Two-stroke performance tuning?

[TerraRoot]

macdizzy's used to be a great place, anyone else mourn the board's there going commercial?

RE cdi's: Megajolt won't work on 6v, http://home.earthlink.net/~jcgebhart/megaignite.html i'd efi the lot if i could sort it to run on 6v. off to indian ebay for 12v system off a late rx135 need more money

[Yow Ling]

Also you bring up something that's being annoying me, where the heck do people get an adjustable cdi for a 6v single cylinder two stroke? 3d or 2d?

www.zeeltronic.com has fully programmable cdi's about 100 euros , I have one on my LC and it is great

[TZ350]

That is a really good idea Skunk (in my opinion)....the TYPE (i.e useable spread) of power you are looking for on a 4 speed transmission is quite different to what you would be looking for with a close ratio (6 speed) (or,like Cagiva did with one of their Mito road 125's 7 speed!) gear box.

Screen Scrape:-

"You may be interested to know, that in many cases a non-squish combustion chamber, with its complete utilization of the mixture to offset the power-limiting effects of a necessarily-lower compression ratio, has proven to be best in absolute terms of power and economy."

Read it all here:- http://toostroke.blogspot.com/2007/12/squish-bands.html

"Our application here, of course, is strongly biased toward maximum horsepower, and that points toward a squish-band head - which is what you will have in most motorcycles in any case. I will warn you, now, that it may be unwise to follow the old-time tuner's habit of increasing an engine's compression ratio as an opening gambit in the quest for better performance. Indeed, before your work is done you may find it necessary to reduce your engine's compression ratio below the stock specification. You see, in the final analysis it is not so much compression ratio as combustion chamber pressure that determines the limit - and these are not at all the same things."

So its a trade off between broad power and maximum horsepower.

.

[SS90]

Also you bring up something that's being annoying me, where the heck do people get an adjustable cdi for a 6v single cylinder two stroke? 3d or 2d?

You had me up to here........

Pardon?

[SS90]

Screen Scrape:-

"You may be interested to know, that in many cases a non-squish combustion chamber, with its complete utilization of the mixture to offset the power-limiting effects of a necessarily-lower compression ratio, has proven to be best in absolute terms of power and economy."

Read it all here:- http://toostroke.blogspot.com/2007/12/squish-bands.html

"Our application here, of course, is strongly biased toward maximum horsepower, and that points toward a squish-band head - which is what you will have in most motorcycles in any case. I will warn you, now, that it may be unwise to follow the old-time tuner's habit of increasing an engine's compression ratio as an opening gambit in the quest for better performance. Indeed, before your work is done you may find it necessary to reduce your engine's compression ratio below the stock specification. You see, in the final analysis it is not so much compression ratio as combustion chamber pressure that determines the limit - and these are not at all the same things."

So its a trade off between broad power and maximum horsepower.

.

Well..... screw me sideways......

[bucketracer]

Its good to see TZ backing up what SS90 and Thomas have to say by referencing other material that supports them.

Your a good sport TZ, thanks for all the real info and extra reading that goes with your intelligent input.

.

[Skunk]

That is a really good idea Skunk (in my opinion)....the TYPE (i.e useable spread) of power you are looking for on a 4 speed transmission...

Actually it's now a 6 speed box. TF/TS125. TF has a crap 1st - 2nd ratio so effectively a 5 speed...

The figure you have posted (for the duration of the exhaust) is very much where I would suggest a 4 speed air cooled 125 would want to be (What primary gear ratio do you have?)

As you missed the bit earlier about it being a new engine I have to ask which timing you're asking about. The TF or the AX?

what ideas do you have for the duration of the transfers..... (I like 131...(just as a number)

Haven't calculated that yet. Ballpark is in that region though.

Oh, also (when you have the time) could you measure the distance from the top the piston to the top of the cylinder (measured when the piston has JUST closed the exhaust port) and post that as well?

30mm.

skunks Ax100R is limited by that 4 speed transmission, but carb size is open....... (hmmmmmm)

Carb is restricted now. I'll be paying careful attention to the volume of the intake path...

"You may be interested to know, that in many cases a non-squish combustion chamber, with its complete utilization of the mixture to offset the power-limiting effects of a necessarily-lower compression ratio, has proven to be best in absolute terms of power and economy."

Read it all here:- http://toostroke.blogspot.com/2007/12/squish-bands.html
So its a trade off between broad power and maximum horsepower.

Broad power is my aim - I don't give a rats about peak power.

[TerraRoot]

thanks yow ling, it's nice but seems to need a 12v supply and it seems like it's only 2d, a fully mapped 3d ignition curve should produce a much softer engine still with good power.

Any one have some thoughs on EFI?
http://www.rzrd500.com/phpBB2/viewto...ight=efi+rz350
http://www.rzrd500.com/phpBB2/viewto...ight=efi+rz350

you could run a massive intake and it would still be driveable everywhere.

[SS90]

Hi thought you may be interested in this cylinder skunk.

I's called an ML1, by a small tuning company called Quattrini.

(They don't have a website, it's just a small group of guys from an area in Italy called "Parma", kind of a "Holy Grail" for 2 stroke tuners in Italy.)

The layout is based on a Kart sport engine (originally, although I am unsure which one), and as such it is quite a revvy cylinder, accordingly you have to run a primary gear ratio of 2.86 or 3.00 (which is quite low really)

I am hoping to get 25 PS and 18 NM from this cylinder, (They have 17 PS and 15NM "plug and play", and are quite "peaky"...but I am currently unsure why that is!)

I am suspecting that is because the ones I have tested on the dyno have all had primary compression ratios set "old school" (too high), with unsuitable (again "old school") expansion chambers, as the port layout and scavenge patterns look alright to me.

The exhaust/ transfer durations are 183 deg and 128 deg (according to the information I have been given, but I will measure that, as I suspect they a bit longer than that.

I also believe you could go a few degrees higher on the exhaust (if those specs are correct)

I read somewhere that you made your own exhaust, are you intending to use that on your new engine, or make a new one?

[speedpro]

you could run a massive intake and it would still be driveable everywhere.

That's the theory anyway, as far as fueling goes. There's a bit more to it.

[Chambers]

The exhaust/ transfer durations are 183 deg and 128 deg (according to the information I have been given, but I will measure that, as I suspect they are a bit longer than that. I also believe you could go a few degrees higher on the exhaust (if those specs are correct)

Exhaust Duration of 183 = Ex Opens 88.5 ATDC and Transfer Duration of 128 = Trans Opens 116 ATDC.

"you could go a few degrees higher"

Ex Opens 86.5 and Trans Opens 116 ATDC.

With more upswept 24-30 deg main transfers, shallower secondaries 10-15 deg, 55 deg boost and a pipe with a long shallow first diffuser section seems to be pretty much where current port timing is for bikes with a useable power spread.

On a piston port motor, inlet ports that are to big lose velocity and therefor inertia and can wind up with less air in the crank case than there would have been had the mixture stream had enough inertial push to thoroughly pack the crankcase as the piston closes the inlet port.

The reed valve cylinder that SS90 has shown us is a very good looking piece of work. Its very big inlet is possibly why the cylinder requires a bigger crankcase volume as the inlet stream may lack velocity and inertia to propery fill a tighter volume. This cylinder looks like it benifits from a pipes ability to draw mixture through the crankcase.

.

[Skunk]

Hi thought you may be interested in this cylinder skunk.I read somewhere that you made your own exhaust, are you intending to use that on your new engine, or make a new one?

I did. It was an attempt to tame the power delivery. I'll make a new one when I sort the new engine.
Attached are a couple of crappy pics of the TF125 bits. I've been busy helping prep a KR150 and a GSXR600K4 for next weekend, so nothing of mine has been looked at.

These pics are standard TF. I'm still in the planning/learning/theory stage.

[SS90]

Exhaust Duration of 183 = Ex Opens 88.5 ATDC and Transfer Duration of 128 = Trans Opens 116 ATDC.

"you could go a few degrees higher"

Ex Opens 86.5 and Trans Opens 116 ATDC.

With more upswept 24-30 deg main transfers, shallower secondaries 10-15 deg, 55 deg boost and a pipe with a long shallow first diffuser section seems to be pretty much where current port timing is for bikes with a useable power spread.

On a piston port motor, inlet ports that are to big lose velocity and therefor inertia and can wind up with less air in the crank case than there would have been had the mixture stream had enough inertial push to thoroughly pack the crankcase as the piston closes the inlet port.

The reed valve cylinder that SS90 has shown us is a very good looking piece of work. Its very big inlet is possibly why the cylinder requires a bigger crankcase volume as the inlet stream may lack velocity and inertia to propery fill a tighter volume. This cylinder looks like it benifits from a pipes ability to draw mixture through the crankcase.

.

Yes, this one will be an interesting project.

The manufacturer, while they have taken Kartsport technology, and adapted it (well), in my opinion, they have not really spent the time to correctly develop the set up. (they recommend, like I say a primary drive gear ratio of 3.00), as well as a primary compression ratio of over 1.5:1.

Obviously I will be going lower than that (the primary compression), quite a bit actually, due to the specifics of this cylinder (as well as the design of the new exhaust)

I will put a figure on the ratio I use, so we can all have useable data for the future.

We all know 1.5:1 is the maximum, but as such, there will be a minimum value as well (I don't know what that is yet, and have never seen any data to say what the minimum is) it would be nice to have a value. (using modern expansion chamber designs)

Mush like Chambers has suggested.

The engines I have seen set up like this, have all (4 in total) had the same power (17 PS and 15 NM), which has always been dissapointing. However, all the engines of this type I have had on the dyno have not been built by experienced tuners, so I suspect that has a large part to play.

Last year I fitted one of my/our exhausts to one of such set ups (no other changes) and one made 3 PS more instantly.

I can honestly say that that particular exhaust design is 2 year old technology.

I have spoken to other people over here, and 2 others have been able to get 25 PS (with quite alot of work) I am hoping to get similar results with less work ( actually none on the cylinder).
I believe that this is a good example of a cylinder that NEEDS as much modern set up as can be managed.

For this cylinder, there is only one (specific) exhaust available (see attachment), and, it really is not very good.

It's an "old tech" design, and not really very impressive with it's results.

A friend of mine (who works for Huskvarna) is designing an exhaust specifically for this cylinder (using up to date calculations), and the whole engine will be set up to specs using ideas we have spoken about on this and other threads.

I will use this engine to collect data for that exhaust as well.

The customer is adamant we use the exsisting "squish head" though...... so that is the only thing I don't like. (but the squish area is a little different to others, and could be considered quite modern thinking)

[SS90]

I did. It was an attempt to tame the power delivery. I'll make a new one when I sort the new engine.
Attached are a couple of crappy pics of the TF125 bits. I've been busy helping prep a KR150 and a GSXR600K4 for next weekend, so nothing of mine has been looked at.

These pics are standard TF. I'm still in the planning/learning/theory stage.

Cool!

I know how hard it is to find time to work on your own stuff skunk!

What are your current thoughts/opinions on cylinder heads? (and squish/non squish)

[Skunk]

Cool!

I know how hard it is to find time to work on your own stuff skunk!

What are your current thoughts/opinions on cylinder heads? (and squish/non squish)

Ummm, I'm so new that I haven't enrolled in a school yet... To call me a beginner at engine work is way too generous.
The ESE engine thread is what encouraged me to give it a go and taught me what boost and transfers are!
Don't ask me for my opinion yet, I'm very much reading and trying to comprehend it all.
So far I've decided (probably) on a non-squish head and about 188° exhaust.
The rest I'm still mulling over and researching what will go best with that for my engine.
On top of that I have the option of piston port and reed (as it is) or going full piston port or full reed. Hence the long discovery process. There are many things I need to check and measure before I make any decision; and that will be passed by a few people for their input too.
The worst thing for me is everything seems to look at maximum power rather than maximum duration of power (which is my aim).

I have plenty of time and no resources, so don't wait up!