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Discussion Starter #1
I have a 900SS for track duty. Bought split FCR's for it to get some more RPM's from it.
However, I can't run open race exhausts on the track (only 95db allowed!).

Last time at the track I ran stock carbs with stock airbox (lid closed) with baffles in my race exhaust and did not get any warnings regarding exceeding the noise restriction.

Split FCR's run K&N pod filters, making more noise than stock filter. Maybe a bit too much with the race exhausts (even with db-killers).

So I was wondering if I could run stock exhausts with the FCR's?
Or would that kill all advantages from the FCR's?
 

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HMMMM, I'll chip in. Im clearly no expert from my current thread which has split carbs. An engine is a air pump, effected buy the extremeities of intake/exhaust length and diameter and the myriad of combinations that one may try. Of course each engine has its own DNA and correct combination so dont rule out stock exhausts with FCR's.

Lets break this down. A flat slide replaces the std mikuni vac diaphram slide system. This means where ever you have that slide open, is your fuel supply regardless of RPM. Another advantage is the lack of a butterfly which increases flow dramatically ++ so far.
Also the decreased intake length will raise the rev ceiling which all helps the FCR,(you may want to change cams to take full advantage of the increased rev range now) So now we have this air pump breathing a little better, with a much better throttle response, its a win so far. The noise from the carbs are well below 95db so dont worry about that. The stock headers are good for 90hp and i cant see the mufflers being a massive bottle neck so if you can tame the sound from your mufflers its a no brainer to go FCR's.

Maybe enlarge the perferations in the baffel and repack....or if all else fails short shift past the sound meter. I'd be interested to see how this goes.
 

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Discussion Starter #3
In time I 'll most likely go for ST2 or 900SS I.E. cams. That's more of a match for my budget ;)

I was hoping for somebody with experience on running FCR's with stock exhaust. But it seems there's nobody crazy enough to do so :eek:
Seems testing will be the best option.

It would be a pity though if the stock exhaust's layout would limit the potential of the split FCR's too much. Then I would be better of using them on my Superlight road bike :)
 

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The stock SS exhaust is very similar to the 888 strada exhausts being the same size (40mm) and crucifx layout (can swap exhaust cans between these) . The std 888 can make around 90RWHP when subjected to minor fettling (time cams/open airbox lid/map) so shouldnt be overly restrictive on a FCR'd SS 900. However I'm not sure the open filter intake noise will be low enough to pass the noise test and you might need to look at using an airbox (which could limit midrange/top end hp) to get it close to passing.
PS open clutch covers don't help either if you have one fitted
 

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I use rail mounted 41's with a stock exhaust. Works fine. Maybe a little rich but the starting procedure is not so tedious.
Off topic but:
I'd be concerned with the stock header on the track. The turnouts catch the asphalt fairly easily. With flats ground on both sides of my header, I consider myself very lucky.
Dez
93ish SS
 

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Discussion Starter #6
First of all, apologies for bringing back a 7 year old topic back to life :)
Feel slightly embarrassed that I made zero progress on the bike since.

But hopefully during winter I can treat myself to some garage time!

I'll be using a 1994 900SS as a track bike.
No need for max. power / weight reduction etc. Just want to have good fun.
As you can read above, tracks around here have noise restrictions and some even require the use of stock exhausts.

I have a set of split Keihin FCR's laying on the shelf that I wanted to use on this bike, to have some power at higher RPM.
Problem is, pod-filters would make to much noise (even with stock mufflers).

But I think I've found an easy solution: using the airbox of an injection model Supersport :)
Found these pictures on a German board (ok, it's Mikuni flatsides but should work in a similar way).



It might be a less-than-perfect airflow from the airbox into the carbs, but at least noise will be near the stock levels and I can have fun without risking a black flag :)
 

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What are the rules for the tracks noise limits?

I do sound checks for a track day group in the north east as we have one track with very tight standards, too tight. As in every year we fail numerous bikes that are 100% stock and un touched. Cbr1000rr that was 4 days old , panigale 1299, aprilia rsv4 etc did not pass sound check ** as the sound check was dictated***. If you are trying to pass a sound check on track then you will need to look more at limiting your rpm's as this is what gets most bikes.

We are allowed 92Db at redline at this track but because our customers are adults the track allows us to find the rpm that they will pass at and if they stick to it they can ride. We had a R6 with pipe that was limited to 6000rpms I am pretty sure a yamaha R3 makes the same power, but he got to play.


My point is get the tracks sound limit rules and read them carefully, then find/get a sound meter. I test for state inspections so have a class one sound meter $$ , we have tested against cheaper meters and they do not have the same accuracy but are probably plenty close for what you need( this is what the track uses). We have supersports with aftermarket exhausts (mine as well) that pass this test but it is not all. only way to know is to test what you have and then adjust as needed.

I feel pretty safe in saying the intake is NOT your issue, stock exhaust or Db killers in your exhaust and you should be fine as your bike will not be making power to 9000rpm unless you have had the heads ported and this can be confirmed by a dyno run to know when power is over. What is loud and you might look at is a open dry clutch at idle, make sure if the test is at idle they do not meter your dry clutch as they are often louder than exhausts at equal distance (not while under power probably). .

meter the bike before modifying as you may fiind you do not have to change much. If you exhaust needs re-packing start there. Db killers effect power very little if you have a standard size can and will often clip about 5 Db.
distance from meters, each foot away from a track side meter helps find them and give them space. a 102Db bike was under 60 when meters 200 yards away so every foot counts.
Rpm's hurt, find what rpms your bike makes peak power and peak noise and work to keep the peak power under peak noise. If your bike is not built for high rpm's yet focus on making more power down low where the bike is not as loud. A bank of FCR's on long manifolds and degree the cams more for midrange will gain you more power where you are allowed and you may find the bike to quicker out of corners but this can be track sensitive.
 

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Discussion Starter #8
Of the 2 tracks I would visit most, 1 has a static limit of 95dB (not sure if they measure until red-line) but 102dB dynamic (track side) measurement.
The other has a limit of 95dB dynamic measurement on 2 points on the track (easy to avoid detection if being easy on the throttle on those parts of the track).
Some tracks only allow for stock exhausts, so that's what I'm going for.

I intend to use a closed clutch cover to quiet things down a notch.

Racked carbs (maybe even just to stockers) might indeed be better for my intentions (not planning anything major on the motor, want to keep the budget down + my track skills don't justify major costs to increase HP).
However, I bought these split's for less than 500 euro. So just looking to work with what I've got really :)
All I might consider is some HC pistons (splitting the cases to replace all bearings, so whilst in there... why not) and most likely some 900 i.e. cams (or ST2 or similar profile if they come around cheap).

Some people already told me I would be fine with the pod filters, others not. I would settle for the airbox just for the ease of mind.
I was looking for find some advice on whether an airbox set-up would limit the advantage of having the split carbs (a slightly wider power range) too much?
Off course, I can start out with pod filters and measure the dB output. But always nice to know in advance plan B can work as well.
 

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The airbox won’t cause a power drop vs pods but will be quieter. A closed clutch cover or alloy plates and the quiet clutch mod would help. You might be able to use head pipes that allows more ground clearance and a more efficient design with stock mufflers. Though may be able to get away with boring the baffles in stock mufflers and still stay pretty quiet but lose a little back pressure. Remember, the sound meter sees the total noise you’re making, not just exhaust noise. Intake and clutch noise reduction might help a little.
 

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If I owned the FCR's I would give them a try just know if you build the bike to make its power higher in the rpm's you will increase the need to quiet the exhaust. realisticly you will likely not gain that much so if you run a open airbox or pods and use larger volume slip ons with a good Db killer you should be fine at both tracks. the exhausts i see issues with are the ones people cut too short or make too thin so that a Db killer becomes too much of a plug. Volume is your friend to quiet the bike and keep Hp, that's why factory exhausts are so large.
 

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If I owned the FCR's I would give them a try just know if you build the bike to make its power higher in the rpm's you will increase the need to quiet the exhaust. realisticly you will likely not gain that much so if you run a open airbox or pods and use larger volume slip ons with a good Db killer you should be fine at both tracks. the exhausts i see issues with are the ones people cut too short or make too thin so that a Db killer becomes too much of a plug. Volume is your friend to quiet the bike and keep Hp, that's why factory exhausts are so large.
Has anyone ever tried these "power bombs" or "megabombs"? .... pictured is one made by FMF .... they're intended to be used with a tail muffler (aka "slip on"). One design is an anti reversion system, the other acts more like an in-line muffler (more or less). Perhaps using these types of technology along with slip ons, may not only keep the exhaust sound pressure levels ("SPL") under track limits, but also if applied right may also increase power. Taking care in the design and placement can move the power curve around, allowing "tuning" of the power output and placement of the power curve, as well as reshaping the curve to whatever one needs or wants. If nothing else, it may be worth looking in to at the very least. Most likely FMF and Megabomb do not make ready-to-go systems for Ducati SS bikes/engines, but since the technology is so bloody simple replicating the design would be very simple.

The FMF type is an anti-reversion design, placed about a foot or so from the exhaust outlet on the cylinder head (placement is important as it affects the power curve). The Megabomb system is more of just a perforated baffle, like a slip on, but it's installed in-line somewhere near the exhaust outlet on the head (within about a foot or so).

Here's a good discussion regarding both designs;

LINK = https://thumpertalk.com/forums/topic/1075515-megabomb-header-explanation/

DucVet, if you're not already versed on these things, you may find the information especially interesting.

975576
975577
 

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Rex it is these moments i want to buy a welder and start making "test systems" I have some of the tools needed just a welder and oh yeah... skills. lol

I have not seen this type of exhaust tried on a Ducati (or any other) with before and after dyno runs to help see any change. A friend used to make systems and experimented with a strategically added venturi based on rocket engines we welded at work. Not sure if they helped,hurt or were just another unknown "feature".
 

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First of all, apologies for bringing back a 7 year old topic back to life :)
Feel slightly embarrassed that I made zero progress on the bike since.

But hopefully during winter I can treat myself to some garage time!

I'll be using a 1994 900SS as a track bike.
No need for max. power / weight reduction etc. Just want to have good fun.
As you can read above, tracks around here have noise restrictions and some even require the use of stock exhausts.

I have a set of split Keihin FCR's laying on the shelf that I wanted to use on this bike, to have some power at higher RPM.
Problem is, pod-filters would make to much noise (even with stock mufflers).

But I think I've found an easy solution: using the airbox of an injection model Supersport :)
Found these pictures on a German board (ok, it's Mikuni flatsides but should work in a similar way).



It might be a less-than-perfect airflow from the airbox into the carbs, but at least noise will be near the stock levels and I can have fun without risking a black flag :)
FWIW - my SMI (Sil Moto Italia) system came with dB killers. 95dB ones. Way quieter than the standard exhausts - but REALLY restrictive - to the point where the bike was struggling to idle or run, it was so choked up - still on the CV carbs and standard headers at that stage - I was just 'trying' the new exhausts to see what they sounded like.
The headers are hard to get now, but the tailpipes are available with a bit of a hunt.
Some hi rise ones - https://www.eurocorsa.com/cgi-bin/commerce.cgi?preadd=action&key=2800
 

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Rex it is these moments i want to buy a welder and start making "test systems" I have some of the tools needed just a welder and oh yeah... skills. lol

I have not seen this type of exhaust tried on a Ducati (or any other) with before and after dyno runs to help see any change. A friend used to make systems and experimented with a strategically added venturi based on rocket engines we welded at work. Not sure if they helped,hurt or were just another unknown "feature".
Haahaa! ... I have the welders and other machine tools needed (and skills) but I'm without a dyno, and no local access to one either. So any testing would need to be seat of the pants, and time consuming timed runs, 0-60 stuff, 50mph on-up run-ons, fuel consumption, and all of the other old school stuff. Super interesting ideas (those anti-reversion systems), really gets the blood pumping when thinking about it. Buy a few sets of $30.00 stock headers on eBay, get out the hacksaw/welding machines, and start putting together systems with different variations on the theme. Then the hard part ... matching cams along with valve sizes and port configurations to take full advantage of it all. It would be easy to sink a few years into the research for the lone (and curious) wrencher!
 

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A while ago someone on Facebook showed a dyno of their S2R 800 with an airbox and then with pods. The dyno indicated a loss of 5HP with pods. I can't recall if it was a static loss or mostly just around the peak. I think it's safe to extrapolate from that and say there would be a similar power loss on a carbie 900.

For me personally a ~2% power loss is worth the sound, clean look, and ease of service pods deliver. If I was racing, however, I would want that ~2% and thus I would have an airbox.

PS - I have an airbox for sale if you need one.
 

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As always check the details before coming to conclusions.

Was the air fuel adjusted for the pods?
was it peak ve peak power or power everywhere was off. I would expect if the fuel is matched the pods will make more power but might suffer driveability without the airbox. Removing the airbox is the easy part, making it wrk is the important part. I have a m1000 customer who bought the bike with pods, it is close enough that we never bothered to put a airbox back on. Keep in mind you need to do it and then check air fuel to know.
 

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The air box is a known commodity, while the pods are not. If you use the largest pod that will fit, and If the filter media is low enough in restriction, and if putting the tank in place doesn’t block too much filter area, you have a chance to make as much power with pods as with the air box with a good filter and modified lid. The air box always has the advantage of larger internal volume and puling its air from the open area under the tank. the pods have one big advantage: Ease of maintenance for the carbs. if you use pods, make sure theyre constructed well enough not to collapse and reduce flow when dirty , some of the foam type are shaky in that regard.
 

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As always check the details before coming to conclusions.

Was the air fuel adjusted for the pods?
Great point. Without adjustment that wouldn't be a fair comparison. I don't think it was adjusted otherwise I would expect a time consuming event like that to be shared along with the dyno report.


you have a chance to make as much power with pods as with the air box with a good filter and modified lid

Ease of maintenance for the carbs. if you use pods, make sure theyre constructed well enough not to collapse and reduce flow when dirty , some of the foam type are shaky in that regard.
I have only heard the performance benefits of pods for power - what about throttle response and bottom-end performance? The air-box can take advantage of Helmoltz resonance. If I had to guess I would say less resistance at the very least leads to better throttle response, but I'm not sure if it's noticeable in the real world.

I had velocity stacks at one point. It made tuning and maintenance even easier and I also enjoyed the look and sound of it. I was worried about dirty air being sucked in so I purchased pods. The issue is that I think pods compromise the design of the velocity stacks, namely the bell curve and thus the venturi effect.

What pods do you run? I have UNI pods.
 
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