ESE's works engine tuner

[fatbastd]

Sorry all-searched but I can't find it.... What is the relationship between relative air density changes and main jet size change? Was it 5% jet change for every 3% RAD change?

Thanks.

[RomeuPT]

The sharp rear cone will pump up the peak number at the expense of powerband width, and yes the diffuser shape you describe will help crap ports
as it wont be pulling a big depression before bdc and cause the loop to short circuit early in the cycle.
Taper mids are just a way of balancing how much diffuser "power " you want vs the effectiveness of the rear cone.
The taper is so small, it in itself has no real effect on the pressure ratios in the sim.
Remember as Frits said there is only a finite energy available, and a taper belly is one way of twisting around where that energy is used to achieve a particular end goal.
Banshee ports are "not bad " but suffer from old fashioned axial angles - the B ports are angled up sharply.
The A ports are quite flat and dont like a very strong diffuser action, but for sure they are better than an old TZ750 layout that has a very wide and flat A port.
There are some quite fat Banshee pipes like Shearer inframes, and these do work alot better than the skinny things I have also seen.

Yep, those best selling toomey's are very thin, with very shalow diffuser, only a little strong in the very end. They are all around power but also make the best peak power of all aftermarket excluding the dune and drag pipes like cpi, sheareer etc. Kind weird how they work so good.

The banshee fires sparks at both cylinders two times per rpm right!? So a simple ignitech DC-CDI-P works there if setted for two sparks for rpm?

[Frits Overmars]

.. it may be worth getting a Mazda 13B housing to have a look at. They have an insert in the exhaust port to reduce heat transfer from the exhaust to the aluminium, Im not sure what it is made of but it is hard as hell

On the inside it is also hot as hell.

...But some fresh charge is drawn into the 2T's exhaust header before being pushed back into the cylinder. And we don't want to heat this fresh charge if we can help it. So a 2T's shield ideally needs to shield the cylinder without getting to hot itself.

You've got that right, TZ. But how do you achieve that? The same way as on a piston crown: polish it.
Shiny surfaces won't absorb any heat; they will just reflect it, and as soon as the heat is gone, so is any reflection.

[peewee]

On the inside it is also hot as hell.


You've got that right, TZ. But how do you achieve that? The same way as on a piston crown: polish it.
Shiny surfaces won't absorb any heat; they will just reflect it, and as soon as the heat is gone, so is any reflection.

i dont understand. is a polished piston top and exh tunell the way to go ? in the past ive never bothered doing such things but if it helps i may try it

[peewee]

Banshee ports are "not bad " but suffer from old fashioned axial angles - the B ports are angled up sharply.
The A ports are quite flat and dont like a very strong diffuser action, but for sure they are better than an old TZ750 layout that has a very wide and flat A port.

i recall atleast one honda engine (cr500) used the same old fashion angles and its a bugger to correct. lift the cylinder slightly to fix the floors and then your limited on the roof angles (unless you sky jack the timings well above 130*). leave the cylinder low to get a decent angle on the roof and your floor angles are shit. honda must have known these angles were no good because im not sure they did it on the 125 or 250cc mx stuff. between lifting and grinding i was never able to get over 20* on the A port and the floors werent quit right either. i gave up and moved on to other engines

while im thinking of it, you got any recomendations for a good banshee drag racing pipe ? im just getting familiar with the banshees

[Grumph]

On the inside it is also hot as hell.


You've got that right, TZ. But how do you achieve that? The same way as on a piston crown: polish it.
Shiny surfaces won't absorb any heat; they will just reflect it, and as soon as the heat is gone, so is any reflection.

Ceramic coating is also an option. HPC in Auckland do it I believe.

FWIW i think the ex port inserts in the rotaries are inconel. Going back a few years, some models of Datsuns had an insert too - bloody hard to grind out....

[wobbly]

Just one thought to add to the 125 stroke thing - the Aprilia made peak power at 12800 and reved to 14500, if we tune the long stroke in a similar
fashion we will have peak HP at 11800 and peak revs = 13500 to give 26M/Sec.
Peaking at a lower rpm will necessitate cranking the bmep thru the roof,and no one has been able to better the Aprilia BMEP at 12800rpm so who thinks they can do better than Jan Thiel et al.
Not me for sure.

The jetting rule of thumb for diameter based jets as we would normally see in a Keihin carb on a well tuned engine is a 3% change in RAD = 1 jet change.

The ceramic coating works to keep heat from raising the temp of the base material - the ceramic surface IS hot as hell ie NFG for a 2T EX port nor in the squish
band of the piston/head - go coat the rest of the combustion surfaces if you want, but not the squish area - it CAUSES deto, been there, blown that up.

Yes polishing the piston and the chamber reflects the radiated heat and reduces the thermal load, ceramic coating the entire chamber area ( less a ring around the squishband ) works more effectively.

The Banshee has wasted spark, a completely dumb idea invented by accountants.
The much better way is to cut a slot in one lobe, making it 3 equal gaps ie lobe/gap/lobe all the same,then program a P2 to fire 2 coils with 3 lobes.
The split lobe is cylinder 1, I always make this the LH side.

[Cheesy]

On the inside it is also hot as hell.


You've got that right, TZ. But how do you achieve that? The same way as on a piston crown: polish it.
Shiny surfaces won't absorb any heat; they will just reflect it, and as soon as the heat is gone, so is any reflection.

Hot as hell is probably a bit of an under statement. I realise that the air charge goes out the port and back so the inconel insert idea was along the lines of minimising heat transfer as opposed to removing heat (and simpler). Looking at material properties stainless would just as good for a cooler 2 stoke exhaust as inconel.... If it was actually beneficial at all

[Yow Ling]

Thanks for the tips and the example from your own work and relating the experience of the snow sleds, I am encouraged by the idea.

Attachment 303141

I too think a lot of heat enters the cooling system from inside the exhaust duct and on my latest air cooled motor I am building, I plan on fitting a finned copper (or alloy) spigot that goes as far back into the exhaust duct as possible and which has cooling finn's on the outside.

The spigot will be a loose fit in the exhaust duct to cut down on heat transfer from the spigot to the cylinder and by using a small forced air fan and duct directing cooling air over the spigot finns it might be possible to keep the initial header-pipe section cooler and also reduce the heat uptake into the rest of the cylinder.

Air scoops and ducting will be part of the picture too.

Instead of ducting and fans etc why not put a temp sensor in the header then when its over say 1000°F turn on a pump that sprays water on the skin of the header, wont take much room or weight and wont block the desperately needed cooling air for the cylinder, will be a bit steamy , but no rule against that in the MNZ book

[RomeuPT]

Just one thought to add to the 125 stroke thing - the Aprilia made peak power at 12800 and reved to 14500, if we tune the long stroke in a similar
fashion we will have peak HP at 11800 and peak revs = 13500 to give 26M/Sec.
Peaking at a lower rpm will necessitate cranking the bmep thru the roof,and no one has been able to better the Aprilia BMEP at 12800rpm so who thinks they can do better than Jan Thiel et al.
Not me for sure.

The jetting rule of thumb for diameter based jets as we would normally see in a Keihin carb on a well tuned engine is a 3% change in RAD = 1 jet change.

The ceramic coating works to keep heat from raising the temp of the base material - the ceramic surface IS hot as hell ie NFG for a 2T EX port nor in the squish
band of the piston/head - go coat the rest of the combustion surfaces if you want, but not the squish area - it CAUSES deto, been there, blown that up.

Yes polishing the piston and the chamber reflects the radiated heat and reduces the thermal load, ceramic coating the entire chamber area ( less a ring around the squishband ) works more effectively.

The Banshee has wasted spark, a completely dumb idea invented by accountants.
The much better way is to cut a slot in one lobe, making it 3 equal gaps ie lobe/gap/lobe all the same,then program a P2 to fire 2 coils with 3 lobes.
The split lobe is cylinder 1, I always make this the LH side.

Are you sure about 12800? Isn't more like 13k? Peak torque at 12800 maybe?

[wobbly]

Sorry ,yes I meant to say peak torque at 12800 where the max bmep is seen.
But still a couple of hundred rpm makes no difference to the impossibility of making the long or short stroke variation " better " than what the Aprilia R&D achieved.

[TZ350]

Instead of ducting and fans etc why not put a temp sensor in the header then when its over say 1000°F turn on a pump that sprays water on the skin of the header, wont take much room or weight and wont block the desperately needed cooling air for the cylinder, will be a bit steamy , but no rule against that in the MNZ book

Good idea, I like it and could do it alright, we will have to put it out there and see what the consensus about its legality is.

[Drew]

Good idea, I like it and could do it alright, we will have to put it out there and see what the consensus about its legality is.

That's water cooling. All good for 100cc.

[Reckless]

Instead of ducting and fans etc why not put a temp sensor in the header then when its over say 1000°F turn on a pump that sprays water on the skin of the header, wont take much room or weight and wont block the desperately needed cooling air for the cylinder, will be a bit steamy , but no rule against that in the MNZ book

Good idea, I like it and could do it alright, we will have to put it out there and see what the consensus about its legality is.

I would suggest the amount of water you would need to carry, the pump and the electrics would negate any gains made by cooling the header pipe. We ran EGT sensors on all engines we raced in Gearbox class. Standard equipment with a micron guage which gave track mapping also etc etc. Most of us had laptops.

Secondly spraying water on hot steel would work harden it would it not?? Generating cracks?

I have always wondered why you guys don't run track mapping on your buckets? With the level if tech in this thread I would have thought it was a must have? Unless you are or its banned??

Anyway just really posted to say there is people like me reading this thread with interest and not posting!
Keep it up great stuff

[koba]

That's water cooling. All good for 100cc.

Agreed.

R.E. logging etc, this is budget racing!