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Ram Air on a RT


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There have been numerous discussions about installing a GS air snorkel on an RT. I did this, and put in a K&N filter to get it to breather easier, knowing of the limitations for the in-side improvements.


The snokel has two parts, one going into the air box, and a larger tube runs to the front of the bike, but the interscetion of the two tubes is not connected. It is a "big tube feeding a small tube". Has anyone connected these tubes to create a ram-air effect? Is there a good reason why these two tubes, stock or not, are not connected?



Your feedback will be appricaited.


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Jim, a couple of reasons the intake snorkel is not sealed to the air box.. The first being water intrusion.. If the bike was parked with that tube facing up hill it could allow water to run into the air box..


The second reasons is the fuel injection system is pretty primitive & has no way to deal with air box pressure so if more air is forced into the engine the fuel injection system wouldn’t know to add more fuel to the air.. In closed loop it could handle it based on 02 input but at WOT open loop it couldn’t..


I doubt you would get much ram air in it’s current location & snorkel size anyway..





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There is no restriction on the intake of these bikes outside of the heads. If you want the bike to breath easier you have to re-work the intake tract but that will do no real good as the exhaust port is more restrictive. So that will need re-machining too - oh, and you also need to change the cam profile to take advantage of this.

There have been dyno tests done on a R1100RT with various intake filtering configurations and the K&N brings NO gains to the party. In fact with the stock filter more than half covered in plastic film there was no loss in power. These engines are simply not restricted in intake or exhaust beyond the contrints of the head casting.



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Airflow INTO the boxer motor is not a limiting factor to engine performance. Hence, no K&Ns, no ram-air.


Woodie, you are probably correct on the air filter (at least in theory) but not on the ram air.. Any time you increase atmospheric pressure into the intake you can force more air in through a smaller opening..

So with a turbo,, or blower,, or FUNCTIONING ram air you would flow more air into the engine for the same intake restriction.. It would still be limited but more air none the less.. The problem becomes on how to effectively add fuel to that air..




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I give the same response I give to may HD riding buddies who blow cubic dollars making their bike go faster. After spending all the money and hours of work to get more power out of a motor that was never designed to be that kind of motor, some snot nose kid on a 600 cc rocket from Japan will leave you in the dust the first time you want to "get it on". So why bother!


Save the pain, money and a less reliable bike that can never reach the potential of a stock repli-racer, and put that money down on one of those fast 600s and be done with it. Or the 1000 cc version if you want to scare yourself silly when going WFO.

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Thanks for the valuable insight. I'll leave it alone (for now).


One post questioned: If you are satisfied, why change it? My reply would be that I'm interested in moving past the standard, into new territory. Not that it is always an improvement, but it is always fun.


Finally, I'm interested in maximizing the performance of my R1100RT and not changing bikes. One does not find too many rockets listed on the Iron Butt web site under the Bun Burner Gold category, but you will not only find an R1100RT, but my name as well (1562 miles in 21½ hours).


Ride Safe!


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Joe Frickin' Friday

Have you done the math? At 75 MPH, the best improvement in airbox pressure you could hope for is 0.67 percent. The effect scales with the square of speed; so at 37 MPH, you'd expect (at absolute most) about 0.16 percent boost.


Cheap-but-proven mod? Swap GS intake tubes for your stock tubes. Lower peak horsepower, but better mid-RPM torque, where you'll use it on a regular basis.


Pricey-but-proven mod? See San Jose BMW, where they'll sell you a set of heads that have been modded to accept dual spark plugs. Better MPG, more power, though I don't recall how much.

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Lots of people spend lots of $, time, and thought in order to chase some imagined improvement in power/speed/performance/?. The RT has been around for many many years and I for one would imagine if some significant improvement in performance could be achieved, BMW would have integrated those improvements over the years. Chase what you like but that will likely end up in some theoretical discussions with your fellows, but no change in performance. TEHO.

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Something more to keep in mind here.


For ram air to work effectively it requires that air box pressure be maintained and, if the fueling is to work at all, it has to pretty much follow the speed vs pressure predictions as outlined by Mitch.


The BMW air box is WAY too small for this. Liter size engines with ram air such as ZX-11/12/14 have air boxes with a capacity of over 6 liters for this reason. Ditto my old Blackbird which, according to the magazines of the day, had the most effective ram air system with measurable improvements at speeds as low as 80 mph. Note that almost all these are 4 cylinder engines with much smaller piston pulses and hence air box pressure variation than would be the case with the boxer motor.


Pro Stock drag bikes typically have a 15-18 liter air box to feed the 1.5 liter motors except for the Harley powered ones where the air box deal flat doesn't work. They lose out on the ram air but make up for it with 50% more displacement.


Ram air does work and works pretty well if the bike was designed to take advantage of it with something like a MAP sensor to help compensate the fueling and a big air box. It also helps to get some speed up. Say 120 mph and up. The RT is just about done for at 120 mph anyway and will never see 140 even if you throw it off a cliff.


In short, spend the money on a riding school instead. It will make everything you ride faster.

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Suffice to say, other than extensive mods to an antiquated engine, leave the beast alone.


An engine is in fact an air pump. You have to move calulated amounts of air and fuel THROUGH the engine, not just stuff it in one end.


What ya trying to accomplish here? It's an RT...


Now if you really want to go fast.... :grin:



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Total rebuild, strengthen the cases while apart, add turbo, and 5lb NO2 bottle in side case, stage 2 nozzles could attach easily into the intake tubes. With all that you may be able to keep up with an R6, for twice the money at least. But the look on the kids face when you spooled up and hit the button would be priceless... :grin:

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Total rebuild, strengthen the cases while apart, add turbo, and 5lb NO2 bottle in side case, stage 2 nozzles could attach easily into the intake tubes. With all that you may be able to keep up with an R6, for twice the money at least. But the look on the kids face when you spooled up and hit the button would be priceless... :grin:


I think I would like to see the look on YOUR face when you hit the button to spool it up ))) :grin:


I suspect riding that for the first time will be a bit of a shock... and you might want to make sure you have plenty of straight running room when you hit it... ))) :grin:


Regards -


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RB Racing turbocharger with custom injector pump and Black Hole exhausts would be my choice (assiming I had an extra 10K lying around)...

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