Hey everyone.

I've been battling severe turbo lag lately on my 2005 PSD, and I'm out of ideas. Here's what I've checked/done so far;

1. EBP is working? I'm not understanding the readings though. At idle it's showing "400", under heavy load it'll go to "600". I thought normal readings were 103 at idle and 110 at high idle? Could this be my problem? A bad EBP sensor? The value changes with rpm, so I am assuming that the passage isn't clogged.

2. Fresh rebuilt turbo. VGT readings vary from 15 to 85 as it should. It has the old style pressure line, but it's not leaking.

3. EGR cooler is deleted, but valve is still in place and connected. It never opens though, according to torque as it just stays at 0.0% (but did move prior to the delete) and I never get a CEL. This truck is not tuned. I installed a EGR delete up pipe also. There is no exhaust leak.

4. New CAC. The truck will boost to over 22psi (torque reverts to vacuum after 22psi for some reason).

5. Fresh oil cooler and coolant flush, deltas are in 8 degree range.

6. IPR (also new) at idle is 23.5-24, ICP is 580 and I don't get any codes when I pull them.

7. Fresh 5w40 synthetic and filter.

8. New batteries, alternator and positive battery cable assembly.

9. FICM holds 48v/13v/13v with no problems.

10. New fan clutch.

The lag happens just off idle to about 1800 rpm. Sometimes the power comes on sooner, but I can manipulate it a bit. For example, if I floor it from a stop, the lag will last until about 1600-1800 rpm and then power will come on. If I give a little pedal, then follow with full throttle, there is little to no lag and it pulls vary hard.

I am able to get the turbo to fart and the air filter is new. I don't suspect a boost leak as the CAC is new and the boots all look good (I just had them all off)

Also, on occasion, it take about 3-4 seconds for the truck to start when cranking. I don't know if this is normal as I bought the truck with an ICP leak (STC fitting) and it's always started like this since I've owned it. My old '95 7.3 would turn over twice and start. This just seems a little slow to me.

The last pending code I had after the top end rebuild was about a month ago for a "Cylinder #4 contribution/imbalance". I attributed this to air in the HPO system and cleared it. It hasn't come back.

 

Sounds pretty normal to me, yes you will get an almost "dangerous" amount of lag flooring it off the line, just brake stall if your merging traffic from a stop or something, don't know why torque goes funny after 22 psi but anywhere from 22-28 is normal.

 

thought ebp should look like map readings? you must be using something other than psi.

 

EBP, MAP, BARO should all be the same until you crank it up. Then MAP and EBP go up with throttle, BARO doesn't move (with a storm coming it will).

Running a stock exhaust pipe? If your running a 4" from the turbo back, make the down pipe a 3.5" and lag will go down.

Normal crank is a 2-5 seconds, at least mine is. FORD says a long crank is 30 seconds.

Get a tune and lag will go down. Ease into the throttle and then tromp it, no boost until 1600-1800.... that's about the stall speed of the torque converter. Sounds about right to me.

Add a ground cable from drivers frame to block, voltage will go up and clean all the grounds where they touch something other than a battery terminal.

Your using the wrong settings on your gauge, should get around 25lbs boost.

 

Thanks everyone. It's nice to know that it's working correctly.

 

I'll second the 'get a tune and your lag will go down' comment. The difference when running the Atlas 40 tune vs latest Ford flash is incredible. The stock configuration is, to me, down right dangerous from a lag perspective.

 

Make sure you don't have a bellows or y pipe leak.

 

Covered in step 3.

 

I noticed that you're rocking the Atlas 80, so you really shouldn't have too much of a problem with Turbo lag.

A few things I'd look at:

EBPS, tube, and fitting at the exhaust manifold- People normally clean the sensor and call it good, but you need to go further. Tube itself becomes clogged afterawhile and must be cleared with carb cleaner and a wire brush. This is also true with the fitting at the exhaust manifold. It wasn't until I cleaned the fitting itself that I found it was plugged with carbon, causing my lag, and black smoke from the turbo not boosting properly.

MAP nipple on the intake manifold-When the EGR is deleted, as sad as it sounds, people don't take the time to properly clean the gunk out of the intake manifold. The EGR recirculating black smoke through the intake for years leads to the MAP nipple getting clogged with soot over time. When it becomes clogged, the turbo will not boost properly and will lag similar to what you're experiencing. You can clear it with either a wire hanger or a straw from a can of WD-40.

Downpipe-How big is the downpipe on your truck? I've noticed a severe lag with the 4 inch downpipe I ran on my truck. It didn't matter how hot the tunes were (ran the Atlas 40 and 80 with TSD SPD, Gearhead SRL+, and SRL Extreme) it ALWAYS had a lag at the bottom until the turbo caught up in the higher RPMs. Since I've gone with a 3.5 inch downpipe, I no longer have any issues with lag and my truck responds SO much better overall. What people fail to realize is the science behind the exhaust for the 6.0. Ford and/or International gave the 6.0 a 3 inch downpipe to a 3.5 inch after the CAT exhaust. (The truck is also programmed as such) The science behind it is that the VGT needs backpressure to spool (i.e. fill the downpipe with air) then it can fill the rest of the 3.5 inch pipe easily once it spools. When you go to a full 4 inch system, sure you're eliminating backpressure, but you're also making it harder for the turbo to spool as it has now has to fill a 4 inch downpipe before you get anywhere. This is why some people feel like they lose low end torque with a 4 inch downpipe it's because they do. You're essentially moving all the power higher in the RPM due to the turbo needing more time to properly spool. With a 3.5 inch downpipe, you have better power at the bottom and throughout the RPMs. The only reason I see for someone to go with a 4 inch downpipe is if you're running a bigger turbo AND 190/100 injectors or larger.

 

I was more then impressed with the Atlas 40 tune when I got it as far as turbo lag.


Did you have any of that recent work done at a ford dealer? If so maybe they flashed your FICM and you are now back to stock. Going from the Atlas 80 back to stock would probably make a huge difference in the lag.

 

Hah! I guess my increasingly older eyes didn't notice in your signature line that you are already running the Atlas 80! Good snag, guys!

That said, there is NO DOUBT that if the truck has been re-flashed, that you'd be back in lag territory.

Do you have any idea as to whether this is the case?

 

See in red. I have verified that the lag is normal, I just have never driven a "healthy" 6.0L before. I came from an OBS 7.3L with a wicked wheel and the spool was much faster. I just have to remember that this truck has lag down low when I'm towing.

 

I actually did have some work done, just after the FICM was replaced. I'm beginning to think they may have flashed it back to stock.

 

If they flashed it, makes sense. Killed a $150 bux!

 

Where did you get the tune from initially? If from us, we'd help you get back to what you had. If not from us, we'd STILL help you get back to what you had - we're just that way.

If nothing else, if you shot the module our way, we could tell you for certain what is on it.