Code 45 Turbo Boost Limit Exceeded

[detobias]

Quote:

Originally Posted by JCI400 How does the actuator work? Its hard as heck to see. I see a vacuum line in and that rod to the wastegate out. What else is there to it? Is it manufacturered to look for a certain positive pressure in the vacuum line to operate? Does positive PSI in the actuator combine with pressure from the turbo to open the WG?

yes, more or less

the positive pressure in the exh manifold/turbine housing IS pushing against the WG puck, adding some force to try to open it

AND the pressure applied to the WG can via the solenoid and vacuum lines will push against the WG can's internal spring to open the WG

I suggest reading
www.DempseyBowling.com
and the pages therein; also
Donovan's Dodge Garage
click on Turbo Database ; read ALL sub-pages
also

[EvilcowRoland]

Maybe this will help, maybe it won't.



This isn't a perfect diagram obviously, but this is basically how the system works. Boost pressure applied to the can pushes on the diaphram (in red) and overcomes the spring tension (blue) holding the wastegate closed. When the wastegate opens, some exhaust bypasses the turbine wheel, so it limits the boost the turbo can generate.

[JCI400]

Thanks, the posts helped clear it up for me.

Its remarkable, what a balancing act has to be occuring. Boost in the turbo is not enough to open the WG, and positive psi in the vacuum line is not enough to open the WG, but together there is enough pressure to open it.

If the spring/diaphram is too weak it opens early killing power, if its too strong it never opens damaging parts.

So to test the WG, you have to have enough boost in the turbo for the computer to open the selonoid and that combined positive pressure then allows it to open.

Kinda hard to do, revving a motor with no load on it can scatter parts. How do you test it? Connect a boost gauge and believe what it says.

[puppet]

Quote:

Originally Posted by JCI400 Thanks, the posts helped clear it up for me. Its remarkable, what a balancing act has to be occuring. Boost in the turbo is not enough to open the WG, and positive psi in the vacuum line is not enough to open the WG, but together there is enough pressure to open it.

No. There can be enough pressure in the exhaust turbine to open the swing valve ... at that boost level though you better have the right fueling etc or you will burn it down. The boost pressure going to the WG actuator is enough to open the swing valve (puck). When we are raising our boost levels around here we have to find a way to bleed off the pressure in that vacuum line (going to the actuator) to help keep the puck closed since it only takes 5-10 psi depending on arm preload tension. We use bleeds, "G" valves or some other type of manual boost control (MBC) to accomplish this.

Quote:

Originally Posted by JCI400 If the spring/diaphram is too weak it opens early killing power, if its too strong it never opens damaging parts.

True ... but we don't rely on the spring in the can to determine our boost level. We tune to a boost level and dial that level in so it isn't exceeded. To do this we use one of the methods I described above. There is nothing wrong with higher boost levels as long as you've tuned for it ... and the engine can hold together.

Quote:

Originally Posted by JCI400 So to test the WG, you have to have enough boost in the turbo for the computer to open the selonoid and that combined positive pressure then allows it to open. Kinda hard to do, revving a motor with no load on it can scatter parts. How do you test it? Connect a boost gauge and believe what it says.

You can use a common air compressor to test the WG actuator. Regulate the output down to 5psi and connect the WG actuator to the air compressor hose using a length of appropriate sized vacuum hose. You can watch the arm move out from the WG actuator as pressure is applied to it. Doesn't move at 5psi? ... raise the pressure to 6psi and so on. You'll find out at what boost level the WG actuator will open naturally. It'll be around 5-7psi. Common sense now tells you that if you connected that WG actuator directly to the intake manifold vacuum source (with a hose) the actuator arm will move when boost hits 5-7psi. The SV puck is opened and boost stays right there at that level.

[JCI400]

You guys have been great, stay with me a little longer on this thread.

Puppet, you are correct in that positive pressure opens the wastegate. I followed your steps, watched it work and none of the lines leak.

My problem lies in either the selonoid or the wire from the computer. Jumping the battery to the selonoid terminals I can hear it 'click'.

I have continuity from the computer red connector 19 (green) to the green connector on the selonoid. I also find red/19 to ground has continuity, both to the ground screw next to the computer and to the welded on bolt the selonoid bank attaches to the fender with a nut.

Testing while driving, I have 13.5 volts from red/19 to ground, when the boost meter gets around 15+psi the volt meter reads OF (overflow?). I am a programmer by trade not an electrician, so does this make sense?

The computer is a new/rebuilt, couple weeks old max, short of this one issue, works great.

Tee'ing the vacuum/boost source to the WG Can gives around 6-7 pounds boost, you're right. But it still is not right, and you can see by my array of posts, it bugs me when its not right. Not when we are this close to having it run 'right'.

[EvilcowRoland]

My guess would be you have a bad wire to the wastegate solenoid. But that's just a guess without being able to examine the parts myself. The easiet thing to do would be to use a manual boost controller. Set it to 9 or 10 PSI and forget about it.

[JCI400]

Yeah, I've come to that conculsion myself. Thanks to you, Puppet and NAJ I've got a good feel how things work. At least to begin trying some of the recommendations.

I already ordered an MBC, a Black Stealth, figuring it will disappear into the engine compartment best. Cheap but effective, set it and forget it.

I've also bought a Sunpro vac/boost guage that I will install with the MBC. You think 10 psi is a good high for boost?

How do you guys get more boost without the computer freaking out? I've seen the MP computers mentioned but have only found one vendor for it. Does Mother Mopar still sell these? Or is there a better solution?

Been reading the archives here, as well as Mini-Mopar, Donovan's and DempseyBowling.

Once I get my DD back I will have more time and freedom to turn the wick up on the 'lil beasty.

[EvilcowRoland]

10 PSI is good for a T1. Some of the later T1 cars came that way from the factory. I definately wouldn't go over 12 without an intercooler, and that's only if you're sure you're getting plenty of fuel.

Your car being an '85 has a fairly lowsy intake design. Boost can stack up in the intake over 14 PSI and cause some issues. Plus the design is very hard to intercool. So to make any real power you'd need to convert to the later model 1-piece intake. There's info about this swap on Donovan's site (and others). The actual Mopar Performance computers are still floating around in used shape mostly. Our vendors carry some very nice calibrations though and can make a custom computer for your setup. Forward Motion, FWD Performance, and Turbos Unleashed all sell performance parts for our cars.