High velocity porting....

[Jak]

I did try and separate out the "off topic" comments but I couldnt as it's more than one page.

I've unlocked the thread so you can carry on the porting thread ... please play nicely together!

[Quan-Time]

im back again.. Ive got a fairly busy life now, and dont get on a computer anywhere near as much as i would like. Being easter, i have a few days off now, which is fantastic !

I would like to say that i agree 100% with what HansJ said about his previous post (page2 i think).

Velocity will ruin top end, if you port the CFM in a certain way. It is possible to increase fill rate and gain it right back, at the cost of another area (say idle or midrange, etc).

You really need to focus on your application. 99% of "walk in customers" want a "max cfm, cos my brother-in-law knows a guy who has a 1000hp car, which runs 6sec 1/4mile times, and he knows, so i want that". Now obviously that car is gonna be aspirated (turbo, charger or screwblower). So porting a head is totally different to NA cars / bikes. As is running NOS, and a host of other things. Most ppl just wanna show their penis size by "my car has more CFM than yours".

1hp is ~2CFM of air.. Its a touch less than that, but lets talk ball park figures. Heat, pressure, humidity all play a factor in how an engine will run. If you get that 2cfm into your cylinder FASTER you can decrease your duty cycle of the engine. Think "instead of the engine taking 3seconds to rev from idle to redline (where the ignition cuts out) it can now be done in 2secs". Now this DOESNT increase raw power. All it is doing is allowing you to access the "power zone" earlier. Look at a F1 car.. How quick can those things rev from idle to 19,000rpm, and back to idle again ? its astonishing. You dont increase torque nor do you increase hp, but you get the option to change gears and keep the revs where you want them. Anyone a truck driver here ? heard of the "double clutch" technique ? going from 1st to 2nd gear..
1st gear,, rev, put in neutral, rev the engine while in neutral, put to 2nd, then release clutch.. its to help keep the revs in their "power zone". With an engine that spools up easily, you can counter this.

I agree with putting power where you need it. If you do the odd track day, but mainly ride to / from work, plus a ride on weekends with mates thru the hills / local cruise, you want your power to be in the meat of where you operate the engine at. Start looking at how you want power.

Lets have another example (this might loose some ppl, and i do apologise for that, but most ppl should be able to follow, even Jak ) We are going to use "approx / round" numbers, for the sake of the exercise.

Bog stock TRX850, 270deg crank, not the 180 (is it 96 - 99 for that ?)
redline 8500rpm
max power 8000rpm
idle 850rpm
3rd gear, 60km/h 3000rpm (city limit in australia most places)
4th gear 80km/h 3100rpm
5th gear 110km/h 3500rpm

OK. please remember this is just an exercise, not gospel numbers !. The engine does most of its work around the 3000rpm range, lets give it 2000rpm play, 1k either side, so 2000 - 4000rpm is the meat of where you want your power. 850cc engine, 425cc cylinder. 3000rpm is 1500 power strokes per min. half the "up" strokes are pushing the exhaust out, other half are compressing for the "bang".
Im not gonna go into any maths here, but you can quite easily calculate how much CFM is needed for that rev range. You can also calculate how much is needed for max power.

The valve is in its closed state twice per cycle, in its mid range twice per cycle, and only once in its max lift. So max lift numbers dont really help that much.. Sure you can have high lift cams and what not, but we are talking stock motor.
Get your head on a flow bench, flow it with all valves open, at max lift (8mm), check what it flows, now turn the valves upside down, so the stems are still there, but there is no bottom, it should flow freely. Check that number.
Pretend you get 50cfm with the valves upside down, and 40cfm with the valves as they should be. This doesnt mean anything, except to the person working on the head. Lets pretend the ports are 80% efficient now. (50:40 is 80%). So we know how well the engine works now. (in THEORY, none of this is real world dyno numbers remember)
Lets flow at 0.5mm lift, from 0 to 8mm. Find out how well each lift preforms. You should have 16 measurements now. This doesnt mean anything to anyone, except the guy flowing the head, so DONT compare flow results over the net, with mates, to the guy nextdoor, in most cases, its totally useless. Whos to say their bench flows correctly, or yours either. BUT your results are repeatable (they should be !) so you now have a baseline to work off. Your bench might be out by 9% via air leaks / mis-mounting or something, but long as you can repeat your numbers (pull head off, wait a few mins, remount, etc) then your all set.

Lets now say that at 4mm lift you flow 17cfm. Technically the head would flow 25cfm in 100% efficient state, 20cfm @ 80% efficiency. This doesnt really tell you much other than where you should start looking to improve. What if it flows 17cfm @ 4mm and 32cfm @ 6mm. Well thats great, because flow has picked right up. So you know where abouts you have to do some work.
Theres quite a few things that can change how your power is delivered. induction, IE: kehein carbies. Trumpets / funnel rams, air box design.. Its obvious that Kehein work wonders. Anyone would think they have done their homework, and designed a carbie to match the head and what its requirements are.
New cams (kent cams perhaps). Instead of the cam lobe having a nice progressive and linear path for the valve to open on, maybe we can change the curve, and get the lobe to open a touch faster to 5mm lift, and then normal from there. IE: reducing the time its at 4mm lift and have it at 6mm lift a touch longer, because its more efficient.
Many ppl have stated that putting on kehein carbies, or kent cams, or both, that their engine feels more "responsive" and obviously more powerful. The response is the result of an engine running more efficiently.
Looking at flow thru the head, also look at flow thru the exhaust. If you want your power range to be at 2 - 4k rpm, what CFM is needed, and what velocity is wanted (some ppl say 400fpc (feet per sec) some ppl say 350 is more than enough, i honestly dont know personally). Once your head is flowed, and your inlet is done, flow your exhaust to match that range. Match your cfm and velo to what you calc as "optimum" for that rpm range. Then build your exhaust around that. So at that rpm, your engine will be running upwards of 90% efficient (you will NEVER get 100% obviously, 90% is a REALLY good figure, its closer to about 85% for a well tuned engine i THINK, correct me where required please).

If you are still reading this, and not the tyre / oil sub section ( ) you should have a basic understanding of "no engine is perfect, but engine A can run better than engine B, even tho they are both totally stock". How the cylinder head was cast, how the exhaust is bent (there are tolerances in the factory) its why some bikes / cars just run slightly better than others. The power zone MIGHT not be where you want it. Some cars idle better than others, its the nature of the beast.

EFI can sort MANY of these problems out. At the cost of money and huge development time.
Working your cylinder head is a solution to more power, but its only going to be useful to a degree. the "weakest link" concept will probably reveal your carbies (the stock Mikuni ones) will just not work well, so you need to use better ones. Engine still has a huge "flat" spot, or a "stutter" ? probably the exhaust. Still not happy ? the engine "surges" or has weird power curve ? the cam can fix it up.

Its quite often a mechanics worst nightmare when a customer says "yer its a daily driver, but i want it to be a full on race car, but it has to idle perfectly and get great fuel economy". Yes its possible to do, but the amount of money you need to spend will be bigger that ben hur.
Take a look at the YCCI (yamaha chip controlled intake). Its just crazy. Its a fantastic solution, but the clams they prolly spent figuring it all out, wow..
http://www.mcnews.com.au/podcasts/2006_ ... 1_YCCI.mov 5.6meg Quicktime file.

The twin butterfly is "fly by wire" setup. Sure you (partly) control one set (top ones). So even if you open them 100%, the computer controls the other set, making the "optimum" decision. Much like traction control / launch control. It applies the power the best way possible.
Variable tunnels is a no brainer, longer / shorter ones provide different power curve, so they made adjustable ones. I read somewhere they experimented with an infinitely variable one, much like a trombone slider thinggie, but it wasnt financially viable, it was just WAY too expensive.
Obviously the EFI gets out the last dip by making it all work together when is best. So even tho they worked the head / cam to get power. By throwing a bucket load of electrics at it, they got even MORE power by making the CFM / velocity as close to "perfect" thru the entire rev range.
As for the exhaust, they even have a butterfly in the there as well. To help with back pressure / velocity.. etc.

Sorry to carry on about this. Its a subject that i love and work on regularly. I dont get anywhere near enough time to work on my own bike, nor develop it (head / cam profiles, etc). I still ride the TR1X, but i cant finish it off as i still ride it almost daily and dont have the spare time to finish development on the spare engine. Such is life really.

I hope i havnt confused anyone too much, nor bored anyone. Thanx for your time.

[Killerwhale]

im back again.. Ive got a fairly busy life now, and dont get on a computer anywhere near as much as i would like. Being easter, i have a few days off now, which is fantastic !

Great reading!! Now you can just sit back and wait to be flamed by the "i can change oil dude"

[youngy]

Quan - one thing you could never be called is boring!

[steve speed]

thanks for that Quan Time that was really interesting

[youngy]

and complicated

[HansJ]

C'mon guys, get a life, the real world is calling...



QT: That's what I mean, sadly, it's all about compromises... Let's not dive in to standing waves and so on, I think this is enough for anyone to understand the complexity of tuning (And I am by no means an expert, I've only listened to others, but I am trying to learn as much as possible)

Excellent piece of text!

It's interesting. (And like always, the more one learns, the more one realises how little one knows...) For example, I've seen TRX bench runs with different lengths of trumpets, amazing what differences they can make, and although gaining torque/BHP not necessarily smoothening the output curves. Variable ones would be a bliss

But do not despair, standard engines will benefit from fairly simple porting, i.e. straightening, removing excess material and so on, especially our russian designed tractor engines.

[Jak]

Most ppl just wanna show their penis size by "my car has more CFM than yours".

....this might loose some ppl, and i do apologise for that, but most ppl should be able to follow, even Jak

I shall (when I have a little time later) read through that properly and try and follow ... even if threads are "over my head" I'm picking stuff up and one day I might surprise you all by doing something complicated with my TRX







Quan you are a star - you inspire people like me to learn more. To you and the others who contribute detailed info on projects .... don't stop writing your essays/posting photos.

from the "I can't even change the oil" bird

[Killerwhale]

and complicated

Then you can take it a step further and mod the head for tumbling (as the formula one cars has) and get a more even powercurve. To let everyone know....i just read about this a week ago when a XR turbo rider in Sweden showed off his headjobbie.....

[youngy]

Kw what are we looking at there? What's been done for this tumbling thing?

[Killerwhale]

Kw what are we looking at there? What's been done for this tumbling thing?

You can see that the head´s circular design is welded up.
The effect one is after is kinda what you get with a 1,5l bottle....empty it just holding it upside down....then empty it spinning it a couple of turns.
....but i guess we wait for QT to explain this for sure!

This dude has made "piranha teeth" in the intake also....

[Killerwhale]

Kw what are we looking at there? What's been done for this tumbling thing?

Dudes bike a while back:

http://trx850.motomaniac.net/forum/view ... =45&t=2350

[Quan-Time]

Kw what are we looking at there? What's been done for this tumbling thing?

common misconception.. tumble / swirl has been taken out of the head, rather than being introduced.

The little "rib" bits help make the flow path more straight, or "laminar".

Get a normal every day fan.. Like one with a steel cage on it in your living room. Tie a piece of string to it, turn on the fan. See how the end of it "whips" around ? thats part of the swirl path. Now get a long piece of tube, say.. a paper towel roll. Put the string into the tube, repeat the experiment. The string will still whip around in the tube, but a lot less. If you make small ribs / lines, you can make the flow more even, and smooth out the string even more. Try taping 5 or 6 paddle pop sticks / popsicle sticks along the length of the tube you have. So it has 6 internal "splines". put them standing tall in the tube, rather than flat, if you get what i mean.
This helps increase efficency in the port.
When you (well when some ppl anyway) flow a head, you can use wands, flags, or wahtever you want to call them. Wand is a small piece of wire. Think MIG welding wire, 0.9mm diameter. Small ball of about 1mm - 5mm on the end (most ppl have several of varying sizes). You start flowing the head, place the ball in the path of where you might be having problems. Sometimes the ball wont effect cfm / vel numbers at all, other times it obviously takes a bit of a hit. because of the obstruction. but sometimes, you get INCREASE in cfm / vel..
A flag is just a piece of fine string (sewing cotton / thread) on the end of a piece of welding wire. Make the flag about 2" / 50mm long. Start flowing the head. Because its shortish, it wont flap around too much on its own, it mearly gives a visual indication of how the air is moving.
If you were to get a cigarette, and blow a big bit of smoke into the port, and watch, you would visually see the air is "tumbling" in the port. Obviously you need ALOT of smoke and would start to cough really fast. So a flag will flap around and show you. Its a fairly good indication. It will also tell you if theres a high / low pressure system going on. Meaning this.
Around radius / bends, air must change direction. It does this by all the air piling up and creating a mini high pressure zone. because air is more dense there, there must be a low pressure zone. The flag wil usually flow into the low pressure zone by itself. The high pressure air will "push" it..
Sometimes you hold the flag onto the left wall of the port, and half way down, it comes right off the wall into the middle of the port.. almost like a 45deg bend..
obviously the air is having huge problems navigating that part of the port. So you break out a wand.. Start waving it around and seeing what happens.. Not fast.. very slowly move it around the high pressure area to "break up" the air.. See if you can improve it. MOST times (not all) when you find how to fix it, the problem is down port of where the ball is. Not always, but sometimes. Get some putty, try to build up an area, if you cant fix it, start to shave a little off with a grinder when you know EXACTLY where the problem area is. Go very little at a time.

Sure its easy to take material off, but you take too much off you end up using jbweld / filler.. as hansJ said, yes you can use it, but you want to use as little as possible if you can.

Altho air is treated as a "fluid", its quite different to what most ppl think of fluid, like water / oil. They compress no more than about 1%, but you can get HUGE pressure with it.. 40psi oil system anyone ? where as air can compress 50% and only get 15psi. So air tumbling down a port in the swirly motion all over the place, you get huge "separation". This means you can effectively pull the fuel right outta the air by making it turn into droplets rather than keeping it as a vapor. Im not sure how it exactly works, but i think its along the lines of "if air is constantly bouncing around in high / low areas, the vapor droplets dont compress, but because they are in a smaller area they "attach" to eachother, and form bigger droplets.. Its partly why some fuel injectors are right above the valve, to basically not let this happen, and 12hole injectors rather than 4hole, to make a finer mist, so its more uniform. If you have a really well shaped port, sort it out, you can move you injector further back, like a motogp bike that puts the injector over the trumpet. Ive been told (but never tested, and honestly dont know how to) that the fuel is pulled apart and evenly balanced in the air. Meaning you have a VERY uniform layer of fuel / air shooting into your ports / engine.. which is good.
Hopefully you have a better understanding of whats going on now.

reshaping the combustion side..
Its worth about 2 - 5% of your gain in HP if its done correctly. You can LOOSE 2 - 5% if its done incorrectly at the same time.
This is a REALLY touchy subject, and i honestly dont know much about it. Many ppl are getting into "wetflow" testing. get water, put in a few drops of UV reactive dye, flow the head on a custom wet-flow bench, get a UV light, you can see where the dye piles up to things, obviously the valves will glow like chernobyl, but you can see in the combustion chamber where the fluid is piling up. Ive heard that some ppl even shape the top of their pistons to get better flow. They sacrifice some compression (go from 11:1 to 10.3:1 for example) and are getting MORE power. The chamber fills really well, less compression means a touch higher rpm, which means slightly more hp. Because the engine is more efficient, they get more hp for less wear. Why do you think most top end sports engines never claim true compression ? look @ motogp, they claim this n that, but usually leave out peak HP and compression. You do get more HP with more compression, but an efficient engine will always win the dyno shoot out.
Valve shape can play a HUGE role in this. Notice the valves are concave, not convex ? ie, they are dimpled. You can get some that are flat, or even bulge a touch.. You can get some extra compression by changing your valve type. So even tho you shape your piston head, and loose a touch of compression, you can get it right back by changing your valve shape.

Now, im gonna give some HOMEWORK !!! for you lovely ppl. There is no right or wrong answer here, but instead of reading my ramblings, do a bit of research of your own. This is a very taboo subject right now. (well, its quite old, but its made a come back).

"Quick burn head".

refer KW's pick, the one on the left, the red one, has been filled up, the one on the right, the old dirty one, is stock / not filled up. you should be able to see a difference (please note that this head is NOT !! a quick burn, but it can be done)

By reshaping / filling up the parts of the head which are dead space, what are you changing ? are you adding or taking a problem ? explain.

Im going to give you a REALLY big hints.
Flash point.

so what ideas about it do ppl have ?.. remember, there is no wrong or right answer her.. its just a friendly open discussion.

[HansJ]

The pics are crappy, or my eyes... What do You see that's been done to the head? And obviously my English sucks as well, as the "hint" doesn't help me a bit. Which filled up parts do You mean, the "plastic" in the ports? And I am not sure what You mean by the question either. Not many rights for me today

But please explain, I find it interesting, and please don't stop rambling, it's also interesting! Not many guys have that kind of knowledge. There are not many tuners that do the maths, with a proper design and thought. Most seem to just let the grinder talk... (Which in many cases can improve, but in other cases even destroy...)

[Killerwhale]

The pics are crappy, or my eyes... What do You see that's been done to the head? And obviously my English sucks as well, as the "hint" doesn't help me a bit. Which filled up parts do You mean, the "plastic" in the ports? And I am not sure what You mean by the question either. Not many rights for me today

But please explain, I find it interesting, and please don't stop rambling, it's also interesting! Not many guys have that kind of knowledge. There are not many tuners that do the maths, with a proper design and thought. Most seem to just let the grinder talk... (Which in many cases can improve, but in other cases even destroy...)

It´s all in Swedish at Sporthoj, search for user "Boost 3" and the thread "portat o klart"