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Discussion Starter · #1 ·
Now I know a lot about engines, but I do not know a lot about engineering them. Sure I can fix them, figure out what part isn't doing it's job, clean them and bolt it all back together, but I haven't yet been able to build and design an engine from scratch. One day while looking at a friends Triumph Twin though, a thought occurred to me. If getting great air flow is a huge part of motor efficiency, why have the carburetors facing the opposite direction of the wind? If you were to theoretically place the carburetors where the exhaust ports are and vice versa for the exhaust, and then tune the bike for such an operation, wouldn't it vastly improve air flow? I mean, it would practically be turbocharging it? If someone could enlighten me as to why this would be tremendously stupid though, I would much appreciate it. Thanks!
 

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Been done before, the problem is the motor injesting Rocks Small Dogs/cats children......

You get the pic.....:rolleyes:

.....Roach.
 

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Cooling plays a big factor. The pipes are facing forward to balance the heat in the engine. Look at old BMW and Guzzi engines. Heavy finned exhaust nuts help too.
 

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Cooling plays a big factor. The pipes are facing forward to balance the heat in the engine. Look at old BMW and Guzzi engines. Heavy finned exhaust nuts help too.
When I say pipes, I mean exhaust ports.:rolleyes: But you already knew that.
 

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How would you jet for wide open throttle at 10 MPH and the same at 100 MPH? You would need some very sophisticated fuel delivery at all speeds and at all RPM's to make it work. Air cleaners would ruin the ram effect for the most part.

Might work for a drag or land speed bike but I don't know what you would do for the street.
 

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youl need to go around 160 or better, maybe 180, before you see any positive pressure..and then it wil be very slight.you have to remeber that air will have to over come the cfms its that its already ingesting to make positive pressure.
 

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youl need to go around 160 or better, maybe 180, before you see any positive pressure..and then it wil be very slight.you have to remeber that air will have to over come the cfms its that its already ingesting to make positive pressure.
All true, but remember, even if you don't create positive pressure, reducing negative pressure will still be seen by the motor as lowered restriction, and give you some free HP

I had a 70 GTO I made a ducted fresh air system for, using dryer ducting and large rectangular funnels under the nose, and I gained about 12MPH of top-end with just that. Some of it was lowered temp, but you could definitely feel the difference from 100 to 147.
 

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Heat dissipation of the exhaust ports. More important than ram air injection on an air cooled engine.

Not to say plenty of Triumph don't have flipped heads.
 

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Ram Air Induction.
I once tried it on a Ford Capri v4 it made a very noticeable difference on a stock carb with stock settings. We ran a VW beetle defroster hose from the grille to the air filter housing.
 

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I agree with kickstarts reply .
I remember reading about some old timers trying this set up at bonneville and also at the dry lakes.Problems with carb tuning caused them to give up.
HD drag bikes using velocity stacks with a forward facing scoop use float bowls that are sealed up and then connected to inlet tract pressure so that the float bowl and venturi can function properly ,otherwise air pressure at the carb will be higher at the venturi than at the float bowl and tuning goes out the door.
The below link has some interesting thoughts on air boxes which seems a better solution
http://www.thunderproducts.com/AirboxesDynotech.htm

Cheers R

 

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Discussion Starter · #13 ·
Hmmm, okay, I see the issues. What about having velocity stack style ports that are basically u-shaped so that you get the ram effect but without sacrificing, the exhaust placement, air filtration, etc.? Would it be pointless because of the u-bend or could that in a way help? Sorry if this are all dumb questions, I am just starting to get into air flow theory and all of this. It's fascinating! Thanks for all the replies too guys!

EDIT: Just saw Riding Hood's response too, so it is possible then? You just need to account for the difference in pressures?
 

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Regarding speeds involved, the Kawasaki Ram Air system for example does provide an appreciable horsepower gain at way below 160 or 180mph. According to tests it's under 100mph when things start to take effect.
 
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