+4mm crank gains

[edgefinder]

Slingers specs are in a post near bottom of first page. He was doing work for others, posting a lot of good info like how to do the +4 mod so when he posted his 70hp specs I saved them. He does call it a race spec and its not for a +4 stroke but i'm more interested in the angles he chose. The flatter roof angles are what I want to try and i'd like to know what engmod thinks of it.

viewtopic.php?f=1&t=13559

[jumjum01]

I dont know the stock roof angles, but in the RD350 file from engmod (Niels) the roof angles are
A: 0 deg.
B: 15 deg.
C: 60 deg.
I think A is wrong because its seems angled and not straight...
Changing angle A from 0 deg to 20 deg. made a whooping loss of 0,2HP at all rpm

[MK]

- Enlange exhaust port down -2mm to match piston top at BDC (very small gains, might not be worth it)
- Keep transfer ports as they are (I cant find any good gains modifying them)

I once ran engmod sims that showed around 1.5-2 HP gains when matching the lower transfer port edges to the new piston position in BDC.
Save the work to do that for the exhaust port.

[jumjum01]

These are the gains from enlarging the ex port down to match piston top at BDC

[edgefinder]

Alright I stumbled through getting a pic to post.

These are the Yamaha cylinders in my shop. RZ500, RZ350, DT50 3BK sold in the states 88, 89. I have a TZ500 cylinder but its still in Japan. I have an RG400 project never run and all the rest of my 2 strokes are mx. Maico and KTM. I know the RZ350 exhaust port is probably the biggest restriction to power but I'm pretty sure that if the intake and transfers were more accurately shaped that although it might not show up on a dyno or sim it will probably feel better riding the bike. Like you said about cutting the ex port bottom to match piston at BDC not showing much in the sim I want to keep cutting the cylinder wall to a minimum.

[jumjum01]

Here are the final EngMod calculations. The rd350 project file I got was apparently for a heavy modded bike. Having measured all the components of my engine and put in that data, here are the final dyno simulations.

Current bike:
simuated: 31.63 x 2 =63,26 HP in motor /1.11 = 56.99 rwhp
real life dyno (SAE) = 55.5 rwhp

4mm stroker bike:
simuated: 34.79 x 2 =69,58 HP in motor /1.11 = 62,68 rwhp
real life dyno (SAE) = ??? rwhp

% gain i engine cc 355cc -> 382cc = 7,6%
% gain in HP 62.68/56.99 = 1.099 = 9.9%

My guess is that I will end up with around 61 rwhp (SAE)

[edgefinder]

If it dyno's in the low 60's hp with a small amount of work and it has a linear power increase throttle in hand like sim shows then you've done good work. Your early sims where you weren't getting any change after adding 4mm to the stroke got me thinking it will take some effort to learn all the variables in the program to get sims and dyno to agree. I hope dyno time is cheap. I had an RZ350 when the SV650's came out and they were pretty equal in speed. I'm anxious to see how the new ZX400-4's compare.

I'm gathering all my stuff in the basement so I can collect and compare data I have. I'd like to see how its input in the RD350 project file. I got a tuning manual from Martin, MK here for my RZ500 many years ago. He does one for the 350 also and it has lots of useful information. How bout it Martin, is it still available? I want to show how I measure and modify ports but It might take a while to get started.

[MK]

I've been busy with other important things in live, so the 2016 version would be still available, if it weren't for my printing shop closing down a month ago.
Honestly I was too lazy to source another one, yet.

The 500 manual is available for download here:
https://www.rd350lc.de/downloads/MK-Dok ... Seiten.pdf

[jumjum01]

Dyno time is not that expensive. The build is now complete and bike has had initial startup, runs fine at idle, and has good 125psi compression on both cylinders. But due to no winter ensurance I cannot ride the bike. Outside temp is now 0 deg. celsius and needs to be at least 7 deg. to do proper dyno testing, so some patience is required
What stinger size is "normal" to run on +4mm stroker? Engmod seems to make more overall and topend power with bigger stinger diameters, but that seems opposite of real world??

[jumjum01]

Today I had the RD383 dynoed. Dont know if I picked the wrong date, but temp was 6 deg. celcius and 99,6% humidity. The rented box trailer lock would not open and I had to use my hobby trailer to transport til motorcycle to the dyno shop. When I got back the front disc brake had allready started to rust, due to wet and salty roads.
Anyways, the RD was dynoed with my stock fuel map (EFI bike) +8% fuel in mid-top rpm. It made 59rwhp SAE, only 3,5hp more then last dyno run. Dont know if weather condition and or "temparary" fuel mapping was to blame
But looking past the top rpm HP and looking at the complete rpm scale the bike made decent gains through the scale. Since I cant overlay the 2 dyno sheets, here it the gains over previous dyno run.
4500rpm: +3hp
5000rpm: +2hp
5500rpm: +1hp
6000rpm: +2hp
6500rpm: +3hp
7000rpm: +3,5hp
7500rpm: +6hp
8000rpm: +4hp
8500rpm: +3,5hp

The bike was dynoed with both 20mm stinger insert and no stinger insert (24mm). Clear winner by 2,4 HP was 24mm.

[jumjum01]

According to Engmod air/fuel ratio is pretty signifacant. Good for 2,6HP on 11afr vs. 12afr

[jumjum01]

I made some expansion chamber exhausts to move some power up the rev range to max at 9300rpm and did a dyno run.
Here are the results, the red baseline is with f2 pipes and stock crankshaft. Blue is 4mm crankshaft and custom pipes
Thanks to MK for his pipe building guide

[MK]

The dip at 8.5k could be cured a bit by more ignition advance in that range.
And fiddling a bit with the PV fully open rpm. Try 9 - 9.25 k.

[jumjum01]

Thanks MK. More ignition advance will get close to detonation limit. PV is fully open now at 7300 rpm. I will try playing with later full open PV next.
I might get more dyno time testing a set off Jollymoto GPs pipes against stock F2s.
Damn it is a big job building pipes but a fun challange

[Yamavarna]

What method did you use for welding these pipes?