HIGHER EXHAUST PORT, GOOD IDEA? How Exhaust Port Timing Affects Two Stroke Performance.
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- Опубліковано 24 лип 2024
- When tuning 2 stroke engines raising the exhaust port is common practice. In this video I explain why a higher port not necessarily is a good thing. In one word, resonance.
Check out my other videos on two stroke technology too!
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I really appreciate you putting the time to educate us on the lesser known facts of two stroke engines. I mean anyone has the concept of switching the air filter for a "performance" one, changing gear ratios, different spark plug, etc. But this stuff is a bit more outside the box and very intriguing
Thanks!
@monkey, this is definitely not outside the box on 2stroke engines. Porting the intakes and exhaust ports on a 2 stroke is basically the same as putting a bigger, performance cam in a 4 cycle engine..
This makes me want to tune my friends moped thats been sitting outside my garage for a few months
+Ben Lauderdale GO!
This totally blows my mind especially when just used to big cc snowmobile engines
This brings back so many memories =D I love the Peugeot sp, 103 and this newer one you are working on. If only we had mobile phones back in the day when I was working on those moppets lol.
+www.skyblock.nl Cool!
The. More you raise the exhaust port more blow down is created.
Too much blow down is what kills the bottom end.
So sometimes you have to increase transfer (raise transfer ports) timing as well to keep the right blowdown ratio.
When is the video about changing your balancefactor coming? btw, love your videos. They're instructive, not too long nor short, and you explain everything so well, good job man! Keep up the good work! :)
+MatarengiMoppers Thanks! Not quite sure, lots of stuff going on atm. Won't be too long tho! I just received a new crank for the Spx and I'm pretty sure it has the wrong factor for my setup, I'll use that to show what to do.
Love your videos very informAtive you defenitely need a television channel I'd watch every saturday faithfully at breakfast
+demetrius thomas Thanks!
Very informative video. Thanks for you explanation
That is a good explanation of raising the exhaust port but what happens if you lower it. I have just resleeved a two stroke cylinder and I reduced the port timing from 190 to 185.5. This was done at the same time as widening the ext port to achieve more area than before. I was hoping this would result in a longer power stroke.
Very usefull info ! Thanks ! Will use this for my KR1S !
+Jack Postma Thanks! You're welcome!
Thanks for the tutorial.
Very informative. Thank you 🙂
Thanks!
You probably don’t think so but your explanations are easily retainable!!! Give yourself more credit my good friend! Appreciate all the time, energy and funds that you put in for the channel!!
Thank you for the video. Very informative!!!
+Frank Crawford Thanks!
Hello thank you for your video's. What happens to performance when you block off the converging cone exit .... and re route the silencer pipe to the belly area instead. Thus a side exit bend to the silencer instead of conventional exit at rear of converging cone. Hope I made sense.
With all the issues fuelling the spx with nitro, does the different fuel affect the resonance? As in it depending which fuel used burns/bangs faster or slower the petrol,, meaning faster or slower pulses etc etc
sir i wanna ask, if im using over bore cylinder 59mm to 61mm have power valve..exhaust port should be hi also? mean,adding more gasket for cylinder? ..how about the head,need adjustment?..need your help sir..
How about chain saw engines with no pipe. We raise the exhaust port ceiling, and lower the intake port. Then we cut about 1/8” from the bottom of the piston skirt. I wish I knew more. I port Husqvarna dirtbike vintage engines and they respond very well. Like your videos.
the only easy way to do this for me is wack another gasket between the barrel and bottom end, this will also raise my intake, what effects will this have? my motor is a yamaha kt100j (13hp) it revs to about 11280rpm, i managed to get it to compete with its destroked higher output cousin (kt100s) but i seem to run out of power at around 10800
Great explanation! For those who dubt about i suggest learn about time/area and more specific on blowdown time-area, in your case your positive performance are an e sample of the possibile with clever way! Aniway Thank you to Walter kaaden from mz we know also That timing lesso Thank 180 does nt work perfectly with pipe tuning..
+Vns workshop Thanks!
Hi m8, i like your videos a lot, maybe you can give me a hint with my bike. I have a 2018 Aprilia RX50 with engine d50b0, i took off everything that is restricting it, i installed aftermarket cdi, leovince xfight exhaust, polini cp19 carb moded with different jets and now i have a proper piston wash with 49low jet; 90 mainjet; neddle 12/22 clip position 1 above midsection, airsal 74.2 bbk, i kept the stock air filter, malossi vl6 reeds kit, gears 11/50. I would like to get more torque in low band, i use it only on mud and forest, don't need speed too much.... I would appreciate any advice. Thanks
Good series of videos. I'm really enjoying it. Might also be worth noting that the volume above the exhaust port is a sealed chamber containing a huge explosion so earlier you open the exhaust port the earlier the pressure escapes into the exhaust. The force on the piston (and the work done) drops suddenly as soon as the exhaust port is open.
+ametti000 Thanks! True, but then there's the balancing act between energy used to push piston and energy left for the pipe. Might be a video.
And on day 7 god invented the power valve
No, Yamaha did.
Hahaha, word! Those old 350's were so much fun....
I thought Kawasaki was the first to implement an exhaust valve on a 2t.
I'll have to trust you guys. I had quit racing ring-dings long before power valves appeared on production bikes.
Hahaha that he did... That he did...
If the exhaust port timing is too high can this be corrected with retarding the ignition? My 85cc dirtbike pops when wot more than 2 seconds jetting is correct. 105 BBC kit installed
On 200 degrees on a 125cc running methanol, Reverse fuel pressure with a readout, change the timing depending and reduce cooling with with tape on the radiator, and also start rich with jetting and work your way down. My 125cc engine dyno’d at 39.7hp in 1997. And also drop one of the piston rings (bottom one)
Great job with the videos
+boldmobleify Thanks!
So can this contribute to a weak power band? if not, then what makes a power band sluggish?
Sir, I need such a help. I want to ask about the port of such a cylinder, how can we increase the speed from its port. Please help me. Please tell me.
Hello guy! Does the exhaust manifold/flange length have any effect on resonance? If so, can anyone please tell me what the difference would be using a shorter and a longer one? Thanks in advance.
The pipe in effect starts at the piston face so yes, it's basically part of the header.
With a piston ring out of the bore what should the gap be? I'm asking because I am curious to know how much tension the ring should put onto the cylinder wall when inserted in the bore around the piston?
.003" for every inch of diameter of the piston
Alex, nice explain, lots of pen action, can't go wrong with pen action,
well at least until the ink runs out.
To add abit of info for you and AuMechanic (good basic chamber videos,
thumbs up).
When engines run, they don't run at a constant rotational speed all the
time thru the cycle.
So say your rpm meter is displaying 11000rpm, this is the mean rpm,
measured at one point in the 360* rotation. If you were to measure the
instantaneous crankshaft angular velocity (done with an encoder with the
output quad'd to get the resolution down to 0.1-0.2*) on a single
cylinder 2 stroke you'll find the instant varies from the mean by as
much as +/- 250rpm, 500rpm P-P. The undervalue bottoms around exhaust
port open which then gains rpm until the overvalue top just before BDC
and then loses rpm back down to the undervalue at exP open.
So its not possible to use simple maths for the time that the exP is
open and closed and this has an effect on why the natural port duration
for resonance usage is not 180* along with other factors involving the
sonic wave speed in the pipe itself.
+cara vaggio Thanks! (got stuck in the spam filter...)
Hello, I'm just getting into motorized bicycles and this vid brings a question to mind; is resonance a factor in the intake as well? Also, if so how is it different from the exhaust resonance as far as affecting performance?
Yes it is, in fact it's a factor throughout the whole engine, the whole system needs to be "in tune" for best results.
Excellent! So you could get a custom pipe to match for the added height though?
Yes, a different pipe might be needed.
2:28 damn you convinced me
+Semnick Semnome haha, great! Thanks!
haha That was the same moment for me too.
hello.. sorry I am commenting on an old video.. People always discuss about raising and lowering the port and it will indeed change the power curve of an engine. what happened if we tweak the bottom part of the port, i.e making the port longer down the cylinder, but not changing the port timing. what will happened then? I hope you can explain it if you have this kindof experience. thank you.
In short lowering the port floor beyond where the piston stops at bdc won't do much at all, in some cases raising it can have a positive effect on power due to less short circuiting and a smaller duct resulting in higher gas velocity during blowdown.
... which results in better scavenging.
if there is one guy i take advice from, then it is from you sir. 👌
Cool video bro !!! I got a old 250 with piston port set up I’m trying to get it running I put new piston rebuild the carb it’s trying to start but no luck what do u think is wrong
+david voges Thanks! Hard to say, need more info...
Thank you!
Have you ever seen a Agria 1700? This is a old kind of "Tractor" don't know the name in english. In german its called "Einachser". The Agria has an Hirth 250cc Engine 2 Stroke! They are racing in the dirt with these Agria's... maybe a Agria would be a perfect Project for you?
I just put on a 60cc cylinder on my moped and the exhaust port is "too high", for me at least. It has no torque at all but from like 7 or 8000 rpm the hp is insane and its sketchy to ride. I would wish that it had a little more of both since the old 49cc one had all the torque...
Do you have an educational background in design? Because you're always spot on with your drawings and you always seem to know how to make helpful diagrams
Thanks! No design background.
Good content.
Hi! Me and my friend building a peugeot fox for mopedcross. Do you have tips for porting the original 50cc?
Does it have to be the stock cylinder? Probably a pretty bad starting point.
Thanks for the reply! Nope, but it has to be 50cc and i have been told that the original 50cc isn't that bad.
i raised the exhaust port on my motorised bike it doesn’t rev quite as hard now but i also don’t have an expansion chamber will it be better with an expansion chamber ?
Obviously
I raised the exhaist port on my cylinder i was just wondering How will know when driving if ive raised the exhaust port to high.
After about 190° you'll start shrinking the rpm range in resonance, if you go too far it'll shrink to such a narrow range it becomes practically unusable - you've made a doorstop...
ive seen guys going 200, does higher timing results to a higher rpm range but lower on torque?
Has anyone tried a variable length pipe on a two stroke? Can't easily lengthen a cone, but maybe a short telescopic straight part between the diffuser and the end cone?
Yes my dad did on his rc plane 30 years back. Was a 50cc boxer
This is a great topic
+Barter Fiend yep! Thanks!
Simply put 👌
but leaving the tube long on the carburetor you gain torque for what you lose in expansion chamber so I don't think I would shorten the tube on the carburetor
What do u think about dimpling port0ing? Intake? Exsaust ? Just like a Golf ball i did it to my race 2 stroke motor thinking it wqill helo admizing my oil gas mix what do u think?
Dimpling can help with turbulence, making your fuel more evenly distributed/mixed in the air
I have to do some testing with dimpling in various places.
QUESTION::
Does more blow down give more torc or top end. Does less blow down give more torc or top end. There is no videos out there saying what more or less blow down does
I've seen a few youtube vids on how a 2 stoke expansion chamber work, none of them give the full story!
The actual way that they work is that when the port is uncovered a positive pressure wave travels down the pipe but when it reaches the diffuser section of the pipe due to a law of acoustics some of the wave is reflected back up the pipe with a negative sign (in other words a partial vacuum). This vacuum actually helps pull fresh charge up from the crankcase above the piston and even out into the exhaust). Not all of the initial wave was reflected back, some remains as a positive wave and travels along the pipe until it hits the baffle cone, it is then reflected back with the same positive sign, this wave pushes the fresh charge that was 'stored' in the exhaust back into the cylinder. Simples!
The acoustic law is basically that a pressure wave (positive or negative) is reflected back as a wave of the opposite sign when it reaches the end of an open pipe. The diffuser is a 'sort of open pipe', not fully open. This is why the diffuser is important in an expansion chamber. The law also states that a pressure wave will be reflected with the same sign when it reaches the closed end of a pipe. The baffle cone is a cone and not a flat plate with a bleed hole in it in order to try to increase the RPM range that the pipe will stay in tune. (The diffuser cone(s) can be tuned in the same way. Steep baffles cone(s) mean that the wave amplitudes are high but the RPM range that the pipe will work is very narrow.
+Sidecarbod well explained!
That is true and I've just done a video yesterday on it, first in a series of them.
What is described here does actually occur, however it is not the basis for tuning calculation.
The resonant effective described here is a secondary effect that can benefit or work against, and is more a matter of being fortuitous enough to have a pipe that ends up benefiting from resonance, and not the later.
If you happen to have a design and timing that results in a favorable resonant effect, its your lucky day, if the opposite occurs, not so lucky.
+AuMechanic Is your video up yet?
Yes it is now, posted last night.
First one is just the basics of what occurs, next ones Ill get into the details of each part of it as well as the resonance issues.
+AuMechanic 👍Great stuff, already watched it!
I had my cylinder head ported "sport port" do I have to upjet?
Yes
Can you tune the expansion chamber to gain more effect on lower revs at the cost of performance on the high end of the power spectrum?
Yes
@@2STROKESTUFFING how
Years ago I saw a König racing outboard engine with tuned pipes that tromboned longer and shorter with the throttle position. I tried to Google that now but found zip. Maybe this was a local experiment. I remember there were a whole bank of pipes that moved. The engine was on the small hydroplanes where the pilot lay down. I loved the racing fuel they used back then.
@@christopherknee5756 that would definitely be neat to see.
Are performance crankshafts worth it? Someone told me that performance crankshafts are as strong as oem crankshaft. How much can oem crankshaft take before breaking?
+zozias101 They're only needed if the stock crank can't handle an increase in rpm or power, or if you're after more/less crankcase volume some of them might help with that. OEM often exceed the so called performance cranks in quality.
So are you say you should or shouldn't raise the exhaust port
So basically, if i increase the exhaust port, it would be best if i also design a new pipe to match the port?
bingo
If I extend the exhaust timing to be higher... (184deg to 190deg) what effect should it have on my carb jetting? Should it be richer? And which jets? All of them?
Richer
But not much richer
So i have a small 2 stroke.
I just measured the exhaust port duration and it is a measly 160 degrees.
Should i CuT dAt ShiET?
seriously though, i want the engine to rev higher, its a single speed transmission and i want more top end.
did you try to cut that shit? if so, what happend?
@@eirikrcman1511 not much, i did it several times, im at 180 now.
Its more about port angles and size it seems. Unless they were the bottleneck all along
I want to buy a new Cylinder for my 2 stroke bike. Some have exhaust boosters and some dont. What are exhaust bosters?
+Barkev shadian Auxiliary exhaust ports add area above the transfers - a good thing!
2STROKE STUFFING Thanks buddy! Nice channel BTW! Keep it up!
+Barkev shadian 👍Thanks!
I have a cheap chinese cylinder kit on a cpi sm 50 (Taiwanese Minarelli am6 copy) I didn't run the kit before rebuilding the bike but the kit had a silly amount of poorly cast, rough material around the exhaust port so in chamfering it I was raising the exhaust port also. in the upper RPM's itll scream away, has a very narrow powerband and not much power in the lower rpms so the engine has to be worked all the time which makes town riding a chore. its almost like a yamaha dt125 with the powervalve pegged open but alot worse since the little 70cc has less power than a 125
under 100cc low end power and high max power dont go well together at all. maybe you could make it better with a different pipe
If the pipe pulse (a sound wave) is released earlier (due to a raised ex port), than it has to come back to the piston earlier also, (not later), since the sound wave is a fairly stable speed, (depending on pipe temps). It's a good point that I had not put that much thought into though. But "your" second pulse (off the piston, which I have never seen before) has to be diminished in strength quite a bit. But that would not matter. Once the port opens again, (the big boom),--that little pulse is going nowhere. Sorry man.
Port wide 1/2 mm up clean transforports new case bearings seal retainers these bicycle engine can get to 15,000 rpm now they have 92cc motorbike engines 52mm piston
But is it good idea if my engine hasn't got expansion chamber? Thanks.
+Jacek Gwiazdowski Without an expansion chamber you won't produce much power no matter what you do. Well, maybe with a turbocharger/supercharger.
Ok thanks again!
This vid only explains half of what an expansion chamber does, the positive pressure wave that travels down the pipe is partially reflected by the defuser part of the chamber (the diverging cone part), it is reflected as a negative wave, in other words as a partial vacuum. When this vacuum reaches the exhaust port it helps pull fresh charge up from the crankcase via the transfer ports, it actually pulls fresh charge into the exhaust pipe. This fresh charge is rammed back into the cylinder by a positive pressure wave just before the exhaust port closes.
When i port my yamaha jog 50cc cylinder i notice that Higher exhaust port gives very very much power put makes it lot more rpm but with giannelli exhaust,190° exhaust port and 19mm carb i get 96km/h
Por favor subtitula tus videos al español! gracias!!
Is it 190 degree is suitable port timing duration for all 2 stroke bike ?
Generally, but more is usually needed to get sufficient blowdown time area for max power.
@@2STROKESTUFFING oww .. thanks braah . You awesome . I follow all of your vedio and now , i know more about porting and the other stuff
So raise the ex port, lower the compression you gain the 17600 rpm?
+Knolto 125Rider With enough blowdown area, yes.
2STROKE STUFFING so that your ex had an extremely smal pipe, then have you cut edge on piston top instead cut the ex port, at least open and closed duration wil be same degree
Knolto 125Rider ramping the piston still changes the timing
tip top top tip : the hotter the exhaust pipe/gas is the faster the sonic pulse travels
wrap or ceramic coating helps with this
how am i'm gonna get this to work on my outboard engine hmm i don't know yet :) but something has to happen
Tell us more about time area and blow down :D
+pascal marciano I'll make a video!
Okayy lex, drink more rum for more sum HAHAH!!
In the book 2stroke tuning by hayes Its a good book
Gr marvin
4 stroke to by hayes book
Sometimes i feel like i'm a high exhaust port 😂
The biggest performance killer when raising the exhaust is loss of compression. Keep that in check and you probably won’t notice much difference between a couple degrees.
And yove just made more blowdown
2 strokes like lower compression anyways
@@xfdfff2620 no they don't.
@@CJSaws you can just see here in this video at the end, stock head made little more power than high compression one, and vhm head with lower compression insert made more than one with high comp
ua-cam.com/video/SF7pDtT13XM/v-deo.html
This can also be seen in 250 2 strokes
@@xfdfff2620 too much compression is a different story. There is a sweet spot and it's only lower compression if your comparing it to a motor with too much compression.
So many factors not addressed. Tune exhaust design, carburetor tune, boost ports, reed valve,piston port, rotary valve compression, ignition ignition
I knew about the first pulse but not the second one is this why the power-valve works well it it give the flexible power band.
Also Why does EVERYTHING in your workshop not go rusty like mine did with a propane heater in there.
+Graham Dawes Kinda, power valves lower exhaust timing, but mostly the just screw up the pulse action altogether. This is a good thing outside of the powerband when the pipe is working against you.
+Graham Dawes Not sure why stuff dont rust, I keep a small oven on all winter tho, too keep from going below 0°C
the problem with rust:
the heater does heat the air relatively quickly. Warm air can hold more water and will do so, picking up moisture mainly on the ground, on outside walls and especially in outside corners which are the coldest spots in a garage or workshop or outhouse ;-)
The warm and moisture filled air then gets stirred around by the heaters jet EVERYWHERE and cools down around all cold objects and thus pulls down the ability to hold humidity, which leads to condensing. Small droplets of water get deposited on all objects, thus you see rusting on EVERYTHING!
A wood burning oven would not have this effect, because the air doesn't not moved that much and the oven gives off most of it's heat in form of infrared radiation - objects get heated directly (stand around a corner, if you can't see the oven, the oven won't heat you! Terrible in small compartmentalized apartments). The wood burning oven gives off only a smaller portion of it's energy by heating the air (convection).
Matters with resonance is that a large numbers of moped just can't use it due to configuration the moves the engine ...
Exhaust that lift up with engine are bit fragile on tightened points,
If you specifically could "find" them, most of times not allowed anymore on roads,
And other point is to built parallelogramme balance system onto the moped, ...
Which is not either allowed on roads ...
Resonance cannot efficiently be used on exhaust with ajustable inclination the move the engine .
So, hight exhaust without proper resonance that reduce the frequency bitrate usable is not a solution on most of case .
Better look for exhaust port in three pieces two barrels and two smalls laterals ones .
You will have a way more longlasting rings ...
Endurance the engine sometimes has to be considered ...
Once theorical power cannot runs for miles, how get a sense the work done ?
I much prefer to widen more than raise.
+Dragon800 Smart!
one can only go 'so' big before running into problems with shortcircuiting transfers with exhaust through piston wrist pin.
correct. you need at least 5mm of space between the edge of the port and the cut out on the piston
And by that, one sometimes has to rise exhaust to get desired flow for rpm´s reached for.
yes i realize that. I almost always raise the exhaust some but i think a wide more rectangular port with big auxiliary ports is better than a super high port with no low end performance.
Hey bro do you work on engines? If it were to ship you mine. Its brand new just want to make it max out on rpm.its for a scooter project.
So a higher exhaust port is better?
I want to increase performance of my Yamaha Dt125 ypvs so I want to know how can i change my ports...
leave the ports, raise the compression.
@@aeroflopper that's one of the smaller DT models Yamaha made. Seems counter productive to simply not buy the larger model bike. I love my dt175
I get the theory but what happens with engines that do not have a tunned pipe, say a chainsaw motor has a small box silencer, do the pulses still return to the engine with this design?
+Guy Osgerby They do, but as that type of exhaust system usually is very short, the pulses just bounce back and forth a bunch of times each cycle and when the exhaust port is about to close again they're so weak they're almost gone.
fantastic info, cheers. As a video idea can you talk about upper circlip positioning on both sides of the wrist pin? recently i had a circlip wiggle its way loose on a blata ultima minibike, it completely ruined the piston and cylinder as it chewed it up. I've read an opinion they should be positioned either at the 6 or 12 o clock position, how much truth is in this? fantastic channel btw!
+Guy Osgerby Thanks! Too bad about that cylinder! I've always oriented the circlip gap like that too, 6 o clock, not quite sure why that's best. Maybe to avoid the clip "compressing" under piston acceleration. My only real tip concerning circlips is to use the type without any form of "ears". Those "ears" has a bad habit of breaking off.
you hit the nail on the head there, the ones that gave way were the circlips with ears, on the replacement piston and cylinder combo the circlips were a clean cut straight type, really appreciate the reply. fab source of info. cheers
shorten the pipe was my first idea.
i se the wawe a difrent way. i se it like a pressior wave and controll it with the last pipe before the silanser. the pressior wave has to resunance and have like a little pause ca 10 or 12 cm the port so you get a under presior at the port and a high pressior in the rest of the mufler . the higer the revs the more presior and ther is ver i detirmet the Ø of the last pipe and controll the pause to get max back presior and max wacoom at the port and newer loos all the presior in the mufler. ewrything you push back in the cylinder is free horses.
Widen the port is power.... make it higher the rpm goes up.. u need a balance between the two....
Also doesn't the raised exhaust port lower compression
Yup
You were supposed to counter act this with milling the head.
Not exaust port, but injection port at high pressure making a sort of supercharging, you could inject a little amount of fuel and NOS mixed with special injectors that already exist ( the injector wich inject fuel and NOS mixed), do you undetstand what I said. They Are NOT exaust port puted higher, they are actually injection ports above the exaust line.
I believe you are talking about what is know as back pressure?? Some back pressure is needed to stop fresh air and gas from escaping out the exhaust while the cylinder is taking in new mixture or CHARGING. To much BACK PRESSURE is NOT good OR to little. Your type of exhaust comes into play here does it not??
Walter kaaden!
Higher exhaust for my dont ist the good idea and less if you don't have a gearbox
In the age of no internet and UA-cam, I've learnt this with trial and error with my little 110cc bike and ruined many cylinder blocks along the way. I learnt that high is always better, but the problem is to find a matching sport exhaust to match it. None of the ones/aftermarket sold in the store would match it but found one old and beat up exhaust matching it perfectly. I did not know it had to do with resonance but now I understand why it's a pain to look for a matching exhaust. It easily hit 180kmh in a few seconds. I used it for drag
so basicaly the earlyer your port opens the longer the pipe needs to be,
Just going to hopefully add to the conversation:
You can make hp but have the power band so narrow that in real life, the engine falls below the band when shifting. The bike will be very sluggish and won't win any races.
+Big-J True
2STROKE STUFFING Can you list your PayPal address direct under the PayPal link in the description? The link doesn't open the app on my phone.
+Big-J degnestransport@gmail.com I'll put a "paypal.me link" too in the description from now on, rather not put my private mail there cause spam...
2STROKE STUFFING Done!
+Big-J Thanks man!
I just realized iam stupid as shit😅 didn’t understood nothing man... please talk for dummies 😂
Longer exaust timing, likes longer exaust systems...
so you are saying that the longer the port duration the longer my pipe needs to be? well finding the right pipe size is simple but does having a longer(higher) port duration increase power in the high rpm range?
sorry for the newbie question, im just finding ways to squeeze all the power from my 50cc moped
@@redsoldier17 on a piston port twin longer pipe tailcone/timing worked out ok for me but lost in lower rev range. 2 stroke tuning is compromises.
If you're really interested into the how & why of tuning small 2 stroke tuning checkout: AuMechanic youtube chanel
If youre street riding a 50, big bore kit may be best bang for buck after a pipe & carb...
Size doesnt matter but resonance. Thats not what she said!
Too many things I don't agree with to get into. To start with the pulse speeds are not the same. Not even close. The temp of the exhaust gas when the port opens is higher. And much hotter.
Anyway how about doing a video with insanely low Ex port durations and fun things you can do with them.
Chambers work better with high exhaust port duration than they do with low ex port durations.
You should make a 4StrokeStuffing channel !!
Port High = Half stroke?
Stroke 50 mm/ port High 25mm.....
half stroke means 180° of crankshaft rotation
The timing is not linear to the stroke... its a sinus function of it... near the TDC an BDC youll have to turn much more degrees to get the same "pistontravel" as 90° between the DCs...
If we are talking about the exhaust port, half the stroke as port height means 180° of crankshaft rotation.
+Peter Ipsen It's a bit more complicated than that. Google "piston travel vs crank rotation"
Well well well .... i do know that half stroke is 180 degre :-) but, it is not nessesary to make the exhaust port higher than 1/2 off the stroke?
Ifyou worked on 4strokes you wouldn't be spending so much *money*
+fishsticks But I like 2 strokes better...