Twin Turbo Question?

Just changed both Air Filters approx one month ago as usual cleaned the inside of the air cleaner before putting the new filters in and I dont use the cheap filter buy Donaldson straight from my local Peterbilt dealer. I might try pulling the air tube off one day to see if I can get more boost. 07 C15 475HP Acert... I tell you what throttle response on this truck sucks but I'm getting used to it..It doesnt seem to have the pep off the line as the old 96 378 with an 3406C had. Truck is ex A.N Webber so pretty much an old fleet truck just like yours!

 

Maybe the mods can move thread to the garage section..

 

I think it might be the 435hp setting,.. the ECM kicks the waste gate open before allowing boost to exceed too much power.

I have an 08 T660 with an 07 C15 625hp motor detuned to 475/1875.

I have the boost gauge as well as the Cat Messenger set up that shows what the ECM sees. My boost fluctuates all the time. I have seen as much as 40 PSI climbing hills,.. and other times never see more than 20 - 22 psi climbing similar hills,.. both times under a full load. I can say I do feel a difference in the pulling power from 38 PSI down to 22 PSI.

Part of it on this truck has to do with the DPF and while its regening, you can hear the valves tone change. I assume this is the ECM cutting back power and fuel so the DPF system can do its job. PITA if you ask me.

I love the torq this motor has when climbing various passes. But the majority of issues seems to always revolve around the ARD head and DPF system. I have been curious to know what these motors were like before they introduced the DPF into it. This is my first and only CAT. Always driven Cummins or Detroit before this.

Hurst

 

I know exactly what your saying about the throttle response. Was one of the first things I noticed. Just doesnt have that crispness or eagerness to rev. Almost like a slight hesitation before the throttle actually does something.

We have another truck with a 525 ISX Cummins and its night and day compared to the C15 in my truck. You get used to the 'soft' throttle response,.. I get in that truck and I find myself jerking the truck from a start because I've acclimated myself to how this one is. . Need to have a bit more 'finesse' with that one.

Hurst

 

Yeah me too. It's just the nature of a Cat I think. We have and '01 and an '05. They "feel lazy" but they will pull a hill.

 

ECM has no control over the wastegate. The wastegate is controlled by the amount of air pressure generated by the low pressure turbo. Also the wastegate doesn't control power, it controls boost pressure and compressor wheel speed.

 

Yes thank you, wastegates are mechanicly accuated by air pressure and a spring. If it is not adjusted correctly it can either open to early not building boost or not open at all and possibly over spin the turbo or cause other failures related to high boost.

 

I apologize then. I was told the ECM had some control over the boost.

Let me ask you this, turbo diesels are a grey area for me. But why does the C15 often cut off boost early,.. say only 20 - 22 PSI,.. while other times it will allow it to climb to 38 - 40 psi? What causes the fluctuation? Would temp cause the vacuum signal to be different?

In my home application, if I set a controller to blow off anything beyond 15 PSI for when I use 93 octane, my boost gauge never shows more (Or less) then what I set. It is what it is and hits my target each time. The boost in this truck seems to have a mind of its own at times.

Thanks, and again,.. I am sorry for any mis-information. Was not my intention.

Hurst

 

Your fuel temp will make the engine run with less fuel/boost until the fuel hits a certain temp. If your thermostat is stuck open you motor wont get warm enough to run at 100%. There is so many little things that can effect the parimeters that the ECM runs at.

 

No problem about posting what you thought...this is how we all learn together.

The difference in post pressure could be from many things like milskired said. One of the bigger ones is ambient air temp though. Cooler denser air produces more boost and the engine doesnt work as hard. Also if there is to many water grains in the air your boost will suffer. I am not that familiar with the DPF equiped ACERTs, but there may be programing in the ECM to limit fuel or HP when the DPF is in operation. This in turn would drop boost levels.