What do you know about them? How well do they work? How hard are they to tune. I know they are tuned to an Engines harmonics but any Comments, thoughts, insight would be great.....go!
Variable length intakes
- Thread starter 'blanshee'man
- Start date
well on a four stroke like that i dont think the intake length is going to effect it nearly as much. im sure it works to an extent with adjusting the speed at which the air comes into the engine. are those bikes fuel injected? sorry im not real familiar with them
well i would guess then (and im no expert) that you could tune the air intake speed to match the exhaust speed and the specific fuel air mixture to maximize performance. its not going to add hp but its going to maximize the hp thats already there
Length of an intake and shape of the runner is what determines velocity and turbulence of the intake charge a shorter intake runner doesn't do much for proper air fuel mixing it's kinda like slamming someone in the face with a baseball bat and then making them read Shakespeare too long of a runner and throttle response drops because of pressure drop the intake runner acts like a low pressure regulator the pressure behind the throttle slide drops because of the small opening variable intakes are difficult to tune unless you have a cad program a flow bench and a dyno for tuning
good luck
good luck
CAD flow bench yes. dyno yes i have access to both to use basically when ever i wish. I have to short of a runner now so wanted to make a spiral shaped and make it decently longer and rig up a servo that runs off a tac to determine the optimal length. Its a dog up untill about 8 grand then it hauls ass. The rev limiter is set at 13000.
Suzuki has been mseesing with airbox harmonics since they began making street bikes. The problem with tuning your intake runners is (wait for it, wait for it just a little more...) it's a trade-off just like everything else. If you want to tune for 13,000 rpm it's going to be a dog until 8,000. Suzuki did SRAD on purpose to tune their engines for the tracks they were running at the time. Anything other than those tracks, and you're out of the power range.
The highest power outputs (of naturally aspirated engines) don't use intake runners at all. They are velocity stacks with fuel injectors aimed directly down their throat. Again, a trade-off. The driver won't ever let the engine run below 10,000 RPM so they don't need "torque"
If you're trying a servo actuated intake system, you're going to be using some sort of butterfly to change the airflow. The trick is to turn the air at low rpms making is more "restrictive" and allow it straight into the intake runners at high RPM's. The trouble is, frequency harmonics of the airbox itself comes into play on something turning the RPM's of a GSXR 600. The engine puts sound waves out of the intake runners when you're looking directly down them. Anyone who's heard an engine rev without the airbox on can attest to it. A high revving engine like that puts out a different frequency at the various RPM's it turns. That sound actually affects the airflow through the box.
http://en.wikipedia.org/wiki/Helmholtz_resonance
Tuning for this is next to impossible on standard CAD equipment.
The highest power outputs (of naturally aspirated engines) don't use intake runners at all. They are velocity stacks with fuel injectors aimed directly down their throat. Again, a trade-off. The driver won't ever let the engine run below 10,000 RPM so they don't need "torque"
If you're trying a servo actuated intake system, you're going to be using some sort of butterfly to change the airflow. The trick is to turn the air at low rpms making is more "restrictive" and allow it straight into the intake runners at high RPM's. The trouble is, frequency harmonics of the airbox itself comes into play on something turning the RPM's of a GSXR 600. The engine puts sound waves out of the intake runners when you're looking directly down them. Anyone who's heard an engine rev without the airbox on can attest to it. A high revving engine like that puts out a different frequency at the various RPM's it turns. That sound actually affects the airflow through the box.
http://en.wikipedia.org/wiki/Helmholtz_resonance
Tuning for this is next to impossible on standard CAD equipment.
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Thanks for the posts guys, ill definably keep you guys up to date with how this goes. But what completely forgot to say was why im doing this ha. Well i ended up joining the UNH FSAE team University of New Hampshire Formula SAE and got on the engine and drive train group 3 people, a sr a grad student and I (the grad student seems to know alot about engines and sh*t he says he has been building rally cars for 20 so odd years) and talked about what we can do to make it faster. Right now the dyno chart is VERY peaky and all the power is waay up top so we are trying to flatten it out a bit to make it not fall on its face out of the corners like it does. we are already throwing the stock header back on because it has a butterfly valve the other header doesnt so that should help down low a bit. But our main focus is the intake at the moment
sicivic- that thing is crazy!
sicivic- that thing is crazy!
I agree. Peaky is what those small displacement inline-4's do best.
So basically, you need to design a curve in the manifold with the direct shot going straight into the throttle bodies. The direct shot is cut off by butterfly valves until it becomes advantageous to open them, usually about 60% full throttle or whenever your timing maps jump to the high speed timing advance.
http://upload.wikimedia.org/wikipedia/commons/5/57/Lower-intake-manifold.jpg
Honda cars (prelude and civic Si's use it) and they have the butterfly's open at VTEC. Because the engine is then running on high cam (and usually a WOT trying to put out as much power as possible) and the velocity in the intake runners is great enough to dampen out individual intake pulses, you want the velocity as high as possible to ram more air in during the intake stroke. Instead of dampening out intake pulses with a long runner, you begin to force feed the cylinder when the intake valve opens with increased velocity.
So basically, you need to design a curve in the manifold with the direct shot going straight into the throttle bodies. The direct shot is cut off by butterfly valves until it becomes advantageous to open them, usually about 60% full throttle or whenever your timing maps jump to the high speed timing advance.
http://upload.wikimedia.org/wikipedia/commons/5/57/Lower-intake-manifold.jpg
Honda cars (prelude and civic Si's use it) and they have the butterfly's open at VTEC. Because the engine is then running on high cam (and usually a WOT trying to put out as much power as possible) and the velocity in the intake runners is great enough to dampen out individual intake pulses, you want the velocity as high as possible to ram more air in during the intake stroke. Instead of dampening out intake pulses with a long runner, you begin to force feed the cylinder when the intake valve opens with increased velocity.
try making a dual intake system with a butterfly valve for it.
like on many "sport" cars, they have dual intake runners one is bigger than the other and they have a butterfly valve to control the intake flow.
some cars i know that use this is the Taurus SHOs (both V6 and V8) and the Sentra Spec-V (QR25, this also include other nissans too).
you could also try to have your exhaust size change with RPM range. i know ferrari those this at like the header, corvette does it in the muffler. same conpect as the intake, you want it smaller diameter at lower RPM and bigger at higher RPM.
like on many "sport" cars, they have dual intake runners one is bigger than the other and they have a butterfly valve to control the intake flow.
some cars i know that use this is the Taurus SHOs (both V6 and V8) and the Sentra Spec-V (QR25, this also include other nissans too).
you could also try to have your exhaust size change with RPM range. i know ferrari those this at like the header, corvette does it in the muffler. same conpect as the intake, you want it smaller diameter at lower RPM and bigger at higher RPM.
Exactly guys. The butterfly is our best option but there is some guide lines on the intake we have to follow. Before it enters the engine it has to pass through a 20mm restrictor plate. Also nothing that can throttle the engine can be placed after the restrictor. But after the restrictor it can be split or whatever as needed (it just has to be the last mechanical device to alter flow). So it will be interesting to how it comes out.
We can do the valve, it just has to be before the restrictor which im not sure if would actually help. Ill have to test some stuff out. But yea we will have plenty of tuning time on the dyno and track for the final set up.
