Honda Grom banner
1 - 12 of 12 Posts

·
Registered
Joined
·
156 Posts
Discussion Starter · #1 ·
I picked up a spare stock air box for my 2020 Grom. I have both Koso tubes and DHM spacer. I’m going to mod the box and install it. Does anyone have this mod on an otherwise stock bike? What can I expect I specifically I am wondering about noise and if I will lose any low end torque. My plan is to do this first then if I like it to add the tb cam. I have it left over from a 2020 monkey I had. If I remember correctly I think the cam lost low /mid torque and woke up at higher RPM’s.
 

·
Registered
Joined
·
25 Posts
If you mod the standard airbox , benefits , might be incremental , but small.
Expect a very small amount of low RPM improvement.
Maybe a small incremental increase in induction noise.
But in doing so , your building the foundation , with other performance mods , to improve both power output & torque .
 

·
Registered
Joined
·
25 Posts
I picked up a spare stock air box for my 2020 Grom. I have both Koso tubes and DHM spacer. I’m going to mod the box and install it. Does anyone have this mod on an otherwise stock bike? What can I expect I specifically I am wondering about noise and if I will lose any low end torque. My plan is to do this first then if I like it to add the tb cam. I have it left over from a 2020 monkey I had. If I remember correctly I think the cam lost low /mid torque and woke up at higher RPM’s.

Depends on the spec & characteristics of your camshaft.
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #4 ·
Thanks. The air box is modded and back in the bike. I reset ecu and tps. Started right up and idles well. The induction noise is not much different from stock. I can live with it easily. I will try to get a ride in this weekend to see if I can notice any performance changes
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #6 ·
I removed the air box and used a dremmel with a sanding drum to enlarge the holes. It worked too well. If you mean how is it, I don’t know yet. Rain here. I haven’t had it off my street yet
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #7 ·
I finally got to check out the mod. 50 miles tonight. I want to be as accurate as possible for future readers that might consider this mod. My bike is stock except I am running 15/35 I added a tooth to the rear because there just wasn’t enough torque to get going with stock sprockets and I couldn’t pull 3rd gear past 8.25k, 4th was even worse and pulled to 7.5k max. I do have the 12oclock speedo healer installed and dialed in. I rode the same roads I’ve been riding for years and know what to expect from the setup before this mod. First let me comment on the noise. I hate induction noise and removed a chimera intake after a 5 minute ride because it was too loud. This was a pleasant surprise. Yes it is louder than stock but if you didn’t know what stock sounds like you wouldn’t know it was louder. I could hear it over my stock exhaust but the wind noise in my helmet was louder. About as loud as a cat purring vs not. I have no problem keeping this mod on for good. As mentioned earlier I am 1 tooth shorter than stock for a tiny bit more torque Below 5k. With this mod I would say I lost about half of that gain. I can live with it but may go up to 36 to get it back. I was able to pull 3rd gear to 9k @56 mph. That’s a little more than pre mod. Fourth was still below 8k but there was no loss of performance. My bike reliably gets me to 53 mph sitting straight up. If I need 55 I have to tuck. After the mod I was able to go 54 mph sitting up. That’s a huge improvement when I only hope to make small gains. Top speed in a tuck was 63. I haven’t tuned the ecu for this ride. I’m going to install a Tb cam next and get a stage 2 ecu tune. The cam will lose a bit of low end torque but wake up around 6k. By adding another tooth in the back i hope to compensate for the cam profile and I think I may be able to hit the limiter in 3rd and pull 4th higher. I don’t expect any more noise from the tune so this may be the 55 mph with staying power I’m looking for. Parts are on order.
 

·
Registered
Joined
·
25 Posts
I finally got to check out the mod. 50 miles tonight. I want to be as accurate as possible for future readers that might consider this mod. My bike is stock except I am running 15/35 I added a tooth to the rear because there just wasn’t enough torque to get going with stock sprockets and I couldn’t pull 3rd gear past 8.25k, 4th was even worse and pulled to 7.5k max. I do have the 12oclock speedo healer installed and dialed in. I rode the same roads I’ve been riding for years and know what to expect from the setup before this mod. First let me comment on the noise. I hate induction noise and removed a chimera intake after a 5 minute ride because it was too loud. This was a pleasant surprise. Yes it is louder than stock but if you didn’t know what stock sounds like you wouldn’t know it was louder. I could hear it over my stock exhaust but the wind noise in my helmet was louder. About as loud as a cat purring vs not. I have no problem keeping this mod on for good. As mentioned earlier I am 1 tooth shorter than stock for a tiny bit more torque Below 5k. With this mod I would say I lost about half of that gain. I can live with it but may go up to 36 to get it back. I was able to pull 3rd gear to 9k @56 mph. That’s a little more than pre mod. Fourth was still below 8k but there was no loss of performance. My bike reliably gets me to 53 mph sitting straight up. If I need 55 I have to tuck. After the mod I was able to go 54 mph sitting up. That’s a huge improvement when I only hope to make small gains. Top speed in a tuck was 63. I haven’t tuned the ecu for this ride. I’m going to install a Tb cam next and get a stage 2 ecu tune. The cam will lose a bit of low end torque but wake up around 6k. By adding another tooth in the back i hope to compensate for the cam profile and I think I may be able to hit the limiter in 3rd and pull 4th higher. I don’t expect any more noise from the tune so this may be the 55 mph with staying power I’m looking for. Parts are on order.
Great news , i have another bike , with air box removed , but the grom i want to keep that refinement.
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #9 ·
I did take the next step and installed the Tb cam and DHM ecu stage 2. 57 mph sitting upright wasn’t a problem and 3rd gear did 57 before the rev limiter so I do see the improvement with the cam and ecu but idle seems to hang up above 2k and I don’t like that. I’ve cleared and reset A few times but after 10 or 15 miles the idle issue pops back up. There is no annoying noise and I can feel a slight decrease in torque so if I keep this setup I will add a tooth to the rear I emailed David asking about the idle issue. I want to solve that first.
 

·
Registered
Joined
·
25 Posts
I did take the next step and installed the Tb cam and DHM ecu stage 2. 57 mph sitting upright wasn’t a problem and 3rd gear did 57 before the rev limiter so I do see the improvement with the cam and ecu but idle seems to hang up above 2k and I don’t like that. I’ve cleared and reset A few times but after 10 or 15 miles the idle issue pops back up. There is no annoying noise and I can feel a slight decrease in torque so if I keep this setup I will add a tooth to the rear I emailed David asking about the idle issue. I want to solve that first.
Defiantly some advantages to keeping the stock air box , its very water proof , keeps induction noise down to a minimum , it can , help improve torque & here in Spain its essential for the safety check every year.

The hanging idle , is certainly a pain , but I'm sure , some further calibration & consulting with David ( DHM ) will result in a better , settled idle.

Thanks for your feedback & lets hear about your final setting , cheers.
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #11 ·
Okay. David was helpful with the hanging idle issue. I had to adjust the plastic air/idle? Screw. I started with a half turn clockwise and it lowered my idle to 1k. The hanging idle disappeared but the idle was too low. I ended up going back clockwise a quarter turn and the idle settled in at 1400. I have done 2, 20 mile rides and it doesn’t hang up so that’s behind me. What I can say is I’ve lost some more torque in the lower rpm’s and I still can’t pull 4th past 8k. I can hit and hold 55 on a flat road without tucking so there is improvement. I’m going to change the rear sprocket from a 35 to a 36. That will help with the low end torque and also help 4th gear pull past 8k. I don’t think it will make the bike faster but it should feel better. I may ride it a few more times before the swap just to get a better feel for it first
 
1 - 12 of 12 Posts
Top