Low Boost

[TomJohnston]

I think we got this figured out. The diesel tech who work on my truck actually bought it so I got to talk to him for a few hours today. He says the y-tech is showing the boost jumping from 43psi which is max boost the MAP can show to 51psi which is impossible and with the boost fooler on it shows up to 36psi when the boostfooler is supposed to show a maximum of 26psi. I believe the computer takes the ambient pressure reading from the IAT sensor and the reading from the MAP and can do a combined rating inside the ECM. The MAP is what sets the overboost code at 36psi so you wont throw a code/CEL but the combined boost reading causes the truck to defuel. I have noticed that with my truck with no boostfooler it will cut fuel and do weird things before it throws the overboost code. I think that is the area we are in where the boost the truck is seeing is not enough to throw a code but the ECM is defueling to try and get boost down. So for some reason a standard boost fooler is not good enough for us. I think a resistor in line with the signal output of the boostfooler which would drop the voltage another . 2-. 5 volts would fix our problem or maybe attacking the pressure sensor side of the IAT.

I am almost positive that the whole problem resides in the boost input or we both have something internal to the ECM that is causing the boost signal to whig out. But it was obviously a problem when the ECM sees the boost jump from 43psi straight to 51 until you let of the pedal. We may not have a for sure solution but I am sure we have found the problem.



BTW, since the diesel tech bought my truck, he will get this resolved and let us know what the issue or fix is.

 

[cerberusiam]

He says the y-tech is showing the boost jumping from 43psi which is max boost the MAP can show to 51psi which is impossible and with the boost fooler on it shows up to 36psi when the boostfooler is supposed to show a maximum of 26psi.

Like I said, the ECU is seeing and outputting absolute pressure because thats what the MAP reads. The calculations to back out ambient and use just boost happen in the fueling algorithms which are the drivers for the base programming.

I think that is the area we are in where the boost the truck is seeing is not enough to throw a code but the ECM is defueling to try and get boost down.

Doesn't work that way, the boost tables go until whatever values are written into them correlated with MAP values. The ECU does nothing until the interpolation routines say OOPS no values to correlate, then it defuels till things are readable again. There is the possibility of a ramp down algorithm that would start to defuel at a percentage of max but limiting fueling at the levels means it is broke. Other trucks do NOT exhibit this behaviours so its specific to something.

So for some reason a standard boost fooler is not good enough for us.

Standard boost fooler works fine on many trucks, its a glitch specific to the flash or truck.

 

[TomJohnston]

I just want to be clear the y-tech would show boost rising all the way to 43psi and the jump straight to 51. example 1,2,3... 40,41,42,43,51

This doesn't make sense not a single digit from 43 to 51 just jumps straight to it. It like the op-amp for the signal goes haywire when it hits

43psi(5 volts). Wether I am explaining this well or drawing the wrong conclusions there is definitely something wrong with the way the ECM is reading or reacting to boost even with a boost fooler.

 

[cerberusiam]

I just want to be clear the y-tech would show boost rising all the way to 43psi and the jump straight to 51. example 1,2,3... 40,41,42,43,51

This doesn't make sense not a single digit from 43 to 51 just jumps straight to it. It like the op-amp for the signal goes haywire when it hits

43psi(5 volts). Wether I am explaining this well or drawing the wrong conclusions there is definitely something wrong with the way the ECM is reading or reacting to boost even with a boost fooler.

Now THAT is different. The signal maxes at 5 volts so its like an auto added value when the boost hits the end of the table. That would be something in the software doing that.



Wonder what happens when the boost hits the end of the stock tables? Does it jump the same way or amount? That would definitely make things defuel if it hit the end of the stock tables and immediately bounced to say 40 or 41 psi. Depending on how it defueled that could limit max boost at 34-35 psi.

 

[SShafranko]

Well i'm pretty excited about the fact that the tech bought your truck and i'm sure he will come up with a fix soon enough. I am also thankful to you Tom for still posting and keeping me updated as this is not your problem anymore but i'm sure that you are curious as to what the problem is. I can't thank you enough for helping me out.



The one thing i am concerned about is that we may have two seperate issues. My truck is behaving somewhat differently than yours is. I beleive that my truck is defueling throughout the entire rpm range and not only at top end. I cannot get past 35 psi and on some occassions even past 30 psi, as for you, you seem to be hitting the 50 psi range if i am understanding you correctly.



Well anyway i'm pretty sure that the solution to your ex-problem will help me greatly in resolving my current problem.



Thanks again and thans Cerb. for staying in the loop and helping also.



Sasha

 

[SShafranko]

I can't stop thinking about my injector harness. Its just about the only thing i havent changed yet. Would it be possible if there was a short or if the harness wasn't functioning properly that it could cause a defueling situation?



This is also my second ECM. According to the Dodge technician my first one was bad. If this one is now also bad than something is shorting it out. I am not going to replace this one until i find the cause. I think i am going to bring the truck in again next week to get scanned. Have to wait for some money to come in on Friday and then i'll go probably Saturday actually. I may as well bring it someplace that has the y tech available.

 

[TomJohnston]

Cerberusiam, One thing both of our trucks do that makes no sense is even with no electronics or boostfoolers, the truck will cut fuel and buck and surge at wot and then may or not throw an overboost code. All the trucks I know just throw the code and it doesn't seem to do anything to the truck. And why does the truck go all weird before throwing a code? shouldn't it happen at the same time or throw the code and then cut fuel. And it is always related to boost with or without a fooler.

 

[TomJohnston]

It's not the harness, this is all boost related whether it is not getting enough or the ECM seeing too much.

 

[TomJohnston]

Shasha, I am pretty sure that our problem is the same. Everyone that I have found with this problem have all had diiferent boost levels that correlated to the size of their injectors. Same problem but stock injectors 30psi, same problem 80hp injectors 40psi, go to 150hp injectors and no more problem. When the truck defuels it can only decrease timing and injector pulse width. If you have a bigger injector, even with it defueling you are able to get a lot more fuel into the cylinder which creates more boost. Also with bigger injectors your turbo is going to spool a lot faster and by the time it starts to defuel you are making more boost.



The dodge tech is in full agreement with me. The ECM is seeing too much boost with or without a boost fooler. I have 2 boostfoolers the one built into the Quad race that the tech said definitely wasn't fooling correctly and a standard Quad boostfooler that worked better but the ECM was still seeing too much boost. Why the ECM is seeing so much boost and not throwing a code I don't know. But I will tell you this, that tech paid 29,500 to buy my 2006 SLT Bighorn with 50,000 miles. He seems pretty confident that it is a ECM boost issue and he can fix it. I hope he didn't drop that kind of money to inherit a problem he can't fix.

 

[SShafranko]

LOL/ he must be pretty confident that he could fix it buying the truck and knowing the issue it has. Maybe somebody will finally figure this one out. He may just be the most popular guy on forums pretty soon.



Good for you i'm glad you got what you were looking for on your sale.

 

[AH64ID]

Exactly, its not boost fooling its WG off, which one can easily accomplish with a pair of vice grips. Pretty sure Sasha tried that and still had boost leveling out lower than it should.

But clamping the WG without a boost fooler or smarty will trip an overboost code.

I think we got this figured out. The diesel tech who work on my truck actually bought it so I got to talk to him for a few hours today. He says the y-tech is showing the boost jumping from 43psi which is max boost the MAP can show to 51psi which is impossible and with the boost fooler on it shows up to 36psi when the boostfooler is supposed to show a maximum of 26psi. I believe the computer takes the ambient pressure reading from the IAT sensor and the reading from the MAP and can do a combined rating inside the ECM. The MAP is what sets the overboost code at 36psi so you wont throw a code/CEL but the combined boost reading causes the truck to defuel. I have noticed that with my truck with no boostfooler it will cut fuel and do weird things before it throws the overboost code. I think that is the area we are in where the boost the truck is seeing is not enough to throw a code but the ECM is defueling to try and get boost down. So for some reason a standard boost fooler is not good enough for us. I think a resistor in line with the signal output of the boostfooler which would drop the voltage another . 2-. 5 volts would fix our problem or maybe attacking the pressure sensor side of the IAT.

I am almost positive that the whole problem resides in the boost input or we both have something internal to the ECM that is causing the boost signal to whig out. But it was obviously a problem when the ECM sees the boost jump from 43psi straight to 51 until you let of the pedal. We may not have a for sure solution but I am sure we have found the problem.



BTW, since the diesel tech bought my truck, he will get this resolved and let us know what the issue or fix is.

The ECM reports boost in absolute, so 0 psi reads 14. 7 to the ECM on a standard day. Or 32 psi (WG trigger) will read 46. 7 on a standard day, and max boost is actually read as 57. 7.



Not sure if thats what the tech is seeing or not, but I have talked to techs that swear up and down these trucks make 45+ lbs of boost stock, becuase thats what the DRB or Starscan, now Wi-Tech tells them.

 

[SShafranko]

Could a bad cascade overflow valve on the cp3 be causing my loss of power and low boost issues?

 

[cerberusiam]

Could a bad cascade overflow valve on the cp3 be causing my loss of power and low boost issues?

Its possible. Didn't you replace the CP-3 or upgrade to the Arson kit? There is not a lot than go wrong with a COV but its possible for them to throw subtle things into the mix. Somehow I was under the impression all the CP-3 things had been addressed?

 

[SShafranko]

No i never changed the CP3. I did switch out the FCA with my buddies truck to no avail but my truck is running a lot better since i installed the new ECM. I wonder if my ECM was so bad that all the sensors i switched out will have to be done again with the new ECM?



Pulling out the cov right now and i'll blow some air through it to see if it seats properly.

 

[SShafranko]

Took the valve out and cleaned it. I pushed it in with a pen and it seems to operate properly. It moves in and out freely so i guess it works.



The one thing which probably is the most important part of diagnosing an issue such as mine i have been overlooking. I never hooked up my rail p gauge or checked to see what my rp is at idle, cruise or wot. I did switch out the rp sensor and the releif valve with the old ecm but i never actually read the pressure. I am going to install the gauge this week and see what happens.

 

[cerberusiam]

The one thing which probably is the most important part of diagnosing an issue such as mine i have been overlooking. I never hooked up my rail p gauge or checked to see what my rp is at idle, cruise or wot. I did switch out the rp sensor and the releif valve with the old ecm but i never actually read the pressure. I am going to install the gauge this week and see what happens.

Oh, thought you had a rail pressure gauge and all was good. My bad for not asking.



You list a Stage 1 CP-3 in your sig, whats that entail?

 

[SShafranko]

I really should change that because it is a misrepresentation of what i really have. I modded the FCA myself about two years ago and called it a stage one which is wrong. Sorry about that. I have a rp gauge and turns out it is broken so i just ordered one and they told me i'll have it in 2 weeks since it is special order. Autometer came out with new gauges specifically for our trucks which match the factory gauge closter graphics and light up the same color as the factory cluster. I can't wait that long but i guess i have no choise.

 

[cerberusiam]

I really should change that because it is a misrepresentation of what i really have. I modded the FCA myself about two years ago and called it a stage one which is wrong. Sorry about that. I have a rp gauge and turns out it is broken so i just ordered one and they told me i'll have it in 2 weeks since it is special order. Autometer came out with new gauges specifically for our trucks which match the factory gauge closter graphics and light up the same color as the factory cluster. I can't wait that long but i guess i have no choise.

That clears up a lot. Thought you had a Stage 1 from II or somebody that should be good. If I were you I would invest in an Arson III and see if that makes a difference. Suppose dto be a pretty good upgrade.



Did you check with Genos on the gauge? They had it in stock when I got mine but they may be popular. Works really well and matches the factory gauges nicely.

 

[SShafranko]

Update

Ok problems solved. Since i installed the new ECM the truck runs very smooth, and the cutting out at WOT is completely gone. The only issue i had now is cannot boost past 32-34. I decided to try pinching the WG hose again with the new ECM and boom boost shot to 45psi.



I did pinch the hose with my old ECM also but i guess since it was bad it was not allowing me to fuel past a certain point by cutting out. So now obviously my WG is opening prematurely. Is it messed up or does it need to be adjusted? I feel better performance, quicker spool, more boost throughout the entire rpm band. If it has to be adjusted i do not understand how without taking the turbo off since the rod is so far behind the turbo i cannot reach it.



Todd is sending me an edge elbow. Will it work ok on my turbo?

 

[cerberusiam]

Yep, boost elbow in the reference line to tune when your WG opens. The 32-34 is pretty normal boost range but you can use more when needed. Glad you got it figured out.