Recently I upgraded to a 3071R with an external Tial 38mm wastegate. The wastegate came with a 1.0 bar spring (which is in the wastegate now), and a secondary spring to add to the 1 bar spring to make the overall spring rate 1.4 bar. I finished the install and hooked up the stock BCS and went for a drive. I didn't get a reading above 1 bar, so i started, incrementally, and worked my way down to zero on the boost map. Not one single change in boost control.

I ended up reading about the gm BCS, and bought in on May 24th. If finally came in this week, a completely different rant, and I installed it. I moved my values to 65 in all sites, and finally am hitting 1.5 bar. I need to do some fine tuning as the ramp is steady up to redline, but you get the picture.

My question is should I install the secondary spring and tune the BCS for the extra .1 or .2 bar, or should I just leave the wastegate alone, and tune the BCS for .5 to .6 bar? I am concerned on environmental changes that could sway the BCS larger than if I would just add the spring and tune for the slight change. Any and all comments are welcome.

BTW if you haven't upgraded to the gm BCS, do it! It makes a world of difference on the boost map control.

 

Did you hook up the GM solenoid in place of the stock one without a resistor? If you did, did it trigger a CEL? (Personal query for my own info)

Anyway, Its probably in your best interest to set your wastegate spring pressure to the lowest you feel would run "Safely" should something happen.. Last thing you'd want is to have trouble with your car and not be able to lower it in an alternate map.

 

No resistor, no cel, and no problems as of yet. This has only been on the car for ~2 hours of driving and 4 days.


Kind of an ambiguous answer. The stock 'failsafe' setting would be the default spring rate as the solenoid is a fail open. This stock setting would be 1 bar. The map that I am developing is for 1.5 bar, and I am thinking that if I put in the extra spring, the GM BCS would only control .1 bar, as the spring rate would be 1.4 bar. Even if the GM BCS would fail, I would then be at 1.4 bar (wastegate only).

My real question is would it be benifical to switch the wastegate from 1.0 bar to 1.4 bar and allow the GM BCS to control .1 bar, or leave it and allow the GM to control .5 bar. The effects of a GM BCS failure would be either the car would run rich, or richer depending on the wastegate spring rates, but how would weather changes affect the GM BCS control of .5 bar as opposed to .1 bar?

 

If your using closed loop boost control, then it shouldn't vary much as weather changes. But I think leaving it the way it is, allows you to run much lower boost should you have an issue such as bad gas, or some other problem. If you set it to always run the higher boost at wastegate spring pressure, then you don't have that flexibility. The solenoid failing was never really a concern since it does normally remain open if it were to burn out. Basically I keep a spare with me for that reason.

If your ok with running 1.4 bar all the time (even in less than optimal conditions) then I see no reason why you shouldn't run the heavier spring. But my personal preference is to give myself enough flexibility in adjustment..

 

Well as I am writing this, my car is disassebled and in the garage. I am waiting on my brother to come over to help me close the wastegate. It definately takes two people to shut this thing up. One to hold the cap together with both springs, and the other to install the bolts.

As for the gm boost control solenoid, you are correct in that it fails open. I did a rudimentary test (blew though it with my mouth ) while the car is down and the air passed though with no problems. This could be a catastrophic event if I didn't hear the alarm on my boost gauge (defi b series). This is why I decided to install the spring instead.

In the event I need to run a higher boost level (like on race gas), then I can easily hook the gm bcs back up and switch to a different map.

Thanks for the opinions Jack!

 

Oh a word of warning about running without the resistor, I doublechecked today how mine is set up..

In your boost map, if your 0% column is set to ECU, start the car and let it idle for awhile (if you can) if the solenoid gets very hot, its because its "on" all the time because thats how the stock system works.. I set my boost duty to 1% (or 1 in closed loop) this sets the lowest possible duty cycle, it'll still ramp to the wastegate level, but if you leave it at ECU the solenoid will get so hot, to the point of burning your fingers if you touch it, it will eventually burn out the solenoid..

Basically I'm testing something in open loop boost, so I have mine set for 1 in teh 0% column, and 70% in the 20-100% column..

I'm going to spend some time and figure out what rated current limiting resistor you need so its enough to actuate the solenoid, but not generate so much heat.. Hopefully someone who works with the AEM knows the boost control solenoid driver's output current draw where I can determine what resistor is needed.

I did make a plug and play interface for the solenoid though.. But I don't want to make anything available or show anything until I finally find the correct resistor.

Why would it be a catastrophic event though? On my wastegate (the stock one) if it fails "Open" it just goes to wategate pressure (10.5psi on my car) if it fails closed, it would wildly overboost because it wouldn't get any signal..

 

I am running an atp kit with a tial external gate. As I am sure you know, the tial has an upper and lower port. I am connecting the upper one to the output side of the boost solenoid. If I were to lose control of the solenoid, and it fails open, then the upper and lower sections of the wastegate would be equal pressure, and keep building boost. This is why I said catastrophic.

On a side note, with the spring installed, the boost ramps up very, very fast. I know that I could 'tune' the utec's boost map to do the same thing, but 3 hours to pull the turbo and install the new wastegate spring was much easier.

On a side side note, I am very pleased with the seat of the pants dyno on the atp kit. Stay tuned for a complete write up with before and after dynos.

 

Sounds like fun..