|
|
Post by solo2racr on Aug 13, 2008 10:45:45 GMT -5
Hi Solo2Racer. Are you the person who does the heads at NR performance? Yes Is there much advantage in going further than what you normally do, ie raise the port slightly as per the article. Not having a flow bench (yet) to make comparisons to what the article gets for numbers, it's hard to say what more can be gained for sure. I'm sure there is more to be had but the question is "how much more". The whole idea is to use as much area as you can that is available though the opening valve. What's happening with the stock head is that the open valve area nearest the edge of the cylinder wall is not being used. Some will look at the SR head and not like the angle (offset to the left) that the port comes in at. I prefer to be an optimist with this design. This can be used to get a swirling of the intake charge inside the combustion chamber to get a more complete burn. It may ultimately not flow as much as a head with a straighter port but, one needs to look at the whole head and not just one port. This is one thing the article never touches on. Just intake port flow. One other thing they fail to talk about is the exhaust port. After all, the more you get in, the more you have to get out. It the same as the intake in that you need to take advantage of as much of the open valve area as possible. While they do not mention it in the article, the reason for finding what they did is call the Bernoulli effect. This is also what makes wings on aircraft create lift. Or inverted, makes cars stick better to the race track. I actually do some minor reshaping inside both ports but, without welding on the head. I do it a bit differently than in the article but the idea is the same. As an aside I was discussing the port with a guy who does a lot of car heads and he said that at a guess the port needs opening at the top and filling in at the bottom but as these heads were not his speciality then he would only be surmising. He's right. That is what they did in the article. |
|
|
|
Post by hudriwudri on Aug 13, 2008 15:17:25 GMT -5
Hi, Would anyone have any pics of a flowed head (SR500) they would like to share. The knowledgebase now of how to port these heads is fairly scarce and the people doing the work have asked for some starting points before they start grinding and flowbench work. I would of liked Carl to do the work but at present he only does complete rebuilds so I have to go the do it yourself route. Thanks in advance. Alan here is a lil pic of one with hemi squish areas:  and here an older one were one can see a lil the finalshape of the port and the throatarea even though that head is allready ages old and nowadays quite outdated.  funny though that the engine guy thats operating the flow bench seems i.m.h.o. a lil clueless(sorry if that sounds smartasstyle) since with the proper operation of the flowbench there is first the measuring through means of the bench and velocity meters and other assorted means and thus one should get a allready pretty clear picture besides some peculiar specialties of the sewer pipe shaped sr-port since the port is quite kinked unfortunately and needs as mentioned special tricks to make it flow better and not have the mixture separate. kind regards christian |
|
|
|
Post by caferacercarl on Aug 21, 2008 4:40:02 GMT -5
And thats a LOT of hours work in the picture above, and these engines really go hard done at this level, but someones got to pay us for it, we don't do it for fun, we have bills to pay. many people have phoned me from around the world from some very good tuning houses and couldn't understand why I wrote the VMX articles and shared years of R&D , I told them out of frustration of not being supported by owners and moving on. Stew Ross does his homework,and he will be happy...cheers.
|
|
|
|
Post by solo2racr on Aug 21, 2008 10:33:54 GMT -5
That's funny. I did a pair of Hemi style squish (like the top pic) aircooled VW heads 20 years ago. The nice thing about those is that the material is already there. Doing dome pistons tops to match the squish was also fun. Carl is right. A LOT of hours.
|
|
|
|
Post by hudriwudri on Aug 25, 2008 6:47:36 GMT -5
Nevertheless it was (and is  ) a lot of fun doing especially considering the increase in performance it brought (together with other mods on the upper end, and me loosing since that pic 20ibs ;D). Have done several more since then and one gets fortunately faster and better with experience in doin so ;D kind regards PS: nevertheless it´s unfortunately somewhat true that people have inhibitions wanting to be dishing out money for a bike that doesnt cost too much to begin with. Especially considering the amount of work necessary for "real" efficient SR ports, which is i.m.h.o. the next point since in stock they perform as good as a sewage pipe  |
|
pcnsd
Full Member
Posts: 113
|
Post by pcnsd on Aug 26, 2008 16:52:25 GMT -5
Before beginning, I’d like to thank Caferacercarl for his writing’s in VMX 29, 30, 32, StewRoss for posting the full info on the TT500E hop up, and hudriwudri for reminding me about active combustion chamber concepts. The following is the result of your writings, efforts and photos. This particular thread has been very good and resulted in a lot of fun for me. (IMHO).  I began by porting the head following the general guidelines in the hop up article, but opened the intake port to 40mm per Caferacercarl. I use a 22mm carb spacer to help position my VM correctly and it came in handy as the port guide. (I will be using a 40mm VM carb from a Husky 500.) When you open the port to 40mm and stay away from the port floor, the floor hump described in the hop up article, just kind of appears out of the metal. Regarding the combustion chamber, I recall from a seminar I once attended that this type of chamber had several of things going for it, but is typically used in a wedge chamber and not on a Hemi. The spark plug position and it’s entry angle are less than ideal still, I thought it could provide at least some of the supposed benefits (resistance to detonation, better fuel charge mixing and less heat transfer to the pistion) I am running a Wiseco 90mm 9:1 piston which on calculation for actual compression on my bike worked out to 8.4:1, so a little more compression may not hurt either. The chamber mod it self was very tricky and I thought I had scrapped the head at least once. Welding next the valve seats was difficult at best. Also the original chamber mod used 3 scallops on the spark plug side. I discovered on observing fluid flow via my garden hose that the scallop on the intake/spark plug side caused disruption of the flow out of the port so I ground it off and that final layout is what you see in the photos. The gasket is shown for reference.      PC |
|
|
|
Post by wotavidone on Aug 26, 2008 19:19:22 GMT -5
Wow. It does not matter one bit whether you get a performance increase (though I'm sure you will). You will at least have the satisfaction of knowing that you are riding around on a true work of art. Well done, mate.
Mick
|
|
|
|
Post by StewRoss on Aug 27, 2008 1:44:49 GMT -5
Very impressive...keep us informed as to how it goes. SR  |
|
|
|
Post by manxman on Aug 27, 2008 8:27:58 GMT -5
Nice work!
|
|
) a lot of fun doing especially considering the increase in performance it brought (together with other mods on the upper end, and me loosing since that pic 20ibs ;D). Have done several more since then and one gets fortunately faster and better with experience in doin so ;D
