New M50 airbox mod

[diamond_jim]

I modded the airbox by making it smaller and cutting out a plate for it. I recontoured the back part of the airbox and mounted the new air filter. I used the two front existing screw holes and holes for mounting the plate. The air filter was $15.99 at Autozone. I had been wanting to try this before I bought a hypercharger.

[phil.dye]

Originally Posted by diamond_jim

I modded the airbox by making it smaller and cutting out a plate for it. I recontoured the back part of the airbox and mounted the new air filter. I used the two front existing screw holes and holes for mounting the plate. The air filter was $15.99 at Autozone. I had been wanting to try this before I bought a hypercharger.

Attachment 13105Attachment 13106Attachment 13107

Do you notice any difference in engine performance since making this mod?

Thanks,
Phil

[diamond_jim]

Originally Posted by phil.dye

Do you notice any difference in engine performance since making this mod?

Thanks,
Phil

Not yet, but I've only ridden about 15 miles with it. I'm thinking the trick is that it's still using the stock airbox. The airbox has a good bit to do with performance. I was reading reviews the other day about Honda Shadows and how performance had dropped because the airbox hhad been significantly downsized as compared to prior years for asthetic reasons. I'm wondering if with the stock airbox and the fact that M50s run a little rich already when stock, that it will work fine without a fuel processor. I do know that I still smell a little gas which is a sign that it may still be a little rich even with the new air filter. Anyhow, I'll post further findings.

I also know that the inside of my right knee no longer bumps up against the intake like it did with the larger stock airbox cover.

[SNAFU]

Looks good d j.

[chinard]

you have a PCIII on there yet?
i can see this mod really leaning out your engine maybe a little too much with the debaffle/demickey combo.

[diamond_jim]

Originally Posted by chinard

you have a PCIII on there yet?
i can see this mod really leaning out your engine maybe a little too much with the debaffle/demickey combo.

I'm kind of concerned about that. I haven't ridden much with it on yet. I am curious to see what difference this setup makes without and then with a PCIII.

[Alex13]

Looks good. You need a award for the most mods and least amount of money spent!

[chinard]

well if you arent sure, dont ride it too hard and check your plugs regularly to make sure you arent doing noticable damage. If it looks overly white or even worse pitted then you should stop otherwise you might damage to your valves.
I think it would be amusing to see just how much of a difference changing the air filter cover would make considering how naturally rich most v-twins natively run.
The main thing is that you are leaving the airbox pretty much intact which is where it appears that the majority of backpressure is happening.
Of course this comes from years of tinkering on carburated bikes . Many tuning techniques for those engines would be considered downright barbaric as opposed to these new-fangled fuel injection systems.

[diamond_jim]

I will be checking it. Thanks for the info.

I just came across this:
"Relocate IAT Sensor - This is a very simple modification that will work on a great deal of fuel injected vehicles. The IAT sensor (“Intake Air Temperature”) tells the computer how hot or cold the incoming air is. The computer will then adjust the amount of fuel being injected, as well as make minor adjustments to timing based on that reading.

The problem is that in many vehicles, the IAT sensor is located in the intake manifold, near the cylinder head. Therefore the air that the IAT sensor “reads” is much hotter than the air, say, in the intake arm. The idea with this mod, is to relocate the sensor to the intake arm. Use JB Weld or similar to patch up the old port for the sensor.

This will cause the computer to believe that incoming air is slightly cooler, causing it to inject more fuel and advance the timing a tad."

What do you think about it?

BTW, I just finished priming and painting the airbox flat black. It looks much better now than in the initial pics. The airbox kind of vanishes more. I'll post some more pics soon.

[chinard]

i seem to remember hearing something about that cold air sensor. Its a pretty common trick with FI systems to coax a bit more hp out of an engine with simple intake/exhaust mods. If it helps richen the fuel mixture a bit i could really only see it as a good thing from this point.

I seriously doubt that the intake and exhaust mods you've done would lean out the mixture to the point where you would be at any serious risk of damage. Even if you were at risk it would be over a very long period of exposure... like months of hard driving on a lean mixture will wear out your valves pretty fast.

Reading spark plugs are far from accurate but they will tell you when something is seriously wrong. The colour you are most aiming for would be very light beige.
To get more accurate you really have to be using something like the colourtune system that i was using for my CB750 (dohc 4 cyl). Its actually a pretty cool system, it has special glass spark plugs with a periscope so you can actually see the colour INSIDE the combustion chamber.
It sounds funny but its a hell of a lot cheaper and more convenient than going to a dyno shop every time you mod your bike.

of course standard disclaimers here.. FI bikes are new territory for me so take my advice with a grain of salt

[diamond_jim]

If it is too lean, would an airflow restrictor plate help?

[chiefriceburner]

if you call a dyno shop they will do a simple run on a dyno for about $45 and give you the results.

[diamond_jim]

Here's some more pics after prepping, priming and painting the airbox flat black.



I'll ride my bike to work and around today and give feedback this evening.

[diamond_jim]

I rode some this morning with the new airbox and noticed two things.

1. It seems like there is a little bit of low end torque loss when you start from a stopped position. I'm guessing a 10% loss. This is likely some power loss from running a little lean. It feels like the torque doesn't really kick in until about 400-500 rpms later than it did with the stock airbox. I didn't ride too long or too hard.

2. It's got more pep on the high end. When cruising at 60mph and then rolling on the throttle, it pulls maybe 10% harder.

My guess is that it shifted, or advanced, the torque curve a little. I'm sure the stock airbox is a compromise to allow more torque at low speeds yet breathe enough for high speeds. I'll let the smart ones, like Clint, figure it out and explain it to the rest of us.

Anyhow, I'm gonna experiment with a restrictor plate. I'm starting off with a 1" hole. After some riding, I'll open it up to 1.25" and ride and so on.

Here's some pics of the airbox off and installing the restrictor plate. Each time I take it apart and do something, I wipe it down and then blow everything off with compressed air. Gotta keep it clean!

[chinard]

yeah restrictor plate makes sense.
its always safer to run too rich than it is to run too lean.

[Mario]

Keep it up and thanks for the pics <thinking.. I could do that>

[diamond_jim]

Wow! I don't know exactly how it worked, but the 1" restrictor plate made a big difference. It feels like the bike has more power across the whole rpm range now than it did with the stock airbox and debaffled stock pipes. I usually figure that to feel a noticable difference there's got to be at least a 10% change. Well it's definitely got a noticable increase in low end torque comapred to stock and still has the 5th gear roll on power that I discovered prior to adding the restrictor plate.

I must admit that it feels kind of stupid to have this open, easy breathing air cleaner and then a restrictor plate with only a 1" hole. It seems like it would defeat the purpose. But it works. I'm not messing with this restictor plate. Oh no. I'll make a new plate and play with the sizes but this 1" puppy ain't getting touched!.

It's almost like the stock setup has been reversed. In the stock, you have a 1.25" hole in the cover for air entry and then the filter. With my mod, it's air filter first then a 1" hole.

I have some ideas, but somebody explain to me why the 1" restrictor plate makes such a big difference.

[chinard]

I am imagining that the smaller-than-stock opening is acting just like a choke.
I bet your idle is higher than it usually is as well due to the richer mixture.

i think what you are feeling there is some of the power restored by a more balanced fuel mixture.
These bikes run naturally rich to begin with. Debaffling and demickey reduced some exhaust backpressure which leaned the mixture out a little, then the airbox mod leaned out out even more.

Of course without that restrictor you would need something like a PCIII to increase the amount of fuel delivered to match the increased amount of air being delivered by the intake/exhaust mods. This of course is where you really start to see the performance benefit once you get the settings right.

[m50riderga]

Nice work, looks damn good.

[diamond_jim]

Originally Posted by chinard

I am imagining that the smaller-than-stock opening is acting just like a choke.
I bet your idle is higher than it usually is as well due to the richer mixture.

i think what you are feeling there is some of the power restored by a more balanced fuel mixture.
These bikes run naturally rich to begin with. Debaffling and demickey reduced some exhaust backpressure which leaned the mixture out a little, then the airbox mod leaned out out even more.

Of course without that restrictor you would need something like a PCIII to increase the amount of fuel delivered to match the increased amount of air being delivered by the intake/exhaust mods. This of course is where you really start to see the performance benefit once you get the settings right.

It's got a noticeable increase in power over the stock airbox with no holes or mods. I take the same route to work everyday and that's the same route I took today both with the inital setup and with the restrictor plate. So I'm familiar with where I accelerate, where I shift, etc. I could clearly tell the power loss on the low end when I first put it on. Likewise, I could tell the power increase over stock after putting the restrictor plate in. It's one of those routes that you drive everyday to the point that you could do it with your eyes closed and you know how the bike accelerates and handles.

I'm wondering if, even with the restrictor plate, if there's just a little bit more air available to the engine since the filter is open to the air and thus the wind and it's taking advantage of the slightly rich stock fuel settings. Maybe there is greater air velocity through the intake. I figured it would restore the low end torque but then reduce high end performance due to the restrictor hole size. It didn't seem to reduce high end as compared to a non-restricted modded airbox. I'm gonna run it like this for a day or two and then try a different size restrictor plate and also try moving the restrictor hole around to see how it reacts.

The ultimate would be no restrictor plate, add a PCIII and some dyno runs to calibrate it. I'm not sure which existing map would be the closest for a starting point for tuning though.