ESE's works engine tuner

[ken seeber]

Wobbly,

I have attached a pic of an LKE KZ head insert. Its design and damage leads to a few questions:

1. The squish area is very low at 32% (44.5 inside diameter of band), it has a strange radius return just inside the squish band and the actual bowl is relatively flat topped. Other KZ engines are similar. This is in contrast to the sketch you did a few days ago of the toroidal shape. Is there something different required to karts over bikes or is this the latest good thing?

2. Compression volume. Typically "as supplied" KZ engines are well over the minimum CC method of measurement used in Oz, possibly by around 1.5 CC or so. Given that, there are the options to reduce the volume. One being to just face the original insert, sticking with the shape. The next is goingto a totally new toroidal design (along the lines of your sketch), but the trade off here is that the volume in thetoroid above the bottom face of theplug boss will capture air during the measuring, thereby giving a lower CC reading than is actually the case, minimizing the possible CC reduction. However, it might turn out better to have a good shape with a larger volume than a CC measurement that is on the minimum allowed. Hope this makes sense. The other option is just to do nothing because there might be nothing to be gained and for the question below

3. Detonation damage. The majority of this is above the B & C ports, not the exhaust side. The piston was similarly damaged. This damage is not unique to just this engine. One would think that the piston crown adjacent to the exhaust would be hotter, thereby making that side more susceptible to detonation. One thought is that above the exhaust there might be end gas which might slow down the combustion rate in this area, hence less damage. However the opposite may be the case. It might also be that the volume is small enough such that it would be unwise to reduce the CCs further, given the 98 octane fuel requirement.

Thanks

Ken

[ken seeber]

here it is

[F5 Dave]

That is queer, you usually see damage either direct centre of piston or ex port edge taking off the sharp edge of the crown. It would be interesting to know what revs & throttle position with a det sensor & data logger to see when it is happening beyond normal running of a racebike perhaps? (I don't even know if this engine is fixed gear or not) With the insert and the sealing arrangement if there was a leak at some point in that area? There is a shiny area & a dull one so we can ignore the garks I guess?

Interested to see what Wob thinks, I'm just cluelessly speeling filling in time

[wobbly]

A very easy question to answer.
The KZ2 ignition is virtually a straight line, thus the static you set it to is what you get.
Thus the pipes are very short to enable the engine to rev 14000 + as the ignition timing is way too advanced at high rpm to dump heat into the pipe
as would normally be the case with any sort of digital or simple analogue retarding setup.
In these engines we are fighting this excessive advance all the time, and many factors must be looked at to get a good working setup that wont detonate
but of course make the best power.
Biggest issue is that the end gases trapped in the squishband will deto the instant you run a little lean, or have too much static wound in.
The key to understanding whats going on is to realise why it always happens opposite the Ex.
This is due to the direction of rotation, as the piston rocks over TDC the inlet side is momentarily the closest to the head.
I have tried all the many combinations of cc, squish and chamber shape and as im in a good mood I will give you some of the detail.
Get the chamber down to 13.2cc thus leaving a little for safety sake with Tech officers not so clever at using a burrette, this pumps up the power needed at 9000
to get off the mostly 2nd gear slowest hairpins.
The minimum squish at the bore edge can be no less than 1.3mm, with the band tapering away from the piston at least another 0.2mm.
It must have a sharp edge into the bowl, and cut away the roof ( as well as making it as flat - bathtub - as you can ) so that the plug is just legally below this surface.
You must run a R7376-10 fine wire plug and NOT a resistor cap.
Every engine is different and the combination of 13.2cc and the static timing is what will give the balance between mid power punch and straight out rev on ability.
I have run anything from 1.1 to 1.7mm, and the only way to determine what is best,is to ensure always to jet it so it never exceeds 620*C and run it on a dyno to see what it likes.
Track testing to do this is very hard on gear, and thus even more expensive than getting onto a dyno.
The problem with the testing is to keep the jetting under control, and look at the data/talk to the driver to see what is the best tradeoff between having good bottom
combined with plenty of revon.
The relationship is almost linear - as you wind in advance the mid pumps up - and the overev drops.
Trick is to only do short runs, and always use a bendy torch every run to watch the inlet squish side of the piston to see the shiny surface "just" starting to turn grey.
I will take a pic in the morning of Hamiltons national title winning engines piston that is on my dyno now.
That is absolutely on the edge,after running the qual,heats and final.
You will NOT get away with a toroid in NZ - I understand that a tuner in Europe is doing this, and wants his engines held on some super critical angle
to check the cc, but yes I have asked and no its not permitted here - makes no odds to me anyway as we kicked the World Cup winning Savard TecSav engines arse - toroid or no toroid I dont know.

[ken seeber]

Jeez Wobbly, I'm glad you were/are in a good mood.

Lots of usful info for the dudes over here, inc myself, to get our minds around.

So, if we ask you more questions , you'll be in a good mood more often. Everyone wins !!

However, I won't go as far as demonstrating a " 125 Aircooled with 24mm carb making 30 Hp at 10500", despie the rewards.

Cheers

Ken

[marsheng]

Ok this is way out there, but we spend hours getting into those tiny little transfer ports with all sorts of tools to get the right shapes.

What if we bored out the cylinder 10 or so mm and made new aly sleeve to fit inside. That way we could do all the porting on the aly sleeve possibly complete with cast iron liner then drop the whole lot back into the barrel. The top of the sleeve can have a ridge on it to stop it falling through and the bottom could be welded to the to the barrel bottom to keep it all strong.

As most barrels are quite porous the new solid aly sleeve would probably help quite a lot with heat transfer. The only issue that I can see is the exhaust bridge being '2' parts.

Comments ?
'

[wobbly]

Been there done that - forget having an ally sleeve AND a cast one, too many disruptions to the heat path.
As you say, big overbore, cut the sleeve, press it in and then weld it in at the top for the best heat transfer in the hottest area, and weld the transfer ducts
to the sleeve for retention.
Then get it plated.
I believe you have to use 6061 ally and special rods if the weld is to be covered by the Nicasil.

[marsheng]

Sounds an interesting option. Do you weld the transfer port dividers ? Will be hard to get in there.

Not sure if you heard, my Maico Barrel expired, started to split around a base bolt hole. Did 6 or so laps.

Cheers Wallace

[peewee]

hey wobbly or anyone else. ive seen what happens with insufficient blowdown. is there such a thing as too much blowdown ?

[wobbly]

Its not so much the issue of too much blowdown per se in an engine spec.
The real issue is how did the excess blowdown for the planned Hp/rpm actually occur.
Using a CAD program it is easy to see a mismatch between the STA numbers for any combination of port area and timing.
If for example we see really big numbers for the EX and Bl STA but a mismatched small Tr STA then the performance will be transfer limited - and we wont see the power as the BL STA would predict..
Go the other way and we can have big Tr STA and big Bl STA, and this in fact may not be an issue, as in many cases having the TR and Bl correct, but an undersize Ex STA
will just mean that a clever person has filled in the EX floor and the bottom corner rads to reduce short circuiting.
This scenario will perform as per the correct BL and TR STA numbers predict.
What I was going on about the other day was to point out that taking a cylinder with low Tr and low Ex timings and simply jacking it up, will for sure give a useful improvement.
Simply due to the better timing numbers suited to alot more performance, but having huge 130* transfers and a relatively low 192* Ex points to the engine then being BL STA limited.
Drop the cylinder and grind up the Ex to get all 3 STA numbers complementing each other,and more power than the simple jack up scenario is a given.
Here are the STA numbers for an Athena 50 - one with the cylinder jacked up, the other with the same transfers but the Ex ground up to match.

[wobbly]

And here is the pic of the TM125 piston.
This has done 3 hard days testing, qualifying, 3 heats and a 25 lap final.
When you are this close to the edge one thing many dont realise is the following.
Always buy fresh fuel from the most popular gas station in town, that has regular tank topups.
NEVER leave fuel sitting overnight in the kart tank and use it the next day, and dont buy 20L at a time and only use 1/2 of it
during a test day, then use the other 1/2 the next day, with the fuel sitting in a 1/2 empty container overnight.
When you open a tin and hear the " whisssh " of pressure escaping the lid, all that "vapour pressure " is exactly that.
The light front ends of the fuel that are easy to emulsify as a fine mist and burn efficiently in the chamber, have all collected as vapour pressure in the can, or escaped out of the kart tank into thin air.
What is left is denatured ,crap, low octain, slow burning piston killing deto juice.
When heavy, large drops of fuel with little or no light fractions enter the combustion process, alot of this isnt burned, the molecule collections are simply to big to consume in time.
This shows as a "rich " mixture, so of course we lean that sucker down to get some temp into the pipe and bugger, it detoed its tits off.
Nothing to do with the jetting or the timing, its bad fuel from simply being left overnight in a tin or tank.

[peewee]

wobbly you might get a chuckle from this one. its alittle lopp sided but i didnt know any better at the time. one of the problems i had was the cylinder casting was pretty thin at aux exh ports which limited how large they could be (ill probly cut the side of the cylinder off and weld them next time). with a lack of exh area i tried to compensate by raising the main exh which threw the blowdown out of wack. ive got another cylinder so i can give it another go. ill fiddle with engmod and try to get the numbers looking alittle better for next time. im not sure what more i can do with the reed cage. i cut out some of the dividers which increased the tip area by 10mm (if i recall correct) which was equivalent to adding another petal.

[pete376403]

And here is the pic of the TM125 piston.
This has done 3 hard days testing, qualifying, 3 heats and a 25 lap final.
When you are this close to the edge one thing many dont realise is the following.
Always buy fresh fuel from the most popular gas station in town, that has regular tank topups.
NEVER leave fuel sitting overnight in the kart tank and use it the next day, and dont buy 20L at a time and only use 1/2 of it
during a test day, then use the other 1/2 the next day, with the fuel sitting in a 1/2 empty container overnight.
When you open a tin and hear the " whisssh " of pressure escaping the lid, all that "vapour pressure " is exactly that.
The light front ends of the fuel that are easy to emulsify as a fine mist and burn efficiently in the chamber, have all collected as vapour pressure in the can, or escaped out of the kart tank into thin air.
What is left is denatured ,crap, low octain, slow burning piston killing deto juice.
When heavy, large drops of fuel with little or no light fractions enter the combustion process, alot of this isnt burned, the molecule collections are simply to big to consume in time.
This shows as a "rich " mixture, so of course we lean that sucker down to get some temp into the pipe and bugger, it detoed its tits off.
Nothing to do with the jetting or the timing, its bad fuel from simply being left overnight in a tin or tank.

The markings in the top of the piston (makers name, size, etc) "look" like little dimples/pinpricks with sharp edges. If they are, would that have any effect on detonation?

[F5 Dave]

And here is the pic of the TM125 piston.
This has done 3 hard days testing, qualifying, 3 heats and a 25 lap final.
When you are this close to the edge one thing many dont realise is the following.
Always buy fresh fuel from the most popular gas station in town, that has regular tank topups.
NEVER leave fuel sitting overnight in the kart tank and use it the next day, and dont buy 20L at a time and only use 1/2 of it
during a test day, then use the other 1/2 the next day, with the fuel sitting in a 1/2 empty container overnight.
When you open a tin and hear the " whisssh " of pressure escaping the lid, all that "vapour pressure " is exactly that.
The light front ends of the fuel that are easy to emulsify as a fine mist and burn efficiently in the chamber, have all collected as vapour pressure in the can, or escaped out of the kart tank into thin air.
What is left is denatured ,crap, low octain, slow burning piston killing deto juice.
When heavy, large drops of fuel with little or no light fractions enter the combustion process, alot of this isnt burned, the molecule collections are simply to big to consume in time.
This shows as a "rich " mixture, so of course we lean that sucker down to get some temp into the pipe and bugger, it detoed its tits off.
Nothing to do with the jetting or the timing, its bad fuel from simply being left overnight in a tin or tank.

Over night? I'm not one to challenge you. But if it's in a tin it's surely better preserved than in a vented gas station tank. I just asked my in house refueling expert and gas stations are filled twice a week for high use outlets. Kart tanks are plastic so breath. Or are you saying that mixed gas is affected worse?

[F5 Dave]

Ok here's a question. Kart guys seem to like to start their karts on the stands then rev them. From cold- Revvvv. Brake
Revvvvv. Brake. RREEEEVVVV brake.

What do they think they are doing? They don't seem to be warming them up. They can't be tuning them as they are not to temperature and not under load. What do they think they are doing?

Other concerning thing is the spinning wheels at waist height would take you apart if you walked into them.