ESE's works engine tuner

[Frits Overmars]

Frits, can you tell me what type and name of race fuel was actually used in your world champion winning aprilia 125 race bikes. thanks, nigel.

breezy, I don't think that Jan Thiel will feel OK with the assumption that he is not the father of the winning aprilia 125.

You are quite right Peter.
Breezy, this is one of those seemingly simple questions to which there is not just one simple answer.
For starters, there was a leaded era followed by an unleaded era. The leaded fuel was 130 octane, the unleaded was a mandatory 102 octane if memory serves.
Then there is the fact that the various world champion winning machines were leased by various teams, with various fuel and oil manufacturer's contracts.
The Italian Agip fuel probably was most frequently used.

[TZ350]

Page 1710 .....

Here's a product called Composimold being used by a Thomas H who appears to cruise this forum, if not only the ESE thread. It's far more expensive though at $66NZD + $30 shipping for 20oz of the stuff -_-

http://bucketracing.blogspot.co.nz/2...mposimold.html

Google.co.uk came up with:

Vinamold - Best Value - - Direct from the manufacturer‎

Adwww.extruflexonline.co.uk/vinamold‎
Large UK Vinamold Stocks, 24 Hr Delivery

4 hardness types?

I thought Vinamold was american.

ATAC in general works much lower down the powerband than a powervalve does, and cannot be gradually reduced in its effect.
It works very well to reduce the effect of the pipes return pulse being way too early at lower rpm, but this effect kills the power badly as soon
as the pipe efficiency starts to rise - thus the valve connecting the Helmholtz chamber to the pipe must be switched instantly at a specific rpm.
In a 125 race engine the ATAC would be off at around 8000 rpm, where as the PV may not be closed fully to within 1000 rpm of peak power.

Detonation.

This started te be a problem when 50cc engines started giving more than 17HP, around 1975.
At the time I thought this was a limit on engine power.
Nikasil plated cylinders were very prone to detonation.
Because of the rounded off edge at the top.
At Minarelli/Garelli I solved this problem by sticking the cylinder head insert 3mm into the cylinder.
A good solution, used for many years.
But at Aprilia we found an even better solution: plate the first 5 mm around the bore at
the top of the cylinder.
Later this was machined to a very sharp corner, and this eliminated completely the unnecessary
'dead room' at the top of the cylinder, it also gave 0,3HP more.....
A little bit of still remaining detonation was eliminated by modifying the inner wall of the
transfer ducts, cooling the piston.
But part-throttle detonation remained a problem.....
Which we never had on the dyno!
On the photo you see a piston after a 54HP run...
As long as you keep the throttle wide open a 2 stroke doesn't brake down!

The Aprilia RSW was a ROTAX design.
Later Aprilia made their own engines, but closely followed the original ROTAX design.
Except some small details.
Now they could say everything was 'made in Italy'
Which had financial 'advantages' for certain people!
Who could now take a bribe from the suppliers......as is usual in Italy.
So I am certainly not the 'father' of the Aprilia engines!

I was responsible for cylinder development, starting with 46,5HP and ending with 54HP.
Later, when working at DERBI, I had the idea of making the RSA engine, and made the first sketches.
The actual design was, of course, done on a computer by a professional designer.
Although it won several world championships I don't consider it a big success...

Aprilia always used AGIP fuels and oils for dyno testing
102 octane.
We were given face masks and special gloves, which we never needed for the 130 octane fuel.....

When modifying a cylinder measuring duct sizes is not easy, especially in the curves!
You can see our solution to this problem on the photo....
Round 'sensors' fitted to a piece of welding rod!
We had them from 7-7,25- 7,5 and so on until 28mm.
Behind the cylinder, in the wooden block.

I did not design this engine, nor did Frits.
It was Aprilia who wanted their 'own' engine.
The designs and the engines were made by ROTAX.
I still consider a V engine with a single crankshaft as the best solution!!

A Dutch friend of mine, Thijs Hessels, had improved the original cylinders by epoxying the outside curve, and giving the mixture a more upward direction. His private Aprilia proved faster than the 'works' bikes. The Aprilia racing boss, Jan Witteveen, demanded that Thijs should give those cylinders to him. Otherwise Thijs would not be able to get any more spare parts for his bike!!

I started working with an existing engine, a ROTAX, with an existing cylinder and exhaust pipe.
During the year dozens of different exhaust pipes were tested.....



The original Rotax A duct was something like this....

With this modification a ROTAX cylinder gave 46,5HP instead of the normal 44.
This happened in 1994, a year later I started working for Aprilia.
They were still epoxying ROTAX cylinders, but had decided to make their own cylinder.
The development of this cylinder was to be my work.
This cylinder was called the APC, and was destined for all 125 and 250 private riders.
It gave the same 46,5HP, but of course without epoxy.
I got the oldest dyno there was, and had to learn to use the computerized system.
As I had never touched a computer before it was not so easy.
But I quickly learned, the system was very precise and repeatable.
I was given the casting models and had to go to the foundry to have some cylinders cast,
While waiting for the castings to be machined I worked with ROTAX cylinders.
I won some power by making the auxiliary ports bigger, but they were already too high I thought.
So I made sure the APC cylinders had lower auxiliary ports, and I also filed their sand cores to make the exhaust duct a lot smaller, as I had already, successfully, tried on some ROTAX cylinders.
There were some small mistakes in the casting models, they were quickly corrected.
And then real development could begin!
I started by making the B-ports and ducts as wide as I could, and this improved bottom power, without losing at the top.
And I had one casting with a narrower C-port, made by filing the sand core.
Here the B-ports could still be made wider, and it proved to be the best cylinder of the lot.
So we got to 48HP
We also bought a lot of dentist tools and burrs, and a filing machine.
And a flow bench.
Power improved by making the auxiliary ducts longer, and wider.
But at a certain point we made a hole, ending up in the cooling water space!!!!
To cure this the casting model had to be modified.
I also had a wooden model made for use on the flow bench.



To determine the best size of the auxiliary ports and ducts.



They seemed to 'like' having a downward angle.
The casting model was modified in this way, and so we reached 49HP.



I decided to try to make the exit of the exhaust duct, and the flange, a bit wider, and won another 0,6HP

I discovered that making the underside of the transfer ports even with the piston in BDC
was very important: considerably more power, less detonation and far better piston cooling.
We started to have the exhaust ducts CNC machined in 1999 I think.
But first we had to overcome the new fuel regulations in 1998
102 octane had to be used instead of 130 octane.
We expected BIG problems.....
But within a couple of month's we had more power than before!
The compression ratio was lowered from 19,5:1 to 16:1
And the tailpipe restrictor was made 0,25mm bigger.
Then a very serious combustion chamber development was started.
The result was that parallel squish was the best, with a squish height of 0,75mm
Less squish height would give more torque but less revs.
At 0,45 the piston touched the head....
Then a head insert with a much wider squish band (50% of cylinder surface) was tried.
And that proved to be the final touch.
We now had more power than with the 130 octane fuels, and less problems.



The sharp edge between combustion chamber and squish band proved to be very important.
Even a small radius would give 0,5HP less..

Vannik or anyone that knows stuff, I don't have your software so don't know this, if combustion does not happen, what happens to the air velocity in the combustion chamber at / after TDC? Does the rapid turbulence in the combustion chamber stop and reverse at some stage, as the squish starts to open up again? Or does it keep going but just slow down a bit?

The turbulence is caused by the breakdown of the main flow. Because of the viscosity (in effect the internal friction of the fluid) the main flow progressively break down into ever smaller eddies and if left long enough all the main flow and all the eddies will stop. The main flow is from the transfer port loop and a stronger better directed flow with more kinetic energy can generate a lot of turbulence before it stops. If you have weak flow by the time combustion happens you need the extra flow from the squish to generate extra turbulence to get good combustion.

On the other side if you have strong flow and thus good turbulence the extra turbulence can speed up the combustion too much and you loose power but mostly overrev. This explains why engines do not always behave the same to squish changes. Good engines use squish to minimize end gas to stop detonation while poor engines use squish to add turbulence.

So to answer the question: Turbulence cannot reverse, it is a one way street after creation. The bulk flow with the squish opening will loop slower and slower, both because of the increase in volume and because it keeps generating turbulence until it completely stops.

Pistons:


We had cast and forged pistons.
Cast pistons gave slightly more HP, but sometimes cracked.
0,8mm piston rings gave more HP than 1mm rings.
As the auxiliaries and transfers overlapped each other a certain power los was caused by this.
So closing the pin hole in the piston was tried.
There were many solutions that were tested, but they all caused some trouble.
In the end the best, and most reliable, solution was welding then closed.
This was very well done by PANKL in Austria, and never caused any trouble!

Do you mind me asking why do you think cast pistons made more hp than forged?

Because forged pistons had a tendency to 'bend' their top inwards.

Transfer ducts.

Many transfer ducts with small differences were tried.
We found more power by enlarging the A-port in the direction of the exhaust.
Only the lower half, but it was important to give the A-duct an inclination away from the exhaust!
The ducts were very conical, the smallest point being the port.
In and outside walls of the ducts had a constant radius from top to bottom.
The flow remained attached to the inside radius and so cooled the piston and eliminated detonation.
Flow bench testing and the Jante type testing proved useless for power improvement.
Giving the rear side of the B-duct an inclination versus the middle of the cylinder gave a big improvemet

[jamathi]

breezy, I don't think that Jan Thiel will feel OK with the assumption that he is not the father of the winning aprilia 125.

The Aprilia RSW was a ROTAX design.
Later Aprilia made their own engines, but closely followed the original ROTAX design.
Except some small details.
Now they could say everything was 'made in Italy'
Which had financial 'advantages' for certain people!
Who could now take a bribe from the suppliers......as is usual in Italy.
So I am certainly not the 'father' of the Aprilia engines!

I was responsible for cylinder development, starting with 46,5HP and ending with 54HP.
Later, when working at DERBI, I had the idea of making the RSA engine, and made the first sketches.
The actual design was, of course, done on a computer by a professional designer.
Although it won several world championships I don't consider it a big success...

Aprilia always used AGIP fuels and oils for dyno testing
102 octane.
We were given face masks and special gloves, which we never needed for the 130 octane fuel.....

[Niels Abildgaard]

I was responsible for cylinder development, starting with 46,5HP and ending with 54HP.
Later, when working at DERBI, I had the idea of making the RSA engine, and made the first sketches.
The actual design was, of course, done on a computer by a professional designer.
Although it won several world championships I don't consider it a big success...

We are many that will love to read a short step describtion of going from 46 to 54 and I will like very much to hear how a Jan Thiel 125ccm engine would have looked with freedom and money no problem.Pure phantasy.
Please?

[jamathi]

We are many that will love to read a short step describtion of going from 46 to 54 and I will like very much to hear how a Jan Thiel 125ccm engine would have looked with freedom and money no problem.Pure phantasy.
Please?

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!

[diesel pig]

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!

Believe me much more than one person is interested.

[tjbw]

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!

Jan, we are all interested.

[Tim Ey]

Jan, we are all interested.

Nothing else to add to that statement

[ken seeber]

jan, we are all interested.

yes, yes & yes

[teriks]

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!

The above might become the most quoted message the thread.

Count me in as interested, very much so!

[shnaggs]

Count me in Jan... I am all ears!!!

[guyhockley]

Plus one (more)...

[breezy]

breezy, I don't think that Jan Thiel will feel OK with the assumption that he is not the father of the winning aprilia 125.

ouch.... please dont shout at me peter.... my apologies ... my english is very poor.. sorry Jan and sorry Frits if my wording made you feel uncomfortable, thanks for reply and information,which i have passed on to the interested party...

i am, as others, interested in Jans work

[TZ350]

My wife is going a couple of days to her sister, then I will do it.....

We would love to hear more.......

[Carel H]

Jan, I just mist the 1968 TT by a year, but you're lot inspired me to build motorcycles. Just at home. And maybe winning. Winning is a combination of many things.