dumptubes: re-routing vs. open
07-05-2007, 03:15 AM
#41
0.0 BAR
Join Date: Jan 2006
Posts: 34
Re: dumptubes: re-routing vs. open
Please read this entire thing if you care about your tune.
someone please tell me how an open wastegate is different from a pre-turbo / pre-o2 sensor exhaust leak.
this is hmt. is anybody else with me here?
a wategate opening is no different to a turbo than an exhaust leak. it's just that one is a controlled leak, and one isn't. a good wastegate only leaks out what you set it to leak out, to control power. an uncontrolled exhaust leak on the other hand, releases more exhaust than the wastegate already is, after AND before it's opened. therefore, exhaust leaks will slow turbo spoolup, and alter o2 sensor readings, further reducing power, right? please tell me why an open dumptube wouldn't do the same thing.
i can understand how you guys think that you want the o2 sensor to only read what the turbo has already seen, but guess what made those other dumptube gases. that same turbo pumping air into the cylinders. when you run an open dumptube, you're not reading everything that's getting dumped out of the exhaust ports. some of it is going out of your open dumptubes, and some of it is spooling up your turbo, and then going into your o2 sensored downpipe. a wastegate's only purpose is to let exhaust gases bypass the turbine housing, not the rest of the exhaust system entirely. an o2 sensor still wants to see those gases after the turbo, wideband OR narrowband.
physics: you can't have two things in the same place at the same time. sooooo... the exhaust gases coming out of the wastegate aren't the same gases coming out of the turbo.
i know open wastegates sound cool, and are easier to fabricate than a recirc setup, and i know they work. hell, we all do. that's what everyone else runs. but you're sacrificing tuning accuracy at high loads when the wastegate's open.
^^This is exactly what I'm talking about! Real experience of WTF I'm talking about!
happy 4th, noglets! *drunknhigh*
someone please tell me how an open wastegate is different from a pre-turbo / pre-o2 sensor exhaust leak.
this is hmt. is anybody else with me here?
a wategate opening is no different to a turbo than an exhaust leak. it's just that one is a controlled leak, and one isn't. a good wastegate only leaks out what you set it to leak out, to control power. an uncontrolled exhaust leak on the other hand, releases more exhaust than the wastegate already is, after AND before it's opened. therefore, exhaust leaks will slow turbo spoolup, and alter o2 sensor readings, further reducing power, right? please tell me why an open dumptube wouldn't do the same thing.
i can understand how you guys think that you want the o2 sensor to only read what the turbo has already seen, but guess what made those other dumptube gases. that same turbo pumping air into the cylinders. when you run an open dumptube, you're not reading everything that's getting dumped out of the exhaust ports. some of it is going out of your open dumptubes, and some of it is spooling up your turbo, and then going into your o2 sensored downpipe. a wastegate's only purpose is to let exhaust gases bypass the turbine housing, not the rest of the exhaust system entirely. an o2 sensor still wants to see those gases after the turbo, wideband OR narrowband.
physics: you can't have two things in the same place at the same time. sooooo... the exhaust gases coming out of the wastegate aren't the same gases coming out of the turbo.
i know open wastegates sound cool, and are easier to fabricate than a recirc setup, and i know they work. hell, we all do. that's what everyone else runs. but you're sacrificing tuning accuracy at high loads when the wastegate's open.
Originally Posted by rexsk8er
gen4acclude got my point. i dyno'd my car with an open dump, and i was lean in boost after the w/g opend. so i retuned and the car ran like ----. i put it back to the basemap, after my last pull and i made best power, so i kept it there and babyed it back home. so than i made up a tempory dp with the wg rerouted into the exhuast and i was in the 11's @ wot when the dyno wbo2 was shoing mid 13's. basically i had a good tune, but my afrs were thrown off because the dyno wbo2 didnt see the exhuast from the open w/g
happy 4th, noglets! *drunknhigh*
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