ESE's works engine tuner

[Kickaha]

at least TZ will be able to get the piston off the rod !

Already done that, I didn't notice the oil ring end gap when I was at your place, it's about 20mm on both of them and that piston is way more munted than mine

[TZ350]

WTF ….. The Beast screams around the track on full song then quits when taken out for an easy trot, what is that all about?????

Attachment 261714

Sounds like the standard life expectancy of a two stroke

.........



To be on the safe side we had richened the mixture up (Blue line)



And in case the piston might be to close to the head we tried an extra 0.5mm base gasket (Red Line) but we didn't like that and took it out again.

But it is interesting to see what lifting the barrel only 0.5mm does.



There is no evidence the piston was hitting the head, just a lot of derbis crushed into it. I regret we didn't lift the head for a look after the first race, then we would know for sure, but it was going so well I didn't want to disturbe it.



The original dyno graph and ignition curve.

With a straight line ignition curve the engine made max power around 16 degrees, the advanced portion improved the lower power curve. The ignition curve is 16 degrees at 12,750rpm and retads 10 degrees by 13,500 rpm for max over rev. This curve was carefully developed on the dyno using full throtle runs and took a lot of work and time.

10 degrees retard, on full throttle is that excessive? is it OK to hold it on full throtle in the max retard area at 13-14,000 rpm for longish periods? like holding out to the end of a short straight.

Any way the problems happened at lower rpm and lesser throttle openings when the motor wasn't being driven at race pace.

One small point is that in the area off the pipe, I have found that the engine will not make much if any more power, as shown by the dyno load it will pull, but by adding a heap more timing, it will for sure
operate much , much better on part throttle response, on track.
Here is a 125 kart engine curve that made 50RWHp,and won 3 back to back 125 National titles easily.

This thing would deto like mad on part throttle at 6000 if held there, but on track it would pull out of 1st gear hairpins hard enough to spin the tyres on full throttle from the same rpm, then rev out to 14200.

A TPS and a 3D map would achieve a better result, but I didnt have a RS125 Honda carb at the time.

I am wondering if this could be the problem? and I might need to use a TPS and go the 3D map way, or at least switch between 2 maps depending on rpm and throttle position.

[speedpro]

The shape of the dents in the crown suggest a bearing problem, bits of cage have been escaping. Has the ring snapped, which I think is unlikely, or has the ring location pin moved allowing it to rotate? The amount chewed away at the front suggests detonation to me but the ring has been jammed down the front of the piston going by the curved mark on the piston so possibly another problem as well.

I don't think you'll be able to sandpaper those marks out and reuse it this time.

[TZ350]

The shape of the dents in the crown suggest a bearing problem, bits of cage have been escaping.

Has the ring snapped, which I think is unlikely, or has the ring location pin moved allowing it to rotate? The amount chewed away at the front suggests detonation to me

A brg problem, I did not think so, but possible, the mains are phenolic caged, so not from there. I will have a better look at the big end brg tommorow.

A section of ring is missing, clean break, both ring ends that normaly go around the locating pin and the pin itself are still there.

[Bert]

WTF ….. The Beast screams around the track on full song for a whole lot of laps then quits when taken out for an easy trot around in the two warm up laps for the next race, what is that all about?????

Attachment 261714

Damage is in the exhaust port area, and thats a steel ring thats cleanly snapped in two....

I wander if things cooled down equally? or rather did something heat up too quick while putting around??
Was the ring gap correct for the temperature range you are working at? I've got a number of KT pistons that look similar due to incorrect ring gap settings; and ring pushing too far out into the exhaust port once things warmed up.
Could it be possible you sucked in something solid? I was amazed at the number of stones and bits sitting in the bottom of my bellypan after each outing.

I don't think you'll be able to sandpaper those marks out and reuse it this time.

Come on; a bit of devcon

[Yow Ling]

Here a bit of history on disk valve engines, yes there is a 2 stroke cosworth in there , near the bottom, the Junkers torpedo engine is pretty interesting too

http://www.douglas-self.com/MUSEUM/P...aryValveIC.htm

[TZ350]

I've got a number of KT pistons that look similar due to incorrect ring gap settings; and ring pushing too far out into the exhaust port once things warmed up.

thats possible, when the ring ends but together the ring would bulge out into the ex port.

[2T Institute]

WTF ….. The Beast screams around the track on full song for a whole lot of laps then quits when taken out for an easy trot around in the two warm up laps for the next race, what is that all about?????

That is the very essence of a highly tuned disc valve engine. There are NO easy trots, your either at 0% throttle and hard on the brakes or 100% throttle, something that long time japper riders have trouble adapting to when they ride Aprilia GP bikes.

[breezy]

it seems to make sense that at some point in manipulating the tuned lenth of the exhaust that a power gain would be achieived due to the tuning of the exhaust and barrel becoming sycronised to perform at its optimum. fabricating an exhaust to bang on dimentions to suit the barrel porting to give 100% , in the real world , must be nigh on impossible.if nothing the experiment would give a better tl measurement for which to produce an exhaust that gave 4hp more at 10000rpm than the fixed pipe it has been compared with. but it will be very interesting to see if the pipe produced gains throughout the rev range.. excellent innovation hope the fella finds a fix for the sealing problem

[SS90]

WTF ….. The Beast screams around the track

Damage is in the exhaust port area, and thats a steel ring thats cleanly snapped in two.

I will dig out the dyno graph and ignition curve.

When you get wide exhaust ports like you now have, excessive ignition retard starts to show up in my experience, it is very well documented that the exhaust side of the piston crown will super heat when the advance is too much,(an unfortunate by product of the very reason retard gives over rev in regards to pipe temp, the "passing the heat onto the pipe" is benificial for over rev,but also unfortunately this "heat" has to go through the exhaust port, and as the piston opens the port, this same flame front super heats both the port and the exhaust side of the piston crown compounded by being air cooled ) this may well be today's problem. The dyno result of the lower compression (giving a very real band width increase, albeit for a wee loss in peak is something I would consider worth investigating, given the last few results, and the fact that you are trying to increase the spread, perhaps some investigation using this "less is more" concept would be worthwhile.

[wobbly]

The one and only reason you get a destroyed piston like that is DETONATION.
And looking at the Ignition curve you have posted it is immediately obvious why the thing keeps on blowing up.
NO 2T race engine making any sort of power can take anything like the advance numbers you have except in very fast, short burst, transient testing.
If at any time you had held the engine on part throttle at 10,000 rpm in 6th gear on the dyno, then done a roll on test it would have seized instantly.

I have never seen in 30 years of dyno testing any engine making reasonable Hp that would take 22 degrees of advance at peak torque, 12200 , then 20 * at peak Hp, 12400 in this case.
You have the wrong end of the stick completely with the comment about holding the engine in the overev region.
Its safe as houses up there as its BMEP is low ( little dynamic com ) plus there is not much advance, alot of the heat energy is going into the pipe - not the piston and head .

The real issue is exactly as per the comment of mine you posted re that 125 kart engine - the edvance curve it liked when used at full throttle in the mid range,would deto its tits off when held
for any time at those low rpms, be that on part throttle for a fast corner, or slow acceleration due to corner loading.
In a kart, part throttle is very rarely seen in a corner, as they have tons of grip.In a bike you run part throttle in corners most of the time, especially in the area just under the peak torque point
and having 27* of timing at 11,000 is going to kill the thing every time unless jetted well rich.

Using fuel to cool an over advanced engine looses power big time and it is impossible to set up an ideal ignition curve on a rolling road with no instrumentation at all.
With no deto sensing or being able to track EGT plus CHT you have no idea about what is happening with a particular ignition setup at all.

You used the port timing map off the sim I did as well as the head geometry, that put the overall engine efficiency quite a bit higher, but then ignored the combustion file that had an ignition curve tailored to suit the bmep
plus the overriding fact that it is an air-cooled engine.
If you take the sim as I last ran it then do a Turbulent Model with your ignition curve,the TuMax will be thru the roof,and the program will probably scream DETO WARNING at you in the mis range.

The way to go is pointed to by the fact that the RACE box has two curves that can be used in all sorts of ways - one of which is as per Honda RS125 setup, using a shift rum sensor that has allows alot of advance
in gears 1 thru 3, then uses a retarded map in gears 4 thru 6th when the acceleration rate is alot lower.
But really you first need to get a handle on a single map, that can be used in any gear at any TPS without it destroying itself.

These issues have nothing to do with an inherent problem with the 2T engine as some are joking about - I went to the kart nationals over Easter, with over 300 entries, only one siezure of a 2T all weekend that I heard about,
and that was caused by some idiot running so low on fuel it sucked air.

[TZ350]

The one and only reason you get a destroyed piston like that is DETONATION.

And looking at the Ignition curve you have posted it is immediately obvious why the thing keeps on blowing up.

These issues have nothing to do with an inherent problem with the 2T engine.

Thanks Wob, very informative and encouraging ....

[richban]

With no deto sensing or being able to track EGT plus CHT you have no idea about what is happening with a particular ignition setup at all.

Sort of what I was thinking. Maybe give Andrew a call and see if he can tell you where he got his fancy headphone setup. When I was playing with the igntech on the dyno with FXR it was really easy to hear the detonation with the phones. Might even be easy to make. After playing around at the track trying to jet the FCR I am sold on some actual diagnostics. Was going the wrong way. It wanted leaning not richness. As we are also pushing the limits of an air cooled single I am making a header with a lambda and EGT setup. Blow ups are expensive and really I would rather be racing than swinging a spanner. Maybe marking your throttle with about 10 positions and try loading and listening for det at each poz should give you a good idea of how the carb and ignition are working together. I had a small manifold leak when I was work with the headphones was very obvious something was wrong.

Onwards and upwards mate.

[TZ350]

The text of an email I received from Neels van Niekerk and posted here with his permission.



Hi Robert

I know it has nothing to do with me but if the engine that broke the ring this past weekend was running the attached export it is no wonder. My experiences with these size exports are the following:

1. Never exceed 41mm for your bore ( *** )
2. Use at least 10mm radius for top corners
3. Use 100mm top edge radius
4. use 12mm radius for bottom corners
5. Use 80mm radius for bottom edge

Exceeding these gave more power but lead to the following:
1. Unexplained seizures
2. Broken rings after cooling off at the end of a race - runs fine and wins race, refuses to restart
3. Pinched rings - from severe hammering of piston top edge
4. Broken ring land at export
5. Ring breaks at low speed - not sure why but I think it just have more time to bulge into the export

If the only way to be competitive is to run such a port:
1. Piston and ring life is max 50km
2. Bore must be perfect
3. Very good (rounded) chamfer of top and bottom edge

I really like reading your ESE thread - gives me good feedback about where to improve my software and it is great to see such an enthusiastic bunch.

Regards
Neels

*** 56mm was the bore size enterd into the simulator.

[wobbly]

Rob, I thought you have been running that Ex width for a while with no issues ( it was in your original sim file ) - but I have never gone over 72% except in small bore sizes that seem to be able to keep the ring life OK.
Looks like it could now be a combination of too high bmep for the ignition that was OK before, and same with the Ex width, that cant be sustained now its starting to see some serious revs.

Running egt and cht you can watch both rise in unison as the rpm and power rise.
As soon as deto starts the cht will shoot up, the egt will flat line or drop as radicals are formed in combustion.
The best data logging gauge ( and the ONLY reliable egt probes ) are here.

http://www.exhaustgas.com/ProductDet...sketID=&RepID=