Turbo Manifold - Is bigger better?
12-13-2004, 09:09 AM
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Turbo Manifold - Is bigger better?
I'm just getting ready to fabricate a new stainless steel Turbo manifold and was wondering which size fittings / tube to use. I've decided to build a "Ram Horn" (I hope that's the right name). If you look at a Stone Mountain racing manifold (mandrel bent equidistant) the runners seem to be approximatly 1.25" in size / diameter. Other manifolds like the ram horn look to be around 1.5" (or bigger). Which is better? I've seen a stone mountain manifold in action and it spooled the turbo pretty darn quick. Keeping in mind that the design of a manifold, as well as the quality of the fabrication, can influence the spool times, if I use 1.5" fittings will there be a noticable difference in Turbo Lag due to the increased size / volume of the runners? Is there really any benefit to going bigger? The force on the exhaust wheel won't change (that's my theory anyway), just the volume in the maniold (the flow will have to restrict to enter the turbo housing anyway). Is there any benefit to increase volume and is it worth the extra time to fill the runners? 
12-13-2004, 10:42 AM
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Re: Turbo Manifold - Is bigger better? (Islandspeed)
I've wondered this myself....
I believe the smaller diameter runners will help to maintain or speed up the velocity of the exhaust gases. If you go larger than you exhaust ports, you may run into a little inefficiency due to the gases slowing down in the manifold then speeding up within the turbine housing, then slowing down after they exit the turbine.
I'd say build both sizes and let us know how they work!
I believe the smaller diameter runners will help to maintain or speed up the velocity of the exhaust gases. If you go larger than you exhaust ports, you may run into a little inefficiency due to the gases slowing down in the manifold then speeding up within the turbine housing, then slowing down after they exit the turbine.
I'd say build both sizes and let us know how they work!
12-13-2004, 11:24 AM
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Re: Turbo Manifold - Is bigger better? (fknslmd)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fknslmd »</TD></TR><TR><TD CLASS="quote">i built one recently and i used 1.5" stainless piping. it worked out good for me.</TD></TR></TABLE>
How much boost were you running and what RPM were you at when fully spooled?
How much boost were you running and what RPM were you at when fully spooled?
12-13-2004, 11:30 AM
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Re: Turbo Manifold - Is bigger better? (stizzit)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by stizzit »</TD></TR><TR><TD CLASS="quote">I've wondered this myself....
I believe the smaller diameter runners will help to maintain or speed up the velocity of the exhaust gases. If you go larger than you exhaust ports, you may run into a little inefficiency due to the gases slowing down in the manifold then speeding up within the turbine housing, then slowing down after they exit the turbine.
I'd say build both sizes and let us know how they work! </TD></TR></TABLE>
Thought of that...... I don't think that I'll get a chance to do both before next spring unfortunatly so I was kind of trying to avoid reinventing the wheel so-to-speak. I was thinking along the same lines you were with respect to the bigger diameter runners and the flow slowing down then speeding up. I could be completely wrong though and it mey be the best thing since sliced bread. It's not really my area of expertise.
I believe the smaller diameter runners will help to maintain or speed up the velocity of the exhaust gases. If you go larger than you exhaust ports, you may run into a little inefficiency due to the gases slowing down in the manifold then speeding up within the turbine housing, then slowing down after they exit the turbine.
I'd say build both sizes and let us know how they work!
</TD></TR></TABLE>Thought of that...... I don't think that I'll get a chance to do both before next spring unfortunatly so I was kind of trying to avoid reinventing the wheel so-to-speak. I was thinking along the same lines you were with respect to the bigger diameter runners and the flow slowing down then speeding up. I could be completely wrong though and it mey be the best thing since sliced bread. It's not really my area of expertise.
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