Boost leak/slow spoolup questions

Cummins Driver

Cummins Driver

THE Cummins Driver
Joined
May 16, 2007
Messages
2,405
Hey guys. Seems I am having a small problem with my truck. I modified a 3rd gen turbo to fit and have not had a single problem out of it so far. Its been on for at least 2 months. Anyways, I am having a spoolup issue now. I used to be able to make 10-12 psi in overdrive at 1200rpm. Tonight, 5-6psi was it, and it just felt really dead there. Normally I can have it fully lit by 1400rpm or so if i really try. Tonight, it was more like 1600rpm. Once it gets up on the charger though, it still makes full boost. I have it gated about 38-40psi, and in overdrive tonight, It was making 40psi on a hard run. Just wasnt spooling like it normally does on the bottom end.

I looked it over in the dark with a flashlight, and couldnt find anything obvious, but would a small boost leak cause this? I have a piece i built to pressurize the intake system with air, so I will probably look at it either tomorrow or Sunday after church. I was just looking for opinions on what it could be. The boot on my charger looked fine, and the piping looks just fine too. Im wondering if it could possibly be the boot going into my intercooler from the turbo, but i dont know for sure.

Turbo spins very freely, and has no in and out play. Sounds fine, and makes full boost with normal side to side play, so i dont think anything is wrong with it, and I dont see any exhaust leaks. Havent had the intake horn off recently either, so i wouldnt think it would be those gaskets.

What has me kind of wondering more than anything is that it still makes full boost. I have it gated around 38-40lbs, and it still makes that, although with the wastegate blocked, it would make 48psi, so its possible, it has lost 6 or 8 psi, but will still reach enough boost to get to where i have it gated.

Anyways, any ideas are appreciated. Im sure the best way to do it is to pressurize the system, so ill be doing that soon and updating then. Until then im accepting ideas:poke:

Eric
 
Are you sure the WG is closing all the way and not hanging open? And yes a small boost leak will cause you to loose 5-10psi but its a constant lose so i would pressure rise the system and check for leaks then check the WG to see if its sticking.
 
can you hear it leaking at all when your first building boost? I guess a small leak could prevent it from getting started as quick. Id say check your piping and boots and if nothing found check your air cooler, we had a guy come in the other day and all connections were all fine but it was leaking out of the cooler.Good luck
 
mondtster said:
Don't forget to check the intake plate.
Click to expand...

x2.

I had to use red glue on the intake plate gasket to make it stay put. The first replacement gasket with slightly over-torqued bolts only lasted a few months.


FYI, don't go too tight on the intake plate bolts, the cast ears they thread into are prone to breaking.
 
Thanks guys. I plan on looking at it tomorrow afternoon.

As for the wastegate not shutting fully, I thought about that, but I dont think it is the problem. I wont rule it out yet though.

Eric
 
check exhaust side pre turbo like a champ. That would cause slow spool and lower boost, more so than a small leak in the intake side, because a small one will not leak as much in the lower boost as it will in higher boost.
 
Well, maybe im retarded? :nail:

I didnt drive the truck any yesterday because my buddy wanted me to take his 6.7 cummins to a dyno day and run it, and then i drove it the rest of the night since he is in Florida working right now. Couldnt say no to driving a 533hp 6.7 cummins :rockwoot:

Anyways, I got in it this morning to go to church, and it has been great all day. I can build 10psi by 1200rpm again. Drove about 10 miles to pick up my fiance and then into town to get lunch, and back and it has been good.

Anyways, its dry today, and when it was acting up the other night it was raining, so the only thing i can figure is the humidity was hurting the spoolup and i just hadnt noticed it before?

Either way, it is working fine now, so It looks like i dont have to work on it today. I do know something was definately different with it the other night, but I am chalking it up to the weather.

Anyone else noticed this before?

Eric
 
Well, its acting up again. It never acted up this morning, but i never got on it in full fuel. The gate doesent open in valet i dont believe.

Anyways, I got on it hard on the way home tonight and after that it started spooling slow again. I think the gate must be sticking open some for some reason. I guess I will try and mess with it tomorrow. I might just make a manually adjustable wastegate rod with a spring under the adjusment nut to hold tension on it. It would be easily adjustable, and extremely simple.

Im not sure why it would be acting up though? It hasnt done this before and the turbo has been on for about 2 months.

Eric
 
Are you using the stock wastegate actuator in the stock configuration? If the answer is yes, remove the actuator, drill out the small pressed pin/ pin-sized crimp so you can turn the threaded end. I shortened mine about 3 turns to help fully shut the wastegate and keep it from blowing open till the actuator pushes it open.

Once you remove the actuator, it's a ten minute job drill out the crimp and make the actuator adjustable. Once you shorten the rod, you have to use compressed air to help install the actuator. It's a tight working space with the turbo installed and a little compressed air makes the reinstall ten times easier.
 
I am using the stock actuator, but I made my own bracket for it. When i put the rod on, I had to pull it out some with pliars to get it out far enough to get it on the arm on the exhaust housing so it has some preload on it. It has been fine up until now though. I just think it has to be something with the gate though, since it didnt start acting up again until i ran it hard in full fuel on the way home yesterday(which made it open the gate). Something may be binding up. The wastegate rod is at kind of an angle, so it may not be working quite as well as it should. I know it always opens consistently though.

Anyways, I have to pull a 2550 john deere in half today so i can put a clutch in it for my uncle, but I should have time to look at my truck, so hopefully i can figure it out.

Here is a pic of my gate setup:

Eric
 

Attachments

  • 3rdgengate.jpg
    3rdgengate.jpg
    96.8 KB · Views: 14
Well, i shot some WD-40 on the gate setup today and drove to town and back and everything seemed fine the whole time, so maybe it was just getting bound up a little? I hope so, but so far so good now.

Eric
 
You must log in or register to reply here.
Back
Top