4" exhaust.

[duramax on fire]

I've shearched all night. Still need answers. Seams like the mbrp is the best fit. But jegs is ok also.

Will the 4" help cool the motor down and maybe get better mpg. Not having problems but fan engages on highway pulling load and stays engaged.

Will exhaust alone give me more power. Stock truck right now. Not ready to do a tranny build. I've read even a small tune is hard on the torque converter

Got 10.7 mpg hand calc. Pulling 6k trailer running 68ish

 

[TROJAN366]

What year is the truck?

 

[duramax on fire]

2003 sorry. Lb7

 

[JoshH]

I prefer Flo~Pro brand exhaust kits. An exhaust will help exhaust temps a little, but that won't do much to keep your coolant temps down. Assuming your location is Dallas, TX, that's just how it is towing in the summer here. It may help your fuel mileage a little too, but if you want better mileage, you need to get it tuned. That's where you'll see your biggest improvement.

 

[TROJAN366]

What about a boost increase valve and a ported intake horn? Might help things out a bit.

 

[yellowchevy]

I'd lean towards a ported/polished turbo but thats my thing!! haha

Flo-pro or Magnaflow are good fitting systems so I'd lean towards either of them.
Ported/polished intake horn or aftermarket intake horn will help throttle response. PPE boost valve or just putting an air regulator between the cover & wastegate to adjust how much the wastegate see's will help.

If you're wanting some local guidance or someone to look at it go see JoshH, hell of a nice guy and very knowledge able!!:thumb:

Yellowchevy

 

[duramax on fire]

Ok thanks for all the advise. It was 101 while towing. Couldn't run AC last month because it would overheat. Bad fan clutch.

So does a small tune hurt the trans or not

 

[bmc1025]

A small tune will greatly effect drivability, in a good way.

 

[DaJokr]

Tuning may do more damage over time, but it will all depend on how big you go and how hard you are on it. A small tune (50-60hp) and a light foot you shouldn't have any issues. Start wearing lead boots though...

 

[TheBac]

Wait a sec -- an LB7 with a fan that comes on while towing on the highway? Thats not too common.

Id be checking the fan clutch and cleaning the cooling stack out first.

 

[WolfLMM]

^ Yes!!! Lb7s are cold blooded as hell. Even here in the heat of the Deep South, my truck rarely ever gets over 182 degrees. Fan hasn't been on in years.

 

[duramax on fire]

Fan clutch is new. Washed out the AC condensor. Pulled radiator and washed it when head gaskets were done. With bad clutch motor got up to 230 running ac

 

[OregonDMAX]

So after all that how hot does it get.
I've never seen over 200 before even on the 110+ degree days. Now that not Towing but still stop and go traffic with no airflow.
As stated lb7's are cold blooded if operating properly.

 

[duramax on fire]

Stays cool. Runs up to 195-200. The. Fan engages and pulls it down to 180.

 

[duramax on fire]

http://www.duramaxdiesels.com/forum/showthread.php?t=65135


Also this engine has some scoring in one cylinder. I don't think that would cause any heating issues. But so far cylinder holding up well. Still 400lbs.

I just wasnt sure if the fan clutch running all the time was normal. JoshH says it was though and he's knowledgeable on these motors.

First dmax. Still learning.

 

[WolfLMM]

It's normal for lly-lml. Lb7s run a lot cooler. What are you towing? And is it stop and go or highway?

 

[duramax on fire]

It's normal for lly-lml. Lb7s run a lot cooler. What are you towing? And is it stop and go or highway?

25' camper. Probably 7 loaded down maybe. Running down highway is when it would heat up on me before I did the fan clutch. Stop and it would cool right back down. Any thing over 60 and fan runs more but stays cool. There is a guard on the front.

 

[duramax on fire]

Before fan clutch

 

[duramax on fire]

After running 65. Both loaded

 

[duramax on fire]

Grill guard mesh