ESE's works engine tuner

[twotempi]

Question mainly for Wobbly and Fritz.

The water flow within an early TZ 250/350 - in one side of the head and out the other - seems a bit odd.

Would it be better to introduce the cooling water around the exhaust port area using a fabricated manifold, and then discharge at the back of the head ( normally the inlet !! )

The TZ's are known to run hot - and often use larger radiators in Australia.

Comments, or have you done this before ??

thanks

[wobbly]

When you change the head to inserts you can also change the water flow with a fitting for the cold water in on the back of the cylinder - under the head face.
Having cold water flow over the Ex is NOT what you want at all.
Keeping the transfer ducts outer walls cold is the prime target.
A TZ will struggle to run under 70 at the best of times with the stock rad,but Hintoes replacement unit is alot better - even though it is simply just thicker..
It is easily possible to add 30mm to each side of a TZ rad and still fit it into the fairing, but the best workaround would be to change the flow completely.
Put the tanks on the ends and make it crossflow with a divider on the RH side.
Hot water in at the RH top, out at the RH bottom, using a bypass - exactly as per the pic I posted back a little.
Then run it at 50* like a good little 2T should be.

[TZ350]

Page 620 ...

Big post by Bucket on setting up carburation with an EGT probe.

And Just for you TeeZee I waded back a hundred pages or so and collected up Wobs comments on setting up 2-Stroke carburation.

More on port radiuses

I have just completed a back to back test on the Ex port radius in a TM 125 kart engine.
The cylinder from the factory was a special "tuned "expensive part number, and I was given a stock one to modify.
For sure the two were very different, the stock one being alot lower timing.
This was fortuitous,in that it enabled alot of room to be used to move ports.

First test was the stock cylinder with the main EX at 194, I put a big radius on the roof giving effective timing at 196.5 ( the trick cylinder was the same at 196.5 )
This instantly picked up power everywhere from 8000 to 14000, with alot better overev power, being 6Hp up at 14000
The next test involved dropping the cylinder,removing the chrome and regrinding the ports to the reverse stagger layout.
The A port being the lowest, to allow alot bigger Aux ports.
The main Ex port now opened around 192,with effective at 195 but the Aux opened at the same time, giving better blowdown area, as well as the flow enhancing radius on all 3 ports.

With the reverse stagger giving better transfer area ( as the B,C ports being high with alot of width compared to the previously high A port ) the engine now made 2 Hp or more than the factory trick cylinder
but was now 8 Hp up at 14000 and gained 400 rpm of usable overev, as previously it dropped dead at 13800 on track.
This setup proved to be quite insensitive to jetting and timing changes, allowing alot more static advance giving much better off corner power without killing revs as this would normally do.
Thus the enhanced blowdown flow of the radius at low port openings,allowed those much lower timings to be used effectively, enhancing power everywhere, but most importantly in the overev,where blowdown is most needed.

Frits is right when he says that the Italian factories are 3 years behind,as they still havnt started to use much of the technology developed at Aprilia even now.

Case Comp and Pipes

Case com is a very complex subject but a few rules of thumb apply.
The higher the bmep of an engine then the higher the delivery ratio, thus a larger case can store the higher volume of ingested air at a higher pressure and this is then available to the transfer ducts.
But the quality of the duct and port geometry also affects the case com required.
The smaller the case vol (higher ratio) the greater the pressure rise in the case as the piston drops - this suits compromised transfer ducts with little or no inner wall shape, as it helps force the flow around thru the ducts quicker.
Good duct/port geometry allows the use of a bigger case as they dont need a large pressure ratio across the port to initiate good flow.
Lastly is the effect of the pipe geometry, the diffuser sucks like hell on the Ex port around BDC, pulling flow thru the transfers, and it is important to match the pipe diameter ( and thus the diffuser included angles) to the transfer port/duct geometry.
Suck too hard on crap transfers and they loose directional control - giving greater short circuiting out the Exhaust port.

Thus you have a Catch22 in that you need a small case to speed up the flow, but this limits the available stored mixture, and you want to suck on the transfers as much as possible, but no so much as to loose the control of the flow direction - or to speed up the loop velocity excessively thus reducing the trapping efficiency..

One myth that needs busting here is that the bulk of the flow thru the transfers is initiated by the piston dropping.This happens in lawn mowers, not racing engines.

Pipe diffuser suction when the piston is around BDC forces the bulk of the flow volume, NOT the pressure in the case forcing flow up the ducts.
When the transfers open there is more pressure in the cylinder than in the case.
Thus we get flow reversal at the initial transfer opening point.
This also means that the transfer port that opens first - flows last, as it has the greatest flow reversal affect,down the duct.

In general, high bmep engines that by default will have good port/duct geometry, will like a case com down near 1.3:1, lower performance engines with crap transfer/duct geometry will perform best with the ratio higher, up near 1.4:1.
Thus as you develop an engine, increasing its efficiency with better porting, then this will allow the use of a bigger case, and bigger pipe diameter/vol, to work with that - the two go hand in hand.

Another curly one to deal with. It would seem that staggered transfer timing would have real flow advantage rather than just taming a too peaky motor.
I figure that with this reversal of flow that the boost port would open first as this would allow the flow from main and aux to potentially reach the rear of the cylinder before being directed up, like wise the aux would open next ensuring the main flows first thus limiting short circuiting out the exhaust??????
Anyone got a spare KE125 cylinder (preferably with aux exhaust ports), mine is heading for the bin!

Honda first used the staggered transfer setup with the RS125/250 and was developed by Helmut Fath ( my hero) as was Exhaust stinger nozzles,for the factory teams.
With the big T port they opened the main first by around 2*, the secs and boost ports last.
Aprilia later came along with a 3 port Exhaust setup with huge aux Ex ports, they now have the mains lower to allow much bigger aux Exhaust area, with the secondarys and boost opening first.
All have the axial angles set at around 22* - 12* - 55* to clear out as much residuals from within the loop area as possible.
The big hooks on the secondarys also flips the flow over on itself under the boost, to clear this area out as well.
Greater flow reversal occurs when there is insufficient blowdown STA,and the TZ250 sacrificed blowdown for more transfer area, something we now know is a mistake - but with limited transfer port area you take your pick of what to compromise.

Only Yamaha stuck with the wank flat roof scenario way after the use by date, and got their arses kicked for years in GP.
Till they finally bought a CNC controlled Jante machine from Czech, went square bore/stroke and using the 500 cylinders on the 250 easily won the champs in 2000 with Olivier Jaques.

The secondarys facing each other relatively flat will always collide, but the hooks rotate the flow under the boost as it exits the port ( easy to see with the tap water Jante trick),clearing out a big "dead" area
in front of the rear port.

All modern race engines have a nozzle restriction at the flange face, as big T ports and tripple Exhausts loose alot of velocity going into the header.
Rule of thumb is a 75% of the effective EX area at the flange.
Stepped oval duct into a round flange does work, but I have used a CNC oval to round transition in the spigot for years, as has Honda in A kit, and Aprilia factory engines, this works way better.
Here is a sim showing my new 400cc F3 engine, with and without the spigot nozzle.

The stinger nozzle effectively removes the stinger tube length from the equation - it was developed for Spencers NSR that had one stinger 150 long, the other was 450.
The nozzle is around 2 to 3mm smaller than the tube stinger .

This is great, maybe not as pertinent to the single port commuter engines we are playing with, but still very interesting. Any chance of an example picture?



So assuming I had a 200mm 18mm ID stinger but didn't have the space for it & could replicate it with a 16mm section a couple of cm long & then just run a 209mm section to the pipe to the muffler? A 16mm stinger is 50cc size & would be certain piston crown doom to run on a 100. Is this what you are saying?

I had heard that tapered venturies apparently used on GP bikes?

Here is an oval to round spigot for Robs GP100 with RGV cylinder.
36mm pipe ID, oval shape at the duct exit is 36 wide by 27 high = effective area of a 31mm round..
This nozzle effect doesnt work on single port engines - I have tried.


Re stinger nozzles - if running a 18mm nozzle on a 100cc then you could connect a 20mm stinger tube to it in basically any length and this would not affect the power at all - in fact using the nozzle with a tapered section out to the bigger tube makes more power.
Aprilia/Derby twins do this as the top pipe has a stinger 60mm long, the bottom one is closer to 220, but the effect works on any 2T.

All but impossible to show properly the scavenging pattern without one of the CNC controlled Jante screenshots but imagine looking out from inside the duct,the piston is the "floor" in front of you.
The flow attached to the septum wall blows straight past your left ear, and the flow hitting the hooks on your right side, rotates clockwise underneath this left side flow,the bottom attaching to the piston - the upper flow pushing upwards.

The FPE superkart engine that won the NZ road title at Manfield a few weeks ago makes 92 RWHp on the Dynojet 168 I use.
Still not quite as good as the RS250 setup we did that won at Laguna Superkart Worlds a couple of years ago.

The powerjet carb is controlled by the Ignitech with a combination of throttle position and rpm in a "truth table".
In general the solenoid is activated with 12V ( no fuel flowing) below 4000 rpm and 75% throttle on the TPS.
Above 75% and around 12400 rpm it is activated again to lean off the fuel curve over the top of the pipe.
Looks like you will be able to reverse the fuel exit, blocking off the hole on the throttle bore side, and take off fuel from the outside bung, thru a needle jet and into the top of the venturi next to the slide.

Well funilly enough that Kawasaki piston gave rise to the idea of a toroid shape.
I think they were trying to get the plug closer to the centre of the combustion area, but of course it shagged the squish action as well as the transfer flow regime.
The toroid shape does everything right and there is no reason to use anything else.

[twotempi]

Page 620 ...

Wobbly - Thanks for the reply. It makes sense to keep the transfers as cool as possible to maintain the inlet charge density.

The reason I mentioned the inlet for the cooling to be around the exhaust port was to minimise the temperature difference around the cylinder to reduce any distortion.

So in order of flow of cool water does 1) transfers first 2) than exhaust, 3) inlet area - make sense ??

[husaberg]

One Day i will stop chocking the thread with articles about old stuff.......
But its not today.
Note the induction controlled by reed and rotary valves.

[bucketracer]

These are great, love reading the old articles, I hope you have plenty more.

[wobbly]

If you feed cold water in over the rear of the cylinder it will cool that side first, you then have to control the flow to prevent it filling the head too soon and bypassing directly
to the outlet.
Having the water forced to flow across the cylinder,rear to front, then up into the head,flowing front to rear, and out at the highest point is what you are trying to achieve.

[twotempi]

If you feed cold water in over the rear of the cylinder it will cool that side first, you then have to control the flow to prevent it filling the head too soon and bypassing directly
to the outlet.

What you have described is exactly how the circulation is for an early TZ !! The entry for the water is at the back of the head ( highest point !! ) and exit at the front of the head via thermostat. The cylinder just takes its chances

Hence the "how can it be done better" query.

Will have a think and play to see how your suggestions can achieved so thanks for your comments

[husaberg]

These are great, love reading the old articles, I hope you have plenty more.

Last thing you want to do is encourage an anorak.
Yes a few more left.
Including a very interesting gearbox configuration on a works Kreidler 50cc.
The suzuki 50cc here has an Alloy frame (always wondered why Suzuki's welding was so chunky)
Updraft on the carbs and also note the shape of the crank-wheels.
I have always thought the 60's Suzuki's were functionally pretty.
oh yeah the carbs in thew last 50cc twin nearly bigger than what you are allowed on the Air cooled 125 Rob.
In fairness your power spread is a little wider though

[husaberg]

more clogging........
More well balanced than most articles i have seen credits a lot more people than some.
But at the end of the day it would have been a team effort.
Shame they didn't have better metallurgy and sponsorship.

[husaberg]

Early Suzuki's mmm...
When one of the riders you pay to race your bikes. nicknames your bike whispering death it can be hardly confidence inspiring can it..........

[chrisc]

Thanks Husa, I love these old articles too. Don't stop putting them up!

[husaberg]

An interesting look at a Kreidler transfer passage.

An interesting look at a Kreidler transfer passage.[QUOTE]

The Kreidler engine shown by TZ350 was cutting edge technology in 1962, but I do not think any of you want to copy transfer passages that, together with twin rotary disks and a twelve-speed gearbox, produced all of 10 HP out of 50 cc.
In case you wonder: the transfer timing was 142°; the single exhaust was way over 200°. Don't try this at home....
Below are some more pictures of the same engine, showing the twin carbs and the screwed-in caps that gave access to the transfer ports for easy modification.
You can also see the hand-operated three-speed gearbox behind the foot-shifted four-speed box.

These are great, love reading the old articles, I hope you have plenty more.

Thanks Husa, I love these old articles too. Don't stop putting them up!

Thanks for the nice comments. Good to know some people enjoy them shame most people missed the MZ a page back
Frits (and Robs) original post has some nice pics of the engine and the carb and Overdrive set up.
I find the 3 speed OD box quite interesting. No doubt an economical solution. it would also make the down changes faster if not a little confusing.

[Frits Overmars]

I find the 3 speed OD box quite interesting. No doubt an economical solution. it would also make the down changes faster if not a little confusing.

Forget about 'a little'. Imagine coming down a long straight in gear 4C, braking at the limit for a hairpin and having to shift down to 2A. Or was it 1C? Or 2B? Or 3A?
Later Kreidler substituted the 4*3-box with a 6*2-box; also twelve speeds, but a little easier to keep count.
As a friend who rode these tiddlers, told me: "Most of the time I hadn't got a clue what gear I was in. All I needed to know was, how often to change down with my foot for a corner, and how to move the hand shifter. You had to get that into your head for every corner. And the tracks were a little longer then: the original Nürburgring had 187 corners..."

[husaberg]

Forget about 'a little'. Imagine coming down a long straight in gear 4C, braking at the limit for a hairpin and having to shift down to 2A. Or was it 1C? Or 2B? Or 3A?
Later Kreidler substituted the 4*3-box with a 6*2-box; also twelve speeds, but a little easier to keep count.
As a friend who rode these tiddlers, told me: "Most of the time I hadn't got a clue what gear I was in. All I needed to know is, how often to change down with my foot for a corner, and how to move the hand shifter. You had to get that into your head for every corner. And the tracks were a little longer then: the original Nürburgring had 187 corners..."

do you have any more pics Frits.
The little was unfortunately my sense of humour.

That pic of the engines is a nice diasembled is a nice example of why 2 strokes are so great esp when you compare it to this.(sorry couldn't find a 5


The Suzuki twin write up a while back has how Ansheidt dealt with the multi speed gearbox's.
I can imagine huge problems with over revving, on over run when the rider got even a fraction wrong.
I seem to remember Hugh Anderson as being quoted something along the lines that even if the wheel lifted off the ground for a second the Suzuki's could also do a big end. That's not to mention the tucking in at all costs the imminent threat of siezure and plus the fact that they were also racing. It makes my head hurt.