This is my first attempt at actually contributing to this site
A brief write up on the difference between early(70-74) and late(75-76) style exhaust systems, with many pictures for you visual learners.
We'll start the Heater Box
Arranged top to bottom.
e1.7
e2.0
L2.0 all passenger sides
Click to view attachment
Note the separate collector for the later style.
Also note the bend in the 1.7 differentiating it from the e2.0
Click to view attachment

Now to show the ID of the tubing, Keep in mind these are all used and are not perfectly true(margin of error), but you can still see a notable difference between the Stainless steel early style and the later ID
e1.7
Click to view attachment
e2.0
Click to view attachment
L2.0
Click to view attachment
Muffler mount flanges.
e1.7
Click to view attachment
e2.0
Click to view attachment
L2.0
Click to view attachment

Air guide hardware, S and J-tubes on the left for Early style and the one Piece for the Later styleClick to view attachment
As mounted with Flapper boxes in place.
Click to view attachment

Muffler hangers, picture courtesy of Rhodyguy
Click to view attachment
And the Thread it came from.

Various pictures of the Bursch Mufflers for the L2.0 and e1.7 on bottom.
Click to view attachment
Click to view attachment
Click to view attachment

Mufflers are near identical differing only by the collector arrangement for obvious reasons, one a 2-1 and the other a 4-2-1. Also note the jumper pipe in the L2.0 for deleting the Cat.
Click to view attachment

And lastly the late Stock muffler with Cat in place and O2 sensor of some kind.

Well, that's all I've got. I hope that will help someone someday. If you've got a picture of the OME e1.7 and/or e2.0 Banana muffler post it.
Thanks
Samson

Very cool! Thanks for taking the time!

I think the 'O2 sensor' is the EGR bung.

Yup... Gotta be. No O2 sensor on a 914 from factory.

I knew it wasn't an O2 sensor but I couldn't think what else it would be, thus the "of some kind"

Wow, thanks for show us that. I would have never learned that else where. I have read a few books on 914s, and not one of them mentioned any of that.

This is very helpful. Thanks for your effort.

re. Bursch, are there diiferent versions to suit the various early engine sizes. ie. 1.7, 1.8 and 2.0?

yes.

one for 1.7L/1.8L motors and one for the 2.0L motors ...
Andy

instant classic thread!!!

the top hanger in post #14 is for the late (75-76) hes. the one for earlier version 2.0 hes are narrower (distance from bolt hole to bolt hole). i posted a picture of all 3 versions and the repsective b.h. measurements about 2 years ago.

k

Nice guess, but wrong. The EGR line bolts to the rectangular plate just to the right of the bung in question. That bung (with the device screwed into it) is an exhaust temp warning unit. There's a light on the dash, IIRC, that illuminates when the cat gets too hot. The Cap'n

Thanks Rhodyguy, I just edited #14 to include your picture.
Samson

I say "I vote: CLASSIC" !!!!

to add to this. after communicating barber dave, there seems to be a varience concerning the 1.7/1.8 mufflers. as dave relayed to me, the early, early 1.7 bursch mufflers are configured for the rear valance with the hole as opposed to the valances with the notch.

k

2007 thread bump to 2018!

Does anyone know of any HP differences between early 2.0 and late 2.0 exhaust/exchangers?

Yeah, about 7 HP. The 73-74 2.0 was rated at 95 HP DIN, while the 75-76 was rated at 88 HP DIN.

--DD

7-ish HP is significant. Did later 75-76 models have catalytic converters? I am thinking they no longer ran the 'hot dog' muffler as early models?

Some of the 75-76 cars had cats; most did not. I think it was CA and MA only that had them. Most states used a bypass pipe in place of the cat, but the muffler was still the two-piece thing.

See post #7 in this thread for a photo of the stock 75-76 muffler--in that case, with a cat.

--DD

Thanks for the response. That later muffler doesn't look very good. I wonder what percentage of the 7hp loss was the new muffler vs the new manifolds?

Most of it is the header pipes and single pipe heat exchangers. They are not designed for flow, just a way to route exhaust from 2 cylinders in to one pipe in the heat exchanger.
I have installed aftermarket mufflers (bursh) on 75/76 cars and it makes very little difference.
Backdating to a 73/74 style 2.0 exhaust does make a difference.

Jim

Is the shape of the pipe the same where it goes into the head? ... or are some oval and others round?

They're all oval. They sometimes get called "round" because there are later Buses with ports that are pretty rectangular shaped. Those get called "square port" heads.

But all of the 914 exhaust ports are the same basic shape. You can fit any-year 914 exhaust onto any-year 914 head.

--DD

That makes sense, thank you for the comparison information