Retune boost PID after turbo swap?
 

I just took my car out for a spin with the new 2860RS. The previous turbo was an emotorUSA 2870.

I previously tuned the PID to hit 25psi, and it worked fine. I swapped turbos, and the log looks like it is only running on wastgate. 14psi can, but I saw 215kpa max. boost duty was 0 the whole time. Like a dummy, I didn't think to switch over to open loop and play around. It might be a day or two before I can take it for another run, so I figured I might as well see if anyone has experienced this before.

A little more info:

https://www.miataturbo.net/picture.p...pictureid=2477

https://www.miataturbo.net/picture.p...pictureid=2476

I thougt a while about this issue last night, and I think I know what it is. IIRC I had this same issue when I installed the china turbo. I think I have to tighten down the WG actuator rod some more. While it may seem tight enough to hold the WG shut, I think that there is enough slop to let it open a little under boost.

you have WAYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY too much I.

your numbers should be in the low 20s for both P and I. also with that valve you should be using the 30Hz setting.


I would just go back to square one: start with 100 P, 0 I, 0 D. Lower P until you breech your target during spool. Increase I to keep that target to redline, increasing/decreasing P as needed. Add D as the last step to prevent overshoot and some oscilliation.

I remember us having this discussion when I was tuning the china turbo. The numbers didn't really make sense, but it worked very well. I do plan to go back and retune it. As I still agree with you, the numbers are whack. I've seen a few sets of PID values,a nd the truth is, they all seem to be around the same values P ~ 19 or 20, I under 20, and D is 10 or less.

I think in my effort to spool as quickly as possible I was able to get my P value down to 12, but it required the extremely high I an D values to maintain target.


PS Thanks for the tips brain. I do appreciate them!

On a bright note, the new turbo felt as strong at 16psi as the china turbo at 25psi. Butt dyno of course, but I'll probably run the 2860rs to 22 psi.

nice. for boost I'm like P27 I27 D75.


I wont help with spool, that's long term tracking. Lower P will, but it will also overshoot. increasing D with dampen the overshoot at exspense of some responce.

When all is said and done, you'll see like a 1-2psi overshoot at spool but hold the target all the way to redline perfectly smooth.

I had to lower my P value to 1 before it would boost 2psi over target (25psi) So far mar PID values are 1,0,0 lol. I'm sure I'll have to increase P as I increase I. A P value of 12 only got me to 15psi. Trying to do a boost log in 5th gear from 2000rpm makes my turbo feel like ----. It doesn't come alive until 3500rpm.

Not sure this is correct what you are seeing... Is your plumbing o.k.?
Did you try the open loop?

I haven't messed with open loop for the new turbo. It was tuned for the previous turbo. The EBC appears to be doing its job. iirc my last turbo required the I to be raised before it spooled to my liking. I have a feeling that I will have to increase P as while I'm increasing I. If I don't have success, then I'll go to open loop. I did some research on the spool of this turbo with the .86 housing, and it doesn't seem like 23psi at 4300rpm is that bad. It's a dog in 5th witht he 3.636 before 3500rpm.

Have u tried increasing the frequncy to 30hz and intrvals to 10ms?

My interval is still at 23ms, but I did change to the 39Hz option. I don't believe I have a 30Hz option. I'm going to look at this mornings logs. I took two runs on the way to work with I set to 5 and then 10 with P still set to 1. Based on the gauge reading with I=10 it looked very close to target. Should I be doing the boost tuning in 1:1 gear?

doesn't matter. I like to tune p in low gear to just set the target at spool and the rest on the highway in 4th and 5th