Boost too high!!

[MChrist]

Today, I drove the truck and my boost was over 50!!! Smarty is set about as low as possible and so boost only should max out around 30-35. Today, I noticed truck is much more sprightly, so I looked at EGT gauge and only read 750 while zipping along. Then, I looked at boost and was getting 55 ish!

Keep in mind I don't have head studs, too.

I assume my waste gate is sticking or waste gate actuator isn't working. If these are working correctly, I should be able to unhook the hose from the ATS Aurora 4000 that goes to the stock turbo waste gate actuator, apply 30 psi air pressure and see it move back/forth. If it doesn't, that should point me in the right direction? I'm asking, since the tech guy at ATS was no help. He told me to "wait and see if it gets better. ". Yeah, OK...

 

[JJPage]

I would be more suspicious of the source that is reporting your boost, do you have more than one device to monitor boost? EGT's at 750* is cool, but hard to believe it could produce 50+ lbs boost while cruising.

Keep your egt's under 1250*, don't worry about studs.

 

[cerberusiam]

Your Edge Monitor has lost its teeny little mind. No way your running 50 lbs of boost unless your mashing the throttle all the time. The better running truck is the heavy dense air is stuffing in there.



Have mentioned how much I hate electronic monitors.

 

[AMcCormick]

I would agree with the above. No way you are just cruising along at 50-55lbs and 750*. The truck is flying at 50lbs of boost.

 

[MChrist]

It seems I wasn't clear. By "zipping along" I meant full throttle. All would feel correct until the mechanical boost gauge gets to 30 ish, but instead of boost stopping there, it'll keep going to over 50. Power also increases accordingly. I'm reading 750 degrees at 50 pounds of boost. Boost gauge is mechanical. Truck actually feels like I'm on level 7 Smarty. My mechanical boost always stops at 44, now it wings past it.
So, does it seem like a stuck waste gate / actuator? If so, is what I said the proper way to correct it?

 

[MChrist]

So, just to be clear. . the way I have Smarty set (SW1, 50% POD) I only get around 30 psi and I know how it feels when I floor it. Yesterday, when I got on it to accelerate, it felt way more powerful. That's when I noticed boost was over 50. Even when Smarty is on SW7, I max out at 44psi. Boost gauge is mechanical off a boost bolt from manifold. Truck accelerates and feels like it's on SW5, 100% POD but it's only on SW1. I can accelerate at 30psi, roll on more throttle, and build boost past 50. And it feels like 50!! I'm 99% sure boost is accurate. Truck accelerates much harder than normal, yet EGTs are only around 750-785.
So is this what happens when a waste gate doesn't open for some reason?

 

[fox]

I'd say can some of that extra boost and sell it here!!

Everyone is wanting more.

 

[cerberusiam]

With the added info, it sounds like the WG has quit working or you have a electrical glitch that has upped your fueling rate.



Unload the Smarty, try it, thenload it again and see if anything changes. Not sure about your compound setup and if it has a WG, do you know for sure?

 

[MChrist]

On the aurora 4000 plus compound, boost signal comes from the 4000, which activates the original diaphragm which opens the original waste gate on the stock turbo. The boost rod length is altered so WG opens earlier (or later) than stock... can't remember. I BELIEVE it is supposed to open earlier, if I remember correctly. I assume since my max boost is normally around 30 at low power settings, and goes up to 44 at high levels, that any boost over 30 ish is simply what is being blown past what the waste gate can relieve. That's why I think it's either stuck or the diaphragm isn't actuating. So, if I put 30-40 psi from an air compressor on the hose that goes to the diaphragm, the rod should move, correct?
Also, if it's getting more fuel my EGTs would be closer to 1100, which is where they run on high Smarty levels.
And even on highest Smarty levels, I don't exceed 45 psi. I'm swinging way past 50 easily.

 

[AH64ID]

Do you have a boost fooler? I am guessing not (don't see it in sig), and thats why your boost normally stops at 44, the ECM defuels at this point.



I honeslty think you have a bad gauge. The only WG in the A4K+ compounds is the OE WG on the stock turbo. If that one were to stick I don't think you could get the boost that high, your DP would go thru the roof and you wouldn't spool the 4K as easily.



Try a different mechanical gauge, or hook your gauge up to the air compressor.



On my truck I can't get over about 20-22 psi at SW1 PoD 50, but thats just a single you will get a little more from the twins.

 

[MChrist]

I'm going to go to work today and tinker with it. I'll let you know. Thanks.

 

[MChrist]

Oh, and yes, I do have a boost fooler. Just didn't put it in sig.

 

[AH64ID]

Oh, and yes, I do have a boost fooler. Just didn't put it in sig.

Gotcha, so at least we know your normally getting the full fuel potential.

 

[JJPage]

Sounds like it is running pretty decent... , you may want to leave it alone... .

 

[MChrist]

UPDATE... Ok, I went to my shop and worked on truck. First thing is that I wanted to see if waste gate actuator was moving. I had my foreman looking right at it while I built up 35 lbs of boost (4WD, one foot on brakes, other mashed on the accelerator). Waste gate bar never budged. Then, I took the hose off coming from the big turbo that goes to the actuator diaphragm for the waste gate and shot a small amount of compressed air from the shop air hose directly into the barb for the actuator and the bar/waste gate moved freely. . about 1/2 inch. That seemed free. So I shot some air backward through the same hose back into the big turbo and heard it clearly through the intake.
So maybe the boost gauge IS bad... so I hooked up another 60 psi gauge to the intake horn and ran a hose to the windshield so I could see both gauges at the same time. Took it for a rip and now it runs the way it always did. Both gauges read about 35 psi and my EGTs are back up to 1000-1100.
So..... my boost gauge wasn't the problem, and the only thing I can think of is that the waste gate wasn't opening for some reason, and all the extra air was cooling down the EGTs, because before my "fix" I couldn't get EGTs over 785, boost was 50-55. Now boost slowly climbs up to 40 if I stay in it for more than 5 seconds.
When I got back to the shop, I had the same guy look at the actuator arm while I did another boosted load. This time, I couldn't get boost over 25, and he said the arm moves about 1/4-3/8 inch.
Anybody have any ideas as to what happened??? Could I have ice in the diaphragm?? Blowing it out definitely changed something, since I didn't really do anything else. I didn't unload Smarty because I wanted to rule out one thing at a time.

 

[cerberusiam]

Could I have ice in the diaphragm

That is entirely possible, or, even in the reference line. Considering the blast of cold and wet you just went thru its a high probability. Glad it works now.

 

[AH64ID]

Glad it's working. It certainly sounds like you had a blockage somewhere.

 

[MChrist]

Yeah, it's just weird, though that when I shot just a little air into the barbed end of the actuator, the waste gate moved freely. 55 pounds of boost didn't free it up, but a little shot of shop air did? I dunno.

 

[JJPage]

After what you discovered, I would contemplate blocking the wastegate off on purpose. That is what I was told to do with my set, then adjust fuel to keep egt's under 1250* and I would not have to worry about studs or boost.



That came right from Piers Harry at BD, I know Joe Donnelly is doing the same thing with his R700's. I have been slapping 60lbs+ occasionally for a couple of years now, stock head gasket and studs, all is well.



Just a thought, but not knowing the flow capacities of your chargers, it may be risky business, probably best to do some critical research first.

 

[MChrist]

I wonder if that would over-spin the stock turbo, though. It DID feel a lot crisper, and now that I've been driving it for a few hours, it kinda seems pokey by comparison. Oh well, I don't think I'll chance it.
I've noticed that when I drive it normally (easily) I rarely go over half throttle. Boost gets up to about 25 then slowly creeps up to around 28 or so. I assume that's where the waste gate normally opens. Only when I floor it for more than a few seconds does boost get past 40. I also assume that's due to the flow from the 4000 overtaking the "leak" caused by the waste gate on the stock turbo?