ESE's works engine tuner

[ief]

Small engmod Q.

What would be an appropriate TUmax for say a fast road bike? (if that makes a difference, guess it does)

[fixer]

Interesting times ... have had my new baby (2002 Aprilia RS50) on the ESE dyno a couple of times now, with some interesting results.

Saturday Jan 12
With standard pipe - a subdued 5hp (though I raced it like that at Tokoroa and it was still fun!)
With ex-David-Diprose Conti pipe (for Derbi 50) - a much healthier 7.7hp. Pipe wouldn't fit so was held on with springs and masking tape. There was an earlier post about this.

Monday Jan 21
With pipe properly mounted and an adaptor turned up to match the exhaust port in the barrel (25mm) to the pipe header (32mm) - a bit more hp (8.1hp I think) but the powerband was narrower and moved up the RPM range. Initially this adaptor had a sharp step in it from the smaller diameter up to the larger diameter.

This is where it got interesting. A suggestion was made to smooth out the step in the adaptor and try it again. Instinctively, this seemed likely to produce a positive result. In fact it wasn't. The result was worse in every respect. There was less peak power and the powerband was narrower!

I have a new-found respect for those who dabble in 2-stroke exhaust pipe design. Nothing, I suspect, is obvious.

Tim

[wobbly]

You can increase the com or the timing or the squish velocity till the program SCREAMS - "DETONATION " this happens close to a TuMax of 1000.

[kel]

Tim
re the exhaust port outlet - I posted this some time back. Pictures and quote courtesy of pit-lane.biz [GP125] All that you wanted to know on Aprilia RSA 125 ...

TZ mentioned how the Honda RS pipe inlet is larger than the GP exhaust port outlet, while this is common place on 4 strokes for the purpose of AR I wasnt aware it was used on 2 strokes but on reviewing RSA photos I came across this

Jan Thiel "One wants the pressure wave coming back into the cilinder but NOT the burned gases that are hot and can cause detonation!"
Makes sense.

[husaberg]

Tim
re the exhaust port outlet - I posted this some time back. Pictures and quote courtesy of pit-lane.biz [GP125] All that you wanted to know on Aprilia RSA 125 ...

and i followed with Mr Honda's version
The removal of this step removes HP
From Memory Mr Bangs foul stroke also has one built in.

Jan Thiel "One wants the pressure wave coming back into the cilinder but NOT the burned gases that are hot and can cause detonation!"
Makes sense.

[richban]

and i followed with Mr Honda's version
The removal of this step removes HP
From Memory Mr Bangs foul stroke also has one built in

Ah yes it does. Funny last night I just made the step bigger on the bottom and a little less at the top. Mad into building pipes at the moment. Should have lots of stuff to try on the next big dyno session.

[koba]

Ah yes it does. Funny last night I just made the step bigger on the bottom and a little less at the top. Mad into building pipes at the moment. Should have lots of stuff to try on the next big dyno session.

It's great to see you are gearing up some pipes for a big session...

[richban]

It's great to see you are gearing up some pipes for a big session...

I am pretending to know not, what you mean.

[kel]

Ah yes it does. Funny last night I just made the step bigger on the bottom and a little less at the top. Mad into building pipes at the moment. Should have lots of stuff to try on the next big dyno session.

Isnt that the wrong way round, or are you just trying to mislead the followers

[koba]

I'm still playing with MOTA, I'm finally learning to meaningfully read the wave data and pressure traces.
MOTA seems really limited in this compared to Engmod but that's expected. It's still got enough in there for me to learn a good amount from.

I'm starting to feel confident that I'm reading the data well and making informed conclusions.

The next step for me is probably starting again on the engine with all new measurements and shooting for a clear goal.
Currently I've been trying lots of things with the goal of learning by playing, I've kept good notes which helps but It's still really easy to get lost in the hundreds of files and many different directions of experimentation.

This new effort will take quite some time as I have a lot of measuring to do and I like to keep the bike operational for each round.

[koba]

Isnt that the wrong way round, or are you just trying to mislead the followers

If he means it top relative to bottom perhaps but that reads more like before relative to after to me...

Shit that doesn't make much sense.


I know there will be more authoritive, modern sources but if that is from Bell's 4 stroke book I seem to recall him mentioning it's a worthy area to experiment in.
Not that I would admit to wasting time reading books on poppet droppers.

[richban]

I know there will be more authoritive, modern sources but if that is from Bell's 4 stroke book I seem to recall him mentioning it's a worthy area to experiment in.
Not that I would admit to wasting time reading books on poppet droppers.

Its all experiments. Yeah I have re read Bells book recently and now just working through options that could improve things. Will find out what works and what doesn't. Funny though coz the transition now does look quite like the RSA header port match. Or should I say mismatch. Anyway its fun playing.

[koba]

Its all experiments. Yeah I have re read Bells book recently and now just working through options that could improve things. Will find out what works and what doesn't. Funny though coz the transition now does look quite like the RSA header port match. Or should I say mismatch. Anyway its fun playing.

Yes, yes it is!

[2T Institute]

I have a new-found respect for those who dabble in 2-stroke exhaust pipe design. Nothing, I suspect, is obvious.

Tim

Not quite right it always obvious just you only realise it after the fact, two strokes are like women and kids they never do what you want them to do.

[Frits Overmars]

Interesting times ... have had my new baby (2002 Aprilia RS50) on the ESE dyno a couple of times now, with some interesting results.
Saturday Jan 12 With standard pipe - a subdued 5hp (though I raced it like that at Tokoroa and it was still fun!)
With ex-David-Diprose Conti pipe (for Derbi 50) - a much healthier 7.7hp. Pipe wouldn't fit so was held on with springs and masking tape. There was an earlier post about this.
Monday Jan 21 With pipe properly mounted and an adaptor turned up to match the exhaust port in the barrel (25mm) to the pipe header (32mm) - a bit more hp (8.1hp I think) but the powerband was narrower and moved up the RPM range. Initially this adaptor had a sharp step in it from the smaller diameter up to the larger diameter.
This is where it got interesting. A suggestion was made to smooth out the step in the adaptor and try it again. Instinctively, this seemed likely to produce a positive result. In fact it wasn't. The result was worse in every respect. There was less peak power and the powerband was narrower! I have a new-found respect for those who dabble in 2-stroke exhaust pipe design. Nothing, I suspect, is obvious.

re the exhaust port outlet - I posted this some time back. Pictures and quote courtesy of pit-lane.biz [GP125] All that you wanted to know on Aprilia RSA 125 ...

Tim, right now you may be more interested in ' All that you wanted to know about the Aprilia RS50'. Here are some numbers to play around with. Exhaust pipes don't come any simpler than this, but don't let that fool you; this pipe was good for eight championships. Just don't show it to the Poms; year after year they keep trying to beat those Dutch 50 cc bikes .
About the step in the exhaust duct: if there is a step and you remove it, you lose power. I think the main reason is that in removing the step you increase the duct volume. The Malossi cylinder I experimented with has no step at all, but as you can see in the pipe drawing, the exhaust duct is quite narrow. That works.