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Discussion Starter · #1 ·
As promised I have made a full video tutorial for you showing how to modify our airboxes. Most of you know I run my DodgeRider26 youtube channel, but I also have another channel I've created solely for technical videos, tutorials, maintenance, etc. I wanted to keep the two types of content separate. Any future Grom tech video I make will be uploaded to my MotorcycleProjects channel and my riding videos will continue to be on DodgeRider26.

The purpose of this mod is to remove the factory restrictions on our airbox and retain a stock appearance and functionality, yet increase torque and HP. I've noticed a change in part throttle acceleration across the RPM range indicating an increase in torque, as well as a top speed increase of 2mph indicating a gain in peak HP as well. Along with the power increase this mod will increase the sound of your intake on the bike which makes it feel faster and more enjoyable to ride. If you want to keep the intake as quiet as possible then only remove the air filter screen and the internal airbox snorkel.

Wander over to the video for full instruction!

[ame=http://www.youtube.com/watch?v=6iPJ7iQlGIo]Honda Grom/MSX Airbox Mod (Free) - YouTube[/ame]
 

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Amazing! This is likely the best video DIY I have ever seen! I think I'm gonna hafta go do this to my grom today
 

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I did this today and weighed the two snorkels air filter screen and little metal clip. They were 167.5 grams total. Not a whole lot of weight savings but ever bit helps.
 

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Very well done indeed. I'll be doing the custom filter as well, and probably drilling the holes and leaving the snorkel on. Is the snorkel a soft rubber? I'm wondering if it could be heated and expanded to give it more frontal area.
 

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Dodgerider26 is doing a great job with all the video demonstrations. This DIY is the best one I have seen in a while, very detail and thorough. Thanks for taking the time and making this video ;)
 

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How much pressure do you need in that air box?

Im wondering if opening up that whole front filter panel with holes right in front of the filter would help for air flow?

Stew
 

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could you widen that snorkel inlet hole to force a little more cool air down into the airbox? Also have you given the Grom a boot on the freeway after modding the airbox? Interested in how it behaves at highway speeds...
 

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could you widen that snorkel inlet hole to force a little more cool air down into the airbox? Also have you given the Grom a boot on the freeway after modding the airbox? Interested in how it behaves at highway speeds...
Yeah i would love to see a video of it in action on the highway or just going at a higher speed just to hear how different it would sound, not sure how much of a difference this would make.
 

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I did this mod tonight...

I first went to a long stretch of road around the corner from my house. I started at a certain mailbox, shifted each time at at 7k rpm, when I hit 4th gear I tucked my head down. I made 2 runs exactly the same. 58 mph when I reached my first point then 56 when I reached the second which is slightly uphill.

I did the mod which took about 30 minutes then did 2 runs again.

59 mph and 57 mph. So 1 MPH gain with a pretty consistent test IMHO.

I didn't think I really gained anything on the bottom but maybe. If so, it's not much. I thought I would like the intake noise but I found it to be annoying. (Maybe I was just annoyed) So I went back and threw the external airbox snorkel back on and did the runs again.

59 mph and 57 mph and nearly as quiet as before doing anything. I guess it was worth it because it was so easy to do and free but I was really hoping for 3 mph.
 

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I did this mod tonight...

I first went to a long stretch of road around the corner from my house. I started at a certain mailbox, shifted each time at at 7k rpm, when I hit 4th gear I tucked my head down. I made 2 runs exactly the same. 58 mph when I reached my first point then 56 when I reached the second which is slightly uphill.

I did the mod which took about 30 minutes then did 2 runs again.

59 mph and 57 mph. So 1 MPH gain with a pretty consistent test IMHO.

I didn't think I really gained anything on the bottom but maybe. If so, it's not much. I thought I would like the intake noise but I found it to be annoying. (Maybe I was just annoyed) So I went back and threw the external airbox snorkel back on and did the runs again.

59 mph and 57 mph and nearly as quiet as before doing anything. I guess it was worth it because it was so easy to do and free but I was really hoping for 3 mph.
not what i was expecting to hear but im also not surprised, maybe we'll have better luck with an aftermarket setup?

would you be able to film it on idle and a bit through the revs just so we can hear how it sounds? maybe it wont be annoying to some of us
 

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not what i was expecting to hear but im also not surprised, maybe we'll have better luck with an aftermarket setup?

would you be able to film it on idle and a bit through the revs just so we can hear how it sounds? maybe it wont be annoying to some of us
It wasn't really that bad. It just felt fake to me. Like flipping the air cleaner lid on a 2 barrel 305 Chevy with 150k miles on it. Lot's of noise about nothing.

I think most of the sound increase came from popping the external snorkel off. You can do this by just removing the side cover and wiggling it off.
 

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Discussion Starter · #18 ·
It wasn't really that bad. It just felt fake to me.
That pretty much sums it up. This mod does increase power, but it makes a lot more sound than it does extra power so it feels like mostly a cosmetic/aesthetic kind of mod. The fact we get more power is why we do it, but the sound is just there to make it "feel" faster than it is. With all the extra sound I certainly enjoy riding mine more even though I know it's only slightly faster than it was before. Plus it really helps me maintain a cruising speed now that I can hear the engine running. Before it was so quiet I kept speeding because I couldn't maintain a specific RPM without looking down to check my speed/tach.
 

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How bad does this screw with the airflow into the GROMs engine though, I know its possible to jangle the HP and change the torque curve adversely.

If the airbox is not designed to be force fed air then you will screw it all up as the air flow inside the airbox is not smooth as it was designed.

This throws all the fuel air maps out the window and a completely new set would be required. That is not small task because the air in the airbox would not be a known or even predictable quantity...
 

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Discussion Starter · #20 ·
Two questions deserve 2 answers...

1) Yes, the snorkels are both a very supple rubber material which you can easily bend/flex. Only the hard elbow on the internal snorkel is made of a dense plastic.

2) How much does this screw with the airflow? Very little. Removing only the restrictive part of the internal snorkel still leaves roughly 4-5" of smoother airflow piping before the throttle plate. After the throttle plate there are another couple of inches into the motor. All in all, this shouldn't affect airflow in a negative way. The reason you asked this question is probably because of your knowledge/familiarity with car intake systems.

In a car, the intake typically measures air using a MAF/MAS sensor. Essentially, this is a heated wire that is cooled off by incoming air. The computer uses the amount of cooling on this wire to determine how much air flowed into the engine. It's a very precise setup and changing any one piece of the intake can have seriously negative consequences throwing off your entire fuel mapping. Fortunately, car ECUs (computers) learn over time and self adjust for this so long as the new intake setup still allows smooth airflow over the MAF/MAS.

In our Groms airflow isn't measured directly. The ECU has a fuel map set up for the known amount of airflow based on engine load, RPM, and throttle position. This mod increases the airflow and our ECU must compensate for this which is why it's recommended you ride around awhile to let it adjust. Without a MAF/MAS like a car has we are much less sensitive to turbulent airflow in our intake pathways.
 
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