I'm running the 4" from SS diesel right now no CAT, and couldn't be happier with it. However I heard that 3" exhaust is fine until you start making 400hp + then you need to go to the 4" exhaust system. Is there any differents in performance from 3" to 4"? I see alot of people here are running the 3", 3.5", and 4". I would guess that EGT would be lower with the bigger pipe but don't know for sure. BTW installing gauges this weekend:ro) boost, EGT, and trans. So you know i'll be looking to make more power soon;)

IMO, you can not go too large with the exhaust on a turbo charged engine. There is no benefit to having back pressure post turbo.

Pardon me, MDT, but where did you acquire your 4" stainless exhaust? How much was it, may I ask?

Sincerely,

Rob :)

$290 + $60 shipping. Pinnacle on ebay. Not a direct fit for a Tahoe, but worth the effort.

Hi MDT,

Can you give us a link? I can't find anything under "Pinnacle exhaust" on EBay.

Sincerely,

Rob :)

Very Good Question '94 ! ! ! ! ! I was just about to ask CR the same thing under that other thread '....Louder TD'. Looking forward to seeing what comes of this post.

Thanks.
-391

A cast off Ford PS exhaust works well for donor 4" stainless pipe, many muffler shops have them in the trash when a PS guy upgrades to 5" pipe.

I'll post the 800 number for Pinnacle in this thread when I get home from work.

One reason i asked is if useing a true 3" down pipe, why not use 3" all the way out? I don't know if it's the same but if you run water into a 1/2" line then into a 1" line, you really don't gain much since the 1" line will only flow what is provided by the 1/2" line. I know the sound would be different between the 3" and 4" right?, but really just wounding about the performance. Forgive me it may be different with exhaust, that's why I'm asking. Either way I'm not giving up my 4".

One reason i asked is if useing a true 3" down pipe, why not use 3" all the way out? I don't know if it's the same but if you run water into a 1/2" line then into a 1" line, you really don't gain much since the 1" line will only flow what is provided by the 1/2" line. I know the sound would be different between the 3" and 4" right?, but really just wounding about the performance. Forgive me it may be different with exhaust, that's why I'm asking. Either way I'm not giving up my 4".

Your not including friction loss in you analogy. 200' of 1/2" line would flow considerably less water at a given pressure than 10' if 1/2" line would due to friction losses in the line itself. So if you had 10' of 1/2 inch line and then 190' of 3/4" line, you could expect much greater flow than if you just used 1/2" all the way out.

Tim

Ok, so then going to 4" after the 3" down pipe "could" result in more performance?

94Blazer6.5, can you give some more details on your SS 4" exhaust? For example,

1) did you do the install yourself, and was it hard - did you have to modify it much?
2) What differences did you note? Measurements? Sounds? Power? Torque? I have a '95 Tahoe (same as your Blazer) and am considering buying Walt's exhaust.
3) Also, who did the '97 cooling upgrade, and have you seen a significant drop in temps?

Thanks,

Rob :)

Ok, so then going to 4" after the 3" down pipe "could" result in more performance?

Theoretically, yes. But only if the 3 inch system restricts flow enough to create backpressure in the system. Theres those pesky friction losses again.

If the 3" flow enough to meet engine demand, then the 4" would not have much benefit.

Personally, I think 3" pipes are a touch small. 3.5" is more like it, and 4" is overkill

Tim

Guess i'm killing it then....lol

I'm killing it too.. and it feels GOOD! :ro):ro)

Turbo Tahoe
1. I did install the down pipe, the 1st section, muffler myself - very easy, but then ran into some trouble. Since the fuel tank is in the rear the 4" wouldn't fit between the shock and tank (really to close to the tank IMO) so I cut the 90* elbow from the tail pipe and dumped it in front of the back axel. I then took it a muffler shop to weld the brackets up for me (my ****** welder wouldn't work) they charged me like 10 or 15 bucks to do it.Will it pass inseption? I'll find out this saturday and let you know. Sounds great!!!!!! Loud during take off, but once you start cruising it mellows out and not that loud inside the truck or least my wife and kids still fall asleep on road trips.
2. Don't know about power or torque i have no way to measure that sorry. However it's cool to say I got 4" pipes.
3.Cooling upgrade agian did it myself. Note that I think you will need to grind some on the Alt bracket so the cross-over will fit like i had to. A 4" grinder works OK but big and hard to hold (i left the bracket on the truck, removing it should make it easier) A dermal tool works GREAT. other than that no different than replacing the water pump, and clutch fan. Water temp stays at about 180* in stop and traffice, i don't pull heavy loads maybe 5,000 to 6,000 lbs tops far and few (about 2,000-2,500lbs most the time) in between temp never rose above 180* going though the Texas Hill Country. I'm very happy with what i got form Walt @ SS diesel.