ESE's works engine tuner

[jfn2]

Woobly:

Excellent info. Could you explain more on the long manifold. I'm not to familiar with the TM's. Also will the 2-3mm holes be large enough to cool the bottom of the exhaust duct? Maybe more of a compromise is needed. Like 5mm holes or 4mm, or 6mm? Just wondering. I'll have to try this on my KTM's.

[SwePatrick]

Having been thru the exercise of proving that a hot exhaust duct is no good for power I tested ways of getting better cooling in the TM kart engines
I work on.
The first was to figure out why the factory originally intended to have all the cooling water enter the cylinder via ports under the duct, from the case,and then deleted this
and added a hose to feed water in above the exhaust port - from the side..
After many long hours of thought and trial tests, here is the result.
With all the water flowing over the hot duct, it heats ALL the water,that then flows over the transfer tops,into the head and out.
Thus the transfers are actually being heated up,always a bad idea.
So I first drilled two 3mm holes up thru the plugs under the exhaust duct, and added a water fitting hole into the cylinder facing the boost port.
This allowed some cooling of the duct, but forced the coldest water volume over the transfers.
Result - 1 to 1.5 Hp everywhere.
But the tech minions decided this was illegal,as I had made an extra hole in the cylinder that wasn't shown in the homologation papers.
OK, so fuck them,the papers dont show any water fittings at all, so i made a long screw in manifold that also directs all the cold water, back, over the transfers.
Result, almost the same power, and 1st and 2nd at the National champs over Easter.

Nice!

That verifies my ideas i was talking about earlier =)

Thanks for sharing.

[DoldGuy]

I'm in the process of a top end rebuild on the YZ250, I've decided to go 2.1mm larger on the bore since the cylinder needs replating anyway and the pistons are readily available.
At the moment the cylinder has a double base gasket, all the porting looks as cast.
However I've noticed a few oddities:
-The floor of the transfers is about 1.4mm below the piston edge at BDC.. Why would it be like this? Can I raise the port floor with something?
-There is a large lip (protrudes approx 0.5mm into the flow path) around all of the ports except the main exhaust, the overbore should cut through all of these, will that be a problem?

My plan is to:
-Measure the heights of all ports as they are
-Have the cylinder bored 2.1mm oversize
-Clean up the port edges, in case the lips aren't completely removed
-Recheck heights of the ports, hopefully they haven't changed too much.
-Radius all port edges
-Remove big casting flash but leave the ports standard.
-Smooth the transition from the aux exhaust ports into the main duct?
-Smooth/enlarge the Boyesen ports
-Have Nikasil applied

Does this all sound reasonable? I'm happy with the engine's power delivery, don't really want to mess it up.

Nath88,

Most late model MX 250’s have about 184/185 exhaust 118/120 Transfers. When you overbore, the roof angles will lower the port window (sometimes a lot). The “lip” you referred to, is it on the sides of the port windows (you want those) or on the roof/floor of the window? I have not had my hands on a stock late YZ Cylinder but know that some tuners stagger the transfers for a broader power curve.

Enjoy your post & videos on the FI, keep sharing!

[Flettner]

so what are we talking, twin scroll water pump, twin Radiators. One feeding the crankcase, cylinder, head and one feeding the exhaust stub only?

[husaberg]

so what are we talking, twin scroll water pump, twin Radiators. One feeding the crankcase, cylinder, head and one feeding the exhaust stub only?

Ages I suggested a twin circuit set up so the crankcase only got cooled by ultra cold water, that idea was poo pooed by the panel.

[Flettner]

Ages I suggested a twin circuit set up so the crankcase only got cooled by ultra cold water, that idea was poo pooed by the panel.

Fuck the poo poo panel
The 360 has two Radiators and I've got a twin scroll water pump.Worth a crack?

[katinas]

Seems like the transfer ports are cast about 1mm too low.

Its good point to try rounded piston with modified head. Interesting, how the longer stroke engine react to his.

After first training with rounded piston on SX 85, boy was happy. From side, seems like he can hold longer time with one gear.
First race after two weeks, so it would be more clear.

PS "- Radius all port edges-" be careful with radius on transfer windows top edges (not too much, just for rings ) because of back flow. Page 1900 Frits post .

[husaberg]

Fuck the poo poo panel
The 360 has two Radiators and I've got a twin scroll water pump.Worth a crack?

Id rather not and I think so, you can figure out the order to which I replied

[TZ350]

Fuck the poo poo panel

Always a good philosophy .... Fuck the poo poo ers and do your own thing.

[wobbly]

The trick is to identify what areas need to be cooled, and those that dont contribute more power by being exposed to the coolest water.
Then to find a simply way of keeping the different temp deltas separated.
The best scenario I have used was in the TZ400 classic racer, and then the TZ350 LSR bike.
Cold water enters the cylinder at the rear,and the deck surface is arranged to force all the cold water over the transfers.
The flow then surrounds the Exhaust duct area, then is allowed to flow upward into the front of the head.
This warmed up liquid then runs around the inserts, with good access to the plug threads and the squish area,subsequently leaving the head at the rear of the engine again.
But even in this scenario you have opposing requirements in the same vicinity.
The plug threads and the squish need good cooling, whereas the combustion chamber can be as hot as can be tolerated, to reduce the temp difference between the expanding gas and
the surface it impinges upon.
Coating the chamber with ceramic does just that.

In the TM all I could attempt to do was keep the hot water and the cold water separated and doing the best job,by allowing the hot water from the exhaust to enter the head directly above that area.
Thenat the same time force the main flow of cold water from the case cooling chamber to cool the transfers and enter the head at the rear.
The best scenario would be to keep the chamber between the crankcase and the gearbox, but then run that cold water over the mains to enter the cylinder at the back - just like the TZ setup.

[Frits Overmars]

...the tech minions decided this was illegal

Wob, what do the tech minions say about painting? Surely they can't object to that, can they?
Now there happens to be a paint that is not too good at conducting heat. In fact it was developed to heat-protect Soviet satellites. But it works in two-strokes too.
If you coat the crankcases and the transfer ducts internally, the temperature of the gearbox oil and the wall temperature of the transfer ducts won't matter any more.
You can get the stuff at http://emot.nl/contact.php.

[SwePatrick]

Wob, what do the tech minions say about painting? Surely they can't object to that, can they?
Now there happens to be a paint that is not too good at conducting heat. In fact it was developed to heat-protect Soviet satellites. But it works in two-strokes too.
If you coat the crankcases and the transfer ducts internally, the temperature of the gearbox oil and the wall temperature of the transfer ducts won't matter any more.
You can get the stuff at http://emot.nl/contact.php.

An older project i´ve got has this mod actually.
But i blended my own coating.
It is a ceramic weldingspray that protects from weldsputter that i blended up with some ordinary 2k paint.
Then brush painted it onto the crankhousing.

I testpainted first on a aluminium sheet and heated it up from behind with a torch, it worked =)
But cant rememer any numbers sadly enough

Edit: i tested with a IR gun.

[Frits Overmars]

An older project i´ve got has this mod actually. But i blended my own coating. It is a ceramic weldingspray that protects from weldsputter that i blended up with some ordinary 2k paint. Then brush painted it onto the crankhousing. I testpainted first on a aluminium sheet and heated it up from behind with a torch, it worked =).

Patrick, are you still using this on current projects? And if not, why not?

[SwePatrick]

Patrick, are you still using this on current projects? And if not, why not?

Not on my current project, no.
This because of methanol, the engine has problem reaching temprature as is

Problem with methanol is that you actually need some heat to make the fuel vaporize, but i´m sure you already knew that =)

[JanBros]

working on an excel for T.A's,A.A's, ...for cylinder ports, and just wanted to check if my thinking is correct :

from the RSA we know that 12500=(110315 * 1000)/((124.8 + 8.6) * 66.16) or in units : RPM=(A.A * 1000)/((SV + CCV) * STA) (SV = swept volume, CCV = combustion chambre vol)

so I recalculate the RSA's STA for the RPM I want my engine to perform best at, with NewSTA=(A.A * 1000)/((SV + CCV) * NewRPM) ,
and then transform it to the formula NewRPM = (A.A * 1000)/((SV + CCV) * NewSTA).

for the engine I want to develop, I have the formula for BMEP :
BMEP=(BHP * 448162)/(SV * RPM) (SV is in ccm3 , 448162 is a constant to have all units matching) in which of course RPM = NewRPM from the RSA calculations.

since both RPM's are the same, I can enter the RSA calculation into the BMEP formula :

BMEP = (BHP * 448162 * (SV + CCV) * NewSTA)/(SV * A.A * 1000)

and since I've made an edjucated guess about the BMEP and BHP I want at my "new" RPM, with a certain Head Volume, I can determine the needed Angle.Area :

A.A = (BHP * 448162 * (SV + CCV) * NewSTA)/(SV * BMEP * 1000)

correct or flawed ?