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Post by drc174 on Mar 10, 2017 7:08:20 GMT -5
What is notable is that the XL box exhaust is capable of supporting higher port times and a higher blowdown, so if you can measure your timings, raise your exhaust port up to a 60deg difference between intake and exhasut. If you want to get some gooood power out of the polini go and push it to 175/115 or 180/120, maybe witha spacer underneath and milling off from the top to adjust the difference
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Post by niz76 on Apr 2, 2017 12:21:58 GMT -5
After getting some riding in the last few weekends with the S.I.P. Road XL exhaust I think I'm finally ready to make this statement; I'm not impressed!drc174, I've been thinking a lot about exactly this port timing subject with this exhaust... Here's my experience with the XL- I've found it to have greater torque at a lower RPM than the cheapy expansion chamber (no surprise there) but after a few rides on the open road it just seems to run out of steam much too quickly. Oh, and I've finally experienced that "gap" between 3rd and 4th gear that I often hear of. I'm struggling a bit to describe my experience and exactly what I don't like about this exhaust vs. my expansion chamber experience, but I'll try... With the expansion chamber (remember this is about the absolute cheapest expansion chamber you can get for a Vespa. It's a ScootRS expansion chamber. Lots of Vespa folks seem to despise their products but I've found descriptions in other places of the web where folks say they were quite happy with it. I can confirm that although it's a cheapy clone- I do like it. It seems to fit my riding style, or rather maybe I've just adapted to it over time?) The only real drawback that I've found with it is when taking off in 1st gear. Of course it's pretty dead at low revs so I've really got to rap on the throttle before letting out the clutch and then kinda feather the clutch and keep the revs up while I take off. (I feel like I'm being hard on my clutch plates but still seem to be performing just fine after lots of miles.) It can be a little embarrassing when you let the clutch out at too low of an RPM lol- the scoot is now just put putting across the intersection as you either wait until the revs build up enough under load to get you going, or you re-pull the clutch back in, rev it out, and then often release the clutch a little too quickly because you're in a hurry and suddenly this "slow ass scooter" that was just struggling to build up speed launches into a wheelie and tears ass outta there beating everyone else haha. I love this scoot! After takeoff the expansion chamber is a true pleasure to drive with. It has great speed (awesome sound too!) and I've never experienced this problem with too-far-of-a-gap between 3rd and 4th that I keep reading about. I think it's because the revs are up nicely when I change gears and I always seem to be in the power band. Shifting from 3rd to 4th has never been an issue for me. Oh, and last but not least- I rarely EVER ride full throttle. Full throttle with the ScootRS expansion chamber is around 70 mph+ so there is just rarely ever a need to... Now for my experience with the S.I.P. XL: Takeoff is now a breeze because there is more power available at lower revs. There's definitely more torque too! Wheelies are now even easier but now they never happen unexpectedly due to the "expansion chamber launch" I described above... The sound of my scoot is now unimpressive. I no longer get the "dang that thing sounds nice!" comments when I pull into a store or whatever that I got with the expansion chamber. That raspy pingy poppy rumble is gone with this exhaust.  That's ok, I can get over it as long as the performance is there, and the performance is there- during takeoff. At riding speeds not so much. I now find that this exhaust seems to run out of steam much quicker. It's out of breath at 4200 RPM's in 3rd gear when I shift into 4th and there's that "gap" I keep hearing about! Yup sure enough it seems like the gap between 3rd and 4th is very large, the RPM's drop and now I'm not in the power so much and there's a bit of a lag until I gather up the speed again to cruise in 4th gear. Full retard happens at 5k RPM with the Kytronik map I'm using and this exhaust barely seems to ever be above that unless I'm in a long open straightaways where I can "stretch it's legs". She doesn't have very long legs and that's a bummer. I've found myself at WOT a few times now and not impressed. Not nearly as fast now... So, what to do? Do I tailor my setup to the S.I.P. XL and adjust my timings (they're pretty low, IIRC around 162 exhaust duration? can't remeber exactly and don't feel like going back through here to confirm but they're low). I am using a thicker than stock base spacer to raise the durations a bit though. I've been planning to port this Polini cylinder eventually but I've been enjoying riding it more than I want to tear back into it again haha. Or do I just go back to the expansion chamber that always put a smile on my face when riding this ol' beast? Now that I've written it all out I think the answer is obvious! Hey I'm glad I got to try this exhaust though. Now I know for sure that I'm just an "expansion chamber guy" and I can move forward with 100% certainty of my decision. Now this doesn't mean I'm 100% satisfied with my setup and cheapy ScootRS pipe, the opposite in fact! Now I'm starting to eyeball some other expansion chamber choices and I'll probably just try to offload these two exhausts for cheap... So more building and modding to come! Oh, btw I wanted to mention that I installed my new shocks and WOW what a difference! I shoulda did this a long time ago! Now it's not so much a scary squirrly white knuckle ride when there's a bit of wind. The scoot is totally planted now and so much more of a joy to ride.   |
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Post by 190mech on Apr 2, 2017 13:23:02 GMT -5
Pipes all the way!! Jan Thiel once did a test with the Aprillia RSA 125,this engine produces 54HP in top tune,,he removed the pipe and rejetted the engine till it ran correctly and dyno'ed it again,,17HP was all it would do!!  |
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Post by Lucass2T on Apr 2, 2017 13:34:30 GMT -5
You can lower compression to widen the powerband and regain some top end power.By adding a thicker base gasket you lower compression and raise port timings at the same time, which is what you want. You'll lose some low end torque though...
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Post by drc174 on Apr 2, 2017 18:34:10 GMT -5
You really want atleast a blowdown of 30 fir this pipe, so if you got lwrs say a chil 116 intake get to 176 at least. Your carb doesnt really feed into the whole low rpm thing either but it feeds the xl well. Put 1.5mm underneat the cyl and take 1.5 from the top and you should be closer to what you wantt
Also open the exhaust port to at least 67%
Pipe soundsare ok but i love the low 1200rpm rotary put put put the box pushes with a box
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Post by niz76 on Apr 9, 2017 11:13:48 GMT -5
Still haven't touched this cylinder (or even the broken piston piston for that matter) and been racking up the miles! Another hobby has sunk it's claws into me (drones  ) and I took the opportunity yesterday while my ladies were at a Hunter Hays(?) concert and rode 3 hours round trip to go buy yet another drone hehe. I barely even keep an eye on the temp gauge anymore as my trust has grown deeply in this scoot the last few months. It happily burns through tank after tank of fuel with no issues. Just frickin love this thing! The new suspension is a godsend. Like I said b4, I should've upgraded them long ago! It's been ridiculously windy here in the Tampa area for weeks now and I feel so much safer plugging along at 60 mph now. With the old stock shocks it really was a white knuckle terrifying ride in the wind gusts. So no real updates- just enjoying riding for now and all along planning the cylinder porting/modding in my head....  Scoot on! |
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Post by 90GTVert on Apr 9, 2017 13:33:13 GMT -5
You need one of those drones that follows you and films you. It'll need a BVK (Big Volt Kit) so it can keep up with the scoot.  |
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Post by Lucass2T on Apr 9, 2017 13:47:17 GMT -5
You need one of those drones that follows you and films you. It'll need a BVK (Big Volt Kit) so it can keep up with the scoot. That would be awesome. How fast can those drones go you think? |
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Post by 90GTVert on Apr 9, 2017 16:13:35 GMT -5
You need one of those drones that follows you and films you. It'll need a BVK (Big Volt Kit) so it can keep up with the scoot. That would be awesome. How fast can those drones go you think? I thought it was 20-30MPH, but THIS guy says it was going ~45MPH. I'm sure you could make one outrun the scoot if you try/spend hard enough. |
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Post by Lucass2T on Apr 9, 2017 17:22:44 GMT -5
That would be awesome. How fast can those drones go you think? I thought it was 20-30MPH, but THIS guy says it was going ~45MPH. I'm sure you could make one outrun the scoot if you try/spend hard enough. Thats so cool! |
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Post by lordverminaard on Apr 10, 2017 13:04:40 GMT -5
One of the guys on my local Ducati club just posted a vid of his drone chasing him on his bike. It was really cool. He wasn't going that fast though. I would link it but it is in a private group on FB so that probably wouldn't work.
One of my little drones can probably hit 40 mph easily but it's not easy to control at that speed. I have a bigger one that is much slower though but most of the speed issues with it are due to the flight controller. One of these days I will get a real transmitter and build my own with one of the many open-source flight controllers out there.
Brendan
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Post by niz76 on Apr 10, 2017 18:16:02 GMT -5
Ya there's lots of 100mph+ drones out there. I thought I was ready for a fast manual brushless drone but I wasn't and lost it (fly away) after only like 4 flights! So now I just stick to my slower but still brushless GPS drone. At least when it gets away from me and turns into a tiny dot in the sky I can just hit the "Return to Home" button haha. Unfortunately it doesn't have the "follow me" feature. I can pretty much guarantee that I will figure out a way to mix drones and scoots though! (my GPS drone is down atm due to a water landing  ) |
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Post by ryan_ott on Apr 10, 2017 18:54:34 GMT -5
I think you need to share some drone videos with us.  |
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Post by niz76 on Dec 2, 2021 14:17:24 GMT -5
Wow- So crazy to re-read this whole build thread 5 years later and re-live the nightmares I went through with this thing!
I can save you the TLDR of about 30 pages by telling you the main culprit was always trying to tune with a mis-aligned flywheel with the pickup coil. Once I figured that out, she's run pretty flawlessly since then. To this day the tune has been relatively untouched.
I just fire it up and ride it!
I never did replace that piston with the broken skirt. It's still in there lol.
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Post by niz76 on Dec 5, 2021 17:42:44 GMT -5
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) and I took the opportunity yesterday while my ladies were at a Hunter Hays(?) concert and rode 3 hours round trip to go buy yet another drone hehe. 
Scoot on!
)
