I'm looking for opinions on my approach to using GPS data for carb tuning. Before anything else: YES, I already know I might as well be asking the best way to make wooden wagon wheels, measure my johnson using a stopwatch, or the most efficient way to waste hilarious amounts of time. The goal is to back up each step of carb tuning that I typically do on bikes with data, without paying $100 a run on a dyno that's two hours away. Let's assume air temp, humidity, stuff like that never changes. I have no O2 sensors, no speedometer, and no tachometer on the 1G SV650, making this slightly harder. But I do have a cellphone. Here's what I'm thinking: SETUP: 1. Place enter and exit cones on a 1/3rd mile (or less) dead end road nearby. This road has a slight uphill. 2. Record GPS data at the highest rate possible (one data point per second or less). This records position and speed which I can export. RUNS: 1. Top end (main jet) - tbd gear, ride in at 3/4 throttle, go to full throttle at start, hold full throttle to exit 2. Mid range (needle position) - tbd gear, ride in at 1/4 throttle, go to 3/4 throttle at start, hold to exit 3. Low range (pilot circuit) - tbd gear, enter at 1/8 throttle, go to 1/2 throttle at start, hold to exit 4. Repeat until police show up 5. Do math and analyze acceleration through run and top speed at exit 6. Change stuff and retest OR Just do 1/8 throttle to full throttle runs between start & exit. Analyze data for acceleration and top speed. Adjust one thing at a time and repeat (ex. main jet, repeat, needle clip, repeat). Look for positive or negative change I can test this by doing some runs as is, then tape over part of the airbox and repeat. If I can't see a difference in data doing that, then there's no way I'll see a difference from minor adjustments. Thoughts? I've searched around and haven't found anything written about doing it this way, probably because it's a terrible idea. vroom?
Just throw a set of flat slides on and be done with it. I've run stock bore, .5mm over, 2mm over, and 3mm over. Never put one on the dyno. I just threw some fat mains in a set of 41mm FCR's and let it rip.
lmao... the biggest flaw is going to be your dead end road is not where you will be racing/riding (hopefully) so. Second... have you seen how easy it is to manipulate a PC/Bazzaz setup??? You could make 20 changes to timing & fueling via laptop before you got your jet collection out of the tool drawer. And you wont get gas on your hands.
Yes, but he wouldn't be racing on a dyno either, which is his alternative to tuning on a piece of straight pavement. Also, are you suggesting he swap his carbs for TBs and a controller? Not everyone has the cash to upgrade either systems or bike. MagnetMan - this is the old school way of tuning carbs. You have the right idea, it's just a matter of getting it down to a science.
So on the dyno at least you can get repeatable results and an A/F display... and 100% less chance of losing traction or some other road incident. Also he didnt mention what type of carbs. Stock ones ?? Personally... Id put the largest main possible for the mods and and the same on the pilot. Or just buy a standalone wideband setup with datalogging. They retail for <$250 for a complete kit these days. Less than most phones. Then you can see AFRs on every section of the track... can even get a cheap camera to watch the gauge while he turns laps.
TPS sensors are pretty cheap and may help you determine an exact throttle position. Along with the timer and track markers it wouldn't be hard to visualize the data you get to see what works best.
Estimating the throttle position kinda ruins the point. I suspect changes in results over such a short duration/distance will easily be masked by small changed in throttle position. IMO, do WOT runs and see if you can see a difference. Most phone GPS are 1hz, so you won’t get much data and will have to do some math. Tune with that. I think by then you’ll see the crazy amount of work this is and will be happy enough.
I have a dyno with A/F module but many times the dyno reads richer than the bike actually runs on the road with CV carbs, especially over approx 70mph. I sometimes use a wide band O2 with the readout on the tank or triple and watch it with my eyes or a gopro camera. I start with mains and work backwards to needle and then pilot/pilot screw. It's alot of work and sometimes takes me 8-10 hours to get it perfect. Worth every second when I ride the bikes around after I'm done.
If you have gopro hero black 5 or newer, it has GPS built in and you can overlay speed on video with GoPro quik. Use media player classic and you can get exact timing down to pick correct start and end frame, 1/60 of a second timing accuracy
