timing key Options

[Gettin2Old]

And what part of the grooving idea is BS?

I have done it on both 4-strokes & 2-strokes and there is a noticable improvement all across the board.

Many other people have done this technique with great success too.

In the common theories about combustion efficency, what part of the grooving technique are you not agreeing with?

[orville-x]

My comments weren't directed toward the head grooving specifically, but some of the "explanations" of how the combustion process works and why grooving the head improves combustion. My feeling is that if someone doesn't understand what is going on "behind the scenes" so to speak, that person may not really know what is really responsible for the improvement. As far as grooving the head is concerned, the idea isn't new. When I'm bored, I'll dig around in some of my old IC engine books. I'm almost certain I've seen things like this before - stuff that was tried and abandoned because a "better way" was found. I could see where the groove may generate additional turbulence in the combustion chamber and improve combustion. I have a theory for why it might make an improvement, but I've also seen some combustion chamber types where I'm convinced it wouldn't make much difference at all. I don't think its some "universal" thing that will make an improvement anywhere its done.

[cfm]

Side track, but I feel very important as we are talking combustion chamber:

Wet flow is making a huge difference in 4 strokes, even though it is starting to raise more questions than answers. Comb shape - plug placement (check vid below), etc,etc,etc

2 strokers doing this yet ?

Here's an example:
http://www.youtube.com/watch?v=TFi3KLU6pfQ

[Gettin2Old]

Here is a link to an article on wet-flow testing and what it is,
http://www.engine-builder.com/ar/eb110670.htm

The part that stood out for me was the 'Sharp Edges" help combustion mix flow.

This would lead me to believe that the grooves or slots cut into the head to vent the squish band area are creating sharp edges.

The main advantage of this technique is getting the fuel to ignite at the correct time, not late in the combustion cycle where it adds no presure to the downstroke of the piston.

if we get the fuel to light at the correct time, we are extracting more power from the same amount of metered fuel.
Without the groove (S) cut in the head, the mixtyre trapped in the squish area does no light until later. With the slot it gives the flame front a chance to ignte that stagnant mixture caught in that area at the correct time.

it is this simple stuff that many people overlook, it's just horsepower sitting on the table waiting to be used.

if someone with available dyno time would do this to see the benefits, I bet once the news gets out (besides this and a few other forums) it will be the next big step in combustion chamber efficiency.

Efficiency equals horsepower

This post has been edited by Gettin2Old: Sep 18 2007, 02:09 PM

[cfm]

G2O - When you mention sharp edge where you referring to this quote from DM " IF you sharpen the edges of the seat."

If so, this is the valve seat he is referring to. Problem is, hmmmmm, how do I say it, a bunch of years of reading to kind of understand what air is doing in a certain type of 2 valve 4 stroke motor. There is so much to port shape, design, valve shape/design, throtat and bowl shape/design and etc,etc that it will make your head spin. I've been studying teaching/articles/talk/etc of Darin Morgan and many other guru's (DM is near or at #1 in my mind) just so I can get to the level that I can kind of understand. The shear amount of details that they cannot simply write down + share is staggering.

Anyway, please do not simply things based off of one small article type writing.

As you know, since I do lots of R&D and manufacturing of some go fast pats, I know that there is always a possibilty of something working, even if it sounds weird or doesn't sound like it will work. You never know until you try. In fact, 1, 2,3,4,......100 tries at something doesn't always give you valid results for many times other things have to be changed at the same time for it to be effective .

Lastly, I'd love for you to do some research in this for the Fusion 900's. Seriously. I would get a few sets of heads vs just one so you can change somethings and see what happens. No, I can't help you $$$ or with parts, thats where most of my $$$$ goes - my business stuff. I tinker on 4 cycle stuff, not 2 cycle. I keep my sled stock so I can't blame myself if it shcts itself in the middle of no where. I need one seasonalhobby out of the year I'm not fugging with something. LOL.

[TheBat]

wouldn't sharp edges lead to hot spots in the combustion chamber? that could cause detonation. Unless there is so much airflow in those areas that they are self cooling?

[Gettin2Old]

They can & they can't. ( I know it is a crappy answer)

Combustion theory is just that yet, just a Theroy

There are things that shouldn't work but do wonders, and things that should work, but make things worse.

15 years ago everyone was polishing intake tracts, now it is the exact opposite becuase more things are being learned every year.

it is a science and an art. But basically no "major" improvements in the combustion area of a piston engine have been realized since it's inception.


there are tweaks and changes happening all the time, some work some don't. you could take 2 exact engines and have one perform like crap, and the other be a monster. and it could be one little miniscule item that is different.

With the grooves, everyone thought it would cause hot-spots & detonation, when it did exactly the opposite. they thought heads would start cracking. it is this little tweak that has been overlooked that is making some great strides in getting the fuel to burn at the correct time without exploding and generating excessive heat.

[Jesse Lackman]

Just banging around here looking for minimum quench clearance for two strokes and had to comment on this old thread. I too think the drilling in the pistons is what's referred to as gas porting, the holes are drilled from the top into the ring groove behind the ring so compression forces the ring out against the bore. Lateral gas ports are drilled in from the sides on top of the top ring, they are a half hole like a half moon that lets compression pressure get behind the ring to again force it out against the bore. Lateral gas porting is not visable from the top with the head off. Gas ports are commonly used in automotive engines with the newer .043 thick compression rings.

Interesting to see references to grooving. I did a pretty involved dyno test of quench grooves on a Dodge 360 engine. We had some pretty long and involved discussisons on speedtalk.com about grooves, quench, octane, and detonation;

http://speedtalk.com/forum/viewtopic.php?t=5907

The reason I was searching for quench information is because I have to rebuild our Polaris Storm 800; http://www.hardcoresledder.com/forums/inde...howtopic=396267

It looks like around .060 is a commonly recommended minimum quench clearance for snowmobiles, we go down to much less that that on automotive engines, I've seen as little as .035 on a Dodge bigblock 470, about .032 on a Dodge smallblock with no sign of the piston hitting the head. Don't know what the Polaris 800 triple will be like as far as setting up a good working quench clearance.

I am interested in trying grooves on it too.

Does anyone know if the Wiseco 75mm 861cc kit can be put in stock 1995 castiron sleeved cylinders? That would be a .120 or so overbore, seems like a lot, if possibile that's what I'm looking at.

Thanks.

[Gettin2Old]

Sorry I can't help you on your Storm question, But I appreciate the link to the speedtalk topic about adding grooves to the squish band. This topic dies a while ago and I never did find a decent donor head to groove to see what it would do for our CFI engines.

I think we would see better results on the oldr carbed engines with adjustable timing to take advantage of leaning it out and bumping the timing farther than we usually can.

Are you going to groove the Storms heads?

[LUBA]

Back to the original question. Yes you can put an offset key in the cfi motors. I just put a 1.5 degree in my htg 975. Several people have run them on the HTG 975 with success. Some are running the 2.5 key, I was told by the guy I bought my motor from the 1.5 worked better for him. I just put it in today.

[05cleanfire]

how is your 975 install luba??does it pull like a freight train??

[cfm]

Hey Jesse, good to see you over here and into sleds too. I'm a member over there too (same name - 'CFM') and have appreciated all your input and data. I had read your 'groovy thread' a handful of times. Thanks again.

I have nothing to add technically here. Sledding is my only motorsport I don't tinker with other than maintenance. The 4 cycle world eats all my labor time and most of my thinking time. I like following what the 'sled heads' are up to. Fun to watch and read. Also gives me a mental break from my daily responsibilities.

Jack Struthers at http://www.carlscycle.com/eshopitems_cat_2..._Snowmobile.htm seams to be one of the head honcho's with Polaris performance.

On this site, member name 'Pockets' seems to really know a whole lot about everything Polaris - stock and modified. Yes, there are many others too but his name always stands out. Seems to really like to help everyone. Here's a search under his name.
http://www.hardcoresledder.com/forums/inde...sult_type=posts

Hope this helps.

[spencerpaving]

everybody only "hears" that keys dont work on the polaris, i ran a 2.5 degree on my 975 for two years with out problems, on my new big motor with twins i made my own key that advanced the flywheel .080 and picked up 12hp at dynotech and brought the operating rpm down were it should be with the twins. htg has been doing it for three years and no issues. artic cat efi has the same sensors and pickups similar to polaris , so a key in those would change injector timing too? thats my two cents take for it is wortth

[05cleanfire]

o.k.,where does a man purchase one???

[LUBA]

fett brothers or hi perfomance egineering

[xc6]

Are the keys only beneficial and/or necessary on the 975 kit or will a stock motor with add ons benefit as well?

[Jesse Lackman]

Hey Jesse, good to see you over here and into sleds too. I'm a member over there too (same name - 'CFM') and have appreciated all your input and data. I had read your 'groovy thread' a handful of times. Thanks again.

I have nothing to add technically here. Sledding is my only motorsport I don't tinker with other than maintenance. The 4 cycle world eats all my labor time and most of my thinking time. I like following what the 'sled heads' are up to. Fun to watch and read. Also gives me a mental break from my daily responsibilities.

Jack Struthers at http://www.carlscycle.com/eshopitems_cat_2..._Snowmobile.htm seams to be one of the head honcho's with Polaris performance.

On this site, member name 'Pockets' seems to really know a whole lot about everything Polaris - stock and modified. Yes, there are many others too but his name always stands out. Seems to really like to help everyone. Here's a search under his name.
http://www.hardcoresledder.com/forums/inde...sult_type=posts

Hope this helps.

Thanks, I did notice somewhere here you referring to speedtalk and knew you were there.

I think we would see better results on the oldr carbed engines with adjustable timing to take advantage of leaning it out and bumping the timing farther than we usually can.

Are you going to groove the Storms heads?

I might try grooving the heads but the main problem I have with grooving is that groove placement seems to be such a shot in the dark, might be less so with a two stroke. What I mean by that is it seems to me that detonation occurs on the intake side in a four stroke chamber in the long chain hydrocarbons thus it follows to aim the groove at the intake side, specifically the outer intake edge of the chamber to stir up the long pre-flame reactionable hydrocarbons molecules. But that isn't what people do, they aim it at the spark plug - some think the groove acts as a "fuse" allowing flame travel into the quench area. That means the groove is a two way street - it is easy to get into the trap of thinking of it as only the blast into the chamber when the piston comes up. So it seems to be a guessing game, I know some on speedtalk did have real success with grooves in a two stroke but I don't know exactly how those grooves were positioned. If grooves have an effect on timing requirement it would likely mean less timing.

Does anyone have an opinion where detonation occures in a two stroke - the exhaust side or the intake side?

Reference; -->> Detonation starts on intake side of chamber. True? << (Some of these speedtalk links are to the Advanced Engine Tech forum and require a membership and log-in.)

This post has been edited by Jesse Lackman: Feb 18 2009, 10:01 PM

[05cleanfire]

fett brothers or hi perfomance egineering

thank you

[Gettin2Old]

Thanks, I did notice somewhere here you referring to speedtalk and knew you were there.
I might try grooving the heads but the main problem I have with grooving is that groove placement seems to be such a shot in the dark, might be less so with a two stroke. What I mean by that is it seems to me that detonation occurs on the intake side in a four stroke chamber in the long chain hydrocarbons thus it follows to aim the groove at the intake side, specifically the outer intake edge of the chamber to stir up the long pre-flame reactionable hydrocarbons molecules. But that isn't what people do, they aim it at the spark plug - some think the groove acts as a "fuse" allowing flame travel into the quench area. That means the groove is a two way street - it is easy to get into the trap of thinking of it as only the blast into the chamber when the piston comes up. So it seems to be a guessing game, I know some on speedtalk did have real success with grooves in a two stroke but I don't know exactly how those grooves were positioned. If grooves have an effect on timing requirement it would likely mean less timing.

Does anyone have an opinion where detonation occures in a two stroke - the exhaust side or the intake side?Reference; -->> Detonation starts on intake side of chamber. True? << (Some of these speedtalk links are to the Advanced Engine Tech forum and require a membership and log-in.)

Since 2-stroke heads are hemisphericle, I do not think your question can be properly answered since there is no intake or exhaust side of the head with odd angles to deal with such as wedge engines have

Singh has some pictures of grooved 2-stoke heads on his site, and some figures of how far to stay away from gasket edges. And some links to interesting dyno results from a grooved Doo engine with carbs. it has been a while since I have done anything grooved, but the saws and my old briggs are still running at their peak from the experiments on them.

Timing key;
You 975 guys are getting great results by using and advanced key, but that is a 975.
many things have been modded, has the stroke been chaged too? any little mod can make a whole bunch of differences in how things flow and work together and bumping the timing injector and ignition may have help bring everything back together again.
The results I saw from a timing key were from a stock 900 CFI, and the results were not good.

[spencerpaving]

i think you might be right GTO i do not know how or if they would work in a stock engine , but i do know they wake them up on the big bores