Re: Ported Stockers Revisited
Quote:
Originally Posted by
Shadow
I haven't looked at individual cyl's, always Thought I was so close to an EQ length header swap that it wouldn't be worth it. lol
It's important to keep the turbine housing scroll Close in mind while thinking this through. The expanding gasses will have to Compress again while they Squeeze through that restriction!
It's prob harder for most to visualize because the #3 & 4 runners are so short. Imagine instead an eq length header with 2 runners 1.5" ID and 2 runners 1.68" ID going into a .63 A/R stage 1 turbine housing/ wheel.
Which 2 cyl's are going to outflow the other 2?
Right, so the 1.5" runners will not be able to move the same maximum cfm, but that's not the point. What you are wanting is the pressure that is seen at the exhaust valve head to be the same across all of the cylinders. Because the cross sectional area is smaller, the same amount of mass flowing through is will have to move faster, which equates to less pressure at the valve head (PV=nRT) because the mass isn't stacking up. The larger runners allow the mass to slow down and stack up, causing a higher net pressure and a slower flow. So yes, by mucking with the volumes of the runners you should be able to effectively produce similar pressures at the valve heads as an equal length tubular header that all the runners were the same cross sectional diameter.
As for how the mass moves through the volute and turbine, honestly I really want to do more in depth research here, but the only reason that the exhaust would have to compress again in the housing is if the housing/wheel combo simply couldn't flow the amount of exhaust being passed through it (boost creep). There's a bunch of physics going on all at the same time. The turbine works off of pressure and temperature (to a smaller extent) differential. The volume of the volute does decrease, but it's done so that the decreasing volume of exhaust keeps the same pressure differential around the turbine wheel. I guess you could argue this is "compressing", but the actual pressure theoretically should be the same all the way around.
Re: Ported Stockers Revisited
Quote:
Originally Posted by
Reaper1
Right, so the 1.5" runners will not be able to move the same maximum cfm, but that's not the point. What you are wanting is the pressure that is seen at the exhaust valve head to be the same across all of the cylinders. Because the cross sectional area is smaller, the same amount of mass flowing through is will have to move faster, which equates to less pressure at the valve head (PV=nRT) because the mass isn't stacking up. The larger runners allow the mass to slow down and stack up, causing a higher net pressure and a slower flow. So yes, by mucking with the volumes of the runners you should be able to effectively produce similar pressures at the valve heads as an equal length tubular header that all the runners were the same cross sectional diameter.
As for how the mass moves through the volute and turbine, honestly I really want to do more in depth research here, but the only reason that the exhaust would have to compress again in the housing is if the housing/wheel combo simply couldn't flow the amount of exhaust being passed through it (boost creep). There's a bunch of physics going on all at the same time. The turbine works off of pressure and temperature (to a smaller extent) differential. The volume of the volute does decrease, but it's done so that the decreasing volume of exhaust keeps the same pressure differential around the turbine wheel. I guess you could argue this is "compressing", but the actual pressure theoretically should be the same all the way around.
If I'm understanding you correctly, you're in agreeance with Rob that opening 3 and 4 but leaving 1 and 2 alone will help balance out the flow?
Re: Ported Stockers Revisited
Quote:
Originally Posted by
Reaper1
Right, so the 1.5" runners will not be able to move the same maximum cfm, but that's not the point. What you are wanting is the pressure that is seen at the exhaust valve head to be the same across all of the cylinders. Because the cross sectional area is smaller, the same amount of mass flowing through is will have to move faster, which equates to less pressure at the valve head (PV=nRT) because the mass isn't stacking up. The larger runners allow the mass to slow down and stack up, causing a higher net pressure and a slower flow. So yes, by mucking with the volumes of the runners you should be able to effectively produce similar pressures at the valve heads as an equal length tubular header that all the runners were the same cross sectional diameter.
As for how the mass moves through the volute and turbine, honestly I really want to do more in depth research here, but the only reason that the exhaust would have to compress again in the housing is if the housing/wheel combo simply couldn't flow the amount of exhaust being passed through it (boost creep). There's a bunch of physics going on all at the same time. The turbine works off of pressure and temperature (to a smaller extent) differential. The volume of the volute does decrease, but it's done so that the decreasing volume of exhaust keeps the same pressure differential around the turbine wheel. I guess you could argue this is "compressing", but the actual pressure theoretically should be the same all the way around.
I prob shouldn't say "compressing" as much as accelerating through the turbine scroll, but with a system under pressure moving at an ever increasing rate into an ever decreasing scroll, I have to believe there is some form of compressing going on along with everything else.
Also very important to consider that the exhaust cross section needed to flow X will always be relative to the exhaust port size exiting the head. As many have observed, I Don't hog out the exhaust ports when porting one of these heads. Since my exhaust port exits are almost always going to be Smaller than the exhaust mani inlet, the chance of running out of cross sectional area to sufficiently flow Any amount of exhaust that is able to be produced by that size exhaust port become virtually Impossible..........
Damn, Did I just say that the ported stocker is Infinite!??? :lol:
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Quote:
Originally Posted by
cordes
If I'm understanding you correctly, you're in agreeance with Rob that opening 3 and 4 but leaving 1 and 2 alone will help balance out the flow?
Just for the record, I never said I leave 1 and 2 alone ;)
Re: Ported Stockers Revisited
Quote:
Originally Posted by
Shadow
I prob shouldn't say "compressing" as much as accelerating through the turbine scroll, but with a system under pressure moving at an ever increasing rate into an ever decreasing scroll, I have to believe there is some form of compressing going on along with everything else.
Also very important to consider that the exhaust cross section needed to flow X will always be relative to the exhaust port size exiting the head. As many have observed, I Don't hog out the exhaust ports when porting one of these heads. Since my exhaust port exits are almost always going to be Smaller than the exhaust mani inlet, the chance of running out of cross sectional area to sufficiently flow Any amount of exhaust that is able to be produced by that size exhaust port become virtually Impossible..........
Damn, Did I just say that the ported stocker is Infinite!??? :lol:
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Just for the record, I never said I leave 1 and 2 alone ;)
Could you speak to your process more? I guess when you said "clean" I took it as somewhat literal.
Re: Ported Stockers Revisited
Quote:
Originally Posted by
cordes
Could you speak to your process more? I guess when you said "clean" I took it as somewhat literal.
By the time you have removed all of the rough casting and any casting flash + radiused the corners, then smoothed out, you end up removing a fair amount of material. So you Are increasing the cross sectional area whether you like it or not, just not nearly as much as the 3 & 4 where you are doing a crap load of porting and Heavy removal before you get down to the smoothing process.
I know what the cross section of the #1 runner measures just after the turn, so I know what needs to happen on the flange inlet and around that turn in order to remove any restriction before it. By the time you've achieved what I described above, you are pretty much there.
Has no one else cut open an exhaust mani and measured all of the steps/turns/ openings in it? That was one of the first things I did, Years ago, and still have those cut apart pieces for quick reference any time I need them.
Re: Ported Stockers Revisited
Quote:
Originally Posted by
cordes
If I'm understanding you correctly, you're in agreeance with Rob that opening 3 and 4 but leaving 1 and 2 alone will help balance out the flow?
Basically, yes. By changing the cross sectional area of each runner the velocity (and therefore the pressure) could be altered to "simulate" an equal length header. The pulse tuning probably won't work, but that's not the goal.
Quote:
Originally Posted by
Shadow
I prob shouldn't say "compressing" as much as accelerating through the turbine scroll, but with a system under pressure moving at an ever increasing rate into an ever decreasing scroll, I have to believe there is some form of compressing going on along with everything else.
Also very important to consider that the exhaust cross section needed to flow X will always be relative to the exhaust port size exiting the head. As many have observed, I Don't hog out the exhaust ports when porting one of these heads. Since my exhaust port exits are almost always going to be Smaller than the exhaust mani inlet, the chance of running out of cross sectional area to sufficiently flow Any amount of exhaust that is able to be produced by that size exhaust port become virtually Impossible..........
Damn, Did I just say that the ported stocker is Infinite!??? :lol:
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Just for the record, I never said I leave 1 and 2 alone ;)
I understand what you're getting at. I need to re-read about volutes, etc.
If the exhaust port is always smaller than the manifold and the length of the runner isn't too long, yeah, the stocker *could* be "good enough" for every bit of power that the stock ports can support (meaning no welding, epoxy ,etc.). Of course, as you've said from the start, this doesn't mean that there wouldn't be gains from going with a well designed header, but unless the stocker just couldn't be modified any more, those gains will probably be small.
Quote:
Originally Posted by
Shadow
By the time you have removed all of the rough casting and any casting flash + radiused the corners, then smoothed out, you end up removing a fair amount of material. So you Are increasing the cross sectional area whether you like it or not, just not nearly as much as the 3 & 4 where you are doing a crap load of porting and Heavy removal before you get down to the smoothing process.
I know what the cross section of the #1 runner measures just after the turn, so I know what needs to happen on the flange inlet and around that turn in order to remove any restriction before it. By the time you've achieved what I described above, you are pretty much there.
Has no one else cut open an exhaust mani and measured all of the steps/turns/ openings in it? That was one of the first things I did, Years ago, and still have those cut apart pieces for quick reference any time I need them.
Back when the "twin turbo Shadow" was around (the one that had 2 Mitsu's mounted on the same manifold that was split and the swingvalves pointed at each other welded together), I remember the pictures if the manifold then. That's when *I* decided that the stock manifold was too much of a hassle to deal with for "good" performance.
Re: Ported Stockers Revisited
Thanks guys. This thread has been very enlightening. What's the thinnest you guys go on the castings without worrying about blowing through them when running the car?
Re: Ported Stockers Revisited
Quote:
Originally Posted by
Reaper1
If the exhaust port is always smaller than the manifold and the length of the runner isn't too long, yeah, the stocker *could* be "good enough" for every bit of power that the stock ports can support (meaning no welding, epoxy ,etc.). Of course, as you've said from the start, this doesn't mean that there wouldn't be gains from going with a well designed header, but unless the stocker just couldn't be modified any more, those gains will probably be small.
The gains from a properly designed Eq length header would be in Efficiency. The Efficiency of the exhaust moving Away from the port And, the Efficiency of the exhaust Pulse moving Through the turbine housing/wheel combo.
How much More efficient do I believe the Charger would be with a header right now? With no other change other than tuning the cal to match AFR's with the header, the Charger would prob be making the same power it is now on 32psi vs 39. May be slightly less, may be slightly more, but that's the kind of change you're going to see, More power (more Efficient) on less boost with the same turbo configuration.
Quote:
Originally Posted by
cordes
Thanks guys. This thread has been very enlightening. What's the thinnest you guys go on the castings without worrying about blowing through them when running the car?
I'm sure there are areas on the Charger exhaust mani that are .030", but I would usually stick to at least double that in all other applications.
Also keep in mind that we are only talking about certain areas, not a whole runner that thin.
Re: Ported Stockers Revisited
Quote:
Originally Posted by
Shadow
The gains from a properly designed Eq length header would be in Efficiency. The Efficiency of the exhaust moving Away from the port And, the Efficiency of the exhaust Pulse moving Through the turbine housing/wheel combo.
How much More efficient do I believe the Charger would be with a header right now? With no other change other than tuning the cal to match AFR's with the header, the Charger would prob be making the same power it is now on 32psi vs 39. May be slightly less, may be slightly more, but that's the kind of change you're going to see, More power (more Efficient) on less boost with the same turbo configuration.
I'm sure there are areas on the Charger exhaust mani that are .030", but I would usually stick to at least double that in all other applications.
Also keep in mind that we are only talking about certain areas, not a whole runner that thin.
Wow, that's a huge decrease in boost for the same power. Very interesting to think about.
I appreciate the advice on the thickness. I've never researched what the minimum recommended is.
Re: Ported Stockers Revisited
I would suspect header tube length would have some impact on output to
of maybe where the power is in the power band
I have a set of extended big block headers .. great for bottom end , not so great for top end
by extended length I mean about 20 inches at the collectors
Re: Ported Stockers Revisited
When I port a stocker I try to build a decompression area, like a plenum behind the #3 hole. Under pressure you aren't making 3 flow a ton better than 1. What you are doing is the same thing as making a path of least resistance for 1. If you work 1-2 and leave 3 alone you are creating a bottle neck. When you really work 3 you make a low velocity decompression area for 1-2 to fall into before the turbo. Then the volume area, not a separate port decompress into the turbine. Kind of like a step header to a collector if you will
Re: Ported Stockers Revisited
I hope to have some feedback on this in a few weeks. Of course, I'm changing a bunch of stuff at once to make this experiment invalid, but I did attempt to spend a lot more time on 3 and 4 than 1 and 2. It was ported a lot more heavily than I had initially intended, but I'm a big fan of my die grinder and have been working away on stuff over the winter. I think I'll try a head soon. I'm surprised at how good I am with it. It's a lot like my days of grinding tires when patching flats.
Thanks to all who've offered advice in this thread. It was a huge help.
Re: Ported Stockers Revisited
Good question but mine is has anyone actually gone too far and broken through while porting??
My pal Brian ported one for me very nicely but broke through in one spot.
Looking for input on welding up the small hole.
Any experienced input is appreciated!!
Thanks
Randy
Quote:
Originally Posted by
cordes
Thanks guys. This thread has been very enlightening. What's the thinnest you guys go on the castings without worrying about blowing through them when running the car?
Re: Ported Stockers Revisited
i would look at having brass or bronze or copper brazzed on it first..
you would need to go lean and start melting other things before you melted it.
or road race it under boost for an hour...
Re: Ported Stockers Revisited
When I needed to weld a hole in an exhaust mani, I talked to an friend of mine who's been welding for about 40 years, he told me to order "missile rod", he couldn't remember the number on the rod, only the generic name.
I grabbed a couple pounds and he welded up a few pieces for me, I don't have a ton of run time on the parts but they've held up so far.
https://www.google.com/search?ei=f5C....0.eC42W-0DWjY
Re: Ported Stockers Revisited
Turbo exhaust manifolds have high nickel content, so that is th rod that my welder uses; he also builds up surfaces before porting with a spray on nickel fusion welding powder.
Re: Ported Stockers Revisited
Quote:
Originally Posted by
GLHS60
Good question but mine is has anyone actually gone too far and broken through while porting??
My pal Brian ported one for me very nicely but broke through in one spot.
Looking for input on welding up the small hole.
Any experienced input is appreciated!!
Thanks
Randy
I've broken through one, but I haven't welded it up yet. It's at my father's place at this time. I think we'll get to it one day...