My friend is running a really short open downpipe setup. It's about 1 foot long from the turbine to the end of the downpipe. The O2 sensor sits midway. Would this effect the power? When the turbo (T3/T4 57 Trim) kicks in, I don't really feel the power. He's only pushing .6 Bar

And my other friend who ran no downpipe (to drive to a shop to get the downpipe made), his turbo wouldn't spool up at all.

How long should the length of the downpipe be at least? Thanks.

 

the downpipe has to be able to create some backpressure in order for the turbo to spool....if there isnt any...then like that situation ur friend was in happens...no spool....open downpipe can be effective but it needs to be done right...you need to be able to have the exhaust flow in order for it to suck it out of the engine.....with no backpressure its difficult to do that

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Evanmb44 &raquo;</TD></TR><TR><TD CLASS="quote">the downpipe has to be able to create some backpressure in order for the turbo to spool....if there isnt any...then like that situation ur friend was in happens...no spool....open downpipe can be effective but it needs to be done right...you need to be able to have the exhaust flow in order for it to suck it out of the engine.....with no backpressure its difficult to do that</TD></TR></TABLE>



Turbos spool due to two things: 1) Pressure difference between the manifold side and the exhaust side of the turbine, 2) Exhaust energy pumped at the turbo. Log style manifolds base power production on pressure differential in point 1, equal length manifolds base power production on efficiently utilizing exhaust energy as in point 2... though of course equal-length still have a pressure differential as well.

That being said I have no idea why the things aren't spooling that well, though I do know that having too short of a downpipe can actually cause more pressure than it alleviates due to turbulence at the turbine exit. But they both should still spool nicely. Like Mr. Bell said, the best turbo exhaust is the least exhaust.

Weird.

 

no exhaust = most power so.....id say both you friends have some mechanical probs

turbos need backpressure? um no.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turbo E 604 &raquo;</TD></TR><TR><TD CLASS="quote">no exhaust = most power so.....id say both you friends have some mechanical probs

turbos need backpressure? um no.</TD></TR></TABLE>



The best exhaust for turbo cars is no exhaust

he may be running way too much timing or his A/F's are way off becuase of the short DP. Either way if it doesn't feel right something maybe wrong in the tunning or motor

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TurboSmart &raquo;</TD></TR><TR><TD CLASS="quote">My friend is running a really short open downpipe setup. It's about 1 foot long from the turbine to the end of the downpipe. The O2 sensor sits midway. Would this effect the power? When the turbo (T3/T4 57 Trim) kicks in, I don't really feel the power. He's only pushing .6 Bar

And my other friend who ran no downpipe (to drive to a shop to get the downpipe made), his turbo wouldn't spool up at all.

How long should the length of the downpipe be at least? Thanks.</TD></TR></TABLE>

Assuming its a wideband and you're using it to tune the car, you're not going to get an accurate reading that way. Originally my sensor was about 3" from the end of my downpipe and I was reading very lean when I knew for sure the car was running rich. I went to Pep Boys and bought a bunch of mild steel elbows, connectors and clamps. The air/fuel ratio immediately dropped back down to ~12:1. Also, I've heard/seen different things, but some wideband manufacturers recommend placing the sensor as far down the downpipe as possible in order to maximize sensor life due to the heat near the exhaust housing.

 

Also if the downpipe exit doesn't go past the oil pan you might be heating up your oil alot.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by adseguy &raquo;</TD></TR><TR><TD CLASS="quote">The best exhaust for turbo cars is no exhaust</TD></TR></TABLE>

Damnit, You beat me to it..

 

OT but - It's weird how every couple weeks I see someone post that turbos need an exhaust to work. So many things are like this on H-T...