Lost boost with downpipe and test pipe

[bankyf]

Just installed a 3" downpipe and test pipe last night and seem to have lost some boost. I am still using the stock boost control, but with my other mods I was seeing a 17 psi spike on shifts and settling around 14-15psi. After installing the downpipe/test pipe it still spike around 17, but it settles to around 11 - 12psi. It does not feel like I have lost any power and I could turn the boost back up with a manual boost controller, but I just wanted to know if this was normal and why.

 

[larryd]

doesnt make any sense becuase most people gain boost by adding those mods.. do you still have the BCS in place?

 

[Golden4g63child]

Are you still with the stock turbo? If so, that can also be the problem because 3 inch is overkill for the stock turbo.

 

[bankyf]

Stock BCS and stock turbo are still in place. I know it is probably overkill, but I still have the restriction of the stock catback. Even going on the overkill theory it does not make sense. I guess more/same power with less boost is always a good thing, I just would like to know why it happened. Could it be that the computer is seeing the limits of the fuel system and turning back the boost for me? If so, maybe the manual boost controller isn't such a good idea.
Banky

 

[cmc]

Your working backwards, a stock catback w/ a 3" DP!!!!

 

[bankyf]

I know, but I don't really want to do the catback. I have been through my days of Mustangs with loud exhaust and I guess I outgrew it or something. I don't find loud exhaust appealing anymore and sometimes even consider it annoying. Anything much louder than stock will be too loud for me, and I am not convinced that there is an aftermarket exhaust that will meet my demands. The amount of noise added from the downpipe was acceptable, but I am not sure it added any power. The boost has returned out of nowhere and is higher, as it should have been to start with. I put the restrictor back in the BCS and boost is back to where it was before the downpipe install(spikes to 17 at low RPM/settles to 14-15psi). The problem is that now instead of just frying the tires in 1st gear, I am getting violent wheel hop. Seems to me that would be a sign of slightly less power meaning the 3" downpipe actually slowed the car down , but my theory could be wrong. Anyone know if this theory is correct?

 

[crankbender]

actually decreasing the restriction in the exhaust can make you have lower boost. The reason the boost is settling at any boost when you have it set higher is because the turbo can't flow any more air, and that is where the air in and out is equal. decreasing your restrictions in your exhaust just upped your CFM out but not your CFM in. To balance this out physics lowers your boost pressure so that the CFM in and CFM out is equal again. you had the same power cause you are using the same ammount of air...you are just keeping less of the used gasses in the cylinder each time it exhausts.

 

[cmc]

You need a catback!