ESE's works engine tuner

[TZ350]

Ok I have nearly finished fitting the Aprilia TPS and now its time to think about ignition curves again.

I got into trouble at Taupo and Kaitoke by having a to aggresive ignition curve which was great for WOT but over advanced for reduced throttle settings.



This is Wobblys suggestion for my engine on wide open throttle WOT but will need to be retarded around the peak torqe point when the throttle is partly closed.



Here is an Aprilia RS250 curve sent to me by Kel and you can see that above 8,000rpm when its starting to get on the pipe the WOT curve is the most advanced and the curves retard as the throttle opening is reduced.

My mistake was thinking that maximising the power curve by adjusting the ignition on wide open dyno runs which makes for great dyno results and acceleration was the right thing to do. But apparently it leaves the ignition over advanced for reduced throttle settings and was what killed the engine at the GP and Kaitoke.

Talking about this with Speedpro, he suggested that on WOT the cylinder is scavenged well but at reduced throttle settings the cylinder was left with a lot of residual combustion and exhaust gas which greatly reduces the octane rating of the new charge. And with the advanced ignition timing this promotes detonation, hence the need for retarding the ignition when trailing the throttle, Speedpro's explination made sense to me.

[2T Institute]

The start advance is too much
0-1500 10
1600 30

[FastFred]

2T I wouldnt worry about the numbers to much, its the idea that when coming onto the pipe with a partialy closed throttle that the ignition needs to be retarded a bit.

I know its been talked about on this thread before but TZ350's is a pretty good explination.

[wobbly]

The 30* base timing on Robs is just where the rotor ended up, using the stock key position.
Its only effective below 300rpm, where the Ignitech uses the lobe position to spark up initially.
I have used 39* ( the limit of the software ) when converting a HRC - RS250, as the lobes were in an odd place.
You would think it would spit back, but was fine on the Salt speed record bike for example.

Frits alluded to issues with the Aprilia GP engines - they would deto badly on part throttle when doing smokies for the crowd, so the riders were banned from doing it.

[F5 Dave]

Yes I read that & was surprised that they couldn't adjust them for more retard when part throttle vs lower revs. Surely it wouldn't have affected higher rev settings & might have saved some damage. or am I missing something?

I am a bit concerned as I tend to take first session of the day quietly for a few laps. no tyre warmers, cold weather & tyres get reused many races so have to wear the crud off them.

[twotempi]

To Wobbly

The flag-ship Bears bike, namely the Britten, has Japanese clutch and gearbox internals.

Your RZ box therefore is fine .

[2T Institute]

I always use 5-15deg up to 1500 to make them easy to start, a NF4 kart we use 5deg up to 1500 no straps on wheel or pushers required.


RE BEARS racing think you will find the Aprilia RS250 is OK just because it has 'aprilia' cast into the cylinders and ignition cover well it is here anyway. Beware though they are not fond of 2 strokes.

FastFred
2T I wouldnt worry about the numbers to much, its the idea that when coming onto the pipe with a partialy closed throttle that the ignition needs to be retarded a bit.

I know its been talked about on this thread before but TZ350's is a pretty good explination.

Won't apply unless you have a TPS installed the curve is a 2D curve.

[jasonu]

To Wobbly

The flag-ship Bears bike, namely the Britten, has Japanese clutch and gearbox internals.

Your RZ box therefore is fine .

That is hair splitting and good luck convincing the BEARS guys too.

[Yow Ling]

I always use 5-15deg up to 1500 to make them easy to start, a NF4 kart we use 5deg up to 1500 no straps on wheel or pushers required.


RE BEARS racing think you will find the Aprilia RS250 is OK just because it has 'aprilia' cast into the cylinders and ignition cover well it is here anyway. Beware though they are not fond of 2 strokes.



Won't apply unless you have a TPS installed the curve is a 2D curve.

Bears dont allow RS250's or even Italian built NSR125's, John Britten probably had special rights as he was in the Bears inner circle

[F5 Dave]

. . Beware though they are not fond of 2 strokes.
. . .

Previous owner of a mates 256 engined GP bike found that back in late 80s. think he got bumped up to thier equiv of F1 when it became apparent his battles with the top 600(?) ducati was he was foxing & managed a last min pass to win. But if he made a mistake or got baulked he was able to catch up the distance in less than a lap.

[Grumph]

Bears dont allow RS250's or even Italian built NSR125's, John Britten probably had special rights as he was in the Bears inner circle

Correct - and as long as having his bikes at the Sound of Thunder got another 5 - 8 thousand through the gate he could do what he liked.
the point I was trying to make re Wobs masterpiece is that to be F3 legal in NZ he's got to convince the commisioners that the motor is based on a road unit complete with factory numbers..and I take that to be an RZ, or at least in the RZ family. The Banshee, a road motor ? Hmmm. Grey as i said.
Once he's gone down that path he can not reverse and claim it's american made therefore BEARS eligible. Catch 22.
The BEARS would make it run in F1 anyway...will it be competitive with the 1000 BMW's ?

[F5 Dave]

I think we've slipped into some loose arguing by accidental typing. I think it would be very easy to argue that the Banshee cases are so RZ derived that one could swap for the other with little consequence so they are essentially RZ cases, heck if you have to argue that heavily- go get some RZ cases. Indeed my RZ has almost the same barrels on it in 496 configuration.

There are some made from Billet cases that are A'merkiclown made, maybe that was the confusion. Either way no real drama & off topic here.

Wob has got clarification from commissioner that this is F3 (or pro whatever they call it now) legal, at least he said when we'd talked about it about a year ago.

[husaberg]

To Wobbly

The flag-ship Bears bike, namely the Britten, has Japanese clutch and gearbox internals.

Your RZ box therefore is fine .

it had a few more Japanese bits that that as well BTW depending on the stage of development......
THe MNZ also changed the rules to accommodate it in the superbike class as well remember..... They
even paid money to get it to events to get more bums on seat as well.

Err...but did you, have a read of the last page.....

Husaberg err..Jumped the gun on his quip there for two reasons...............

Gee It even had a nice picture an R rated one (for this thread anyway...)


Anyhow What about this.

Remember how Bears the Classics and the even the 4 stroke Nationals (Thumper nats) started because, there was no class to race their beloved bikes competitively.
Based on the pretext that less rules equal more fun so
I suggest 2 stroke Open formula race class.....

Twins Class only rule it has to have only two cylinders and be two stroke.
Singles Class only rule it has to be a 2 stroke with no more than 1 cylinder.

In the best tradition of the MNZ it could be self policing.

[TZ350]

Won't apply unless you have a TPS installed the curve is a 2D curve.

Yes, I am in the process of installing a TPS from an Aprilia RS250. My model of IgniTech has the choice of two 2D maps that the TPS can switch between or one 3D map. And then I want to make the det pickup/amplifier/headphone thing and get the det sensor working with the IgniTec.

The point I was trying to make with my post earlier was, contry to intuition (mine anyway) that when on the pipe, less throttle calls for less advance where as a 4-stroke is small throttle more advance.

[bucketracer]

The ica 100cc kart engines use diaphragm carbs with a choke size of 24mm. However by the carb exit they have diffused out to 27/28 mm. They bolt directly to the engine manifold and appear to diffuse out in area even more but hard to tell as the profile shape changes to match the reed block. This ibea carb is particularly good. http://www.out2win.com/catalog/images/ibeal5.jpg

The replacement world championship class is now called kf2 and these engines are 125cc with reed induction and powervalves. They use the same 24 mm carb design. the l6 carb shown here is homologated for this class. http://www.out2win.com/catalog/ibea.html

People are claiming 38hp plus for these engines. Clearly the carb is not holding them back too much!!!!

The 24mm carb rule is not the limit in horsepower development for a bucket that people think it is provided you use a diffuser. A 30mm at most area inlet port for a disc valve is all that is required with a nice tapered diffuser. Any bigger than 30mm will be a waste of time.

Some of these old posts are worth a re visit. High 30's hp with a 24 mm carb so long as it has a diffuser shape tapering out from the slide.

Taper Bored 24mm OKO, its 24mm at the very front, 29mm at the slide and 30mm at the manifold end.

Attachment 263055 Attachment 263056 Attachment 263057

TeeZee spent hours on the Dyno re discovering or at least understanding what Sonic_V meant by a diffuser carb and the angles involved.

The trick with the diffuser angles is to not make them to steep and have the expanding mixture becoming turbulent, breaking away from the walls and reducing the effective flow area inside the carb.

125 reed induction Kart engines making 38+hp with a 24mm carb and TeeZee has wrung 34 crank hp out of his engine.

So it makes you wonder, whats the point of continuing the 24mm carb restriction for F4 125 2-stroke Bucket engines....