Turbo vitara D16Y8 stutter question!!

[D16hudson]

Hey guys, thanks in advance for the help!

Engine setup:
Vitara built y7 block
Stock y8 head
Rdt t3/t4 .57 trim turbo (25 psi)
Rdt intercooler
Rdt charge/intercooler piping
Greddy type s BOV
Tial 38 mm wastegate
Rc 750 cc injectors
4 Bar map sensor


THE ISSUE:

Two weeks ago I was tuning down in South Carolina. We got to the numbers we wanted and then decided to do a few more dyno pulls just to make sure everything was consistent. The second to last run pulling in 3rd, the boost starts coming up (18,19,20,21.....) and right about the 20-21 psi range the car stutters. The MAP/psi showed the boost coming up (20,21) then dropping for a quick instant down to 13 then back up to 21,22 ish and then back down to 12,13,14 ish and then back up to 22 where it finishes coming up to 25 psi.

We did it again (on the street this time) and noticed it did the same thing in second gear but it wasn’t noticeable (maybe because 3rd gear is longer and it spends more time in full boost??)

Things I’ve tried:

It seemed like a bad electrical connection possibly at the map sensor so I replaced the connector. The 4 bar map sensor is new as of September/October 2017.

I tried turning down the boost to see if it had anything to do with the turbo, that didn’t help.



I’m not really sure where to go from here. It ran just fine on the dyno 10-15 pulls no issues and then the last two showed this weird issue. Any input would be greatly appreciated!

[Spunkster]

Without the calibration and datalog showing the issues it is really hard to say what it might be.

[D16hudson]

Hey! Sorry I am just getting back to you, I never received an email that anyone replied... le sigh. Also I’ll apologize I am new to the turbo/boosted scene, so I’m a little confused as to what information would be best to post up to solve this problem from the data logging. Any tips and pointers for that as well would be awesome.

[Spunkster]

We need the calibration it is running on at the time the datalog is made and a datalog made showing when you are experiencing the issue.