exhaust question

I have an 1835cc with dual Dellorto 44 carbs. I have an EMPI header a with dual mufflers. One of the mufflers is coming apart, could I junk them both and go with a single muffler, or would that be too much back pressure? Thanks for any info

I'm not sure back pressure is at issue. It seems to me that as long as the engine is able to breathe, or rather fully exhale, you're okay. There are professional opinions here which may differ from my shade-tree perspective, and you should certainly listen to them, but as long as the pipes enter the collector in firing order, you'll probably be A-okay.

In my view, there needs to be enough pipe diameter before the collector for all that gas to exit the cylinders AND enough baffling to keep the noise to a civilized level as the gas exits the system.

Consequently, you'll see an amazing variety of pipes under these cars, each with its own turns and twists. It sounds to me like you have a couple 'quiet-type' Beetle mufflers, both of which should be replaced at the same time.

If you're looking to upgrade, you could certainly do that by taking your car to a muffler shop and exploring your options. Volume, both in the mathematical and auditory senses, will be a key point in that exploratory process.

If you just want to replace the tweety pipes you have, you're in luck. They're petty much free: they were not made to last more than a couple years under normal driving conditions, and can be found anywhere that sells EMPI or BugPack products.

Good luck!

"Tweety pipes" Cory, you sure have a great way with words. Love it!

44's with 1835 cc?

Jack, 44 IDF's will work just fine on even a stock 1600 cc engine. All that's necessary is to jet them correctly.

Bob, In regard to your 1835cc engine. It's basically a stock engine with stock stroke but the piston diameter has been increased from 85.5mm's to 92mm's Breathing isn't an issue.. You actually NEED some back pressure.

Replacing the mufflers may be tricky because they're not readily available but it can be done.

My advice is to either do a search on this site for exhaust systems or, ask the question on this board (paying close attention to those that have a 1915cc engine or less) and get a consensus of their opinions regarding the exhaust system they are currently using.

I had a 1776 in my speedy with dual 44 webers and a single quiet muffler, ran excellent, great combination . Mike McCarthy

A nice loud exhaust will drown out all that silly "plint-ketty-planking" going on in the engine compartment. OK, so maybe music is in the ear of the be-holder.

Yeah, 44s can be made to work on an 1835, 1776, 1600, or most anything else you want to bolt 'em on- but why would you? A 44 mm IDF has 36 mm venturis stock- unless your intake runners are at least 36 mm, the vents are no longer the "choke point". Tuning becomes a real compromise.

44 mm carbs, feeding an 1835, and exhaling through a 1-3/8" EMPI header (and probably heater boxes) is a mismatch. It might be made to run "OK", but with enough tuning you could probably get IDAs to run sevicably as well.

That doesn't make it optimal.

This vw Trends article found thier 1600cc motor ran better with the single muffler than it did with duals. Now,, you are flowing a bit higher volumes,,, soooo,, it is hard to say if there will be any noticable difference between the two muffler options. I am guessing that the single muffler would be marginally better at low-medium rpms,, and the dual mufflers better at the top of the range. But give it a read for yourself. Alan

http://www.vwtrendsweb.com/tech/0109vwt_volkswagen_exhaust_test/index.html

I've read on here from time to time that "back pressure doesn't matter on these engines".

BS

On these engines, back pressure really matters. A bunch of us learned that in the 1960's dune buggy days (like......tear off your exhaust system on something sticking up out of the ground and the engine runs like shit) and nothing has changed. Yes, a single often gives more torque on the mid-to-low end and duals might give more torque on the high end, but there is so much more to consider.......the length, diameter and bends of the exhaust tubes, the size and directivity of the muffler baffles, the air flow through the carbs and heads, the cam/valve timing, the overall combustion ratio - a whole bunch of stuff that good engine builders deal with daily and many of us don't even consider.

If you had duals and got a feel for the performance and then switched to a single (or vice versa) you WILL feel a difference. Will that difference be good or bad? Dunno. It all depends............How do you drive? Where, in the rpm range, do you shift? 3K? 4k? Higher? Lower? see.....All that stuff (how you drive) makes a big difference in answering the 'simple' question, "Will this make a difference???"

OH, and btw.......I seldom pay a lot of attention to "horsepower". Useable torque is everything.

The reason your engine ran like shit when you tore the header off is not because of less backpressure. It's because you've changed the tuned length for peak torque of the exhaust from, say, 5000 to 45000 RPM. Go stick a banana in your tailpipe and you'll see how useful high backpressure is to your engine.

The reason you might want smaller diameter primaries in your exhaust is because it increases exhaust velocity which promotes scavenging and cylinder filling. But that has to be balanced with the need for larger diameters for greater total flow capacity. Too small and you'll have good torque but the engine will choke at higher revs. Too large and the bottom end torque is low but you'll be able to rev the engine higher for more HP.