domi said:
...Do you think I underestimated my FTP?...
Possibly, it's hard to say. For one thing your testing methods seem to change from test to test which makes things difficult. If you use the "regular, repeatable long interval" method for estimating FTP then they should be power levels you hit quite regularly during your L4 efforts not your best effort on any given day. The NP during a longer L3 ride I wouldn't take too seriously. Using NP to estimate FTP assumes you've been challenged up to your limits during the ride and generally assumes a bit shorter ride. Something like a one hour criterium where you've been pushed hard. If it's during a longer L3 ride you were probably either holding back a bit to get home in one piece or a bit tired from the early parts of the ride or simply didn't push up to and beyond your limits.
If you look at your power distribution histogram for say the last 28 days or perhaps the last 14 days, what does it look like? Do you see a substantial step down between two adjacent bins that correspond to your 235 or 250 watt estimates? Play with bin sizes a bit but I usually get good results with bins sized between 7 and 15 watts. Again, this only works if your rides have pressed you up to and beyond your FTP on a regular basis. If not it will underestimate FTP.
How can I raise my FTP faster, with the 85-90% you mentioned, or with L4 work,
Well, if you could sustain pure L4 work day in and day out and still recover well enough to continue to train hard then it would probably raise your FTP very rapidly. But those are big "ifs" most folks can't do very many back to back L4 sessions without excessive fatigue. Backing off to SST (85-95%) can allow you to do more total weekly training that focuses on FTP.
Mixing it up a bit is a real good idea. I challenge my best 20 and 30 minute efforts at least once every two weeks but do quite a bit more work at a bit lower level(85-90%). A good approach I push a lot is to start the week with your hardest efforts but shortest overall workout, follow it with a day of slightly easier but longer work and finish a 3 day block with an easier but longer ride. So it might look like, L4, SST, L3 or something like that in 3 consecutive days.
My first A race is on April 20th, and my big goal would be to break the 300W boarder before or in the race. Does this sound possible?...
If your FTP estimates above are accurate then I think that goal is going to be difficult to reach in such a short time. Many folks don't increase FTP by 65 watts in a full season if they've had much previous training. Pulling that off in 3 months would be very impressive. But who knows, you're young, perhaps without a great deal of training history, you've started training with structured measurable methods. And it sounds like your FTP may be underestimated at the moment. The only way to find out is to keep training.
Just don't get too hung up in any arbitrary numbers like 300 watts. You'll get what you'll get by the time your races roll around. It may or may not be enough to achieve your competitive goals. But the point is to continue to improve throughout the season and into future seasons. Cycling fitness along with race savvy and tactical knowledge takes time to develop and new racers typically improve for many years. Even with 300 watts of FTP at your disposal someone with more race savvy or better fitness for the course could make you suffer and with less than 300 watts you could still ride a very good race if you ride smart. Power is great, but it's only one aspect of racing sucess in mass start events.
Keep up the hard work and good luck,
-Dave