More Horse Power

[rmstg2]

Would it be possible to get a stock 2005 LLY to 400 horsepower without using a tuner. How much is there to be gained in the 4" exhaust option?

Bob H.

[thee craig]

ha. without a tuner? ur truck wont even know until you tell it. a couple at best, but for what your looking for.... little to none.

[Maine Towing]

These trucks are 100% controlled by the computer, the volume of fuel, timing, etc. Change the computer program, with a tuner or EFI Live and you can get there. The 4" exhaust will allow your engine to breathe easier thus more of the HP produced will be transferred to the rear wheels and not to pushing the exhaust gasses out the tail pipe, but in all honesty it is not something you will notice behind the wheel, you probably will see an increase in MPG however.

[labmouselb7]

probably can get closer to 400 HP with tuning alone and with stock exhaust and intake. exhaust will make the exhaust temps safer when running a high horsepower tune but not make the HP for You.

[rmstg2]

Thanks for the replies. A tuner it is, recommendations? I have a friend with a 2011 Ford diesel that feels a little stronger than my Chevy. I haven't told him that though. Would a 4" exhaust be efficient or would a 5" be better. I'm not looking for exhaust noise but would like to hear the turbo.Thanks again

Bob H.

[DuramaxxedLBZ]

A 5" really isn't necessary until you're pushing a considerable amount of more air, but a lot of people go with it for the lower sound, myself included. If you're wanting good turbo noise, go for a ProFab downpipe (pain to install) and any downpipe back system. On my 06 I had a 4" catless system with a muffler (mbrp's muffler is a glorified glass-pack, eliminates most drone) and it had good sound under WOT and was hardly noticeable in the cab at cruising speed.

[Maine Towing]

Agreed, a 5" would not gain you anything at the HP you are looking at. Few things to consider, you are trying to push 90 HP more into your transmission, I know the 6 speed is just about maxed out there, not sure on the 5 speed but you may want to look into that. You really want to consider a lift pump to protect your CP3 and keep from throwing P0087 codes. Lastly more fuel = more HP = more heat, the LLY has an issue with heat so you want to take that into consideration, perhaps an add on cooler, air scoops to get ambient air into the engine compartment? EFI Live is a bit pricy but with a good tune will give you the most for your $$ and lots of flexibility to get the most out of your truck.

[RickDLance]

Back in the early days a stock LLY in Texas did a before and after dyno test on my up pipes and picked up over 20 hp. The thread is here somewhere.

[rmstg2]

Thanks again for the replies fellows. I think I will go with 4" all the way. What gains are there blocking the egr and is it something a novice can do.
Since I changed the mouthpiece the truck does run cooler under a load but that is with stock settings. What is the $1.29 airbox mod?

Bob H.

[Maine Towing]

The EGR block is simple, 2 nuts, 12 mm to remove and slide the plate in place with the gasket on the up pipe side. Only hard parrt is that the nuts are factory torqued to 16.2 billion ft-lbs and are partially blocked by the firewall, so you will loose some skin in the process but that is all. If you block it then you will get a check engine light if you don't turn off the code with a tuner or EFI live, the code won't hurt anything but your check engine light will be on most likely. The $1.29 was the "All on headlight mod" which keeps my low beams and fog lights on when I turn on the high beams. Since you have the LBZ mouthpiece I am assuming you have the LBZ cylinder air cleaner? If so the mod simply involves removing the finned end on the air box which partially blocks the air flow, it will pop right out. I also enlarged the cut out in the inner fender so that more air flows directly into the filter end under pressure.