boost increase because of exhaust?

[DSMcamaro]

my autometer boost gauge tells me I'm at 11 psi. My car is basically stock except for the warblo 190lph pump. I built my own custom 2 1/2in. down pipe and complete 2 1/2" system (flexpipe, no cat, no muffler, and yes its too damn loud, putting a muffler on tomorrow).
While I was playing with the exhaust I figured I could do a little porting to the o2 housing. so I took off the housing and did a very mild port to the turbo side(of the o2 housing), and a fairly heavy port job to the exhaust side. After I had it all done I took it for a drive and I was surprised to see the boost gauge reaching 12 psi and even sometimes 13. I wouldn't think that the exhaust would cause a raise in boost pressure? this seem weird to anyone else or am i just missing something?

 

[oldman]

Do a search on boost creep.

 

[project_tsi]

your exhaust is flowing "too well". if you wanna cry about 1-2 psi, then do the halfass fix it and put on a high flow cat, and you wont see the creep anymore.

 

[oldman]

your exhaust is flowing "too well". if you wanna cry about 1-2 psi, then do the halfass fix it and put on a high flow cat, and you wont see the creep anymore.

Just get a mbc and turn the boost up to 14psi, I just wanted to make him search and read a little.

 

[blackGSX2g]

^ exactly...basically anything you do to open up exaust flow can potentially cause creep. Try running a stock evo III at stock 9psi with a full exhaust...you won't see anything less than 15psi.

 

[DSMcamaro]

thanks for the responses. My turboXS MBC just came in yesturday so i'll hooking that up soon hopefully. guess i'll be reading up on boost creep.

 

[kraka]

oooh..IF you got a turbo xs mbc then I'd also recommend you read up on Boost Spike!!

 

[DSMcamaro]

oooh..IF you got a turbo xs mbc then I'd also recommend you read up on Boost Spike!!

because of the brand name or just because its not electrical?

 

[oldman]

because of the brand name or just because its not electrical?

Possibly because because it's a bleeder type mbc rather than a ball & spring type. I have not use the Turbo XS mbc myself but from what I have read on this site, feedback seems to be mixed, either people love it or have problems with it.

 

[never2muchBoost]

get a hallman mbc, end of story

 

[DSMcamaro]

get a hallman mbc, end of story

woulda been nice to know before I bought the turboXS. (guess I could of did more research) and whats wrong with the turboXS MBC(besides that its not ball and spring)? it should still control the boost.

 

[oldman]

woulda been nice to know before I bought the turboXS. (guess I could of did more research) and whats wrong with the turboXS MBC(besides that its not ball and spring)? it should still control the boost.

A bleeder type mbc controls boost by bleeding off pressure (boost leak) resulting in pressure drop between the actual pressure and what the actuator sees, one would think that any fluctuation will effect your boost level. A ball and spring type mbc controls boost by blocking off the pressure source (no boost leak) until the desired boost level is reached. I have the Hallman EVO RX which comes with light weight ceramic ball that can move back and forth very quickly for precise control.

 

[djPlayboy]

woulda been nice to know before I bought the turboXS. (guess I could of did more research) and whats wrong with the turboXS MBC(besides that its not ball and spring)? it should still control the boost.

it will still increase boost and what not, it just bleeds off towards redline. a ball and spring helps hold the boost a bit more, i got a joep. mbc for 45 bux here http://www.boostcontroller.com/index.php?category=4it looks basic but there hand made by joe him self and there great.

 

[DSMcamaro]

well i hooked up the turboXS boost controller and it seems to do the trick. I got it set to 15 psi now (went to 20 on the first hook up ) and I can see it spike at around 17 sometimes. When i have time i'll do a pull with the logger to make sure everythings running alright. I'll post more if i end up having any problems with it.