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.

"Bull Zork"

^^^

Ha! Hilarious right thar!!!

Now that you've received all the input you need to deal with your problem.....well, what kind of problem is that? A fine example of German ingenuity that's TOO FAST? We all LIVE for that, spend all sort of cash to ACHIEVE that. Suck 'em up, grow some cojones, put the pedal to the metal, hook 'em up dude.

But only provided you don't hear the death rattle. Ditch the EBC, put a 1.0 bar spring in there and call it quits. It's all we really need to have an additional measure of fun and takes one more failure variable out of the equation.

The death rattle is scary. I heard it today. Never want to hear it again.

And to be clear, the car is NOT too fast. The only reason it is too fast is that at umlimited boost, it is too fast for the engineering tolerances of the motor, given the death rattle.

At least everything seems to have stayed intact.

Kenik, so you no longer run the overboost circuit? Hows come, bro?

Tec3r powers the fuel pumps. Overboost is out of the circuit.

Days like this make me think EFI.

Ah, I forgot just how "not stock" your car actually is! :D

So no over-boost protection capability at all with that setup?

If running EFI, it'll fuel cut to the injectors at a set MAP kpa.

I'm getting the feeling that you are going to beat me (not like that) to the EFI punch! Fookin' Norm's already there, tha' bisch bastage!

You could always make dummy metal fuel lines that looked like you were running MFI.

Do you not have any overboost protection? If you have detonation (veeery bad), what level boost are you getting and what did you set the control at?
Something is going to go badly wrong here.
My EBC delays the boost signal release on top of the WG. Works perfectly . But the good advice (Mark) would be to put a 1 bar spring in and forget EBC if you have these issues that can't be resolved.
Next thing we will be reading your rebuild thread :-(
Alan

Its the hose. Get it fixed or replaced.

I set the control initially at .9, then at .8 to see if altering peak had any effect. It blew right through to the moon, based on watching the gauge. I wasnt data logging at the time and will not be repeating the incident just to get data.

I had understood that double spring pressure is all a wastegate could hold, even with an EBC. Apparently that isn't the case, as I know I exceeded 1 BAR, more than double the .5 BAR spring.

Frustrated, as I've worked so hard to ensure the motor never sees this kind of abuse. Once is enough for me, so the car is grounded for the time being til we can figure it out.

The WG isnt the hold factor in this equation, your EBC is.

Since you isolated the EBC you either have a problem with the feed line or the EBC itself. As others have mentioned focus your efforts here. It is not uncommon to see hose collapse under heat. Don't forget the hose also sees vacuum under closed throttle if you have it plumbed to the manifold under the throttle.

I don't think you described exactly how it is plumbed to your system.

btw, you made this comment.

IMHO, pull ignition first. If you pull timing you can reduce rpm and thus reduce exhaust pressure and then boost. It acts like a rev limiter. Yes, most EFI systems can set this limit based on pressure (or other variables)


Pulling fuel makes the engine go quickly lean under high heat generation. Bad things happen here as the sudden lean condition actually increases the chance for detonation. Keeping fuel continues to cool chamber when there is no spark to lessen.

Think about how knock sensors (or J&S Safegaurd) work - they don't usually affect fuel flow. same effect, different cause, same solution.

Aren't you piggybacking a TEC on your CIS?
And that is what you're using for the boost control?

Consider using a non-GM valve. We gave up on those a long time ago, only success with these, and the default position in case of failure is open, so WG spring pressure only.

Plumbing:

http://forums.pelicanparts.com/uploa...1456246885.jpg

Here's what I see:

http://forums.pelicanparts.com/uploa...1456247123.jpg

I don't see any notion of pulling timing for boost.

Another thing I need to confirm: Richard Clewett logged into the machine remotely and altered the tune a while back to work on the IACV config. Today, I was looking it over and the tuning app no longer recognized the MAP sensor configuration. I need to double check and see if the MAP is actually reporting accurately...which could very well be another culprit.

Chris, I'll take one. Email in your inbox.

.....i have a 3rd grade math level admittedly but isnt 210kpa around 30psi?