Sequential Turbo transition points
 

Hi,

Can anyone who has changed your sequential turbo transition points please post your numbers and if you got good results. My primary to secondary turbo transition point is not smooth at all. I want to smooth out my turbo transition and make more linear pwer. Thanks

Easy way to smooth this out is on the dyno.

Make one pass with the transition really low, say 2500, then make another with the transition at say 5500, overlay the dynos.. where the torque curves overlap, try making a pass with the transition at that RPM...

basically your seeing where your primary runs outta breath and where the secondary is required to continue MAKING power.

I have a dyno map already. I figured I could figure it out approximately from that one. My dyno graph shows a quick rise in torque then a dip then another steep curve as secondary comes on. I am assuming the primary is running out of breath at the first peak. I know some people only adjust the transition for wide open throttle and not partial throttle. I wanted to see some people's numbers to see what people are doing.

Read down this thread:

https://www.rx7club.com/showthread.p...rbo+transition

I would like to see some logs to back up what you are saying in that thread.

Nashman your explanation doesn't really make sense to me I guess. My understanding is that most people lower their transition points by about 500 rpm not raise them as you have done in you r car. My car has the problem that the primary comes on strong and the boost goes way up and then there is a significant dip as boost drops at transition, then BOOM secondary comes on hard. Meaning the transition is happening too late in the rpm range. If my secondary were to come on earlier before the primary runs out of breath it should help my problem. My understanding is that the low rpm listed there is to tell when the car switches back to the primary alone and the high setting is when it makes the transition to both turbos. Right?

https://www.rx7club.com/attachment.p...1&d=1245600017
factory solenoid behavior

https://www.rx7club.com/attachment.p...1&d=1245787926

solenoid behavior observed.

TCN (green) ---> Turbo Control solenoid. A value of "1" means it is energized, "0" means it is not.

CCN (blue) ---> Charge control solenoid. A value of "1" means it is energized, "0" means it is not.

https://www.rx7club.com/attachment.p...1&d=1245787926

settings for this test run. I was using boost option 1.

I have also used the default transition values, except raised the "low" setting to 3500. It would make the car shift back into primary-only operation more, which felt more torquey and responsive for driving around town.

F'd up transition
 

Attachment 349905

This is a log of my boost transition in a first gear run. Also a copy of my dyno run. I am going to try and change the transition points and log again when I get the chance. I am gonna try and get the dip to go away and peak on the first turbo and then gradually go up to the second turbo peak. I peaked at 75 boost at 4500 rpm and then dropped to 39 and then back to 81 around 6800. Any ideas? I hope to solve it with tuning rather than changing the pill sizes if I can.

Unfortunately your dyno logs are not particularly helpful. We have no idea what your solenoids are doing. You have a Datalogit, correct? Go into your datalogit "monitor" window and enable the following:

in the bottom right corner, "Advance" and "sensors." all others should be off. On the "sensors" section of the monitor window, select "TCN" (turbo control solenoid) and "CCN" (charge control solenoid). All other boxes in that section should be unchecked.

Go out and do a couple pulls, one in each gear at least. Do that with the exact same map and boost settings as you have right now. Then remove your restricter pills completely and change nothing in the PFC. Log again. Post the map and both logs.

For the first log we need to see what your wastegate solenoid duty cycle and precontrol solenoid duty cycles are, and how boost changes before and after the charge control and turbo control switch. The second log is to see see how much the restrictor pills are affecting the boost control behavior. Another log that would be nice to have is a log of you running on spring pressure only for both actuators. Restrictor pills would be removed, and the line from the actuator to the wastegate and precontrol solenoids would be capped. This would tell you whether you need to port your wastegate or not.

Read up on how the boost control system works, starting with the second post: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/why-engine-so-damn-complicated-part-1-sequential-turbos-demystified-841821/ . Also read this thread about PFC boost control logic in general (scroll towards the bottom of the first post).

Can I get a favor from a couple folks? I need a couple people that have sequentials (preferably '99 twins) to do a run in second gear from about 2k to 7-8K and log basic. The please send me the log file to drugstorecowboy@att.net

I want to look at 2-3 peoples transitions to see if what I am seeing on mine is normal. I'm beginning to think mine is normal.

Thanks in advance.

Anyone?

What was the problem eventually ?