Ram air

Message

szrdave · #1 Post by **szrdave** » Sun Mar 06, 2011 5:31 pm

I was removing the airbox to check the front plugs today, and it occurred to me the ram air system is really badly designed. The inlets are nowhere near the high pressure region at the front of the nose, and the ducting is not very big and poorly sealed.

Even a well designed ram air system will only give a 5% power increase, and you'd need to be going well over 100mph to get it, so the Falco system probably gives little if any improvement to the top end while restricting low speed power and throttle response.

Has anyone tried removing the connecting Y piece that seals the ram air inlets to the airbox?
This would give a nice big hole directly into the air filter for the airbox to breath through, with the advantage of the ram air tubes providing nice cool air from the front of the bike. The only disadvantage would be the loss of any ram air effect that occurs at high speed.

If I'd have thought of this earlier I would have left the Y piece out and gone for a test ride!

I'd be very interested to see the results of comparative dyno runs and high speed testing for both configurations.

Aladinsaneuk · #2 Post by **Aladinsaneuk** » Sun Mar 06, 2011 5:46 pm

iirc the actual ram effect on the big rotax engines is of minimal value - even the reduced snorkal sizes on the slower colours had very little performance effect

actually getting air in - as in opening the airbox up, is the real key

(Very simple analogy, and the figures are NOT correct but - if the displacement is 1000cc and the airbox is only 750cc then it is easy to see what the engine can be starved of air..... by increasing the airbox size - evo solution, or dispensing with it totally - renegade solution the problem is removed).
I have been looking at someones copy of the Edwards replica mille ram system they are now selling - i remain sceptical about the value of it unless you are doing track speeds.....

all of that is, of course, just my opinion

szrdave · #3 Post by **szrdave** » Sun Mar 06, 2011 6:02 pm

Aladinsaneuk wrote:... even the reduced snorkal sizes on the slower colours ...

Genuine LOL!

It sounds like we (and the rest of the world) are pretty much in agreement that 'big twins need to breath'. Obviously the various airbox options give a bigger pool to draw from initially, but this still has to be replenished via the ram air ducting.

If I get a chance one weekend I'll remove the Y section and go for a spin. Chances are the bike will just feel fast though, as it did before! And I'm loathe to leave it out for any length of time as it should have a significant effect on the fuelling.

Next time I see a local dyno day I'll get a run done with and without, to see if there is any difference and how the a/f ratio looks.

randomsquid · #4 Post by **randomsquid** » Sun Mar 06, 2011 6:19 pm

Aladinsaneuk wrote: actually getting air in - as in opening the airbox up, is the real key

Mmm, we seem to have lots of tanks of various gases, valves, tubing and duct tape just lying about at work.
I may have a cunning plan.

Nooj · #5 Post by **Nooj** » Sun Mar 06, 2011 6:19 pm

The Falco intake system isn't designed for 'ram air', the intakes are just a couple of tubes to let air into the box, the bike will run just as well without them fitted.

The ram air effect varies from bike to bike speed wise, it depends on how the intake system is tuned (ours isn't tuned) on each bike.

szrdave · #6 Post by **szrdave** » Sun Mar 06, 2011 6:44 pm

Nooj wrote:The Falco intake system isn't designed for 'ram air', the intakes are just a couple of tubes to let air into the box, the bike will run just as well without them fitted.

I'd have to disagree with that first statement, the only time you'd run a sealed intake from the front of the fairing is in an attempt to create a 'ram air' effect. The longer the intake is the less efficient the system will be, try breathing through a long straw and a short straw of equal diameters for a practical demonstration.

It's for this reason I think there could be an improvement by ditching hte Y piece to move the start of the intake path to the bottom of the air box rather than from the front of the fairing.

The ram air effect varies from bike to bike speed wise, it depends on how the intake system is tuned (ours isn't tuned) on each bike.

The maximum ram air effect would be achieved by transferring 100% of the pressure increase at the stagnation point in front of the fairing into the airbox. In practice this is impossible due to the location of the airbox and associated losses in ducting the air flow. Variations in ram air effect between bikes will depend on the efficiency of the ram air system, and to me the Falco system looks incredibly inefficient!

Aladinsaneuk · #7 Post by **Aladinsaneuk** » Sun Mar 06, 2011 6:54 pm

Actually some of the falcuonos have done away with them pretty much....

Also, if the aprilia ram air system was effective then you would need girt big fans in the dyno labs.....
(or would notice a difference when running the bike depending on speed and engine performance)

k1w1boy · #8 Post by **k1w1boy** » Sun Mar 06, 2011 7:14 pm

.... my snorkels haven't been a sealed system since the front 'fell' off a couple of years ago, taking the lugs etc with it. As we know, 'performance' is to me (beyond the obvious), what media-induced hype is to a goldfish: I haven't noticed any difference without a sealed, fully functional system.

D-Rider · #9 Post by **D-Rider** » Sun Mar 06, 2011 7:17 pm

It'd not fully sealed and it doesn't really work as a ram-air system.
What it does do is duct cooler air from the front of the bike rather than sucking warm air from around the engine.
Also the intake air temp sensor is in one of those intake tubes so if you pull out the snorkel you are dragging in hotter air (particularly when slow/stopped in traffic) and the temp that the sensor is feeding to the ECU is not of the air that the engine is breathing.

That's a penny-ha'penny-worth of my two-pennyworth.

#10 Post by **Kwackerz** » Sun Mar 06, 2011 9:34 pm

That engine shunts out enough power to not focus on the ram effects.

what you want to be looking at it VOLUME, not volumetric efficiency.

it should SOUND like it sucks in small children at 50 paces, eats cosworth sierras for breakfast and shits them out as 1.3 popular plus escorts for dinner..

..something which Renegade and similar have managed to do quite well

szrdave · #11 Post by **szrdave** » Mon Mar 07, 2011 9:16 pm

Agreed, although I've already got plenty of volume from the other end (the bike not me

).

Maybe it's time to go oldskool and ditch the ram air and injection, you can't beat a pair of massive FCRs with a tea strainer to keep the flies/roadside funiture/small animals out