Why is there so much lag in between on three shot per second burst mode?

I shoot with a rebel T6, which is supposed to have a three second continuous burst mode.  I interpret this as a continuous burst of three shots for every second that I hold the shutter down until I letgo, the battery dies, or the card is full. Which ever comes first.

But I learned very quickly that factors such as the buffer on the camera, weather I’m shooting in raw versus JPEG, the write speed of the card, and even the speed at which the camera itself can write to the card, all factor into the equation.

So, with a SanDisk extreme pro card that writes it up to 90 MB per second, shooting in raw format, I will get one or two 3 shot burts, followed by 3 to 6 seconds of waiting for the busy signal to go away.  The longer I try to shoot in this manner, The fewer shots I get in a burst before the busy signal comes again. I can have one shot several seconds of waiting until it clears me for the next. 
ultimately, I have found that only sports icon mode, shooting in large JPEG or smaller, allows for the ongoing continuous shooting that I need for capturing movement in sequence.   None of the creative modes can accomplish this, even with the continuous shooting option selected, and even in JPEG mode. Under these circumstances, Shooting JPEG’s buys a little bit but not a lot.

So in order to get the performance out of my camera that I need, I need to defy everything that is considered Holy and photography… Shooting a JPEG, and shooting an icon mode.

And, since I “jumped” From a 2002 first generation Canon EOS rebel to a 2016 T6, I have seen only a nominal improvement in this area.

from a 2000 to 1st generation Canon EOS rebel to a 2016 T6, I have seen only a nominal improvement in this area.

How high do I have to go with my camera upgrade to get Th ongoing burst mode with no lag in between but I’m looking for while shooting in raw format and creative mode’s?

thanks!

Reading the spec's for a camera will tell you how many images you can get with it's buffer in different JPEG / RAW combinations. That's usually a best case scenario. I haven't done the research but my guess is that you'd have to go to a 77d to get a reasonable buffer. I know that the SL-1 and 2 buffers are small and perform like your T6.

You should be able to get 6 frames before the buffer has to clear. Of course, this is only 2 seconds of shooting since your camera can do 3 frames per second. It will then take a little over 1 frame per second when the buffer is clearing. That's with raw shooting.

Some things that will decrease your shooting speed are lens optimizations, noise reduction, high ISO, and anything else that takes processing. I don't know what options the t6 has available but turn off anything looks like is making the camera do extra work.

Back in my T4i days, I noticed when lens aberration correction was turned on, it really slowed down my burst mode.

Try turning that off...