ESE's works engine tuner

[wobbly]

I have not done a 65cc engine in the sim. But a 50cc Athena race engine making 20Hp crank had a 16mm nozzle, and a KTM 85 race ( ie not MX ) with 38Hp crank had a 20mm nozzle.
Both optimized as 0.8 Mach in the nozzle.

[Flettner]

Im running 2x 17 dia at the moment, peaks at 11,300.
So far detonation is not an issue.
Unfortunately its a heavily under square engine at 48 × 58.
Will be rectifying that with a subsequent build, engine after next 54 × 55 , vairable disc valve, water cooled, twin blade powervalves (to suit the twin exhaust ports).

[F5 Dave]

Wobbly, what pipe restrictor dia would you imagine a 65cc (say a KX65) would have?

Edit, I see Frits has a calculation, D5, but I need to know the HP first. Off to the dyno I guess.

Oh lordy, are we talking about your twin pipe AG? The area of two xx mm holes vs the area of a single hole is what might be worth looking at?

[wobbly]

I think you would easily get away with 2X15mm in that.

[Flettner]

The pipes on the AG are a bit 'Dad and Dave' , the second bend on each pipe were hydroformed and not very well at that
Not accurate at all, so the next set of pipes have all been formed in press tools (many press tools). Ill make the restrictor part of the pipe interchangeable so I can experiment with different sizes.
After the restrictor (welded in 17mm section at the moment) the tail pipe opens out to 20mm out through the mufflers.

[diesel pig]

Leaving aside Throttle position sensor and solenoid controlled power jet issues* Would a 28mm Diameter or 36mm Diameter Carburetor be better from a Max Power vs Power band width point of view(far more important in circuit racing than people think). The 2 stroke in question would be hopefully a well tuned F4 Bucket 100cc.

* I think there are things that can be done for both things on Carbs that do not have them. Mind you if I am right about those things it brings into the Question those OKO copies of PWK 28mm over bored to 30mm,32mm and 34mm but are OKO's any good?

[wobbly]

Its not just a question of what carb and what size , its far, far more nuanced than that.
Take for example the very best of the 50cc FreeTech class engines - where essentially " anything goes ".
Many use a 30mm HV Lectron , this would appear to be extreme excess at a first glance, as when using a 30mm Dellorto carb a KZ 125 engine is capable of around 50 Hp at 13800 rpm.
But the HV Lectron has a 26mm venturi behind the slide , thus at part throttle it appears to the engines inflow as a much smaller diameter , but at WOT the carb is not in any
way the limiting factor.
At the outer extremities of what is possible, our old mate the Devil is very firmly in the detail.
And that my friends, is exactly what EngMod is capable of revealing to all and sundry.

[Frits Overmars]

Wobbly, what pipe restrictor dia would you imagine a 65cc (say a KX65) would have?
Edit, I see Frits has a calculation, D5, but I need to know the HP first. Off to the dyno I guess.

Neil, note that the calculation of restrictor diameter D5 in the FOS pipe concept is based on crankshaft horsepower, not rear wheel power. So you'd need to multiply the power you measure on the dyno by about 1,15. Then the restrictor would match the power the engine is making now.
But the purpose of pipe improvement is to get more power so don't hesitate to be greedy and calculate D5 for a generous horsepower number.
Too large a D5 may hurt the power but it won't hurt the engine.

[wobbly]

Hey Mr Pig , regarding the carb question again , I am tending to the 36mm carb if the rest of the project is dialed into being used for roadracing.
The point here is that using the TPS and the Solenoid allows a longer pipe design , that will then overev easily by switching of some fuel just past peak.
If its as I suspect a WankStriker version , tap out the powerjet tube and machine out the wings in the bellmouth floor.
These work well in an MX scenario for throttle response below the pipe , but have a huge loss of airflow CFM when compared back to back with say a PWM.
You can tune the intake length slightly long to pump up the front side , and one of those sexy looking carbon fiber add on bellmouth extensions would help there as well.

[Grumph]

Any advantage to using a Smartcarb over a Lectron ?

Any comment on the Smartcarb generally Wob ?

[diesel pig]

Any advantage to using a Smartcarb over a Lectron ?

Any comment on the Smartcarb generally Wob ?

I will back that up, there general Smartcarb sexiness and easy way of tuning them(as I have seen in some youtube video's) that has got me very interested in them. But do you lose out on power at the very top of the rev's? or power band width? using them.

My first name is the same as Flettner's so by all means keep calling me Mr pig(i don't mind) it avoids confusion.

[wobbly]

I have fully tested the SmartCarb in two very different applications.
Technically the modus operandi of those and the Lectron are very similar, but the latest Lectron's now have alot more adjustability and their patented new needle is a real game changer.

The Lectron in HV series is better than the SC's egg shaped venturi in throttle response but the big unsolved issue with the SC is that it's all but impossible to get a pair to jet with equal EGT on a twin.
There is simply not enough adjustability in the " main " area of the needle , and there is an insufficient number of close tuned needle variations available - be it for a twin or not.

The Lectron has a simple powerjet , be it with a screw needle or jet swaps , so its dead easy to get a perfect WOT tune in tiny EGT increments.
I can easily keep an engine within 10*C of its perfect best power EGT on any day using the Lectron 's PJ - that tuning I found is impossible with a SC.

[Grumph]

Thanks Wob. Interesting re repeatability between carbs on a twin.

Maybe the "hand made" aspect counts against them here.

[wobbly]

Its not repeatability between carbs , its the crank windup in early TZ and case/manifold/pipe variations in later TZ that need split jetting and or split timing.
You simply cannot get small enough variation in the SC needle setting to equalize the EGT.
A couple of jet sizes in a PJ can fix it instantly.

[koenich]

Mind you if I am right about those things it brings into the Question those OKO copies of PWK 28mm over bored to 30mm,32mm and 34mm but are OKO's any good?

The OKO's are good in my experience, been using their PWK 30 since years on my 50cc (with Keihin jets and needle). However you can't bore them to much more than 30 mm, otherwise the slide won't have guidance and the wall thickness towards your manifold gets very thin. So if you are looking for sth > 30 mm dia, you need the bigger body...