ESE's works engine tuner

[breezy]

this is an open question to the forum,if there were no end gases, would this eliminate detonation? if you were able to ignite end gases within the squish area first then send multiple flame fronts out of the squish area into the fuel air mixture held in the combustion chamber rather than from a single spark from the traditional plug position, would this help, or would end gases still form else where ?

[oldjohnno]

this is an open question to the forum,if there were no end gases, would this eliminate detonation? if you were able to ignite end gases within the squish area first then send multiple flame fronts out of the squish area into the fuel air mixture held in the combustion chamber rather than from a single spark from the traditional plug position, would this help, or would end gases still form else where ?

I think it might just be a matter of nomenclature - if you were to ignite the outer ring of gases first then these would no longer be the end gases. That title would now belong to the contents of the chamber bowl, and I guess that as they are now subjected to the heat and pressure of the surrounding burn then they would be pushed towards detonation, just as the outer ring of gas was when the roles were reversed. There'd also be the effect of quench on the part of the charge that you're trying to light and I assume that this would lengthen the total burn time.

'Course I've been wrong a few thousand times before...

[ken seeber]

But Jan has also stated that the optimum down angle of the roof he tested was 25*.
Maybe increasing this,along with lowering the floor at the port exit could be "better ".
Maybe I can get to try this idea with Franco at TM - the roof change would be easily done by scraping the core,but a hollow floor
would need a CAD change, not as easy.
Fear not, I want to do it.

Haveth no fear Wob. Just as you can rub the core (ie remove sand = more metal) you can just/nearly as easily add sand and remove metal for the floor. The foundry guys can easily add sand to the core, whether it be CO2 or shell core. Just lump on the extra sand and either gas it more or rebake, even with a gas torch. Would take some hand finishing, and possible some core coat to get a decent finish, but for a one off, you'd be in there with a die grinder anyway. Might have to also rub the water jacket core to clear the lump though. If it works, then Solidworks.

[ief]

Oke, this is on the other end of the spectrum but I guess that shouldn't mather, it's doing me head in just the same

Starting out with a highly undertuned 2 stroke, went on my way and (asumingly) improved the intake side, carb, intake, piston and inflow of the transfers and polished the exhaust. In other words, not much.

Now the problem arose that it starts to 'grind' at peak (sounds unhealthy and feels like the engine is working against itself.)

My assumption is/ was that peak pressure on the piston was to early due to to hot temp (???)

I' have tried, jetting, different head (less comp), different exhausts and now finally gave it some more blowdown area.

Still there, it changes from where it is rev wise and how severe but...

It seems to go away when the weather is colder, that is none conclusive but think that's the case.

Now I'm wondering, could it be due to something mechanical? (thinking piston clearance?)

Does that make sense?

[adegnes]

Oke, this is on the other end of the spectrum but I guess that shouldn't mather, it's doing me head in just the same

Starting out with a highly undertuned 2 stroke, went on my way and (asumingly) improved the intake side, carb, intake, piston and inflow of the transfers and polished the exhaust. In other words, not much.

Now the problem arose that it starts to 'grind' at peak (sounds unhealthy and feels like the engine is working against itself.)

My assumption is/ was that peak pressure on the piston was to early due to to hot temp (???)

I' have tried, jetting, different head (less comp), different exhausts and now finally gave it some more blowdown area.

Still there, it changes from where it is rev wise and how severe but...

It seems to go away when the weather is colder, that is none conclusive but think that's the case.

Now I'm wondering, could it be due to something mechanical? (thinking piston clearance?)

Does that make sense?

Could you make a video of the behavior and upload it to YouTube or similar?

[ief]

Not in a way that would be helpfull I'm afraid.

But anyone who has had it will know what I mean by 'grinding' really can't find a better word for it, not even in dutch, haha.

You feel the bike start vibrating a litlle more, engine sound changes, power doesn't seem to be affected much (seat of pants) but it runs, feels and sounds 'raw/ rough' sometimes it spans 500 revs, sometimes 1000, given setup and I think more importantly, weather condition or a combination of those 2.

I thought perhaps to big a piston clearance might 'emphasize' the problem (not the word I'm looking for)

[F5 Dave]

Replace the clapped out engine mount rubbers.

[ief]

If it had any

[wobbly]

IEF, sounds just like the onset of deto.
Bolt a Bosch sensor to the head and fit a flashy lighty thing.
http://www.ebay.com/itm/Knock-gauge-...-/182186510011

Re removing the end gases to stop deto, thats exactly what the italian kart engine makers do.
They have a tiny width of highly divergent angle in the head - so no trapping = no deto.
The real problem though is the straight line ignition, the engine simply doesnt need extra combustion turbulence induced by squish velocity
to increase the burn speed, as there is way too much advance anyway.
But there is a way to fix the issue, and it will be the first dyno run I do at TM when I arrive - if I ever get there, as American Airlines have cancelled a flight due to an A380
not being delivered in time.

[breezy]

IEF, sounds just like the onset of deto.
Bolt a Bosch sensor to the head and fit a flashy lighty thing.
http://www.ebay.com/itm/Knock-gauge-...-/182186510011

Re removing the end gases to stop deto, thats exactly what the italian kart engine makers do.
They have a tiny width of highly divergent angle in the head - so no trapping = no deto.
The real problem though is the straight line ignition, the engine simply doesnt need extra combustion turbulence induced by squish velocity
to increase the burn speed, as there is way too much advance anyway.
But there is a way to fix the issue, and it will be the first dyno run I do at TM when I arrive - if I ever get there, as American Airlines have cancelled a flight due to an A380
not being delivered in time.

i was thinking of electrically isolating the cylinder head from the barrel (anode) and the piston being the cathode and the squish gap being the electrode gap.... suppose spark errosion of an" alloy" piston could be a problem

[Frits Overmars]

i was thinking of electrically isolating the cylinder head from the barrel (anode) and the piston being the cathode and the squish gap being the electrode gap.... suppose spark errosion of an" alloy" piston could be a problem

SAAB tried something like that, combining a spark plug without earth strap with a spike on the piston.
But never mind the electro-erosion of the piston; think of the current's path through the con rod bearings!

[TZ350]

But anyone who has had it will know what I mean by 'grinding' really can't find a better word for it, not even in dutch, haha.

I thought perhaps to big a piston clearance might 'emphasize' the problem (not the word I'm looking for)

Try ... "exacerbate the problem". I know what you mean, when it runs sweet it is really sweet then there is a hint of rough, not so sweet but still good and changes make it feel/seem rougher, harsher but it still pulls good numbers on the dyno ....

[TZ350]

Tz , what kind of radiator are You using and did You measured the water temp?

Not sure, but I think the radiator was from a hot sports 250 4T road bike, anyway it was $20 on TradeMe. Water temp around 45 deg C. I have to be careful to not have the dyno fans blow directly onto the radiator. The water pump is a 25 L/min unit and the bike dynos at about 27 rwhp.

The head temperature as measured under the plug and goes from 37 deg C with the fans full on to 67 deg C no fans. My air cooler ran 90+ deg C with the fans on.

[TZ350]

Changed the rotary valve, didn't carefully check the timing but estimate it to be, opens 140 btdc closes 70 atdc. I will have to put a timing wheel on it but I expect the numbers are in the ballpark.

Tried a thinner disk too, as the old one had minimal clearance and was showing signs of rubbing. Also tried running with a carb, one that had worked well for me on the air cooler. I expected more power because the RV was not so tight in the case and as well I had pulled 32 rwhp on the air cooler with this carb before so was expecting some improvement over the water coolers 27.

The results were very disappointing, this was my favorite carb and I could not get it dialled in and it ran like a bag of pooo, down on power and rat shit everywhere. Ugly, ugly looking curves and it even had the dreaded top end flat spot I was getting with the fuel injection. Also the gearbox oil pump had stopped working and I had started to burn the clutch.

Time to carefully look at, and measure everything.

[Tim Ey]

@ief:
You are not running a mechanical ignition, or? Got the same "grinding" on my Zündapp C50 when the contact is comming to its resonant frequency