ESE's works engine tuner

**TZ350** · 5th March 2015, 05:43

Racing at Edgecom http://www.kiwibiker.co.nz/forums/sh...1130838589#top

**rodg** · 5th March 2015, 12:21

Originally Posted by cotswold

Rod, chuck your 50 cylinder back on and do the F5 GP instead

would be keen but out of country watching NZ win cricket world cup final

**RomeuPT** · 5th March 2015, 14:09

Hello.

Wobbly, if you can give a little help on pipes. Thanks
In normal round exit cylinder's a small step (diff diameters) from cylinder exit to exhaust header is good, ok! For example the cylinder exit's at 32mm and the header begins with 34. Seems to work fine.
But say we got a 30 exit round and the calculation of header inicial ideal diameter is about 34, wouldn't it go better with a first small taper cone from 30 to 34? Similiar purpose of an oval to round transition from 37 to 41? I have been doing this, but not sure if it's effect is real.

For example, some "average" minarelli am6 kit's come with good porting from stock (kit's with 70, 75, 80cc), but have a exit diameter of 28mm (and the inicial header of the pipe should enter this 28 diameter), calculating a pipe says it should have 30 ou 31 header. Then I did the same for some pipes, after the piece that fits in the cylinder I put a first cone of 20 or 25 lenght putting the diameter where it belongs. Same goes for even bigger kits with 32 round.

Wrong or right thing to do?

Thanks

**dark art** · 6th March 2015, 04:23

The smoother the pipe (from exhaust port) is, the bigger the hp potential. But not everybody look for max hp all the times.
There are several cases where we want a mismatched pipe, most mx bikes have a considerable step, even smaller cc bikes, not only 250´s.

I´ve been able to extract more power out of a particular engine with a lower ressonant pipe, just like Wobbly described a few pages back, than with a full ressonant pipe. The engine turned more rpm and thus, made more power. With a full ressonant pipe, the electrics and carburation were not able to cope with large torque variations.

**wobbly** · 6th March 2015, 07:52

All the kits I have looked at for 50cc have way too big Ex ducts.
Take AM6 Hebo 192 Ex for example.
The port effective area is 24.2 dia, the Ex exit is 25, it should be 22.2 dia, and the best scenario is the exit should be oval at 24 wide and the header match that.
The step top and bottom does "work", but an oval to round transition is much better.
You can do this as the first cone of the header, but is way better if its done as part of the slip joint spigot.
Stage 6 and the Athena 50cc kits are no better in this regard.
All you have to do is work out the T port or 3 port effective area diameter, and that is the header entry size.
The duct exit should be around 75% area - all this is done for you in EngMod code - easy.
Counterboring the Ex duct exit as far as you can and then pressing in a sleeve to make the correct oval shape is also easy enough if you cant or dont want to get a tig torch in there.

**husaberg** · 6th March 2015, 09:41

Originally Posted by wobbly

All you have to do is work out the T port or 3 port effective area diameter, and that is the header entry size.
The duct exit should be around 75% area - all this is done for you in EngMod code - easy.
Counterboring the Ex duct exit as far as you can and then pressing in a sleeve to make the correct oval shape is also easy enough if you cant or dont want to get a tig torch in there.

A question. I thought of the other day is a Main port with Aux Ports has effectively 2 bridges.
Yet it is said to produce more power than a bridged Tee port.
I always thought (irespective of any main bridge bulging issues) it was down to a interupting effect of the bridge.
But.............

**adegnes** · 6th March 2015, 09:53

Originally Posted by husaberg

A question i thought of the other day is a Main port with Aux Ports has effectively 2 bridges
Yet it is said to produce more power than a bridged Tee.
I always thought (irespective of any main bridge bulging issues) it was down to a interupting effect of the bridge.
But.............

Could it have something to do with the position of the bridge(s)?

**136kg136ps** · 6th March 2015, 11:31

More blowdown area in a 3 port.More of the exhaust area is concentrated higher in it despite the shape of the T port.

**senso** · 6th March 2015, 11:40

In some cylinders you can also make big T shaped ports above the transfers, but the duct shape will be sub optimal and hinder/limit gas flow.

**adegnes** · 6th March 2015, 11:44

Originally Posted by 136kg136ps

More blowdown area in a 3 port.More of the exhaust area is concentrated higher in it despite the shape of the T port.

But what if you made the T-port exactly the same shape as the 3-port, only difference being the central bridge vs one on each side. The T would undoubtedly have more blowdown area.

**RomeuPT** · 6th March 2015, 12:04

Originally Posted by adegnes

Could it have something to do with the position of the bridge(s)?

It has to do with pulse dinamics created by the pipe. Single port opens first then the auxialiary, making the pulse going more "coerent" when the port opens than divided with the T port. The stronger the pulse the better exhaust action..

I am right?

**wobbly** · 6th March 2015, 13:34

Several reasons for the 3 port being superior.
To gain the maximum blowdown the T port needs two things.
A straight top timing edge, and the outer corner rads ro be as big as possible above the A port.
These two requirements both have big downsides.

The first is that the flat top edge has a very big duct length delta between the corner at the T and the corner at the outer edge.
This smears the outgoing pressure front, reducing its peak amplitude, thus scavenging energy.
I tried helping this in a test where the outer, longer length corner was higher than that at the T - sorry no free lunch, no more power.

The second means that the T port side edge is wrapped around very close to the A ports front and top edges, thus dramatically increasing the possible short circuiting of the
flow out of the A port.

And yes the 3 ports stepped opening does create a stronger more coherent exit pulse, and at 98% width and even with big angled pockets at the outer corner exits into the duct, the Cd value
of the T is always compromised in relation to a 68 to 70% width 3 port setup, with lower Aux around to bore centre.

**136kg136ps** · 6th March 2015, 13:43

I haven't modeled them side by side but using Frits suggestion to graph each degree of exhaust one could easily see if it is possible to get equivalent blow down area.Maybe is the gas dynamics of staggering the separate openings but it doesn't look easy to get equivalent exhaust timing,blow down area and exhaust area.Hopefully on of our esteemed sages will clarify.My expertise is big engines with moving parts that go roundy round not up and down.

**richban** · 6th March 2015, 15:47

I am thinking of trying out some 40mm lectron's on my 300. Wob I noticed in your 300 spec the carb recommendation was 39mm. What carbs were you thinking of using. I have never had a really close look at the lectron let alone tried tuning one.

**Bert** · 6th March 2015, 15:57

Originally Posted by richban

I am thinking of trying out some 40mm lectron's on my 300. Wob I noticed in your 300 spec the carb recommendation was 39mm. What carbs were you thinking of using. I have never had a really close look at the lectron let alone tried tuning one.

Why???
We haven't even got to the stage of using the TPS and powerjet... I would have thought there was still a lot of love to be gained yet.