different idea on use of MBCs

OneJoeZee

OneJoeZee

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Mar 30, 2005
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ok so im having a spiking issue with my MBC setup on my car. im pretty positive its just the nature of the twins super quick spool and the long length needed to tee both turbos together that are causing this. im talking like spiking to 1.3-1.4BAR then settling at my target boost at about 1BAR.

i was thinking since the turbos are true twin and not linked to each other in any way i could use two separate MBCs for each turbo. and also use separate gauges for each individual turbo to monitor then and make sure they are even in addition the normal final manifold pressure boost gauge. this would let me keep the lines very short to optimize response of the MBC and overall response of the car itself with elevated boost levels

heres what the normal setup looks like for one MBC

ic4u44.jpg


and heres the theoretical idea im talking about

ic5t0g.jpg


sounds a little strange i know. but i think the idea is sound and innovative. am i crazy? what do you think...
 
OneJoeZee

OneJoeZee

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yeah, i was reading Stu Hagen's thread about his TTC setup with an MBC but it doesnt really apply to the 1J lacking all that mess of vacuum lines

i really do think its a sound idea to maximize response from the turbos, but we wont know until i try. as soon as i get a hold of a couple more gauges and another MBC ill shed some more light on it.

if it works, great. if not i can cut my losses and sell some stuff back again. we shall see
 
Idealsupra

Idealsupra

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Mar 31, 2005
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the truth of the matter joe is that spiking is a cause of a mbc PERIOD.... i mean sure not everyone will experience it but its one of those things where its one of the downsides of a mbc....

your idea MIGHT work but the fact is a mbc always has the ability to create boost spikes. thats why theres EBCS ;)
 
OneJoeZee

OneJoeZee

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i dont think so dude. i used the same style MBC on my 7M and it worked just fine

i can tell its a cause of long lines.

if i give it gas real quick i can see it swing too high first. if i give it gas, let off a bit and wait for the MBC to catch up then get back into it i can hold boost just fine. ill play with it alittle more and update.

i tested it by hooking up the MBC to just the first turbo and upping it a bit. it hit BAR right on and held it there. then i switched to the current both turbo setup and spiking is serious. i dont see why redoing what i did with the first turbo with both would be bad. but only time will tell

im still going to try the idea as i believe its a worthy cause. we'll see
 
M

mullenc525

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Apr 4, 2005
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Sounds like a good idea, its worth the experiment at least.

Having two extra boost gauges is pointless though. Its tough to explain (i will try) but if the mbcs are set anywhere close to each other, the wastegates will also be close to one another. Even if you get a higher shaft speed out of one turbo, the outlet pressures will be the same because they are linked by a short pipe. What will happen is the higher shaft speed turbo will be flowing more. Since flow is much much harder to measure (you cant do it with any simple setup), your better off just using two identical MBCs and setting them at exactly the same preload. You can be guaranteed the outlet pressure will be the same, and the shaft speed and flow will be very similar.

When I say the pressures will be the same, I mean you wont be able to tell on a boost gauge. The pressure may be 0.1 psi different for example.
 
IHI-RHC7

IHI-RHC7

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Apr 1, 2005
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Joe, I think it's because your 7m wouldn't spool as quick as the little ct12s that made it not spike in the 7m. Manual boost controllers spike. That's why I switched to an EBC.
I've ran 4 ft of vac line (don't ask why;)) And never had spikes with the AVC-r, it's because it learns how fast the turbo spools and opens the gate before max boost is reached to keep if from spiking. Without the AVC-R, the gate won't open until 14 psi with an MBC, but with an ebc, I get super quick spool and the gate opens 8 psi, and then boost pretty much gets cut off right @14 psi. In order to get 14 psi with a manual boost controller, your turbo has to spool slow, or you have to spike to 17-18 psi, and then settle.
 
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itr206

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Idealsupra said:
the truth of the matter joe is that spiking is a cause of a mbc PERIOD.... i mean sure not everyone will experience it but its one of those things where its one of the downsides of a mbc....

your idea MIGHT work but the fact is a mbc always has the ability to create boost spikes. thats why theres EBCS ;)
Click to expand...

I have had a ton more better experiences with MBC;s then EBC's.

Joe what MBC are you running. That is probably where it lies.
There are good ones and there are bad ones.
 
OneJoeZee

OneJoeZee

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i ordered one from adam (dr j). maybe there wasn't anyone ever using ont on a 1J and it just wasn't meant for it.

what are you using pete?

yeah, the two extra gauges is a little much but i brought it up more for ease of seeing how both are working instead of doing one then switching signal then doing the other. in the drawing i had the boost signal reading off each turbo housing before the wastegate. would that not be the proper location if this method were used?

its just an idea... and i appreciated the friendly debate
 
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itr206

Guest
I am sure Adam knows his stuff, but IMO when you pay $20-30 for a controller, what do you expect from it?
Get a Well known MBC and pay the extra money for a good proven one and tell me the difference. I bet you will see it.
I run a turbo xs dual stage now and it sticks dead on. I ran a Hallman before and stuck 100% too. EBC's are headaches for me most of the time.

It wont be designed for a specific app Joe. They just do what they were built to do. Some just work better then others due to the parts and precision used in assembly.
The people having problems with MBC's are using cheaper ones.

You can get a Hallman for like $70 and I bet that will make a nice diff. If you were closer Id let you use mine as a test
 
Joel W.

Joel W.

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Nov 7, 2005
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ive heard of drag racers using pressurized air tanks and dual port actuators to get very constant and precise boost control at what ever psi they want...
i have a friend building one now, im very much wanting to see it work... ;)
 
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itr206

Guest
Ive never seen that.
I have seen more people running directly off springs

More people are going with EBC units now a days becuase of the boost by gear and rpm and such.
Before that MBC's were mostly used from my memory
 
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