I almost didn't do this project because my 2018 stock bike was really nice factory stock, with relatively mild midrange lag and throttle snatch.
You know how it goes though, lets make it faster and lighter!
The M4 install went about as well as it could with just me fitting it up, only a few regrets midway through.
After the install, I took it for a quick test ride unflashed and with the M4 end can, mainly to check for header leaks.
I found in this state it ran weaker in the mid range but stronger on the top end, so off to Dano's.
When I got the ECU back, midrange was strong with no more factory midrange lag and still stronger top end.
I wanted to fit a 2017+ GSXR1000 Yoshi slip on, the one that Suzuki sometimes gives out free with a new GSXR, because I wanted a nice deep tone and hopefully the better performance a longer can is supposed to give. Also these high quality cans can be found on ebay for less than $300 because some folks got them for free and then went to a full system.
I had a link pipe made up at a local custom automotive exhaust shop, they did a mediocre job. I had to make a few tweaks to fit it properly, but it allowed me to do the adapting.
So here's my results, I have a test spot between two markers on a remote country road where I start out at 35 mph in 2nd gear at the first marker and note my terminal speed at the second marker which in this case is the end of 3rd gear. the distance travelled is 1/10+ mile, and less than 1/8 mile.
Believe it or not it's a pretty good method that gives reasonably consistent results. I always calibrate my speedometer with a speedo app on my phone for comparison between bikes, but in this case it was the same bike, which happens to read about 6.5% fast. After a good number of repeat runs, I found an average speed of:
Stock bike terminal speed 120 mph
Bike with reflash:
M4 full system M4 can speed 123
M4 Yoshi can w/noise insert: speed 124
M4 Yoshi can no noise insert: speed 125
So basically best case I got a 5 mph terminal speed gain for the short distance travelled, don't know how that would translate to a 1/4 mile run with a decent drag racer, but its a noticeable difference with a nice linear acceleration all the way.
The tone with the Yoshi is what I had hoped for, I like deep tone without ridiculous loudness. I didn't even try the M4 can with insert removed because I wouldn't ride around that loud.
I do have to say the Yoshi idle is uneven as some have reported with an open can, and smooths out with the Yoshi noise insert.
I'm going to have to decide which way to go between the two.
Yes, Ill put the body work back on when I'm through messing around