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cutouts

Post  quick 52 on November 8th 2013, 2:37 pm

will it matter if I install cutout down stream and not up next to the header just don't have room unless I do a complete rework of the ex. frame rail are only 32" wide so not a lot of room can install about the tailshaft of the trans...

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Re: cutouts

Post  kim on November 8th 2013, 2:52 pm

As long as its before the muffler, the gain/loss is pretty similar. Big benefit to you, the further back, the less noise you get to put up with.

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Re: cutouts

Post  LivermoreDave on November 8th 2013, 3:49 pm

As Kim wrote, a factor I would consider is the noise level inside the car as well fumes. When you install the cut-outs, can you install the cut-out/cut-out opening in line with the exhaust pipe and then relocate the exhaust pipe that continues toward the muffler off the side of the cut-out? What I'm trying to say is make the cut-out functional and provide performance instead of just noise. Back in the '60's we installed cut-outs on our cars and we thought they provide performance. Now days I look back at how they were installed and they only created noise not to mention a pain in the ass to get uncapped!

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Re: cutouts

Post  kim on November 8th 2013, 6:53 pm

Mainly because the engines were cam'ed to deal with the restrictive exhaust, I think the cut outs, 45 to 90 degree off of straight pipe served the purpose, but we never cammed the engine to perform with the open exhaust, all we did was bleed cylinder pressure.

I don't think there is probably 10HP difference in making the cut out the straight vent and the muffler the angled adapted piece or the other way around, as soon as the pulse pressure begins to back up in the pipe, its like water in creek, the flow of least resistance is where it will go. So if the cut out is open, its going to dump there.

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Re: cutouts

Post  LivermoreDave on November 9th 2013, 10:12 am

kim wrote:I don't think there is probably 10HP difference in making the cut out the straight vent and the muffler the angled adapted piece or the other way around, as soon as the pulse pressure begins to back up in the pipe, its like water in creek, the flow of least resistance is where it will go.  So if the cut out is open, its going to dump there.
That's an interesting statement Kim although I have a question if I may? At the point of or path of least resistance (water in the creek), does it not require more pressure to take the path of least resistance since resistance is now present? If more energy is required to redirect the flow of exhaust now that resistance is present does the so-called back pressure increase in the exhaust before the exit provided by the cut-out? Back a few years ago when NHRA Stockers were required to use complete stock exhaust systems (no tube headers) the cars I inspected had the exhaust outlet (opening) in-line with the exhaust pipe shortly after the turn from engine compartment toward the muffler. The exhaust pipe that continued to the muffler was attached on the side of the exhaust pipe which allowed a straight exit for the exhaust from the exhaust manifold/exhaust pipe configuration. It must have been worth something!

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Re: cutouts

Post  kim on November 9th 2013, 10:40 am

Someone sure thought it was, the X and H pipe argument, in reality so long as the pressure has some where to go, I don't believe there is a huge difference if it dumps across an H, or if it splits at an X,  same kind of thing for the cut out.  When the straight through flow hits the resistance of a baffled muffler, its going to dump out the side cut out, the resistance acts as the wall of the pipe and laminar flow is out the cut out.  Straight through, I'm sure even then there is enough volume in the pipe that there were exhaust gases that hit the restriction of the muffler.

Kind of like the years Warren Johnson showed up with cardboard taped around his intakes. Everyone was so worried about some intake secret, they never looked at obvious things for his HP advantage, like carburetors that had been worked with bigger bores, throttle bodies etc.... If everyone is looking at the quick cars exhaust cut out, no-ones looking at the suspension reaction, weight shift, etc......

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Re: cutouts

Post  GT300TD on November 9th 2013, 1:57 pm

I posed this question on the 'other' forum in a 'crossover thread' and haven't received an answer yet, so i'll ask it here.
I want to install an H pipe crossover for extra torque, and the best place 'room wise' is in front of my cutouts. I have full length Crite's headers and 18" x 3 1/2" extensions and installed my cutouts the old school "install them where the crayon mark starts to burn off" method. The 3" cutouts start 10" & 10 1/2" back from where my collectors bolt to my extentions. They are angled back about 45* and down slightly on the outside of the extentions. The extentions go into 3 1/2" to 3" reducers then welded to a set of 3" chambered mufflers. I have very little room to install the "H" pipe crossover between the back of the cutout and the muffler and it would be pretty close to the back of my cutout.
What say you men of knowledge Question .


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Re: cutouts

Post  kim on November 9th 2013, 2:57 pm

I think the cut outs are a little far back for optimum performance, but doing much more than trying to run through the mufflers. Putting the H pipe engine side of the cutout is fine, that's where you want it to balance the exhaust pulse and or scavenge off the other header. The further back you go, the cooler the exhaust, the greater the reduction in volume and velocity. So the further back you go, the more "pressure" the cylinder is subject to. Depending on cam selection with reguards to exhaust events, free flow can hurt some combinations. IF it was cammed for open headers, free flow exhaust, then everything you can do to get rid of pressure, is a win.

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Re: cutouts

Post  GT300TD on November 9th 2013, 3:52 pm

Kim,
My first build so I didn't consider the fine points. 4420# (with me in it). GalaxieXL, 11 to 1 466/C6, 3.89 rear end.
Cam is a Crower 22207 hyd flat tappet, 244/251@.050 dur.,540/541 lift, 108* lobe sep.
Intake opens:   18.0 BTDC, closes: 46.0 ABDC
Exhaust opens: 58.0 BBDC, closes: 14.0 ATDC
Lobe lift: Int 0.312, Exh 0.313
How far back from the collector should I put the crossover? I'm planning on a 3" crossover into the 3 1/2" extentions.???


Last edited by GT300TD on November 10th 2013, 11:33 am; edited 1 time in total

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Re: cutouts

Post  LivermoreDave on November 9th 2013, 10:40 pm

Although the example I provide may be a bit exaggerated, I believe the theory or actions are similar. The video is about 8 minutes long. The areas I call to attention are at the 5:20 and 7:45 marks. The volume of water can not flow freely through the bridge's opening because the opening is being restricted. Watch the water as it attempts to pass into and through the opening. It bellows back out or up stream. Now I know your thinking very little if any. Look at the bridge, there is no restriction upward or in a near 180 degree plane to the stream. The water continues to force water in the direction of the bridge only to have water return up stream by several feet. Now let's fit all this in a tube. There is no relief of back pressure or exhaust gases up stream until the cut-out. In an effort to move toward the muffler a restriction is now present at least to the cut-out or does the restriction move up stream past the cut-out to create back pressure because the back pressure is fighting the exhaust for the space the cut-out is offering! I continue to believe if a cut-out is fabricated in the exhaust pipe it should be in-line with the exhaust flow instead of presenting an angle for the exhaust to exit.

As to the H-pipe and X-pipe, they offer near the same effects. Their intentions are to scavenge exhaust pulses from the weak side. The X-pipe simply is a modern design and may quieten the exhaust tone more than the H-pipe.

Sly engine masters always have a card up their sleeve when operating in public. Like the recent display at 2013 EMC show.


https://www.youtube.com/watch?v=Tiilnigt828

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Re: cutouts

Post  GT300TD on November 10th 2013, 11:19 am

Interesting example, I tend to think that a straight flow is better than a cutout also. I've read that header extentions improve torque over the collectors alone, but can hurt you if they are too long and depend on cam specs, compression, etc. Mine is a street car with limited trips to the strip (1/8 mile), I drive it about 60 miles one way to the strip. If I could justify buying a trailer I would remove the exhaust and experiment with the different length extentions, but for my situation I have to run the cutouts. The car seems to lack low end torque, I'm running a 2800-3200rpm torque convertor, a 3000 rpm was recommmended by Crower for my type of driving. I run 295/55/15 ET Streets and can barely turn over the tires with 3.89 gears. It does launch very well though Smile .
Thanks Dave and Kim Cool .

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Re: cutouts

Post  quick 52 on November 10th 2013, 6:05 pm

Was out in the shop pulling the trans and looking at the EX. think I will put the cutouts after the H pipe

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Re: cutouts

Post  GT300TD on November 10th 2013, 10:29 pm

Looked under the Gal earlier and I'm screwed...My exhaust system is tucked up so only half of my pipes are below the bottom of my trans and trans cross member. The crossover would be too close to the ground if I ran them under the trans. My cutouts are even with the back of my cross member Evil or Very Mad  Rolling Eyes . Oh well.


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Re: cutouts

Post  quick 52 on November 11th 2013, 12:01 am

Ill take some pics of what I have

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Re: cutouts

Post  LivermoreDave on November 11th 2013, 9:10 am

quick 52 wrote:Was out in the shop pulling the trans and looking at the EX. think I will put the cutouts after the H pipe
I like that approach. As we've discussed the X or H pipe configuration may offer an advantage, including that in our search for performance seems a smart idea!

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Re: cutouts

Post  LivermoreDave on November 20th 2013, 2:06 pm

Just another opinion and description of our discussion's pro's and con's.

Dave.



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Re: cutouts

Post  supervel45 on November 25th 2013, 4:28 am

Take this with a grain of salt. On a tuned pipe I have heard they used to paint the pipe, make a full load pass, and where the paint stopped burning off, was the optimun lenght, to cut the pipe. Drag strip time slips, are the only sure way to verify, that I know of. Un capped mild street cars are usually pigs in my experience.

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