Greddy Type S + MBC = Boost Spike?

[95CarbonEclipse]

I just finished hooking up the lower nipple on my type S BOV by 'T'ing into my MBC>Compressor Housing Nipple. Before, i used to have a boost spike to about 15psi and would settle down around 11-12. Now, it's spiking to around 18 or so. I've got my MBC hooked up like this: http://dsmtuners.com/forums/showthread.php?t=237982 only with the lower Type S nipple tee'd into the hose that comes off of the compressor housing. Couple questions about this...

1. Is this a 'normal' amount of spike on a stock T25?

2. If there is a better way to hook my lower nipple up then this, what would it be? (anywhere on the IC pipe before the BOV?)

3. When people say they have they're MBC dialed to 15 psi, they're talking about once it steadies, not the spike, right?

 

[matthewdesigns]

Here's a link to proper connections for the upper and lower nipples: http://herpetology.com/dsm/bov.html

I have a type s and I have not used the lower nipple. It is only used to help open the valve more quickly. Perhaps you are spiking higher now from the added pressure under the diaphragm, before the pressure on top builds and helps hold the diaphragm down. Try running without the lower nipple connected to a pressure source and see if you spike as high.

 

[95CarbonEclipse]

Try running without the lower nipple connected to a pressure source and see if you spike as high.

I did. Did you even read what i posted before i asked the questions?

I just finished hooking up the lower nipple on my type S BOV by 'T'ing into my MBC>Compressor Housing Nipple. Before, i used to have a boost spike to about 15psi and would settle down around 11-12. Now, it's spiking to around 18 or so. I've got my MBC hooked up like this: http://dsmtuners.com/forums/showthread.php?t=237982 only with the lower Type S nipple tee'd into the hose that comes off of the compressor housing. Couple questions about this...

 

[oldman]

Why did you decide to hook up the lower nipple? Spiking to 15 and settle to 12 is pretty normal for a T25.

 

[95CarbonEclipse]

I recently took my car to a shop to have a leakdown test performed. While it was there they fogged the IC plumbing to visually look for boost leaks. When i got the car back they told me that a hose on my BOV had come off and that i was leaking from there. I thought to myself "that's pretty wierd" so when i got home i inspected it myself and found that they had capped off the lower nipple on my BOV.

After doing a couple quick searches i see that there is a bit of controversy on whether or not one should hook up the lower nipple to a pressure source. I didn't read anything negative about doing so, so i figured that if it's a possible leak source it'd be best to hook it up.

 

[oldman]

Be more clear so we don't go back and forth.

1. Did they tell you it was leaking out of the lower nipple they capped off or are you just guessing? Where exactly did they say was leaking?

2. How did they run this "fog test"? Fill up the intake with fog while the car is running?

 

[95CarbonEclipse]

1. They just told me that "a hose from my BOV had come off and that it was leaking from there." I assumed at the time they were talking about the main hose that goes to the IM (that's the only hose that i had hooked up to it). But after thinking more about it, i was just under the hood the day before and there wasn't any significant changes in performance between then and when i took it to the shop. Hell, i didn't really notice any difference after taking it to the shop either. So, i 'assumed' that they were talking about the lower nipple when i discovered the cap on it.

2. I haven't seen them actually perform the fog test, but from how it was first described to me months ago when i first got the car is that they fill the IC pipes up (car off) with some sort of smoke/fog while at the same time pressurizing the system (i later found out that they only pressurize it to 2-3psi), obviously any leaks would be noticable by the exiting smoke.

I'm surprised that this hasn't been talked about on the forum before. It's too bad too, b/c i was trying to think of a way to build my own.

 

[oldman]

1. Is your BOV recirculated?

2. Fog test is not for boost leak testing, forget what they say/did and perform your own boost leak test.

3. Remove the hose from the lower BOV fitting, cap it off or VTA. See this awesome tech article to understand the purpose and functions of the lower fitting.

4. Restore your boost reference line as a standalone line going from compressor housing to MBC.

5. Like I said in my previous post, spiking 3 extra psi before settling on boost setting is a normal behavior, along with further drop off at 5.5k+ RPM, for a T25, what was the reasoning behind taking your car to the shop for a leakdown in the first place? Low compression numbers?

 

[95CarbonEclipse]

1. Yes

2. I have performed my own boost leak tests and can't find any other leaks, but i'm still not getting 100% correct performance.

3. Okay

4. Okay

5. Burning oil and poor performance. See this thread for more on this issue: http://www.dsmtuners.com/forums/showthread.php?t=256238