View Full Version : Smaller Header Pipes
Coyote
3rd July 2005, 13:48
I was watching Performance Car TV yesterday and they had an overview of what they had done to this car they were preparing for a competition. They mentioned how they made custom extracters that were slightly smaller than the stock system which resulted in the exhaust having to travel faster giving the engine more power. Homies think making bigger extracters is good for performance but it only makes the exhaust fumes travel slower making the engine more sluggish.
This got me wondering about doing the same to the CBR. Could I improve performance by making header pipes that were made of smaller tube metal or is there a lot of other things you would have to modify to benefit from this that they didn't mention?
onearmedbandit
3rd July 2005, 14:19
Exhaust science is quite complicated, tuned length headers, opitimum diamater, etc. A lot to do with scavenging from exhaust pulses etc, ie as one cylinder has completed it's compression stroke and expelled the gases, the vacuum created by the leaving pulse sucks the next cylinders (in the firing order) 'pulse' out as well, making the engine more efficient. Reducing the diamater will speed up the flow of the exhaust, but it maybe at the expense of another area of its performance. More so than a lot of other mods, exhaust systems need to be designed as a complete unit to get noticable gains, from what I understand (correct me if I'm wrong) this even includes the shape of the airbox (induction side).
But, if you've got the time and ability it would be a good experience for you to try something.
Coyote
3rd July 2005, 14:23
Thanks for the response. I was thinking of making header pipes for a metalwork project at school (currently making a rear stand for a sportsbike), if they didn't work out I could always revert back to stock anyway
onearmedbandit
3rd July 2005, 14:55
Nothing to loose by trying as you can always revert back to standard as you say. I must say though the Japanese are very good at getting the whole recipie right the first time, but I'd be interested to read of your results. You'll definately want to do some dyno-testing though, as even a change in exhaust note and feel can make a bike 'seem' faster or slower. Good luck.
There are formulas for pipe diameter and length,I've posted them here before I think,but as my books are still packed away I can't find them (sunday afternoon project,unpack my books?) The exhaust gases and the exhaust noise are two different things,one travels down the pipe at aproximatly the speed of sound,the gases are needed to move at around 300 ft/sec at max rpm,the smaller the dia the faster they move - most stock pipes are about one size too small as this boosts bottom end HP.Very early Triumphs had huge fat pipes because they thought that was a good idea,but the gases traveled too slow - so later models,say 60s models,actualy stepped down in size from the exhaust port....check out a 69 Bonnie.I'll post some formulas when I find my books later.
Found them - exhaust pipe length...L=V 120/N
L=length of pipe
N= engine speed in rpm
V= velocity of wave in ft/sec
Velocity of the wave is variable to some degree,if you use a figure of 1700ft/sec it'll get you close enough.
Pipe dia formula is - V=piston speed/60 X D squared/d squared
V=gas velocity in ft/sec
D= piston dia
d=inside pipe dia.
piston speed=Stroke X 2/ 12 X rpm,this gives ft/min so divide by 60 for ft/sec.
It all sounds pretty complicated but it's fun to play around with - I used to do this stuff before calculators....and I didn't take maths as a subject at school.Enjoy yourself,I do.
onearmedbandit
3rd July 2005, 15:24
Did you mean this one Motu?
http://www.kiwibiker.co.nz/forums/showthread.php?t=9550&highlight=exhaust+formula
Look for Motu's post.
Coyote
3rd July 2005, 16:09
Mustn't forget installing a flamethrower system as well :whistle:
WINJA
3rd July 2005, 19:04
I was watching Performance Car TV yesterday and they had an overview of what they had done to this car they were preparing for a competition. They mentioned how they made custom extracters that were slightly smaller than the stock system which resulted in the exhaust having to travel faster giving the engine more power. Homies think making bigger extracters is good for performance but it only makes the exhaust fumes travel slower making the engine more sluggish.
This got me wondering about doing the same to the CBR. Could I improve performance by making header pipes that were made of smaller tube metal or is there a lot of other things you would have to modify to benefit from this that they didn't mention?
AT FULL REVS THOSE SMALL 250 LIKE YOURS HAVE OVER 100% VOLUMETRIC EFFICIENCY , ID TAKE A $20 BET THAT YOULL ONLY MAKE IT WORSE
Jamezo
3rd July 2005, 19:48
AT FULL REVS THOSE SMALL 250 LIKE YOURS HAVE OVER 100% VOLUMETRIC EFFICIENCY , ID TAKE A $20 BET THAT YOULL ONLY MAKE IT WORSE
over 100% efficiency, cor blimey!
"Lisa, in this house we obey the laws of thermodyNAMICS!" - Homer Simpson
marty
3rd July 2005, 20:24
i think he meant that it was as volumetrically efficient as it was going to get, therefore it was, for all intents, operating at 100% of its ability.
Coyote
3rd July 2005, 20:50
AT FULL REVS THOSE SMALL 250 LIKE YOURS HAVE OVER 100% VOLUMETRIC EFFICIENCY , ID TAKE A $20 BET THAT YOULL ONLY MAKE IT WORSE
Always room for improvement though
marty
3rd July 2005, 20:52
the engines i work on are allowed to run go 105% for short periods of time, with 100% being around 32000rpm, 3750 ftlbs of torque. they can sustain 5000 ftlbs in an emergency though
NordieBoy
3rd July 2005, 21:08
Have a look at MotoMan's (http://mototuneusa.com) website.
If you can get past the garish colours etc then you'll find out about "velocity porting" etc etc.
See what you think.
HDTboy
3rd July 2005, 21:14
I'd also vote for over 100% volumetric efficiency, and also think you'll only make things worse by putting smaller headers on. You may make a bit more torque down low but I'd say you'll lose the need for a 19'000 redline
WINJA
3rd July 2005, 21:17
Always room for improvement though
IF PEOPLE LIKE 2 BROTHERS ARE FUCKING UP EXHAUSTS ON 250S YOU HAVE NO
CHANCE.
WINJA
3rd July 2005, 21:23
i think he meant that it was as volumetrically efficient as it was going to get, therefore it was, for all intents, operating at 100% of its ability.
I MEAN THAT CAUSE OF THE ENGINE SPEED AND CAM TIMING IN CONJUNCTION WITH THE EXHAUST AND INLET SHAPE THE CYLINDER CHARGE AT HIGH RPM IS SLIGHTLY HIGHER THAN ATMOSPHERIC PREASURE , IE HIGHER THAN 14.7PSI ABS OR 101KPA ABS.
THIS EQUATES TO A SLIGHT SUPERCHARGING EFFECT
Coyote
3rd July 2005, 21:28
IF PEOPLE LIKE 2 BROTHERS ARE FUCKING UP EXHAUSTS ON 250S YOU HAVE NO
CHANCE.
You're doubting my abilities? Think I'm gonna cry now (sob)
Even if I have no hope of improving the performance it'll still be fun to give it a go. I haven't got anything to lose as I'm not going to cut up my original headers of course
WINJA
3rd July 2005, 21:30
You're doubting my abilities? Think I'm gonna cry now (sob)
Even if I have no hope of improving the performance it'll still be fun to give it a go. I haven't got anything to lose as I'm not going to cut up my original headers of course
WELL DO IT THEN IF YOU WANT TO WASTE YOUR TIME DOING THAT SHIT INSTEAD OF HELPING WINJA PAINT HIS ROOF
The Preacher
3rd July 2005, 21:32
As "Vance and Hines" say, alter the exhaust then you must re jet the carbs to gain the benefits or you will be worse off.
Coyote
3rd July 2005, 21:39
WELL DO IT THEN IF YOU WANT TO WASTE YOUR TIME DOING THAT SHIT INSTEAD OF HELPING WINJA PAINT HIS ROOF
If I did make them in metalwork, all it would require is bending a few pipes. Easy NCEA credits :2thumbsup
WINJA
3rd July 2005, 21:40
As "Vance and Hines" say, alter the exhaust then you must re jet the carbs to gain the benefits or you will be worse off.
AND AN OLD AKRAPOVIC INSTRUCTION BOOK SAYS VANCE AND HINES ARE WRONG YOU CAN GET A PERFORMANCE GAIN ACROSS MOST OF THE RANGE BY BOLTING ON A AKRAPOVIC WITH NO OTHER CHANGES, AFTER TRYING ARROW , VANCE AND HINES AND AKRAPOVIC ON THE SAME RACE/ROAD BIKE ID HAVE TO SAY AKRAPOVIC ARE THE MASTERS OF PERFORMANCE EXHAUSTS.
VANCE AND HINES IS A HAS BEEN COMPANY
RiderInBlack
3rd July 2005, 22:18
A lot of famous inventors have been told by "Experts" that they couldn't achive what they were trying to achive. Thank God they didn't let that stop them from trying anyway.
My advice is listen to the advice you are given, but don't let that stop you from trying. At the very worst is that you will learn by practical experience why the "Experts" are right. At the best you will come up with a new (maybe better) way of doing or makeing something.
Go for it:Punk:
pete376403
3rd July 2005, 22:32
Agree with RiB, but remember Honda have forgotten more about tuning that the aftermarket pipe makers will ever know.
Also agree with WINJA about +100% VE - it can be done but the trade off will be a very narrow power band and crap performance outside of this range. The old British race singles were a good example of this - "megaphonitis" was the word used to describe it - or the old piston ported two strokes with expansion chambers and a razor thin power band.
HDTboy
3rd July 2005, 22:36
CBR250s like mine and alurumbas make max torque at 11'500, and max power at 15'000 indicating a relatively narrow powerband, and I'm still supporting the theory of +100% VE.
I don't think you'll improve anything alurumba, but I'm interested in seeing what results you do get
NordieBoy
3rd July 2005, 22:44
CBR250s like mine and alurumbas make max torque at 11'500, and max power at 15'000 indicating a relatively narrow powerband, and I'm still supporting the theory of +100% VE.
I don't think you'll improve anything alurumba, but I'm interested in seeing what results you do get
Sounds like they're a little too free-flowing.
A bit more back-pressure (smaller headers/exhaust) may help move the peak down the rev-range or help broaden it out.
You'll notice less power on top but you may just get there quicker :)
Give it a go alurumba :D
Oh and how much do you mean by "smaller"?
What diameter are the originals?
HDTboy
3rd July 2005, 22:52
Most of the time you have at least 8000 revs aboard anyway, it's a different riding style. To get the most benefit, one would need to change cams, and the fuel and ignition curves
WINJA
4th July 2005, 10:33
HAVE YOU GUYS SEEN THE MICRON HYDRATECH HEADERS, IT MUST BE A GREAT IDEA COS HONDA HAVE COPIED IT
SPORK
4th July 2005, 19:25
Wouldn't it just be a better idea cleaning out the old smelly header pipes, polishing them or soemthing so that the gasses can flow freer? That seems to be the best idea I think, that way you get OEM headers with improved flow.
But I'm probably wrong. Time to go paint Winja's roof.
WINJA
4th July 2005, 20:13
Wouldn't it just be a better idea cleaning out the old smelly header pipes, polishing them or soemthing so that the gasses can flow freer? That seems to be the best idea I think, that way you get OEM headers with improved flow.
But I'm probably wrong. Time to go paint Winja's roof.
YAY PAINT MY ROOF
SPORK
4th July 2005, 20:20
YAY PAINT MY ROOF
Sure thing, my services of the roof-painting variety cost around $20 an hour.
This got me wondering about doing the same to the CBR. Could I improve performance by making header pipes that were made of smaller tube metal or is there a lot of other things you would have to modify to benefit from this that they didn't mention?
If you have a look at the size of the headers on, say an old GSX 750 or any early eighties bike, compared to what is on your bike, you should see that those tricky little aisian fellows have got their finger on the pulse. My 87 fizzer pipes, are inch and a quarter, my mates GSX, inch and three quarters. And there is a marked power difference between the two.
WINJA
4th July 2005, 20:22
Sure thing, my services of the roof-painting variety cost around $20 an hour.
$20 , FUCK OFF
$20 , FUCK OFF
Gimmie some speights and I will HELP paint your roof, min = 24.
As "Vance and Hines" say, alter the exhaust then you must re jet the carbs to gain the benefits or you will be worse off.
Can't be true, I made my own end can, and got more poke all the way through the revs.
And that is just a chunk of two inch perferated pipe, inside a four inch stainless sleeve, packed with pink batts.
SPORK
4th July 2005, 20:27
$20 , FUCK OFF
Ok, ok, I'll do it for a ZXR250C :yes:
Can't be true, I made my own end can, and got more poke all the way through the revs.
And that is just a chunk of two inch perferated pipe, inside a four inch stainless sleeve, packed with pink batts.
How does that sound?..
Gimmie some speights and I will HELP paint your roof, min = 24.
Speights pays for all :yes: I'm with you !
How does that sound?..
Actually sounds really good, deep and not too loud
Here is a pic if you are interested
Here is a pic if you are interested
Sweet! I've done the same thing - Cant wait to hear it - your can looks nice n'tidy
WINJA
4th July 2005, 20:37
Actually sounds really good, deep and not too loud
HEY IF YOU EVER FIND THE MUFFLER IS TO LOUD YOU JUST ADD MORE HOLES TO THE PERF OF VARYING SIZES , I HAVE NO SCIENTIFIC PROOF BUT I THINK IT
WORKS CAUSE DIFFERENT SOUND WAVES GO THRU DIFFERENT SIZED HOLES BETTER ,THIS CAN SOMETIMES TAKEAWAY THE HARSHNESS OR RASPY SOUND FROM SOME BIKES, ALSO DONT UNDER PACK OR OVER PACK THE MUFFLER.
Sweet! I've done the same thing - Cant wait to hear it - your can looks nice n'tidy
Came up all right, woulda looked better if I could have use polished pipe, instead of brush finish, but the father in law works at a scrap yard, so I took what was free.
HEY IF YOU EVER FIND THE MUFFLER IS TO LOUD YOU JUST ADD MORE HOLES TO THE PERF OF VARYING SIZES , I HAVE NO SCIENTIFIC PROOF BUT I THINK IT
WORKS CAUSE DIFFERENT SOUND WAVES GO THRU DIFFERENT SIZED HOLES BETTER ,THIS CAN SOMETIMES TAKEAWAY THE HARSHNESS OR RASPY SOUND FROM SOME BIKES, ALSO DONT UNDER PACK OR OVER PACK THE MUFFLER.
I packed it in as tight as it would go, but that is cos I used pink batts, of the common wall variety, and I wanted it to work.
Coyote
5th July 2005, 10:55
I was told by a few mates at school (so this probebly isn't the most reliable info I've been given) that there's likely to be baffles in the header pipes. This true? If I made a replica set of header pipes without baffles, would this change performance for better or for worse?
Baffles are placed in a controlled area where they will be most benificial to both the high and low end, the can, some headers have kinks in them that provide a baffle type effect... But not to the same level..
Screw the crap, get the can, gut it, shove a perferated tube in it and run away laughing...
bungbung
5th July 2005, 11:02
I was told by a few mates at school (so this probebly isn't the most reliable info I've been given) that there's likely to be baffles in the header pipes. This true? If I made a replica set of header pipes without baffles, would this change performance for better or for worse?
They're pulling your leg. The only place you will find baffles is in your muffler.
Coyote
5th July 2005, 11:09
Baffles are placed in a controlled area where they will be most benificial to both the high and low end, the can, some headers have kinks in them that provide a baffle type effect... But not to the same level..
Screw the crap, get the can, gut it, shove a perferated tube in it and run away laughing...
Perferated tube? Sound interesting
I wonder if you could make a Turbocharger/Pulsejet exhaust system :devil2:
They're pulling your leg. The only place you will find baffles is in your muffler.
Baffles in the muffler yes,but some bikes have a restrictor in the header pipe,part of the derestriction process is to remove these.
Coyote
5th July 2005, 12:10
Baffles in the muffler yes,but some bikes have a restrictor in the header pipe,part of the derestriction process is to remove these.
How do these restrictors work? Are they like baffles?
How do these restrictors work? Are they like baffles?
Normally washers or kinks. (mainly in smokers)
Coyote
5th July 2005, 12:21
Normally washers or kinks. (mainly in smokers)
Ah stuff it. I'll just remove the header pipes :p yes I relise how stupid this would be, I did it to a Mitsi Chariot
Sounds good but kiss your valves goodby, like I said perferated tube, no packing.. legend sound.. I just tested mine.. me likes.
Coyote
5th July 2005, 12:32
Sounds good but kiss your valves goodby, like I said perferated tube, no packing.. legend sound.. I just tested mine.. me likes.
What's a perferated tube and how did you do whatever to your muffler? I thought modifying my stock muffler or debaffling it would result in sluggish performance?
http://www.aardvark.co.nz/pjet/
Yeah, one of those on the CBR would be sweet
In theroy it depends what you want, the debate of backpreasure is so hot aired I wont get into it, All I can say is your going to loose low end (in most cases)...I got the exhaust of taka mc wreckers they have them on trademe, I just drilled it out and took out the packing and am trying to fit it on to my pipe cleaner than the current method...
'm sure motu will be more insightful - because i am a young testosterone driven teenager, Its all about sound... Apparently...
Coyote
5th July 2005, 12:42
In theroy it depends what you want, the debate of backpreasure is so hot aired I wont get into it, All I can say is your going to loose low end (in most cases)...I got the exhaust of taka mc wreckers they have them on trademe, I just drilled it out and took out the packing and am trying to fit it on to my pipe cleaner than the current method...
'm sure motu will be more insightful - because i am a young testosterone driven teenager, Its all about sound... Apparently...
Low end is already crap so I keep above 14k (on the track, I'm more conservative on the road) so if I can make top end better from sacrificing bottom end, I'm not really losing in the end
Also I was thinking of changing the rear sprocket to one with a few more teeth, but that's another story
I would be more inclined to drop the front a tooth dunno why, just because thats cooler ;)...
Does the CIBBER have a 18rear? try to slap a 17 on it..
I havent had any full riding experience with my bike running a proper straight through but I would imagine it wouldnt be fun at all, tristan runs a budget straight through ask him.. He cant really make up his mind about it lol :\
Coyote
5th July 2005, 12:52
I would be more inclined to drop the front a tooth dunno why, just because thats cooler ;)...
Does the CIBBER have a 18rear? try to slap a 17 on it..
Not sure what it has at the moment. I wanted better accel so I could get ahead of the RGs at the start instead of having to back off and wait untill I got to a straight to pass them. Although, the problem with all these mods is they're not allowed in streetstock anyway, but then again the VMC don't scrutineer the bikes :shifty:
thats not very sportsman like of you! *spanks*....*spanks some more*....*enjoys*
onearmedbandit
5th July 2005, 12:56
You'll find it easier and cheaper to drop one tooth on the front rather than getting a sprocket with more teeth at the rear. Why? Because you shouldn't have to change your chain.
Coyote
5th July 2005, 12:59
thats not very sportsman like of you! [other bullshit typical of John]
But in the first race 2 stupid RGs were riding together and I couldn't get around them, second race at the first corner a ZXR tried to swipe my front tyre, fortunately I backed off in time or there would've been a major pile up, and the third race a RG crashed into me and thats what has sent me off the road and track for 2 1/2 months! I need to actually qualify (they stopped me from doing that as they had to explain to beginners like me what each flag was) and get ahead of them so they can't hurt me or slow me down
HDTboy
5th July 2005, 13:03
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
5th July 2005, 13:06
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
5th July 2005, 15:43
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?
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
5th July 2005, 17:00
Check this page (seems fairly reputable) for info on a BMW F1 engine (not turbo) http://forums.atlasf1.com/showthread.php?s=&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
5th July 2005, 17:29
They're pulling your leg. The only place you will find baffles is in your muffler.
NOT ALWAYS
WINJA
5th July 2005, 20:03
.
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
5th July 2005, 20:14
Check this page (seems fairly reputable) for info on a BMW F1 engine (not turbo) http://forums.atlasf1.com/showthread.php?s=&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
5th July 2005, 21:08
Notice any change in performance?
No.
10 characters
Lou Girardin
6th July 2005, 13:15
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. :wait:
I guess you're referring to intake charge inertia, which is used to increase cylinder filling. But it doesn't achieve 100% plus.
pete376403
6th July 2005, 14:24
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
6th July 2005, 15:36
When the intake valve shuts, nothing more can enter that engine. :wait:
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
6th July 2005, 15:54
Quite right, but I was pointing out the error in WINJA's post. Namely that when the valve is shut, nothing can enter.
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
6th July 2005, 16:19
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....
FlyingDutchMan
6th July 2005, 16:34
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
I did, and this was part of it:
(I think that these are things that they're not allowed to do).
1.12 Supercharging :
Increasing the weight of the charge of the fuel/air mixture in the combustion chamber (over the weight induced by normal atmospheric pressure, ram effect and dynamic effects in the intake and/or exhaust system) by any means whatsoever. The injection of fuel under pressure is not considered to be supercharging.
So they are allowed to increase the air intake by using a RAM air setup, intake and exhaust tuning and pumping fuel into it. They're not allowed to use intercoolers or other such flash gadgetry.
But point taken with the bench test...
WINJA
6th July 2005, 17:33
When the intake valve shuts, nothing more can enter that engine. :wait:
I guess you're referring to intake charge inertia, which is used to increase cylinder filling. But it doesn't achieve 100% plus.
WHAT ABOUT AT BDC IS THERE STILL IN RUSH, REALLY I HAD NO IDEA WHAT THE DUDE WAS TALKING ABOUT , ALL I KNOW HIS HE BUILT GOOD ENGINES
Coyote
6th July 2005, 17:45
"The louder the pipe, the more power it has" - Straight from the Homies mouth. Thought he was bullshitting, sadly he wasn't :no:
"The louder the pipe, the more power it has" - Straight from the Homies mouth. Thought he was bullshitting, sadly he wasn't :no:
Not how it works. In theory, the more gas that escape from the exhaust, the more power you can extract, but you have to play with all the other variables, this is a can of worms you might want to study for a degree in engineering befor you open.
I think you should check the headers for restictors, gut the pipe, and jet the carbs.
If you start fucking with the rest of it, you could go backwards, and unless you got a spare bike, that leaves you kinda screwed.
DEATH_INC.
6th July 2005, 19:09
Making headers is great fun,have a go.....
If you look at motu's formulas you'll see that size is relevant to both bore and stroke,and rpm.Length is only relevant to rpm.....But I've found these formulas don't really work for bikes,you'll often end up with a length of 15" or less......
Smaller will give more low rpm grunt at the expense of top end and of course vice versa.
Start with the stock sizes,make one set 1 pipe size smaller,and an inch or so longer and make another set 1 size bigger and an inch or so shorter.Try making the smaller set 4>2>1 too,it tends to add more midrange.Make your tail pipe about 1 1/2 times the size of your headers and use a straight through muffler.
If you have pipe expanders you can make slip joints under the engine and add different lengths in too.
Outta interest I've found around 28" long seems to work on 750's and thous etc.I prefer 4>1 myself,but then I always chase top end.....
I've also seen a study in a cage mag where they experimented with backpressure,as the rumour has been that some actually helps a bit,but they found to the contrary,as any backpressure they introduced made a definate reduction in power.
RiderInBlack
6th July 2005, 20:32
Doesn't Yammy's have the Exup thingy in the pipes/collector that is suppose to boose the power?
How does that work and could it be applied here?
Just curious.
WINJA
6th July 2005, 20:41
Doesn't Yammy's have the Exup thingy in the pipes/collector that is suppose to boose the power?
How does that work and could it be applied here?
Just curious.
WORKS BETTER WITHOUT IT ON MODERN BIKES , THE ZX10 R1 CBR1000 AND GSXR1000 ALL HAVE THEM BUT YOU TAKE THEM OFF TO GET REAL POWER, THEY ARE THERE FOR NOISE TEST I RECKON , I GOT INSTRUCTIONS FROM YOSHIMURA ON HOW TO REMOVE MINE , AND FUCK IS IT BETTER , EVEN THE MECHANIC WHO JUST RODE IT RECENTLY SAID IT WAS FUCKEN GOOD
FlyingDutchMan
6th July 2005, 22:34
I've been thinking of making adjustable length headers. Have the 4-1 at quite a short distance from the engine, then have 'slider' bits that go inside them and can extend out. So at low revs it'll be all the way out & long, and as you rev it up the go in further & get shorter. Still haven't quite managed to work out how to make them move magically yet though. Would be wicked to have a wide powerband.
Ixion
6th July 2005, 22:42
I've been thinking of making adjustable length headers. Have the 4-1 at quite a short distance from the engine, then have 'slider' bits that go inside them and can extend out. So at low revs it'll be all the way out & long, and as you rev it up the go in further & get shorter. Still haven't quite managed to work out how to make them move magically yet though. Would be wicked to have a wide powerband.
Ferrari did this on one of their V12 F1 engines. More practically I think some racing gokart engines use the same idea
Looks like I am the only one who thinks, fucking with a 250 seems a lot like throwing money away.
Having said that, once I get an idea on how to get more power out of anything, (including my generator motor,) I can't be talked out of it, hence my falcon is getting a pair of hair driers, (turbos for those not up with the lingo).
So give it a go, at the end of the day, as long as you don't hack up the stock bits, they can go back on.
Have fun, and be sure to post the results :Punk:
Making headers is great fun,have a go.....
If you look at motu's formulas you'll see that size is relevant to both bore and stroke,and rpm.Length is only relevant to rpm.....But I've found these formulas don't really work for bikes,you'll often end up with a length of 15" or less......
Smaller will give more low rpm grunt at the expense of top end and of course vice versa.
I forgot to mention,although it was in the link to the other thread...double the result for a good length for a bike,catch the wave next time round.I also have the formula for intake length.Most of this stuff was done in the 40s and 50s on car systems,we have come along way since then,but I haven't seen any formulas for modern day engines.You can actualy hear a good exhaust when you get it right.
All the advances in modern times have been combustion chamber design,port design and cam profile - not cam timing.If you look at cam timing figures for engines say pre 70s and compare them to the engines we have today the modern engines have almost lawnmower camshafts...it's how they open them that has changed,and then how the gases flow through ports,around valves etc.
FlyingDutchMan
7th July 2005, 19:43
Looks like I am the only one who thinks, fucking with a 250 seems a lot like throwing money away.
Having said that, once I get an idea on how to get more power out of anything, (including my generator motor,) I can't be talked out of it, hence my falcon is getting a pair of hair driers, (turbos for those not up with the lingo).
So give it a go, at the end of the day, as long as you don't hack up the stock bits, they can go back on.
Have fun, and be sure to post the results :Punk:
Perhaps it is throwing money away, but producing more power and actually being able to use most of it most of the time has more use than 500bhp on a 'busa. And it'd be a great project to play around with (just like FI). Planning on getting a new bike (CBR600) in the next year, and turning the wee cibby into a full out project mobile.
Looks like I am the only one who thinks, fucking with a 250 seems a lot like throwing money away.
Having said that, once I get an idea on how to get more power out of anything, (including my generator motor,) I can't be talked out of it, hence my falcon is getting a pair of hair driers, (turbos for those not up with the lingo).
So give it a go, at the end of the day, as long as you don't hack up the stock bits, they can go back on.
Have fun, and be sure to post the results :Punk:
Yea but your normal, people like to be different - if they didnt then think what the world would be....
speedpro
7th July 2005, 21:28
I've been thinking of making adjustable length headers. Have the 4-1 at quite a short distance from the engine, then have 'slider' bits that go inside them and can extend out. So at low revs it'll be all the way out & long, and as you rev it up the go in further & get shorter. Still haven't quite managed to work out how to make them move magically yet though. Would be wicked to have a wide powerband.
It's been done on a bucket sort of. It had a rear cone within the rear cone. The inner cone was moved by a push/pull cable hooked up to something like a powervalve controller. It worked quite well. The same bucket had the stinger exiting out the side of the centre section. 2-strokes of course but the idea is the same - vary the tuned length.
DEATH_INC.
8th July 2005, 20:05
I forgot to mention,although it was in the link to the other thread...double the result for a good length for a bike,catch the wave next time round.I also have the formula for intake length.Most of this stuff was done in the 40s and 50s on car systems,we have come along way since then,but I haven't seen any formulas for modern day engines.You can actualy hear a good exhaust when you get it right.
All the advances in modern times have been combustion chamber design,port design and cam profile - not cam timing.If you look at cam timing figures for engines say pre 70s and compare them to the engines we have today the modern engines have almost lawnmower camshafts...it's how they open them that has changed,and then how the gases flow through ports,around valves etc.
Funny,the formula I normally use comes from a '67 car mag......Yeah,doubling the length does bring it pretty close,and I guess once you calculate the cam timing into it you'd prolly be pretty bloody close....
Lorcan,the guy that runs the Turbo site I go on,had his cams reprofiled by a mate who worked on formula 1 engines (lotus I think),same timing,just a different profile,with very good results.Like you say they're always getting better...
Can you send me a copy of the intake length calculations?I've never found a decent one.....
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