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Author Topic: Belly Tank Build Diary  (Read 89331 times)
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Mike Brown
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« Reply #315 on: August 21, 2018, 09:14:11 AM »

I have attached a photo of the new intake.  I started with the fiberglass headrest that I bought with the original belly tank body that I did not use.  This design is too short and did not produce good MAF sensor signals.  I added an extension made from cardboard and tape which worked much better.  Now I need to decide if I am going to fabricate and extension or start from scratch on a one piece longer design. 


* New Scoop small.jpg (273.02 KB, 1008x756 - viewed 114 times.)
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Mike Brown
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« Reply #316 on: August 22, 2018, 09:56:39 AM »

The new scoop has a short section of intake tubing welded to a plate.  This short section of tubing is connected to the rest of the intake system using a flexible coupling and hose clamps.  The metal is attached to the fiberglass using methacrylate.  This adhesive is the best that I have ever used between metal and other materials.  I have not decided on starting on a longer scoop from scratch or extending this one.  Hopefully I will get some good advice from friends who have been there done that. 


* Back of Scoop small.jpg (271.64 KB, 1008x756 - viewed 68 times.)
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Mike Brown
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« Reply #317 on: August 28, 2018, 07:42:59 AM »

I decided to build a new scoop.  I used the "column of air" calculations with the "Woody" factor along with hydraulic area calculations for the size of the scoop.  The scoop is purposely long to hopefully not confuse the MAF sensor.  I started with 1/8" aluminum folded into a channel.  To improve the aerodynamics the tail will be tapered.  I marked out a design with cardboard template so the design would be symmetrical and cut it out with a saber saw. 


* New Scoop 1 small.jpg (310.27 KB, 1008x756 - viewed 55 times.)
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Mike Brown
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« Reply #318 on: August 28, 2018, 07:44:24 AM »

I folded the tail section by hand and TIG welded the corners. 


* New Scoop 2 small.jpg (289.51 KB, 1008x756 - viewed 71 times.)
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Mike Brown
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« Reply #319 on: August 28, 2018, 07:46:38 AM »

I welded a 4 inch "spigot" to a back plate that will attach to the intake system with a flexible coupling.  This back plate will form the floor of the scoop. 


* New Scoop 3 small.jpg (269.98 KB, 1008x756 - viewed 58 times.)
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Mike Brown
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« Reply #320 on: September 07, 2018, 07:27:55 PM »

The wonders of CNC.  I machined what I hope to be a flow straightener that will go opposite the air intake with the MAF sensor (unless Woody chimes in to tell me that I should throw it in the trash).  I used a section of 4-1/2" UHMW plastic.  The UHMW is secured to a piece of aluminum as you can rarely machine this stuff directly in a three jaw chuck without tossing it out of the machine.  Chip control is paramount as they are all continuous which can be very dangerous if they wrap around the tool post or worse yet a finger.  One line of code to set the radius and another that reads that line to rough the shape out in steps before the final smooth cut.  CNC machining still amazes me.  I was hoping to try a few of these options to reduce drag while keeping the MAF sensor happy at the 1/2 mile event close to home.  The event was canceled due to the rain.  So we will give a try in a couple of weeks. 


* Flow Straightener small.jpg (265.92 KB, 1008x756 - viewed 70 times.)
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Rex Schimmer
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« Reply #321 on: September 08, 2018, 02:07:12 PM »

Mike, Since you have a CNC lathe, you might consider machining the spigot and where it is connected to the scoop floor give it a nice large and smooth radius, then put a "blocking/turning" vane aft of the inlet spigot to direct the air to turn 90 degrees and go in your spigot. You mite even use two turning vanes, one about half way across the inlet spigot diameter that would only be about 1/2 of the scoop depth and then the final one that goes from the roof of the scoop to the floor with a nice radius. Also make sure that the scoop inlet is above the boundary layer at the inlet to insure full velocity air at the inlet.

Rex 
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Rex

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Mike Brown
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« Reply #322 on: September 09, 2018, 03:25:17 PM »

Rex,

Thanks for the input.  The bottom of the scoop is about 5/8" out from the body.  Is that enough to help with boundary flow issue?
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Rex Schimmer
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« Reply #323 on: September 09, 2018, 05:37:33 PM »

Mike,
Since your scoop is fairly far forward 5/8 should be good, the boundary layer should be pretty thin.

Rex
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« Reply #324 on: September 09, 2018, 06:26:19 PM »

The inside of the new scoop.  Regardless of what I do the engine will barely idle unless there is a some sort of restriction in the intake system.  I can simply place my hand over the intake with small gaps between my fingers and the engine idles good.  I calculated the open area of the screen and added it in front of the my "flow straightener" and the engine idles good.  It appears that the MAF sensor just needs some sort of pressure drop across it to work, I am not sure that turbulence is the real issue.  My hand across the intake could not be particularly good at reducing turbulence however I can feel the pressure drop.  I think it may be time to stop toying with the MAF sensor and get the speed density tune up. 


* New Scoop 5 small.jpg (238.45 KB, 1008x756 - viewed 48 times.)
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Mike Brown
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« Reply #325 on: September 09, 2018, 06:29:52 PM »

A photo of the new scoop attached to the car. 


* New Scoop 6 small.jpg (270.44 KB, 1008x756 - viewed 75 times.)
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Rex Schimmer
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« Reply #326 on: September 10, 2018, 07:43:28 PM »

Mike it looks good. Regarding the idle are  you sure that the butterfly is closing completely?

Rex
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« Reply #327 on: September 11, 2018, 07:00:58 AM »

Rex,

I potentially know where you are going with this.  For a decade I drove a Jeep with a blown early Hemi that had Hilborn mechanical fuel injection (prepared by Junior Thompson) and a Lenco transmission on the street.  Those 3" butterflies rarely fully closed after cruising with reasonably high intake manifold vacuum regardless of how many return springs were used.  An 1,100 rpm idle equated to .002" clearance between the butterflies and the injector housing.  I had to rap on the throttle to reduce the intake manifold vacuum so the butterflies would snap shut.  Not the safest thing to do on the street.  I eventually replaced the mechanical fuel injection with a pair of Weber carburetors which had ball bearings on the throttle shafts which exhibited much better (safer) behavior on the street.  

This is a modern computer controlled engine.  The throttle is drive-by-wire with a servo motor operating the butterfly which is controlled by the engine electronic control unit.  The throttle pedal is electronic.  I was concerned about that and one of the reasons that I added the AEM data logger.  There are multiple things going on between your foot and the butterfly.  By trial and error I did find the actual butterfly position in the data log (I can watch it real time) and it looks OK.  The actual idle speed is controlled by an idle air control motor.  This is a stepper motor that works an idle air circuit that bypasses the main butterfly.  This circuit is somewhat like the idle circuit on a Weber IDF carburetor.  

On my initial dyno pull the tuner told me that my blower belt was slipping because the boost was never as high as it should have been.  I only have a crankshaft pulley and blower pulley with a rib belt.  I use a fixed tensioner verses a spring loaded version and did not think that the belt was slipping.  Looking at the data from the Kilkare run (after I had tightened the belt) I still had low boost.  I researched this and found that the blower bypass butterfly was set incorrectly from the factory.  On most modern supercharged engines they use a butterfly in the intake system that allows the blower to be bypassed during normal driving which helps to keep the intake air temperatures down.  The engine electronic control unit controls this butterfly with vacuum/boost pressure acting on a diaphragm and a solenoid.  To keep the butterfly from sticking there is the equivalent of an idle adjustment screw.  It was an improper adjustment of this screw that kept the butterfly open slightly further than it should have been reducing my boost.  I am contemplating eliminating this feature.  This feature is great on a vehicle with traction control and a body computer that helps to keep the average Joe from getting into too much trouble on the street but may be complicating driving a race vehicle with the goal of using the most horsepower available.  

I am just in the infancy of figuring this combination out.  It will be interesting to see how it turns out.  
« Last Edit: September 11, 2018, 07:01:38 PM by Mike Brown » Logged
NathanStewart
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« Reply #328 on: September 18, 2018, 03:41:28 PM »

Hi Mike, glad to see you're still hang in there and learning and progressing. Hope all is well.
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Mike Brown
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« Reply #329 on: September 25, 2018, 09:39:41 AM »

I use the Tilton 6000 series hydraulic clutch release bearings.  The cockpit of the lakester is so small that I could not get enough stroke on the clutch pedal to insure a complete release of the dual disc LSA clutch.  Sometimes there was a clash when shifting the transmission into gear when stopped.  I never had any problems shifting the transmission when running.  I was using the standard 7/8" master cylinder.  So using the philosophy of if 7/8" is not large enough bigger must be better I installed 1-1/8" master cylinder.  I had no more problems with the clutch releasing fully.  After that I had multiple problems breaking the tires loose shifting into second gear.  Both at Blytheville and Kilkare dragstrip.  The clutch had a somewhat digital feel, in or out.  I decided to try a 1" master cylinder which still gives me a full clutch release but retains some feeling that I can release the clutch smoothly without dumping it all at once.  I was hoping to see how this theory worked in practice but the 1/2 mile event in Batesville Indiana was canceled do to angry homeowners adjacent to the track which resulted in the new facility owners seeking rezoning for the property.  I will most likely head back to Kilkare dragstrip for a test & tune session. 


* Master Cylinder small.jpg (401.22 KB, 1008x756 - viewed 21 times.)
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