550 hp 3406e VS 550 C-15

I agree the most of the twin turbo Cats are hard on fuel but I have customers with some that get a consistant 5.5 to 6.5 us mpg loaded. I am downloading the ones that are running well and going to do some testing to see whats different. I have some twin turbos getting 3.8 to 4.1 us mpg loaded that I am working on a fix.

 

Hey DDS I am taking mine to the shop Monday for for a weak CAT break problem and I am thinking about having them to put it on the dyno just to see what its doing power wise.....Mine is in the 4.8 to 5 mpg range....Would you take a look at the read out and see what if anything needs to be done to it? Its a MXS.

 

Your weak Cat brake problem may be a broken hold down bolt. Let the dealer do a full par dyno and get a report. Let them do an adjustment to top of spec. They will do this if it is a 475, they will not take a 550hp more than nominal fuel flow. Scan the before and after report and send it. When the truck is out of warranty, or before if you use another ecm, a flash to a 625 hp works very well.

 

I had an '05 MXS come in with complaints of a weak CAT brake.All that needed was an ecm reflash.

 

How does the ECM control the Cat brake? I understand that the ECM see's every thing going on with the motor but I dont understand why a reflash could fix that. Mine still works in all 3 stages but its had gotten weak and it dont "sound" as chrisp and sharp as before. It use to have about 22 to 25 pounds of turbo boost at 1500rpm when on now it has around 15 to 18 pounds. I m not the type to use it every time I stop, I use it for what it was ment to be use for...going down hills and when it was working right it was a #### good now its reminds me of a Jake brake on a old 3406 Cat...more noise than brake.

 

Is it down on power/boost also? if the boost is down under power also it could be a mechaincal problem, maybe wastegate, turbo damage or Cat brake lash problem, blocked intake or exhaust will give the same symptoms.
If there is no loss of boost under power it could be lack of oil pressure to the cat break, they break mounting studs and then the housing cracks causing a loss of oil pressure, a spun cam bearing can also cause this with no other faults (the VVAs get oil pressure from the rail on the RHS of the engine but the cat brake gets it oil from the cam the same as a traditional C-15). you cant buy any separate parts for the cat brakes, makes it way too expensive if something is wrong with them.

 

Got the Cat brake fixed...It was a broken hold down bolt AND a broken rocker arm shaft. I had the overhead ran last month in Denver and told them to check out the weak Jake then. Said the Jake was fine. Now that I had the time to get it to the Cat shop here at home they found it after doing a cutout test. Number 5 cyl was a little funkie and thats were the problem was. So much for the shop in Denver!!

 

Remember, Cummins and Detroit rate engine hp at the rear of the engine, CAT rates on the ground.

 

How do figure that? A stock 550 Cat will have 550 at the flywheel or close to that.I know when I had my 02 engine dyno'd at Cat, it had 553 corrected HP at the flywheel

 

Cat rates theirs to the flywheel, Mack is the one who rates HP to the wheels.