RZ/RD 350 & Misc. 2-Stroke Tech BBS

I bought a Engmod2T license for my upcoming +4mm stroker build. I did some different setups playing with port size and timing. I cant seem to get any good gains with the +4mm crank. I can get decent gains by making the intake ports bigger on both stock and +4mm crank setup. I did a test with both spacer under cylinder and no spacer. No spacer and letting piston go +2mm over deck is the best setup. But still no good gains...
Red curve is baseline (bike current setup)
Black is bigger intakes
Green is +4mm crank

Is there any downside to make intake bigger? Rough running at lower rpm, increased consumption at cruise?

Bigger exhaust stinger on +4mm crank setup, more power from 6750rpm and up, but less peak

That’s very interesting I wonder how well it translates to the real world?

You may want to discuss that here:
https://www.facebook.com/groups/5510115 ... ?ref=share

Yamavarna wrote: ↑Mon Nov 06, 2023 10:43 am That’s very interesting I wonder how well it translates to the real world?

I find it very normal that more cc's need a bigger stinger

Sorry I was referring to the very dismal gains with the +4 crank over stock, not the stinger size and unfortunately I don’t have Facebook.

Yamavarna wrote: ↑Tue Nov 07, 2023 7:30 pm Sorry I was referring to the very dismal gains with the +4 crank over stock

everything else the same ? timings, compression, ...

I selected the wrong fuel for the bigbore setup, "regular" instead of 95 ron which was selected for the baseline. Now the simulated dyno gains look better. Compression, port timing basic setup is the same.. Dyno simulation is for one cylinder.

BLACK curve is baseline (bike current setup)
RED is bigger intakes
GREEN is +4mm crank
BLUE is +4mm crank + ex port to 1UA specs.

What powervalve curve and ignition curve are you using? What pipe too?

Ing. timing is 26 deg up to 6000rpm, then tapers down to 10 deg. at 9000rpm. Powervalve curve is for now 3 step (arduino based controller) . Closed until 5800rpm, then opens 80% ish, fully open at 7300rpm. Gives a nice "kick" at 7300rpm . Exhaust is modified F2 with different silencer.

Try something like 16-18 deg @ 9000 and fully open PV @ 8k

I did not remember correct regarding the ignition timing. Here is the ign. table. You have to divide values by 2, since Microsquirt ECU thinks 180 deg. rotation (2 magnets) is one full cycle. Just did the machining on the cylinder head yesterday to make room for extra stroke and set the desired chamber volume. I will post when bike gets dynoed to compare simulated/ real world results

I'm finishing an RZ350 with +4 crank in a FZR400 chassis build. I have 2 sets of stock cylinders and heads to start with, 29Y's and 31K's. PWK 28's and modified Lassak pipes. It will be a few months until it runs and I hope I can help with data of some kind as I don't have time or knowledge to run EngMod2T on my own. I've got JanBros program but don't really know how to use it

Luke

jumjum01 wrote: ↑Sun Nov 05, 2023 3:49 am
Is there any downside to make intake bigger? Rough running at lower rpm, increased consumption at cruise?

I might be reading between the lines but it sounds like your wanting more torque without raising rpm. Thats what i'm looking for anyway. One of the members here, Slinger, posted port specs axial and radial that would be good to test in EngMod.

The pdf in post 38538 here https://www.kiwibiker.co.nz/forums/show ... r/page2570 is what i'll be adjusting towards

edgefinder you are correct. Keeping the original powerband and lifting it up a notch is what i am after. Its my everyday street bike so I want to maintain a good strong midrange and it needs to be stable at cruise speeds too at small throttle openings

I have been playing with different setups in EngMod. So far the best settings to fit my needs are:
- Split the extra 4mm stroke (piston +2mm into cylinder head)
- Compression set at 6.54 @ 0.9mm squish
- Enlarge intake ports 4mil up and 4mm down in bore. (more power in all rpm, big gains)
- Enlange exhaust port down -2mm to match piston top at BDC (very small gains, might not be worth it)
- Keep exhaust port roof at 27mm (lifting roof makes more peak power but looses at mid rpm)
- Keep transfer ports as they are (I cant find any good gains modifying them)
- Ingition timing needs to be retarded to avoid detonation at high rpm
- Increase exhaust stinger size to avoid detonation.

I hope to have the bike dynoed in december if not too cold outside