Turbo Problem (I think) or is this normal? - Diesel Forum

james007calif · 03-27-2007, 02:45 AM

Does anyone else experience this? I have an 04 that I just loaded the SCT Extreme Steet tune in it for the first time tonight and took a test drive. When I accelerate aggressively and then let off to a normal cruising speed, my boost drops to zero with no get up and go, and stays that way until I get on it again with the turuck downshifting and the RPMs Rev. (which takes a few seconds to get it to react). It will also boost up again if I let off of the pedal completely for a few seconds and then give it some pedal again which drops it into a lower gear and higher RPMs. On the other hand, if I accelerate in a non-agressive mannor, when I hit a cruising speed the boost will stay at about 5 lbs and the power seems to be right there when I call on it. Is it normal for the turbo to completely shut down at times at highway speed or should it always be registering a little boost when cruising at a constant speed? I had the same problem when I had the Quadzilla in my truck too, but I was hoping it was just a programing problem with the quad. It seems to do this mostly when the truck shifts into overdrive with the lower RPMs.

teamroper60 · 03-27-2007, 02:56 AM

If I am understanding your question, what you are experiencing is normal. You have to be applying throttle to make boost. Generally, when you let off the throttle, your boost will drop to zero until you apply the throttle again... At a steady state cruise, there is steady throttle and thus some boost. 5lbs is about right on flat ground. But again, if you let off the throttle it most likely will go to zero. You can also experience this with the cruise on, if you start down a grade and it removes throttle input.

slow6oh · 03-27-2007, 12:51 PM

If you are experiencing what Chuck just described that is normal.

ciscofreak · 03-27-2007, 07:20 PM

Now what about when I am cruising 65-70 on flat ground and my truck is showing no boost at all at light throttle? It builds boost when I give it moderate throttle but at light throttle I get 0 boost.

I don't remember the 0 boost situation before my last turbo cleaning but it could have been like that all along.

Sorry about the thread hijack, I just figured this fit in this thread [img]/ubbthreads/images/graemlins/biggrin.gif[/img]

UNBROKEN · 03-27-2007, 08:44 PM

I never register any boost running on flat ground at highway speeds...on either of my boost gauges.

F250Attitude · 03-27-2007, 09:13 PM

It is normal to make no boost upon deceleration, meaning your foot is off the pedal. No reason for pressure to build when no fuel is present (throttle input). As far as not registering any boost at constant speed (light throttle) I wonder how your boost guages are graduated??? The factory guage on the '05+ models is 0 - 40psi. Mine sits at about 3-5 psi at a 70mph cruising speed on flat ground. I have a buddy with a Duramax who had an aftermarket DiPricol guage which spanned 0 - 60psi and it sat at 0 at cruising speed. He called DiPricol and they told him to get a 0 - 35psi guage and it would fix the problem and be more accurate for his application. And so it is. He now registers around 5psi at cruising speed. Not sure if this shed any light or not but for what it's worth.

teamroper60 · 03-27-2007, 09:40 PM

[ QUOTE ]
Now what about when I am cruising 65-70 on flat ground and my truck is showing no boost at all at light throttle? It builds boost when I give it moderate throttle but at light throttle I get 0 boost.

I don't remember the 0 boost situation before my last turbo cleaning but it could have been like that all along.

Sorry about the thread hijack, I just figured this fit in this thread [img]/ubbthreads/images/graemlins/biggrin.gif[/img]

[/ QUOTE ]

If you know for a fact that either you or the PCM is applying throttle, I would suspect your boost gauge to be at fault in this case.

james007calif · 03-28-2007, 01:37 AM

When I accelerate agressively to highway speeds and then cruise but still on the throttle a little, the boost drops to zero and the truck feels sluggish when I go to give it more pedal. But, if I take it to highway speeds at normal acceleration the boost stays at about 5 lbs and reacts much quicker when I get on the pedal again. hope this clears it up.

ciscofreak · 03-28-2007, 11:06 AM

[ QUOTE ]
[ QUOTE ]
Now what about when I am cruising 65-70 on flat ground and my truck is showing no boost at all at light throttle? It builds boost when I give it moderate throttle but at light throttle I get 0 boost.

I don't remember the 0 boost situation before my last turbo cleaning but it could have been like that all along.

Sorry about the thread hijack, I just figured this fit in this thread [img]/ubbthreads/images/graemlins/biggrin.gif[/img]

[/ QUOTE ]

If you know for a fact that either you or the PCM is applying throttle, I would suspect your boost gauge to be at fault in this case.

[/ QUOTE ]

Yea, this morning I noticed it was sitting just above the lowest mark (~1lb-ish) at freeway speeds with light throttle. I will have to take it in and have it looked at again.

F250Attitude · 03-28-2007, 01:11 PM

[ QUOTE ]
When I accelerate agressively to highway speeds and then cruise but still on the throttle a little, the boost drops to zero and the truck feels sluggish when I go to give it more pedal. But, if I take it to highway speeds at normal acceleration the boost stays at about 5 lbs and reacts much quicker when I get on the pedal again. hope this clears it up.

[/ QUOTE ]

Ok, after reading this I tried to recreate what you are talking about and I experience sort of the same so I will try to give an analogy that might help explain why this may be normal. The turbo diesel engine rely's on the turbo to force air into the engine to make power. Now imagine a garden hose sitting in front of your house. You turn it on full and water starts to flow but nothing is coming out of the end of the hose for a few seconds. Once the water has filled the entire volume of the hose it shoots out the end of the hose at a consistent rate. Now if you turn the spicket flow down low enough, air will creep it's way back into the hose filling some of the volume of hose. Now you reach back over and turn the spicket on full again and there will be some delay before the water starts flowing full pressure again. Much the same when your on the throttle heavy (or moderately) and then let off (even maintaining some slight throttle) and then you go to get back on it, the turbo must fully repressurize all the boost tubes, and the intercooler before it can start to build steady pressure (boost), ie: create power. This delay is often referred to as Turbo Lag and generally experienced worse from a dead stop. Do you also notice your RPM's drop to around 1500+/- when you let off the throttle at say 70? Anyway, I'm no Tech but maybe this will shed some shadetree light on the subject.

james007calif · 03-28-2007, 09:00 PM

[ QUOTE ]
[ QUOTE ]
When I accelerate agressively to highway speeds and then cruise but still on the throttle a little, the boost drops to zero and the truck feels sluggish when I go to give it more pedal. But, if I take it to highway speeds at normal acceleration the boost stays at about 5 lbs and reacts much quicker when I get on the pedal again. hope this clears it up.

[/ QUOTE ]

Ok, after reading this I tried to recreate what you are talking about and I experience sort of the same so I will try to give an analogy that might help explain why this may be normal. The turbo diesel engine rely's on the turbo to force air into the engine to make power. Now imagine a garden hose sitting in front of your house. You turn it on full and water starts to flow but nothing is coming out of the end of the hose for a few seconds. Once the water has filled the entire volume of the hose it shoots out the end of the hose at a consistent rate. Now if you turn the spicket flow down low enough, air will creep it's way back into the hose filling some of the volume of hose. Now you reach back over and turn the spicket on full again and there will be some delay before the water starts flowing full pressure again. Much the same when your on the throttle heavy (or moderately) and then let off (even maintaining some slight throttle) and then you go to get back on it, the turbo must fully repressurize all the boost tubes, and the intercooler before it can start to build steady pressure (boost), ie: create power. This delay is often referred to as Turbo Lag and generally experienced worse from a dead stop. Do you also notice your RPM's drop to around 1500+/- when you let off the throttle at say 70? Anyway, I'm no Tech but maybe this will shed some shadetree light on the subject.

[/ QUOTE ]Thanks BG, that makes sense and it doesn't sound like I am alone on this one. Great analogy by the way. Thanks for getting back to me. I have a long trip pulling my boat this weekend and wanted to know if I should have it looked at prior to the trip if needed. The truck seems to always act this way, it just is more apparent with the extra power of the Quadzilla and SCT.