C15 Acert rebuild

oldog1984 · Feb 12, 2018

RedForeman said: ↑

So two drivers getting crappy mileage but no idea what kind of terrain, load, or aerodynamics are possibly affecting mileage. Here's what I've learned the past four years with mine.

One, get a scan gauge so you can see what's happening real time. The mpg numbers aren't going to be accurate, but they will be good for knowing what's better or worse with your driving habits.

First thing, both of mine had some kind of great big catalyst? muffler that got replaced with a high flow smaller one. They get stopped up over time. Since the replacement is a much smaller diameter, the brackets have to be modified. Biggest, easiest improvement in performance and mileage right there.

ACERTs run high boost pressure. My latest is a stock 475 NXS that will max out close to 40 psi. The 550 MXS I drive has gone upwards to 50 psi under the right circumstances. So making sure the intake system is sealed tight is even more important. Outside of a CAC pressure test someone else already mentioned, start with the simple stuff. You will probably see evidence of air leaks around the hump hoses. Alternatively you can soap them up and watch for bubbles when a helper snaps the throttle. Or just change them if you know they're old. Another (relatively) cheap and easy to do fix. A set of 4 and 8 new clamps will seal those intake tubes up.

Also look for soot around all the turbo couplers and their clamps. Also around the exhaust flange that the innermost turbo attaches to. If you see any, first try tightening the clamps/flange nuts. If the clamps are broken, or if you find broken studs on the flange, that stuff needs to be replaced and repaired.

The ACERT also likes to break #6 exhaust studs. Get a flash light and look up in there to make sure there are still two in there, then get the broken one drilled out and replaced LOL. It won't take long to notice this from the noise and exhaust fumes in the cab. Even before you hear it, power and mileage will fall off substantially with an exhaust leak upstream from the turbos.

If you take anything apart on the exhaust side, you'll have to re-torque all the clamps at least a dozen times before they quit stretching loose during a heat cycle. Best to just do it as part of your pre-trip on a cold engine every time, until they stay tight.

I just did Q4 2017 IFTA. My '07 T600 was at 5.95 mpg. I haul a reefer Atlanta to NY and back. The northbound trip is nearly always via I-77/US19/I-79 straight through the mountains with about 28k in the wagon. Coming back I'm usually maxed out close to 80k gross and run I71/271/75 via Jellico TN. I run the speed limit and never the last one up the hills. Truck has 13 spd and 3.25 rears.

My son is driving the '07 387 and it got 5.96. Most of his runs are Atlanta into eastern Virginia, sometimes into PA. Same spec as mine but stock 475 tune and 3.36 rears.

Both trucks have Tripacs and bunk heaters on them, so nearly zero idling. Low rolling resistance tires on truck and trailers. Also have skirts and tails on the trailers. Mine has just over a million miles on it, the other one 1.2 mil.

If I was running better terrain, or not chasing traffic up hill, I could easily see the IFTA numbers hitting 7+.
Click to expand...

the terrian ohio to cal tp florida up and down i77,75,65,40,20,and i10 and always heavy flatbed hauling steel.

bavarian · Feb 12, 2018

RedForeman said: ↑

So two drivers getting crappy mileage but no idea what kind of terrain, load, or aerodynamics are possibly affecting mileage. Here's what I've learned the past four years with mine.

One, get a scan gauge so you can see what's happening real time. The mpg numbers aren't going to be accurate, but they will be good for knowing what's better or worse with your driving habits.

First thing, both of mine had some kind of great big catalyst? muffler that got replaced with a high flow smaller one. They get stopped up over time. Since the replacement is a much smaller diameter, the brackets have to be modified. Biggest, easiest improvement in performance and mileage right there.

ACERTs run high boost pressure. My latest is a stock 475 NXS that will max out close to 40 psi. The 550 MXS I drive has gone upwards to 50 psi under the right circumstances. So making sure the intake system is sealed tight is even more important. Outside of a CAC pressure test someone else already mentioned, start with the simple stuff. You will probably see evidence of air leaks around the hump hoses. Alternatively you can soap them up and watch for bubbles when a helper snaps the throttle. Or just change them if you know they're old. Another (relatively) cheap and easy to do fix. A set of 4 and 8 new clamps will seal those intake tubes up.

Also look for soot around all the turbo couplers and their clamps. Also around the exhaust flange that the innermost turbo attaches to. If you see any, first try tightening the clamps/flange nuts. If the clamps are broken, or if you find broken studs on the flange, that stuff needs to be replaced and repaired.

The ACERT also likes to break #6 exhaust studs. Get a flash light and look up in there to make sure there are still two in there, then get the broken one drilled out and replaced LOL. It won't take long to notice this from the noise and exhaust fumes in the cab. Even before you hear it, power and mileage will fall off substantially with an exhaust leak upstream from the turbos.

If you take anything apart on the exhaust side, you'll have to re-torque all the clamps at least a dozen times before they quit stretching loose during a heat cycle. Best to just do it as part of your pre-trip on a cold engine every time, until they stay tight.

I just did Q4 2017 IFTA. My '07 T600 was at 5.95 mpg. I haul a reefer Atlanta to NY and back. The northbound trip is nearly always via I-77/US19/I-79 straight through the mountains with about 28k in the wagon. Coming back I'm usually maxed out close to 80k gross and run I71/271/75 via Jellico TN. I run the speed limit and never the last one up the hills. Truck has 13 spd and 3.25 rears.

My son is driving the '07 387 and it got 5.96. Most of his runs are Atlanta into eastern Virginia, sometimes into PA. Same spec as mine but stock 475 tune and 3.36 rears.

Both trucks have Tripacs and bunk heaters on them, so nearly zero idling. Low rolling resistance tires on truck and trailers. Also have skirts and tails on the trailers. Mine has just over a million miles on it, the other one 1.2 mil.

If I was running better terrain, or not chasing traffic up hill, I could easily see the IFTA numbers hitting 7+.
Click to expand...

Absolutely agree.
I put a fleetair filter in. Felt another slight improvement.

The OP should do way better if his loads are steel only. It's not the flatdeck itself that kills the fuel, It's those none aerodynamic big boxes they sometimes haul.
When was the last time the overhead was done?

The last thing I could think of are the shift points of the transmission. If the transmission shifts down above 1200 rpm, lock it in manual and lug down the engine to 1100 before dropping a gear.

bavarian · Feb 12, 2018

By the way, the OP never talked about idling.
He is in warmer climate and idling might be a factor.

Manvan · Mar 15, 2019

bigdad7 said: ↑

If you pm me I can give you a referral for my cathouse after some work and a tune my acert averages almost 7mpg last week I was 6.8 mpg
Click to expand...

Can you please share the info with me .

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