APS/G 250

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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

I've been working on some specific 300cc engine stuff.

I am making new pipes as all my existing Exhausts are all made for a 250, so I can get a bit more power with the correct pipes.

This Engine design software is based on data that two engineers from the Aprilia (2 Stroke) Works Team have shared since all GP Bikes went to Four Strokes in 2012.

These pipes are made by making a series of cones based on the measurements in the 3 Stage Diffuser Chart and welding them together.

I think I've already said that the RGV engine has some inherent restrictions, mainly the short 50.6mm stroke, that limits the area in the cylinder that can be used for the ports.
That also influences the shape of the internal ducts in the transfer ports, they are upside down L shape to suit flat top pistons in the 250.
The 300 has dome top pistons so a radius shape is more efficient and difficult to achieve with my limited level of porting skill.

Having said that, it still has the potential to make good HP per CC for a small production engine. Some of the modern Racing 2 Stroke design can still be applied to my engine in the future.

Next step is to run this through the Ian Williams MOTA 2 stroke Engine Simulation software (once I get a working XP Laptop), if that shows an improvement, I'll cut, roll, weld, fit, then back to the Dyno.


Pete :)
Last edited by AuotonomousRX on Sat Aug 07, 2021 9:01 am, edited 1 time in total.
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BONES
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Re: APS/G 250

Post by BONES »

Hey Pete
Have you thought about using a single diffuser cone?
Isn't the theory the single cone will give you a stronger returning wave at the expense of a narrower power band so hopefully more HP?
If the RPM drop at each gear change is not too much it should work.
I recently finished a set of pipes for my TZR250---- it's a big job

cheers Bones
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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

BONES wrote: Sun Jul 25, 2021 9:03 pm Hey Pete
Have you thought about using a single diffuser cone?
Isn't the theory the single cone will give you a stronger returning wave at the expense of a narrower power band so hopefully more HP?
If the RPM drop at each gear change is not too much it should work.
I recently finished a set of pipes for my TZR250---- it's a big job

cheers Bones
Hey Bones

Yep, that was my preference (this software gives that option) but having a single diffuser type pipe made the pipe too long and it won't fit on the Bike.

I don't know about the Theory, I was going single diffuser as it was simpler to build. As far as Theory stuff, most of it is beyond me, I'm just following what the the Aprilia engineers found.

I agree, it is a big job, it is just a thing I have to do now the engine is 300cc. The pipes I have that work "ok" with the 300, don't fit on the Red Bike either.

As I said, next step is to run these designs through the MOTA Engine simulation and find the best compromise between safe peak RPM/HP that fit. :lol:

I used MOTA on my 250 build and the results it came up with matched, to about 2 percent, my actual Dyno curves and test run data, so I'll stick with it.

I'll post what I find.

Cheers

Pete :)
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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

Exhaust update: The earlier exhaust has been updated to a simpler "Single Diffuser" design with the same rpm/output. (thanks Bones)

I made an operator/data entry error with the software as the earlier results did not make sense. (The three 1/2/3 diffuser design options did not line up and they should have.)

All good once I re read the instruction manual :?

Image

Pete :)
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Stayt`ie
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Re: APS/G 250

Post by Stayt`ie »

hey Pete I see the speed of sound setting is at 560ms, is that a default setting ?, or is it your setting based on exhaust gas temperatures ??
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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

Stayt`ie wrote: Wed Jul 28, 2021 11:51 am hey Pete I see the speed of sound setting is at 560ms, is that a default setting ?, or is it your setting based on exhaust gas temperatures ??
Hey Ron

The default is 587ms, that is for the Works Engine which is more efficient than my engine.

The instructions suggest a lower number based on the characteristics of the engine.

It is a best guess, on the high side, based on percentage difference in BMEP, and juggling rpm/peak HP/fit the Bike.

As I said I am not up on a lot of the Engine Dynamics and this software is "relatively" basic compared to others around, but good for free stuff.

I am still going to keep making adjustments, and it will be interesting to see how they end up, I enjoy going through the design process.

Thanks, more food for thought.

Pete :)
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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

The other part of this is actually making these Pipes.

As this is a series of Cones welded together here is the software I use to make the paper templates I print out.

Image

Pete :)
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BONES
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Re: APS/G 250

Post by BONES »

Hey Pete
Good to see you found an error. The tuned length should stay the same with single or multiple cone diffuser.
You can design and print the cones to bend in MOTA. Set the desired angle and number of pieces and press go.

cheers Bones
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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

BONES wrote: Sat Jul 31, 2021 10:19 pm Hey Pete
Good to see you found an error. The tuned length should stay the same with single or multiple cone diffuser.
You can design and print the cones to bend in MOTA. Set the desired angle and number of pieces and press go.

cheers Bones
Hey Bones

Yep it's a learning curve.

I have the earlier MOTA and it won't run on my current computer, needs XP or Win7, and my old Laptop that I used does not work anymore, all good.

This gives me a good excuse to get the the latest 6.3 Version. :lol:

Pete :)
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Stayt`ie
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Re: APS/G 250

Post by Stayt`ie »

come'on fellas, set square and compass are a lot cheaper :lol: ,,

last century when doing my apprentiship, marked out and cut by hand 100's of lobster backs of various angles to suit pipes up tp 3' in diameter (lagging on steam pipes in a sugar mill) :)
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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

Stayt`ie wrote: Sun Aug 01, 2021 8:19 am come'on fellas, set square and compass are a lot cheaper :lol: ,,

last century when doing my apprentiship, marked out and cut by hand 100's of lobster backs of various angles to suit pipes up tp 3' in diameter (lagging on steam pipes in a sugar mill) :)
Hey Ron

I do have both of those, but I want the pipes to actually come out something like they are supposed to :lol:

Pete :)
Still trying to decide if I am a procrastinator

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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

For all of you reading this post, and are wondering about 2 strokes, here is a little animation that might be helpful.

This is a Crankcase Induction, Reed Valve 2 stroke engine similar to my engine.

While this is air cooled and mine is liquid cooled, they both work in this same way. (There are other types)

Image

Pete :)
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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

This entire thing has been a steep learning curve, despite their physical simplicity, 2 strokes are complex things to modify and have evolved a lot since I raced and tinkered with my Short Circuit/Dirt Track CR125M in the mid 70's, and like all engines the HP/cc ratio has also moved on.

Apart from the "newer" Reed Valve/Direct Crankcase Induction and Exhaust Port "Power Valves" part of the equation, the electronic tuning side has also opened up.

This other big change is that Ignition Timing and the Power Valve activation became adjustable with basic "ECU" modules also available.

I use this unit, the Zeeltronic PDCI - 20V, designed for the RGV VJ22 engine as it has a Throttle Position Sensor (TPS) and this allows me to modify the Ignition timing and Power Valve opening to suit the engine modifications I make and the fuel I use. It has two maps that are switchable.

Here is a screen shot of the STD Aprilia RS250 Ignition Map 1. Map 2 is a custom map I tried but did not suit my engine. It makes a lot of difference being able to change these so I can get the most out of the real limitations of the RGV engine.

For the 250 modded engine I used the RGV Kit Ignition Curve that also came with the unit, and made a few tweeks to suit the Sunoco Supreme (reduce the advance) and power valve opening for the Jolly Moto pipes (delay fully open rpm point.)

Now with the 300 engine and Pump Premium Unleaded I've gone back to the Std maps and will make some changes based on what I learned tuning the 250.

Eventually I hope to run both Gas and Fuel Classes and I can change Fuels and switch from Map 1 to Map 2 to suit.

Image

Image

Pete :)
Still trying to decide if I am a procrastinator

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AuotonomousRX
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Re: APS/G 250

Post by AuotonomousRX »

Apart from the Bike/Engine stuff, a part of Speedweek that is not often talked about is getting your weapon of choice there in one piece.

My Trailer has been a work in progress.

After three years I've finally extended the rear of the Trailer so the Long Red Bike fits in properly.

This also rebalances the trailer after the angled front extension I did in 2011 so the Trailer was not like towing a parachute (2010). :shock: :lol:

Image

Next on the list is a new DIY pit shade.

Stay safe

Pete :D
Still trying to decide if I am a procrastinator

Pete :?
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