For anyone with a homemade mbc T fitting, spring, bearing, bolt type mbc....
06-10-2004, 01:52 PM
#1
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Join Date: Apr 2003
Posts: 2,612
For anyone with a homemade mbc T fitting, spring, bearing, bolt type mbc....
I installed one on Monday and first I adjusted it shooting for 10psi. The psi would go to 10-11 and drop down to 6 1/2
without a bleeder hole. Then I turned up the boost to peak at 14 psi and then it would go back down to 10 psi by 8k rpm. That's a 4 psi drop! I drilled a 1/32" hole under the spot where the internal wastegate goes a.k.a. "bleeder hole" and turned the boost down a little and it went from 12 psi to about 9 psi, small improvement. Then I drilled a 1/16" hole through the previosly drilled 1/32" hole and went for a test run on the expressway of coarse. After adjusting the bolt on the mbc one more time, now boost peaks at 10 1/2 psi and then goes to 9 psi.
Very big improvement compared to when I had no bleeder hole at all! peaking 14 psi only to come back down to 10 psi. Now it peaks at 10 1/2 psi and comes down to only 9 psi. A 1 1/2 psi drop, as compared to a 4 psi drop. I think I can live with that. This isn't a question, it's an experiment I did with the mbc that turned out alright incase it could help anybody out.
without a bleeder hole. Then I turned up the boost to peak at 14 psi and then it would go back down to 10 psi by 8k rpm. That's a 4 psi drop! I drilled a 1/32" hole under the spot where the internal wastegate goes a.k.a. "bleeder hole" and turned the boost down a little and it went from 12 psi to about 9 psi, small improvement. Then I drilled a 1/16" hole through the previosly drilled 1/32" hole and went for a test run on the expressway of coarse. After adjusting the bolt on the mbc one more time, now boost peaks at 10 1/2 psi and then goes to 9 psi.
Very big improvement compared to when I had no bleeder hole at all! peaking 14 psi only to come back down to 10 psi. Now it peaks at 10 1/2 psi and comes down to only 9 psi. A 1 1/2 psi drop, as compared to a 4 psi drop. I think I can live with that. This isn't a question, it's an experiment I did with the mbc that turned out alright incase it could help anybody out.
06-10-2004, 02:48 PM
#2
3.0 BAR
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Join Date: Apr 2003
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Re:For anyone with a homemade mbc T fitting, spring, bearing, bolt type mbc....
Does anyone here's boost go down just a little after reaching full boost, 1- 1 1/2 psi maybe? If so what kinda boost management you usin?
06-10-2004, 03:20 PM
#5
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Re:For anyone with a homemade mbc T fitting, spring, bearing, bolt type mbc....
I got them at a hydraulic supply store, I found what seems to be a better mbc in the FAQ: http://www.lotuselancentral.com/mbc.htm
this mbc on the link limits the air going to the waste gate and it goes hooked up directly to the compressor houding. While the one I built goes connected to the BOV and the compressor housing gets capped off. I think a bleeder hole of 5/64" just 1/32" bigger than the hole I have on there now will probably give me no boost drop at all after peak boost. Now I have a 1/16" hole and it drops the psi only 1 3/4 psi compared to no hole and seeing a 4 psi drop after full boost. If that doesn't do the trick I'm gonna get one like in the link above. And if that doesn't do the trick lol, I'll just keep it how it is, 1 3/4 psi drop is better than the 4 psi drop it had before
this mbc on the link limits the air going to the waste gate and it goes hooked up directly to the compressor houding. While the one I built goes connected to the BOV and the compressor housing gets capped off. I think a bleeder hole of 5/64" just 1/32" bigger than the hole I have on there now will probably give me no boost drop at all after peak boost. Now I have a 1/16" hole and it drops the psi only 1 3/4 psi compared to no hole and seeing a 4 psi drop after full boost. If that doesn't do the trick I'm gonna get one like in the link above. And if that doesn't do the trick lol, I'll just keep it how it is, 1 3/4 psi drop is better than the 4 psi drop it had before
06-10-2004, 10:23 PM
#8
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Join Date: Dec 2002
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Re:For anyone with a homemade mbc T fitting, spring, bearing, bolt type mbc....
if your mbc is mounted inline between the compressor outlet line and wastegate actuator...ditch the ball and spring deal and use a needle valve and bleed the boost instead of drilling bleed holes and using the ball and spring. it's basically what you're doing now by drilling the holes and ball and spring is worthless.
mine holds 11-12psi w/o any problems by bleeding the boost signal going to the actuator. it makes the turbo spin more and build more boost before the stock setting is seen by the actuator.
the bleeder style won't work if you are getting your signal from the manifold and you will be forced to use a ball and spring type or your engine will idle like crap because it see's it as a vac leak.
mine holds 11-12psi w/o any problems by bleeding the boost signal going to the actuator. it makes the turbo spin more and build more boost before the stock setting is seen by the actuator.
the bleeder style won't work if you are getting your signal from the manifold and you will be forced to use a ball and spring type or your engine will idle like crap because it see's it as a vac leak.
06-11-2004, 10:13 AM
#9
3.0 BAR
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Join Date: Apr 2003
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Re:For anyone with a homemade mbc T fitting, spring, bearing, bolt type mbc....
Thanks for the advice. I got tired of messing with that spring & ball mbc and ordered a turbo xs mbc that hooks up between the waste gate and the turbo compressor housing off ebay last night $77. more than a home made one but I got a little frustrated with the mbc I got now and didn't want no more hassles. Plus the turbo xs mbc looks cool.
