Supercharger intake plenum extension question?

Joel K

Supporter
For a supercharged engine, most builds use an aluminum tube/elbow and throttle body adapter flanges to turn the throttle body around. I am wondering if the intake extension needs to be aluminum or could it be a silicone tube that sits between the supercharger and the throttle body.

Just wondering if I could get by with using a 4” diameter cobra head silicone intake tube between the supercharger and throttle body. This approach may help package an LT4 into an SLC without modifying the bulkhead. Looking for some thoughts from others with more experience on how supercharged engines work.

Thanks for you input.
 

Roger Reid

Supporter
I'm machining an aluminum flange to fit my magnuson. Fortunately the Maggie starts out at a 30 degree angle. Then I have some 4" polished tubing coming in from Spectre that I'm going to splay (cut, spread and weld) one end to fit the flange. https://www.spectreperformance.com/cat/air-intake-components-tubes-aluminum-4-0-90-degree?cat=C00000073 Similar process as modifying LS7 headers.
Could you post a pic of the nose end of your supercharger?
If the silicone elbow you were talking about is rated for manifold vacuum you should be ok.
Some other thoughts are to draw the intake manifold up in cadd then have it 3d printed. Then skin the outside with carbon fiber and remove (grind/cut/melt) the core out. I haven't checked on wax materials that can be used in a 3d printer but I believe it is available. Maybe Scott could chime in.

Magnuson flange.JPGIntake tube 1.JPG
 

Joel K

Supporter
I'm machining an aluminum flange to fit my magnuson. Fortunately the Maggie starts out at a 30 degree angle. Then I have some 4" polished tubing coming in from Spectre that I'm going to splay (cut, spread and weld) one end to fit the flange. https://www.spectreperformance.com/cat/air-intake-components-tubes-aluminum-4-0-90-degree?cat=C00000073 Similar process as modifying LS7 headers.
Could you post a pic of the nose end of your supercharger?
If the silicone elbow you were talking about is rated for manifold vacuum you should be ok.
Some other thoughts are to draw the intake manifold up in cadd then have it 3d printed. Then skin the outside with carbon fiber and remove (grind/cut/melt) the core out. I haven't checked on wax materials that can be used in a 3d printer but I believe it is available. Maybe Scott could chime in.

View attachment 98354View attachment 98355
Thanks for the input Roger, below is a pic of the LT4 Magnusson and stock supercharges side by side. The Maggie is a bigger blower and uses the stock tune, but would be extra $$$ since I already have a supercharger.

I’ll ask the supplier of the silicone elbow mfg and see. I know it’s intended use is to be in front of the throttle body and not behind. Is there a difference in pressure? Based on the technical specs, an LT4 max boost is 9.7psi, but no idea if that is the manifold pressure.

I have a fabricator who can help reproduce the elbow in aluminum if needed, would just be easier to add a flange with a 4” stub tube to each end of the silicon cobra head and be done with it but may not be ideal.

21A0CA13-530B-4787-B2D0-E6BD3CBC0D33.jpeg
 
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Scott

Lifetime Supporter
Roger, my plan is to do exactly as you stated. Aluminum up to the throttle body, then 3D print a sacrifice shell to be wrapped in carbon fiber and then dissolved. 3D printing leaves ridges so I'll need to sand the OD smooth. This will result in better airflow than a metal intake because there are no weld seams. Since the shape will be a little complex the idea is to print snap together pieces with different radii. This will enable them to be clocked/oriented while on the car (Like ICE Engine Works kit). This should make it easy to obtain perfect routing.

Benefits are; optimal routing, very light, excellent heat rejection, smoothest interior... now I just need to make it as good as I imagine;-)
 

Roger Reid

Supporter
I feel your LT4 supercharger is a great choice. Don't change the supercharger.

I feel you are in the same position I am. Make or buy a flange that fits your supercharger, weld an aluminum tubing bend to it. Add tubing bits to it until you get the TB where you want it. Weld another flange on the inlet side and bolt the TB in place. I found my flange at https://www.ictbillet.com/gen-5-lt5-95mm-throttle-body-adapter-plate-to-lt1-intake-manifold-or-lt4-sc.html

The 9.7 psi is the pressure generated at and after the rotors. Air pressure between the filter and throttle body see's very little vacuum. A silicone elbow can handle this easily. Between the TB and valves (intake manifold) you see little to no vacuum during wide open throttle but around prox 18" vacuum (depending on your cam) at idle. At idle the motor wants to suck in air but the throttle body holds it back, IE vacuum. Superchargers develop boost or positive pressure after the screw or rotor but no pressure before the rotors which is where the throttle body is located. So bottom line is that the piping between the TB and supercharger will see zero to prox 18" vacuum depending on throttle opening.

Contact the manufacturer of the silicone elbow and ask them if it can handle 18" vacuum without collapsing.
 

Roger Reid

Supporter
...3D print a sacrifice shell to be wrapped in carbon fiber and then dissolved...
Scott, question. If you didn't have the supercharger to TB intake section already fabed up, would you consider the method you described above for that purpose?
 

Scott

Lifetime Supporter
The supercharger to throttle body section wasn't well executed. It's being tossed and I'm starting over. I thought about doing it all in carbon but I wasn't sure of my ability to get something to support the weight of the throttle body with vibrations etc. That section is a simple bend and easy to do in aluminum. The tube between the throttle body and the cold air intake box is a lot more complicated and I may need to flatten the tube Between that complexity and the fact that it doesn't need to support any weight other than it's own makes it a good candidate for custom carbon fiber.. That's the current plan. but my plans change a lot!
 

Roger Reid

Supporter
I've got several pieces of 4" od, 3.8" (96.52mm) id polished tubing bends coming in from Spectre. My SC has a squared oval shape. Larger than the 4" tubing, I need to match to. Plus my TB is 102mm. So I'm planning to horizontally split my tubing, shape the end of the half round until it fits the flange pic I posted above, then add material where needed to get to 4.016 id on the small end. At least that's the plan for now.
 

Joel K

Supporter
I heard back from the Cobra head intake tube manufacturer and he did not think it was suitable to use after the throttle body and it would collapse due to the vacuum pressure. Since I’m close to getting the engine in the car then I’ll know exactly how much room there is and see if I can use it before the throttle body, if not go to plan B and fabricate an aluminum elbow of some shape that will provide enough flow and clear the rear chassis brace.
 

Joel K

Supporter
I've got several pieces of 4" od, 3.8" (96.52mm) id polished tubing bends coming in from Spectre. My SC has a squared oval shape. Larger than the 4" tubing, I need to match to. Plus my TB is 102mm. So I'm planning to horizontally split my tubing, shape the end of the half round until it fits the flange pic I posted above, then add material where needed to get to 4.016 id on the small end. At least that's the plan for now.
That’s a big throttle body, the stock LT4 is 87mm. You made a good choice on the supercharger, based on the pictures it should fit in very nicely.
 

Joel K

Supporter
Roger,

I checked the specter performance web site and found the following:

1A423A74-9EA8-42F0-AA5F-E096B89F8012.jpeg
ABB2BAAC-3A96-4DE9-A172-82D26B9B4820.jpeg

The dimensions are almost identical to the silicone cobra head tube I have. I could use this as the basis for a flat intake elbow. Maybe cut out the hole for the carb bolt and make it flat then add a 4” tube and flange to mate it up with the supercharger.

Do you think this could provide enough flow?

I also found this one which just looking at the dimensions should provide enough flow and may fit nicely.

86BCB852-CCBC-479A-8688-A6677832C8DD.jpeg
78A29A2F-62CA-4BC4-861C-415FB2F6CA5B.jpeg

These are a good find and I’ll take the measurements once the engine is in the chassis. Thanks Roger for the link!
 
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Joel K

Supporter
Thanks Ken, I have not thought about using stainless but that may work out better. Do you happen to know if the flanges would then need to be stainless as well? I am assuming you can’t weld stainless to aluminum but don’t really know. I probably can machine up the flanges in either aluminum or metal. I know I can buy the flanges in aluminum and not sure about stainless.
 
Flanges would have to be stainless as well. I forgot it was stainless and not aluminum....sorry.

I'm pretty sure the flanges will not be available in stainless
 
Thanks for the input Roger, below is a pic of the LT4 Magnusson and stock supercharges side by side. The Maggie is a bigger blower and uses the stock tune, but would be extra $$$ since I already have a supercharger.

I’ll ask the supplier of the silicone elbow mfg and see. I know it’s intended use is to be in front of the throttle body and not behind. Is there a difference in pressure? Based on the technical specs, an LT4 max boost is 9.7psi, but no idea if that is the manifold pressure.

I have a fabricator who can help reproduce the elbow in aluminum if needed, would just be easier to add a flange with a 4” stub tube to each end of the silicon cobra head and be done with it but may not be ideal.

View attachment 98356
FYI- per the magnuson site and manual, the LT4 blower does NOT use the stock tune.
 

Joel K

Supporter
FYI- per the magnuson site and manual, the LT4 blower does NOT use the stock tune.
Thanks Chris. Yes, I misread the description since the LT4 does not come with a tune I thought you would use the stock tune, but looks like it requires a custom tune.

Now that I have the engine in the car, looks like I have enough room to fab up an intake elbow without cutting a V in the rear 2x6” crossmember and use the factory blower.
 

Joel K

Supporter
I have spent some more time thinking about an LT4 throttle body intake elbow. I really would prefer not to modify the chassis cross brace and came up with this prototype design which does clear the frame. It is made out of a pool float noodle, duct tape, and an HVAC tube. Although using Auto-CAD may be in my future, but for now doing it old school.

I used a 4” Silicone Cobra Head Elbow as the basis for the design and the primary logic I used to convince myself this will work is as follows:

1)The intake plenum on the super charger is 3.5” diameter. Surface area is 9.6”
2)The 4” Cobra Head Elbow is supposed to flow 90% of a standard 90 degree silicone elbow.
3)The design I came up with should have equal or more surface area than a 4” OD tube through the elbow. Surface area is 12.56, 90% is 11.3 which is about 17% more surface area than the supercharger plenum.
4)I have absolutely no know knowledge of fluid dynamics to know if this will work and if the elbow bend is an issue an which will reduce flow or create turbulence, etc. to the point where it won’t work.

I plan to fab it up as is with a slight mod of getting more of the 4” tube extending the length of the elbow increasing the surface area. Also, if I can get it to fit, I have a car with a V8 Supercharged engine so may just bolt it on and see if it throws codes and see how it runs.

Just looking for some continued feedback on the subject and approach.

Side by side, Silicone Cobra Head and prototype. The prototype looks a little smaller, but the walls of the tube are thinner but internal dimensions are very close.
10D6FF3A-8D64-4CB1-83F5-D8582EEB135A.jpeg


Looks like I meet my goal of clearing the bulkhead...
14193C28-02F9-4B00-AFCF-921949F8CDC4.jpeg


Will modify this to have more of the 4” tube extend the length of the flat portion to increase surface area.
FB33442B-3811-4B93-8491-878805FC4BA8.jpeg


To me it looks pretty good with the throttle body in place. Need to add the other TB flange when I get it
782F9428-2F7E-42E7-918D-696AA4AF6660.jpeg
 
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