ESE's works engine tuner

**wobbly** · 22nd February 2018, 15:19

I dont understand at all what you are saying peewee,here we have been given a STA printout of a 50cc engine that i assume has been
measured or modified to the specs that show a huge transfer time area, with a Blowdown number not even remotely matched.
What has this got to do with engines you may or may not have seen with stud issues etc.
All I am saying is that with ports so badly mismatched, any result from moving the Exhaust floor,will be masked really badly by the other issue.

**dutchpower** · 22nd February 2018, 19:46

with ports so badly mismatched !!!!!!!!

**katinas** · 22nd February 2018, 20:24

Originally Posted by wobbly

Here are the STA numbers for a RSA/W 125 cylinder.
Note that these are the actual port numbers,and do not reflect that the Ex has a huge radius on the timing edge.
Thus in reality the actual Cd of the Ex would reflect that of the transfers,making both capable of the same power. Jan stated that any change in timing of the transfers ( up or down )
would loose power - showing that any increase in Blowdown by reducing the transfers /or visa versa upset the delicate flow balance.
Note also Jan stated that lifting the Ex port floor and reducing the duct volume only worked once the Blowdown had been optimized for best power.

Thank you very much

And with rised Ex floor, there is little more space for additional cooling under floor and cylinder wall.

**F5 Dave** · 22nd February 2018, 20:39

So finally swapping my Zeel for an Ignitech. So far so easy.

Running std flywheel stator. 1 pickup 2 lobes.
std dual output coil setup. I've wired both CDI outputs to it.

Seems to like,
Standard setting 2 lobes 1or2 pickup setting.
question: does this fire both CDI?

Also RPM test only seems to go to 2000rpm on tacho despite setting.

Cheers.

**katinas** · 22nd February 2018, 20:45

Originally Posted by wobbly

This is a favorite hobby horse of Ken Seeber and mine.........

Before leaving MotoGP four stroke world , Mr. Furusawa said, that now he will have more time to develope his Yamaha RZ 250 engine cooling pocess !!! Never ending process.

**husaberg** · 22nd February 2018, 21:01

Originally Posted by katinas

Before leaving MotoGP four stroke world , Mr. Furusawa said, that now he will have more time to develope his Yamaha RZ 250 engine cooling pocess !!! Never ending process.

It's a sad buy true story that all TZ's right up to the reverse cylinder ran their water in entirely the wrong direction prior to 1988. The cooler water from the rad actually enterered the head and was pushed down. Thus Ensuring the crankcases recieved the hottest water. exactly the opposite of what should happen.
No doubt the rest of the yamaha road bikes suffered the same fate.

**Muhr** · 22nd February 2018, 21:23

Originally Posted by wobbly

Here are the STA numbers for a RSA/W 125 cylinder.
Note that these are the actual port numbers,and do not reflect that the Ex has a huge radius on the timing edge.
Thus in reality the actual Cd of the Ex would reflect that of the transfers,making both capable of the same power. Jan stated that any change in timing of the transfers ( up or down )
would loose power - showing that any increase in Blowdown by reducing the transfers /or visa versa upset the delicate flow balance.
Note also Jan stated that lifting the Ex port floor and reducing the duct volume only worked once the Blowdown had been optimized for best power.

Thanks

great stuff!

Originally Posted by peewee

usually its just the opposite with the engines ive seen. the transfer sta is far to short with little chance of making any improvements without a welding machine and 10lb of filler rod. mainly from terrible stud spacing is to blame I think. the late model ktm dirtbike engines seem to be pretty good however

Maybe you usually work with bigger cc?

Originally Posted by dutchpower

Why lifting the exh. port floor on 50 cc give less power Wobbly

Is it something you are building?
I will follow this with great interest in such a case.
What I do is more conservative.

**wobbly** · 23rd February 2018, 07:49

F5, yes with the standard setting of 2 lobes,1 or 2 pickups,the default is 2 ignitions per revolution,so as each lobe passes the single trigger
a spark event occurs in both cdi.
Personally I would dump the double ended coil and go with two RS250,RGCV250 coils.

Dutchpower - the Transfer STA being so huge ( as they are very wide obviously ) in comparison to the Blowdown STA, means that if the Delivery Ratio is sufficient to
actually flow enough air to make 38.9Hp via the transfers,then you will get the classic scenario of a huge residual combustion pressure at TPO.
The nowhere near sufficient Blowdown will create a large reverse flow down the A transfer ducts, as they open first, creating havoc with the scavenging regime.
So I believe that when you have a fatally flawed scavenging setup like that, lifting the Ex duct floor for sure wont be able to increase power.
The perfect example was shown by Jan when developing the Aprilia, that lifting the duct floor only made power once the Blowdown was optimally matched to the Transfer STA.

**F5 Dave** · 23rd February 2018, 12:09

Thank Wob. Yeah on lookout for RGV coils but run what I've got for now.
Any thoughts on the low test tachometer? Yet to start it to see what it does running. I did a mod on the early R1 dash to suit the Zeel. May reverse it.

**Jannem** · 25th February 2018, 01:16

Originally Posted by Frits Overmars

Attachment 334752

Makes me wonder why Aprilia went with the intake side offset cylinder head for ditech, as it's already proven not to be that great. To get the plug to the hot side?

One of the ideas I've pondered experimenting with, is to offset the chamber to the exhaust side. That approach is proven to work very well in 4-strokes allowing a lot more compression and reduced ignition lead, but can't say what to anticipate in 2-stroke. Should at least improve the piston cooling and charge vaporization somewhat. Easy to try though.

**wobbly** · 25th February 2018, 09:45

The issue with any offset to a chamber in a 2T is that no matter what, you end up with the MSV off the scale on the wide squish side, and no MSV on the other.
This was a huge issue in the old TZ250G model, that would detonate as soon as the jetting was even close.

**Haufen** · 25th February 2018, 22:39

Originally Posted by Jannem

One of the ideas I've pondered experimenting with, is to offset the chamber to the exhaust side. That approach is proven to work very well in 4-strokes allowing a lot more compression and reduced ignition lead, but can't say what to anticipate in 2-stroke. Should at least improve the piston cooling and charge vaporization somewhat. Easy to try though.

I can confirm your statement for an industrial engine with no proper utilization of the squish effect. As soon as there is some charge motion by SV, it was superior to have the chamber in the middle as already written by wobbly (and to have a MSV as high as possible).

**dutchpower** · 26th February 2018, 07:37

Dutchpower - the Transfer STA being so huge ( as they are very wide obviously ) in comparison to the Blowdown STA, means that if the Delivery Ratio is sufficient to
actually flow enough air to make 38.9Hp via the transfers,then you will get the classic scenario of a huge residual combustion pressure at TPO.
The nowhere near sufficient Blowdown will create a large reverse flow down the A transfer ducts, as they open first, creating havoc with the scavenging regime.
So I believe that when you have a fatally flawed scavenging setup like that, lifting the Ex duct floor for sure wont be able to increase power.
The perfect example was shown by Jan when developing the Aprilia, that lifting the duct floor only made power once the Blowdown was optimally matched to the Transfer STA.

Thanks Wobble

I made transfer time area as big as possible ( Jan Always say every square mm counts )

**wobbly** · 26th February 2018, 08:21

Again in this case the Blowdown is still a mismatch with the Transfer STA.
This would be OK if the duct geometry is compromised, and then its normal to increase the Transfer area to help with the
bad effect the ducts have on flow capability.
What scavenging regime are you inputting with these huge transfers, and why is the Blowdown still limited ?