Bad MBC??????????

[hottboost]

Alright, I fixed all boost leaks and put a new mbc in the car. http://www.slowboyracing.com/img/Turbosmart Boost Tee MBC.jpg It is a turbosmart base boost controler. Here is the problem, In order to run 19psi I have to tolerate a spike to 25psi. If I turn the mbc down then it will lower the boost. Now if I put the car in any gear at like 1800 rpms and go wot the boost will stay at 25psi but If I down shift with the revs high it will spike to 25psi then settle down. I have an adjustable wastegate actuator and have adjusted it every way I know how. Could this problem be solved with a different mbc. I did some searchs and it seems other people have had this problem with the turbosmart mbc. Thanks for the help

Carl

 

[Mr Peepers]

-Shorten the lines between the pressure source(and mbc) to your WG to increase its response.

-Use a pressure source that is as close to the compressor outlet as possible, again, better WG response.

-Don't tee off the BOV line(doesn't look like you did anyway from your pic). You guessed it, WG response.

 

[DSM4me44]

I had the exact same problem. Heres the two things that fixed that for me.

1. Use the nipple on the turbo housing, nipple on the J pipe, or install a nipple somewhere between you intercooler and turbo housing. I had a J pipe that came with my 14b install kit and i installed a nipple there. Spike occured when i tapped by BOV line for the boost controller.

2. Get a different MBC depending on what one you have. If you looking for something reliable, I got a Voodoo IV on ebay. You can pay a bit extra if you want a cermanic ball in it. It is supposed to reduce the chance for a spike, so i did that too.

I now only spike 1 psi if that.

Hope this helps...

BEN

 

[hottboost]

I have always used the nipple on the compresor housing. The link above shows a pic of the turbosmart mbc. Someone correct me if I am wrong but arent they supposed to be Tee'd to the bov. Long story short I have the hallman mbc and I will put that on this weekend and see if that helps. I have did multiple boost leak test to ensure that it wasnt that. Thanks for the help

Carl

 

[Talesin]

No, you are NEVER supposed to tee off the BOV/CBV line. That was the old way to do it, and a lot of lazy part manufacturers haven't updated their install diagrams. They also might be that way because not everyone may have a compressor outlet elbow vacuum nipple, and they don't want to have people calling in and complaining.

Short version: Teeing off the BOV line is a BAD IDEA. It's only perpetuated due to lazy marketroids and old install diagrams. Don't do it.

 

[hottboost]

Alright I installed the hallman mbc, the spike is not as bad but it still spikes about 7 psi. I have replaced the pcv valve twice, Is it possible that the pcv valve could be causing this? Guys I am lost and need some help. I have did multiple boost leak test, and adjusted the actuator multiple times.

 

[DSM4me44]

No, you pcv valve wouldn't have anything to do with boost.

This might seem stupid but, you are hooking up the MBC the right way with the right nipple connecting to the right source (compressor housing and wategate actuator)? I was just wondering if it was possible you reversed them.

You can also test your actuator by hooking a vacuum line up to it and fitting a tire valve stem to it. When you injectect air it opens, when you pull the valve stem off it shuts. You can verify that it is opening all the way.

 

[hottboost]

I just put the actuator on about a week ago.

 

[drewvr4]

i have the same problem with it spiking and holding a lower boost, but im using an ebc...im about lost at this point

 

[hottboost]

I am going to try to T back into the bov line because I know there is no boost leaks now. When I had it there befor it only spiked 2-3psi. Now if I do this I will find myself checking for boost leaks alot more often. When it was like this befor my Type S bov worked fine. Other than overboosting the turbo and the bov working properly what are the other dangers. Wouldnt I be better served with a 2 psi spike versus 6-7psi when conected to the compressor fitting? Also can I run the lower line from the bov to the compressor fitting instead of capping it?

 

[Mr Peepers]

One of the reasons you don't tee into the BOV line is the delay before the WGA sees pressure. The BOV line is routed from your intake manifold, so the intercooler and all its piping is in between. This usually increases boost spike.

 

[DSM4me44]

I am going to try to T back into the bov line because I know there is no boost leaks now. When I had it there befor it only spiked 2-3psi. Now if I do this I will find myself checking for boost leaks alot more often. When it was like this befor my Type S bov worked fine. Other than overboosting the turbo and the bov working properly what are the other dangers. Wouldnt I be better served with a 2 psi spike versus 6-7psi when conected to the compressor fitting? Also can I run the lower line from the bov to the compressor fitting instead of capping it?

No, you want to leave the lower one the way it is. Don't cap it off or run a line to it.

 

[hottboost]

Alright I got it fixed without t'ing to bov. I enlarged the mbc bleeder hole. Now it spikes about 4 psi. Thanks guys

 

[Mr Peepers]

Worked then huh? Can I ask what size the hole was previously and how much larger you made it? Glad to see my theory held up Even though I still would have waited for a wiseman's opinion

 

[hottboost]

It was 1/16! I drilled it out to 5/64. It is only about a 4-5 psi spike now. I am wondering if I should go to the next size?? What do you think? I had an old home made mbc that I tested befor I drilled the hallman pro. Now everything is put back. I changed all vacuum lines. I am going to take the uicp off this week and drill it out for a fitting that I can run to the lower nipple on the Type S bov. I am getting compressor surge when I have it tight enough to hold boost.

 

[Mr Peepers]

Answered in this post:

http://www.dsmtuners.com/forums/showthread.php?t=262063

Also the idea behind it if anyone was interested/wanted to critique.

 

[DSM4me44]

It was 1/16! I drilled it out to 5/64. It is only about a 4-5 psi spike now. I am wondering if I should go to the next size?? What do you think? I had an old home made mbc that I tested befor I drilled the hallman pro. Now everything is put back. I changed all vacuum lines. I am going to take the uicp off this week and drill it out for a fitting that I can run to the lower nipple on the Type S bov. I am getting compressor surge when I have it tight enough to hold boost.

If your getting compressor surge I would strongly recommend you do the single spring mod to your greddy rather then hook the lower nipple up.

 

[hottboost]

Why do you recomend that? It seems that either way people say it will work. Take a look at this ... http://www.evomoto.com/tech_info.php?tech_id=7! Also RRE as a write up also
http://www.roadraceengineering.com/instructions/rreicpipeinstructions.htm. Just a thought, tell me what you think.

 

[DSM4me44]

Why do you recomend that? It seems that either way people say it will work. Take a look at this ... http://www.evomoto.com/tech_info.php?tech_id=7! Also RRE as a write up also
http://www.roadraceengineering.com/instructions/rreicpipeinstructions.htm. Just a thought, tell me what you think.

I have had nothing but good luck with the single spring mod. I can hold 19 psi no problem.

Both myself and my buddy have tried hooking the lower nipple up. On partial throttle I spiked to 25 psi and he spiked to 26 psi.

Hooking up the lower nipple requires yet another T and another vacuum line to be run through the engine bay. The less lines I think the better. I eliminated my emissions system so that I wouldn't have to to worry about more then just a couple lines for boost leaks and such.

However, you are right. You can hook the lower nipple up, but just from experience I would say go for the SSM.

 

[hottboost]

I have had nothing but good luck with the single spring mod. I can hold 19 psi no problem.

Both myself and my buddy have tried hooking the lower nipple up. On partial throttle I spiked to 25 psi and he spiked to 26 psi.

Hooking up the lower nipple requires yet another T and another vacuum line to be run through the engine bay. The less lines I think the better. I eliminated my emissions system so that I wouldn't have to to worry about more then just a couple lines for boost leaks and such.

However, you are right. You can hook the lower nipple up, but just from experience I would say go for the SSM.

Here is what I ended up doing. I drilled and tapped a fitting on LICP and ran a vacuum from there to the lower nipple on the bov ( no tee's ). I shortend the actuator arm some more and tightend down the bov very tight. I spent the last 2 hours re tuning the safc as my boost would hit 22psi and settle to 19psi by redline. Got to where it climbed a nice smooth timing line with no dips. Then ran a few more pulls to moniter egt's and it peeked at 835* C at the top of 3rd and only moved a little bit as I shifted to 4th and kept it wot. We will see how it does but I finally got it to where I want it. THANK YOU TO ALL WHO HELPED AND GAVE INPUT!!!

Carl