ESE's works engine tuner

[Flettner]

All sorted Swepatrick, EFI at work.

[FastFred]

Only proper way to get fuelinjection to work fully in a dynamic twostroke raceengine is to add a 3d map with rpm,throttle,airmass inputs.(map sensor won´t work)

As when pipe start doing it´s thing you have to predict fueldemand at fullthrottle without airmass meter, this makes it very off the chart in hitting the throttle again after a 'long' coastdown(pipe has gotten a bit cooler and doesn´t work 100% for a couple of moments until heat is up again)

Problem is the airmass meter unit, you need it close to the carb(to get fast reaction), and carb spits fuel the wrong way sometimes, this will lead to malfunction of airmass sensor.

Some good thoughts there. At certain rpm Carbs can spit back fuel but TeeZee reports that he has noticed much less spit back through the EFI throttle body, probably because the main injectors are in the transfers and timed to finish squirting by BDC. Interesting thought about the wave collapse in the chamber on over run and loss of bulk air transfer until the pipe heats up again.

[F5 Dave]

So the EFI reverse equivalent of an accelerator pump where it might lean off a bit when EGT drops below ideal for whatever revs. Maybe.

[Ocean1]

So the EFI reverse equivalent of an accelerator pump where it might lean off a bit when EGT drops below ideal for whatever revs. Maybe.

Or you could stick a small restriction in the intake, measure the pressure drop across that and supply fuel to match the corresponding air flow!

I'll just dash off a quick patent before someone else thinks of it...

[jamathi]

I just figured out something was amiss with my musing......
The Aprilia has contra rotating cranks it wouldn't mater that the direction was reversed, as one would always be rotating the opposite anyway

Crankshaft rotation can have some influence on engine power.
At Aprilia we once tested a kart engine.
Just to see how a reed-valve engine worked.
Originally it had a 30mm carburetor of course.
And non-variable ignition.
Fitting a 41mm Aprilia carburetor didn't make much difference.
And neither did the Aprilia ignition....
Reversing crankshaft rotation gave 1,5HP more!

About the 125 RSA
It was a bit of a delusion, but it gave a little bit more power than the RSW.
A big disadvantage proved to be the, necessarily, inclined carburetor.
It was bad in braking on-track.
And the fuel level in the float chamber lowered at full throttle, making the engine run weak.
To solve this problem finally a fuel pump had to be fitted.
Most dyno work was done solving these problems.
Cylinder development was always done on the RSW engine
In order to use a cylinder on the RSA its 'liner' had to be shortened on the C-side, as it disturbed inlet flow.
After shortening such a cylinder it gave less power on the RSW engines.
And most of our cylinders were destined for RSW engines.

The Aprilia 250 RSA was made to raise the gearbox output shaft.
The frame designers saw that as important.
It had the traditional side inlet.
When the first engine was ready it was tested as a twin, something we normally never did.
It gave the same HP as the RSW, everybody was very happy.
And a bottle of champagne was opened.....

[jonny quest]

The best power for a single cylinder 125? 70hp? I read that as all 500 test were done with a single 125.

Why would it burn down with a larger carb?

All the tests were done with a single cylinder engine,
And a 39mm carburetor, with a bigger carburetor the piston would melt in a couple of seconds....
The best power they saw was about 70HP I think.
The same injection was also tried on the 125.
Same HP as with a carburetor.
There was no injector in the crankcase.
I would have loved to have it on the 125!

[jonny quest]

Why was RSA cylinder development done on the RSW?

Isn't the RSW the design right before the RSA?

[husaberg]

The best power for a single cylinder 125? 70hp? I read that as all 500 test were done with a single 125.

Why would it burn down with a larger carb?

The 70hp was from the 500 which was a twin. and not always 500cc it started off under 400CC and grew.
Its not Frits or Jans favourite engine and as they have said, they had nothing to do with it.
With the testing They likely only used the RSW125 bottom end as a test mule, as it was convenient.
With the 500 fours and 250 twins using a single mule cylinder, allows you to work four times as fast and four times as cheaply.

Crankshaft rotation can have some influence on engine power.
At Aprilia we once tested a kart engine.
Just to see how a reed-valve engine worked.
Originally it had a 30mm carburetor of course.
And non-variable ignition.
Fitting a 41mm Aprilia carburetor didn't make much difference.
And neither did the Aprilia ignition....
Reversing crankshaft rotation gave 1,5HP more!

About the 125 RSA
It was a bit of a delusion, but it gave a little bit more power than the RSW.
A big disadvantage proved to be the, necessarily, inclined carburetor.
It was bad in braking on-track.
And the fuel level in the float chamber lowered at full throttle, making the engine run weak.
To solve this problem finally a fuel pump had to be fitted.
Most dyno work was done solving these problems.
Cylinder development was always done on the RSW engine
In order to use a cylinder on the RSA its 'liner' had to be shortened on the C-side, as it disturbed inlet flow.
After shortening such a cylinder it gave less power on the RSW engines.
And most of our cylinders were destined for RSW engines.

The Aprilia 250 RSA was made to raise the gearbox output shaft.
The frame designers saw that as important.
It had the traditional side inlet.
When the first engine was ready it was tested as a twin, something we normally never did.
It gave the same HP as the RSW, everybody was very happy.
And a bottle of champagne was opened.....

Thanks for your reply Jan
I was certainly unaware that a pump was eventually used.
I understand Kenny Roberts ran into trouble with the forward mounted carbs on the triple as well, but in their case under braking.
Pretty sure Wob mentioned the BSL500 had the same issues as the Roberts 3 also
I have seen it written that, If you were going to design a new disc valve single it would be with twin discs one either side.
What size would the disc be, the same as the RSW? or larger?
Also the Derbi reed valve engine you inherited what changes did you make to that?
Frits once posted a dyno graph it was very impressive for a reed valve. likely More than a Honda produced.

Also am i right in sugesting when you say the RSA250 gave the same power as two of the RSW singles, It was only when the APF RSA cylinders were used.
I read on a site that the additional head studs when deleted as a trial actually cost quite a bit of power. Is this because of distortion? distortinn leading to poor sealing

[jonny quest]

Wasn't the RSW a side rotary valve?

Only 70HP front a twin 500? Ouch! Or was the 70hp a 250 single hp number

[husaberg]

Wasn't the RSW a side rotary valve?

Yes. it is a conventional disc valve.

Only 70HP front a twin 500? Ouch! Or was the 70hp a 250 single hp number

But it was a very oversquare very compromised design. That was in essence a overbored 250.
Yes the 70HP rom one cylinder of a 500 twin.

[jamathi]

The 70hp was from the 500 which was a twin. and not always 500cc it started off under 400CC and grew.
Its not Frits or Jans favourite engine and as they have said they had nothing to do with it.
with the testing They likely only used the RSW125 bottom end as a test mule, as it was convenient.
With the 500 fours and 250 twins using a single mule cylinder, allows you to work four times as fast and four times as cheaply.




Thanks for your reply Jan
I was certainly unaware that a pump was eventually used.
I understand Roberts ran into trouble with the forward mounted carbs on the triple as well, but in their case under braking.
Pretty sure Wob mentioned the BSL500 had the same issues as the Roberts 3 also
I have seen it written that, If you were going to design a new disc valve single it would be with twin discs one either side.
What size would the disc be, the same as the RSW? or larger?
Also the Derbi reed valve engine you inherited what changes did you make to that?
Frits once posted a dyno graph it was very impressive for a reed valve.
Also am i right in sugesting when you say the RSA250 gave the same power as two of the RSW singles, It was only when the RSA cylinders were used.

The first RSA engine was made at Derbi, it was meant to be able to beat Aprilia.
The Derbi reed valve engine gave 47,5HP when I arrived there in 2004.
So obviously something new had to be made.
But it was improved to 49.5HP, mainly through better inlet flow and better crankcase cooling.
It's electric water pump proved insufficient, so it was not used on the RSA.

The 250RSA had side inlet, so it used RSW cylinders, all tested and developed on a 125 RSW single.
It simply was a normal 250 with the gearbox output shaft in a higher position, and therefore the crankshaft rotation had to be reversed.

The 125 RSA/Derbi was a completely different engine, with the inlet valve on the rear.
This was done after flow bench tests showed that the RSW inlet flow was very much disturbed by the connecting rod, it seemed logical at the time!
Later we realized that the RSA inlet flow collided with the cylinder wall at the opposite side.
So there was very little gain....
Fins directing the inlet flow versus the transfer tunnels would have helped I now think!

In 2006 a special RSA cylinder was made with the cylinder bolts in a different position.
It had also better cooling of the exhaust duct and small cooling canals through the inside wall of the
transfer ducts, which improved power by 0,5HP!

So I finally came upon the idea of using a disc valve on each side, as already had been done by Exactweld.
But I decided to retire, a Dutch friend made some crankcases, but never finished the work.
So I still wonder how it would have gone....

The 70HP I mentioned for the 500 was, of course, on a single cylinder.
The engine used for those tests was a 500 engine, with only 1 crankshaft fitted.
Testing on 2 cylinders is more complicated and inconvenient.

Derbi was owned by the Piaggio group, which owns several Italian makes.
At the beginning of 2005 Piaggio bought Aprilia.
So they decided to close the Derbi racing workshop and I had to return to Aprilia, which I did in 2006.

The piston melting with a bigger than 39mm carburetor was probably caused by a weak spot just before maximum torque.
Because no powerjet was used at the time....

[husaberg]

The first RSA engine was made at Derbi, it was meant to be able to beat Aprilia.
The Derbi reed valve engine gave 47,5HP when I arrived there in 2004.
So obviously something new had to be made.
But it was improved to 49.5HP, mainly through better inlet flow and better crankcase cooling.
It's electric water pump proved insufficient, so it was not used on the RSA.

The 250RSA had side inlet, so it used RSW cylinders, all tested and developed on a 125 RSW single.
It simply was a normal 250 with the gearbox output shaft in a higher position, and therefore the crankshaft rotation had to be reversed.

The 125 RSA/Derbi was a completely different engine, with the inlet valve on the rear.
This was done after flow bench tests showed that the RSW inlet flow was very much disturbed by the connecting rod, it seemed logical at the time!
Later we realized that the RSA inlet flow collided with the cylinder wall at the opposite side.
So there was very little gain....
Fins directing the inlet flow versus the transfer tunnels would have helped I now think!

In 2006 a special RSA cylinder was made with the cylinder bolts in a different position.
It had also better cooling of the exhaust duct and small cooling canals through the inside wall of the
transfer ducts, which improved power by 0,5HP!

So I finally came upon the idea of using a disc valve on each side, as already had been done by Exactweld.
But I decided to retire, a Dutch friend made some crankcases, but never finished the work.
So I still wonder how it would have gone....

I am familar with the dual disc engine, I was unaware he never finished it though.
Last time i looked at their website, most of the two stroke stuff including their Aprilia like cylinder conversion for Honda RS engines had been removed, A rather sad sign of the times.

The Exactaweld was a great concept but sadly i assume underfunded.
https://www.kiwibiker.co.nz/forums/s...post1130703351
When was a kid i used to stare and marvel at pictures of the Chassis they did for the Norton coswoth engine.

As an adult i understand that the lack of chaassis is a result of the overly huge engine.

[katinas]

Hi,

Started it yesterday and revs like like crazy chainsaw, I have never heard such a sound from this old engine. For this experiment made 1 cylinder crank, because Honda ns 250 engine is 2 cylinder. Ports timing and size is original . Cold winter outside and now no possibilities try on the road.
Thanks Harry R...

[ken seeber]

Thanks Hooser,

Clearly Jan has a good eye for good 2 stroke ports..




OK Katinas, good post, BUT you have a lot of questions to answer:

1. To achieve the same port timings, did you use the same (ns250) con rod centres?
2. Did you retain the ns250 pipes?
3. Did you "wet sump" the crankcase?
4. How did you attach the piston rod (approx Ø35) to the cast (?) piston?
5. No con rod upper bearing shown. Was this a one sided thing (the pic) or is this just a mock up?

Certainly I (and I'm sure a shitload of others) look forward to understanding what you have done more. Well done though.

BTW, welcome to ESE.

[SwePatrick]

All sorted Swepatrick, EFI at work.

Yes.. but i still think there can be improvements.
Especially in roadracing.
An mx machine isn´t that sensitive like a hardcore tuned gp machine.