Another Air Filter Option
Post Reply    Forum -> Project Reports
Author Message
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 182
Location: California
Mon Mar 11, 2019 8:45 pm quote
FYI: The Uni filter 6245ST will fit over the OEM intake tube without trimming (Filter is 63mm I.D. x 152mm Long). The only fabrication needed is to make a spacer "ring" for the new filter to have something to tighten down onto, as the OEM tube is not rigid. The OEM tube has a nice flare at the end which is in about the middle portion of the filter.

I have not ridden with this yet, so I am unsure of the performance gain/loss. I was previously running a straight pod filter at the end of the throttle body, but was not happy with the cables & wires rubbing on the filter. This appears to be a much better setup, as the filter is not only larger, but should be able to get more cool air from outside.

https://www.amazon.com/gp/product/B000WJFFUO/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

IMG_20190311_174002.jpg

Addicted
GTS 300 Super
Joined: 13 Sep 2017
Posts: 734
Location: West Sacramento, CA
Wed Mar 13, 2019 8:06 am quote
Interesting.

Look forward to the follow up on gain/loss or any other pending issue/performance of this mod!
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 182
Location: California
Fri Mar 15, 2019 7:43 am quote
Here's a few more pictures. I used 2.25" OD aluminum tubing for the spacer ring.

IMG_20190314_172127.jpg
The intake tube flare is roughly in the center of the filter. The ring is not in it's final location, and will sit flush with the rubber flap when complete.

IMG_20190314_173839.jpg
The ring in it's final position

Ossessionato
Joined: 22 Oct 2011
Posts: 3815
Location: Tega Cay, SC
Fri Mar 15, 2019 4:47 pm quote
Keep an eye on the color of your spark plug as this may cause it to run lean. Most motorcycle engines need a re-map or a power commander when any changes are made to the intake side, the exhaust side, not so much.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 182
Location: California
Fri Mar 15, 2019 7:33 pm quote
Sacto Monkeyboy wrote:
Look forward to the follow up on gain/loss or any other pending issue/performance of this mod!
Unfortunately, I have made way too many changes to be able to tell if it's faster or why. I can say that the sound is different than with a pod filter... you can hear more of a hollow tube sound. It might be louder outside the bike, as the pod filter was muffled by being under the seat & pet carrier.
Tierney wrote:
Keep an eye on the color of your spark plug as this may cause it to run lean. Most motorcycle engines need a re-map or a power commander when any changes are made to the intake side, the exhaust side, not so much.
I am currently running a MP3 400 fuel injector, but do suspect that it might be somewhat lean. My stainless PM-80 exhaust is turning colors... I have been thinking about getting a wideband O2 sensor, but am still somewhat new to that world. This is the one I am leaning ( ) towards: https://www.plxdevices.com/Wideband-O2-Air-Fuel-Ratio-Sensor-Module-p/897346002726.htm



As a side note, I wonder if anyone has had any success with tuning the intake length. An interesting calculator I have been playing around with: http://www.velocity-of-sound.com/velocity_of_sound/calculator3.htm
Hooked
ET4 187
Joined: 14 Mar 2017
Posts: 323
Location: Germany
Sat Mar 16, 2019 8:45 pm quote
I enjoy seeing a clean motor compartment on a scooter!

The setup looks great, but I'm not so sure without flow measuring and engine tuning software of reaching success here. This is a very sensitive area.

The velocity software, intake runner length and harmonics is the way to proceed. The NASCAR guys are absolute top of the list tuners.

On another thread, a similar setup would need an extended intake runner to the head, like in the neighborhood of a 10" extension....!!

I believe as well, the exhaust should be modified to match. What goes in, must come out.

Several articles later on, I've gathered the filter, some guys use cones, has to blocked off by around 50%, as the air intake is just too extreme to let the motor thrive.

Good luck with your endeavor. I'd love to read some positive things coming out.
Molto Verboso
Kymco AK550
Joined: 09 Feb 2008
Posts: 1059
Location: UK
Sun Mar 17, 2019 1:07 am quote
It is a common myth that an air filter with less resistance to flow will work correctly if the mixture can be made richer to match the extra air flow. In practice this never works because it is the resonance of the intake tract that has been destroyed and this has to work sympathetically with the inlet valve timing across the entire rev range. Intake air flow, especially with a single cylinder engine, is dependant on the design of the air filter housing ( plenum chamber ), the length of the inlet tract, and the camshaft profile.
Because scooters with continuously variable transmission often operate over a relatively small rev range it is possible to improve performance by changing the effective intake length or diameter by placing a can over the air filter or by reducing the intake area with some form of restrictor. The only way to be sure that adjustments are taking things in the right direction is by performance testing done in a repeatable way. I used to do a lot of this using GPS tracking over a consistent test route.
With experience it is also possible to gain some insight by listening to the changes to the engine note. There is a certain flat sound which says the engine is not pulling properly and conversely a crisp note answering the throttle indicating that intake timing is good.
Hooked
ET4 187
Joined: 14 Mar 2017
Posts: 323
Location: Germany
Sun Mar 17, 2019 10:17 am quote
Hi roadster, excellent post.

As I understand, maintaining or even raising air/fuel velocity is the key. The larger air intake volume without adjusting the remaining sectors, intake manifold and cylinder head port/valve dimension, would adversely affect port velocity.

For instance, porting a valve chamber to what appears to be more volume, by no means guarantees the head flow works more efficiently. These changes need to be constantly monitored for advanced flow behavior.

I'd like to find out what the best air intake and intake runner length would be, without changing cam or head dimensions, for instance using a flat slider "racing" carb, instead of a vacuum, standard carb.

Keep up the good work AnnDee4444, an interesting topic.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 182
Location: California
Mon Mar 18, 2019 9:41 am quote
roadster wrote:
It is a common myth that an air filter with less resistance to flow will work correctly if the mixture can be made richer to match the extra air flow. In practice this never works because it is the resonance of the intake tract that has been destroyed and this has to work sympathetically with the inlet valve timing across the entire rev range.
I have a Polini cam, so I am willing to bet that the OEM intake is no longer tuned for the ideal RPM (whatever that may have been). As far as I know, the 200, 250, & 300 all have the same intake box/tube but use different camshafts... so I doubt the factory even considered intake length.
MichaelG wrote:
On another thread, a similar setup would need an extended intake runner to the head, like in the neighborhood of a 10" extension....!!
Playing with the calculator above, ff you are designing for the first wave the intake valve to tube opening distance would need to be around 35" long (8,500 RPM target). The filter would end up down by the brake caliper . Second wave would be a more reasonable 17".
Hooked
ET4 187
Joined: 14 Mar 2017
Posts: 323
Location: Germany
Tue Mar 19, 2019 6:43 am quote
Yes, I believe what you're looking for performance wise is the 3rd harmonic, about 11" at 8500 rpm.

I'd start from there.

Maybe better yet, start longer and keep shortening till you hit a sweet spot. Still a huge amount of air coming in though.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 182
Location: California
Mon Apr 22, 2019 5:22 pm quote
AnnDee4444 wrote:
Tierney wrote:
Keep an eye on the color of your spark plug as this may cause it to run lean. Most motorcycle engines need a re-map or a power commander when any changes are made to the intake side, the exhaust side, not so much.
I am currently running a MP3 400 fuel injector, but do suspect that it might be somewhat lean. My stainless PM-80 exhaust is turning colors... I have been thinking about getting a wideband O2 sensor, but am still somewhat new to that world. This is the one I am leaning ( ) towards: https://www.plxdevices.com/Wideband-O2-Air-Fuel-Ratio-Sensor-Module-p/897346002726.htm]
With the help of http://modernvespa.com/forum/post2316033#2316033
I read the ECU today and found that even with many airflow mods, the MP3 400 injector is way too large at idle for the stock map. The fuel correction would peg itself at 25%, and still read rich. Some slight throttle stabs would get it back to normal range, but without a way of dynologging I can't accurately determine what is happening under load.

Also the motor can't reach target idle RPM, which I suspected since the decompression weight keeps bouncing around (this is with a Polini cam).


I know this is a long shot, but does anyone have an .XDF file for the MIU1 or any other factory tunes?
Missouri Loves Company Rally   vespa scooterwest scooter west Motorsport Scooters   Cool Ass scooter seat cover
Post Reply    Forum -> Project Reports
[ Time: 0.2669s ][ Queries: 25 (0.0591s) ][ Debug on ]