ESE's works engine tuner

[TZ350]

Ok, dug out some cylinders and took some photos.

I think the bulk of the heat that needs to be lost from the cylinders cooling system mostly comes from the underside of the exhaust port duct, the top of the upper cylinder and the top of the transfer ducts when hot exhaust gas enters them after the blow down STA has become to short for the RPM.

I don't think that just cooling the upper cylinder would be enough for road racing.



Aprilia 122

There must be a good reason that cooling water enters the cylinders around the exhaust port first. It could be an issue air cooling the underside of the exhaust tract properly.



It does look like it would be possible to cut the water jacket away enough to get fins onto the upper part of the cylinder but as the bulk of the heat comes from the exhaust port area and the top of the transfers. Getting enough good finning onto them to cool them adequately looks a bit harder.



Still the Aprilias inlet looks like it is made to do the business.



RGV250

Same issues cooling the exhaust port area.



Another problem with the RGV cylinder is the head studs, if you cut the water jacket away you loose the head stud holes.



I had thought about putting the fins on the outside and filling the water jacket with fine copper dust and cooking oil for heat transfer.

[TZ350]

TZ, just looking at the pics (which look well cut) it would seem the subs will bleed into the transfers, have you made flush pin plugs?

No plugs, it wasn't planned they just grew that close.

I am surprised at Wob's comments about the hot bridge, when I'd done it I'd assumed the extra area would give support & not overheat, but I suppose it isn't attached to a particularly well cooled area.

Me too, I would have thought wider would be better too, I will just have to suck it and see now.

[SwePatrick]

About heat in my 88cc machine.
A little powerloss thou.. but i bored the cylinder a couple of hundreds bigger.
In other words: i got instead of 0.07mm clearance for piston i got 0.09 in clearance.

this is also good with all forged pistons to do as they are prone to seize a bit.

I bored my 136cc project 58.02mm instead of 58.00.

this allows the piston to take som more heat before it smears on the cylinderwall and ruins the day at the track.

easy to understand why,,, i haven´t got GP budget and wan´t to race all summer.

Rgds
Patrick

[husaberg]

Ok, dug out some cylinders and took some photos.


There must be a good reason that cooling water enters the cylinders around the exhaust port first. It could be an issue air cooling the underside of the exhaust tract properly.





I had thought about putting the fins on the outside and filling the water jacket with fine copper dust and cooking oil for heat transfer.

Why not absorb some of that heat as well instead of just transferring it
Specific heat values of common materials: (not conductivity)
Material Specific Heat
(kJ/kg/degree C)
Water 4.18
Aluminium 0.94
Copper 0.39
Air 1.01
Concrete 0.88

Instead of cooking oil I would use a solid at room temp medium with copper . but with external fining and lots of it.
Paraffin wax, , its typical characteristics are:
• Melting point: 52 degrees C
• Specific heat: 3.27 kJ per kg per degree C
• Specific heat of fusion: 210 kJ/kg
So to increase the temp of 1kg of the wax from 47 to 52 degrees takes 16.35kJ, but to push it past 52 degrees takes nearly 13 times as much energy. (Or, to risk causing confusion, you could dissipate in it a power of 14kW for 15 seconds to melt 1kg.)


Paraffin wax is non-toxic, doesn't explode (although it will catch fire if you expose it to a naked flame) and is easily handled. Special waxes designed specifically for this change-of-state heat storage purpose are also available with melting points in 10-degree C increments from 50 degrees to 100 degrees C,
But if a Wax with a melting point of 100 degrees (similar to water unpressurised boiling point) was selected and some external source of fining was available to help dissipate the heat?
Would it still be air cooling? would it work? fiik

But then again as you see water cooling is still far more efficient. 4.18 vs 3.27 kj/kg per deg C

[wobbly]

As with most things we deal with there is two sides of a coin involved that leads to having to compromise.
A bridge with a smaller area/volume will expand less,but of course it also has less face area to support the piston/ring.
The ultimate expression of this is the Aprilia that uses as much area as possible to gain Blowdown STA.
The opposite is the CPI cylinders that have alot of material between the main port and tha Aux.
I needed alot of blowdown in the RZ400 cylinder to make 120CHp so the width has been halved,its just about to go on the dyno
with Wossner pistons using the same ovality as the 485 with wide bridges.
The new pistons have a cutaway above the pin that extends to the bore centerline, so I couldnt go any wider the other way.
So we shall see the effect immediately.

[twotempi]

Hi guys,

I want to use a particular ProX piston but it comes with two holes drilled in the skirt for lubricating a exhaust port bridge.
My cylinder does not currently have a bridge so what are your opinions on what to do.

Possible options are

1) Do nothing to the holes. Yes, there will be some leakage but..............
2) Use say a brass domed head rivet with knurled shank inserted from inside the piston - and peened over very carefully on the outside.
3) Spot weld the holes
4) Put bridge into exhaust port - which would allow better STA as well.
5) Some other option that i have not thought of

My preferences are either 1) or 4)

What do you think?
thanks in advance

[dinamik2t]

What's the model of your piston?
Using a different brand/model, without bridge holes but similar dome/wrist pin/heights isn't an option?

[speedpro]

TZ uses pistons with holes to lubricate the ex port bridge but he doesn't have a bridge in the port. He's filled the holes with something along the lines of Devcon but super dooper. Hasn't come out yet.

[Yow Ling]

Hi guys,

Possible options are

4) Put bridge into exhaust port - which would allow better STA as well.

My preferences are either 1) or 4)

What do you think?
thanks in advance

How would you do that? I have thought along those lines , maybe if I was a gynacologist I could do it. I just not that clever.

[bucketracer]

I want to use a particular ProX piston but it comes with two holes drilled in the skirt for lubricating a exhaust port bridge.
My cylinder does not currently have a bridge so what are your opinions on what to do.

TeeZee just glues his with Belzona, when people questioned it he posted pictures of race pistons from an Aprilia or Honda RS that were done that way, now I think he intends trying Devcon.

[bucketracer]

Before I start on my Wobbly engine I wanted finish the Ex side port mods on my old air cooled engine and run it up on the dyno.

First step is to prep a new piston, I have been using a dished piston but Wob tells me they are not that great so future ones will be flat top.

Attachment 230863

The oiler holes for the exhaust bridge need plugging.

Attachment 230864

Normaly I would weld them but was persuaded to try glueing them with some super duper stuff thats as tough as shark shit.

And hey, this is Buckets, we are allowed to try new ideas.

So the were prept up with a dremmil.

Attachment 230866

And the finished result.

Attachment 230865

Then new holes were drilled for oiling the bridge between the exhaust and transfers.

Attachment 230862

The Ex/Trans bridge

Attachment 232140

After 40+ dyno pulls at near 30hp the glue blocking the oiler holes is still there inside the piston..

Attachment 232766

Thomas comes up with the goods again......... RSA ?

Attachment 232769

Transfers

Attachment 232768

Main Ex Port 66% of bore

Attachment 232767

Old bridge oilers glued up, so now we know for sure that gluing the piston works, just like Thomas said it would.

TeeZees posts where he talks about glueing the oiler holes.

[TZ350]

The first piston that I glued, I used Belzona, this one is glued with Devcon F.



A bit of prep and a thin layer of glue worked into the holes to seal them. I think a thin layer is less likely to pull lose than a thicker one.

[SwePatrick]

there´s one more way..
soldering. use alutite.

http://www.youtube.com/watch?v=OLvDHwQFvAM
http://www.youtube.com/watch?feature...v=zaaZ0R8-2Bw#!

[TZ350]

Took the failed piston off tonight. Not only does it have what looks like detonation damage over the exhaust port, it has turned the ring and there is a lot of mechanical damage too. The blue line is where the ring peg is.

On a positive note this piston has done many dyno runs, the full race meeting at Te Puke and a fast practice at Kaitoke and only failed during the slow warm up laps for the next session.

Looking at the underside of the piston there is the localised over heating from the detonation but no central stain on the underside of the piston crown that you would expect if the engine was generally running hot.

From comments that Wob has posted, the problem seems to have been that the ignition curve was OK for hard out full throttle work like a dyno run or hard out racing but was to advanced in the mid range when just trickling around.

[TZ350]

TZ uses pistons with holes to lubricate the ex port bridge but he doesn't have a bridge in the port. He's filled the holes with something along the lines of Devcon but super dooper. Hasn't come out yet.

The glued up bridge oiling holes and one of the new holes drilled for oiling the area between the exhaust and main transfer ports.