Can't drop boost - 67DBB

[87natl]

Interesting problem to have, but I can't get boost below 23 lbs with my 6776DBB. I was curious if anyone else has had a similar issue, especialy with THIS turbo. I've got the same HD actuator on this turbo that I ran on my TE60, and with that turbo I had no problem gettin boost down around 18 if I wanted. I didn't port the WG hole when I installed it, and thought there was a chance I might get some boost spike. But this isn't a spike. It shoots right to 23 psi and holds there rock solid, with the arm set as loose as possible. I'm getting ready to go ahead and pull the turbo back off, check the markings and see how my puck is lining up, but I'm skeptical if this is going to help if I'm not having spiking issues.

Thoughts?

 

[Ed Valvo]

Unhook the wastegate actuator arm and let it flap loose in the wind. Go out and WOT it and see if it builds boost. It will feel like a pig at first but will eventually build boost if the WG hole is too small. It should not if the WG hole is large enough. If it does, port the WG hole.

 

[Otto J]

Add and alky control kit and leave it alone at 23#s or add a few more

But i had to port mine also and still didnt get less than 22#s

 

[87natl]

Oh, I'm running alky, and I've got it tuned in at 23psi. (because I had no choice). But I'd LIKE to be able to get it lower for around town, if you understand. 23psi on the street with this set up is WAAAAYYYYY too much power.

So Otto, even after porting yours you can't get below 22???? Damn. How large was your WG hole after porting??? I'm going to take away as much metal as I dare. I'd like to get her under 20.

 

[RUQWKNF]

It's pretty much manditory to port the wastegate hole on any P-trim turbine wheel equipped turbo, in order to get the boost levels below 20 and under control. IE: No boost creep.
Also, when running a HD wastegate actuator, you will be lucky if you can get the boost down to 18psi. The as casted hole on a PTE turbine housing should be around .900". Typically you would port this hole out to around 1.25" or just smaller than the diameter of your puck on your downpipe. And the last most important thing is to make sure, make double dang sure, that you have a nice landing mark on your turbine housing, before you start porting the turbine housing. (Landing mark typically shows itself up in the form of carbon / soot marks.) With the puck locations on all the downpipes varying by as much as 1/2" in some instances, you can see why this is such a crutial thing to get right. If you port the wastegate hole too far off to one side of the hole or another, you could actually create a gap. This would lead to very, very slow spool up and no boost control.

When we ported my new THB3-76 housing, I ran it for a week with the hole unported, just long enough to get a nice carbon trace. Then, removed the turbine housing, traced the hole with an egravers pen and circle template that was just smaller then the OD of the puck on my TH downpipe, leaving somewhere around 1/16th of an inch for the puck to seal on, then went to grinding. Don't forget to blend the ported area smooth for better flow.
Now, with a Heavy Duty actuator, I can turn the boost all the way down to 18psi. I've run up to 28psi so far, but it killed my tranny last fall.
Hope this helps.


Patrick

 

[Otto J]

Follow what Patrick said,If you dont want to wait for the carbon to build i have taken hte ex housing off the turbo,bolted it to the downpipe and
sprayed paint in the pipe opening and it left a mark where the puck sits

 

[87natl]

I've already been at it. Taking a break right now.

I did the exact same thing, Patrick. Ran it for a few weeks unported so that I would have a good mark. I've bee back blending the port as I go so that I have a smooth transition. I'm just a tick over 1" right now. What was funny to me is that I don't have a creep issue, rock solid at 23psi all the way to 120. However.....

I noticed that exhaust has been blowing by the mating surface between the turbo and the header. May not be much of a leak, and I've heard nothing that sounded like an exhaust leak, but any suggestions on getting that to seal better?

Back to the grinder...........

 

[87natl]

Update......

Ported out to about 1.15", and rolled all the inner edges to smooth things out. Just took it out with the wife's eagle eye on the guage......ran it to 100+ several times....19psi, rock solid! Woot!!!!!!! Tried stabbing it from a roll, you name it, wouldn't go over 19. Cool, now I can turn it back up....

Thanks guys.

BTW - I ran a flat metal file across my old header flange, with the tube blocked off with rags , just smoothed it over a bit. Won't know if it stopped any leakage, but it can't be leaking much with the way this thing spools. INSTANT!

 

[RUQWKNF]

Good Deal!!!

As far as sealing is concerned there are two methods that I have used that worked well.

1. Use a thick layer of copper high temp silicone sealant on the entire flange surface of the downpipe. Let it dry for a day or two before driving the car again.
This is the way I have it now on my car and no leaks.

This next one might sound crazy, but believe me, it works just as well.

2. Axel bearing grease on the surface. You actually don't have to let it dry as it never will. What you are doing is, burning the grease so that it forms a carbon seal. This can be messy and it doesn't take much, but it will seal.

Eitherway, we need to seal both flanges. Letting it go for too long will eventually dirty up everything underhood. Been there, done that.

For the header to turbo, I use a copper SCE 4172 gasket with a good amount of copper silicone sealant and let it dry for 2 days before driving.

Good job on the porting. I'd use Copper high temp silicone if it were me.
HTH


Patrick

 

[MikeL.]

87Natl...We have roughly the same setup. The lowest boost I could attain was 19 but I was using Jason's boost controller also. I'm not sure if that prevented boost spiking or creep but my unported 6765 isn't running into the issues you outlined...yet. I'm having fun on the street waiting for my carbon ring to build up.:biggrin:

 

[John Wilde]

subscribing

 

[87natl]

87Natl...We have roughly the same setup. The lowest boost I could attain was 19 but I was using Jason's boost controller also. I'm not sure if that prevented boost spiking or creep but my unported 6765 isn't running into the issues you outlined...yet. I'm having fun on the street waiting for my carbon ring to build up.:biggrin:

The extra cubes in my case may be adding to it. Everything is ported to death, and the engine is beathing freely. My WG hole, on the other hand, was clealry NOT. LOL!

Hey, I'm happy with being able to get it down to 19. That's satisfactory for me. I've ported out my previous units, but they, without the porting, would creep or spike. This one didn't do that. Just shot to 23 and hung there.

One part of the story I didn't tell.....after getting my freshly ported turbo back on and we went for a test run, aparently at 18psi my up-pipe popped off violently enough to ding up my hood pad. Dammit, I swore I checked all those calmps!!!!!! Doh!!!!!!!!!!!

I'm glad I keep a set of nut drivers in the trunk.