Opening the dump pipe?

[chadly]

I turned my boost up to 17/18psi last night doing some testing on the way to the track. When I got there I opened up the exhaust and made my first run. I saw the boost climb and hold at 21/22psi. Does opening the exhaust cause the boost to climb?

Thanks Chad

 

[t3intercooled]

yes it does cause the boost to climb. opening the exhaust gets rid of all the flow extrictors such as the muffler, cat, etc. You will always be faster and have more boost with the dump open...I suggest alky....that way you'll be safe

 

[chadly]

Alky is defiantly on the wish list.

I noticed that when I capped it off and drove home it dropped back down.

Thanks.

 

[Jerryl]

Here is a good read.
http://www.turbobuick.com/forums/ge...-dump-pipe-there-realy-gains-look-inside.html

 

[chadly]

Thanks, that is an interesting read. I really wanted to make a couple passes with the exhaust capped, but ran out of time. Each car would be different, but it would be fun to try full exhaust at a set 15psi boost and establish an ET. Then uncapp it, turn boost down to 15psi and establish some more ET's. I would think you would get faster spool uncapped. It would also show how restrictive your exhaust is.

 

[johnnyttype]

i guess my exhaust isnt very restrictive because my boost at most went up about .5psi. of course i dont have a converter and 3" torque tech duals outback with two 3" 2 chamber flowmasters! ET wise i gained .020 sec in the 1/4 with the dump open compared to closed!

 

[bison]

With the first car listed in my sig on an older build it had a $hitty flow master exhaust that would restrict the hell out of it. Opening the exhaust it spooled over twice as fast and it went 6-7 psi higher on the same tune and settings . Fortunately i was ready for this knowing the exhaust was a POS.

 

[bison]

Thanks, that is an interesting read. I really wanted to make a couple passes with the exhaust capped, but ran out of time. Each car would be different, but it would be fun to try full exhaust at a set 15psi boost and establish an ET. Then uncapp it, turn boost down to 15psi and establish some more ET's. I would think you would get faster spool uncapped. It would also show how restrictive your exhaust is.

You will need to adjust the fueling with each setting or it will go lean or rich depending on which way you went open or closed. Your thoughts are correct. But if its a stock ecm car i would set it rich and get into it easy. No need to melt it from un-planned overboost.

 

[johnnyttype]

With the first car listed in my sig on an older build it had a $hitty flow master exhaust that would restrict the hell out of it. Opening the exhaust it spooled over twice as fast and it went 6-7 psi higher on the same tune and settings . Fortunately i was ready for this knowing the exhaust was a POS.

was that one of the 2 1/4" or 1/2" flowmaster kits u see in the summit catalog? single muffler crap? i can see just looking at that kit its pretty bad! and for a flowmaster it doesnt sound to good to me either. my kit, given its not flowmaster, just the mufflers r, and i know im am very biased in that it is my personel car, is one of the best sounding 3.8L i have ever heard through the exhaust:smile:

i know alot of people dont like flowmasters for their buicks but like i said earlier, my car saw no gains by opening the dump... the .020 sec came on the 60ft time.

 

[bison]

was that one of the 2 1/4" or 1/2" flowmaster kits u see in the summit catalog? single muffler crap? i can see just looking at that kit its pretty bad! and for a flowmaster it doesnt sound to good to me either. my kit, given its not flowmaster, just the mufflers r, and i know im am very biased in that it is my personel car, is one of the best sounding 3.8L i have ever heard through the exhaust:smile:

i know alot of people dont like flowmasters for their buicks but like i said earlier, my car saw no gains by opening the dump... the .020 sec came on the 60ft time.

Its a custom single 3" that was on the car when i bought it. The car was capable of 130 mph passes. I had a dual 3 inch back in the mid 90's that didnt get any better opened on a 12.0 car but it was heavy as hell. It was a good sounding car. Better than any ive had. Even the custom 3" single sounds good. Its just restrictive as hell.