50cc RACING engine...

[kliff]

OK, here's the deal.... I got too many HP qmb139 parts sitting on the shelf, and the Twist N Go at Indy is a couple of months away.


I'm thinking of building either an 80cc or 72cc RACING engine. Not a warmed up street engine, but a racing engine.
Milled 12 degree intake and exhaust ports, custom intake and exhaust manifold, ported polished, & matched, lightenned valves,
24mm carb, gas ported piston, NEW crank & rod assy,NEW oil pump, modified oiling system for positive oiling of left side main bearing, Prodigy variator, and lightenned & balanced clutch shoes. new belt, springs, and more "one -off" special construction labor than you can shake a stick at

But I'd like to see some interest, if not a cash commitment to buy first. Not cheap, at $600.00 shipped, but you'll be getting MORE than you money's worth. If I get a cash commitment, ALL details will remain between me and the new owner, otherwise, I'll do a semi-detailed build.....gotta hold something back, just for the owner's knowledge. LOL

What do you say guys, gonna take me a month to build, so that's delivery around the 3rd week of March. Plenty of time to install and tune before May 1st...any takers?

[zedooo]

Will you do the head-quenching, Singh-grooving masterpiece on it? I'm planning on trying that, but I don't know if it's worth the hassle

[kliff]

Mar 3, 2010 5:23:29 GMT -5 zedooo said:

Will you do the head-quenching, Singh-grooving masterpiece on it? I'm planning on trying that, but I don't know if it's worth the hassle

Good question.

"head-quenching, Singh-grooving..." what is it? Maybe I know of what you're referring by a different terminology, maybe not.
Edumicate me, please.

[zedooo]

hehehe







Singh grooves:

somender-singh.com/

[Rebel]

I've actually heard of that grooving thing, didn't remember the entire name of it and don't know how effective it is. a lot of these things seem like black magic at times. At first glance, you are bumping the compression up, it is those grooves that have me befuddled.

here are some other references to look over;

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

www.hotrodders.com/forum/engine-efficiency-136018.html

[zedooo]

sounds like good stuff to me! if I'll get the time needed, I'll do one head with the grooves and the porting, one with just porting, and get one stock. then we'll see the real differences.

[Rebel]

for the quench plate here is a informative post I found in a car forum The posters name is Curtis73 and it is on hotrodders dot com

As this discussion progresses, I want to bring up something important. I want to distinguish between combustion efficiency, thermal efficiency, and fuel efficiency/mpg. Some things you do to affect thermal efficiency will affect MPG, but not always in the "right" direction.

Thermal efficiency can be thought of as how much of the energy (BTUs) in the ingested fuel gets released during combustion.

Combustion efficiency is how much of that released heat is transferred to the piston as force. These first two are usually just lumped together because alot of it is interconnected.

The third is obvious; how many miles you get from a gallon of gas.

The best way to increase thermal efficiency is to increase compression. When you give the ingested charge more energy in compression, it usually responds by releasing more of its stored heat. It can increase MPG, but it also almost always requires more expensive fuel, completely negating the benefits. It also takes more energy to compress the charge, so some of the extra energy you release goes right back into compressing the next cylinder.

The best way to improve combustion efficiency is to use tactics that allow higher compression without detonation on cheap gas. Quench is very pivotal to that. Quench (sometimes called squish) is an effect that you can achieve by using heads and pistons that have a flat area that comes close together beside the chamber and/or dish of the piston. Like these photos illustrate, notice these SBC heads have a flat area beside the combustion chamber, and the D-dish pistons have the dish offset to match up with the chamber. As the piston rises to meet the head, that little area squishes the charge causing it to violently swirl. This does two things primarily; makes sure the mixture is homogeneous (uniform) and its like fanning a flame making it burn much faster. What this does as a pleasant side effect is allows for less ignition advance and therefore the engine can sometimes support more compression on cheap gas.

Here is a photo of a commonly used L98 head from a TPI 350 showing the quench pad beside the chamber.


Here is a photo of a D-dish piston designed to match up with the quench pad like this Speed Pro forged piston:


Piston/chamber design is also very important. Typically the most efficient design is a flat top piston set to a proper quench height in a properly sized chamber. Domes kill flame front speed requiring more ignition advance and lowering detonation tolerance. They also often require big open chambers which makes it almost impossible to engineer a quench pad. Hemis were known for their power, but they were also known for their intense thirst of high octane fuel. Conversely, tiny chambers require big dishes in the piston; sometimes so much dish that no quench will be available

Now take a look at Vortec chambers with their heart-shaped combustion chamber. The altered shape of the quench pad is very effective at inducing much more swirl; so much so that typical ignition advances are in the 32 degree range compared to 36-38 degrees for an old chevy. The vortec head is on the right, the traditional small block on the left. Its a subtle difference, but it makes a world of change.



Another trick you can use to squeeze out some MPG is polishing the chambers. Eliminating hot spots on the rough casting prevents detonation. You can also try using heat-rejecting coatings on the piston and chamber. More of the heat released will be kept in the combustion event instead of soaking out through the casting into the water.

Other ideas; higher temp thermostat and associated tuning, friction reduction, using the proper spark curve and advance, making sure the igintion parts are all up to snuff... all can make huge differences. Finding the right ride height will minimize drag too.

Singh's grooves are a way to increase quench. Its a relatively newly accepted technology despite being around a while, so the truth is hard to nail down, but the idea is simple. A Singh groove is cut into the head's quench pad. If you've ever been to the beach, you may have noticed how low spots in the sand cause a rushing variation in the water's flow back to the ocean. Cutting a groove in the heads and/or piston's quench area helps that quench just like water rushing back off the beach.

I have spent a few months really researching this, but I haven't actually tested my own "A-B" results. I'm personally putting grooves in two of my current builds, but it will be a couple months until I can post personal results.

Here are a few links for you to decide for yourself:

somender-singh.com/
speedtalk.com/forum/index.php ... go here and search for "singh" and you'll find tons of stuff.


Otherwise do an internet search for it. You'll find equal results that say its great as you do sources that say its crap... but it will at least give you both sides of the story. In a nutshell, I'm sold. At the worst you're cutting a worthless groove in a head. At best you're improving quench, MPG, detonation tolerance, and helping emissions. Its one of those things where its either "win" or "don't lose", but I encourage individual research on the subject.

[Rocketdog]

Very nice. All true from what I have experienced.

RD

[zedooo]

what do you think...how much will the compression go up if I weld up the head? in psi pls

[kliff]

I'm a dinosaur.... I lived the last few years of my mechanical life with H-D's. And with blinders on, blocked out all else. The semi-hemispherical combustion chamber was so easy to manipulate. I got lazy, and didn't follow any other theories, or even experiment, outside my world.

Keep going guys, I'm watching and learning. 'cause if'n the ole dawg can't learn something new, then maybe it is time to hang it up and retire.. EDUMICATE me.

[zedooo]

Ok, we'll try to edumicate you, Homer

Any of you atleast try to make the squish (quench) area? It helps a lot...raises the compression, makes the mix much more flammable because it turbulences it, making the gas particles much smaller, etc.
Singh grooving is supposed to enable high compression ratios with regular fuel, make the flame burst quicker and cleaner, and it's told that the machines run quieter and are able to get smaller RPM's at idle.

[Rebel]

What I got out of my reading was that this is a 50/50 thing, may or may not help. Some people say they had no improvement but others say they did. It is something to think about though.

[kliff]

Mar 4, 2010 7:16:32 GMT -5 zedooo said:

Ok, we'll try to edumicate you, Homer

Any of you atleast try to make the squish (quench) area? It helps a lot...raises the compression, makes the mix much more flammable because it turbulences it, making the gas particles much smaller, etc.
Singh grooving is supposed to enable high compression ratios with regular fuel, make the flame burst quicker and cleaner, and it's told that the machines run quieter and are able to get smaller RPM's at idle.

"Homer" huh? OK, I've been doing some reading, I'm curious. So teach this dawg some new tricks...show me. Show me your work. Teaching me, by having me read others work, and do my own experimentation. But when you call me outside my name, be ready to be the teacher, the experimentor, the man with the proof.... show me.

Most of what bI'm reading is done on "wedge" type combustion chambers. We, I'm operating with near, or semi hemispherical combustion chambers, which have always exhibited a fast flame front across the combustion chamber. NNow why would I wannna go and bugger that all up, by welding my chamber, to make a less effective wedge chamber?

When you weld a few, and show me some real world results on the GY6 type engines, I'll be all ears... till then, I'll keep working out of my cave. I "put up," I put my work to the test, show me what you can do with someone elses' ideas.

[zedooo]

nuff' said Kliff! you're absolutely right...we should try that, and then we can talk...

I called you Homer because he uses phrases like "edumicate"...

"Can you edumacate me in the ways of the saxamophone?" .)

I'm from Croatia, so my English is pretty shallow!

[Rebel]

We sometimes forget where people are and that they are not always in this country. I looked and on your first post you did let us know you were from the other side of the world. Then we use local slang and you might have a hard time understanding where it is coming from. I would never have guessed from your posts that you are not in the USA, sorry, I know to a lot of the world that would be an insult, it is not intended that way.