So I've been reading up on the FWD Monte exhaust systems, learned about the u-bend, and started wondering if each and every Monte since 1995 got stuck with one, no matter which engine they have. It's not just a 3800 "thing", is it? And if that's true, then do all W-bodies (Montes, Luminas, Impalas, Grand Prixs, Regals, etc.) have it in their downpipes too?

 

I'm almost certain every 3800 powered vehicle has it, not sure about the other engines though

 

I know gen 2 W-bodies (like the '97-'03 Grand Prix, '00-'05 Impala and '00-'05 Monte) has the U-Bend regardless of 3800/3100/3400 engines. I'd imagine the rest of the 2nd gen W-bodies would be the same.

If I recall, the H-bodies, like the Bonneville, do not have the U-bend.

 

Well, out of curiosity I looked under the hood and behind the engine of my Z34, and discovered that on the LQ1 at least, the oxygen sensor plugs in right on top of the rear-bank exhaust manifold, just before the junction to the downpipe... and the downpipe just seems to be a plain and simple one with no significant kinks in it.

So on the W-body cars, the u-bend is done to (inelegantly) accommodate an oxygen sensor, which is placed before the catcon. I'm thinking the industry-wide switch to OBD-II beginning with the 1996 model year has to do with the relocated O2 sensor, and thus the '95s might be the only-year Montes to avoid being stuck with it.

So, to answer my own question: no, not every W-body car has a u-bend!

 

You are probably right, the switch to ODBII had a lot to do with the addition of another O2 sensor. Such as I know my 94 Grand Am with a 3100 had a single O2 sensor on the rear manifold, much like you described with the LQ1 you have.

Just for the record, GM never relocated the O2 sensor, they added an additional one. They kept the one on the rear exhaust manifold (just like your LQ1, this has to do with fueling). They added the second one after the cat (not before), and on some cars (like the Monte) it was to monitor the "health" of the cat.

Good to know you escaped the U-bend issue

 

Thanks for the clarification, T.M.; the second O2 after the catcon makes more sense. I admit not knowing exactly how it was all set up; downpipes are kinda hard to see when peeking underneath a parked car.

 

Finally took some pictures under my Z34 for some photographic proof and further clarification.

It's all factory-stock, and actually doesn't look like such a lame setup, with fairly thick piping, smooth (but not quite mandrel-bent smooth) bends, and a properly-shaped Y-split for the dual mufflers. I even like the black-painted slant-cut quad tailpipes the Z34s have. So I doubt that I'll ever do any exhaust mods on this car, aside from a direct-replacement high-flow catcon if/when the stock one clogs up.


^Here's the downpipe... lots of room there.


^There are a couple of mild bends before and after the catcon, apparently done to raise it up an inch or so, giving it the same level of ground clearance as the rest of the exhaust piping.


^And here's where the U-bend and the resonator go on later-model Montes (and other W-bodies). Still, I'm not sure if the '96s and '97s are just like this, or if they're more like the '98-up models.
There is a resonator on the '95, where the pipe goes along the passenger side.

 

Some of the early 5th Gens maybe different that the later ones. For example I liberated a seat from the Rear of a 95 Monte and it didn't attach the same way that my 99 does. Then I recently found some seat from a 98 that were the same as mine I got the front and the back because they were fairly reasonable. I am certain that improvements were made on these cars, and the later ones benefitted from that.
As I recall the Brick Yard Monte was release in 1994. I think NASCAR didn't approve the release of teams using the new style until 1995.