D4BF Boost and EGT issue

A

algor251

Member
My new D4BF in my JB500 is finally fully broken in. I thought it’d be a good idea to start tuning it.

First thing I’ve done is tightening the watergate actuator to boost 10lbs. That’s been great. I figured I should try to get a little extra fuel at the top end of boost. I spun the plunger to to be the deepest offset it could be and removed the nylon spacer. I put it all back together and all was fine and dandy for a good bit. As I was driving on the highway at about 60mph, I started losing boost and my EGT’s started rising rapidly. I let off the accelerator, stepped on it again, and had full power again. It felt like it went into a limp mode or something.

I did put it back to the factory settings and it happened again. Same as before too. I can let off the pedal, step on it again and have full power again. I did plug the overboost relief valve. I’m not really sure what’s going on. Anyone have an idea?
 
The self-resetting thing is odd.
Is there any extra noise while you are losing boost? The symptoms* match a boost leak, but they tend to make a loud whoosh noise.

If the small boost hose to the IP comes off you get the same symptoms, but that wouldn't usually self-reset. Maybe a split hose that's opening up when hot? Or the diaphragm is not perfectly sealed to the IP body and metal cover? Torn diaphragm? (thinking of things you would have disturbed while tuning the IP)

I would check the tightness of the hose clamps on the turbo outlet, and on the small boost hoses from the turbo to wastegate and IP. Look for signs of boost leaking out (engine oily residue)

Also check where the inlet manifold meets the head for oil leaks (loose manifold nuts?).
 
I haven’t heard any extra noise. I was expecting to hear some sort of whoosh, but nothing that I’ve noticed.

I’ll have to take apart the IP again and really inspect it all. All the hoses currently have the pinch style clamps. I might swap those out for regular hose clamps.

I’ll take a good look at all
Growlerbearnz said:
The self-resetting thing is odd.
Is there any extra noise while you are losing boost? The symptoms* match a boost leak, but they tend to make a loud whoosh noise.

If the small boost hose to the IP comes off you get the same symptoms, but that wouldn't usually self-reset. Maybe a split hose that's opening up when hot? Or the diaphragm is not perfectly sealed to the IP body and metal cover? Torn diaphragm? (thinking of things you would have disturbed while tuning the IP)

I would check the tightness of the hose clamps on the turbo outlet, and on the small boost hoses from the turbo to wastegate and IP. Look for signs of boost leaking out (engine oily residue)

Also check where the inlet manifold meets the head for oil leaks (loose manifold nuts?).
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the hoses and connections. Good thing it only has about 13,000km on it. It’ll be easy to see any sort of oily residue from a boost leak.
 
No expert here but could the turbo waste gate be sticking open when you hit max boost? Then when you let off the accelerator it closes?
 
algor251 said:
That crossed my mind too, but I thought it would just stay boosted if the watergate were to stick open.
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Nope... it stays vented/bypassed. It is possible for excess boost in the turbo to push the wastegate open against a weak spring... i.e. if you block the wastegate actuator boost line it can still be forced open by the turbo itself.
 
sk66 said:
Nope... it stays vented/bypassed. It is possible for excess boost in the turbo to push the wastegate open against a weak spring... i.e. if you block the wastegate actuator boost line it can still be forced open by the turbo itself.
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Is the remedy to add a boost controller instead of adjusting the actuator?
 
Early this morning on my drive is when I blew the relief valve. It was completely gone. The only reasons I noticed that are I lost all boost and it sounded like I had a hole in my exhaust. I’m trying to figure out how it unthreaded itself. I never heard it blow off or thought of it until it was gone.
 
algor251 said:
Is the remedy to add a boost controller instead of adjusting the actuator?
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No. You need a wastegate actuator with interchangeable springs/heavier spring... but it sounds like that wasn't your issue.
 
For the four little bolts that hold the metal lid down? M4 from memory? FInger tight and then a little more. Something like 5 inch-pounds.

If one (or more) had stripped the threads in the alloy housing then that might allow a boost leak.

If they're stripped you could repair the threads with heli-coil, or drill right through and use longer bolts with a nut on the far side (but that's far more irritating to install)
 
I have a feeling that’s where my boost leak is. I put hose clamps on all the fittings and still the weird leak at heavy loads. I was thinking of either of those fixes are the next move. I’ll try the heli-coil first. As always, thanks for your help.
 
@Growlerbearnz so I’ve swapped out all of the clamps with proper hose clamps, heli-coiled the injector pump, changed fuel filter, and still having the same issue. I never hear a “whoosh” to indicate boost leak.

Could the rev limiter in the IP be causing this? I don’t have a tach, so I don’t know what rpm’s I’m at. I’m thinking of fitting one.
 
algor251 said:
Could the rev limiter in the IP be causing this? I don’t have a tach, so I don’t know what rpm’s I’m at. I’m thinking of fitting one.
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I doubt it. The rev limiter is just a function of how the IP controls the engine: the accelerator lever (= gas pedal) position sets the desired engine speed, and the IP adds more (or less) fuel until the engine speed matches the accelerator lever position. The "rev limiter" is just the screw that stops you from pressing the accelerator pedal too far.

I think the IP is probably ok.

I wonder if your wastegate or actuator is somehow jamming open. At a steady cruise speed the wastegate is never completely open or closed, but fluctuates somewhere in between as the boost pressure balances the wastegate actuator spring pressure.
Theory: If the linkage was binding or catching on something, it might be enough to hold the wastegate too far open. Lifting the accelerator would reduce the boost, allowing the actuator spring to overcome whatever's binding the linkage?

Tightening the linkage to increase the boost puts extra pressure on the actuator spring. It's possible the spring itself is binding, maybe a couple of crossed coils?
Maybe try returning the actuator to stock (if you haven't already) and see how it goes. Have a good look at the mechanism and linkages while you're in there.
 
Growlerbearnz said:
I doubt it. The rev limiter is just a function of how the IP controls the engine: the accelerator lever (= gas pedal) position sets the desired engine speed, and the IP adds more (or less) fuel until the engine speed matches the accelerator lever position. The "rev limiter" is just the screw that stops you from pressing the accelerator pedal too far.

I think the IP is probably ok.

I wonder if your wastegate or actuator is somehow jamming open. At a steady cruise speed the wastegate is never completely open or closed, but fluctuates somewhere in between as the boost pressure balances the wastegate actuator spring pressure.
Theory: If the linkage was binding or catching on something, it might be enough to hold the wastegate too far open. Lifting the accelerator would reduce the boost, allowing the actuator spring to overcome whatever's binding the linkage?

Tightening the linkage to increase the boost puts extra pressure on the actuator spring. It's possible the spring itself is binding, maybe a couple of crossed coils?
Maybe try returning the actuator to stock (if you haven't already) and see how it goes. Have a good look at the mechanism and linkages while you're in there.
Click to expand...
I finally got around to taking a look at things. I twisted the linkage back towards stock just one full turn. I’m making 9lbs of boost now and the weirdness hasn’t happened as of yet. I haven’t really pushed it too hard either. That’s usually when the problem would occur.

I didn’t see any obstructions around the actuator. It was dark out so I will have to go back and take a closer look.

I’ve noticed an increase in EGT’s. I’m guessing that’s because I haven’t turned down the fuel at all. Is that something I should do since I’ve decreased the boost a little?
 
Small changes to the boost and fuel shouldn't make notable changes to EGT's...
 
sk66 said:
Small changes to the boost and fuel shouldn't make notable changes to EGT's...
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Gotcha. I’ll have to dive into it deeper this weekend and try to get to the bottom of things.

I got it warmed up yesterday while driving around began to giver ‘er the onions. It did the weirdness again right around 9.5lbs of boost. Usually when I let off the accelerator and step on it again, it will go back to normal, I gain my boost back, and the EGT’s go back to normal. This time when I stepped on the pedal, it did NOT go back as per usual. That’s telling me something may be stuck on the actuator. I’m hoping to get it figured out this weekend. I hope it’s an easy fix.

Thanks for all the help though. This forum is a savior.
 
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