Help!! C15 twin turbo MPG...

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Jeron379, Aug 15, 2009.

  1. Jas

    Jas Medium Load Member

    No hard feelings, You are as entitled to your opinion as I am to mine, thats what a forum is for, sharing of ideas.
    Cat definately dont make anyones life easy by not explaining how their system work and then they wonder why nobody likes it?
    The purpose of a wastegate on a diesel is to control turbo speed not boost pressure. Thats not to say it doesnt effect final boost pressure, it does, but thats not why its fitted.
    The reason an Acert runs so much more boost is to get the engine to burn leaner and cooler, the higher volume of air (compressed) in the cylinder the more molecules there are to absorb the heat energy, ie the same amount of heat energy in the cylinder and therefore same power but each individual molecule is at a lower temp because there is more of them, this lowers NOX, at the same time if you (for example) double the boost pressure and therefore double the amount of oxygen molecules in the cylinder you have more oxygen molecules surrounding each fuel molecule and a much better chance of lowering soot levels. Remember the whole purpose of Acert is to improve emission, not power or fuel ecomony...or drivability for that matter.
    The emissions must be improved over the whole rev range so the Acert turbos/cam/compresion is maximised to provide a clean burn at low speed/load operation (thats why the high pressure turbo is ball bearing, so it comes on boost quick) as a result at high RPM and load they need to bleed off some boost to stop combustion pressures getting too high causing head gasket failures, its high pressure in the cylinder that pushes head gaskets and wreck rod bearings after all. With your 6NZ C15 you have 32PSI and 16.5:1 compression you have 528PSI at TDC before you fire the injector, with you 52PSI 18:1 Acert you have 963PSI at the same point. eventually you get to a point where the engine cant take any more pressure, thats why they have to bleed some off.
  2. Coal Bucket

    Coal Bucket Light Load Member

    Nov 15, 2008
    Charm City
    Lets start a discussion... Anyone besides me notice how good you accert runs after warm up but not fully at operating temp? Ever wonder why? Engine oil runs from the filter base up an oil rail int the rocker box untill it reaches a divirter valve... The dirverter valve bleeds oil pressure off into the head until the ecm sees that the oil is at a certin temp, at that desired temp oil then flows to the iva's and begin operating...Sooo ntil you reach that desired oil temp for some reason there is a little more power... hhhmmmm... Now it doesnt take long for engine to reach this temp, so there is a small window to notice the power increase... This also applys to those guys with those random stumbleing/missing problems that go away at operating temp.... hhhmmm.... would the loss of compression on 1 or 2 holes cause that stumble or would an increase of air flow cause that? I also wonder why accert air compressors ( wich are desinged for high pressure ) would need a box with a reed valve in it before that air reaches it?? could that be to protect them extremely high pressures or the loss of pressure when the cylinder gets filled with extra air?? How many accert owners have had to replace their air compressor unloaders ,only to find that when they removed them the valve would be completely caked in soot and carbon? My 6nz doesnt have that problem or that box with reed valve... Why do accerts have an injector with two cycles, pre fire, then the shot?? Are the conditions inside the cylinder that bad that they need that?? By the way how does that carbon end up on the intake side of the head anyway?? Lets compare to an EGR ISX, instead of stagged turbos they have one with a slideing vane that takes the place of two.. Kindda similar, then the isx has an egr valve on the side of the engine, the cat well, doesnt.. So how did cat reduce emissions without an egr valve on the exahaust manifold?? Could it be on the inside somwhere?? I think I might start making wires to read only cold oil temps.... Besides the fact that they will run fine if not a little better with the iva's backed all the way off........... But what the $## do I know anyway?? I'm just an idiot with a laptop that likes to think outside that little yellow box... Would like to hear yall's thoughts... see ya:biggrin_2556:
    Last edited: May 19, 2010
    EverLuc Thanks this.
  3. Coal Bucket

    Coal Bucket Light Load Member

    Nov 15, 2008
    Charm City
    just got done posting and saw the last to replys... I tend to side with jas on this... By the way my last post is not ment to be anything, but just want to hear what people are thinking... I think people tend to over think the vva thing... just my opinion.... No matter what I'd still rather have yellow than grey...
    Last edited: May 19, 2010
  4. dieselroarmt875b

    dieselroarmt875b Medium Load Member

    Aug 26, 2008

    Attached Files:

    BigSam Thanks this.
  5. Coal Bucket

    Coal Bucket Light Load Member

    Nov 15, 2008
    Charm City
    Great post! thanks..
    gonzo01 Thanks this.

    RALLYTONY555 Light Load Member

    Sep 17, 2008
    Sydney, Australia
    Tony, Sorry to hear you had some bad luck at Targa.[/QUOTE]

    Thanks Jas,
    The certre diff in the gearbox failed. The way the brakes work means that the rears work better with light application and the centre diff stops them locking by "joining" the front and rear drive together.

    On the startline of the stage before I was a bit harsh on the take off and the rears broke traction and the front didn't.
    That must have been the final straw for the diff.

    On the next stage at the end of a long straight, I touched the brakes and it was like pulling on the handbrake. I was going way too fast and committed to the next corner to do any thing but let it spin around.

    We left the road at 211kph went through a fence which "tripped" the car up and then hit the strainer wire on the telegraph pole upside down and backwards.
    Snapped the post off and flipped and spun some more.

    Was a big hit, by Julia and I where OK.

    The car isn't that bad considering

    Any way back to making the truck better, hey!

  7. blackpipes

    blackpipes Light Load Member

    May 4, 2010
    king ferry,ny
    my theory on these vva's which is only opinion so take as that. i think that the vva holds the intake valve open so that some fresh air can be blown straight thru and out the exhaust 4 a split second. this sort of dilutes the exhaust making the emissions seem lower. the xtra turbo is needed cus of this waste of manifold pressure. i think thats how cat tricked their way thru the regs until now without any egr or etc. i think that the newest laws were more than this system could fool so cat said see ya. just my opinion tho.
  8. Jas

    Jas Medium Load Member

    Glad to hear you're both ok, the car looked pretty bad in the photo I saw.

    I'm not much help fixing your car but let me know how much power you want your truck to have and we'll get started, lol:biggrin_255:.
  9. mr. slippery

    mr. slippery Bobtail Member

    Sep 22, 2009
    We also had an 07 Peterbilt with a C-15, we put on a twist flow muffler and increased mileage by .20mpg. You are correct about running the overhead. We had been told by a well respected Caterpillar dealer if your getting good fuel mileage don't touch the overhead and if your mileage drops start with the overhead. Hope this helps :yes2557: ... Shift+R improves the quality of this image. CTRL+F5 reloads the whole page. mr. slippery
  10. russtrucker

    russtrucker Road Train Member

    Mar 27, 2012
    Central PA
    My mbn is 5.7 mpg. Have eaton 3.70 on it. Stock muffler, mbn camshaft, and mbn filles kills more mpg. Want to put free flow and bully dog manifold.
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