My car is way too fast for safety...literally. Boost limit doesn't hold.
 

Problem: my car won't limit boost anymore.

I have a GM EBC connected to a stock WG on a .5 BAR spring. Boost holds occasionally when cold, but then the car blows right thru the boost limit and peak boost foes to the moon. The rattle of detonation was a rude awakening, to say the least.

Any ideas?

Kenik, how do you have the boost controller plumbed to the wastegate?

BUTT, an easy way to fix "too fast" is to grow a pair!!!

it's the wastegate gods telling you it's time to get some race gas and enjoy the blessed lady of acceleration.

All of you are every bit as helpful as expected. LOL.

So if you have the controller plumped to the wastegate in an appropriate manner (which it sounds like you do since it works some of the time) then either the controller is malfunctioning, there is something wrong with the power and/or ground path for it, or maybe one of the signal hoses has a small hole (different than Paul's BIG hole :eek:) or tear in it and the effect is worse once the hose gets some heat in it.

Oh, and grow a pair, Mr. "It's too fast"!!!

Trust me, the speed is amazing and welcome. The detonation isn't. Im thinking it is hose related.

So the question is: assuming it is plumbed correctly (it is), what conditions result in runaway boost levels?

Check the hoses, may have a loose one that is popping free under pressure.

When the controller does not allow air (boost pressure) to get to the wastgate and operate the wastegate spring and diaphragm. In other words, the wastegate valve remains closed when it should open. A hole in one of the hoses can have the same effect.

A boost controller should only add pressure, so default should be WG spring pressure only if you disconnect everything boost controller related.

If the WG can't vent up top, it'll hold too much pressure. That's how the boost controller works.

^^^

JustTheTIPpy, doesn't that depend on how it is plumbed to the wastegate? One method is the controller limits pressure to the diaphram, thus tricking the wastegate into thinking there's not as much boost as is actually present. Not sure how Kenik has his set-up, though. Is the way you describe the most common set-up (I'm by no means a boost controller expert)?

And no, Norm & Paul, I did not just type "I'm bi", ya' hopeful bisches!!!

Kenik,

Are you using a separate boost controller or are you using the Haltec to control boost? What size hoses are you using? Also, check to see what boost level is achieved with the solenoid de-energized. What is your target boost level? Is there anyway to datalog what is going on?

One thing I found tuning boost control on my MS3 was that boost comes up much quicker when the oil is hot, to the point where it would overboost at 4200 RPM's when shifting into third after revving to 6500+ in second. But a straight pull in second from about 2500 RPM's to 6500 RPM's showed no issues. But when the engine was cooler (oil temperature at 180*) there were no issues. Then again these overboost spikes were small (10 -15KPA) compared to yours which seems to be no boost control.

Pull the boost controller out of the loop. Runaway boost is either a failed WG or EBC not working.

My recommendation, dump the stock WG and run a TiAL and Greddy Profec SpecB.

From my understanding, one style restricts the air from escaping from the upper diaphragm cavity and the other directs boost into upper diaphragm cavity.

I believe the one that blocks the venting is the one that can get you trouble. If the diaphragm can't move, boost goes up.

An EBC should sit inline between the TB and top port of the WG, i.e. the signal line. It limits the amount of pressure the topside of the diaphragm see thus preventing the valve from opening and allowing exhaust to bypass.

There is a vent line that in most cases is left open to atmosphere.

Some more advanced controllers have the vent also plugged into the controller valve, they do this so the controller can 'feather' boost onset or 'scramble' where boost hits as hard as the turbo can provide. I dont see many configured like this anymore.

^ Shannon, you say these things just to get a reaction, don't you?

Wastegate is fine. Remove the EBC and spring pressure is achieved. The boost hoses are pretty narrow, so am thinking there may be an issue there. We'll troubleshoot tomorrow and run through all sxenarios.

I might even steal your TiAL and Profec B Shannon...

Just because I dont mention someones junk in a reply doesnt mean I am looking for a reaction.

I dont think you will see any difference with hose diameter.

Be nice or you cant borrow my TiAL.

Did someone say "junk"?!?!?

Kenik, maybe you can borrow this guy's?!?!


http://2.bp.blogspot.com/-DqF_AmC63_...Q/s1600/bb.jpg

:rolleyes:

LOL, we'll see. Funny, it worked before. A little troubleshooting will hopefully go a long way.