Exhaust & Intake on LLY

[Rich45]

Hi I'm new to the forums. I was wondering if it was worth it to put a cat back exhaust system and a cold air intake on my 2005 LLY. Is there much of a performance, towing and MPG gain without using a tuner. Thanks

[Freightliner3]

I have 2005 LLY also.I have changed the driver side exhaust manifold.Added a Banks ram air and monster cat back exhaust.I did notice an increase in power when pulling heavy loads.But no real change in fuel economy.
Then I bought the Sun Coast 6spd upgrade for the Allison.That made a measureable increase in fuel economy and a nice quiet daily ride.
If I were to do it over again? I would change driver side exhaust manifold and install the 6spd. upgrade.I have also changed all fluids to Amsoil Syn.which I would recommend.Good Luck!

[Kennedy]

I would put more stock in a full exhaust system. The intake will not give great gains. I have a mod that I do to the OE air box on my site under Tech Tips. I wouldn't bother with a cat back exhaust.

[killerbee]

Hi I'm new to the forums. I was wondering if it was worth it to put a cat back exhaust system and a cold air intake on my 2005 LLY. Is there much of a performance, towing and MPG gain without using a tuner. Thanks

Yes, for towing, a good CAI makes a significant difference in any scenario where the fan comes on frequently. Now see if you can find one that works to keep air temp under control. That is the problem. With IAT's exceeding 220 on the LLY, air density is easily decreased 20%, and turbo efficiency flies right into the toilet, leading also to high EGT.

[Mark Rinker]

...especially if you live in Arizona.

Not so much in Minnesota. We have alot more cooler air to burn, and lower pavement temps yearround.