ESE's works engine tuner

[twotempi]

A mere flesh wound ??

[TZ350]

A mere flesh wound ??

Yes a mere flesh wound ...... up and running in no time.

[Frits Overmars]

If the rod was of infinite length the big-end bearing would constantly rotate at half crankshaft speed

So the small end would sweep around at the other half of the crankshaft speed? I hope not...
OK, the big end bearing cage would constantly rotate at half crankshaft speed. Which is a good thing.

So do longer rods have a significant benefit for the big-end bearing ??

Yes. Long rods may be heavier, but load is not what kills a big end. It's the rotation speed fluctuation and the crowding of the needles towards the outer side af the crank that cause skidding, friction, heat, destruction of the oil and same of the bearing.

[bucketracer]

Maximum output of a 50cc engine using "todays technology"!



The expert:
"The best horsepower we attained at Aprilia last year (2007 125cc GP) was 53,9 HP at 13000 rpm. This means a Pme of 14.88 at a piston speed of 23,6 m/sec. Using these same values means that a single cilinder 50cc would give 29.5 HP at 17850 rpm and a 50cc twin would give 39 HP at 23600 rpm, measured at the gearbox output shaft. I am 100% sure these values can be attained although it never will be proved due to lack of interest and money. Remember that 50cc development was stopped in 1983 and enormous progress was made in the following 24 years. Now, sadly, also the development of the 125cc two strokes has stopped, the two stroke will only survive in karting but there will be no progress because of the very strict regulations!"
Jan Thiel 2008

http://www.elsberg-tuning.dk/engineering.html#theengine

[Frits Overmars]

Oooops no plug ... I was sure it had plenty of compression at Taupo, anyway got a comp tester onto it ....

Attachment 260438
I hope you didn't measure the compression with the plug cap lying around like this; that would be a great way to fry the ignition. If the high tension cannot find a way out via the plug gap, it will create its own shortcut escape route inside the ignition unit.
Every engine I work at has a protruding M6 bolt somewhere, where I park the plug cap every time it is not on the plug.

[bucketracer]

Attachment 260438Every engine I work at has a protruding M6 bolt somewhere, where I park the plug cap every time it is not on the plug.

Good idea ..... thanks.

[SS90]

Gave that one back to Mike, I guess I didn't put another one in for the trip home.

[ATTACH=CONFIG]260446

There is the naughty little sausage, with the ring jammed at the exhaust port.

This must have happened in practice when it seized, amazing the thing ran so well in qualifying, it was still doing a good turn of speed and zipping most things in sight, I guess it just didnt want to go back out there for the main event.

From the looks of the first image, it looks like there are witness marks on the crown (sharp edges), suggesting the piston was touching the head, causing the ring to jam.

Any chance that was the culprit?

[TZ350]

Attachment 260438
I hope you didn't measure the compression with the plug cap lying around like this; that would be a great way to fry the ignition. If the high tension cannot find a way out via the plug gap, it will create its own shortcut escape route inside the ignition unit.
Every engine I work at has a protruding M6 bolt somewhere, where I park the plug cap every time it is not on the plug.

No I didn't comp test it like that but did give it a vigorous shove trying to start it before realising, lets hope that there is a zenor or some sort of clamp set up that limits the maximum voltage that can be applied across the internal CDI circuitry by the back EMF of the coil. I like the stud idea and will fit one.

[wobbly]

The only things that fry these digital CDI units is input overvoltage, caused usually by idiots that run a regulator direct into the ECU with no battery or capacitor load.
I got Ignitech to stop this with a Zener and detector circuit that shuts the ECU down.
But the second death of spinning the motor over without a plug, it is very difficult to prevent damage almost instantly with around 40K running around looking for a random earth - it
usually finds it thru the side of the CDI cap.

[marsheng]

Just found this - BEMP figures !!!!

'Here in Brazil our preferred engine for drag racing is the VW ABA 4cyl 2.0 Liters and I've got 1180 Hp on this little sport compact machine with just 3.6 bar intake pressure.'

Well maybe it's time to revisit a 100cc and supercharger.

[wobbly]

Shit - ONLY 54 lbs of boost, I can fart harder than that.

[Yow Ling]

Just found this - BEMP figures !!!!

'Here in Brazil our preferred engine for drag racing is the VW ABA 4cyl 2.0 Liters and I've got 1180 Hp on this little sport compact machine with just 3.6 bar intake pressure.'

Well maybe it's time to revisit a 100cc and supercharger.

Good idea, that should keep you busy for a while !

[TZ350]

The sized piston from the Taupo GP.



On over rev, close but not touching.



Not so hot that it has coloured the underside of the piston crown, so not overheated. My pick is it needs a touch more clearance.



I think that the top edge and ring grove have been pushed up by the lower edge of the exhaust port, or hammered in as the piston rockes over and slaps the cylinder wall.



The Honda RS piston shows some of the same signs too.



This new Yamaha 90-93 YZ125 piston has a grove under the ring land. Whether that is to over come the ring jamming problem or for something else I am not sure.

[husaberg]

Just found this - BEMP figures !!!!

'Here in Brazil our preferred engine for drag racing is the VW ABA 4cyl 2.0 Liters and I've got 1180 Hp on this little sport compact machine with just 3.6 bar intake pressure.'

Well maybe it's time to revisit a 100cc and supercharger.

I bar 14.7 psi as Wob said 53psi not a problem unless Avgas is the fuel and inlet temps are anything that would be expected normal.
22psi could happen with an approx 6.5:1 comp ratio though a realistic figure for Avgas and efficient intercooling water injection and a Rootes blower. More boost possible with screw or centrifugal charger.(they don't heat the charge so much) But they wont offer such a linear boost to revs curve. ie they offer less down low too much up high.
If you seriously want to have a go i have 2x donor engines here (FZR250's) you can play with for what i paid for them.
If it could be engineered to stay together 40-45HP could happen, given enough time skill and and $.

In hindsight maybe the 50mm Cr80 piston has a lower pin than the nsr125 as well so maybe a couple of mm there too, to be gained.

Having a longer rod ratio - say the Aprilia at 2.2 - will decrease the difference of rotational speeds of the big-end bearing between TDC-Half Stroke-BTDC.

Example - If the rod was of infinite length the big-end bearing would constantly rotate at half crankshaft speed

So do longer rods have a significant benefit for the big-end bearing ??

Unfortunately my budget won't stretch to an infinitely long rod either.

But i did find the odd extra long one but with a 24mm pin as Wob said lots of 20mm pin ones go to 110mm But not sure how to accomidate without scewing up the rest of the engine clearances i would have thought around 106-108 would be easily doable though as well as allowing for the decrease in stroke. But wob will know how to fit them in and still make it work i guess.
I assume the decrease in stroke will make the port timing more racy and the Longer rod will increase the port time area as well?

In hindsight maybe the 50mm Wiseco CR80 piston has a higher placed gudgeon pin? so maybe a couple of mill there as well?

[speedpro]