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What size exhaust are you guys running for some of these high horsepower builds? I know that bigger is better for post-turbo piping; especially for diesels. It seems quite tough to fit large size tubing underneath the 126 chassis. Currently at 3” and looking to go up to 4” or maybe 3.5 if 4 is totally not possible. 

The large canister shaped straight through mufflers I have in the driveshaft tunnel are 6” in diameter but they are quite close to the driveshaft and still hang below the body line and would be the first thing to touch down should I bottom out. A 4” piece of straight pipe would definitely fit in the tunnel and actually gain some ground clearance but also some decibels deleting the two mid-section mufflers and going larger diameter. I think the two most critical areas I am concerned with fitting the 4” pipe is right after downpipe going under car before it enters the tunnel and getting past the rear diff and axles.
(02-09-2020, 11:29 PM)TwoMuchBoost Wrote: [ -> ]What size exhaust are you guys running for some of these high horsepower builds? I know that bigger is better for post-turbo piping; especially for diesels. It seems quite tough to fit large size tubing underneath the 126 chassis. Currently at 3” and looking to go up to 4” or maybe 3.5 if 4 is totally not possible. 

The large canister shaped straight through mufflers I have in the driveshaft tunnel are 6” in diameter but they are quite close to the driveshaft and still hang below the body line and would be the first thing to touch down should I bottom out. A 4” piece of straight pipe would definitely fit in the tunnel and actually gain some ground clearance but also some decibels deleting the two mid-section mufflers and going larger diameter. I think the two most critical areas I am concerned with fitting the 4” pipe is right after downpipe going under car before it enters the tunnel and getting past the rear diff and axles.

3" should be more then adequate for 183 C.I.    Om 606.
In reality, cubic inches or displacement has nothing at all to do with exhaust sizing...only horsepower/flow matters and I want 500 roughly. An 8 liter engine only turning 3000RPM is the same as our engine turning 5,500 and under more boost. RPM, boost level, and horsepower goals are all factors and diesels need larger than their gasoline counterparts. 3 inches is NOT sufficient; at all. Maybe for the average bear sure, but no 30+psi tune is going to like a 3” pipe to breath through.
(02-12-2020, 08:23 AM)TwoMuchBoost Wrote: [ -> ]In reality, cubic inches or displacement has nothing at all to do with exhaust sizing...only horsepower/flow matters and I want 500 roughly. An 8 liter engine only turning 3000RPM is the same as our engine turning 5,500 and under more boost. RPM, boost level, and horsepower goals are all factors and diesels need larger than their gasoline counterparts. 3 inches is NOT sufficient; at all. Maybe for the average bear sure, but no 30+psi tune is going to like a 3” pipe to breath through.

You seemed to answer your own question.
I know right... lol. I guess the predicament is I know what I *want* to do exhaust wise... just not if it's possible or if it's realistic for this chassis. I was hoping someone would have a 4" exhaust fitted for one of these 600ish HP builds but most of those I've seen (like the DPUK wagon) all have a hood stack so...

For what it's worth, I've ordered 4" V-bands and about to order 4" piping and mandrel bends. I'm going to *make it work* at this point so I'll report back with how badly I have to mangle this w126 to get 4 inches under the tunnel.
I don't think (or am not aware of) anyone using bigger than 3-3.5" exhaust on their STD builds. Definitely nobody with 4" on a car... can't see how its an issue
Check ERX's build in the projects section. He claims that going from 3 to 4 inch exhaust helped him gain power. I plan on running a full 4 inch on my build.
(02-12-2020, 07:30 PM)NZScott Wrote: [ -> ]I don't think (or am not aware of) anyone using bigger than 3-3.5" exhaust on their STD builds. Definitely nobody with 4" on a car... can't see how its an issue

Again I agree, I think the muffler would be more of the issue then going to a 4" exhaust.