3.8 L L67 SC V6 Overboost?

[Farmallxjcraig]

I just got done doing an upper and lower intake gasket, opened up my stock air box and cut out the U bend out of the exhaust on my regal gs. Other than that it’s completely stock. I have recently started seeing boost spikes above 10 lbs in third gear. Is that normal? I don’t remember seeing boost that high until I added the 3.4 blower on my last supercharged 3800.

 

3.3 L LG7 V6  Tach install 3300 LG7

3.8 L L67 SC V6  INTENSE Racing 3.8 Liter cam specs

[Jasmindont]

I just got done doing an upper and lower intake gasket, opened up my stock air box and cut out the U bend out of the exhaust on my regal gs. Other than that it’s completely stock. I have recently started seeing boost spikes above 10 lbs in third gear. Is that normal? I don’t remember seeing boost that high until I added the 3.4 blower on my last supercharged 3800.

A boost spike is normal sometimes.

 

[dragonack]

I just got done doing an upper and lower intake gasket, opened up my stock air box and cut out the U bend out of the exhaust on my regal gs. Other than that it’s completely stock. I have recently started seeing boost spikes above 10 lbs in third gear. Is that normal? I don’t remember seeing boost that high until I added the 3.4 blower on my last supercharged 3800.

So let's start with boost here. Basically it's in a way a measurement of restriction. There are a ton of factors that can affect those numbers. Weather conditions, the flow of the engine, how high your RPM is set to and others. For example when I had my 97 back in the day I would often see 9 to 10 lb of boost just like you. Today with the same engine but in a 98 body and mods with a 3.4 pulley I usually see around that same boost but I'm moving more air at the same time. So in essence I wouldn't worry too much.

 

[ThatSlow.W204]

So let's start with boost here. Basically it's in a way a measurement of restriction. There are a ton of factors that can affect those numbers. Weather conditions, the flow of the engine, how high your RPM is set to and others. For example when I had my 97 back in the day I would often see 9 to 10 lb of boost just like you. Today with the same engine but in a 98 body and mods with a 3.4 pulley I usually see around that same boost but I'm moving more air at the same time. So in essence I wouldn't worry too much.

Very well said. Many factors can effect it.

 

[Last Indian]

I’ll say it again 3800’s are sensitive to back pressure due to their unique design. More so than their big brother, but that back pressure helps make the power you love. That’s what you see in higher boost pressure, as dragonack indicated.

 

[Farmallxjcraig]

I’ll say it again 3800’s are sensitive to back pressure due to their unique design. More so than their big brother, but that back pressure helps make the power you love. That’s what you see in higher boost pressure, as dragonack indicated.

I know that the back pressure is what is causing the boost. I didn’t remember seeing the boost go over 8.5 before I removed the u bend and the resonator. It seemed strange that I theoretically removed restriction but it almost acts like I added some. I am going to order some mandrel exhaust pieces to build a better down pipe and get rid of the small tail pipe.

 

[RegalRacer]

Farmall if you remember the factory downpipe is worse off then just a regular u bend section the actual pipe is double walled and as small as 2.25 inch some places internally, is it possible you removed the u bend and have developed a almost scavenging effect that can be caused by the open second section of pipe inside the downpipe? Like the air is almost reversing direction up the pipe towards the top due to velocity inside? If you removed that u bend you could be looking at resonator restrictions next or possibly even muffler issues depending upon your current exhaust conditions?