Let the Testing Begin - Air Box Mod

Byron

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As someone who just can't seem to leave well enough alone I modified something else on my bike, the air box. It started out as just a trip to Turbo City to see Tom about exchanging my FPR because I changed something else on the bike, added Staintunes, after installing the FPR with no intention of adding the mufflers. Anyway, while talking to Tom another moment of weakness hit me and I bought the kit from Tom.

Since I was adding this to provide more air to the engine when it needed it I opted to tweak the mod a little myself. While the options I have seen included openings cut on both sides of the front, holes drilled on both sides of the front, I chose to cut openings on both sides AND the middle (see attachments).

Now Tom felt that the center area would be blocked by the front tank mount but if you look at the pictures you will see that there is a pretty good gap between the air box lid and the frame. The :06biker: can now feed at will on all the air it should need without being restricted in any way.

Well I ran out to Arizona and back on Saturday, after installing the modified air box top Friday night. Here are some of my initial observations. Mind you some of this could be related to my switching of the FPR from a 59 to a 61 psi unit; which kind of began this whole thing in the first place. Since the two changes were done at the same time it is had to seperate the affects. Let me also say that the reason I was bumping up the FPR was because after adding the Staintunes it seemed like some of the low end abruptness in throttle response had returned. Anyway, no more low end throttle abruptness on the trip. Back to being smoother off the line and the ability to be in higher gear at low speed. I actually equate this to the FPF.

Now since I was going some distance I mostly just set the cruise control once on the freeway and enjoyed the scenery along the way. Did I mention that I'm only about 3 blocks from the freeway :). I did have a few instances were I needed to call on the bike's HP to help me pass lumbering 18 wheelers. Some of what I noticed was that it was very smooth and quick from 75 to 95 and never a hint of strain.

I should mention that Tom reported that others have noted that you pick up more engine noise with the top of the air box opened. As for me, I was always one of those that loved the sound when you stepped down on the gas and those back two barrels would open up while at the same time you watched the needle on your gas gauge also going down :D. Well now I have a bike with Staintunes, a 61 psi FPR and an airbox lid that looks like it has a grin from the cheshire cat. Come to think of it I think I have that same grin myself now.

Like the muffles, when you give it the command they report back by making a little extra noise to let you know they are doing their part. Well, you are also picking up a little extra noise from the intake of the bike letting you know that it is doing its' job as well. I think it is music to my ears. Now before I scare some of you off because you're thinking that your bike is going to sound like a boom-box all the time, it's not. At general cruise levels you probably won't hear much if any difference, but maybe a little. Like I mentioned about the 4 barrels, it's only really there when you're flexing the bikes muscles. Cruising the freeway I didn't notice anything but the normal noise from the wind.

This is only one days worth of riding and one type of driving, straight open highway. That's why I labeled this the way I did because there are lots of other types of roads and driving I need to put this trough before I reach a final decision on the mod. However, my initial impression is favorable :D .
 

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Quote by Byron
I should mention that Tom reported that others have noted that you pick up more engine noise with the top of the air box opened. As for me, I was always one of those that loved the sound when you stepped down on the gas and those back two barrels would open up while at the same time you watched the needle on your gas gauge also going down

How could I possibly have known that you like the noise?:) When I was working on a race car, we had a hard and fast truism.
AIR IN + AIR OUT = HORSEPOWER
Sounds to me like you are folowing the rules. I'll be following your test results with great interest.

A good Saturday night. Is always good to go to a car show with a gear head. Always.
 
So now you don't have an air filter? Looks like those holes would bypass the air filter.
 
sport_tourer said:
+1 on that....the way the ST1300 filters air is from the air coming up INSIDE the filter and then the filtered air flowing into the throttlebodies...sure looks like what you did was simply cut holes in the top cover, thereby bypassing the filter.....unless those holes are leading to the INSIDE of the filter...maybe I am wrong but it doesnt look like you are getting filtered air.

There is a plate sealed into the top of the air box. Air enters the top and the bottom of the air filter (modified). NO unfiltered air enters the engine.

Thanks Tom
 
Well, riding to work this moring I was sort of shocked. I didn't hear anything different than before the mod. Then it dawned on me, I had the shield down all the way like I normally ride. When I went to AZ I had the shield up a couple of inches which quiets the noise from wind some. With the shield up and getting on the freeway or grabbing a little more throttle for a pass you could hear the intake.

O.K., now I gots to know where is there a motorcycle dyno in So. Cal? Either that or I'm going to have to try and make a bracket night at Irwindale.

I do have to say that my bike is really running sweet right now.
 
Well, it has been a couple of days riding with the mod now and all I can say is, I don't think that there is anything else that can or needs to be done with anything connected to the engine of this bike now.

Without having anything to compare it to I have no way of giving meaning full numbers or imperical proof as to what the air box mod has done for the bike. As to noise, it is only when you are telling it "get me there now" that you hear the engine/pipes speaking to you saying "you got it!"

As I previously stated the bike is running so sweet now. I have had it in the canyons and on the freeways and it is performing flawlessly. I won't say it is the fastest ST out there but I've been to a new high for me. Lets just say that it has been beyond double legal limit and not maxed out that I know of :D.

I generally ride at about 75 mph on the freeway. To pass a vehicle from that speed I'm at 95 in no time and with no effort. When you're cruising I don't notice any difference in noise.

I talked to Tom about the gap that was mentioned at both sides, which mine had, and he said that is already being addressed. He said he had already looked into it once reported.

Here is my take todate. Is this a needed mod? Not unless you're wanting to get the most out of what the bike has to offer. Is the cost of the mod worth it? I was to me. I've always been a horsepower kind of guy :D. Where is it most effective? I would have to say at the upper end, when the motor is wanting as much air as it can have. If you're running a paper filter I don't think the mod will work as well. With the K&N type gauze filters you will get the best bang for the buck, no restrictions. I haven't had it out in the rain yet but I don't think that it will be a problem. It is covered by the tank on top and the frame in front with the faring infront of that. At worse, the water would simply drop into the lower pickup which is vented at the bottom to allow moisture and fine dirt to fall out.

You won't find this one in the classifieds.
 
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I don't think there is room. Take another look at the last attachment from my first post. Even though there is a gap around the front of the air box the tank come down right on top the frame so no room for an air duct there. The bottom duct fills the opening under the frame and above the radiator. I don't know where you could pick up the fresh air and how you would get it to the top front of the air box.

Got any ideas?
 
If you do some test riding, you will find that that area between the frame and the tank is an area of very cool air. Ride carefully about 70 mph and place an ungloved hand around the front of the tank. You will find that it is a higher pressure area and is surprisingly cool. I do not think that you will find any more gains by ducting air from any place else.

Thanks Tom
 
Several guys have done this type of mod on ST1100's over the years and have not been able to see a discernible difference when actual dyno testing was done. One guy documented, with dyno testing at each combination, all kinds of air in/air out mods with various combinations of air box drilling, re-jetting, different air cleaners, different exhaust setups, and essentially found out that the stock setup was the best.

It'll be interesting to see if your actual dyno results indicate any increase in HP on the fuel-injected ST1300.
 
Don-STOC237 said:
Several guys have done this type of mod on ST1100's over the years and have not been able to see a discernible difference when actual dyno testing was done. One guy documented, with dyno testing at each combination, all kinds of air in/air out mods with various combinations of air box drilling, re-jetting, different air cleaners, different exhaust setups, and essentially found out that the stock setup was the best.

It'll be interesting to see if your actual dyno results indicate any increase in HP on the fuel-injected ST1300.

I don't think you will see much difference on a dyno, maybe 2-5 HP. The biggest difference is how the engine transistions in rpm, faster/free'er. That type gain is hard to measure.

A very good test would be to run a stock and modified ST side by side, from 50-100 mph. Average several runs and look at the results. Does anyone have the time and the space on thier drivers licence to take on the chalenge for us?

Thanks Tom
 
^^^^

I don't think it would be a good test, too many variables with two different bikes, two different riders, etc. And on the first point, any seat-of-the-pants impressions about smoother rpm transitions can vary, a lot, from day-to-day and ride-to-ride.

I'd be real surprised if this type modification will be worth the effort, unless you count placebo effect.

Why not just put one of your turbos on it and see a real difference? :D :D :D
 
Don,

I understand your doubts about what is gained. As Tom as stated true HP is probably small. MuleSkinner has stated that he thought there was no differenct above 130. I can't fault him because those are his observations for his setup. The only other testing I can think of are timed runs from a set speed to a second set speed. However, because of the many variables it will take lots of numbers to find true meaning statistically.

I'll offer you this; anyone that is serious about wanting to see if there is any difference is welcome to take my bike for a short run. The only caveat is you break it you pay for it. I'm not talking about 0 to redline in every gear till the rev limiter kicks in type of test, I'm talking about typical passing maneuver stuff.

I haven't checked with Irwindale yet to see what the equipment requirements are for motorcycle runs but I'm going to check. The only thing is their track is 1/8 mile unless things have changed recently and this type of mod is more mid to top end related so don't know if 1/8 mile will show. At least they can measure reaction times, top speed and elapsed time :). If your not looking for every last ounce of power you probably don't need this. Hell, I didn't need it I just wanted to give it a try and see.
 
Has anyone installed Turbo Tom's Air box Mod since this last post? I bought one but now am having second thoughts about installing it after reading this. Any updates would be appreciated. ;)
 
I'm still thinking about doing this. It just strikes me how small the air inlet is at the front of the ST VS the throttle body diameter X4.

The air inlet on my KLX650C is bigger as it was on the XR650L. I made them even bigger when I did the jetting changes.
 
I once let my mind wander and it came back with a scheme to fit the air pump from a vacuum cleaner into the airbox, powering it off the battery / alternator.

I sometimes wonder if it would add more power than it drained...

Cheers & God bless
Sam "SammyTheSnake" Penny
 
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