Help understanding Fuel Cut and MBC'S - MR2 Owners Club Message Board
 
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post #1 of 11 (permalink) Old July 28th, 2019, 12:53 Thread Starter
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Help understanding Fuel Cut and MBC'S

Hello MR2 community, I've owned my bone stock 92 JDM MR2 GT for about 15 months and just recently installed a homemade fuel cut built following the toyodiy instructions and installed a new turbosmart in cabin mbc with the turbo. I used a bike pump and adjusted the fuel cut for 15lbs.

I have the turbosmart mbc at the lowest setting but the mr2 is boosting to 15lbs and then boost stops. The goal is to have a more conservative 12 lbs be where boost is set at, with fuel cut at 15lbs. My mods are TCS GEN2 intercooler kit, ATS racing throttle body inlet, TCS water neck, prosport 45mm boost gauge. Any thoughts as to why it's boosting to fuel cut?
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post #2 of 11 (permalink) Old July 28th, 2019, 15:59
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Have you set it to the correct lowest setting? How has the MBC been plumbed in?
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post #3 of 11 (permalink) Old July 28th, 2019, 17:32 Thread Starter
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Quote:
Originally Posted by GDII View Post
Have you set it to the correct lowest setting? How has the MBC been plumbed in?
Thanks for the reply, I follow instructions to the letter and I'm pretty good with cars (I've successfully rebuilt a transmission on my own) but this is my first turbo. Followed instructions and watched Pure Functions YouTube video on the mbc install but mine is a in-cabin.
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post #4 of 11 (permalink) Old July 28th, 2019, 20:55
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Fair enough. It can be hard to gauge ones experience with cars and their mechanical knowledge based on a very short post.

Thanks for the photos, it does help.

Would I be correct to assume the T is connected between the compressor housing and the waste gate diaphragm?
And it is installed as per this manual? This manual states if you have not disabled the factory boost controller you will get symptoms like what you are experiencing.
http://www.twosrus.com/Articles/Inst...structions.PDF
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post #5 of 11 (permalink) Old July 28th, 2019, 21:30 Thread Starter
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Fair enough. It can be hard to gauge ones experience with cars and their mechanical knowledge based on a very short post. <img src="https://www.mr2oc.com/images/MR2OC_2015/smilies/tango_face_smile.png" border="0" alt="" title="Smile" class="inlineimg" />

Thanks for the photos, it does help.

Would I be correct to assume the T is connected between the compressor housing and the waste gate diaphragm?
And it is installed as per this manual? This manual states if you have not disabled the factory boost controller you will get symptoms like what you are experiencing.
http://www.twosrus.com/Articles/Inst...structions.PDF
Thanks so much for all the help, people like you are a credit to the community. I'm sure you've solved my problem. I did not know that I had to disable the vsv. I'll do this tomorrow and post results. &#x1f601;
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post #6 of 11 (permalink) Old July 28th, 2019, 21:39
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No problem. I'm just providing information created by others in the community.

The MR2 has a slightly different way to control boost as it has a dual port waste gate actuator. So you need to have the second port blocked off that goes to the factory boost control solenoid AKA the T-VSV.
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post #7 of 11 (permalink) Old July 30th, 2019, 08:30
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If you have the Kinugwa waste gate instead of the stock to achieve a higher boost pressure, do you also need to block off the T-VSV? I have a fuel cut defender currently in place set to 15psi along with the Kinugawa (1.0 bar spring) and haven't been able to reach that 15psi (1.0 bar) with the stock downpipe and CAT. I've been assuming it's just because there's so much back pressure it's forcing the waste gate open and I need to move to a stronger spring as others have done. But, I've also got the T connector in connecting the turbo-waste gate-T-VSV that the Kinugawa came with. I had been able to get 15psi with an aftermarket downpipe that had a 120cel cat in it but moved back to the stock set up for CARB emissions and just wanting a less polluting car. Having a Tesla Model 3 in the family will regigger your brain.

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post #8 of 11 (permalink) Old July 30th, 2019, 16:01
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Originally Posted by senna21 View Post
If you have the Kinugwa waste gate instead of the stock to achieve a higher boost pressure, do you also need to block off the T-VSV? I have a fuel cut defender currently in place set to 15psi along with the Kinugawa (1.0 bar spring) and haven't been able to reach that 15psi (1.0 bar) with the stock downpipe and CAT. I've been assuming it's just because there's so much back pressure it's forcing the waste gate open and I need to move to a stronger spring as others have done. But, I've also got the T connector in connecting the turbo-waste gate-T-VSV that the Kinugawa came with. I had been able to get 15psi with an aftermarket downpipe that had a 120cel cat in it but moved back to the stock set up for CARB emissions and just wanting a less polluting car. Having a Tesla Model 3 in the family will regigger your brain.
If you are trying to adjust the boost pressure using means other than the OEM system you need to disconnect the T-VSV.
Downpipes do affect what the turbo can do. Less back pressure should allow it to boost better, not worse.

What PSI are you reaching? Sometimes the stock CT26 will barely make 14psi even with the MAP sensor pressure line disconnected. But that's with a 7psi spring, not a 14.7psi spring like you.

Last edited by GDII; July 30th, 2019 at 16:08.
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post #9 of 11 (permalink) Old August 3rd, 2019, 19:42 Thread Starter
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Problem fixed. Thanks again.
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post #10 of 11 (permalink) Old August 4th, 2019, 15:20
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Problem fixed. Thanks again.
What did it end up being? Not having the T-VSV disconnected?
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post #11 of 11 (permalink) Old August 4th, 2019, 23:39 Thread Starter
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Yes, my MR2 was actually starting to overboost with it still connected, it got up to 16lbs. Now it seems to be behaving like before with a slightly higher boost limit set at 12.
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