ESE's works engine tuner

[casal-fan]

Some wishful thinking:
Attachment 330290

Presume you like the concept since you posted the picture?
If so, it makes me happy. I´m betting on the 72X72 config.

[wobbly]

There are a couple of things in play that affect the egt reading of a perfectly well running engine.
If you look at the velocity and temp profiles as we have seen in CFD analysis of the Exhaust port/header you see that the temp varies dramatically
with not only position along the duct, but also across it profile.
I know that the very short probes as sold by some manufacturers for kart/bike use only intrude some 10 to 15mm into the header,and these read much lower than
if the tip is on the centerline.
So I try to standardize on 3X bore down the header and in the middle,using exposed tip probes from EGT industries - the only type that have a guarantee, 2 years for the Stinger type.
The exposed tip is way faster reacting and as long as the data sample rate is high enough ( above 10Hz ) you get to see what is actually happening in real time.
Some gauges only update the screen readout every couple of seconds - useless.

[karter444]

If you can only get to 500* then there is a serious problem.
It can only be a few issues that will cause this, way too much compression or timing for the fuel, or severe short circuiting.
I had the short circuiting problem on a 250 MX engine that had the Aux ground around to bore center.It ran just fine but when the piston was changed from a
Wossner to a Prox it ran like shit and would not respond to leaner jetting changes at all.
Finally in desperation I pulled it down ,to discover that the Wossner had a machined hole in the skirt above the small end that did not go around past the centerline.
The Prox had a huge cast in cutout,that was well past centerline and this was seriously joining the Aux and A transfer together as the piston passed over them.
Changing the piston fixed the jetting issue immediately,where previously it would run rich ( 500* ) no matter what jet was in it.
Any engine on petrol should be able to run past 600* in the header without any problems at all, no matter what the cc,rpm or bmep.

Hi Wobbly, when you say short circuiting do you mean exhaust gas entering the transfers or transfer outflow entering the exhaust
duct . with regard to the piston cutout it seems most pistons have some form of cutout that will link the Aport to the aux exhausts , why is this cutout there and why do some pistons have such different size cutouts . as you mentioned a cr 250 wossner has a relatively small cutout while a kx 250 pro x has a large cutout , both would join the A port and aux ex to some extent ,so I imagine some joining of these ports is acceptable
cheers Richard

[41juergen]

Presume you like the concept since you posted the picture?
If so, it makes me happy. I´m betting on the 72X72 config.

Hey Rui, that's a nice head. Is that for your single cylinder bike and was that done by yourself or by Martin?

[wobbly]

If the Aux port is in front of the pin hole then no linking occurs,same with the skirt holes or pockets for weight reduction.
When linking does occur there must be transfer mixture entering the Ex as the egt drops,and going leaner does not fix this.

[breezy]

Husaberg thanks for links... had a go but the exhaust port bits a bit of a guess and the the near transfers also. seems to be some conflicting/ cant find dimensions, although thats probably me

[peewee]

Attachment 330642
KTM200SX-EXC ’98-16
Ø Small End (A) 20.00mm
Ø Big End (B) 28.00mm
Center to Center (C)118.00mm
Width Small End (D)15.90mm
Width Big End (E 15.90mm
Total Length (F) 151.40mm
Eye to Eye Center (G) 94.00mm
Ø Big End Pin (H) 22.00mm
Length Big End Pin (I) 55.00mm
Washers 22 x 37 x 1.0mm
Remarks Barreled Rod

RD250 + RD350 Air Cooled -360-
Ø Small End (A) 20.00mm
Ø Big End (B) 28.00mm
Center to Center (C)110.00mm
Width Small End (D)16.00mm
Width Big End (E)16.00mm
Total Length (F) 141.50mm
Eye to Eye Center (G)86.mm
Ø Big End Pin (H) 22.00mm
Length Big End Pin (I) 50.75mm
Washers 22 x 37 x 1.0mm

RD400 ’76-79 -1A1/2T2-
Ø Small End (A)20.00mm
Ø Big End (B)28.00mm
Center to Center (C)115.00mm
Width Small End (D)16.00mm
Width Big End (E)16.00mm
Total Length (F) 147.00mm
Eye to Eye Center (G) 91.00mm
Ø Big End Pin (H) 22.00mm
Length Big End Pin (I) 51.00mm
Washers 22 x 37 x 1.0mm

I realized now why I used the Suzuki small end bearing. the ktm small ID is 20mm. banshee is 21mm. so to use the 16mm piston pin the bearing has to be substituted. seems like the Suzuki cage was wider or had wider rollers or something like that also, hence the reason I didn't use the ktm small bearing

[peewee]

Hi Wobbly, when you say short circuiting do you mean exhaust gas entering the transfers or transfer outflow entering the exhaust
duct . with regard to the piston cutout it seems most pistons have some form of cutout that will link the Aport to the aux exhausts , why is this cutout there and why do some pistons have such different size cutouts . as you mentioned a cr 250 wossner has a relatively small cutout while a kx 250 pro x has a large cutout , both would join the A port and aux ex to some extent ,so I imagine some joining of these ports is acceptable
cheers Richard

something like this doesn't link the exh direct to the transfer

[peewee]

Husaberg thanks for links... had a go but the exhaust port bits a bit of a guess and the the near transfers also. seems to be some conflicting/ cant find dimensions, although thats probably me

what about lifting the main exh floor a hair. jan has talked about it a lot of times. I lifted mine about 5mm (82mm stroke) although ill never know truly how well it works because I never had a previous dyno, but I don't think im losing any power. so if nothing else, the only thing ive lost is alittle time

[wobbly]

If the Aux ports are around to the centerline that piston will link them to the A port big time with such a deep pocket.

Re the RSA, it had the main Ex floor lifted by some 3mm from memory.

[jamathi]

If the Aux ports are around to the centerline that piston will link them to the A port big time with such a deep pocket.

I really do not understand why people make such idiotic pistons...

[trevor amos]

Wob, Frits, Jan?
In a typical cylinder reed 5 transfer port engine, having a Honda style ex-port, with a transfer port opening sequence of A then B then C would there be any overall net gain from having the B and C ports open simultaneously, where the C port lift gives more transfer port area and a touch more time /area. Or, would the overall balance of the transfer, in cylinder flow streams be compromised with just such a change leading to a reduction in performance? I can see both sides of this dilemma but not the more beneficial one, but I bet you guys can! Any advice is always appreciated by the greater readership.

cheers, Trevor

[Frits Overmars]

Wob, Frits, Jan? In a typical cylinder reed 5 transfer port engine, having a Honda style ex-port, with a transfer port opening sequence of A then B then C would there be any overall net gain from having the B and C ports open simultaneously, where the C port lift gives more transfer port area and a touch more time /area. Or, would the overall balance of the transfer, in cylinder flow streams be compromised with just such a change leading to a reduction in performance? I can see both sides of this dilemma but not the more beneficial one, but
I bet you guys can.

As far as I'm concerned, you just lost that bet Trevor, because I have no way of knowing how that modification would influence the transfer balance.
Increased time.area is useless if it worsens short-circuiting. I'd need all data of all the transfer ducts before I could make an educated guess.

Having said that, even increased short-circuiting can have its merit. It drops the EGT, so the powerband may commence at a lower rpm value.
If you ever worked on a 100 cc direct-drive kart engine, you may remember the big single B-port, doing just that.

[Martin1981]

I really do not understand why people make such idiotic pistons...

Because they don`t know and don`t care about real high performance engines. It`s all about fast selling and making money....as usual.

[breezy]

If the Aux ports are around to the centerline that piston will link them to the A port big time with such a deep pocket.

Re the RSA, it had the main Ex floor lifted by some 3mm from memory.

i suspect the Aprilias non pocketed piston and wrist pin capping stopped this happening

i have been trying to make port map up from the " Aprilia files" posted way back to see what it looked like but wasn’t able to find all the info to do it and as such some of it was guess work.

Frits / Jan/ Wobbly are you able to show the aprilia rsa / rsw 125 port map? i have tried searching on the net, so as not to bother you, but have drawn a blank.