Newest Project - Lower Intake Manifold for Fabricated S4 Intakes
05-28-2014, 03:40 PM
#121
Lets start the roll call.
06-02-2014, 03:20 PM
#122
Bump
06-02-2014, 04:16 PM
#123
Rennlist
Basic Site Sponsor
Basic Site Sponsor
This project is back from the dead. Funds wont allow for casting, so I wont be able to offer the "cheap" flanges I originally envisioned, but I will be able to offer affordable flanges machined from 6061. I have profiles available for 2"OD-11g, 2"OD-16g, 2.25"OD-11g, and 2.25"OD-16g. First batch will be the 2"-11g as it will allow for easy integration with a number of aftermarket parts. I can offer any of the other profiles if I receive an order for 5-sets.
Here is one configuration (runners not yet optimized in length, but all the difficult geometry angles are solved) using off the shelf bends. The blue plane is a worse-case scenario hood line with brand new motor mounts based on the constraint of the original intake manifold.
http://cloudviewer.spaceclaim.com/e8...8a4c51074.html
I am placing a deposit for the tooling and programming, and will get an evaluation set in before accepting orders, but it will be fairly simple to make any number of intake configurations.
Here is one configuration (runners not yet optimized in length, but all the difficult geometry angles are solved) using off the shelf bends. The blue plane is a worse-case scenario hood line with brand new motor mounts based on the constraint of the original intake manifold.
http://cloudviewer.spaceclaim.com/e8...8a4c51074.html
I am placing a deposit for the tooling and programming, and will get an evaluation set in before accepting orders, but it will be fairly simple to make any number of intake configurations.
1. Measure the ID of the stock S4 runners. You are going to need that ID....minimum.
2. Take that number and translate it into the OD of an aluminum tube.
3. Multiply by 8. Add in a minimum of 1/8" where the runners cross. Record that total on a tape measure.
4. Take that tape measure out to an engine compartment and lay it on top of the stock intake....just behind the stock chassis stiffing bar.
5. Enough said?
It's a bitch of a job. Porsche did a fantastic job of "packaging" their intake manifold, in that space. While not perfect, it's pretty damn nice.
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
06-02-2014, 05:07 PM
#124
Nordschleife Master
That looks vaguely familiar. Been there.
1. Measure the ID of the stock S4 runners. You are going to need that ID....minimum.
2. Take that number and translate it into the OD of an aluminum tube.
3. Multiply by 8. Add in a minimum of 1/8" where the runners cross. Record that total on a tape measure.
4. Take that tape measure out to an engine compartment and lay it on top of the stock intake....just behind the stock chassis stiffing bar.
5. Enough said?
It's a bitch of a job. Porsche did a fantastic job of "packaging" their intake manifold, in that space. While not perfect, it's pretty damn nice.
1. Measure the ID of the stock S4 runners. You are going to need that ID....minimum.
2. Take that number and translate it into the OD of an aluminum tube.
3. Multiply by 8. Add in a minimum of 1/8" where the runners cross. Record that total on a tape measure.
4. Take that tape measure out to an engine compartment and lay it on top of the stock intake....just behind the stock chassis stiffing bar.
5. Enough said?
It's a bitch of a job. Porsche did a fantastic job of "packaging" their intake manifold, in that space. While not perfect, it's pretty damn nice.
The first question is whether one should use the stock S4 gasket and fasteners or not. If one will use those, then one does not need to build additional thermal expansion compliance into the manifold. If one will dowel pin the intake to the heads precisely and use gasket/attachment without any compliance, then one will need to build some compliance in the manifold itself, for example with silicone couplers. Both methods have their pros and cons. In a max effort racing engine, I would dowel pin the manifold to the heads and for a low-maintenance street engine I'd probably use the stock gasket. Others may end in a different conclusion.
If one goes with the stock gasket and fasteners for the flanges, then in my opinion one doesn't need to leave any clearance between the opposing bank runners. In fact, one could even permanently attach them together to provide a part of the plenum ceiling - not a practical choice in welded manifolds but a common practice with cast manifolds.
Some silicone couplers are likely needed when the runners are attached to a closed plenum top. For fabricated manifolds, this is because I don't think there are many humans or robots who are skilled enough to weld in blind spots under the runners with no access whatsover. For cast manifolds, the casting techniques are going to make it a lot cheaper to cast the runner top separately from the bottom plenum, which means one will still need some sort of coupling system to attach the plenum to the runners. One could in principle fabricate a plenum top with precisely located holes for the runners and weld them on from the inside before welding on the bottom of the plenum, but any adjustments would be pretty difficult after that point of no return.
Round tubes are inconvenient in a manifold like this. Oval tubes would be much more convenient, but oval in the different ridection than the ports. This is because those oval tubes will cross in a lot smaller space. Fabricating the oval tubes from a larger diameter mandrel bent round tube while providing a transition back to smaller diameter round in the end is challenging. Having them cut from an aluminum blank is expensive. Having them cast is expensive for the series size we're talking about here.
The required runner diameter is an interesting question. The stock manifold runners are large, as evidenced by the experience by people who have extrude honed the stock manifold. Just increasing the stock runner diameter will reduce power for most engines - my belief, not a fact. The runners can be relatively small diameter as long as they are very straight. It's the number of curves and the short radius of those curves in the stock runners that kill the top end power, not the so much the diameter.
If one wants to keep the stock MAF in its stock location, that puts some serious constraints on runner placement. Basically, the rear runners need to run as high as possible and the plenum needs to have an irregular shape with enough clearance at the rear. Speed density or alpha-N or relocated dual MAFs would give more design flexibility but will add to the cost in various ways.
If one wants to keep the stock air box or even the stock air box location for the filter, that puts some constraints on the rear primary runners. There's probably less than an inch of clearance between one of the rear primary runners and the air box, so one either has to move the filter or curve the runners in a very particular way. This is less of an issue for me, since I already have filters in the front - I could just replace the air box with a Y-pipe. With Y-pipe and MAF, getting the flow to fully develop to give consistent MAF readings is another challenge. Honeycomb flow straightener is one possible solution.
In the end, with the possible runner lengths, one could come up with a manifold that underperforms the stock manifold below about 3500 rpm but outperform it above 3500 rpm.
For my purposes (turbo car), a 6" primary runner manifold with as straight runners as possible makes a lot more sense than say 12" runners crossing into a plenum below. The 12" runner manifold (12" in the runner and 4" in the head for 16" total tract length) adds torque to mid range where I don't need it. I need more torque either at the top or the bottom, not in the mid range.
06-02-2014, 06:21 PM
#125
Rennlist
Basic Site Sponsor
Basic Site Sponsor
I've been looking at the runner placement and packaging for a long (12") runner manifold. Mostly just as an academic exercise. It's pretty challenging and therefore fun. Here's what I've concluded after thinking about it, but not having tried it yet.
The first question is whether one should use the stock S4 gasket and fasteners or not. If one will use those, then one does not need to build additional thermal expansion compliance into the manifold. If one will dowel pin the intake to the heads precisely and use gasket/attachment without any compliance, then one will need to build some compliance in the manifold itself, for example with silicone couplers. Both methods have their pros and cons. In a max effort racing engine, I would dowel pin the manifold to the heads and for a low-maintenance street engine I'd probably use the stock gasket. Others may end in a different conclusion.
If one goes with the stock gasket and fasteners for the flanges, then in my opinion one doesn't need to leave any clearance between the opposing bank runners. In fact, one could even permanently attach them together to provide a part of the plenum ceiling - not a practical choice in welded manifolds but a common practice with cast manifolds.
Some silicone couplers are likely needed when the runners are attached to a closed plenum top. For fabricated manifolds, this is because I don't think there are many humans or robots who are skilled enough to weld in blind spots under the runners with no access whatsover. For cast manifolds, the casting techniques are going to make it a lot cheaper to cast the runner top separately from the bottom plenum, which means one will still need some sort of coupling system to attach the plenum to the runners. One could in principle fabricate a plenum top with precisely located holes for the runners and weld them on from the inside before welding on the bottom of the plenum, but any adjustments would be pretty difficult after that point of no return.
Round tubes are inconvenient in a manifold like this. Oval tubes would be much more convenient, but oval in the different ridection than the ports. This is because those oval tubes will cross in a lot smaller space. Fabricating the oval tubes from a larger diameter mandrel bent round tube while providing a transition back to smaller diameter round in the end is challenging. Having them cut from an aluminum blank is expensive. Having them cast is expensive for the series size we're talking about here.
The required runner diameter is an interesting question. The stock manifold runners are large, as evidenced by the experience by people who have extrude honed the stock manifold. Just increasing the stock runner diameter will reduce power for most engines - my belief, not a fact. The runners can be relatively small diameter as long as they are very straight. It's the number of curves and the short radius of those curves in the stock runners that kill the top end power, not the so much the diameter.
If one wants to keep the stock MAF in its stock location, that puts some serious constraints on runner placement. Basically, the rear runners need to run as high as possible and the plenum needs to have an irregular shape with enough clearance at the rear. Speed density or alpha-N or relocated dual MAFs would give more design flexibility but will add to the cost in various ways.
If one wants to keep the stock air box or even the stock air box location for the filter, that puts some constraints on the rear primary runners. There's probably less than an inch of clearance between one of the rear primary runners and the air box, so one either has to move the filter or curve the runners in a very particular way. This is less of an issue for me, since I already have filters in the front - I could just replace the air box with a Y-pipe. With Y-pipe and MAF, getting the flow to fully develop to give consistent MAF readings is another challenge. Honeycomb flow straightener is one possible solution.
In the end, with the possible runner lengths, one could come up with a manifold that underperforms the stock manifold below about 3500 rpm but outperform it above 3500 rpm.
For my purposes (turbo car), a 6" primary runner manifold with as straight runners as possible makes a lot more sense than say 12" runners crossing into a plenum below. The 12" runner manifold (12" in the runner and 4" in the head for 16" total tract length) adds torque to mid range where I don't need it. I need more torque either at the top or the bottom, not in the mid range.
The first question is whether one should use the stock S4 gasket and fasteners or not. If one will use those, then one does not need to build additional thermal expansion compliance into the manifold. If one will dowel pin the intake to the heads precisely and use gasket/attachment without any compliance, then one will need to build some compliance in the manifold itself, for example with silicone couplers. Both methods have their pros and cons. In a max effort racing engine, I would dowel pin the manifold to the heads and for a low-maintenance street engine I'd probably use the stock gasket. Others may end in a different conclusion.
If one goes with the stock gasket and fasteners for the flanges, then in my opinion one doesn't need to leave any clearance between the opposing bank runners. In fact, one could even permanently attach them together to provide a part of the plenum ceiling - not a practical choice in welded manifolds but a common practice with cast manifolds.
Some silicone couplers are likely needed when the runners are attached to a closed plenum top. For fabricated manifolds, this is because I don't think there are many humans or robots who are skilled enough to weld in blind spots under the runners with no access whatsover. For cast manifolds, the casting techniques are going to make it a lot cheaper to cast the runner top separately from the bottom plenum, which means one will still need some sort of coupling system to attach the plenum to the runners. One could in principle fabricate a plenum top with precisely located holes for the runners and weld them on from the inside before welding on the bottom of the plenum, but any adjustments would be pretty difficult after that point of no return.
Round tubes are inconvenient in a manifold like this. Oval tubes would be much more convenient, but oval in the different ridection than the ports. This is because those oval tubes will cross in a lot smaller space. Fabricating the oval tubes from a larger diameter mandrel bent round tube while providing a transition back to smaller diameter round in the end is challenging. Having them cut from an aluminum blank is expensive. Having them cast is expensive for the series size we're talking about here.
The required runner diameter is an interesting question. The stock manifold runners are large, as evidenced by the experience by people who have extrude honed the stock manifold. Just increasing the stock runner diameter will reduce power for most engines - my belief, not a fact. The runners can be relatively small diameter as long as they are very straight. It's the number of curves and the short radius of those curves in the stock runners that kill the top end power, not the so much the diameter.
If one wants to keep the stock MAF in its stock location, that puts some serious constraints on runner placement. Basically, the rear runners need to run as high as possible and the plenum needs to have an irregular shape with enough clearance at the rear. Speed density or alpha-N or relocated dual MAFs would give more design flexibility but will add to the cost in various ways.
If one wants to keep the stock air box or even the stock air box location for the filter, that puts some constraints on the rear primary runners. There's probably less than an inch of clearance between one of the rear primary runners and the air box, so one either has to move the filter or curve the runners in a very particular way. This is less of an issue for me, since I already have filters in the front - I could just replace the air box with a Y-pipe. With Y-pipe and MAF, getting the flow to fully develop to give consistent MAF readings is another challenge. Honeycomb flow straightener is one possible solution.
In the end, with the possible runner lengths, one could come up with a manifold that underperforms the stock manifold below about 3500 rpm but outperform it above 3500 rpm.
For my purposes (turbo car), a 6" primary runner manifold with as straight runners as possible makes a lot more sense than say 12" runners crossing into a plenum below. The 12" runner manifold (12" in the runner and 4" in the head for 16" total tract length) adds torque to mid range where I don't need it. I need more torque either at the top or the bottom, not in the mid range.
I've never had an S4 manifold "backwards" on a flow bench, so I'm clueless about this.
06-02-2014, 07:05 PM
#126
Nordschleife Master
The long answer is that if everything is well functioning, the pressure differential between the cylinder and the intake plenum is not much higher for a turbo car than normally aspirated car. It's there between 0 and 2 psi, depending on various things. I think the factory conventions (when they still owned flow benches and not just computers) used to be 20 inches of water, which perhaps coincidentally is in the middle of the range.
So both the turbo and the normally aspirated car "push" air to the cylinder, the NA car having a 14.5 psi absolute or something in the plenum and 13.5 psi absolute in the cylinder and the turbo car having say 24.5 psi absolute in the plenum and 13.5 psi absolute in the cylinder. The flow bench as a system also only "pushes" air, regardless of which way the motor is run. The plenum having 14.7 absolute and the cylinder 14.7 psi absolute minus whatever the test pressure, which for 20 inches of water adds up to 13.7 or so. Or the intake hooked up to the bench the other way around and the bench motor run the other direction, the plenum now having 14.7 plus the test pressure, say 15.7, and the cylinder head end seeing 14.7 of the ambient air.
What is very different between turbo and normally aspirated cars is the density of the air in the runner. There's no way to test that on a standard flow bench, because whichever way you run the bench and the manifold it's always going to have about ambient air density in the intake runner (1.23 kg / m^3 or so). To realistically test a 10-psi boost turbo manifold, one would have to somehow have the plenum at 24.5 psi absolute and the cylinder at 23.5 psi absolute, which would then have a density of 1.6-2.0 kg / m^3 depending on the efficiency of compression and subsequent cooling. I don't know how to do that and I don't personally know anyone who knows how to do that.
Someone like me is then left with some rules of thumb to make some guesses and look at other people's turbo manifolds and try to copy what works. What seems to work is that up to 20 psi boost any manifold that distributes about equally is going to work well on a 5.0L engine and the car is going to fly. At higher boost levels, 30 psi plus, extremely straight and short tapered runners seem to work well. Might have something to do with friction growing with density, and the denser charge generating adequately strong pulses even with a short runner. I don't know.
12-09-2014, 07:05 PM
#128
Rennlist Member
Why cant we just adapt some of the awesome intake plennums and runners to our system as I joked about before by slapping the BMW M5 intake over my 928 intake. it seems that if you had that adapater shown here, and then some custom joiner tubes, you could have some mass produced, very efficient intakes, that could be bolted on to the 928 with minimal adaption.
heck, even the Aston or Mustang intake, albeit a little too high would yield some big gains. they are now getting near 450rwhp out of a 5 liter, stock, with not much compression (11.1) and 8300rpm.
I don't think it has a radical cam by any stretch and it's valves are not that huge. someday, one of those trick intakes will be put on the 928.
I think your custom 928 intake did 360 rwhp on a stock 5 liter, right? I forgot what that even looked like, but It sounds like it worked well!
12-10-2014, 10:17 AM
#129
Rennlist Member
Thread Starter
Oddly enough, I have received three emails in the past week about flanges. I got a call last week from one of the shops I use looking for some work as they are running low on jobs in the off-season.
We spoke yesterday, and he thinks they can get some flanges made at a good price if I make some design changes to fit it in a 1.25" bar stock. Currently the part is about 1.28" tall, which would require the use of 1.5" raw stock, which would add to the price both at the material and machine time stages.
I am supposed to get a +/-20% number today based on the original design assuming if it were modified to a height of 1.23" to fit inside the less expensive bar stock. If the numbers look good, I will redesign the flange from scratch over the weekend and put a PO in on Monday for 5-sets.
We spoke yesterday, and he thinks they can get some flanges made at a good price if I make some design changes to fit it in a 1.25" bar stock. Currently the part is about 1.28" tall, which would require the use of 1.5" raw stock, which would add to the price both at the material and machine time stages.
I am supposed to get a +/-20% number today based on the original design assuming if it were modified to a height of 1.23" to fit inside the less expensive bar stock. If the numbers look good, I will redesign the flange from scratch over the weekend and put a PO in on Monday for 5-sets.
12-10-2014, 02:22 PM
#130
I'm in. As I always have been. Either 1 or 2 sets.
12-30-2014, 04:14 PM
#132
Rennlist Member
Thread Starter
So... finally have firm pricing from the shop to make these lower manifold flanges, and it looks good if we can get at least 5 sets in the first batch. I will take the time to make the small modifications to get them to fit in the less expensive bar stock this weekend if we get to 5 sets or more.
For the first five sets, I can get these done from 6061 billet for $600/pair +shipping.
I will design them for the common stock 14mm Bosch lower o-ring, and they will have blank bosses where the stanchions are located for any number of fuel rail configurations.
I can provide matching fuel rails if there is interest, and would have these quoted after the order goes in for the lower manifolds.
The last detail is what size runner do people want. I can do either a 1.75" or 2" ID, but all sets would have to be designed for the same diameter.
Lets get a raise of hands on who wants sets and what ID runner they want. If we get the 5 sets an agreed ID, I will collect the funds on Friday, modify the design over the weekend, and get the updated files to the shop Monday morning with the deposit to get the material ordered.
Thanks
Hans
For the first five sets, I can get these done from 6061 billet for $600/pair +shipping.
I will design them for the common stock 14mm Bosch lower o-ring, and they will have blank bosses where the stanchions are located for any number of fuel rail configurations.
I can provide matching fuel rails if there is interest, and would have these quoted after the order goes in for the lower manifolds.
The last detail is what size runner do people want. I can do either a 1.75" or 2" ID, but all sets would have to be designed for the same diameter.
Lets get a raise of hands on who wants sets and what ID runner they want. If we get the 5 sets an agreed ID, I will collect the funds on Friday, modify the design over the weekend, and get the updated files to the shop Monday morning with the deposit to get the material ordered.
Thanks
Hans
Last edited by hans14914; 01-10-2015 at 12:39 PM.
12-30-2014, 05:20 PM
#133
As ever, I am in.
12-30-2014, 06:29 PM
#135
Rennlist Member
Thread Starter
To share the conversation publicly, here are the highlights of email with Tuomo:
Critical 928 related dimensions:
Cross-sectional area of the port at the sealing surface of the head - 1867.84mm^2
Cross-sectional area of the port at the sealing surface of the manifold (excluding injector bung)- 1688.67mm^2
Common material dimension:
2"OD-1.75"ID RMR extruded tube internal cross-sectional area - 1551.79mm^2
2"OD-16guage (1.87" ID) internal cross-sectional area - 1771.9mm^2
2.25"OD-2"ID RMR extruded tube internal cross-sectional area - 2026.83mm^2
2.25"OD-11guage (2.1" ID) internal cross-sectional area - 2047.15mm^2
My vote is for the 2.25" 11g tubing, as you can use it in mandrel bent form or use the 2.25"OD-2"ID extrusions from Ross Machine Racing depending on your application. The thicker wall will be much easier to weld to the flange without blowing through for those assembling manifolds at home. The 2"-16g is probably the optimal selection all things considered, but it could be a pain to work with.
Thoughts?
Hans
Critical 928 related dimensions:
Cross-sectional area of the port at the sealing surface of the head - 1867.84mm^2
Cross-sectional area of the port at the sealing surface of the manifold (excluding injector bung)- 1688.67mm^2
Common material dimension:
2"OD-1.75"ID RMR extruded tube internal cross-sectional area - 1551.79mm^2
2"OD-16guage (1.87" ID) internal cross-sectional area - 1771.9mm^2
2.25"OD-2"ID RMR extruded tube internal cross-sectional area - 2026.83mm^2
2.25"OD-11guage (2.1" ID) internal cross-sectional area - 2047.15mm^2
My vote is for the 2.25" 11g tubing, as you can use it in mandrel bent form or use the 2.25"OD-2"ID extrusions from Ross Machine Racing depending on your application. The thicker wall will be much easier to weld to the flange without blowing through for those assembling manifolds at home. The 2"-16g is probably the optimal selection all things considered, but it could be a pain to work with.
Thoughts?
Hans