Boost control issues (searched first!)

[1158]

Setup:
b18C1 83mm pistons
full race AC manifold/DP/44mm Tial (7.5 psi spring) with closed loop dump
GT3076R
Fixed duty cycle
Solenoid configured to max boost @100%

First time tuning this setup(2 weeks ago) we could not control boost using the S300 the Hondata MAC solenoid. At 34% the solenoid would not open, ran 15psi. At 35% duty cycle boost would shoot to 20psi and hit boost cut. We suspected it was my waste gate reference lines being hooked up to intake manifold. I rerouted the lines, bottom comes off the charge pipe at turbo outlet to side of gate and is teed to #1 port on solenoid. #2 port goes to the top of the gate and #3(middle) is open. Now at 34% duty cycle I get 8-9psi. At 35% duty cycle the boost still shoots up to 20psi and bounces off the boost cut. I know everything mechanically is hooked up correctly. We had no trouble controlling boost with a MBC on the dyno yesterday (steady 19psi). This happens with a full exhaust and open exhaust.

This is not the first time for this setup. I previously had a Precision SC34 on the car and the boost control worked flawlessly. So I know the wiring (all soldered) is correct. I am using resistor plugs and have the diode correctly installed close to the solenoid. I tried removing the filter on the solenoid, but it did not make a difference. I checked the solenoid at 0psi activation with key on and heard the solenoid buzzing.

I am wondering if the solenoid frequency being set at 78 Hz is the problem. I have tried adjusting it, but am not sure which way I should go and did not make that large of a change. I may try messing with that more, but haven't seen much about it in my searching.

As I stated in the title, I have been searching the boards and trying every solution I come across. So far I have not figured out what is going on. I've included the calibration file for the 34% duty cycle but the only change to the other calibration is changing duty cycle to 35%. The 2 data logs I've uploaded are a run with duty cycle set at 35% and then dropped to 34% and 35% only. The data logs were taken while driving, not on the dyno.

[Spunkster]

I would recommend you have someone else look over your setup as sometimes you will overlook something obvious that is routed incorrectly or installled inproperly. Changing the dutycycle 1% with things connected properly should not increase boost by more than 10psi.

[1158]

I would recommend you have someone else look over your setup as sometimes you will overlook something obvious that is routed incorrectly or installled inproperly. Changing the dutycycle 1% with things connected properly should not increase boost by more than 10psi.

When it was on the dyno we had 4 people looking over everything. I have triple checked everything I can. The fact that it works with a manual boost controller tells me it has to be something with the solenoid or with the electronics. I'll happily go over everything again later this evening, but I do not expect to find anything.

[1158]

I think I fixed it. I changed the solenoid frequency to 10Hz with duty cycle at 35%. Boost went to 10psi. Then I adjusted the duty cycle to 50%, boost went to 17-18psi. I then went back to the frequency, upped that to 20Hz and hit the boost cut. Dropped the duty cycle to 45% and got a nice quick spool, but might have to drop the duty cycle a little more. I was at 16psi @ 6600rpm.

I'll mess around with it more tomorrow and report back in the late afternoon.

Thanks

[1158]

It's fixed. The solenoid frequency was the issue. I increased the freq to 30Hz and dropped the duty cycle to 35%. I now see 16psi around 5500 rpm and it holds steady to 8500 rpm. I'll probably play more with the freq to see if I can get the boost to build faster, but seems like the issue is solved.

[joeb]

Wow , i'm having the same problem . My duty cycles are extremely low as i hit 18 psi with 15 percent duty cycle . I did drop my solenoid frequency down from 78hz to 32hz and it made a very small change . I am going to try and lower the frequency again and see what happens . On my car the quick spool tables have the biggest impact on boost control .Wow what an old thread i just bumped !