I've got an LS swapped project that originally had a 4.8L and the turbo off of a 7.3L PowerStroke, and has now moved up to an LQ4 and an S475. I know that this is a common combo, and so I was it expecting it to be relatively responsive, but I've managed to end up with something that just is not working right at all, and I'm at a bit of a loss for what the issue might be.

Setup is a totally stock '06 LQ4 with 270k on it, PAC-1218s, the Elgin 1840P cam (228/230 .585/.585, 112LSA if I remember right), a 4L80e with a stock converter (plan on upgrading before too long), out to a rear end with a 4.10 gearset and 235/65R15s. Truck weighs about 2400lbs if I had to guess. Hot side is a truck manifold setup I built, twin 2.5", one to each half of the T6 flange. Has a 44mm VSRacing WG tied into both of them near the turbo. Exhaust is 4" the whole way back. Cold side is a 2.5" setup running through a 3"x6"x30" ebay intercooler.

I've got some HPtuners logs and the tune that I'll attach. I just cannot get the thing to come up on boost at all. In fact, at high RPMs, it's choked down to like 5psi absolute and hits an air limited rev ceiling. If I roll into the throttle very slowly, it will spool the turbo up better, which I got at about the 10:20 mark on the log. At about the 7 minute mark, I tried break standing it. Engine had enough to break the tires free, but just stopped revving at about 4k rpm. The fueling needs a little work, though the log didn't record the wideband, so you can't see that. It doesn't break up or anything, just stops revving.

I don't know if my issue is a hot side issue, a cold side issue, tuning, or just a poor combination of parts. I got lulled into a false sense of self assurance after the 4.8L and powerstroke turbo worked extremely well with very little effort, and I'm not too sure how to proceed now. Hoping somebody can point me in a good direction.

 

can you post your config? i cant tell if its supposed to be 2 bar or 3 bar.

 

The config is a 2bar. I'm running the 2bar MAP from a supercharged 3.8L, as I had it already. Got my channel config attached

I checked the wastegate to be sure, and it definitely does not appear to be opening. I added another spring in it to be sure. How big of a hotside or coldside leak would have to be present to act like this?

I was reading build threads for other 6.0/s475 builds, and saw that some people were already into boost by 2500rpm. My turbo doesn't even begin making a sound until 2500. I also wanted to add that if I slowly lay into the throttle, it does seem like it will start to wind up the turbo, but snapping the throttle open lets the engine just outrun the turbo and then the turbo won't get going at all.

 

Is the turbo 2nd hand? I had a turbo go bad on me years ago, and while it didn't leak past the piston, the bearing would seize up and wouldn't allow the motor to rev when leaned on. It did the exact same thing that you are describing.

 

Turbo is a brand new VSracing clone.

 

Fire rings in the gates?

 

Fire ring is in there, yes. I'll try being sure no exhaust is coming out the gate, but when I pulled it off last night, there was a noticeable line around the gate where exhaust sooting stopped at the fire ring sealing surface.

 

Looks like when you are at wot your map is decreasing as rpm increases. At one point at wot you were at 5000 rpm and 44 kpa. According to your log you never made any boost. Is your map sensor reading 100kpa with the engine off?

 

Yeah, the manifold pressure takes a dive as RPM increases because the turbo won't spin up at all and apparently pulling air through the turbo doesn't work too well.

MAP reads 13.9psi engine off, which at my elevation of like 2600ft makes sense. I drove the truck pre-turbo with the same MAP before without issue.

Though, actually, I took the truck out for a spin before I plumbed the cold side (intercooler hadn't shown up yet), and it was hitting a rev wall like that at like 4000rpm. I had been an idiot and plumbed the wastegate reference to the same line that the MAP is tied to, and figured that was the issue. I've changed that since. I wonder if it's possible that it was something else...

 

So it wouldn't pull past 4000 even NA? Quit lookin at the turbo. Fix that first. Look for any setting that references 4000 RPMs (rev limiter, fuel cut, ignition retard, etc.)

 

Sorry, I should have explained better. I've been running this same engine and basic tune for several months now. It has run perfectly until I started working on the turbo setup. I'm confident the rev issues I was having before was a mechanical issue, and not a tune issue. I'm going to go try and drive it again now with the added wastegate spring, and I'll record logs for that, as well as I'll stop and pull the charge pipe and verify that it works like it should without the turbo plumbed to the intake.

 

Here are logs for driving with the charge pipe and without it. Thing runs like a bat out of hell without the charge pipe. Turbo winds out much better too, just isn't doing anything.

After having been driving it around the last few days with it being a complete dog, the NA setup almost had me fooled into thinking it was properly turbo'd.

 

Strange, anytime my charge pipe blew off, the car wouldn't pull the hat off my head, AND the turbo wouldn't spool. Your situation is weird for sure.

 

 

I've checked the intercooler and charge piping a few times. I don't see anything obviously the problem. I think I'm gonna try doing a straight shot from the turbo to the throttle body and see what happens though.

I'll check the nut on the compressor wheel. Turbo feels nice and tight though having spun it earlier.

One thing to mention that I forgot to mention. I know even just sitting in the driveway in neutral, if I nail the throttle, the coupler at the throttle body gets buckled down by vacuum. Doesn't seem like that should happen. I wouldn't think 2.5" would be that much too small though?

 

Well, it seems I only thought it was tight cause it's a heavy wheel. This turbo has a solid mm or to of side to side shaft play... Gonna bet that could have something to do with it.

Guess I'm gonna contact VS and see if I'm just SOL or if they can do something for me.

 

So you ran it at WOT without the charge pipe attached? Good way to overspeed a turbo and destroy it.
Have you pressure tested the cold side? How about some pictures of the setup?

 

Holding WOT for like a second or two, I don't think I got this turbo anywhere close to overspeed. I said it wound out better, but it still did not wind up very far.

Here are a few photos of the hot side.




I haven't pressure tested the cold side. Given my ability to get the intake to like 9psi below atmospheric, I'm pretty sure I don't have a significant leak.

Playing with the wheel, I notice that if I side load it at all, it has a ton of drag, otherwise it spins nicely. I think my issue is the bearings have been trashed from shortly after the beginning. If I bring the rpms up slowly and avoid loading the turbo up too much it'll spin up, but heavy load all of a sudden and it stalls. Not sure why they failed so quickly in the first place though.

 

Did you run a restrictor in the oil feed line? I have heard on some turbos VS recommends using one, but on the larger turbos they do not.

 

post a pic of the turbine and compressor blades