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UFO Installation & Test (Read 297 times)
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UFO Installation & Test
04/11/20 at 02:28:17
 
This report gives the details for installation of an Ultimate Flow Optimizer (UFO) in a Mikuni VM38 carburetor.  It also summarizes the test results after installation.

The UFO is a device that’s intended to eliminate turbulence and increase air flow through the carburetor.  The product is marketed by Thunder Products, Inc. (TPI).  Their phone number is (320) 597-2700.  Their website is thunderproducts.com.
 
TPI lists a whole bunch of things you can expect from the UFO, including but not limited to:

     -More horsepower with less fuel
     -Broader powerband
     -Exceptional throttle response
     -Simple installation

Lancer was kind enough to loan me a UFO for this test.  I installed it and had a lot of fun, learned a few things too.

Let’s get started.

Here’s what you get in the kit.   On the left is a drill guide that you use to drill a hole in the bottom of the slide.  On the right is the UFO.  On the bottom is a self-tapping screw that is used to secure the UFO to the slide.  The kit also has instructions, but they leave out a few tuning details.
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UFO_Kit_2.JPG

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Re: UFO Installation & Test
Reply #1 - 04/11/20 at 02:29:17
 
The standard VM38 carburetor comes with a #2.5 slide.  The UFO is intended for use with a #3.5 slide.  The instructions tell you to grind the slide to suit the UFO.  I decided to purchase a new #3.5 slide.  That way, I would be able to switch back & forth for comparative testing (and oh boy, I did I a lot of switchin back & forth).

Here’s a look at the 3.5 slide with UFO installed next to the standard (as-delivered) 2.5 slide.  The UFO fits perfectly.  It’s a high-quality plastic part.
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UFO_Slide_Comparison_2.jpg

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Re: UFO Installation & Test
Reply #2 - 04/11/20 at 02:30:43
 
The first step in the installation process is to get a good baseline on your jetting.  My VM38 was dialed in perfectly with a wide-band air/fuel ratio meter so I knew I had a good baseline.

PJ 22.5
MJ 210
NJ Q-2
Needle 6DP1
Clip middle groove
Air screw 1-5/8 turns
Main Air Bleed 0.5
Slide 2.5
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Re: UFO Installation & Test
Reply #3 - 04/11/20 at 02:31:24
 
Once you have a good baseline, remove the carburetor and start the installation.  The instructions tell you it’s gonna run rich at idle, so you need to reduce the size of the pilot jet.  I spoke with Lon at TPI and he advised me not to go below a #15 pilot jet so I installed a #17.5.
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Re: UFO Installation & Test
Reply #4 - 04/11/20 at 02:32:52
 
Now that you have a leaner pilot jet installed, it’s time to drill the slide.  You use the drill guide to line up the hole location on the bottom of the slide.  A drill press is in needed for this operation.  Also note the soft copper strips between the jaws of the vice and the slide.  You don’t want to mar the slide surface.
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Slide_Drilling_Alignment_1_2.jpg

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Re: UFO Installation & Test
Reply #5 - 04/11/20 at 02:33:46
 
After the screw hole has been drilled through the bottom of the slide, turn it over and use a larger drill to make a countersink for the screw head.  The instructions provide all the details, including recommended drill sizes.  Always use the soft copper strips between the jaws of the vice and the slide.
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Re: UFO Installation & Test
Reply #6 - 04/11/20 at 02:35:03
 
The drilling is finished, install the UFO in the slide.  Use the screw to lock the UFO in place.  Make sure that the head of the screw is slightly below the surface of the slide.  If it sticks up, the slide needle won’t be captured properly, and your mid-range mixture might be erratic.
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Re: UFO Installation & Test
Reply #7 - 04/11/20 at 02:35:44
 
That’s all there is to the installation.  It’s time to put the carb back together, test air flow, and dial it in.
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UFO_Finished_2.jpg

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Re: UFO Installation & Test
Reply #8 - 04/11/20 at 02:36:42
 
On the poor man’s flow bench, the VM38 with UFO flowed 180 cfm @ 15” H2O.  The standard VM38 flowed 178 cfm, so looks like I picked up about 2 cfm.  It was time to run it.
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Re: UFO Installation & Test
Reply #9 - 04/11/20 at 02:38:06
 
It didn’t take long to figure out that TPI wasn’t kidding when they said you need a smaller pilot jet.  This thing was grossly rich at idle.  The air screw was completely ineffective.  I could hardly breath while the thing was running.  I’m not gonna go into all the gory details.
 
I tried all the smaller pilot jets (#15, #12.5, #10, and one plugged with epoxy).  The smaller pilots barely improved the over- rich idle.

Then, at the advice of Lancer and Lon, I drilled a hole in the needle jet hood.  Still too rich at idle.  
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Re: UFO Installation & Test
Reply #10 - 04/11/20 at 02:38:58
 
I shortened the needle jet hood in small increments, and eventually removed it all together.
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Re: UFO Installation & Test
Reply #11 - 04/11/20 at 02:39:46
 
I tried smaller needle jets all the way down to a P-4.
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Re: UFO Installation & Test
Reply #12 - 04/11/20 at 02:40:24
 
I tried larger main air bleeds.  All sorts of combinations of main air bleeds, pilot jets, main jets, needle jets, and slide-needle positions.  If you’re gonna get into one of these contraptions, you better have a good selection of jets.  That jet case that comes in Lancer’s kit is a sweet place to start, but you will have to add a few more jets if you plan to get serious.
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Re: UFO Installation & Test
Reply #13 - 04/11/20 at 02:41:26
 
Ultimately, I ended up with the following combination of jets.

PJ 15
MJ 260
NJ Q-2 with hood removed
Needle 6DP1
Clip bottom groove (max rich)
Air screw 2-5/8 turns
Main Air Bleed 0.5
Slide 3.5 with UFO

It ran very good except for idle.  The idle was OK but not perfect.  It was a bit erratic and couldn’t hold a speed setting.  Sometimes it would idle up to 1800 rpm or so, and other times it would idle too low.  You could back out on the stop screw and it would speed up (????).  Other than idle, it felt great.  I decided it was as good as I was ever gonna get it.
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Re: UFO Installation & Test
Reply #14 - 04/11/20 at 02:43:01
 
I did a series of runs with my GoPro zeroed in on the air/fuel (A/F) meter.  With the engine up to full operating temperature, I recorded A/F at idle, 2500 rpm level-cruise, 3500 rpm level-cruise, 4500 rpm level-cruise, 4000 rpm up a grade, and WOT 3rd gear all the way past 7000 rpm.

After reviewing the videos to verify that the A/F was optimized, I reconfigured the carburetor back to the baseline and did the same series of runs with the GoPro zeroed in on the A/F meter.

I repeated this test several times, back & forth (UFO, no UFO, etc.) until I was satisfied that the data was consistent & repeatable.  Note that it always developed the erratic idle in the UFO configuration, and always idled perfectly in the standard configuration.  The rich idle issue isn’t a loose/leaky manifold, it’s directly attributable to the UFO.

Here are the results of those tests.  The standard configuration and the UFO configuration were almost identical.  BTW, the higher the A/F number the leaner the mixture.  For instance, 12.0 represents 12.0:1 which is 12 parts air to 1-part fuel.
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AF_Ratio_Tests.jpg

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