Leo Vince GP RIPS! - unconventional chamber

Thought i'd share my new experience with a unconventional chamber. The Leo Vince GP has a diverging cone, but not a converging cone.

I have a petty long tuned length (measured to the rear flat face) so it hits pretty low. my clutches are engaging probably around 5k and it's starting on the pipe right there and pulls like an SOB for a few thousand RPS and then drops off very abruptly. the front wheel is just about lifting without any pull on the bars at all and i'm running a 31/22 sprocket setup (tomos A3). in case you didnt know that's almost as tall as you can go.

no speed runs yet, there's ice everywhere outside. I'll post a result for top speed as soon as it's nice enough

sound is suuuuuuper quiet. I don't hear the exhaust at allllll over my intake

running on:

ported airsal

vm20

4 petal

hpi

tuned, lightened, stiffened clutches

Re: Leo Vince GP RIPS! - unconventional chamber

Photo on the bike?

Re: Leo Vince GP RIPS! - unconventional chamber

forgot to mention I used a biturbo header. pedal and shock clearence are both good too

Re: Leo Vince GP RIPS! - unconventional chamber

whoa thats cool i'd love to hear more about it in the future.

Re: Leo Vince GP RIPS! - unconventional chamber

Overpriced Parts /

Looks cool I can't see why it wouldn't work 2 stroke outboards have no pipe at all and they work fine

Re: Leo Vince GP RIPS! - unconventional chamber

i'm confused though, did you mod a leo vince or does this exist somewhere?

Re: Leo Vince GP RIPS! - unconventional chamber

chief mycon Wrote:

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> did you mod a leo vince or does this exist somewhere?

This. i'd like to do some research on the thing if i can.

Re: Leo Vince GP RIPS! - unconventional chamber

What did the pipe originally belong to?

Looks cool, if it works good even better. I like how the pipe shape slighly mimicks the shape of spokes on your mags.

Re: Leo Vince GP RIPS! - unconventional chamber

Ken Roff Wrote:

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> Looks cool I can't see why it wouldn't work 2

> stroke outboards have no pipe at all and they work

> fine

I was reporting that this thing BLASTS, not simply that it works. Very much a low end powerband with how long my header is, but i think it could be tuned

chief mycon Wrote:

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> i'm confused though, did you mod a leo vince or

> does this exist somewhere?

it's a leo vince scooter pipe i ebayed for $150 shipped hack and welded to a biturbo header. the header was only a few mm smaller than where we hacked the GP, so we made one more cone for a total of 8 diverging cones

it's originally for a Aprillia SR50. I was a little nervous because it lacked the converging cone, but i found enough dyno results to go for it

This is a AEROX dyno result with a few pipes. The scooter is apparently stock, but each exhaust tested has been derestricted

(edited)

Re: Leo Vince GP RIPS! - unconventional chamber

max, you running the 30 pounders ss springs?

Re: Leo Vince GP RIPS! - unconventional chamber

Mo Peds Wrote:

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> max, you running the 30 pounders ss springs?

I'm not. they're too heavy for how much i lightened the clutch arms. the 25 pounders are working awesome. I'll try to eventually post another speed run watching the speedo rise

my guess is the 30 pounders will do awesome in a more stock clutch (edited)

Re: Leo Vince GP RIPS! - unconventional chamber

What tuned length did you end up with by using the biturbo header?

Re: Leo Vince GP RIPS! - unconventional chamber

Brian Carver /

this pipe is like alien technology! cool!

Re: Leo Vince GP RIPS! - unconventional chamber

you have a lot of header you can work with there, you can shift your powerband up incrimentaly each time you shorten it.

Re: Leo Vince GP RIPS! - unconventional chamber

neat

Re: Leo Vince GP RIPS! - unconventional chamber

I have more to report.

the pipe starts to hit at 5k and pulls hard until 7.5-8k

it noticeably falls off the face of the earth at 8.5k

with my setup, that gets me from 0-40mph really fast and then it will peak at about 45

i wish we still had a bike dyno in town.. I'll try to post a video watching the speedo soon

Re: Leo Vince GP RIPS! - unconventional chamber

no groms no blasters /

dafuq

Re: Leo Vince GP RIPS! - unconventional chamber

campeona del mundo /

stever said it...

man i liked my kitted a3...ripped off the line and topped out at like 48 with stock gear and the stock carb. thing was rad! OTHER THAN THE FACT THAT NOTHING I COULD DO COULD STOP THE IMPENDING DESTRUCTION OF CLUTCHES. if it weren't for that i so woulda kept it.

Re: Leo Vince GP RIPS! - unconventional chamber

how were they getting 7.5hp out of a stock aerox(minarelli horizontal) with just an exhaust?

Also, wouldn't it of been smarter to get one of those other wider powerband pipes since your bike isn't variated. just saying

Re: Leo Vince GP RIPS! - unconventional chamber

Ryan Mayer Wrote:

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> how were they getting 7.5hp out of a stock

> aerox(minarelli horizontal) with just an exhaust?

> Also, wouldn't it of been smarter to get one of

> those other wider powerband pipes since your bike

> isn't variated. just saying

as far as the aerox, i dont know and didnt really care. it wasn't important for how i was using the information. whatever setup the bike was, it remained constant while testing those pipes.

you're right about it being designed for a variated bike. that's why it drops off so hard.

i can throw a biturbo back on and get over 55. i wanted an around town 40-45 mph pipe that looked good. i'm planning on tuning this to quit between 9-10k

and it was an awesome looking stainless pipe no one else is running for half of what i was about to drop on an mlm

Will campeona del mundo Caldwell Wrote:

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> stever said it...

>

> man i liked my kitted a3...ripped off the line and

> topped out at like 48 with stock gear and the

> stock carb. thing was rad! OTHER THAN THE FACT

> THAT NOTHING I COULD DO COULD STOP THE IMPENDING

> DESTRUCTION OF CLUTCHES. if it weren't for that i

> so woulda kept it.

got that under control. about 500 miles on these without any issues

Re: Leo Vince GP RIPS! - unconventional chamber

adjusted the timing and now I can hold 52 mph all day. It's as far as i dare push it without my egt working

Re: Leo Vince GP RIPS! - unconventional chamber

would ya just look at that

Re: Leo Vince GP RIPS! - unconventional chamber

i think it looks good, and it's so different and obviously performs well for an around town daily bike. a+

Re: Leo Vince GP RIPS! - unconventional chamber

I shortened the header by about 2 inches an gained about 1.5k rpm

Re: Leo Vince GP RIPS! - unconventional chamber

‡∫‡ß Sire Roycington (Duke of Waffles) /

Sharrrrrrp! I always wanted to do with with my old LeoVince ZX pipe. Same one made for the Aprilia. Those pipes are designed to hit at 8-8k. I know I hit 60 once on the sr with it. Kid even used the bracket.. ha!

Re: Leo Vince GP RIPS! - unconventional chamber

BAFFLE CONES (Jennings)

We have already noted that the baffled end of most expansion chambers is conical. This cone lends the chamber rather more pleasing lines than it would have with a flat end, but that is not its reason for being. The reason is that if we end the chamber very abruptly, with a flat plate, the wave reflections away from it will also be very abrupt: strong, but of a duration too brief to provide the desired port-plugging effect except within extremely narrow limits in engine speed. A conical baffle, on the other hand, extends the wave reflection time (as reflection occurs down its entire length) and, because its effects are thus felt over a wider engine speed range, the engine’s useful power band is broadened. Obviously, here, a long, gently tapered baffle-cone will extend an engine’s power range more than a shorter, more sharply tapered cone in the customary trade-off between range and peak power. These tapers should be, in most cases, twice that of the diffuser used in the expansion chamber. Thus, in a chamber having an 8-degree diffuser, the baffle-cone should be tapered 16-degrees. That is the rule in general. However, wide variations are possible and may be employed to cope with a specific situation. The largest taper angle you should use is 20-degrees; the smallest, 14-degrees. And you may, to obtain a particular effect, mismatch diffusers and baffle cones in any combination. The thing to remember is that there is a peculiar side to the power-range broadening effect of the baffle-cone: most of it is on the part of the engine’s power curve past the horsepower peak. Thus, for an engine that has proven to be rather fragile when pressed beyond its rpm red-line, you may terminate the expansion chamber with a 20-degree baffle cone, and rest assured that if the system’s tuned length is established to place the horsepower peak, say, 500 rpm below the danger mark, the engine will resist very strongly any effort to get it spinning faster.

My experience in dynamometer-testing various expansion chamber configurations has shown that a 20-degree baffle-cone gives a good, strong power peak – and then simply cuts the engine dead, in terms of output, if you try to force the revs any higher. A 15-degree baffle-cone, in contrast, gives a somewhat lower maximum output – but helps the engine maintain its output well after the peaking speed has been exceeded. The implications of this influence on an engine’s power curve should be obvious: motocross bikes can gain in engine flexibility from a long, gently tapered baffle-cone, but if you are tuning for some young man who often forgets to protect the engine from over-exerting itself by changing gears, then you can use a 20-degree baffle cone. It will remind him about the gear lever by chopping the power drastically every time he tries to use too many revs.

Re: Leo Vince GP RIPS! - unconventional chamber

Dug this up because now that i'm on a variated bike, i think i'm going to hunt down another sharp angle or flat face baffle.

anyone play around with this?

How about a side (or dual) bleed, flat baffle design.

^^ wouldn't this be the recipe for maximum peak power?

Re: Leo Vince GP RIPS! - unconventional chamber

Even variated bikes need a certain width power band. Go for something with a steep angle and just mess with the tuned length. Maybe an adjustable header length?

Re: Leo Vince GP RIPS! - unconventional chamber

Jake:

i guess what I'm going for here is not a normal rideable setup. I'm looking to find the absolute maximum boost we can get from a chamber to push a top speed a little higher

i want to build something like this: I think if we give the rear face some shape, we'll get different vibrations and fundamental frequencies. how would you tune that..? no idea

(edited)

Re: Leo Vince GP RIPS! - unconventional chamber

cool, also see: inside of an estoril

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