Head design parameters and how they affect power output

[YamaZuki]

That's awesome info,And yah it will have stock internals 1st overbore,ported and eventualy a pipe when i find one.and this is for trail use.I want to double the hp of stock tho.Can i get there from a recut head ,porting, a pipe and propper jetting?Adding a base gasket to change port timing?If i have to i will get a carb eventualy,only 30mm tho.
Thanx so much for all u put into this passion we all share here

 

[best]

Excellent thread James! I didn't want to clutter it up while you were on a roll! STICKY! STICKY!

Joe, what is the squish velocity of those heads? What exhaust port timing were they designed for and operate at? What's the RPM ceiling for those combustion chambers?

While engineering things from the numerical is a good process, Joe has done it pragmatically, not theoretical. He started with a known performer, the DT200 chamber and a proven port map. From there he has played with each variable to see what they did to the power. Squish %, squish gap, chamber shape and chamber volume, to feel for where optimum is. It is a time honoured process that is often used to generate the numbers or see if the numbers jive with real world experience.

Like you mention, there is not one perfect head shape or volume, but the "50% 11 degree hemi tuned for squish gap and volume appropriate to the porting" will really please most folks, taking their 17hp Blaster over the 30hp threshhold.

If you want more, it will take much more fine tuning, not just in the theoretical, but in the practical testing to see if it works. The theory is often a good guide in which direction and how far to go.

Great work!

Steve Best

 

[joeak47]

Joe, what is the squish velocity of those heads? What exhaust port timing were they designed for and operate at? What's the RPM ceiling for those combustion chambers?

I need to get my degree wheel back from my buddy,and I'll see what I come up with. I'm curious myself. I know that without question that the Heads I've re-chambered WORK! And work VERY,VERY WELL! All without any detonation. However,I would like to know the squish velocity. I know that they (the heads) have definitely increased the over-rev considerably. I wish the blasters had a tachometer. I mean a "real time" tachometer with no delay. How are the DT200 tachs set up? Cable? or...electronic?

I just find it very easy to come up with a head design with a pencil,paper,and my brain,walk out to the lathe,and cut one in about 45 minutes,CC it,bolt it on,and TEST! Then...Take lots of notes and pictures for my two stroke note book. Then remove the head again and try something different.

So far I've been very successful.

 

[best]

<SOME SNIPPED> I wish the blasters had a tachometer. I mean a "real time" tachometer with no delay. How are the DT200 tachs set up? Cable? or...electronic?

The DT200 is cable operated off the top right side of the engine. Need the gear inside as well as the cable and tach.
The tach is very heavy too.
There is always the TTO and several other small battery operated tachs. Some do delay and I like a needle better than digital.
They work by a wrap of wire around the sparkplug wire.

The TTO temp gauge records maximums, I don't know if the tach does.

Trailtech TTO Tachometer Hour Meter for Paramotor and Other Small Engines | eBay

 

[dksix]

........making their 17hp Blaster over the 30hp threshhold.

Do you really think just rechambering the head can make that much more power? I'm going to do one soon and expect an increase but nothing like 70%+ more.

 

[joeak47]

Do you really think just rechambering the head can make that much more power? I'm going to do one soon and expect an increase but nothing like 70%+ more.

Coupled it with an "Aggresive Trail Port" and you will ...without question.

 

[scotj77]

with the mods in my sig i am guessing i am at about 100% power increase. if not that high it is really close

 

[Paulie B]

Whats really cool about all this is you can custom chamber a head that was never meant to work well like say a stock banshee head on a 10mil bottom end

 

[YamaZuki]

Like i said in my appologiy i id not know you weren't done, so just delete my posts as to not leave this awesome write up all screwed up by me.I had just woke up and thought it was a completed item,sue me

 

[sicivicdude]

Whats really cool about all this is you can custom chamber a head that was never meant to work well like say a stock banshee head on a 10mil bottom end

This thread is about the theory and parameters involved. We'll call what is going on for you practical application!

Like i said in my appologiy i id not know you weren't done, so just delete my posts as to not leave this awesome write up all screwed up by me.I had just woke up and thought it was a completed item,sue me

I've always heard that the only stupid question was the one you didn't ask.

I don't mind answering questions as long as the person answering is willing to learn what I have to teach.

 

[YamaZuki]

This thread is about the theory and parameters involved. We'll call what is going on for you practical application!



I've always heard that the only stupid question was the one you didn't ask.

I don't mind answering questions as long as the person answering is willing to learn what I have to teach.

That's all i do is sit here reading and learning,i wish i had the drive when i was a child.would have gone far in life.
But seeing as i am sitting here for a few months healing a broken collar bone,(2 places)all i have is time to do read and understand and learn even more, i just wish i had a machine shop lol.
My theory is why buy it when you can build it,But some things are better left to the pro's,i will stick to fab and tuning,Machine work is a whole other deal lacking the tools.
But seriousely i wish i could delete my posts interupting you.I lose sleep over things like that tbh. And feel like a dick for it,can't change it tho.
And thanx so much again for writing these things up.SO that capeable people can learn and understand the science behind why things work.

 

[xKroniK13x]

Stickied .

 

[dksix]

I've always heard that the only stupid question was the one you didn't ask.
I don't mind answering questions as long as the person answering is willing to learn what I have to teach.

I've always believed anyone could add to the discussion, even by just asking questions. It helps the thought evolve and expand and I always have plenty of questions. I may not agree with something but I never thoughtlessly dismiss someones point or opinion, knowing that it may be me who is wrong. I have learned more about engines in my few months here that in the past 4 decades of my life, several very knowledgeable guys here which accounts for the quality of the discussions.