Airbox mod?

[fizzer6hundred]

Has anyone determined if the flow from the top air-box filter cover is at all restrictive? I have found on my cars via dyno that there are a lot of gains with a good flow filter and set up of the air intake. I can easily think of a mod that removes the intake cover with the four screws and the right angle intake to a modified simple 4 screw hold down ring all open around the center of the air filter. Seems like that would be the least restrictive and would only be a temporary mod I can try and use if it works better.

Anybody made any gains here with the airbox input port side?

[yamaha_george]

Has anyone determined if the flow from the top air-box filter cover is at all restrictive? I have found on my cars via dyno that there are a lot of gains with a good flow filter and set up of the air intake. I can easily think of a mod that removes the intake cover with the four screws and the right angle intake to a modified simple 4 screw hold down ring all open around the center of the air filter. Seems like that would be the least restrictive and would only be a temporary mod I can try and use if it works better.

Anybody made any gains here with the airbox input port side?

I do not know of anyone ever posting a mod with a view to a better Dyno reading for their engine.except for swapping the OEM filter for a K &N replacement and while these filters do flow more air I never actually saw someone doing a before & after dyno. sheet.

So go for it since you have done this with auto's and been able to use a Dyno to prove or disprove atheory.

[KaMaKaZeE_FZR1]

I took the snorkel on the top of the airbox and removed the center plenum and opend the snorkel slightly to allow for more airflow. I found a write up on the net for this mod but they didnt give any dyno readings but it did help flow better. I also debated a restrictor plate on the top of the snorkel to allow extra air flow but I have yet to do it, even bought an extra airbox to experiment on. Keep posted and post up some pics so we can see how you did it. My idea was more like a bath tub drain with staggered holes so the more you open it, the more it would allow for airflow.

[apsolus]

back when i was trying to dial in my carbs i ran with the airbox lid off and secured the filter with duct tape. no noticable increase were noticed. in my opinionid leave everything alone. on that note i watched two identical acura rsx on the dyno the bone stock on pulled 170hp the one with the so called intake mod made 144hp. the only way an intake mod will help you is if the engine needs the air, if the heads cant flow the increase in potential airflow the mod will kill intake velocity,

[fizzer6hundred]

I changed my air cleaner and snorkel air box from stock and put a low restriction filter and no snorkel on my corvette and dynoed it and had a 38 HP difference. I swa the actual air flow change and there was enough water vapor in the air to see it condense at high RPM's. This helped me visualize what was different in the actual air flow like a smoke stream in a wind tunnel. What I learned is that the shape and quality of the stack into the carb is HUGE in terms of power at high RPM (i.e, in the power band).

All I might do is fabricate a new cover to the air box. This is so simple. I am not sure if I will be able to quantify the difference other than qualitatively as I do not have free access to any Dyno's. If it "feels" better its worth at least 5hp and better MPG so I will let you know and snap a few pics when I have some thing.

[apsolus]

yeah i agree with you but it always just depends if the engine actually needs the extra airflow, i suppose the corvette was beging for it! im sure your right i bet these bikes would love the extra air too. but i like to leave good enougth alone im good with 130hp! haha im assuming you used to work at a dyno? ever see honda's with giant airfilter and drivers claiming 50hp gains?

[yamaha_george]

Knowing Yamaha as i do ,I would say that the Air duct system is just below optimum for the sake of manufacturing tolerances & warranty claims.

Removing HUGE chunks of the air box "restriction" is liable to be detrimental how ever sllght mods on a progressive series just MIGHT find something better. How ever the engineer in me says Dyno access is a must seat of the pants is very subjective, I have had the pleasure of having a pair of racers using the same bike for endurance and boy what fun that was NOT!

[reelrazor]

I'd say that there is more likelyhood of messing up any resonant benefits of the airbox (of which there are plenty-http://www.saltmine.org.uk/randy/airboxdesign.html - to start with),

than there are of hitting some weird sweetspot of de-restriction.

[KaMaKaZeE_FZR1]

I got the idea from Ivan's. He was trying to recoup some of the low end power lost after swaping to a full race exhaust.

http://www.ivansperformanceproducts.com/fzr1000.htm

At the time I was running a full yoshi exhaust, hi-flo filter, re-jetted, and was looking for a little more bottom end. Since then I have went back to the factory ex-up exhaust, re-adjusted the jetting, and I feel that it still has helped with the punch on the bottom end. The article above doesnt include all the info he used to have for the mod but It is quite simple and doesnt change the box from the factory specs significantly, only allows for a little more airflow to feed the beast. Also, im not sure what all the previous owner did when he built this motor but I think it has a little top end work, not much but always felt restricted with the box in original condition

[yamaha_george]

I'd say that there is more likelyhood of messing up any resonant benefits of the airbox (of which there are plenty-http://www.saltmine.org.uk/randy/airboxdesign.html - to start with),

than there are of hitting some weird sweetspot of de-restriction.

RR,
Randy Norian did a great deal of work for his RG500 breathing well. How ever i too have done a lot of work on air boxes for two strokes (primarily RD's &DT's ) and not having any recourse to scientific stuff & dyno's I had to do a lot more work than it should have been.

The DT series of 2 stroke dirt bike was very restrictive & and lacked punch but a fluke accident that punched a hole in the air box about an inch across got me started.
Thro alot of mucking about with sliding orfice I found that a 7/8 dia hole enabled the bike to get more punch BUT that hole had to be in just the right place on the box.

With the RD's the box was the biggest keep back so pods was the way to go BUT they had to be on risers for them to give the full an-leashed horse power up from 34 to 66Hp (that included port work, compression, head shaping & Spannies )


34Hp is what Yamaha quote and 66HP is what we got from a Dyno run in England and the engine was 15 years old at that point !

As I said I know Yamaha they are conservative, and slow small steps can reap some HP BUT YMMV

[DonTZ125]

The older bikes didn't have air boxes, they had filter protectors...

Consider that the FZR airboxes theoretically use technology and knowledge 10-15 years more recent than any RD. I have no doubt that improvements could be made, depending on the individual setup, but the days of "pitch and gain" are gone - even simple pod replacement requires a certain degree of intake length tuning, as YG so fervently preaches.

I have always wondered what might be achieved by a large volume airbox with high-flow intakes, variable-tune tract(s), and individual filter pods inside the airbox. To achieve the volume required, this would probably entail an RS125-style 'bucket' airbox, with the carbs inside and the tank itself as the lid (sealing foam strips everywhere, obviously). The 250s and 1000s might do better with this than the 400 / 600s, with their odd tanks; this might be a useful situation for a YZF600 tank swap.

[yamaha_george]

The older bikes didn't have air boxes, they had filter protectors... .

Don,
Tuned length theory has been around for a VERY long while at least back to world war 2 (i.e. before my time :-})
If you look carefully atlate '70's DT air boxes /filter covers etal then you would see the use of tuned length induction by the convoluted passage ways behind the filter. as to scientific use/proof i cannot help you with what i found in my own way as where I was very 3rd world and as some wiseass said back then "we have bike mechanics & we have K.G.B" (my company) which is probably why we were asked to take on the Yamaha service franchise for bikes.

[jdugen]

Airboxes are as much about noise restriction and CO2 readings as they are about performance. Most noise and emmision tests are done with the engine revving at about 5000 rpm. Just the point when you need lower end torque and this is the most restricted. Programmable ECU's are the main culprit in restricting the engine at this point, but a lot of other factors are in there too, carb jetting and airboxes come into play. To take advantage of any increase in airflow, the carb jets will have to be altered to compensate.

[yamaha_george]

Airboxes are as much about noise restriction and CO2 readings as they are about performance. Most noise and emmision tests are done with the engine revving at about 5000 rpm. Just the point when you need lower end torque and this is the most restricted. Programmable ECU's are the main culprit in restricting the engine at this point, but a lot of other factors are in there too, carb jetting and airboxes come into play. To take advantage of any increase in airflow, the carb jets will have to be altered to compensate.

On the older Seca750 we had a Yamaha tech show us a trick, I was away on course and I passed the info to the Yamaha sales racing team we worked with. He in his infinite wisdom decided more air flow cool bigger jets, I got back for the closing races on the weekend heard we were losing abysmally, so i asked him what else besides the mod he had done , nothing. so i asked if he had changed jets oh of course. which way, oh bigger of course.
Ok take the spare carb sets and drop the mains by one down from stock and drop the needle one down from stock..

The team came in 1 thro 4 next two races.as i said earlier Yamaha err on the side of caution running real rich to cool the engine.

So some times things are counter intuitive.

[DonTZ125]

I've heard tell of well-jetted 2-strokes having port / pipe / intake mods, and actually wanting SMALLER jets to go with the increased airflow. Seems the reduced flow restriction was also allowing a stronger signal to the jets, sucking more fuel up and in.

Whenever you modify something, what you had is now a starting point. Check EVERYTHING.