Phish806

iTrader: (5)

I went out with a friend last night to start doing some logging and turning up the boost on my build. Long story short, the car makes six pounds as supposed to and is data logged. We then drive for a ways and about 15 minutes later we try another pull - the car only made 4 pounds. We try multiple pulls and still the car only produces 4 pounds. I shut off the boost controller and WHAM 6 lbs (spring pressure) - turn the boost controller on and 4 lbs. Obviously my boost controller is having issues. After the car warms up or after a certain amount of time (not sure which) the boost controller is not controlling boost and wont let it build more then 4 lbs.

Well, since we cant turn up the boost we went to a car show. The car cooled down for a few hours. Leaving the show, i turned the boost controller back on and turned the boost up to 8 lbs. Did a pull and Whala 8 lbs of boost.

To recap, after the car runs for awhile the controller will not let it build more then 4 lbs of boost. Shut the controller off and it runs on spring pressure fine. When the car is first started and driven ( for about 10 minutes) the boost controller will work perfectly.

Anyone have any theories on this? Controller itself is inside the car in the glove box. The solenoids are under the heat shield on the side of the car where the computer is located... Anyone have any thoughts?


Here is some info about the car:
90 Rx7
motor - LQ4
Turbo - Comp 8079
Boost Controller - Innovative MBSC-1

Couple pics:

Selenoids for boost controller are under the heat shield on the left. Engine computer is in the same location.

stevieturbo

4psi to 6psi ?

And 4psi with a working controller, and 6psi without makes no sense.. Base spring pressure is normally lowest pressure, unless you're using CO2 or a high pressure air source.

Explain exactly what way this controller is configured and what boost you think it should be running.

Phish806

iTrader: (5)

I understand all the numbers are a little confusing. Let me try to explain better.

The spring is 6lbs

Boost controller set at 6lbs.

When you first start the car, it runs 6 lbs and its supposed to.

Once the car is heated with nothing changed, it only makes 4 lbs.


This is how its all plumbed. Also, its running off manifold pressure NOT on-board air supply

asubennett

iTrader: (6)

You are using manifold pressure on top and bottom of the gates. Hook it up to compressed air and tune your PID settings first. Then back to manifold pressure and see what happens.

Sounds to me like as the car gets warm your settings need to be changed. Why not just tune the car at operating temperature and run the car at operating temperature. Don't get into boost until the car is warmed up properly.

Can you post IAT logs and Water temp logs when it does what you want and when it doesn't for comparison?

Phish806

iTrader: (5)

I can get some logs, but it may be a few days. I have a lot going on in the next few days. How would intake temp/water temp have an effect on pressure at the wastegate? I don't have much experience in the boost controller / wastegate area.

RedRocketZ28

iTrader: (19)

Logs won't do any good. If he turned the controller on, or up to a higher boost setting, it still only builds 4 psi. It isn't a tune issue.

Phish806

iTrader: (5)

In my opinion its a controller or boost leak issue. In theory it should always make spring pressure and never less - unless there is a leak somewhere? Am I wrong with that thought?

transam69230

iTrader: (49)

Agreed!

asubennett

iTrader: (6)

If he had a mechanical problem (leak) it would not being doing this "work sometimes then not work others". Mechanical problem would be a common denominator.

Something is up with your boost controller settings. Because you are using a dual solenoid set up and not using a fixed pressure source it makes me want to see your logs.

Forcefed86

iTrader: (4)

Makes no sense.

The way you have the BC plumbed it has no way to turn down the boost. If the WG has a 6lb spring in it and it makes 6lbs with the bottom port alone connected, applying pressure to the top port can't lower the boost. It can only raise it.

Block the signal to the BC and eliminate it. Vent the top port. Go test the car cold and hot.

Sounds like a WG issue. Maybe it's getting stuck once warm? Using a china gate?

Phish806

iTrader: (5)

The gate is a precision 46mm wastegate.

As far as the gate getting stuck, if I turn off the boost controller and run it on spring pressure, It will hit and run spring pressure (6lbs) every time. As soon as I turn the boost controller back on, it malfunctions and only produces 4 lbs. (only when hot)

Edit: Let me add that I agree that there is no way, with how its installed that it should be able to decrease boost to under the spring pressure

Forcefed86

iTrader: (4)

Something else is wrong. If you understand how the BC works you know it has no way to drop pressure below the WG spring pressure, period. It can't magically change spring pressures or apply vacuum to the upper port. It can only apply additional pressure which raises boost.

You need to isolate things physically. Remove the top port and run a known non- leaking vac line form the intake mani to the bottom port. If that makes 4lbs you know something (maybe solenoid) is leaking. If not you know it's the gate itself or a boost leak.

If your positive the Wg isn't sticking, then there has to be a leak. If you have the ability use shop air regulated down to 6psi or so and bench test it all.

A boost leak check rig is also a must have IMO with any turbo car. Pressurize the whole system to 6psi and check it for operation and leaks.

ls1_chevelle

iTrader: (9)

next time you go for a drive... turn the controller on, add 1 psi then remove 1 psi, stand on the throttle and I'll bet it makes 6psi. My msbc1 was doing what you described. Its off the car now.

Phish806

iTrader: (5)

My plan for tonight has been to pressurize the whole system and check for leaks. I figured it would be a good place to start. If I find nothing I will move on to eliminating the controller and maybe even hooking up a manual controller to see if it does the same.

ls1_chevelle

iTrader: (9)

I bet it makes 6psi with the controller shut off because when the WG opens it is dead heading out the top port(making it harder to open).

If you take the top line off your waste gate and just run a line to the bottom gate(to the manifold), The car will most likely only make 4psi. a "6PSI" spring isn't an exact science. EVERY combo is different.

Phish806

iTrader: (5)

Once we let the car cool off, we set the controller on 8 psi. It made and held 8psi for the next two pulls. Parked the car after that. So it will make more then spring pressure if the car is cool and we set the controller to do so.

asubennett

iTrader: (6)

Which is why I want to see logs. The only variable you have given us is operating temperature. And because you are not using a fixed pressure source (you said you are using manifold pressure (is it plumbed to the compressor?)

ls1_chevelle

iTrader: (9)

take video too showing the msbc1 operating

Phish806

iTrader: (5)

Correct, all that's changing as far as I know is time and temperature.

I am getting my manifold pressure to the boost controller/WG from the Intake manifold right behind the TB.

Phish806

iTrader: (5)

I will see if I can do a few tests tonight and get video of the issue at hand.