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Post by JoeyBee on Nov 4, 2015 15:21:44 GMT -5
The results of testing the larger 30mm carburetor on a stock 150cc engine (157QMJ) are done. I am very disappointed from the lack of performance gains and the very noticeable increase in fuel consumption. Clearly as ricardoguitars pointed out, without upgrading the engine the increased amount of inputted fuel is just being wasted. With the help of my wideband air/fuel sensor I was able to tune the 30mm to perform almost as my stock carburetor. I say almost because the 30mm did not have an adjustable needle. But after adjusting the mixture screw and swapping the main and pilot jets, I was able to get it to maintain near a 13.5 air:fuel ratio until WOT then drop to 12.8ish. After getting the tunes to match for both carburetors I ran some tests to see if I gained any speed. The quarter mile runs were .5-1.0 seconds slower, and WOT runs were several miles per hour slower. [Quarter Mile Runs]  [WOT Runs]  |
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Post by pistonguy on Nov 4, 2015 16:21:13 GMT -5
Just swapped my stock 24mm carburetor on my 150cc for a 30mm carburetor form GY6 Racing Team. Give me a few days to fine tune it, and then I'll have some statistics on performance. Standby for the results..... Yes Size matters. Stock Motor? |
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Post by lain on Nov 4, 2015 16:25:03 GMT -5
Just swapped my stock 24mm carburetor on my 150cc for a 30mm carburetor form GY6 Racing Team. Give me a few days to fine tune it, and then I'll have some statistics on performance. Standby for the results..... Yes Size matters. Stock Motor? I believe that is what he may have said. |
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Post by horace on Nov 4, 2015 18:43:17 GMT -5
Indeed size does matter....... Don't rely on what the missus says  In My humble opinion, The jet size is more important than carb size...... The biggest carb ever made is only as good as the jet squirting out the go juice... I maybe VERY wrong as air flow is also a concern..... Balance is the key.............. Let us know how the experiment goes brother!!!!!!!!!!!!!!! |
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Post by JoeyBee on Nov 4, 2015 18:54:00 GMT -5
Yes, stock 157QMJ engine. And fine tuning will include everything from air:fuel screw, adjustable needle, to jets.
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Post by lain on Nov 4, 2015 19:53:45 GMT -5
Well when you use a larger carb you also allow a larger band of air to enter which may be ratio-wise the same as the old carb but in quantity there is more gas to explode and more air to use to explode the gas which in turn creates more torque. Bigger more forceful explosions happening in the combustion chamber will force the piston away from the chamber with much more power, of course there is always a limit to how much particles you can fit in there. If you can figure out how to put more in there than physically possible your next project will most likely be a Tardis, lol.
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Post by JoeyBee on Nov 4, 2015 21:07:25 GMT -5
Well when you use a larger carb you also allow a larger band of air to enter which may be ratio-wise the same as the old carb but in quantity there is more gas to explode and more air to use to explode the gas which in turn creates more torque. Bigger more forceful explosions happening in the combustion chamber will force the piston away from the chamber with much more power, of course there is always a limit to how much particles you can fit in there. If you can figure out how to put more in there than physically possible your next project will most likely be a Tardis, lol. That was the same line of thinking I had. But larger carbs have been a hotly debated topic here, so I statistically wanted to confirm or denie it. As for a Tardis, I will leave that to manic doctors. |
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Post by lain on Nov 4, 2015 21:31:22 GMT -5
Well when you use a larger carb you also allow a larger band of air to enter which may be ratio-wise the same as the old carb but in quantity there is more gas to explode and more air to use to explode the gas which in turn creates more torque. Bigger more forceful explosions happening in the combustion chamber will force the piston away from the chamber with much more power, of course there is always a limit to how much particles you can fit in there. If you can figure out how to put more in there than physically possible your next project will most likely be a Tardis, lol. That was the same line of thinking I had. But larger carbs have been a hotly debated topic here, so I statistically wanted to confirm or denie it. As for a Tardis, I will leave that to manic doctors. Well I'm no engineer or metal fabricator, but I understand enough physics and often think heavily about how each component in scooters work and how they effect other parts. I still feel like some of the physics of carbs are a mystery to me but I understand that the size of the smallest passageway is the limit of the entire system just like with computers. I compare computers sometimes because that' what I worked on for over a decade before getting into scooters. You know how if you have a super fast cpu on a computer it will still only go as fast as the front bus has bandwidth to allow the electricity to move. I guess I'm getting a little abstract if you don't understand computers already. Maybe a better comparison would be comparing how liquid moves through a straw. Not exactly the same but as far as thinking of providing fuel to the engine, think of providing your favorite "fuel" (like redbull) to your face via a straw. Obviously a wider straw will get that redbull to your face in larger volumes at the same or faster rate than before providing that your face can provide the "vacuum" to pull it in and your face has the space to store it before consuming it... and well let the exhaust go to your imagination on this one, haha. |
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Post by JerryScript on Nov 4, 2015 22:43:42 GMT -5
Larger equals less vaccum, hence the need to upjet.
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Post by pistonguy on Nov 5, 2015 7:02:28 GMT -5
Here is what your dealing with, The Engine can only Demand so Much Air and Fuel. Beyond that you going backwards.
I do Not have these Numbers, Yet!
At or above a 26mm this Already OutFlows What the Engine Can Use. So what is this going to do for me, Your Going Backwards, Especially with a Stock Motor with Stock Exhaust.
Your Dumping a Toilet into a Straw,
Extremely Important to Keep Velocity Up that Translates into Cylinder Charge/Fill/Mix.
I love to find the K&N booth at the Trade show's, they have that nifty display with the pin pong ball floating in the air with a OE filter not moving the Ball, More Flow Right? This Question Blows there mind.
The OE Filter Already Outflows what the Engine Can Use So What will this do for me? Uhhhhhhhhhh, duhhhhhhhh,
You can wash the K&N. Ive see that crap on the Dyno and Loose 1 1/2 hp on a 600 sport bike.
Yes it will start and run, go down the road and back but if we put her on the dyno bethca she Loses HP and Torque.
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Post by ricardoguitars on Nov 5, 2015 20:43:29 GMT -5
Yes, sizes DOES matter, as long as your engine can handle it, you need a head with bigger valves, better fuel flow, and upgrade the exhaust to take advantage of the bigger carb. When I put the 59mm BBK on my scoot, I also put a big valve head, eliminated the vacuum petcock, and put a high flow fuel filter; the results are crazy acceleration and more top end.  |
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Post by ricardoguitars on Nov 5, 2015 20:51:14 GMT -5
BTW, it takes a toll on fuel consumption, I went from $20 per month on fuel to around $30, I'm breaking the bank!! Seriously, the only drawback is on long trips, you will have to fill the tank more often, I'm considering a bigger tank or an external reserve tank when doing long trips. |
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Post by JoeyBee on Nov 14, 2015 11:03:23 GMT -5
Updated on top.
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Post by JerryScript on Nov 14, 2015 11:46:22 GMT -5
Excellent video Joey! I look forward to more! |
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Post by JoeyBee on Nov 15, 2015 10:39:20 GMT -5
Excellent video Joey! I look forward to more! Thank you for the kind words. It was a fun project, and something different to try. It's a little rough around the edges in some places, but that can be worked on. For the next video I'm debating between testing spark plugs or cutting open several blue "racing" CDIs looking for sand. |
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