ESE's works engine tuner

[Frits Overmars]

Attachment 296833Valves dimpled on the head like a golf ball for better air flow

No doubt the dimpling will do what it's supposed to do: promote cash flow .

[jonny quest]

That's a pretty bold statement without having tried them yourself Frits. But again, this is not a 4 stroke thread, so I'm not going to get into a pissing match with anyone over this.

[Grumph]

That's a pretty bold statement without having tried them yourself Frits. But again, this is not a 4 stroke thread, so I'm not going to get into a pissing match with anyone over this.

Jonny - i see you've only eleven posts, so maybe you haven't worked out that on KB pissing matches are normal - and even encouraged....

By all means start another thread on this subject and let's be at it.....i've never tried dimpled valves either but my 4 stroke experience is at least as long as Frits 2 stroke experience - and i wouldn't give them house room.

[Frits Overmars]

That's a pretty bold statement without having tried them yourself Frits.

It's pretty bold to state that I haven't tried dimples Jonny. How would you know?

[wobbly]

If you can make the assumption that "they " have 1/2 a clue about what they are doing, then I can also make the assumption the original manufacturer
also had 1/2 a clue as well.
If so then the original timings of 90* and 121* by their very nature would produce a small ( though not necessarily correctly matched ) blowdown STA.
Then by simply lifting the cylinder , the transfers suddenly become suitable for a full noise road racing setup,but that small blowdown number remains relatively the same.

Its very similar thinking to lengthening and shortening a pipe by chopping or sleeving the header.
Sure the tuned length is being affected, and the engine may in fact respond to this change favourably, but if you fail to realise that having a header say 28% or 36%
of the tuned length will invariably produce huge holes in the torque curve - due to the incorrect positioning of the diffuser - then that for sure indicates only 1/2 a clue is present
and the result is exactly as deserved.

[wobbly]

To prove my point about the pipes, here is a dyno graph of a pipe designed using TSR for a 490 Banshee.
The rpm was some 1500 down , so of course they cut the header, oh dear even less power.
I redesigned the pipe ( with exactly the same length as the shortened version ) and it suddenly seems to work a little better.
Amazing eh.

[wobbly]

Golf balls with dimples fly further due to the fact they create turbulent flow in the boundary layer.
This turbulence close to the surface pulls the laminar flow in the direction of travel into a smaller area behind the ball in flight, thus reducing the overall drag.
Simply dimpling a valve will for sure create the disturbed flow conditions on the surface, but a valve isnt round, so the effect of reducing the disturbed area
behind the valve head doesnt exist - no free lunch.
If this did actually work then you can be sure all the Nascar and V8 Supercars and F1 valves would have this simple mod - sorry they dont.
Same as grooving the squish band, an Indian guy patented the idea years ago, and if it was so damn good then any one of the big manufacturers would have bought the rights.
Yamaha paid a fortune to the sly old fox Dr Erlich for his patented offset combustion chamber, they used it once in the TZ 250 G model, and as we know all that did was deto its tits off
due to insane MSV on one side and none on the other - no free lunch again.

[jonny quest]

Who said a Nascar team isn't running them... and a few factory MX teams. .. and a factory US Super bike team?

Highest velocity point is at low lift. SATOP did some computer modeling. ..honestly I don't know if it's a true laminar situation, or fuel atomization scenario. In a 250cc MX bike typically .3-.4 HP gain. I'll take that any day.

[husaberg]

Sounds a bit ranti tanti so your point is exactly.

I think what he is trying to say is take a holistic approach to what you are doing.
For instance if you run your changes in a sim, but use the header shorten by 25mm and then do the same sim, but shorten the mid section by 25mm. pipe length the same, Yet results different.........

As for the valves Jonny mmm................I will sit on the Fence but i do note...
I see they are Ti.......so likely lighter, seem to have a different shape than std ( Frits would appreciate their shape )......... and might even rock up the comp a bit too..(underneath) they might have a new set of seats to go with them, and then sit a little more proud too? plus have a better seat than those which they replaced............
Were the dyno results carried out with the same valves pre and post dimpling?
pipes very pretty though......

One other bit that maybe Frits won't even know is the odd set ups Nascar have to bend arround their rules, which result in engines with rather odd quirks, Huge comp (like 18;1) and tiny ports with 100mm bores turbulent heads with extreme intake velocity........(like the speed of sound)

[jonny quest]

Yes, A B A B testing numerous times.

I've never had luck shortening a header after a good length was found. .. like Wobbly has said, 31-33%. Always error on long side.

The end of diffuser has shown to always be the biggest influence on power for me. 1/8" long or short would always make or break a pipe for me. That was always more influential than anything. If you had a pipe that worked pretty well. .. but wanted a bit more rev.... take length from mid section.

If you wanted to lengthen pipe adding to header usually worked well for a quick first attempt. But shortening it at header...almost always hurt to many other variables if it was in the ballpark

[2T Institute]

Attachment 296833

Something I have just seen on the net. Valves dimpled on the head like a golf ball for better air flow over there surface, so clever I don't know why it had not been done before.

Looks like your a victim of a bit of ASTROTURFING via a trail of bread crumbs from the Williams MotoWerx website

http://en.wikipedia.org/wiki/Astroturfing

[wobbly]

Well im involved in building a full house classic Triumph engine for a customer ( though I hate compressors with a passion ) and have been discussing valve/port geometry with several friends who build engines
at Hendrick ( Nascar Chevy ) Roush ( Nascar Ford ) Yamaha MotoGP and Mecedes F1 so I know none of the TOP engines in those fields have valve dimples.
It for sure would seem that the idea could do " something " but the golf ball analogy doesnt cut it - so if it really does make power in a true back to back,then
some other effect is in play.

The point I was making about cutting or sleeving headers to do a dyno test, is that simply doing that and trying to analyse the results is completely pointless
if you havnt measured the pipes beforehand to see what the original design intent was.
If the header is short to start with, and you then shorten it more, the tuned length may be perfect, but the negative effect from the now silly short header length
will overpower any of the good effects of the overall length.
Conversely if the header was short and you lengthened it, the power increase may be mainly due to now having a " correct " % of header - though the pipe length may be completely wrong for the port timing.
Im just trying to help those with as you say " 1/2 a clue " get a bit closer to the full clue - and if I dont help with this then who the hell is.

[FastFred]

Your explanation makes sense of Fixers dyno graphs. It will be interesting to see a post from TZ with a new (after modification) dyno graph explaining their reasoning for the cylinder plate approach. But it may be a bit of a wait as I hear they have had a woopsie with the dyno computer and need a replacement copy of the Dynojet software so they can commission a replacement computer.

[F5 Dave]

. .
Im just trying to help those with as you say " 1/2 a clue " get a bit closer to the full clue - and if I dont help with this then who the hell is.

Not Santa Claus, - he’s a Rotary partisan

yeah we appreciate it Wob.

[jasonu]

Who said a Nascar team isn't running them... and a few factory MX teams. .. and a factory US Super bike team?
.

But are they the WINNING teams???