Smaller Header Pipes

[HDTboy]

They run a 17 john, alarumba, i've knocked the baffles out of mine and it's very loud now, louder than my flatmates CBR600 with micron

[Coyote]

They run a 17 john, alarumba, i've knocked the baffles out of mine and it's very loud now, louder than my flatmates CBR600 with micron

Notice any change in performance?

[Lou Girardin]

Micron Sepent headers have flattened sections just out of the port, but whether this speeds up gas flow or just helps clearance is not clear.
I doubt that 100% VE can be achieved without forced induction though.
Anyone know the BMEP figure at 100%VE for given cylinder capacity?
Motu?

[Motu]

Micron Sepent headers have flattened sections just out of the port, but whether this speeds up gas flow or just helps clearance is not clear.
I doubt that 100% VE can be achieved without forced induction though.
Anyone know the BMEP figure at 100%VE for given cylinder capacity?
Motu?

The Bible I carried everywhere stolen from my van a couple of years ago,I'm back to being stupid.But I think 100% of anything is wishful thinking without outside influences.

I remember reading once how a bike racing grain farmer noticed that grain ran from his silo's faster with square section pipes than round - so he made exhaust systems for his bikes out of square section tubes....worth a try he thought.

[pete376403]

Check this page (seems fairly reputable) for info on a BMW F1 engine (not turbo) http://forums.atlasf1.com/showthread...threadid=61653


Quote " Hmmm interesting figures on the air intake volume (1995 cubic meters)..

18000 rpm (the average between say 17k and 19k as operating range) / 60 = 300 rotation per second. 300 rotations X approximately 1.5 liters of air (not considering fuel added in the cylinders) = 450 liters of air / second = 27.000 liters of air/minute (or 27 cubic meters) = 1620 cubic meters per hour..! That is around 375 cubic meters below the reported data. Which means that forced inductions provides these.. So the engine should be working at around 123% volumetric efficiency. Hmm.."

So +100% should be possible, but in a fairly narrow set of circumstances.

[WINJA]

They're pulling your leg. The only place you will find baffles is in your muffler.

NOT ALWAYS

[WINJA]

.
I doubt that 100% VE can be achieved without forced induction though.

IM NOT A MECHANIC BUT VALVE TIMING AND PERFORMAMCE IN ENGINES GOES WAY ABOVE BEING AN AVERAGE MECHANIC.
THE BEST WAY I CAN TRY TO EXPLAIN IS THAT HAVE YOU EVER HAD A BALL VALVE ON A WATER PIPE , NOTICE WHEN YOU SLAM IT SHUT IT CAN HAMMER, PEOPLE FORGET THERE IS NO SUCH THING AS A VACUM , WE ARE SITTING CONSTANTLY AT 1 BAR , OR 14.7 PSI ABSOLUTE , WELL ON A COMPLEX HIGH REVVING ENGINE WITH A HIGH INERTIA PORT WHEN YOU SLAM THE VALVE SHUT THE AIR CHARGE STILL CARRIES ITS VELOCITY WHICH THEN ADDS A SLIGHTLY PREASURIZED CHARGE TO THE COMBUSTION CHAMBER, AGAIN IM NO MECHANIC , AND NOTE I DID SAY SLIGHT

[FlyingDutchMan]

Check this page (seems fairly reputable) for info on a BMW F1 engine (not turbo) http://forums.atlasf1.com/showthread...threadid=61653


Quote " Hmmm interesting figures on the air intake volume (1995 cubic meters)..

18000 rpm (the average between say 17k and 19k as operating range) / 60 = 300 rotation per second. 300 rotations X approximately 1.5 liters of air (not considering fuel added in the cylinders) = 450 liters of air / second = 27.000 liters of air/minute (or 27 cubic meters) = 1620 cubic meters per hour..! That is around 375 cubic meters below the reported data. Which means that forced inductions provides these.. So the engine should be working at around 123% volumetric efficiency. Hmm.."

So +100% should be possible, but in a fairly narrow set of circumstances.

They've got a RAM air setup, which is a sort of forced induction.
1995 cumecs = 0.554 meters cubed/second @ ~200km/h (~56 meters/second) average means that the intake area needs to be .554/56=0.0099m squared, or 9900 mm squared. Thats comparable to 112 mm diameter intake. They have quite visibly larger one than that (guess @ 200mm). So basically the speed of the car through the air provides the forced induction, and not all of its going in.

RAM air is one mod I do want to do to my bike, but it'll have to wait like the rest of my projects...

[HDTboy]

Notice any change in performance?

No.
10 characters

[Lou Girardin]

IM NOT A MECHANIC BUT VALVE TIMING AND PERFORMAMCE IN ENGINES GOES WAY ABOVE BEING AN AVERAGE MECHANIC.
THE BEST WAY I CAN TRY TO EXPLAIN IS THAT HAVE YOU EVER HAD A BALL VALVE ON A WATER PIPE , NOTICE WHEN YOU SLAM IT SHUT IT CAN HAMMER, PEOPLE FORGET THERE IS NO SUCH THING AS A VACUM , WE ARE SITTING CONSTANTLY AT 1 BAR , OR 14.7 PSI ABSOLUTE , WELL ON A COMPLEX HIGH REVVING ENGINE WITH A HIGH INERTIA PORT WHEN YOU SLAM THE VALVE SHUT THE AIR CHARGE STILL CARRIES ITS VELOCITY WHICH THEN ADDS A SLIGHTLY PREASURIZED CHARGE TO THE COMBUSTION CHAMBER, AGAIN IM NO MECHANIC , AND NOTE I DID SAY SLIGHT

When the intake valve shuts, nothing more can enter that engine.
I guess you're referring to intake charge inertia, which is used to increase cylinder filling. But it doesn't achieve 100% plus.

[pete376403]

They've got a RAM air setup, which is a sort of forced induction.
RAM air is one mod I do want to do to my bike, but it'll have to wait like the rest of my projects...

No - read the whole thread. For a start the engine shown is in a dyno room - no ram effect there. Further F1 regs state there has to be a hole in the back of the airbox to prevent air pressure build up. Mind you, BMW are proably a cut above your average backyard mechanic so don't be surprised if you can't duplicate their figures

[HDTboy]

When the intake valve shuts, nothing more can enter that engine.
I guess you're referring to intake charge inertia, which is used to increase cylinder filling. But it doesn't achieve 100% plus.

When the valves shut they send a pressure wave along their pipes, the waves bounce along the length of the intake throats and exhaust headers. The intake and exhaust can both be tuned so that these waves help fill the cylinder during intake, and help extract the exhaust gasses

[Lou Girardin]

Quite right, but I was pointing out the error in WINJA's post. Namely that when the valve is shut, nothing can enter.

[Motu]

When the valves shut they send a pressure wave along their pipes, the waves bounce along the length of the intake throats and exhaust headers. The intake and exhaust can both be tuned so that these waves help fill the cylinder during intake, and help extract the exhaust gasses

And it's a bit like tuning a guitar,you fall off the sweet spot pretty quick,sometimes it's just not worth it.....but fun to try.

[vifferman]

Quite right, but I was pointing out the error in WINJA's post. Namely that when the valve is shut, nothing can enter.

I think he was talking about the zorst valve, as that is still open after the intake valve opens (overlap). It tricks the fuels and air molly kewls into thinking they can escape ("We're free! FREE!!") so they rush into the cylinder, little realising it's a cunning trap, and they all pile up in a heap, pushed in by those stampeding along behind them. Even though the bureaucrats have specifed there's only room for a certain number, there's always extra that seem to squeeze in, especially if there's party gases involved....