ESE's works engine tuner

[SwePatrick]

only IF you can rev the 250 as high as the 125

Remember i earier built on a single cylinder engine.
this project i´m talking about now is a twin, so no problems with revving

[Frits Overmars]

The last Aprilia125 powerlimit was 52 horsepower (from memory) and had cost phantasillions to attain.
Let us enlarge all dimensions from that cylinder with cuberoot of two (= 1,26) and make a 250.
In that cylinder blowdown area will be these 1,26 squared (= 1.59) time so big and powerlimit for same state of art will therefore also be 52 times 1.59 horsepower equal to 83 horsepower.

only IF you can rev the 250 as high as the 125

Niels was correct, Jan.

The bore and the stroke of the 250cc engine are 1,26 x the 125cc-values, so the port areas are 1,26² = 1,59 x the 125cc-values.
And with the port timings of both engines being identical, the angle.areas of the 250cc engine are also 1,59 x those of the 125cc engine.
With the cylinder capacity of the 250cc engine being 2 x the cylinder capacity of the 125cc engine, its specific angle.areas are 1,59 / 2 = 0,794 x those of the 125cc engine.

If the 250cc engine is to have the same Brake Mean Effective Pressure as the 125cc engine, it must have the same specific time.areas.
The specific angle.areas are smaller, so the time factor must be bigger, i.e. the 250cc engine will give this BMEP at 0,794 x the rpm of the 125cc engine.
So the 250cc engine has the same BMEP at 0,794 times the 13000 rpm of the 125cc engine, and it has double the cylinder capacity. You do the math: it's 83 hp @ 10.320 rpm..

I could have kept this story a lot shorter: keeping the same BMEP requires keeping the same mean piston speed, and with a stroke that is 1,26 times as long, the revs need to be 1 / 1,26 times what they were

[TZ350]

Or change down to 3rd from high speed. That'll do it.

Worked for Speedpro.......

[SwePatrick]

I struggled for a while as my ego told me there are more power hiding somewhere.
I finally found it , my rearwheel bearings seized.
this makes the disc drag and ofcourse the resistance in the bearing.
Curve below show when it seized.

[wobbly]

After seeing the actual dyno run time , its way way too short.
You need to being doing the actual power inertia runs in a much taller gear , or take 5 teeth off the back.
If you could do a printout showing egt against rpm, you will see that the delta between run start and run end would show the pipes are not getting hot enough.
On my engine dyno settup I have to do at least 3 all gear WOT pulls , then go down to 4th and do the actual power logging run , to get fully repeatable results with real hot pipes.
Also as I have said a thousand times , use a race plug in a race engine , get some R7376 in there so you can read the ground electrode - but again the run time is too short to get any meaningfull result from that as well.
But , despite all that ranting , great result for the beginning of a project.

[SwePatrick]

I know of all that, but i have developed this problem: i don´t have the guts to spin my roller at above 2500rpm, i have balanced it last winter and it feels really good, but i need to overcome the fear, get some trust, babysteps and i´ll get there, never any wrong to have some caution
The pulls are about 4s long as for now, i want them to be about the double.
I need to fix my brake on the roller, i used to use it to make a steady state pull to raise the pipetemp before a powerpull.
I tried with the brake(when it was working) hold the rpm at say ~10000rpm for about 5-10 seconds.
Then rapidly coast down to about 7000rpm and start a pull.

In my other 212cc kawasaki that gained a LOT of power.

[F5 Dave]

I always did some all gear runs (boohoo) when I had the dyno.. more often than not on a new bike taught something . Quite often to do with fuel supply.

[wobbly]

SwePat - do the simple calculation for Hoop Stress on the flywheel.
This will tell you if your balls are telling you the right thing.

[dutchpower]

What is the material off your roller drum SwePatrick

[SwePatrick]

SwePat - do the simple calculation for Hoop Stress on the flywheel.
This will tell you if your balls are telling you the right thing.

As my roller is quite long(870mm) it is quite hard to balance out the dynamic unbalance, but i´m really close actually.
The diam is 292mm with 60mm shaft through.

[TZ350]

[SwePatrick]

What is the material off your roller drum SwePatrick

It is steel, 870mm long with 60mm shaft through, and three sideplates(one in the middle to hold the shaft from bending, and to get inertia) 40mm thick.
I also filled it with concrete(it´s been debated before in this thread) this to also make the roller 'dead' and don´t create any harmonics in the shaft.
The walls in the roller are 25mm.

The dyno is built so if something happens the roller is 'caged' and probably won´t be any problem.
But, my mind is my problem, it´s like chasing cure for vertigo.

[andreas]

I hope he remembered to chamfer the port this time.

[Muhr]

And i aim for about ~80 to the wheel, so if it all goes as planned i´ll be in the nieghbourhood of 83hp on the sprocket as they measured.

Is not 53.21nm at 10567RPM 80.07 HP

[jfn2]

Could someone tell me what this ports are used for? I see no reason for them, or how they work. Thank you. Jeff