Made some time to go into the shed tonight. My last setup had a leak which was screwing with things.. Nothing drastic, but yer. I noticed it. My setup isnt pretty, but its what i quickly whacked together the other day mainly because of time restraints. It works, but as you can see, its.. err.. ugly. Doesnt effect readings, but yer. Ill make a proper adapter at some stage.. Its on the bottom of a LONG list of "to do".
Stock TRX850 cam is 8mm lift. The "kent cam" is 8.4mm from what i remember (someone correct me please) i tested up to just shy of 9mm. In 0.25mm increments.
OK. Should be fairly much explanatory, but ill break it down.
FPS = feet per second. Put a piece of confetti in the air, its how far it will move. IE: its the velocity of the air in the port. Higher is better, to some extent. Low movement means its not getting into the cylinder fast enough.
CFM = Cubic feet per minute. How much volume of air is getting in. More is better. always. (well, theres an exception to that rule too, but lets not go there)
Depression = The relative "power" of the air. How much ability it has to suck something.. Think strong vacuum VS weak vacuum.
With that said.. Im sure you can see that CFM tends to drop off a bit at top end.. Ive gone to almost 9mm, and the trend continues. Id expect total plateau around 10.5mm, or possibly 11mm at the outside. But its dropping fast, so my guess is 10.5mm.
Velocity tends to spike a bit. Partly due to internal turbulence, or possibly me not holding the velocity probe at EXACTLY the same spot every time.. But it was fairly consistent. It was in the middle port, just before the valve stem, in the middle of the runner. Each side was yielding faster FPS, but thats to be expected because of the port shape.
From ~6.00mm and up, FPS is about the same. It also SCREAMED as it was doing it. Its literally tearing the air apart. Its something i really need to fix. The port is just not able to ingest that amount of air with that port shape. It will do it, but it wont like it.
I have some RADICAL designs planned. Time will tell if they end up good or bad. Ill document with pics and stuff later on.. But i got the next 2 days off providing i leave my phone turned off and turn the stereo up in the shed so i cant hear the missus or the kid yelling at me.
OK.. Now for some other stuff.. Dunno how many people know this, but the inside of your chamber also effects flow. Its to do with swirl. Theres LOADS of ways of measuring this. Ive chosen the cheats method because of time restraints, but its inherently messy. But it gives a good idea of whats happening. Saying that, the stuff i used is too powdery.. Its good that its drying almost instantly, but its not getting a chance to stick to anything. Im able to wipe it off the inside of my bench, its like powder, its sticking to the head, but its very weak.. I need something more "inky". Much like dy-mark. It doesnt matter if the air moves it about thats partly what i WANT it to do.
Get a drop of water on a piece of paper,, now blow it with a straw.. all around.. Notice the nice lines it draws ? if you have someone else blow with a straw the same time, you get a TOTALLY different pattern, and different air pressure also does the same.. With a "inky" or slightly more liquid medium, this will happen and really show the path of where the air is actually going.
These were taken at 0.5mm lift increments, the last one is 8mm to show nothing else was happening.
The air was moving fast enough that it wasnt sticking.. So yer.. Ill need to retest with something better so i can see whats happening.
The method is to spray about 2 feet away, not directly at the port, but sort of "let the port pull the paint out of the air".. So that way it has a more natural path.
Not much happening.. Its only really dribbling air in anyway.
starting to see it get into the cracks. This is natural.
OK.. starting to see a defined line between the exhaust ports. Also seeing some bias on the bottom of one of the inlet valves. That inlet valve was usually SLOWER FPS than the other side, only by a touch.
Probably could have sprayed more. But yo ucan see it pooling around that exhaust valve, and it wants to break over.. Needed more time to reveal exactly what it wanted.
You can see it going from one exhaust valve to the other clearly, and then down and around to an inlet. This indicates a clockwise swirl. Its quite large, sometimes swirls are the size of a fingernail.
Its stopped swirling and wanting to break to the cyl side, between the exhaust ports. The swirl is going clockwise from one exhaust to the other, but its instantly going BACK and up at about 45deg.. You can see a heavy line drawn. On the cylinder wall at the 3 oclock position, you can see its got a line that is starting to carry on clockwise again.. Its like its comming off that lower exhaust valve, smashing against the cyl wall, and then swirling again. You can almost see the splatter mark.
Again, not really heavy enough. But you can see quite a collection on the lower inlet valve. Maybe its got a bias to that area ?
Velo's fairly much taken over here. Its got some signs, but nothing new, and velo is really starting to boogie now.. Paint is getting a chance to stick to anything.
I can see its still swirling clockwise some what.
Nothing new to report.. This is 8mm lift. I used a fair amount of paint as you can see. But when its comming out of the valves, its moving too fast.. once it slows down its able to stick as you can see by the layer of blue dusting on everything.
Well, thats about it for the moment. Hopefully i have something new to report in the next day or two, but no promises. Hope you all learnt something and if anyone has any questions or querys on anything, ask away ill answer to the best of my knowledge. (right or wrong, who knows !!)
