How are ya Jeff. I was going to ask you what inprovements you would find with your Stage 2- 7.2, for 66cc GT5. I've got now on 66cc Puch hihi, with Arrow reed. Is there a pretty big variation between the two? Would a person really see that much difference?
grinningremlin
Active Member
Fred, just let your products speak for themselves, you BOTH are standing on the shoulders of giants and didn't invent anything (as far as I can see), so calm the f.u.c.k. down.Anyone who needs to tout their righteousness is gonna be bit in the a.s.s. by his own complex someday, so take it easy, we're all fallible.
Also remember, some cool things have come from people experimenting not having a clue what they are doing, just saying.
Also remember, some cool things have come from people experimenting not having a clue what they are doing, just saying.
HeadSmess
Well-Known Member
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in between socialising and other errands, and ignoring this thread, i been drawing...
6mm between fins cus thats the best endmill for alloy i got... wonder if it can get to 24 deep? doubt it. whatever!
very hard to see but i learnt how to draw hemispheres on google sketchup. neat
learn something new everyday, thats the key.
no idea what grade alloy it is that i got but im gunna use it. even comes with a 10mm hole ...
a little bit of maths and im sure i could calculate the volume...lets see now...4/3piR^2 isnt it? i learnt that in 5th grade! so. 25mm sphere. erm...6.5 cc? um. so half is 3.25. nasty. i need a bigger hemisphere 30mm is about 4.7. nicer a true 48 cc swept volume and tight squish would gimme 11:1 with that, roughly...
raising chamber to 35mm is around 6.4cc as i see it, or ideal. this is not including any space in the plug, etc. just a true hemisphere. at which point the squish band is down to 2.5mm... doesnt really seem worthwhile, does it?
but then that silly 11:1 ratio is swept... not from exhaust closing times.
best way is to start small and machine it bigger i guess... unfortunately plug depth is sorta set by size of dome... i didna think of that when i was drawing away...
whats harder is MACHINING the freaking hemisphere... i havent got cnc lathe i do have a section of rack and mating gear, and some lumps of steel. i can get this to work i needs a pivoting tool post driven by the grumpyslide
once again, can we stop acting like little kids and just talk about practical considerations?
would anyone be interested in a watercooled head?
6mm between fins cus thats the best endmill for alloy i got... wonder if it can get to 24 deep? doubt it. whatever!
very hard to see but i learnt how to draw hemispheres on google sketchup. neat
learn something new everyday, thats the key.no idea what grade alloy it is that i got but im gunna use it. even comes with a 10mm hole
...a little bit of maths and im sure i could calculate the volume...lets see now...4/3piR^2 isnt it? i learnt that in 5th grade! so. 25mm sphere. erm...6.5 cc? um. so half is 3.25. nasty. i need a bigger hemisphere
30mm is about 4.7. nicer a true 48 cc swept volume and tight squish would gimme 11:1 with that, roughly... raising chamber to 35mm is around 6.4cc as i see it, or ideal. this is not including any space in the plug, etc. just a true hemisphere. at which point the squish band is down to 2.5mm... doesnt really seem worthwhile, does it?
but then that silly 11:1 ratio is swept... not from exhaust closing times.
best way is to start small and machine it bigger i guess... unfortunately plug depth is sorta set by size of dome... i didna think of that when i was drawing away...
whats harder is MACHINING the freaking hemisphere... i havent got cnc lathe
i do have a section of rack and mating gear, and some lumps of steel. i can get this to work i needs a pivoting tool post driven by the grumpyslide once again, can we stop acting like little kids and just talk about practical considerations?
would anyone be interested in a watercooled head?
Last edited:
grinningremlin
Active Member
If it's not instantly applied/adjusted/improvised math (i.e. music), it might as well be 5th grade Greek to me.A water cooled head would be cool, but wouldn't you be getting into weight vs. horsepower problems if it came to fruition?Couldn't you do a fan based air-cooler like the utility engines we use (tanaka/RS/honda) with better results/ less weight? Just always been curious about these mini motorcycle engines sitting idle and how much they must heat up without airflow, another reason I steered clear of them.Remember, I'm a rider, not a machinist/engine guy, be kind.
crmachineman
Member
Umm, were you asking me? It sounded like it. My name is Fred though.
You know, I'm really not sure what improvement, if any you would get. I don't know what the combustion chamber of that head is. And there are other things that will affect performance; you mentioned the GT-5 motor; that particular motor has a problem when it comes to utilizing the squish band.
The fins of the Puch head are not oriented right. Other than looks, I'm not sure what performance difference that would make.
Now, talking about the GT-5 engine, I sell top end kits for them.
This is really important, because for some reason, with the GT-5 engines, the piston stops 2mm short from reaching the top of the cylinder when it's at TDC.
So, in my GT-5 kits, it comes with a modified cylinder body which has been decked so the piston can come flush to the top of the cylinder.
There is more to consider: You can get the top end kits in a stage 1 or stage 2 version.
The stage 1 version is cheap. I charge very little for the cylinder body because I only do a small amount of hand work on the transfers, and I deck the cylinder body. It has a stock steel intake manifold.
The stage 2 version is a lot more. Those have enlarged intake and exhaust ports. The port shape has also been altered to optimize the port timing for significantly better performance.
The cylinder body is also fitted and port matched with my special intake plenum. It is available in 19, 23, 24mm spigot diameters. I am very happy with the results of this intake design.
There is even more to consider:
Lastly, when you order one the top end kits from my website, you can choose from 3 different combustion chamber sizes.
The reason for this is to allow you to maximize the compression (and efficiency) for whatever your engine configuration will be.
For example, if you purchased the stage 2 kit, and wanted to run a simple stock exhaust, I would say the best choice would be the 6.0cc combustion chamber.
With this recipe, you could use normal pump fuel and have excellent power and reliability.
On the other hand, if you want to use the engine with a good expansion chamber style exhaust system and run normal pump fuel, use the 7.2cc combustion chamber.
Of course, if you plan to run race fuel, then you can safely increase the compression further.
Oh, and one more thing. The kits come with special modified pistons which tweak the port timing for better performance.
-Fred
D
Deleted member 12676
Guest
Rich Rohrich, the genius who contributes at the Dirtrider forum wrote in response to my request for info on engines without a squish band:
"If memory serves correctly Morbidelli built some of their GP 125 engines without a squish band. I don't recall exactly but I think it was sometime in the middle 70s."
Fred, of course your heads offer improvement. I did not start this thread attacking your heads (like you attack my CDI), I was mearly stating my opinion about squish bands in relation to putt-putt engines. Your heads offer a small percentage of power increase due to the compression increase. If the increase is above 140 psi and/or the engine is ported for 9000rpm or more then the squish band is necessary. Otherwise it is the equivalent of putting legs on a snake. unecessary. Not decidedly detrimental though. That depends on various factors.
"If memory serves correctly Morbidelli built some of their GP 125 engines without a squish band. I don't recall exactly but I think it was sometime in the middle 70s."
Fred, of course your heads offer improvement. I did not start this thread attacking your heads (like you attack my CDI), I was mearly stating my opinion about squish bands in relation to putt-putt engines. Your heads offer a small percentage of power increase due to the compression increase. If the increase is above 140 psi and/or the engine is ported for 9000rpm or more then the squish band is necessary. Otherwise it is the equivalent of putting legs on a snake. unecessary. Not decidedly detrimental though. That depends on various factors.
That is the opposite of what you need.Quiescent combustion chambers were abandoned long ago.You need the squish at any rpm range not just high speed.The MOPAR Hemis were notorious for detonation and needing ridiculous spark advance.
Marine two strokes that operate under 6000 rpm have a much researched and very refined squishband.
crmachineman
Member
Ahh yes.
Old Bob what you said correlates with the results of my, and pretty much everyone who gets one of my heads, provided that the squish clearance is not excessive.
The best thing is that not only can performance can go way up, depending on exhaust and how well you build the engine, but also the reliability of the engine is greatly increased.
Loss of power and damage to the engine is often caused by detonation and the resultant heat from it. The Fred heads deal with that by increased cooling and combustion chamber design.
My test engines never even see much past 7,000 RPM. Early when I started working on these engines they used to top out at around 5-6000 RPM. I too have noticed improvement throughout the power band.
-Fred
Old Bob what you said correlates with the results of my, and pretty much everyone who gets one of my heads, provided that the squish clearance is not excessive.
The best thing is that not only can performance can go way up, depending on exhaust and how well you build the engine, but also the reliability of the engine is greatly increased.
Loss of power and damage to the engine is often caused by detonation and the resultant heat from it. The Fred heads deal with that by increased cooling and combustion chamber design.
My test engines never even see much past 7,000 RPM. Early when I started working on these engines they used to top out at around 5-6000 RPM. I too have noticed improvement throughout the power band.
-Fred
Fabian
Well-Known Member
Fred, i have sent you a PM on the availability and possibility of having the low compression head manufactured with 6mm head stud holes.
I have not heard back from you via a PM or via this thread?
Why?
I have not heard back from you via a PM or via this thread?
Why?
crmachineman
Member
Hi Fabian
Hmm. Well I don't know what happened. I did get that PM from you and I wrote you a response. Sounds like it didn't make it to you though. Oh, yeah, you want one for the 6mm studs. Ouch! I'm not tooled to make them for 6mm studs because they are not very common. Of course I could do it, but it would cost like $50 more, and it wouldn't come with the special extra tall nuts! I'm curious, why do you want to stick with the 6mm studs?
-Fred
Hmm. Well I don't know what happened. I did get that PM from you and I wrote you a response. Sounds like it didn't make it to you though. Oh, yeah, you want one for the 6mm studs. Ouch! I'm not tooled to make them for 6mm studs because they are not very common. Of course I could do it, but it would cost like $50 more, and it wouldn't come with the special extra tall nuts! I'm curious, why do you want to stick with the 6mm studs?
-Fred
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