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Scootering mag tested GTS on good long trip. What may interest you is that they did comparison acceleration and roll on with GT200.
The extra cubes do make a difference.more overtaking torque as well.
Averaged 69 mph in an hour and didnt need the hand hovering over the clutch lever like the two stroke boys usually do.
This is getting really serious stuff.For my wife you understand.
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Re: Scootering tests GTS
old mod wrote:
This is getting really serious stuff.For my wife you understand.
So she's itching to get herself one? Laughing emoticon
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More Detail
GPS best reading 87 mph speedo about 5% optimistic showed 91.25mph
GPS also said had topped 82.4mph with pillion
over 69 mile stretch averaged 67.8mph
PM tuning already working on pipe and fuel injection mapping
Gulp this things got some herbs.
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Re: Scootering tests GTS
old mod wrote:
Averaged 69 mph in an hour and didnt need the hand hovering over the clutch lever like the two stroke boys usually do.
I know next to nothing about two stroke scooters. Can you explain this?
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Isn't he refering to the need to pull the clutch in quickly when some part of the engine or transmission seizes?.. a distinct possibility on some older scooters at max speed...
⚠️ Last edited by Kev on UTC; edited 1 time
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Kev wrote:
Isn't he refering to the need to pull the clutch in quickly when some part of the engine or transmittion seizes?.. a distinct possibility on some older scooters at max speed...
Yep. Mostly the worry is about piston seizure. The way to make a two-stroke scream is to get the carburation to baseline, then start leaning it out a little bit at a time until it screams. But leaning it out causes it run hotter, hot enough to seize, so it's a delicate balancing act. On Cannonball 2004, Mike Heytens used an Exhaust Gas Thermometer (EGT) to watch the exhaust temp from his engine so he could run it right at the limit. For folks like me with liquid-cooled engines, this is pretty exotic stuff to see. Apparently the EGT technology was pretty standard stuff in piston-powered aircraft, so this isn't something new.
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jrsjr wrote:
On Cannonball 2004, Mike Heytens used an Exhaust Gas Thermometer (EGT) to watch the exhaust temp from his engine so he could run it right at the limit. For folks like me with liquid-cooled engines, this is pretty exotic stuff to see.
In recent years the hot rod / muscle car crowd has taken to utilizing off-the-shelf O2 sensors (which also measure temperature in the absence of O2) to get an optimum tune out of their somewhat fussy carburetors. Normally, these sensors would be used in a fuel injection system to regulate how much fuel was pumped into the engine, but they can be hooked up to electronic gauges to display how rich or lean the fuel mixture is.

I've got a bung welded onto the exhaust (nearest the exhaust manifold) with on O2 sensor in it on my 66 Mustang. The muffler shop that did the work for me, who knew all about O2 sensors, thought I was crazy for putting a fuel-injection type sensor on a carbureted V8.

See this page for a description of the theory.
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jess wrote:
I've got a bung welded onto the exhaust (nearest the exhaust manifold) with an O2 sensor in it... See this page for a description of the theory.
There's one idea that hasn't occurred to me. I like it, I like it, yes I dooo.

I have a Lincoln 220 welder in my garage. It would be a cinch for me to weld an adaptor into my stock exhaust manifold, and I happen to know where to buy a sweet panel-mount LCD voltmeter that is perfect for this application (and less than $10 too). But, I don't want this to be a permanent fixture on my scoot. So, think, think, think... got it! I'll build an O2 sensor probe, that I can insert into the exhaust pipe. Wait, I recall from memory that the stock pipe terminates at an angle. My scoot is home, and I'm currently in the township library down the road. I'll have to reserve my thoughts until I go home and look at the scoot.
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...
Greasy can back me up on this one.

I use an HFT guage I can't fit the rear floorboard on my lammy with the pipe i'm a-runnin' so I go by my Hot Foot Temperature Guage...

I really can tell when the ol' TS1 is runnin to hot, too rich or too lean by my foot .

-larry
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Would depend on which boots you are wearing, or do you ride barefoot?
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Just curious here, Larry, does anyone make a scoot that is 250cc, water-cooled and has gears?

BTW, I'm going in to the Akron store tomorrow to look at my red GTS and then have it delivered next week. Thanks for all the prep work you did on it and it sounds like you guys sold all but two of your GTS stock already.

Greg
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You all got it
Yes thats right to prevent seizure if poss.
But JRSJR answer lead onto interesting stuff, Jess ,I will pass that on to a few hot TS1 and really tuned Vespa jockeys.
Getting back to the figures they were with a just run in engine so were even more impressive I think.
Cheers
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Thisplacerocks! wrote:
Just curious here, Larry, does anyone make a scoot that is 250cc, water-cooled and has gears?
There are plenty of motorcycles like that, but no scoots that I've seen. And certainly there is nothing like that in the US. It could be ridiculously fun.
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There's probably little interest in this subject, but I'll share what I've gathered for its educational benefit.

An O2 sensor remains inert until it reaches 600F. Until then, no voltage is generated. For a scooter application, it would be best to use an O2 sensor that has a built-in heating element. O2 sensors are low current, high impedance, devices. So, use a very high impedance voltmeter to get accurate readings. The chart of voltage versus fuel mixture is correct for all engines, as its strictly a property of an O2 sensor, and has no relationship to a specific engine, or O2 sensor placement. An O2 sensor setup is easy to comprehend, easy to build, and provides a unique insight for the racing enthusiast.
addicted wrote:
jess wrote:
I've got a bung welded onto the exhaust (nearest the exhaust manifold) with an O2 sensor in it... See this page for a description of the theory.
There's one idea that hasn't occurred to me. I like it, I like it, yes I dooo.

I have a Lincoln 220 welder in my garage. It would be a cinch for me to weld an adaptor into my stock exhaust manifold, and I happen to know where to buy a sweet panel-mount LCD voltmeter that is perfect for this application (and less than $10 too). But, I don't want this to be a permanent fixture on my scoot. So, think, think, think... got it! I'll build an O2 sensor probe, that I can insert into the exhaust pipe. Wait, I recall from memory that the stock pipe terminates at an angle. My scoot is home, and I'm currently in the township library down the road. I'll have to reserve my thoughts until I go home and look at the scoot.
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Gary - How hot do our scooters (and specifically the exhaust gas) run? It's not too hard to get the area just past the exhaust manifold on a big V8 up to 600 degrees, but I'm completely in the dark about scooter temps.
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addicted wrote:
So, use a very high impedance voltmeter to get accurate readings.
Sounds just like a pH probe.

http://pdfserv.maxim-ic.com/en/an/A0512.pdf

Or use DrDaq with a built in Op Amp

http://www.picotech.com/press/oxygen_sensor.html
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jess wrote:
Gary - How hot do our scooters (and specifically the exhaust gas) run? It's not too hard to get the area just past the exhaust manifold on a big V8 up to 600 degrees, but I'm completely in the dark about scooter temps.
I naively assumed all internal combustion engines produced comparable exhaust gas temperatures Jess. In reading about 02 sensors, the various types of O2 sensors, and the modes in which they're deployed, the most reliable closed-loop applications came from the use of heated-element O2 sensors. From what I've read, O2 sensors are very finicky and will only phase-change (produce a voltage from a chemical process) when they reach 600F. The majority of O2 sensor applications run in open-loop mode most of the time. That is, they ignore the absence of O2 sensor voltage most of the time. Better systems introduce a bias voltage into the O2 sensor loop, to trick the ECU into thinking that the O2 sensor is working, when it is not producing voltage. Best systems try to sustain the elusive O2 sensor voltage, with a built-in heating element. Given a scooter's low displacement, where the volume of exhaust is relatively low, a heated O2 sensor would provide the most consistent readings.

I do happen to have a temperature measuring kit, that reads accurately to 800F. I can't read internal manifold temperatures with the kit, and I wouldn't be able to do that with an internal probe either, because there's no way to insert the probe into the top of the exhaust manifold. I can, and will gladly, measure the scooter's outside manifold temperature, at the top of the manifold, and also at the tailpipe to approximate the rate of heat dissipation as the exhaust gas travels down the pipe. Here's a picture of my temperature measuring kit.

I realize I haven't fully answered your question yet, Jess. That's because I don't currently know the answer, but I'd like to find out. I'm just as curious as you.

I always try to include my speedo in a picture, so folks can see that my mileage steadily increases, even in the sub-freezing winter. Don't feel sorry for me though, I'm super-comfy with my heated vest and gloves.
Temperature Probe Kit
Temperature Probe Kit
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That looks like a cool set-up, Gary. I'm curious, but I might be an anomaly.
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Perfect shot Jess. You are indeed an anomaly with this, in the classical sense, as you are acting in "deviation or departure from the normal or common". On the popularity scale, technical discussions rank lowest.

Having tuned engines the long and hard traditional way, I view using an O2 sensor to refine the process is too compelling for me to ignore. I'm officially dropping the topic here, but will continue to pursue it for my own edification. Thanks for bringing this use of O2 sensors to my attention.
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Bah! Technical discussions are perfect fodder for Modern Vespa, at least by you and me and maybe a few others. If you find out more, I'd really like to hear about it. Your efforts are very much appreciated.
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I'm curious too. I will likely want/need to use a wideband O2 sensor at some point with my 250. I would eventually like to go to Megasquirt for engine management.
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