Secrets of two stroke ignitions, tuning and function

[@bongzonthebeat]

I wish teachers in school could teach like you do, the way you present your teaching methods is awesome, never got lost once and could watch and listen and understand the whole time

[@arthurmuller2965]

Wish school learned us to tune 2stroke

[@2stroke69]

real.@@arthurmuller2965

[@1crazypj]

@@arthurmuller2965 I was teaching at MMI 2000~2011.5, we were not allowed to vary from lesson plan (which has to be approved in all states where students are likely to come from) I was often 'in trouble' (managers office) for going over and above with students who had more interest in things particularly when 'other instructors students couldn't get the same level of information. I was 'laid off' as an easy way to get rid of me, someone 20 years younger was moved into my position which would be illegal in most states and countries (being made redundant means job is no longer available, not, 'we want someone more compliant who will do as they are told) I had refused to sign off work for students who admitted they had been cheating so should have failed a three week session, management wanted them to pass (when MMI had become 'more money Institute')

[@frank3RV4]

Wow! This is the finest explanation that I have seen about how two stroke engines work. I have seen the timing curves of two stroke engines and wondered why they are so different from four stroke engines. Derek, you are very articulate and a great teacher. Thank you for helping me understand better how two stroke engines work.

[@ajr.1272]

Wow. You gave a whole new meaning to the term "open a can of worms"! Appreciate how, in very layman's terms, you showed just how complex performance 2 stroke engines can be. Best regards from Brazil.

[@Randy_Cox]

Throwing down some great knowledge dude. 👍 Pipes are everything on a 2 stroke and see how you toy with the ignition to compliment the pipe is so cool.

[@19QuickNick93]

The best video for explanation of 2stroke I have seen so far!

[@KrustyKlown]

been messing with 2 stroke racing engines for 50+ years, and I learned a bit !!

[@mrw1054]

Back in the mid 90`s we were running total loss MSD programable ignitions in our full mod Yamaha Super Jets. You could change the ignition curve every 200RPM with with different "chips" that you would plug into the system. It really was a game changer back then:)

[@HPRaceDevelopment]

@@mrw1054 yeah things a good bit farther now but a proper ignition amount always helps

[@HPRaceDevelopment]

@@mrw1054 I have an old 750 kawi stand up, and got a programmable cdi for it, holy hell way better! Lucked into getting it from a guy who had a good map and testing already

[@mrw1054]

@@HPRaceDevelopment I had all the standups:) I had a kawi 750 engine full mod ported.every port raised 5 mm! I put that engine in Kawasaki 440 hull with a straight 19 pitch Skatt track prop used to do like 64 miles an hour! I'm a Harry Klemm (group K) fan from way back I know you know who that is! And you have a great channel Sir!

[@pokebass1]

Coming from a background of studying drag racing for years before getting into dirt bikes, your talk about regarding ignition reminds me of what guys running pro stock would do back in the 1970s. Back when a dual point distributor was the mainstay of ignition devices, guys would split the two sets of points and run the trailing set at high rpm to regard the timing for more power. I believe guys running ego and fancy ignition maps nowadays do the same thing with their timing. That, coupled with stepped header tubes makes a good difference. The stepped header tube is meant to produce a high velocity in the smaller tube section to get the air/fuel mixture moving out of the combustion chamber and enhance the effects of scavenging. The larger tube section is meant to give the slower, colder air more room to move through.

[@cnosigamer]

You can't imagine how grateful I'm for this video!!

[@craighills2382]

Your explaining qualities are well going to waist , you explain with ease of understanding Thank You

[@tinolino58]

Awesome, for my mopeds with 60ccm I programmed my CDI in steps. Below resonance at 30 degrees, at resonance about 22 and at high rpm around 14-17degrees. After this video I will do more testing with a new approach.

[@HPRaceDevelopment]

your set up is taught/told by many very good tuners and builders as a rule of thumb - but that rule of thumb came about from testing like ours…over many years ending up in similar results as yours. Hope it can find more improvements

[@stevenbusk539]

Excellent video and great explanation of the function of the ignition map on a two stroke, for those of us who don't know anything about how it works. I have an 1986 Kawasaki 125, and it was tuned with a programmable ignition, and as you said it gained on the front of the curve, the peak was higher and it held onto the power on the back of the curve more too.

[@andyddog2]

Very nice video! Very clear and a great help to all of us learning, Thanks

[@philipsmith6152]

Absolutely brilliant, and dispels a lot of B.S in the 2t industry about how to get more power 👍

[@mattwindell1638]

Awesome video. I knew pipe shape was crucial to where and how a two stroke makes power. I didn’t know the exhaust temperature had such a big influence. Will you do something similar for four strokes?

[@260bossute]

Not a huge bike fan, but I do enjoy riding them and have to say, dude you clearly know your stuff. When you started to describe the exhaust pulse wave, the aeronautical engineer in me had flashbacks to aerodynamic theory at university. Subscribed and liked! I hope your channel picks up, you totally deserve it.

[@Mineratron]

Excellent video, thank you. Just about to take my first dive into playing with my TSP ERM (KTM 23 300SX). To figure out why I like the first part of the original green map better… theirs is better further up the range though. Feels like the soft map on the older 300SXS CDI, revs out better than stock green KTM. Feels like it’s been tuned for dry hard pack MX. Needs a bit more on initial tap for the desert. Different ball game from Lectron and PV springs… I’m away to watch the 2T FI video. 🤓🤙

[@tiagobarbosa1489]

I'm a mechanical engineer and teach classes on welding and pressure vessel design. But boy, do I envy your skills.

[@mmholling87]

Outstanding content!

[@Roostfactor1]

Super interested in why the ignition spikes back up on the back end for motocross applications and not for Karts or road bikes? Thanks for the content, very interesting! Want to dyno my 2023 300XC?

[@HPRaceDevelopment]

sure

[@Roostfactor1]

@HP Race Development I'm serious so hope I didn't come off the wrong way. I'll call you tomorrow.

[@HPRaceDevelopment]

@@Roostfactor1 no prob. Yeah we can get it on the dyno, I had a 300sx already haven't posted it yet. Be good to see the xc

[@joeylacroix9795]

​@@HPRaceDevelopment how would you suggest finding your best timing without a dyno?

[@HPRaceDevelopment]

@@joeylacroix9795 hard to do...feel it out and be very knowledgeable on what detonation looks and sounds like

[@beverywhereyouare]

WOW !!! You’re brilliant man !! My girl is getting a KTM 85 soon … Id like to send it your way :o)

[@pricebrosracing8418]

Great information! Very well explained and easy to understand. Great job man!

[@charlesharris4280]

Very good information, I enjoy it very much, how much are your DC I for a yz 85 2019

[@rfair123]

Synergy......... Excellent presentation and info......

[@m3hsid10]

Excellent lesson! Your understanding is impressive! Mine?....Not so much....lol!

[@ronbradshaw7404]

I used to know lots about 2 stroke perf. but you, are Kevin Cameron grade!!!

[@mikebrown41182]

Thanks for this Derek, it’s cool to get more indepth into the ignition. But do GET produce ignition boxes for the older bikes like the kx, rm, cr? Or you simply code them to work in conjuction.

[@HPRaceDevelopment]

hpi makes for those

[@The_Snowbike_Channel]

Very informative and your comment regarding “finding a needle in the haystack” is spot on. Over the past two years I have made various hardware changes to a BRC 500 build. The trickiest component was trying to use a programmable PowerCDI ignition paired with a SC2 carb with TPS. I have the bike setup very well now for snowbiking but beginning to wonder if the SC2 carb is too much of a compromise for simplicity and I am missing out on top end power. The added jetting for higher rev would be nice. I suspect the SC2 “robs Peter to pay Paul” when you make a decision where to leave settings. I have a Keihin with STIC I am going to test next. I suspect I will like this carb better but at the cost of complexity and additional tuning effort between rides as conditions change.

[@HPRaceDevelopment]

Spot on

[@BARacing]

top explanation :) videos like these are missing on KZbin... I'm looking for the origin curve of a recent cross bike like yz 85 2018 Do you know where I can find some ideas?

[@HPRaceDevelopment]

Use a timing light, camera and rpm guage in the same shot...plot it out manually.

[@ariane11970]

Absolutely brilliant channel !! 👌 Thanks for your perfect explanations. 😉

[@1crazypj]

I wish this stuff had been available years ago when I was racing. In the 80's, if it kept running and you could finish, things were good. 😁 Electronic ignition was common but reliable ignition was rare on any MX bike and a bit iffy on some road bikes. I've been totally away from motorcycles last 12 years or so, the developments are very interesting but it's doubtful I'll ever use any of them. Two stroke pipe tuning has been known about since 1960's but few people understand it even today. I'm a bit surprised at the 'renewed' interest and availability of two stroke race bikes as in early 2000's it was almost completely gone and only factory teams had any new technology. BTW, Suzuki used power jets on GSX-R four strokes late 90's or early 2000's, (I forget stuff).

[@inevespace]

You didn't mentioned this ignition timing increase for MX bikes in other videos yet, but I'm curious about the purpose. Is it for some kind of rev limiting in the air during jumps?

[@ncopp4358]

No rev limiters on two strokes. 4 strokes need a rev limiter to prevent valve float and two strokes dont have valves. hence why there is no need for a rev limiter.

[@inevespace]

@@ncopp4358 you didn't watch the video?

[@carlmuoio216]

Love it and thanks for education

[@microsoft790]

What an amazing video i would love to be an apprentice under you

[@Copozeras]

Hi, where can I find info on that why is good for motocross engines to advance the timing back after peak?

[@1176hambone]

Great vid!

[@chriscouch8802]

Nailed it on the head for the torque curve

[@chriscouch8802]

I also preached this to many stock class racers parents on the ignition timing and modifications that actually alter stock machines

[@cranksby3004]

Very good explanation.👍

[@z-tech-extrem]

Man that was awsome information for me. Thanks a lot!!!!

[@dwanemitchell9653]

Awesome video

[@halvorsonmx]

What an awesome video! Thanks!

[@Keemo577]

I like this. Adding it to my dirtbike list for future reference. The only thing I wonder about is how towards the end, you say "what we feel like is more horsepower". Do you provide dyno graphs? Not trying to knock you guys, just wondering, ya know?

[@HPRaceDevelopment]

We have a entire video provided about ignition dyno runs as well as a feature series on a kx112 mods. I try to be modest and polite - my company doesn't sell something if it doesn't make power.

[@Keemo577]

Thanks for the reply and keep up the vids. You're good at this.

[@jowensedycastillo3531]

What’s your opinion on the hpi ignition for a 2002 Cr250 with no porting (a stock engine) just adding a higher compression head and 100 octane fuel?, or a JD ignition?

[@chrisbracken7889]

Love your videos dude

[@elobenc2760]

I'm waiting for similiar video about 4strokes!

[@reh9999]

Great content

[@AutoBeta2T]

Thanks Derek - a great video. Thanks for posting.

[@AbBc-w4q]

I put a Zeeltronic programmable ignition on my RD400 and am getting ready to start programming in a curve. Wish me luck.

[@copisetic1104]

Ceramic coat the outside of the pipe, it will retain more heat in the pipe. It makes the pipe work better over a wider RPM range.

[@HPRaceDevelopment]

yeah that really hurts low end

[@fernandomotoholic1417]

would you please explain the difference between motocross engines and roadrace and kart engines requirements on the so-called overrev range that you said you wouldn´t get into in this video or point me in the right direction where I might learn about this details. thank you very much

[@HPRaceDevelopment]

Road race and kart engine don't need to rev under zero load. As such they don't require ignition mapping to function 1500 rpm past peak hp, a motocross engine needs the map developed and in a very special way in order to rev 5000-7000 rpm past peak hp when under no load.

[@jpmorgen5726]

I need a programmable cdi for my vintage 125 Elsinore, any suggested sources?

[@matthewfredrickmfkrz1934]

For efi would referencing the divergence convergence intermittentary section for fuel map be the keystone?

[@iikavanaghii]

Great video. Next is to show us the tool sets used to advance or retard the timing, and the testing around it and also the process of porting, how different shaped pipes effect what, how the pipe and silencer combinations work out for different power delivery / curves

[@HPRaceDevelopment]

We have published porting and cdi videos

[@iikavanaghii]

@@HPRaceDevelopment appreciate the reply, I'll certainly seek those video's out to watch. Watched a number of your video's now, all really good, educating stuff; perhaps my comment was premature :)

[@baby-sharkgto4902]

This was a fantastic video, if would critique anything would say perhaps you could have removed the powerband and shimmed it for more power

[@HPRaceDevelopment]

agreed

[@joelatkinson2080]

Great video!!!

[@Fast-twitch03]

I recently bought a used yz125 and it came with a get ecu on it and now I’m a little bit scared to do some modifications because I don’t know if the tune will negatively effect anything. Should this be something to worry about?

[@HPRaceDevelopment]

While this sounds self promotional - whoever you use for mods should address that for you.

[@keithpeterson6108]

He's trying to scare you from doing any mods & contacting him for work. You can absolutely pick up good gains over a stocker, everywhere in the powerband through the typical mods. Optimizing the ignition is just a nice thing to do to get the last little bit out of it. So don't worry about doing other (sensible) mods. HP likes to paint a picture that he's the only place where you're gonna get your engine modded correctly & get the most power. He's an average builder with average gains. Not saying he does bad work, just saying he plays word games to strum up work. To me, that's shady.

[@curtis026]

Has there ever been a good explanation as to why the new 2 stroke KTM EFI system doesn’t have a sensor somewhere inside the exhaust? There has to be a good reason as to why the aftermarket hasn’t cracked this code yet. Is it because the factory stuff is just impossible to crack, or is it just not worth trying based on the system as a whole?

[@HPRaceDevelopment]

We discuss this in our efi 125 video

[@HPRaceDevelopment]

What sensor to accomplish what? An 02 sensor - doesnt' read accurately on a 2t for a host of reasons - and is slow to respond for a host of reasons. And egt? Useful for tuning under steady constant loads - such as road racing or karting - not useful for MX.

[@emexduzentos]

A two stroke pipe takes temperature into consideration when being calculated/designed and let's not forget squish effect.Yeah, we're reaching black art. Cool video.

[@HPRaceDevelopment]

It does, but you can still influence that temp to broaden it's power range. And yes, the head effects temp -as well as chamber shape and squish details.

[@adrianhadipermana6109]

My bike can lift the front when it's cold, but doesn't when it's on working temperature, did I have to change the jetting?

[@my-max-media7621]

Rase the needle a clip.

[@garyhoward4064]

Do you have a video showing how to actually program your CDI. Guess it’s something similar to programming ÉCU on 4 stroke? I have a 1972 Kawasaki 750 (H2) 2 stroke and since I have the expansion chambers I completely lost low rev power..

[@HPRaceDevelopment]

Most cdi can not be programmed - you have to buy one that can be and make it work for your application

[@garyhoward4064]

@@HPRaceDevelopment if you have such device I’m a buyer

[@HPRaceDevelopment]

look into zeeltronic@@garyhoward4064

[@A_A_Ron78]

Let's say we have a KTM 85 with a stock bore FMF pipe, which we added, (professionally) on a 105 kit, do we wanna now wanna run a big bore FMF pipe? I've watched a few videos, & none were convincing enough that said it made sense.

[@HPRaceDevelopment]

we happen to have published the results of that test in our budget supermini build

[@metallicobject1831]

🤯Thank you.

[@speedtoad6167]

The Vortex Ignition in my YZ250 gave it a touch more power but the biggest difference was it was easier to ride.

[@HPRaceDevelopment]

It likely lost power which feels easier...just our testing experience. The yz happens to have a really optimized curve stock

[@RandomUsername81]

Have you ever dabbled with Twin plugged single cylinder bikes? I think the KTM 495 was twin plug

[@HPRaceDevelopment]

no

[@karumasPT]

Hi bro, how can i get the 85 ktm cdi xg4 ignition curve and specs? i have a programable cdi but no base map for the bike. Thank you

[@HPRaceDevelopment]

Develop it!

[@karumasPT]

@@HPRaceDevelopment Yes but if i have the original one, it will be easyer... For pe. idle advance etc

[@HPRaceDevelopment]

@@karumasPT I work hard to develop and acquire our maps. Sorry but not something I hand out

[@karumasPT]

@@HPRaceDevelopment sorry for the that, but i dont have a oem cdi to "take" and "mesure" the oem cdi curve, so im "blind" in relation of that, and im not a "professional" i just make this to my own, like a hobby, thank you

[@sesker15]

Would a stock motor 2stroke motor benefit from a GET cdi?

[@HPRaceDevelopment]

Depends on which bike, and a few other vairables. But in most bikes stock is great. You can change the "feel" of power with a cdi on any bike (usually by taking power away a little)

[@davidrose8612]

If 2 stroke spark curves are generally similar, as illustrated in the top graph on your whiteboard, can I graft a 2023 YZ250 ignition onto my 1986 Honda CR500? I am finding that the various aftermarket ignition components are poor quality and short-lived. I would like to install Japanese components if possible.

[@HPRaceDevelopment]

We generally dont have any reliability issues on the boxes we use… Oem level quality and used by some oems… If you can replicate the crank trigger location, sort out wiring, and the build combo is about identical in pipe, outlet of pipe, power, porting arranment, and head, then yes you can swap to a different oem cdi

[@davidrose8612]

Understood. Is it safe to assume that apart from a significantly retarded spark needed for starting and maybe idling, the spark on a mid-1980s CR500 remains constant (25 btdc, for example) through its power band and up to the point where power begins to drop off? Your graph seems to indicate this is the case. @@HPRaceDevelopment

[@HPRaceDevelopment]

@@davidrose8612 No, it wont be constant

[@Adrenalinspunk]

My question is could you build and ignition curve using egts only. 🤔🤔

[@HPRaceDevelopment]

power is what we chase - so no. highest or “best” egt at all rpms wouldnt result in best power everywhere. but egt is a great tool on two strokes

[@Adrenalinspunk]

@@HPRaceDevelopment so how could I implement the egts to help with a timing curve as the engine I'd like to build a timing curve on dosent have wheels and can't be done on a dyno. Cheers

[@stackedpennies4377]

Getting a kx112 for my 13yr son. I’d pay for a 1-2hr lesson on an elementary lesson of 2 stroke bike care, tuning, fuel mix, etc. I’m in NB. Let me know if you’re interested

[@HPRaceDevelopment]

Maybe we will do a video series on this, its been on the plan book but I havent done them

[@bernardvanderveen7656]

Can you do same on a 250 f

[@HPRaceDevelopment]

Which type of video

[@yoandragmotocross371]

Can anybody tell me where i can find à similar cdi for an 2007 kx 125? Really need it!

[@HPRaceDevelopment]

u can email me i have a possible source

[@adamhollins]

Which 250 2stroke makes the most power with all these optimisations?

[@HPRaceDevelopment]

Currently a ktm/husk/gas gas are the best of mx based engines

[@Robertas_Grigas]

Great video tho you should really clarify what a "modern 2-stroke" is cuz even today you can buy a brand new Jawa 350 2t

[@FrancoisLaperriere-ry4ss]

For an exemple Witch cdi box is better after porting my ktm 200 sx 2003 ,crankcase porting and polish,cylinder open port,carb open to 39 mm ,and fmf exhaust.Thanks to recommand me ,and if you got stock or mod ktm 200sx dyno graph?

[@1000draggsxr]

When you were mentioning air fuel What would be the optimal air fuel ratio for a 2 stroke seeking over rev

[@HPRaceDevelopment]

whichever one runs the best for that combo....

[@KrustyQuad]

question...Then how is it that significant power can be gained on say a Yamaha blaster with just porting the cylinder without making any other changes?

[@KrustyKlown]

WHY isn't the better solution for max peak power, a fixed ignition & jetting, but with an adjustable pipe (moveable baffle cone) ??? Adjusting timing & mixture to change the acoustic length of the pipe, comes at the expense of peak power.

[@HPRaceDevelopment]

No it doesnt - hence the fact that after 100 years of r&d from very bright minds all over the world its done not your way. Secondly your incredible flawed in logic. The engine is designed for max power with pipe, port, and ignition - then the “tricks” are done to widen that power. not take away from it.

[@KrustyKlown]

@@HPRaceDevelopment ?? But you are doing tricks to change pipe temp that reduce thermal efficiency (loss of potential power). It’s the acoustic pipe length ya want to change. They do it on racing karts (road racing), cause it makes power.

[@HPRaceDevelopment]

@@KrustyKlown You dont understand or dont listen at peak power both the pipe and the ignition are at optimum config and value. the powervalve - is one trick to lengthen tuned length, more ignition is another and a powerjet is another then at peak power the powervalve is open fully, the ignition is at ideal value, the pipe is at perfect tuned length for the port and temp and rpm then past peak power the powerjet turns off, the ignition retards, and we extend power. variable length pipes do not properly change all the pipe dimensions, dont seal well to create maximum pressure, are too slow to change length vs what rpm rate of change mx bikes see, and wont fit on an mx chassis at variable length - and even worse they work worse than a powervalve

[@sidecarbod1441]

Pipe temperature does have something to do with the ignition timing that the engine wants but is not the main reason that a 2 stroke timing retards as the revs rise. A company called Ricardo Engineering many years ago worked out that any piston engine built with reasonable dimensions (con-rod ratio, bore and stroke etc) will give peak torque at any given RPM when the peak cylinder pressure occurs at 14-20 degrees ATDC. Now one thing to remember is that it takes time for this pressure to build so the spark plug needs to fire the mixture sometime BEFORE TDC. Now there are TWO things that affect when you need to fire the spark plug, the obvious one is RPM, in simple terms the higher the RPM the earlier we need to fire the plug, this would lead you to conclude that that timing needs to advance as the RPM rises. BUT and it's a big BUT, the initial cylinder filling with fresh charge has a big affect on the ignition timing, this is known as the engines volumetric efficiency (VE), the higher the VE the higher the initial cylinder pressure will be and therefore the later we need to fire the plug. This is because the flame speed increases as the VE gets higher. Now 2 strokes have terrible VE when they are off the pipe and not in the powerband, but the VE can go over 100% when the engine is on the pipe (intake and exhaust are resonating correctly). So to sum up when the engine is getting nearer and nearer to the RPM when everything is 'in-tune' the less ignition advance that is needed, if the timing is not retarded the peak cylinder pressure will happen too early in the power stroke which at best will reduce the power output or worse will drive the engine into detonation. (The death of many a 2 stroke engine). A fully programable system would be setup to advance the timing at low RPM as the revs go up but it would need to retard the timing quickly as the engine gets into its powerband. The advance in timing after peak power RPM is also to do with the VE of the engine dropping after peak power RPM. A rise in RPM and a rise in VE actually want the opposite in terms of what they require in ignition timing, the rise in VE 'wins' the battle, the result is that the timing is retarded.

[@HPRaceDevelopment]

This is largely innacurate, sorry with a couple truths layed in but a very poor understanding of how a two stroke works. The ignition's primary influence is on pipe temperature. At lower off pipe RPM's the cylinder charge make up is extremely pure with a few exceptions depending on powervalve design. A powervalve is entirely focussed at influencing the pipe just like the ignition is. Because a two stroke has an extremely efficient combustion chamber compared to modern four strokes (who have to deal with valves and poor piston tops), combined with the fact that two strokes have a VE of often times 140-150 percent, combined with the fact a decent amount of the inlet charge gets heated by the outgoing exhaust charge - necessitates less igntion timing near peak torque, but to influence the pipe we want max allowable "off pipe" in early rpm range to "cool" the pipe to act longer - aka better for lower rpm. Since "off pipe" we have a VE well below the peak torque VE - we also can tolerate more advance before reaching the fuels limit. A well designed two troke often has peak cylinder pressure well before 12-14 degrees ATDC. We commonly see the best of the best around 6-8 ATDC. In a theoretical world we would want right at TDC. As we improve engine elements over time we march closer and closer to the theoretical ideals. 12-14 degrees was "ideal" a long long time ago as measured on the test engine of the test...but not ideal because it's "the right time ATDC". It's "what worked at that time". The ignition is "correct" for peak torque to the optimium burn time, cylinder pressure, and compression ratio, and "pipe heat" which really means the pipe is designed right such that it works perfectly when the ignition is idealized for the other variables. Then it retards to add pipe heat past peak torque to improve the pipes function and heat the pipe for improve function past peak torque. This is 2 strokes 101. Modern four strokes are similar but different, with minimum advance at peak torque, max advance at highest rpm, and between those two at lower than peak torque rpms when cyl pressure is lower and the fuel can tolerate it. Advancing the ignition is VERY similar to increasing compression ratio. After peak torque cylinder filling falls off, time to burn decreases, and charge purity decreases creating a slower burn vs a pure charge.

[@sidecarbod1441]

@@HPRaceDevelopment Your reply is largely nonsense with the odd 'cloud the issue' remark thrown in for good measure, the statement about wanting peak cylinder pressure at TDC is the real icing on the cake, you clearly have no clue about conrod angles etc. Frits Overmars as taught me about 2 strokes and how they operate, your statements and video are just hot air, jog on.

[@HPRaceDevelopment]

I know frits quite well. You can forward him this thread and pick his brain on my comments if you wish. I can give you his email if you need it. My guess is He will agree - ignition curves are designed to influence the pipe. An idealized OTTO cycle has instant burn speed, zero spark advance, and max pressure right at TDC. This allows maximum expansion ratio, minimal heat losses, minimal negative work, and maximum power. If you don't understand this - you have zero business lecturing someone who does. Two strokes utilize some of the "weaknesses" in real world usage of the OTTO cycle by recouping some of the energy lost by using that energy into the pipe design and then the pipe does additional work for us - much like a turbo does. A two stroke pipe and a turbo do similar things - extract usable energy from formerly wasted exhaust heat/energy. This energy can be used to pull more charge/stuff more charge in the case of a two stroke: or on a four stroke to pressurize the inlet charge.

[@sidecarbod1441]

@@HPRaceDevelopment Of course having peak cylinder pressure at TDC will give you the maximum expansion ratio but its no good having all that pressure if the conrod is directly in line with the bore, in other words if the conrod is vertical. You could stand an elephant on the piston but it still would not go down the bore, the conrod needs to have an angle relative to the crank so it can actually turn the crank. (The fact that the engine engine is spinning has nothing to do with it, you could take an engine and place the piston at TDC then pump compressed air into the head, if the engine is at EXACTLY TDC the engine would not spin, the piston would not go down the bore). In fact I have seen drawings of engines where the bore is offset relative to the crank so that the conrod has a better angle to create torque at the crank. If you can't understand this you have no right posting up youtube videos where you imply that you are an expert on 2 strokes. Oh I don't need Frits email address, I already have it. I'm not saying that pipe temperature is not important, of course it can be used to change the resonant frequency of the pipe but the VE of the engine has a massive bearing on when the ignition needs to fire the plug, its the same with 4 stroke engines, in the old days they used a vac advance system and many still do, many 2 strokes now do something similar, they monitor throttle position which will act as a guide to the VE, if the throttle is just cracked open the VE must be low because the engine is literally be 'throttled', it can hardly breathe, the timing will advance or at least won't retard, if the throttle is at WOT the VE will go up, the timing will be retarded by the ignitor box because the flame speed will go up. (No pipe temperature monitoring going on here!) Feel free to reply, if you do I'd like you to answer the following two questions, I'll make it easy for you and give you the answers! 1. Why do many 2 strokes now run with a TPS? (the answer is above) 2. Why generally when you increase the static compression ratio do you usually have to retard the ignition? (The right answer is because the initial cylinder pressure has gone up, i.e. the pressure in the cylinder just BEFORE the plug fires, the higher this pressure is the higher the flame speed is, this means that we need to retard the timing so that the PEAK cylinder pressure occurs when the conrod has the best angle to create torque. Same as increasing the VE of the engine, higher initial cylinder pressure, and that's what a working expansion chamber does, it increases the VE of the engine, flame speed goes up so the timing needs to be retarded)

[@noneofurbusiness-yk1mg]

@@sidecarbod1441 a lot of "mierenneuken" (ask frits overmars what that means, its dutch) about theoretical stuff...thats nice if you have 200 years to live and no finish line to cross within time. In the real world people do what this man is doing: dyno, adjust, dyno, adjust, and then get good results. No one ever won a race with theory. I myself don't care a bit about how things work, i look at the finish line and get there before the others do. Do yourself a favour, get on your bike and ride it. If you dont have a bike but only books, then start a youtube channel where you tell about your theory and how everyone is wrong. maybe you'll get some viewers, maybe not. untill then i'll just keep watching HPRacedevelopment videos.

[@cagr4249]

A good marketing-presentation. Only consequence is to run two-strokes with ECUs featuring fuel injection a.s.o.

[@HPRaceDevelopment]

@@cagr4249 what

[@brianpatterson5058]

If pipe temps are that critical why aren’t all 2 stroke exhaust double walled. And why don’t woods racers experience a big drop in power even momentarily after splashing through a puddle as nd finally why doesn’t anyone wrap pipes with the header insulation except the hillbilly guy on the edge of the pits.

[@HPRaceDevelopment]

@@brianpatterson5058 I dont think your grasping what im saying. Pipe gas temperature inside the pipe is what determines sound speed. The pipe wall temperature plays a small role in that compared to ignition, head, port, and fueling. Woods racers DO experience changes in running when splashing through water - if the scenario is right. But achieving a high pipe gas temp all the time is not desireable, and a low pipe gas temp all the time is not desire able. As explained in the video

[@dennismillus4581]

😆 🤣 😂

[@mikebrown41182]

Whats the reason for you being rude? Not the first time you posted something to disrespect HP.

[@petergehle4222]

Great video mate