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Old 01-21-2005, 02:46 AM   #12
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Why not just tune it in for the added components.. oh wait thats right cause you can't, all the more reason to get a UTEC. J/K Yeah a MBC will do want you want, just be warry of the PTFB conditions that come with owning a MBC, and watch your EGT.
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Old 01-21-2005, 10:39 AM   #13
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well my egt gauge is inop right now, i will try this and use a wide band o2 to make sure its all good.
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Old 01-21-2005, 10:50 AM   #14
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Yes i think a WOT switch would be easier but like ben wrx said, cobb maps go to full boost after 60+ % throtle so throtle position sensor switch would be the best. I was thinking 90% before but that was for stock.
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Old 01-21-2005, 11:52 AM   #15
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Target boost for your map is 16.5 +/- .05, so if your only hitting 16 your not that far off. Have you tried resetting your ECU? I am a huge COBB guy, but if you want to run outside your setting ( like 17 or 18psi) I would have to say go with a tunable version or you could wait for the access tuner like me !
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Old 01-21-2005, 01:01 PM   #16
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well i installed a TXS MBC and this is what happened, i set it to 17 psi and and it builds boost faster and stops right at 17 psi with no spikes at all, its also very consistant as compared to the slower oem ebc. i guess just as long as i stay at 17 psi everything should be ok. what do you guys think?
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Old 01-21-2005, 01:16 PM   #17
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As long as you can keep the boost uder 10 PSi at under 60 % throtle it should work with no troubles. That's hard to do, but can be done . I had my MBC on for 2 years with no probs. Just had to change the way i drove. Now i'm not recommending a MBC just saying it can be done if you know what to watch for, and can make yourself do it.
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Old 01-22-2005, 09:55 PM   #18
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Default Sorry it took so long. Been bussy...

I searched back and found what I was thinking of here , now I'm off to the airport in 8 hours to leave the snow behing and go skiing in rainy BC's Whistler.
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Old 01-22-2005, 10:45 PM   #19
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Quote:
Originally Posted by wrxdrvr
As long as you can keep the boost uder 10 PSi at under 60 % throtle it should work with no troubles. That's hard to do, but can be done . I had my MBC on for 2 years with no probs. Just had to change the way i drove. Now i'm not recommending a MBC just saying it can be done if you know what to watch for, and can make yourself do it.
cobb accessport has PTFB, people ened to get with it
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Old 01-23-2005, 12:58 AM   #20
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Quote:
Originally Posted by bren wrx
cobb accessport has PTFB, people ened to get with it
Not as much compensation on the VF34 maps.

On the top end towards redline is where I would be worried with a MBC and Cobb stage 2.5.
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Old 01-23-2005, 02:05 AM   #21
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he can check it with his wideband, get a walbro 255 in there
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Old 01-23-2005, 02:47 AM   #22
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Quote:
Originally Posted by bren wrx
what the hell are you guys talking about

COBB MAPS EXTRA FUEL FOR PART THROTTLE FULL BOOST, therefore that problem with a MBC is NULL. Have you ever gone 60% throttle on your cobb? notice you go past 10 psi?

i dont know about the part mbc possibly throwing the boost curve off.
Huh? What are you talking about? It doesn't matter if Cobb cars "normally" hit high boost levels at part-throttle. Cobb uses the factory boost controller and MAP sensor to determine boost level, and the amount of fuel to put in. Therefore, with a Cobb ECU, you can hit higher boost levels at part-throttle, and it will compensate for it. But if you get a MBC, then the factory MAP sensor is unable to see the "true" amount of boost, so there is a very HIGH chance you will be running extra lean. That's no good for your car. Your car might run 16 psi while the Cobb ECU is giving fuel for an expected 12 psi. I have never seen anywhere that Cobb says you can use a MBC with their maps. They already lean it out more than stock, so running a MBC on a Cobb ECU is MORE dangerous in my opinion than running a MBC on a stock ECU. Of course, if you carefully watch how you drive, you can avoid PTFB while driving. But that's a big chance to take on your motor imo.
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