Understanding my boost behavior

[SDrake]

I bought my 2003 ho Cummings, leaving a 94 to my son. On the 94, I had changed fuel plates beefed up the transmission and upgraded to a triple disk converter, routinely ran just under 30 lbs boost towing on interstate grades.

On the 2003 I was puzzled that it only boosted to about 22psi at max throttle on same grades. Never would go any higher. After about 8 years I noticed something i had not noticed before. Coming to a grade at around 22 hundred rpm, when I punch the throttle the boost will rise quickly to around 25 or 26 then instantly drop back to 22.

I am wondering if something is not adjusted to best setting for goodboost. I understand the 2003 boost is waste gated differently than my 94. Is the computer limiting boost?

So is this normal that the boost on a stock 2003 would overshoot and settle back in this manner?

i have a bigger trailer and would appreciate some extra power and if there is something maladjusted that is limiting the boost I want to fix it. Then I am headed to a smarty jr and atransmisssion upgrade.

 

[DaveHess]

SDrake, I have no idea if this is right or wrong but I put an adjustable boost elbow on mine and then played with it for several hours. Right now, I have mine adjusted to where the boost elbow is not allowing any thing through it. The most boost I have ever seen is 29PSI and do not see EGT over 1200/1250. That EGT is usually for a very short time during long grades fully loaded. Normal towing EGT is around 800 to 1000. The boost elbow has been set closed for about 5 years and I have not experienced any codes or malfunctions. I do have a Smarty Jr. set on Tow. I tow a travel trailer and we now go across the scales at a tick over 18,000 GCW. I hope this helps.

 

[AH64ID]

The 2003 has a mechanical wastegate than can be adjusted by an adjustable boost elbow, as Dave mentioned.

On the HE341 I think 30 psi is a good number for the wastegate to open.


If you're interested in a Smarty Jr (great choice) I have one for sale in the classifieds.

 

[Tuesdak]

The Smarty will wake it up for sure! Specifically getting rid of the roll off of power near max RPM and raising the RPM limit.

A rework of the turbo at Turbo Resource (Lake Havasu) appears to get improved results. (I run a different BB turbo altogether myself.) Boost is a fickle number dependent on load and will spike during transient conditions. The question to ask is the turbo, at any boost number, blowing out the smoke? Then you have enough boost. No need to increase backpressure for boost #'s you are not using.

 

[SDrake]

Thanks to all. The 2003 ran so well when I got it that I was just never motivated to tinker around and learn the setup. On the ther hand. My 94 started out with stock 165 HP. it didn't take much to get it to around 300 HP. The 2003 towed similarly.

I do get a bit of smoke, hard to see in rear view unless light is just so but can usually see it on the full throttle up hill climbs. That told me I could use more boost and wondered why I was not getting it. I am going to start with the adjustable boost elbo and tinker awhile. Is there a line I can pinch to just see what happens with the boost?

At any rate it looks like I am headed for a bit of fun upgrading my power a bit. Too bad I can't expect a 80% jump for an investment in a fuel plate , a set of governor springs kind of thing. I did put a 4" exhaust from turbo back when I got the truck, and 1/2" fuel lines when I installed the fuel filter upgrades.

 

[Tuesdak]

I thought the same about my 2003 till I put the Smarty on it. Then I kicked myself for waiting so long... :-laf

 

[Prairie Dog]

My 03 ran about 25~26 PSI originally. Now it will peak at about 34 and drop to 32. I adjusted the wastegate and a boost elbow did the rest along with a SmJr.
I think your boost level is a little low. You could either adjust it or just use an adjustable elbow with the smarty.

 

[SDrake]

My 03 ran about 25~26 PSI originally. Now it will peak at about 34 and drop to 32. I adjusted the wastegate and a boost elbow did the rest along with a SmJr.
I think your boost level is a little low. You could either adjust it or just use an adjustable elbow with the smarty.

It appears from what I see on mine and what you just reported about the peaking and then dropping back a few psi is the boost just doing its thing, but I am low. Others have not addressed that particular behavior but are unanimous that I can wake this thing up pretty easy by Smarty Jr and adjustable boost elbo.

Shouldn't I be seeing higher than normal exhaust temps on the long hard pulls if I am under boosted and putting out a bit of smoke, very light but definitely not completely clear exhaust? Just another thing that I found at variance with what I thought I understood about the fueling and air equation.

The truck still idles very nice, starts quick and with 170K and not a drop of oil leaking, still lots of life to go. I am looking forward to that , "what on earth took me so long" feeling.

 

[AH64ID]

I am not sure that 22 is low. From what I recall the wastegate should hold right around 23 psi. Minor differences in gauges, as well as boost reference location will have a small impact on what you read on the gauge.

I saw a 1-2ish psi difference when I read boost in the OEM intake elbow vs the intake manifold. The design of the OEM intake elbow causes a minor restriction that can be seen on a boost gauge.

 

[SDrake]

I am not sure that 22 is low. From what I recall the wastegate should hold right around 23 psi. Minor differences in gauges, as well as boost reference location will have a small impact on what you read on the gauge.

I saw a 1-2ish psi difference when I read boost in the OEM intake elbow vs the intake manifold. The design of the OEM intake elbow causes a minor restriction that can be seen on a boost gauge.

I know my truck runs great and pulls nice until I have reached the limits of its power.

But now I am still curious with that peaking and dropping back a few psi. Is that just a lag in the ability of the boost control mechanism to respond. Or does it signify that something is sticking that could be fixed?

 

[AH64ID]

I know my truck runs great and pulls nice until I have reached the limits of its power.

But now I am still curious with that peaking and dropping back a few psi. Is that just a lag in the ability of the boost control mechanism to respond. Or does it signify that something is sticking that could be fixed?

It's normal for a wastegate to allow the boost to go up a bit higher and then settle on its adjusted setting.

 

[DaveHess]

SDrake, In post #5 you asked about pinching the line. That's what I did and drove me to the adjustable boost elbow. I pinched the rubber hose from the elbow to the waste gate and saw the change on my boost gauge. I also am running an ATS Arc-Flow intake tube. I do not know what effect that has on my boost readings since I am reading my boost off of a port on the back side of the intake tube. That intake tube is considerably larger that the stock tube which has always made me wonder if there is a pressure drop when the boosted air hits the "openness" of this intake tube. Or does the air slow down in the ATS as opposed to the stock tube. As for smoke, the only time I can visible see smoke from mine is if I have been idling say at a traffic light, and then roll into the throttle when pulling my travel trailer and even then it only puffs for about two seconds or so. My thoughts is this was because the engine or turbo "loaded up" at idle and the subsequent increase in RPM cleared the exhaust until the turbo came up in RPM causing the visible black smoke to go away. I really have no idea if this is right or not.

 

[Prairie Dog]

SDrake, In post #5 you asked about pinching the line. That's what I did and drove me to the adjustable boost elbow. I pinched the rubber hose from the elbow to the waste gate and saw the change on my boost gauge. I also am running an ATS Arc-Flow intake tube. I do not know what effect that has on my boost readings since I am reading my boost off of a port on the back side of the intake tube. That intake tube is considerably larger that the stock tube which has always made me wonder if there is a pressure drop when the boosted air hits the "openness" of this intake tube. Or does the air slow down in the ATS as opposed to the stock tube. As for smoke, the only time I can visible see smoke from mine is if I have been idling say at a traffic light, and then roll into the throttle when pulling my travel trailer and even then it only puffs for about two seconds or so. My thoughts is this was because the engine or turbo "loaded up" at idle and the subsequent increase in RPM cleared the exhaust until the turbo came up in RPM causing the visible black smoke to go away. I really have no idea if this is right or not.

Mine acts the exact same way when I'm towing our travel trailer.

 

[SDrake]

SDrake, In post #5 you asked about pinching the line. That's what I did and drove me to the adjustable boost elbow. I pinched the rubber hose from the elbow to the waste gate and saw the change on my boost gauge. I also am running an ATS Arc-Flow intake tube. I do not know what effect that has on my boost readings since I am reading my boost off of a port on the back side of the intake tube. That intake tube is considerably larger that the stock tube which has always made me wonder if there is a pressure drop when the boosted air hits the "openness" of this intake tube. Or does the air slow down in the ATS as opposed to the stock tube. As for smoke, the only time I can visible see smoke from mine is if I have been idling say at a traffic light, and then roll into the throttle when pulling my travel trailer and even then it only puffs for about two seconds or so. My thoughts is this was because the engine or turbo "loaded up" at idle and the subsequent increase in RPM cleared the exhaust until the turbo came up in RPM causing the visible black smoke to go away. I really have no idea if this is right or not.

Again thanks everyone. This has turned out to be more interesting than I thought. I want to pinch the line and just watch and prepare for Smarty Jr.

 

[Killer223]

if you don't tune with the smarty you'll get an over boost CEL and the computer will defuel.

 

[SDrake]

Killer223 I appreciate you not letting me find that out the hard way I assume it would reset after a while once pinch removed.

 

[DaveHess]

SDrake. Just for the record, even with my line between the boost elbow and the waste gate pinched off, I have never gotten a CEL or code. As I stated earlier, I have had the adjustable boost elbow installed and closed shut, effectively providing no signal to my waste gate, for about five years now with no codes or ill effects. I run my Smarty Jr on Tow and have left all settings on Default.

 

[AH64ID]

SDrake. Just for the record, even with my line between the boost elbow and the waste gate pinched off, I have never gotten a CEL or code. As I stated earlier, I have had the adjustable boost elbow installed and closed shut, effectively providing no signal to my waste gate, for about five years now with no codes or ill effects. I run my Smarty Jr on Tow and have left all settings on Default.

The Smarty Jr keeps you from getting an overboost code.

 

[DaveHess]

John, Will you settle something for me please? Since my boost gauge has not in any given situation over the last five years gone above 29 PSI, is it a safe assumption that even with the adjustable boost elbow shutting off the signal to the waste gate, that I am not causing harm to my turbo?

 

[AH64ID]

John, Will you settle something for me please? Since my boost gauge has not in any given situation over the last five years gone above 29 PSI, is it a safe assumption that even with the adjustable boost elbow shutting off the signal to the waste gate, that I am not causing harm to my turbo?

You shouldn't be doing any harm at 29 psi.

The adjustable elbow will still send air to the WG and allow it to open if the boost gets high enough, in your case that appears to be 29. IMHO it's a good setting for the HE341 for longevity.