ESE's works engine tuner

[wobbly]

Sure is , with A maybe a little lower and C a little higher as the trend seems to be less stagger differential on the C , than that of the A/B delta.
But as always its getting the Blowdown and Transfer STA to match that is all important.

[philou]

I am curious to try my new 45 degree contra-angle

I think it must be practical for working the vertical angle of the port.

[wobbly]

I posted this chart on my Wobblypipes FB page and was asked several times if the idea works for any racing twostroke .
The anwer is yes.
The method starts with first finding the best power egt just short of deto with a specific weather . I do it on the dyno , but a first data point can be gained at the track , where you lean it down to the point where
the next smaller jet does not give any rise in egt ie the deto limit.In my specific case of Dellorto jets on a TM KZ engine I would expect to see a 20°C rise in EGT when using the usual jet size split ie dropping from a 160 to a 158 size, as long as the jets are
pinned as accurate. Any less than this EGT increase and we are on the deto limit. Once you
have created a set of pinned jets in one size increments ie 160 down to 159 the EGT
increase should be 10°C per size. This enables very accurate and safe tuning during the day
to stay bang on the desired best power numbers.

Then you would need another couple of weather/jet points ( gained from a RAD app on your phone accessing the nearest airport weather station ) where you hit the same egt on the day.
Once you have 3 points you can draw the reference line thu them.

The scale of jet size along the bottom can be whatever the carb uses - but for it to be reliable the jets must be guaranteed accurate by being flow/time tested or using a jet pin diameter set.

EDIT - added temp rise targets for egt.

I did the first chart over 10 years ago , but have used the same reference line ever since , with different engine versions /mods and tune , the lines are always parallel for the Dellorto jets I use.
In this kart chart the top line is a TM KZ10C in OZ on 100 octane race fuel.
The middle reference line is an older KZ10B on 98 pump gas in NZ
And the bottom line is a TM R1 on C12 110 octane in USA - the only difference is the combination of tune and fuel quality.

Once I have the tune line I can go to any track , dial up the weather combination on my phone , and fit the perfect jet for that RAD on the day.
Usually I would change jets 3-5 times during the day , simply keeping the same egt - tracking any weather changes in temp , pressure , or humidity.
I use Density Altitude as it has an expanded scale over RAD.

All this is doing is maintaining the optimum bsfc for the engine/fuel ie - less air density = less fuel needed = less power generated = smaller jet.

[Roflhat]

Interesting with the graphs and a clever solution. Do you find that at higher temperatures/altitude you may need a larger main jet to aid cooling? Been reading up about it for Bonneville, most folk say the change in jetting in reality is much smaller than the calculations would suggest

[wobbly]

The thing is these data points are not calculations , each is taken from hitting the optimum egt at a specific Density Altitude,
Most of the KZ10B was done at sea level , the Vegas R1 altitude is 650M , but Density Altitude uses Temp , Air Density and Humidity for the data points and as actual altitude
affects the Air Density the airport calibrated weather station sends out by default.

[Roflhat]

I like the idea a lot, might try do the same for mine.

Got my suzuki running today, definitely feels like it has more power but it's quite intermittent. Going to change plug and try again, used plenty 2 stroke during engine assembly. What sort of jetting would you expect for this? GP100 with tranfers opened up as per Rob's recipe, standard carb and exhaust (with cone welded inside). Currently 107.5 main. Will get it on the dyno soon once the ignition setup arrives but would be nice to have a rough idea

[TZ350]

I like the idea a lot, might try do the same for mine.

Got my suzuki running today, definitely feels like it has more power but it's quite intermittent. What sort of jetting would you expect for this? GP100 Currently 107.5 main.

For our GP125's running 24mm carb's we were around 135mj.

For the 100 with its 22mm carb. Maybe 120ish would be my guess but take as many different main jets of all sizes as you can get hold of.

On the dyno, take big steps, high and low to find the likely area to zero in on. Start with going high first.

Adjusting the needle clip may be required with changes in main jet. Ie a much bigger main jet may require lowering the needle to keep things throttling well.

[F5 Dave]

So have you calculated your peak power revs with the modified pipe?

What was ignition? Not worth wasting your time on dyno if left std unless revs are real low, and that would be a waste of power anyway.

[Roflhat]

Cheers, have ordered a big pile of jets so I'll have 105 up to 135.
Pipe is designed for ~10k rpm. Currently using the electronic ignition kit, Rob is very kindly sending me a setup so once that's on will get it over to the dyno

[Roflhat]

Was playing with some free programs for pipes, I think mine is not too far away from these given the restrictions for class

Drew them up in Rhino quickly


I've got a file for a carb housing spacer if anybody wants too, I 3D printed mine

[F5 Dave]

Any curve he sends you will be geared towards significantly more revs. That will keep the power quite modest. Maybe within class limits that will be competitive. I wonder for top speed if a pwm power jet project would increase revs/spread and be worth pursuing as a high priority.

[Roflhat]

I've got another standard exhaust sitting in the shed, I can cut it up and put a cone further up inside so it'll be suited for more RPM. I have to run the standard carb, unless you mean adding a power jet to the standard carb?

[husaberg]

I've got another standard exhaust sitting in the shed, I can cut it up and put a cone further up inside so it'll be suited for more RPM. I have to run the standard carb, unless you mean adding a power jet to the standard carb?

Come countries had the same exhaust for the GP100 and GP125.
might be worth investigating if the GP125 one is bigger dia
https://www.cmsnl.com/suzuki-gp125-1...sy_1430139671/

looks like the early Gp125 and the later GP 125 headers are potentally different sizes as well judging by the parts numbers although it might be materials

https://www.cmsnl.com/suzuki-gp125-1...as_1418111010/

https://www.cmsnl.com/suzuki-gp125u-...as_1418111020/
gasket same part as a RGV250.
I would bet the Header is double skinned or at least the later one might be.

[F5 Dave]

I've got another standard exhaust sitting in the shed, I can cut it up and put a cone further up inside so it'll be suited for more RPM. I have to run the standard carb, unless you mean adding a power jet to the standard carb?

Adding a power jet with a solenoid, perhaps like Robs experiment a few pages back. I made one from parts from a KX 125 carb which was fitted std when I couldn't get the carb to fit in the space. Had other things to chase so never had it working properly in anger. But being able to control turning it off should extend your rev range.

At some point working with std pipe the header/diffuser will be quite long compared to the length of the pipe required for say 13,000rpm you would prefer to spin. Find someone to model in engmod might save you going in wrong path given such restrictions.

[Condyn]

I am curious if somebody could please point me in the correct direction, regarding the best possible coolant path in a 2 stroke. I know I have stumbled across some info on this, but I cannot find it now. Thank you.