Cutouts, is 2 better or just 1?
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TECH Junkie
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From: Burleson/Ftw,Texas
Cutouts, is 2 better or just 1? I was wondering which would give me the most gain? should I do 2 or 1? If I do one i was gonna go after my Y-pipe, but if I do 2 i was gonna go after my headers. Which is better? See sig for my mods 
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From: Miami
One in the I pipe is sufficient.
2 work fine also. It's a matter of choice/ loudness.
I tend to think that if you have a good merge collector at the Y-pipe, one cutout in the I pipe is the way to go.
2 work fine also. It's a matter of choice/ loudness.
I tend to think that if you have a good merge collector at the Y-pipe, one cutout in the I pipe is the way to go.
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TECH Junkie
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From: Burleson/Ftw,Texas
Well im using a Hooker offroad pipe, I think its 3". I was just wondering if i would loose TQ but gain HP using a dual system or would I see a gain across the board?
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TECH Senior Member
Joined: Nov 2001
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From: Troy, AL
Folks, it really has little to do with whether you have one opening or two. It's the amount of flow that counts most (and to a much smaller degree the amount of surface friction the gasses encounter.)
A couple of examples for you...
Two 2.5" pipes will flow 940 cfm at a velocity of 230 ft/min.
One 3.5" pipe will flow about the same at 922 cfm at the same velocity.
One 4" pipe will flow 1204 cfm at 230 ft/min.
Two 2" pipes will only flow 602 cfm at " ". That's right, they flow HALF what one 4" pipe flows!
So, you could use dual 2.5"s or one 3.5" pipe. The flow will be roughly the same. The above examples were not taking into consideration flow losses to friction. If you take that into consideration, I believe the single 3.5" pipe will outflow the dual 2.5"s by a slim margin in the lengths that are most likely to be used (see, frictional losses grow as pipe length increases.) A single pipe has significantly less wall surface area than dual pipes that that together have an equal cross sectional area to the single pipe. In other words, the two pipes, because there is more more wall for the air to rub against, will have greater losses to friction than the single, but otherwise equal, pipe.
Hope this helps.
A couple of examples for you...
Two 2.5" pipes will flow 940 cfm at a velocity of 230 ft/min.
One 3.5" pipe will flow about the same at 922 cfm at the same velocity.
One 4" pipe will flow 1204 cfm at 230 ft/min.
Two 2" pipes will only flow 602 cfm at " ". That's right, they flow HALF what one 4" pipe flows!
So, you could use dual 2.5"s or one 3.5" pipe. The flow will be roughly the same. The above examples were not taking into consideration flow losses to friction. If you take that into consideration, I believe the single 3.5" pipe will outflow the dual 2.5"s by a slim margin in the lengths that are most likely to be used (see, frictional losses grow as pipe length increases.) A single pipe has significantly less wall surface area than dual pipes that that together have an equal cross sectional area to the single pipe. In other words, the two pipes, because there is more more wall for the air to rub against, will have greater losses to friction than the single, but otherwise equal, pipe.
Hope this helps.
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i did two in the ypipe for a couple reasons
1) sound: it sounds so much better open when you have them behind the headers rather than the ipipe
2) as colonel said, friction: the more pipe the gases have to travel through, the more friction. going through the bends in the ypipe and the crappy collectors that come on most ypipes will definately slow things down
3) this post by QTP
heres my setup
1) sound: it sounds so much better open when you have them behind the headers rather than the ipipe
2) as colonel said, friction: the more pipe the gases have to travel through, the more friction. going through the bends in the ypipe and the crappy collectors that come on most ypipes will definately slow things down
3) this post by QTP
We have some results for you guys. This is on Pauls WS6. Untouched motor. Mods are:
Lid/Filter
Ported TB
QTP Headers
QTP Dual QTEC Y Pipe
QTEC in I Pipe
This was on Carteks Dyno
1 Cutout Open
339.7hp/355.1TQ
2 Cutouts Open
345HP/358.4TQ
I have to scan the dyno sheet in but there is NO loss of torque down low or anywhere else. Gains across the board.
I have to get my car on the dyno to see how heads/cam car reacts to 1vs2
Lid/Filter
Ported TB
QTP Headers
QTP Dual QTEC Y Pipe
QTEC in I Pipe
This was on Carteks Dyno
1 Cutout Open
339.7hp/355.1TQ
2 Cutouts Open
345HP/358.4TQ
I have to scan the dyno sheet in but there is NO loss of torque down low or anywhere else. Gains across the board.
I have to get my car on the dyno to see how heads/cam car reacts to 1vs2
TECH Senior Member
Joined: Nov 2001
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From: Troy, AL
On point #2. It is important to only use mandrel bent tubing and a 1st rate collector like the Flowmaster collectors when using a Y-pipe.
And like we've both pointed out, pipe length effects frictional losses, though these are generally somewhat small with mandrel bent tubing and at the lengths we're talking about. But every little bit counts!
On my racecar I run open headers. Less weight, less frictional losses, sounds mean as hell.
And like we've both pointed out, pipe length effects frictional losses, though these are generally somewhat small with mandrel bent tubing and at the lengths we're talking about. But every little bit counts!
On my racecar I run open headers. Less weight, less frictional losses, sounds mean as hell.
